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CONFERENCE
ON
DNA PHYSICS 2017(9-11 March, 2017)
Programme and Abstracts
Department of Physics
Birla Institute of Technology & Science, Pilani
Pilani Campus, Rajasthan (India)
ADVISORS TO THE ORGANIZING TEAM
Marco Zoli, University of Camerino, ItalyGautum Menon, Institute of Mathematical Sciences, IndiaPankaj Mishra, Indian School of Mines, IndiaFlavio Seno, University of Padova, ItalyDebaprasad Giri, IIT-BHU, Varanasi, IndiaGerald Weber, Federal University of Mina Gerais, BrazilRalf Metzler, University of Potsdam, Germany
Chief PatronProf. Souvik BhattacharyyaVice-Chancellor, Birla Institute of Technology & Science, PilaniPatronProf. A.K. SarkarDirector, Birla Institute of Technology & Science, Pilani, Pilani CampusChairProf. Anshuman DalviHead, Department of PhysicsConvenerDr. Navin SinghCo-convenersDr. J.N. BandyopadhyayProf. R.K. Gupta
Local Organizing Team
Amol HolkundkarBiswanath LayekDebashis BandyopadhyayDebi Dutt PantKaushar Vaidya Kusum Lata Madhukar Mishra Manjuladevi VNiladri Sarkar R.R. MishraRakesh ChoubisaRishikesh VaidyaSindhu SSrijata DeyS.N. KarbelkarSubhashis GangopadhyayTapomay Guha Sarkar
Student’s support
AditiArghyaCaptainDinachandraIshaanNeelakshiPrachiPradeepParulRajeevRitikaShivaniSumitaTridev
Office Staff
Shrikant SharmaRajeev GaurVirendra Yadav
SPONSORS: CSIR, DST-SERB, DRDO, DST (Rajasthan)
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From Convener’s desk
It gives me immense pleasure to welcome all in the conference DNA Physics 2017. DNA is known to
be the molecule of life. It contains code of our life and is known to be one of the very complex as well
as interesting molecule. Researchers around the globe, regardless of their categorization as biologists,
microbiologists, physicists, engineers etc, are putting lot of efforts to understand the complex structure
and behaviour of this spectacular molecule. All are busy to unravel the secrets lying beneath the basis of
genetic code and its possible applications.
The essential aim of this conference is to bring together all the researhers whose focus is revolving
around the DNA molecule; be it fundemental or application research. On behalf of the organzing team
of the conference I sincerely hope that this conference will be immensely helpful in advancing the
existing knowledge and will lead to unravelling of further dimensions in this field.
Personally, I would like to thank all the members of Department of Physics and the members of Pilani
campus who put their sincere support in organizing this event. At the end, the financial support from
CSIR, DSTSERB, DST (Rajasthan), DRDO, New Delhi, India are gratefully acknowledged.
Navin Singh
(Convener, DNA Physics 2017)
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I I I Day (11-03-2017) (Sat urday )
SES SI ON – VI IC hair : A. Sain
9:00 – 9:30 AM A.N. Gupta9:30 – 10:00 AM Alok Shah
10:00 – 10:20 AM Rajdeep Choudhury10:20 – 10:35 A M Te a
SES SI ON – VI I IC hair : S . J alan
10:35 – 10:55 AM Rajesh Mehrotra10:55 – 11:15 AM Ashok Garai11:15 – 11:30 AM Concluding Remarks
12:30 PM - Lunch
I Day (09-03-2017) (Thur sd ay ) I I Day (10-03-2017) (Fr id ay )8.30 AM – 9.00 AM Registration9:00 – 9:30A M Ina ugura ti on SES SI ON – IV
9:30 – 10:00 A M Te a & Photo C hair : S .M. Bhat t achar jee9:00 – 9:45 AM S. Kumar
SESSI ON – I 9:45 – 10:30 AM M. PeyrardChair : Y. S ing h 10:30 – 10:45 A M Te a
10:00 – 10:45 AM S.M. Bhattacharjee10:45 – 11:30 AM Hermann Gaub S ES S ION – V
11:30 – 12:00 Noon G.V. Soni C hair : M. Pey rard12:00 – 12:30 PM R. Chakrabarti 10:45 – 11:15 AM Y. Singh12:30 – 12:55 PM D. Das 11:15 – 11:45 AM Rajeev Kapri
1:00 – 2:30 Lunch 11:45 – 12:15 PM S. Jalan12:15 – 12:35 PM J. Maji
SESSION – I I 12:35 – 1:00 PM Ajay AgarawalChair : H. Gau b 1:00 – 2:30 PM Lunch
2:30 – 3:00 PM P. Ranjith3:00 – 3:30 PM P.K. Mishra SESSION – VI
3:30 – 3:50 PM Te a C hair : S . Kumar2:30 – 3:00 PM A. Sain
SE SSION – I I I 3:00 – 3:20 PM P. DebnathChair : R. Kapr i 3:20 – 3:40 PM M. Suman Kalyan
3:50 – 4:20 PM G. Mishra 3:40 – 4:00 PM Himanshu Joshi4:20 – 4:40 PM Apratim Chatterji 4:00 – 5:30 PM Te a & Poste r4:40 – 5:00 PM Abhijit Ghosh
6:00 – 7:00 PM Visit to Sarswati Temple
Confe re nce di nne r a t VFA ST a t 8:00 PM D i nne r a t 8:00 PM in VFA ST
INVITED AND CONTRIBUTORY
TALKS
Perturbing DNA near its melting point
Somendra M Bhattacharjee
Institute of Physics, Bhubaneswar, India
Two different perturbations, force and a third strand, near the melting point of a double stranded DNA
will be considered in this talk. We show how a thermodynamic hypothesis provides the nature of the
force induced unzipping phase boundary near the melting point. We then discuss the role of bubble
fluctuations in establishing a long range attraction that leads to the state of three chain bound state when
no two are bound, a thermal analogue of the quantum Efimov effect.
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DNA as molecular force sensor
H.E Gaub
Lehrstuhl für Angewandte Physik und Center for NanoScience,
LudwigMaximiliansUniversität Amalienstr. 54 80799 München, Germany
The rapid development of scanned probe technologies allowing the precise application and measurementof minute forces has opened exciting new perspectives in bioanalytics. Interactions of DNA with otherpolynucleotides, with proteins and also small ligandscould be measured with unparalleled precision.However, the wide spread use of AFMbased bioanalytics is hampered by the limited throughput. Wedeveloped DNAbased molecular force balances as an alternative approach to measure the unbindingforce of intermolecular bonds in a differential format by comparison with a known reference bond. Inaddition to a marked increase in sensitivity and force resolution, this new approach allows for a parallelassay format, which is a prerequisite for most bioanalytical applications.The second block of this presentation will focus on the use of DNA as a programmable nanotool.Bottom up assembly of functional molecular ensembles with novel properties emerging fromcomposition and arrangement of its constituents is a prime goal of nanotechnology. With thedevelopment of SingleMolecule CutandPaste (SMC & P) we provided a platform technology for theassembly of biomolecules at surfaces.It combines the Å positioning precision of the AFM with theselectivity of DNA hybridization to pick individual molecules from a depot chip and allows to arrangethem on a construction site one by one. Anchors and handles are typically composed of DNA, butalternatively a broad range of ligandreceptor systems may be employed.
