Maikel Rheinstädter, XPCS NSLS II Workshop, BNL, January 10th, 2008 1

Maikel C. RheinstädterDepartment of Physics and Astronomy

University of Missouri – Columbia

XPCS NSLS-II WorkshopJanuary 10-11, 2008

Brookhaven National Laboratory

The Impact of Collective Molecular Dynamics on Physiological and

Biological Functionalities of Artificial and Biological Membranes

Maikel Rheinstädter, XPCS NSLS II Workshop, BNL, January 10th, 2008 2

Biological Physics is…

Aims and Scope, European Biophysical Journal:

“Although living systems obey the laws of physics and chemistry, the notion of function or purpose differentiates biology from other natural sciences” (Hartwell et al.)

OrganismOrgan

CellOrganelle

CytoskeletonFunctional Module

Biological MacromoleculeMolecule

Atom

Hierarchy of biological systems:

“… a distinctively biophysical approach at all levels of biological organization will be considered, as will both experimental and theoretical studies”

“the study of biological phenomena using physical methods and concepts … the primary goal …is to advance the understanding of biological structure and function by application of the principles of physical science”

Maikel Rheinstädter, XPCS NSLS II Workshop, BNL, January 10th, 2008 3

Hard- and Soft-Matter

BiophysicsBiology

Soft-Matter

missing or not well developed periodic

structure (BZ concept)

‘multi-scale’: relevant dynamics in a large

range of length and time scales

high ‘intrinsic’background because of mix

of coherent an incoherent scattering and diffusion and

different molecular components

Maikel Rheinstädter, XPCS NSLS II Workshop, BNL, January 10th, 2008 4

The Cell Membrane

Applications:

Bioengineering:Tailor membranes with

specific properties

Understanding of physiological and biological functionalities:

Drug transport

D. Neumann, Saarbrücken, Germany

Membrane is the primary site of (inter)action

Maikel Rheinstädter, XPCS NSLS II Workshop, BNL, January 10th, 2008 5

Membrane Dynamics

H.Heller, München, Germany

Study structure and dynamics on a molecular scale

Maikel Rheinstädter, XPCS NSLS II Workshop, BNL, January 10th, 2008 6

“Broadband” Neutron Spectroscopy

Inelastic neutron scattering gives wave vector resolved access to

dynamics

Spin-Echo (IN11/IN15)

10-2 10-1 100 10110-5

10-4

10-3

10-2

10-1

100

101

102

Q (Å-1)

E (m

eV)

102 101 100

106

105

104

103

102

101

100

10-1

R (Å)

t (p

s)

Triple-Axis (IN12/IN8)

Backscattering IN10/IN16

Time-of-Flight (IN5)

Spin-Echo (IN11/IN15)

10-2 10-1 100 10110-5

10-4

10-3

10-2

10-1

100

101

102

Q (Å-1)

E (m

eV)

102 101 100

106

105

104

103

102

101

100

10-1

R (Å)

t (p

s)

Triple-Axis (IN12/IN8)

Backscattering IN10/IN16

Time-of-Flight (IN5)

excitationsrelaxations

specific motions

Maikel Rheinstädter, XPCS NSLS II Workshop, BNL, January 10th, 2008 7

Elementaryexcitations

Mesoscopic Membrane Fluctuations

Propagating Oscillating Relaxating

Mode

+ +

Thermal membrane fluctuations

q-dependence of excitation frequencies

and relaxation rates

100 Å

Dispersion relation

Contains ‘dynamic’ information

τ-1

(ns-

1 )

q (Å-1)

60 Å

‘Phonons in membranes’

Maikel Rheinstädter, XPCS NSLS II Workshop, BNL, January 10th, 2008 8

Membrane Dynamics

Local modes in bilayers

Correlated molecular motions might be responsible for ‘functionalities’ of the membrane and structural changes

• Incoherent inelastic neutron scattering

• NMR

• Dielectric spectroscopy

• Coherent in- and quasielastic neutron scattering

• Inelastic X-ray scattering

• Dynamic Light Scattering (PCS)

• XPCS

Collective excitations

Maikel Rheinstädter, XPCS NSLS II Workshop, BNL, January 10th, 2008 9

Collective Excitations in model membranes

Relaxation

2Å<2π/q║<5000Å & 1ps<τ<1μs

DMPC –d54

PropagationOscillation&Relaxation

The ‘Neutron Window’