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Nucleotide and Nucleoprotein Complexes detection using Nanopore platform
Gautam V. SoniRaman Research Institute, Bangalore 560080, India
Structure Function relationship is ubiquitous in almost all of the nature's selfassembled systems. I will
introduce nanopore biophysics and its biosensing capabilities for studying structural heterogeneities in
biological systems. Spanning applications from technology to biology, I will first present my work on
developing nanoporebased novel DNA sequencing technology. This combines ultrafast single molecule
fluorescence microscopy to nanopore mesaurements to read out DNA sequence. In the second part of
my talk, I will show first ever application of solidstate nanopores in screening structural states of
nucleosomes and chromatin. Finally, I will show the new type of nanopore devices that we have built in
our lab and preliminary single molecule detection using them.
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Probing the Dynamics of Nucleic acids in Presence of CarbonBased Nanostructures
Soumadwip Ghosh and Rajarshi ChakrabartiDepartment of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai – 400076, India
The hybrids formed between single stranded DNA (ssDNA) and single walled carbon nanotubes
(SWCNT) are promising candidates for gene delivery vehicles. Using atomistic molecular dynamics
(MD) simulations we show that ssDNA wraps helically around the rigid SWCNT at low NaCl
concentration of the medium whereas at high salt concentration the binding gets weakened significantly
[1]. This is because of the fact that flexible ssDNA adopts a compact coillike state at higher salt
concentration where the nucleobases undergoes selfstacking and their affinity for the CNT sidewall
decreases. This is in good agreement with the divalent salt assisted structural collapse of the ssDNA
where a significant conformational transition from the collapsed to a reexpanded one is observed due to
overcharging at a higher concentration of MgCl2 [2]. Our simulations help understanding the
destabilization of the ssDNASWCNT hybrids and the ultimate detachment of the substrate from the
carrier inside the cell membrane for a successful gene delivery process [3]. Duplex nucleic acids, on the
other hand, are structurally more rigid than the single stranded ones. Apart from their ability to
accommodate small metal/molecular ions into their various binding sites [4], artificial duplex nucleic
acids can be useful for antisense applications in combination with a suitable transfecting career [5]. We
have recently shown that xylonucleic acid (XNA), an artificial RNA analog, undergoes spontaneous
unzipping on the surface of both SWCNT [6] as well as graphene [7] under various physiologically
relevant simulation conditions. The extent of XNA unzipping assisted by either of the nanostructures is
much faster than a naturally occurring RNA with identical sequence of nucleobases. We propose that the
combination of XNA and a flat graphene sheet is best suited for therapeutics since graphene with a
lower surface curvature ensures the optimal unwinding in XNA which in turn, can provide a long term
protection against the expression of a fatal gene in human serum [7].
References:1. Ghosh, S.; Patel, N.; Chakrabarti, R. J. Phys. Chem. B 2016, 120, 455 – 466.2. Ghosh, S.; Dixit, H.; Chakrabarti, R. Chem. Phys. 2015, 459, 137147.3. Tereshko, V.; Minasov, G.; Egli, M. J. Am. Chem. Soc. 1999, 121, 470471.4. Ghosh, S.; Dixit, M. K.; Chakrabarti, R. Mol. Simul. 2016, 42, 715 – 724. 5. Zamecnik, P. C. and Stephenson, M. L. Proc. Natl. Acad. Sci. U. S. A. 1978, 4, 75, 280281.6. Ghosh, S.; Chakrabarti, R. J. Phys. Chem. B 2016, 120, 3642–3652.7. Ghosh, S.; Chakrabarti, R. J. Phys. Chem. C 2016, 120, 22681 – 22693.
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First passage timescales of protein binding to target sites on DNA competing with nucleosomes
Dibyendu DasDepartment of Physics, IIT Bombay, Mumbai, India
It is being increasingly realized that nucleosome organization on DNA crucially regulates DNA–proteininteractions and the resulting gene expression. While the spatial character of the nucleosome positioningon DNA has been experimentally and theoretically studied extensively, the temporal character is poorlyunderstood. Many DNA binding proteins which regulate the activities of genes have to compete withnucleosomes to access and bind to specific target patches on DNA. We analytically solve and alsonumerically study this first passage problem of protein binding, within a kinetic model of bindingdissociating nucleosomes. As a concrete application of our general result, we estimate timescales ofTBP binding to TATA sites, genomewide in Saccharomyces cerevisiae. We find huge genetogenevariability of the timescales. We further study the variation of TBP binding timescales for a specificgene PHO5, as a function of factors which make its promoter switch from a transcriptional OFF to anON state. Reference:
1. Nucleic Acids Research, 44, 1630–1641 (2016)
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Understanding 3dimensional DNA organization in cells in the lengthscale of a gene
P. RanjithDepartment of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai – 400076, India
The fate of a cell is not just decided by the genetic code but also by the nature of the 3D organization of
the protein bound DNA, known as chromatin. Chromatin packaging is believed to be in a hierarchical
manner, and one of the crucial stages in the packaging is argued to be having a zigzag structure with
specific width of 30 nm. However, most of the recent experiments failed to find any zigzaglike ordered
arrangement of chromatin in living cells. In this work, we address this puzzle, and argue that any
regular, ordered, packaging of chromatin is unviable given that certain types of proteins can bind and
bend the chromosomal DNA.
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Effect of confinement and stiffness on the conformational change of a semiflexible homopolymer
chain
Pramod Kumar MishraDepartment of Physics, Kumaon University, Nainital, India
We analyse the nature of the confinement of an infinitely long (and finite) linear semiflexible homopolymer chain confined in between two geometrical constraints (A & B) under good solvent conditionin two dimensions. The constraints are stair shaped impenetrable lines. A lattice model of fully directedself avoiding walk is used to list information of walks of the confined chain and the exact enumerationtechnique is used for the canonical ensemble of conformations of the confined chain to discussequilibrium statistics of the chain. We obtain the probability of polymerization of the confined flexiblechain segments with either one end (polymer trains) or both the ends of the confined chain lying on thestair shaped constraints (polymer bridge and arc). We have also calculated the force of confinementexerted by the constraints on to the chain or the force exerted by the chain on the geometrical constraintsusing grand canonical ensemble theory and discuss nature of variation of the force.
Keywords: Confined Polymer, Exact Results, Analytical Solution
8
dsDNA to ssDNA: A sliding platform for protiens
Garima MishraDepartment of Physics, Indian Institute of Technology, Kanpur, India
Seperation of double stranded DNA (dsDNA) into two single stranded DNA (ssDNA) is prerequisite for theprocesses like replication and transcription. The inherent energetic heterogeneity involved in DNA makes the ATrich region less stable than GC rich region and leads to the bubble formation localized in AT rich region. I willdiscuss the role of the energetic hetrogeneity on the forcetemperature diagram of DNA, which is studiedextensively from theoretical models for homogeneous DNA. The newly generated ssDNA from dsDNA isthermodynamically less stable than dsDNA, and consequently, it spontaneously forms duplex secondarystructures (which inhibit subsequent DNAprocessing reactions). A solution to this problem comes fromspecialized ssDNA binding proteins (SSBs) that bind, protect, and stabilize the ssDNA structures. Complexesbetween SSBs and ssDNA are often highly stable, but predicting their structures is challenging, mostly because ofthe inherent flexibility of ssDNA and the geometric and energetic complexity of the interfaces that it forms. I willdiscuss about my coarsegrained model that predicts the structure of SSB–ssDNA complexes and also sheds somelight over energetics and the underlying association mechanism.