Backscattering-Spectrometer

Neutron-Spin-Echo-Spectrometer

Triple-Axis-Spectrometer

q||

Maikel Rheinstädter, XPCS NSLS II Workshop, BNL, January 10th, 2008 10

Stacked Planar Membranes

Sample Preparation

Solid supported, highly oriented

membrane stacks

several 1000 bilayers per Si-wafer,

mosaicity ~ 0.5°

„Sandwich-sample“with 500 mg

of deuterated DMPC

“Humidity Chamber”

Maikel Rheinstädter, XPCS NSLS II Workshop, BNL, January 10th, 2008 11

Scattering from aligned phases

qzqr

Highly orientedsolid supported

membranes

Isotropic solution“powder”

Si-wafer

Maikel Rheinstädter, XPCS NSLS II Workshop, BNL, January 10th, 2008 12

Membrane Permeability and Stiffness

Understanding and Controlling the Microscopic and Mesoscopic Properties of Membranes

Membrane Permeability

Ethanol

Membrane Elasticity

Cholesterol

Short wavelength dynamicsLong wavelength dynamics

Maikel Rheinstädter, XPCS NSLS II Workshop, BNL, January 10th, 2008 13

Membrane Permeability

Neutron Three-Axes to measure the short wavelength fluctuations

Rheinstädter, Ollinger, Fragneto, Demmel, Salditt, PRL 93, 108107 (2004).

Maikel Rheinstädter, XPCS NSLS II Workshop, BNL, January 10th, 2008 14

Dispersion relation as found in ideal liquids as liquid argon or liquid helium

→ Acyl-Chains behave “Quasi Liquid”

Short-Range Dispersion Relation on TAS

2π/Q0 defines quasi „Brillouin-zone“

Directed transport?

|Q0|

Low-Q range difficult to access for neutrons

(and X-rays)

Single points in S(Q,ω) no quantitative theory

Rheinstädter et al., PRL (2004)

gel

fluid

Maikel Rheinstädter, XPCS NSLS II Workshop, BNL, January 10th, 2008 15

Effect of Drug Enhancers: DMPC/Ethanol

Drug Enhancer: Facilitates the transport of molecules through the membrane

Ethanol(polar)

DMPC

polar head group

MD Simulation

DMPC/5% EthanolDMPC

Enhanced Chain Fluctuations: Phonon Assisted Diffusion

Maikel Rheinstädter, XPCS NSLS II Workshop, BNL, January 10th, 2008 16

Membrane Elasticity

Neutron Spin-Echo to measure long wavelength undulations

Rheinstädter, Häussler, Salditt, PRL 97, 048103 (2006)Schäfer, Salditt, Rheinstädter, PRE, in press.

Maikel Rheinstädter, XPCS NSLS II Workshop, BNL, January 10th, 2008 17

Membrane Elasticity

[ ]3/ mJd

dB ⎟⎠⎞

⎜⎝⎛

∂Π∂−=[ ]mJ

dK /⎟

⎠⎞

⎜⎝⎛= κ

∫ ⎪⎭

⎪⎬⎫

⎪⎩

⎪⎨⎧

∇+⎥⎦⎤

⎢⎣⎡

∂∂= 22

2

][ uKzuBdVH

Mesoscopic membrane fluctuations

Bending modulus Compressional modulus

eVns

μ114.41 =timescales

Maikel Rheinstädter, XPCS NSLS II Workshop, BNL, January 10th, 2008 18

Romanov and Ul’yanov, PRE 66, 061701 (2002)

Undulations

Si-wafer

Dynamics of solid supported bilayers

Undulation Dispersion Relations

Surface mode ?

Bary-Soroker and Diamant, Europhys. Lett., 73, 871 (2006), March 15, 2006

Relaxation

filmbulk-elasticity

κ=14.5 kBTη3=0.016 Paּs

Λ=10.3 ÅB=1.08 107 J/m3

Fit to smectic hydrodynamic theoryRibotta, PRL 32, 6, (1974).