9
Role of special crosslinks in structure formation of DNA polymer
Apratim ChatterjiIndian Institute for Science and Educational Research, Pune, India
Using data from contact maps of the DNApolymer of E. Coli (at kilo base pair resolution) as an inputto our model, we introduce crosslinks between monomers in a beadspring model of a ring polymer atvery specific points along the chain. By suitable Monte Carlo Simulations we show that the presence ofthese crosslinks lead to a specific architecture and organization of the chain at large (micron) lengthscales of the DNA. We also investigate the structure of a ring polymer with an equal number of crosslinks at random positions along the chain. We find that though the polymer does get organized at thelarge length scales, the nature of organization is quite different from the organization observed withcross links at specific biologically determined positions. We used the contact map of ecoli bacteriawhich has around 4.6 million base pairs in a single chromosome. In our coarse grained flexible ringpolymer model we used 4600 monomer beads and observe that around 80 cross links are enough toinduce large scale organization of the molecule accounting for statistical fluctuations induced by thermalenergy.
10
Active Dynamics of Semiflexible Polymers
Abhijit GhoshMartin Fisher School of Physics, Brandeis University, USA
Active fluctuations, driven by processes that consume ATP, are prevalent in the living cells and aremostly driven by different forms of molecular motors. Such motors often move and transmit forcesalong biopolymers, which in general can be treated as semiflexible chains. We present a theoreticalanalysis of the active (out of thermal equilibrium) fluctuation of semiflex ible polymers, using bothanalytical and simulation methods. We find that enhanced diffusion, even superdiffusive, occurs in awelldefined temporal regime, defined by the thermal modes of the chain and the typical timescale ofthe activity. In addition, we find a dynamic resonancelike condition between the elastic modes of thechain and the duration of the active force, which leads to enhanced spatial correlation of localdisplacements. These results are in qualitative agreement with observations of cytoskeletal biopolymers,and were recently observed for the dynamics of chromatin in interphase cells. We therefore propose thatthe interplay between elasticity and activity is driving longrange correlations in our model system, andmay also be manifest inside living cells. Reference:
1. Dynamics of Active Semiflexible Polymers, Abhijit Ghosh and N S Gov, BioPhysical Journal,107, 2014
11
Statistical Mechanics of Driven DNA: Theory and Simulations
Sanjay KumarDepartment of Physics, Banaras Hindu University, Varanasi 221005, India
We propose a generic model of driven DNA under the influence of an oscillatory force of amplitude Fand frequency and show the existence of a dynamical transition for a chain of finite length. We findthat the area of the hysteresis loop, Aloop, scales with the same exponents as observed in a recent studybased on a much more detailed model. However, towards the true thermodynamic limit, the highfrequency scaling regime extends to lower frequencies for larger chain length L and the system has onlyone scaling Aloop ~ 1 F2. Expansion of an analytical expression for Aloop obtained for the model systemin the lowforce regime revealed that there is a new scaling exponent associated with force Aloop ~ 1
F2.5, which has been validated by highprecision numerical calculation. By a combination of analyticaland numerical arguments, we also deduce that for large but finite L, the exponents are robust andindependent of temperature and friction coefficient.
12
Probing DNA fluctuations, from the base pair to molecular conformations
Michel PeyrardLaboratoire de Physique, Ecole Normale Supérieure de Lyon, France
The image of DNA as a static and rigid double helix does not match its biological activity. Actually
DNA is a highly dynamical entity. Its fluctuations allow the reading of the genetic code and its
flexibility is necessary to pack it in the nucleus of a cell or in a virus capsid.
We discuss different views of these fluctuations at various scales:
• UVlaser twophoton ionization of the guanines, combined with standard biological methods can
probe the fluctuations at the scale of a few base pairs. We show that local fluctuations have
consequences that extend about 10 base pairs away.
• An analysis of magnetic birefringence data, which probe the flexibility of DNA, points out the
role of base pair fluctuations on the flexibility of the molecule at large scale.
• Small angle Xray and neutron scattering have been used to through a new light on the role of
some sequences to locate the nucleosomes at preferential positions, and on the recent debate on
the persistence length of short DNA chains.
References:
1. Santiago CuestaLópez, Hervé Menoni, Dimitar Angelov, and Michel Peyrard, Guanine radical
chemistry reveals the effect of thermal fluctuations in gene promoter regions, Nucleic Acids
Research 39, 52765283 (2011)
2. N. Theodorakopoulos and M. Peyrard, Base Pair Openings and Temperature Dependence of
DNA Flexibility, Phys. Rev. Lett 108 07810414 (2012)
3. Adrián Gonázlez Rodríguez, Torben Schindler, Ramachandran Boopathi, Lionel Porcar, Andrew
Wildes, Nikos Theodorakopoulos, Santiago CuestaLópez, Dimitar Angelov, Tobias Unruh and
Michel Peyrard, Small Angle Scattering of the conformations and flexibility of a short DNA
sequence: the case of a Nucleosome Positioning Sequence, unpublished
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Thermal Denaturation of DNA
Y. SinghDepartment of Physics, Banaras Hindu University, Varanasi 221005, India
The thermal denaturation of DNA is believed to be first order phase transition. In the PolandScheraga
type models DNA is considered as being composed of a sequence of alternating bound segments and
denaturated loops(bubbles). The statistical weight (partition function) of a bubble is found to behave as
lc. The nature of melting transition depends on value of exponent c. The talk will focus on finding value
of the exponent c.
15
Sequencing of semiflexible polymers through patterned pores
Rajneesh Kumar, Abhishek Chaudhuri, and Rajeev KapriDepartment of Physical Sciences, Indian Institute of Science Education and Research Mohali, Sector 81,
Knowledge City, S. A. S. Nagar, Manauli PO 140306, India
The knowledge of sequence of nucleotides within a DNA molecule is important for biological researchand various applications such as medical diagnosis, biotechnology, forensic investigations etc.Experiments have shown that the passage of single stranded DNA and RNA molecules throughbiological and synthetic nanopores result in a blockage of ionic current which would reflect theincoming sequence of the DNA. Theoretical approaches to study polymer translocation throughnanopores have focused primarily on flexible polymers. We study the translocation of a semiflexiblepolymer through pores with patterned stickiness. We show that the consequences of pore patterning onthe translocation time dynamics is dramatic and depends strongly on the stiffness of the polymer. Weutilize this dependence of translocation time on the microscopic structure of the pore and the polymerrigidity, to use an effective sequencing strategy. This strategy which involves using multiple pores withpatterned surface energetics, can predict heteropolymer sequences with varying bending rigidity to ahigh degree of accuracy.