2

3

4||

24||2

||3

||1

)(1))/((/)(

Dq

Dqqdq

πμη

πη

κτ+

Λ+=−

ρη3

3ηB

3ηκ

Softening close to Tc

Maikel Rheinstädter, XPCS NSLS II Workshop, BNL, January 10th, 2008 19

DMPC/40%Cholesterol

Effect of Cholesterol

<5% 40%MD simulations, Heller et al.

non polar ‘stiffens’

DMPC

mesoscopic

microscopic

suppressed

Quantify dynamics on different length scales

Maikel Rheinstädter, XPCS NSLS II Workshop, BNL, January 10th, 2008 20

Hard- and Soft-Matter

BiophysicsBiology

Soft-Matter

missing or not well developed structure

(BZ concept)

‘multi-scale’: relevant dynamics in a large

range of length and time scales

high ‘intrinsic’background because of mix

of coherent an incoherent scattering and diffusion

‘membrane spectroscopy’:

• combine instruments and techniques to maximize length and time scales

• overlap between instruments

• optimize instruments (divergences, resolution)

versatile instruments:

Flux is not everything:

• tunable q-ω resolution

• tunable divergences/collimation

Maikel Rheinstädter, XPCS NSLS II Workshop, BNL, January 10th, 2008 21

Membrane Spectroscopy

DLS XPCS

Maikel Rheinstädter, XPCS NSLS II Workshop, BNL, January 10th, 2008 22

ALV Dynamic Light Scattering System

ALV Compact Goniometer System, ALV/LSE-5004 Multiple Tau Digital Real Time Correlator, and Cuvette Rotation Unit

Laser

Optics

Intensity Monitor

Photon Counter

Fiber Optic

2q Arm

Beam Shutter

Sample Cell

Correlator & PC

PCS of Oriented Membranes

LaserCorrelator

Solid Supported

Freestanding

Maikel Rheinstädter, XPCS NSLS II Workshop, BNL, January 10th, 2008 23

Dynamic Light Scattering – Scattering Geometry

Incident Laser Beam

Detector PositionSpecular Reflection

Membrane Sample

Inelastically Scattered Laser Light

2q Scan in Reciprocal Space

Maikel Rheinstädter, XPCS NSLS II Workshop, BNL, January 10th, 2008 24

Dynamic Light Scattering – Data & Analysis

DampedMode.avi

Free standing ‘painted’ membraneDamped Propagating Mode

Relaxating Mode

time

time

exponential

energy

+ω0−ω0

τ

q||=0.003 Å-1

energy

Lorentzian

Δω=2π/τ

Maikel Rheinstädter, XPCS NSLS II Workshop, BNL, January 10th, 2008 25

Protein Dynamics

Bacteriorhodopsin in Purple Membrane

0 0.2 0.4 0.6 0.8

103

104

qr (Å−1)

neut

ron

coun

ts

(1,0

)

(1,1

)(2

,0)

(2,1

)(3

,0)

(2,2

) (3,1

)

(4,0

)(3

,2) (4,1

)

(5,0

)

0.35 0.4 0.45

400

500

600 (3,0

)

(2,2

)

(3,1

)

(4,0

)

Acoustic phonon spectrum

47Å

Data+Theory

Sample: Dieter Oesterhelt, MPI Munich

Challenge: Study Dynamics of Proteins embedded in Membranes0.35 0.4 0.45

0

0.2

0.4

0.6

0.8

1

qr (Å−1)

ω (

meV

)

(3,0

)

(2,2

)

(3,1

)

(4,0

)

Karin Schmalzl, Dieter Strauch,ILL+U Regensburg

Maikel Rheinstädter, XPCS NSLS II Workshop, BNL, January 10th, 2008 26

Thanks to

• Tim Salditt, Institut für Röntgenphysik• Wolfgang Häußler, FRMII, TUM• Christoph Ollinger, IRP• Giovanna Fragneto, ILL, D17• Wolfgang Schmidt, FZ-Jülich, IN12• Franz Demmel, ILL, IN3• Arno Hiess, ILL, IN8• Tilo Seydel, IN10/IN16• Fanni Juranyi, FOCUS, PSI• Klaus Habicht, HMI• Klaus Kiefer, HMI• Thomas Hauss, HMI• Dieter Richter, FZ-Jülich• Dieter Strauch, Regensburg• Karin Schmalzl, FZ-Jülich• Dieter Oesterhelt, MPI for Biochemistry

• Institut Laue-Langevin • DFG, Grant SA 772/8-2