16
Understanding diseaseome through molecular associations: A random matrix theory perspective
Sarika Jalan*
Centre for Biosciences and BioMedical Engineering, Indian Institute of Technology ,Indore 452 020, India
Complex Systems Lab, Discipline of Physics, Indian Institute of Technology, Indore 452 020, India
The inside of a cell is turbulent with activity, as enormous proteins, tiny molecules, and DNA strands windaround each other to accompany thousands of interactions. The disease state is a consequence of various flaws inmolecular interactions that eventually result in the altered dynamics of the expressions of infected molecules. Thegreatest challenge lies in understanding the relationship between these altered molecular interactions that leads inthe altered molecular pathways. Even after enormous researches, different diseases including cancers exhibitextensive heterogeneity, which complicates the pathway procedures and cell functioning thus demanding newtools to understand the cancer complexome at the basic molecular level. Further, the ample availability of varioustypes of experimental data from highthroughput techniques in molecular biology has lead to deeper insight ofvarious complex systems. Utilizing this vast information, rapid advancements in both experimental andtheoretical techniques have been performed in recent years. One such approach is the application of networktheory in combination with the spectral graph theory and Random matrix theory (RMT) approach on diseasessuch as cancer. Cancer being a multifactorial complexome requires comprehensive understanding for its properdiagnosis, screening and cure. Network science, spectral graph theory and RMT approach has shown itstremendous success in a wide variety of disciplines, being it as diverse as the human brain, the world wide web,scientific collaborations, communications and power systems engineering to molecular and population biology.These tools uncover the complexity of the disease and understand disease at the fundamental level enabling us tohave a global view of the diseasome. Constructing the networks for different cancers provide a unique platform tounderstand the altered interactions between the normal and the diseasedtissues, from the information andliterature available on various bioinformatics resources and helps improve our current knowledge of molecularassociations in diseases in a time efficient and cost effective manner. The technique may principally further leadto improvements in prediction of new drug targets and insights not only into cancer biology but also otherdiseases. This novel approach provides a clue to develop promising and nascent concept of single drug therapyfor multiple diseases as well as personalized medicine.
References:
1. Aparna Rai, Vipin Menon, and Sarika Jalan. "Randomness and preserved patterns in cancer network."Scientific reports 4 (2014).2. Sarika Jalan*, Alok Yadav. Assortative and disassortative mixing investigated using the spectra of graphs.Phys. Rev. E 91, 012813 (2015).3. Aparna Rai, Amit K. Pawar, and Sarika Jalan. "Prognostic interaction patterns in diabetes mellitus II: Arandommatrixtheory relation." Physical Review E 92.2 (2015): 022806.4. Sarika Jalan, Krishna Kanhaiya, Aparna Rai, Obul Reddy Bandapalli, Alok Yadav. "Network TopologiesDecoding Cervical Cancer." PloS one 10.8 (2015).5. Sanjiv K. Dwivedi, and Sarika Jalan. "Interplay of mutation and disassortativity." Physical Review E 92.2(2015): 022802.6. Alok Yadav, and Sarika Jalan. "Origin and implications of zero degeneracy in networks spectra." Chaos: AnInterdisciplinary Journal of Nonlinear Science 25.4 (2015): 043110.7. Pramod Shinde, Alok Yadav, Aparna Rai, and Sarika Jalan. "Dissortativity and duplications in oral cancer."The European Physical Journal B, 88, no. 8 (2015): 17.8. Aparna Rai, Priodyuti Pradhan, Jyothi Nagraj, K. Lohitesh, Rajdeep Chowdhury, Sarika Jalan. “Understandingcancer complexome using networks, spectral graph theory and multilayer framework.” Scientific reports (2017)(in press)
Email: [email protected]
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The bubblebound state of a triplestranded DNA
Jaya MajiDepartment of Physics, Indian Institute of Science and Educational Research, Bhopal, India
The presence of a thermodynamic phase of a threestranded DNA, namely a phase of bubbles of twobound and one single strands, is established by using exact real space renormalization group (RG)transformations for dimensions d>2 and equivalent exact computations for fractal Sierpinski gasket ofdimension d<2. In contrast to the EfimovDNA, where three strands are bound without duplex binding,a new phase of DNA with pairwise binding but without three chain contacts appears on the bound sideof the two chain phase boundary. The strand exchange between one strand of the pair and the singlestrand keeps the phase stable. This new phase, which is characterized by a separate RG flow in d>2, canbe identified from direct calculations for d<2.
19
NanoTechnologies for Single Nucleotide Polymorphisms (SNP) DetectionAjay Agarwal
CSIRCentral Electronics Engineering Research Institute & Academy of Scientific & Innovative Research, PILANI (RAJ.) – 333 031, INDIA (Email: [email protected])
Nanotechnologies along with standard silicon microfabrication technologies have enabled novel nanodimensional materials, structures and eventually devices which find numerous applications in the fieldof medical diagnostics, drug delivery, electronics, energy production, detecting food adulterants, waterpollutants, etc. With the increasing awareness, healthcare is particularly in focus that includes earlydiagnosis, drugs discovery, pointofcare solutions, etc. For these biomedical applications, specific andsensitive detection of various biological and chemical species becomes crucial.Single nucleotide polymorphism (SNP) detection technologies are important to know newpolymorphisms and to determine the allele(s) of a known polymorphism in target sequences. SNPdetection technologies have been labor intensive, time consuming and expensive since recently wheresome automated, efficient, and relatively inexpensive methods have been demonstrated. The number ofSNP genotyping methods increasing but the demand for SNP detection is enormous. A new approach todetect SNPs in multiplexed scenario is presented using nanostructured biosensors.References:
1. Ajay Agarwal, et al., Sensors and Actuators A: Physical, 145146, 207 (2008)2. N. Singh, A. Agarwal, et al., IEEE Transactions on Electron Devices, 55, 3107 (2008)3. Z. Gao, A. Agarwal, et al., Analytical Chemistry, 79 (9), 3291 (2007)4. X. Bi, A. Agarwal, et al., Biosensors Bioelectronics, 23, 1442 (2008)5. TS Pui, Ajay Agarwal, F. Ye, N. Balasubramanian, P. Chen, Small, 5, 208 (2009)6. R Prajesh and Ajay Agarwal, BioNanoSci, 2, 218 (2012)7. R Prajesh, P B Agarwal and Ajay Agarwal, BioNanoSci, 2, 223 (2012)8. Ranjan K Maurya and Ajay Agarwal, FluidFET Controller for Microfluidic Devices, IEEE Sensors, doi
10.1109/JSEN.2015.2456233.
20
Spontaneous formation of membrane tubes
Anirban Sain,
Indian Institue of Technology, Bombay, Mumbai
Membrane tubes are common in Biology at the level of single cells. Many recent examples have
emerged where tubes grow from phospholipid vesicles due to ATP dependent active forces. We will
discuss one such case where tubes seem to spontaneously grow from polymer coated vesicles.
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Rupture dynamics in model polymer systems
Rupam Borah and Pallavi Debnath *Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee247667, India
(Email: [email protected] )
I will discuss the rupture dynamics of a model polymer system to capture the microscopic mechanismduring relative motion of surfaces at the single polymer level. Our model is similar to the model forfriction introduced by Filippov, Klafter, and Urbakh [Filippov et al., Phys. Rev. Lett., 2004, 92,135503]; but with an important generalization to a flexible transducer (modelled as a bead springpolymer) which is attached to a fixed rigid planar substrate by interconnecting bonds (modelled asharmonic springs), and pulled by a constant force FT. Bonds are allowed to rupture stochastically. Themodel is simulated, and the results for a certain set of parameters exhibit a sequential rupturemechanism resulting in rupture fronts. A mean field formalism is developed to study these rupture frontsand the possible propagating solutions for the coupled bead and bond dynamics, where the couplingexcludes an exact analytical treatment. Numerical solutions to mean field equations are obtained bystandard numerical techniques, and they agree well with the simulation results which show sequentialrupture. Within a travelling wave formalism based on the Tanh method, we show that the velocity of therupture front can be obtained in closed form. The derived expression for the rupture front velocity givesgood agreement with the stochastic and mean field results, when the rupture is sequential, whilepropagating solutions for bead and bond dynamics are shown to agree under certain conditions.
References:
1. R. Borah and P. Debnath, Soft Matter, 2016, 12, 4406 – 4417.
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Monte Carlo study of periodically driven DNAM. Suman Kalyan* and Rajeev Kapri$
Department of Physical Sciences, Indian Institute of Science Education and Research Mohali, Sector 81,Knowledge City, S. A. S. Nagar, Manauli PO 140306, India
Email: * [email protected], [email protected]
We study the hysteresis in unzipping of a double strand DNA (dsDNA) subjected to a periodic force,with amplitude g0 and frequency , using Monte Carlo simulations. In an earlier study [1] it was foundthat at a fixed temperature the loop area Aloop increases as is increased. It reaches a maximum atfrequency , which depends on force amplitude g0, and then decreases. It was found that Aloop decreasesmonotonically for lower values of g0 but shows an oscillatory behavior for higher values of g0 . Here, westudy the temperature dependence of the hysteresis loop as a function of temperature T, amplitude g0,and frequency . We find that as temperature is increased Aloop starts showing oscillatory behavior evenfor lower values of g0 . We also study the scaling behavior of Aloop as a function of T, g0 , and .
References:
1. R. Kapri, Phys. Rev. E, 90, 062719 (2014).
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Understanding DNA Based Nanostructures using Molecular SimulationsHimanshu Joshi and Prabal K. Maiti
Centre for Condensed Matter Theory, Department of Physics, Indian Institute of Science, Bangalore 560 012, India
DNA is arguably the most important biological molecule. Recent decades have witnessed the synthesisof many DNA nanostructures with proposed applications in nanotechnology. State of the art moleculardynamics (MD) simulations can be very useful to understand the microscopic structure of these selfassembled structures at nanoscale. We have developed algorithms to build very accurate 3d atomisticmodels of various DNA nanostructures like crossover DNA molecules, DNA nanotubes (DNTs) andDNA polyhedra. We investigate the structure, stability and mechanical properties of various DNAnanostructures in salt solution. We find that the persistence length of DNA nanotubes is of the order ofmicrometer. We have also examined the interaction of DNA nanotubes embedded in the lipid bilayermembranes. We discover that the local rearrangement of lipid molecules can stabilize the DNAnanotubes in the bilayer and DNA backbone modification is not necessary for the partitioning of DNTsin lipid bilayer. The Ohmic conductance measured from IV characteristics of the ions channel variesfrom 4.3 to 20.6 nS with ionic strength. The simulation studies with atomistic model of DNAicosahedron reveal the dynamical behavior of the structure and its interaction with encapsulated cargo.We believe that our simulation studies will give further impetus in the design and development ofstructural DNA nanotechnology.
References:1. Joshi et al. PCCP 2015, 17, 14241434.2. Joshi et al. ACS Nano 2016, 10, 77807791.3. Bhatia and Joshi et al. Nature nanotechnology 2016.
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DNA in a crowding environmentAnurag Singh, Suparna Khatun and Amar Nath Gupta
Biophysics and Soft Matter Laboratory, Department of Physics, IIT Kharagpur, India721302
With a view to understand compaction of DNA in crowded conditions, we have measured the radius ofgyration of plasmid in its supercoiled and linear forms in the presence of dextran nanoparticles throughlight scattering. It was observed that the supercoil initially expands and subsequently compacts withincreasing volume fraction of the dextran having smaller size. The plasmid does not collapse into acondensed state. Our results show first, the supercoil expands through a modification of its geometricalproperties by the depletion induced attraction between the two opposing duplexes of the superhelix andsecond, the molecule gets compressed due to the depletion of nanoparticles in the interior of the coilwith concomitant imbalance in osmotic pressure between the coil and surrounding medium. Theantagonistic nature of these two aspects of crowding results has a much more pronounced and richereffect on the dimensions of supercoiled plasmid than the effect of variation in ionic strength. We havealso studied the effect of binding ligand to DNA which changes the elastic property of DNA at singlemolecule level through AFM. When a dsDNA molecule is overstretched in the presence of ligands, itundergoes a cooperative structural transition based on the externally applied force, the binding constantof the ligands to the DNA, the concentration of the ligands and the ionic strength of the supportingmedium. These transitions were studied by the extended and twistable wormlike chain model. Weconclude that besides ionic strength, interacting proteins and content of AT and GC base pairs, theligand binding or intercalation with the ligands is an important parameter which changes the stiffness ofDNA.
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Role of Biosensors in Defense
Alok ShahLife Sciences Research Board (LSRB), DRDO HQ., New Delhi110011
Defense is one of the largest consumers of fresh, semiprocessed and processed food and otheragricultural commodities. In a country like India, the lack of phyto and phytosanitary protocols in theagrifood market has potentially increased biological, chemical and physical threats to food products,catapulting a demand both in Defense and the civil market at large on more effective and better processcontrol, quality and safety of these products. Biosensors can play a pivotal role in controlling productionprocesses and ensuring greater agricultural and food quality by putting in place fast, reliable andaffordable monitoring procedures. The advantage of biosensors lie in providing an alternate mechanismto conventional analytical tools and techniques in terms of size, costeffectiveness, specificity, rapidresponse, sensitivity, repeatability and precision. Food and agricultural production chain is vulnerable todifferent kind of threats at every step in terms of loss of quality and susceptibility to transmit diseasesthrough falling prey to microbial, fungicidal, pesticidal, weedicidal and insecticidal invasions. Thesemicrobial, biological, chemical and/or physical threats can be due to environmental contamination orfailures to stick to standard food handling, processing, packaging and distribution quality proceduresand protocols. A properly developed biochip in a biosensor can capture the molecular and geneticsignatures of various contaminants. Biosensors can not only detect, analyse and quantify molecules ofdifferent biological origins but also throw light on the quality of food or agricultural produce in terms oftheir residual loads of esticides, fertilizers, agrochemicals, dioxins; besides, biosensors can provideinformation on contaminated water, soil residues, genetically modified organisms, pathogenicmicroflora and their toxins, food antinutrients, allergens, drug residues, additives and hydrocarbons,etc. Biosensors can also diagnose changes in the food composition in the aftermath of postharvestpractices, operations and processing through realtime monitoring of various variables such as pH,temperature, pressure, oxygen, flow and volatile components; and, thus, help in the implementation ofhazard analysis and critical control points (HACCP) by identification and detection of food bornepathogenic threats, chemical and biochemical contaminants. The need of the hour is to develop a multiutility biosensor that embeds, within its design, features to function as a chemical, temperature,pressure and pHsensor as well, in addition to picking up molecular and genetic traits of more than onemicroorganism or an analyte. An intelligently designed and developed biosensor can effectively screenair, water, soil, agromaterial, food, water bodies, fresh and waste plant and animal material to mitigatethe biothreat paradigm by rapid detection of biothreat pathogens and agents and their toxic, and orpathogenic analytes and metabolites. 'Detect to Protect' biosensors, at different scales of developmentand ecodeployment, can provide an effective shield against biological warfare (BW) agents.
Email: [email protected]
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A transcriptomic analysis pipeline decoding network of genes involved in different stages leadingto acquisition of cancer drug resistance
J Nagraj, M. Vasudevan, S. Jadav, G. Mishra, S. Mukherjee, S. Chowdhury S and Rajdeep ChowdhuryDepartment of Biological sciences, BITS, Pilani, Rajasthan 333031, India
Existing evidences suggest survival of a distinct population of cancer cells that resist chemotherapeuticshock, eventually evolving into drug resistant cells. This is considered, a cause to treatment failure andsubsequent relapse. Identifying appropriate drug/s that can eliminate these drugtolerant “persisters” stillremains an issue in cancer therapy. Hence, deeper understanding of the distinctive genetic signaturesand genetic boundaries between untreated cells, drug treated cells, persisters following drug shock andpersisterderived resistant cells is of utmost importance. In this study, through deep sequencing of bothmRNA and small RNAs we have generated a transcriptomic network that provides critical insights intothe molecular events leading to emergence of persister subpopulation of cells post cisplatin shock, andstrategies acquired by these cells to evade persister bottleneck leading to emergence of drugresistantcancer cells. The conventional drug, cisplatin which is an integral part of current treatment regime formultiple cancer types is opted for this study. Both receptor mediated signaling and intracellularsignaling were found to be deregulated. A core network of genes showing altered expression wereidentified across the different stages of acquisition to resistance. This study is uniquely designed tobetter understand the series of genetic events leading to the surfacing of drug resistance in osteosarcomacells, and implications from this study can have potential future therapeutic impact.
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ICRF193 delays spindle elongation and produce archery bow phenotype in dividing fission yeastcells
Rajesh Mehrotra1,#, Norihiko Nakazawa1, and Mitsuhiro Yanagida1,*1G0 Cell Unit, Okinawa Institute of Science and Technology Promotion Corporation, Uruma, Okinawa 9042234, Japan
# Department of Biological sciences, BITS, Pilani, Rajasthan 333031, India
ICRF193, a noncleavable, complex stabilizing topoisomerase (topo) Ⅱ inhibitor, has been shown totarget topo in mammalian cells. With the aim of elucidating the roles of topo in dividing Ⅱ Ⅱ S. pombecells, we examined the effects of ICRF193 treatment on such cells. ICRF193 treated cells showschromosome segregation defect and archery bow phenotype. This phenotype is different than top2191mutant cells phenotype. The study involving cs nda3 indicated that ICRF193 treatment delaysmetaphase to anaphase transition in S. pombe cells compared to the DMSO treated control cells. It isreported that anaphase inhibitor securin is kept stable during such delay. The spindle characteristicswere severely affected by the drug treatment. Phase2 and Phase3 of spindle elongation were not distinctas previously reported for top2191 mutant cells but more interestingly, the ICRF193 treated cellsshowed constant spindle elongation speed in Phase2 and Phase3 supporting the delay induced by ICRF193 treatment which ultimately results into archery bow phenotype.64 percent of the dividing cellshowed archery bow phenotype after 2 hours of ICRF193 treatment. Using fixed cells of Top2GFP, we could observe the dot signal of GFP in ICRF193 treated cellscompared to the DMSO treated cells, indicating the trapped topo on the DNA after ICRF193Ⅱtreatment. In short ICRF193 treatment is effective in S. pombe cells. ICRF193 affects the dividing S.pombe cells by inhibiting the spindle characteristics and results in archery bow phenotype. This is thefirst report of ICRF193 treatment in S. Pombe. The data will be presented in the conference.
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Elastic properties and conformational changes of DNA: An allatomistic molecular dynamics studyAshok Garai
Department of Physics, The LNMIIT, Jaipur, India
Active Biological processes, like transcription, replication, recombination, DNA repair, and DNApackaging encounter bent DNA. Machineries associated with these processes interact with the DNA atsuch a short length scale. Thus the study of elasticity and conformational changes of DNA at such lengthscale is crucial. Molecular dynamics simulations can be used to extract various conformational duringstretching and other biomolecular properties of DNA through a systematic study of fluctuations at theatomic level. Atomistic molecular dynamics simulations aid to calculate different elastic properties ofvarious DNAs starting from short free DNA to nucleosomal DNA. Furthermore, it is found thatmacroscopic elastic theory is not adequate to calculate the elastic properties of various short DNAs.Stretching of DNA under different pulling protocols can provide a detailed picture of variousconformational changes of DNA and also brings forth fundamental molecular understanding of DNAstretching mechanism. Such realistic studies will certainly enrich the pool of techniques to interpret theexperimental data as well as motivate to perform new experiments.
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Poster Presentations
Change in flexibility of DNA with binding ligandsAnurag Singh and Amar Nath Gupta1
Soft Matter Laboratory, Department of Physics, Indian Institute of Technology Kharagpur, India721302
The percentage and sequence of AT and GC base pairs and charges on the DNA backbone contributesignificantly to the stiffness of DNA. This elastic property of DNA also changes with small interactingligands. The singlemolecule force spectroscopy technique shows different interaction modes bymeasuring the mechanical properties of DNA bound with small ligands. When a dsDNA molecule isoverstretched in the presence of ligands, it undergoes a cooperative structural transition based on theexternally applied force, the mode of binding of the ligands, the binding constant of the ligands to theDNA, the concentration of the ligands and the ionic strength of the supporting medium. This leads to thechanges in the regions upto 60 pN, cooperative structural transition region and the overstretched region,compared to that of the FEC in the absence of any binding ligand. The cooperative structural transitionswere studied by the extended and twistable wormlike chain model. Here we have depicted thesechanges in persistence length and the elastic modulus constant as a function of binding constant and theconcentration of the bound ligands, which vary with time. Therefore, besides ionic strength, interactingproteins and content of AT and GC base pairs, the ligand binding or intercalation with the ligands is animportant parameter which changes the stiffness of DNA.
1 [email protected] , [email protected]
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Study of translocation of ssDNA and dsDNA through nanopore sites
Anurag Upadhyay, Dibyajyoti Mohanta, S. Kumar* and D. GiriDepartment of Physics, IIT BHU, Varanasi 221005, India
*Department of Physics, Banaras Hindu University, Varanasi 221005, India(1 & 2 are presenting coauthors)
We examine doublestranded and singlestranded DNA translocation through nanopores by means of
molecular dynamics (AMBER and NAMD software) and also Monte carlo simulation.The DNA motion
is found to be independent of the crosssection of nanopores.This happens due to the competition
between two forces the adhesion of DNA bases to the nanopore sites and the mechanical forces which
act along the length of the DNA as it is attached to one end. We also try to understand the Efimov effect
of triple stranded DNA.
Denaturation of DNA at high salt concentrationsArghya Maity and Navin Singh
Department of Physics, Birla Institute of Technology & Science, Pilani(Email: [email protected])
Intracellular sodium triggers a cell to progress in to cell division. So, intensifying of Nacl makes a
dreadful manifestation of cell. The DNA phase transition effect has been studied and established at low
strength of salt in theoretical and experimental aspects. Intracellular positive ions widen nucleic acid
flexibility through nullifying the negative charges on the phosphates of DNA strand. So dsDNA chain
gets more stability. However the behaviour of DNA at high salt strength is still theoretically ambiguous
beacause the experimental studies of salt on DNA apprise a hostile nature after a certain strength. How
the DNA strand breaks in this hypotonic medium so promptly and turn out to be unstable, is the aim of
our manuscript. We outline a corelated biological phenomenon like tumor cells specifically Cancer cells
since these type of cells carry a dissimilar aspect from normal somatic cells of high intracellular
concentration of Nacl. We try to delineate this nature of salt in theoretical aspect using Peyrard Bishop
Dauxois model and also try to scrutinize the stability and unstability slope of this nature of salt from the
graph.
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Understanding ProteinProtein Interactions of Cancer Complexome
Aparna Rai1,a, Priodyuti Pradhan2, Jyothi Nagraj3, K. Lohitesh3, Rajdeep Chowdhury3, and Sarika Jalan1,2,b
1Centre for Biosciences and BioMedical Engineering, Indian Institute of Technology, Indore 453552, India2Complex Systems Lab, Discipline of Physics, Indian Institute of Technology, Indore 453552, India
3Department of Biological Sciences, Birla Institute of Technology & Science, Vidya Vihar, Pilani, Rajasthan, 333031, IndiaEmail: a [email protected], b [email protected] , Group page: http://iiti.ac.in/people/~sarika/
Different diseases including cancers exhibit extensive heterogeneity, which complicates the pathwayprocedures and cell functioning. Development of statistical tools inspired from other branches ofsciences, particularly from graph theory and random matrix theory enables us to have a global view ofthe diseasome. Constructing the networks for different types of cancers provide a unique platform tounderstand the altered interactions in the diseased tissues, utilizing the information and literatureavailable on various bioinformatics resources. Cancer being a multifactorial complexome requirescomprehensive understanding for its proper diagnosis, screening and cure. These tools uncover thecomplexity of the disease and understand disease at the fundamental level. Hence, exploring moleculemolecule associations through the holistic combined framework of the systems biology approach,network theory and multilayer approach is expected to trace differences in the associations of normaland disease states and improve our current knowledge of molecular associations in diseases in a timeefficient and cost effective manner. It may principally be lead to further much required improvements inprediction of new drug targets and in sights into the cancer biology.
References:
1. Aparna Rai, Priodyuti Pradhan, Jyothi Nagraj, K. Lohitesh, Rajdeep Chowdhury, Sarika Jalan,“Understanding cancer complexome using networks, spectral graph theory and multilayerframework.” Scientific reports (2017) (in press).
Study of LennardJones systems using Molecular Dynamics Simulation
Pallabi Kundu and Pankaj Mishra
Department of Applied Physics, Indian Institute of Technology (Indian School of Mines) Dhanbad826004, India
Email: p [email protected]
We discuss the numerical simulation techniques as a method of scientific study of real systems. Varioussimulation techniques has been described with special emphasis on molecular dynamics simulationwhich was studied in details and discussed followed by a few illustrative examples. A system ofparticles interacting via LennardJones potential is studied and a few static properties are calculated.Computation was done in the regime of MD simulation following the constant energy criteria where thekinetic energy of the system is a function of temperature alone.
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AC Magnetic Fields Dependent Measurement on DNA Engineered Cobalt Ferrite For Biomedical
Application
Arpita Das1, Debarati De1, Prof. Ajay Ghosh1, Madhuri Mandal2
1CRNN, University of Calcutta,Kolkata, 700098, India2S.N.Bose National Centre for Basic Science, Kolkata 700098, India
EMail address (corresponding author): [email protected]
The cobalt ferrite nanoparticles have suitable property which may provide a new direction in medicalscience.These particles can be controlled by the magnetic fields from outside the body.
For biomedical application these cobalt ferrite nanoparticles was properly engineered with DNA.Herecobalt ferrite nanoparticles were synthesized on DNA scaffold by wet chemical coprecipitation method.Different batches of particle were synthesized by varying the amount of DNA.The cobalt ferritenanoparticles attached with DNA was analyzed by infrared spectroscopy (IR), scanning electronmicroscope (SEM), Transmission electron microscope(TEM), squid, Xray diffraction (XRD), Dynamiclight scattering (DLS) etc. From XRD data it was confirmed that the above mentioned nanoparticles iscobalt ferrite in pure phase and from IR and SEM analysis it was shown that cobalt ferrite nanoparticleswere attached with DNA. It was investigated from SQUID data that with increasing amount of DNA,cobalt ferrite nanoparticles showed different magnetic properties. From DLS data the exact size of theparticle was concluded. From IVCV measurement it shown the Negetive Differential Resistance whichwill be helpful for charge storage for future application. The DNA bounded cobalt ferrite also taggedwith fluorescence dye so that the path of their movement can be tracked from outside of the body.
A comparative study have been done by keeping the different batches of MNP (magnetic nano particle)attached in cancer cells in the Hyperthermia circuit for varying time. This particle under AC magneticfield produce suitable heat which is very significant for Hyperthermia Therapy.
References
1. Johannsen, M., et al, Hyperthermia, 21, 635(2005)2. Ferrari, M., Nat. Rev. Cancer 5, 161, (2005)
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Fig. 1: Circuit for Hyperthermia Treatment Fig. 2: BioSEM image of DNA attached MNP
DNA functionalized cobalt ferrite nanoparticles: a betterment in internalization with cell and
cytotoxicity level
Debarati De1, Arpita Das1, Prof. Ajay Ghosh1, Madhuri Mandal2 1CRNN, University of Calcutta, Kolkata, 700098, India
2S.N.Bose National centre for Basic Science, Kolkata 700098, IndiaEMail address (corresponding author): [email protected]
Different batches of cobalt ferrite nanoparticles (CoFe2O4, CoFe2O4DNA) with average size in therange between 20 nm were synthesized using the Wet chemical co precipitation method. The cobaltferrite nanoparticles attached with DNA was analysed by infrared spectroscopy (IR), X ray diffraction(XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), squid etc.Cytotoxicity and biocompatibility of these particles were also analyzed in human mammary carcinomacell lines (MDAMB231) where different amount of doses of different batches were added to the cells.Here Cell viability is measured as the percent live cells compared with untreated control. From the studyit was seen that the CoFe2O4 NPs shows itself cytotoxic effect in case of cancer cell but is biocompatiblein case of normal peripheral blood mononuclear cell (PBMC). From the above mention study it was alsoseen that the DNA bound cobalt ferrite (CoFe2O4DNA) NPs shows less toxic effect and betterinternalization of particles compared to the bare cobalt ferrite (CoFe2O4) Nps.
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Fig 1: Without DNA + RITC Fig 2: 0.4 DNA NPs + RITC Fig 3: 0.8 DNA + RITC
Figure: Internalization of cobalt ferrite NPs and different amount of DNA bound cobaltferrite NPs in MDAMB231 cell.
Role of DNA bending nonhistone proteins in higherorder structure of Chromatin
Gaurav Bajpai1, Ishutesh Jain1, Mandar M. Inamdar2, Dibyendu Das3, Ranjith Padinhateeri1
1Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India2Department of Civil Engineering, Indian Institute of Technology Bombay, Mumbai, India
3Department of Physics, Indian Institute of Technology Bombay, Mumbai, India
In eukaryotes, DNA is packaged inside the nucleus in the form of chromatin. Chromatin is acombination of protein and DNA. We know from our molecular biology text books that three levels ofchromatin organization are found in the cell. (i) DNA wraps around histone proteins form nucleosome,the beads on a string structure. (ii) Multiple nucleosomes wrap into a 30 nm fiber consisting ofnucleosome arrays in their most compact form. (iii) Higherlevel DNA packaging of the 30 nm fiberinto the metaphase chromosome. In lots of experiments it has been found that 30 nm structure exists invitro. But in vivo evidence of this type of structure is not very visible. Why we sometimes see 30 nmstructure and sometime not, is a puzzle. The fundamental physical principles behind the formation of aregular 30nm structure are the orientations of DNA entering/exiting nucleosomes and the bendingelasticity of linker DNA between nucleosomes. In the conference, we present our theoretical modelwhich explain that once we consider the presence nonhistone protein (nhp6, HMG etc.) that bind andlocally bend linker DNA, the existence of regular structure are not feasible. Our model is comparablewith recent MicroC experiment which explain chromatin structures inside the cell are irregular andcontact probability of neighbor nucleosomes and next neighbor nucleosomes are equal.
References:
1. Bajpai G, Jain I, Inamdar MM, Das D, Padinhateeri R, Binding of DNAbending nonhistone proteins destabilizes regular 30nm chromatin structure, PLoS Comput Biol 13(1): e1005365 (doi:10.1371/journal.pcbi.1005365)(2017)
Kinetics of Tumbling of polymers in shear flow
Sadhana Singh and Sanjay KumarDepartment of Physics, Institute of Science, Banaras Hindu University, Varanasi, 221005 India
To study the kinetics of tumbling and conformational change of polymer system in shear flow, we have
developed a coarsegrained model for flexible polymer chain. Based on the numerical simulation, the
static and dynamic properties of a single polymer in shear flow is studied. The observed properties are in
general agreement with results reported in the literature. The cyclic motion phenomenon is studied by
power spectrum density analysis.
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Codon based cooccurrence network motifs in human mitochondriaPramod Shinde*, Camellia Sarkar, Sudeep Tiwari$, Sarika Jalan
Complex Systems Lab, Discipline of Physics, Indian Institute of Technology, Indore 453552, IndiaEmail: *[email protected], [email protected] (presenting coauthors)
The nucleotide polymorphism in human mitochondrial genome (mtDNA) tolled by codon position biasplays an indispensable role in human population dispersion and expansion. By analysing codon positionbias captured by nucleotide cooccurrence over mtDNA, we develop a powerful network model todescribe complex mitochondrial evolutionary patterns between codon and noncodon positions. It isinteresting to report a different evolution of Asian genomes than those of the rest which is divulged bynetwork motifs in noncoding regions. Most notably, codon motifs apparently underpin the preferencesamong codon positions for coevolution which is probably highly biased during the origin of the geneticcode accompanied by their comparison with random variants. Our analyses manifest that codon positioncoevolution is very well conserved across human subpopulations as well as independently maintainedwithin human subpopulations implying the selective role of evolutionary processes on codon positioncoevolution. Ergo, this study provides a framework to investigate cooperative genomic interactionswhich are critical in underlying complex mitochondrial evolution.
Statistical mechanics of a polymer chain attached to the interface of a coneshaped channelSanjiv Kumar, S. Kumar and D. Giri#
Department of Physics, Banaras Hindu University, Varanasi 221005, India#Department of Physics, IITBHU, Varanasi 221005, India
We study equilibrium properties of a short polymer chain attached to the one end of a coneshapedchannel. Depending on the solvent quality (good or poor) across the channel, a polymer chain can beeither inside or outside the channel or both. Exact results based on a short chain revealed that when thesolvent quality remains the same across the interface, the polymer prefers to stay outside the channel.Surprisingly, when the quality of solvent inside the channel is relatively poor than the outside, eventhen, polymer prefers to stay outside at lower temperature. Our results demonstrate that a slight variationin the solvent quality can drag polymer chain inside the pore and vice versa. Furthermore, we also reportthe absence of crystalline (highly dense) state when the poresize is less than the certain value. Wedelineate the possible mechanism, which may have potential application in understanding of thebiological processes.
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Translocation of a semiflexible polymer through sticky poresRajneesh Kumar*, Abhishek Chaudhuri and Rajeev Kapri$
Department of Physical Sciences, Indian Institute of Science Education and Research Mohali, Sector 81,Knowledge City, S. A. S. Nagar, Manauli PO 140306, India
Email: * [email protected], [email protected]
We study the driven translocation of a homogeneous semiflexible polymer through an extended porethat interacts with the polymer. We consider pores with different patterned stickness and study how thetranslocation process depends on the bending stiffness of the polymer. We find, similar to earlierstudies, that a stiffer polymer takes more time to translocate through patterned pores. We then considerthe driven translocation of a semiflexible chain consisting of alternate blocks of stiff and flexiblesegments through the patterned pores. In this case we find that the translocation time depends stronglyon the pore pattering. The waiting time distributions, of the monomers of the polymer, which givesextensive information of the translocation dynamics, show novel features attributed to the frictionexperienced inside the pore due to varying porepolymer interactions and finite lengths of the pores.
Melting and Unzipping of ThreeStranded DNATanmoy Pal and Sanjay Kumar
Institute of Science, Department of Physics, Banaras Hindu University, Varanasi 221005, India.
We study thermal melting and forced unzipping of a short threestranded DNA comprised of twoidentical single strands made of T bases only and a third strand of equal length but made of A basesonly. By allowing the WatsonCrick base pairing, implemented through LennardJones potential, we doLangevin dynamics simulation for a range of temperature and unzipping force. At zero unzipping force,be low a critical temperature, the system stays in a threestranded bound state which has been reportedin the literature as ”mixed state”. Next, we apply an unzipping force at the ends of the two Tstrands andstudy the endpoint separations as a function of the unzipping force. As direct Hydrogen bondingbetween two Tstrands is not allowed, we get interesting forceextension curves which we can explainthrough quantities related to denaturation bubbles.
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