X-ray Crystallography

Index-History-x-ray-Introduction-Instrumentation x-ray source monochromatic calorimeter Goniometry photographic plat film detector-Principal-Working-Application-Reference

Historyx-ray crystallography was discovered by Johns kaplae in 17th century.

X rayAn electromagnetic wave of high energy and very short wavelength (between ultraviolet light and gamma ray).which is able to pass through many materials opaque to light.

Introduction

1. X-ray is the study of any crystalline structure of bio molecules using x-ray.2.s It is widely use in biological science for studying structure of biological molecule such as protein, antibiotics, fats, DNA, RNA.

Properties

1.X-ray travel in straight lines.2.x-ray are electrically neutral.3.x-ray are polynergetic and heterogonous.4.x-ray are invisible ray.

Instruments

The instrument used in x-ray crystallography is know as x-ray diffractometer and content following part:1. X-ray source2. Monochromater3. Calorimeter4. Goneometer5. Photographic plate film6. Detector

X-ray source

the x-ray most common source of x-ray is an x-ray tube . The tube is evacuated and contains a copper block with a metal target anode, and a tungsten filament cathode with a high voltage between them.

Monochromater

It act as x-ray filter which remove unwanted rays, generally12-24 am- strong ray has been in x-ray.The name is form the Greek roots mono-” single", and chroma-”colour”.

Collimator

This comprises of 2 closely packed metal plate which are 0.3mm apart from each other. The x-ray beam originate from x-ray source passes through this gap and follow single line path.

Goniometry

It is device on which crystal whose structure is to be determine has been mounted.This device spin slowly in according to crystal which to rotate on constant speed.This place between collimator and photo plate.

Photo plate film As the name suggest this plate capture the diffraction rays of crystal.The light-sensitive emulsion of silver salts was coated on a glass plate ,typically thinner than common window glass ,instead of a clear plastic film .

Detector

The captured data has been send to computer for further processing by detector where 3D structure of crystal gets develop.

Principle

The principle is based on principle of diffraction1. The crystal is made to strike against x-ray beam.2. Due to striking the atoms present in crystal diffracts the x-ray beam into different direction.3. The angel and intensity of this diffraction rays is analog to spatial arrangement of atom in crystal.4. By studying these angle, the 3D structure of any crystal can be determine. 5.X-rays are generated by bombarding electrons on an metallic anode.

Working

Protein Sample for Crystallization:

Pure and homogenous (identified by SDS-PAGE, Mass Spec. etc.)Properly folded Stable for at least few days in its crystallization condition (dynamic light scattering) Conditions Effect Crystallization - pH (buffer)

- Protein Concentration- Salt (Sodium Chloride, Ammonium Chloride etc.)- Precipitant- Detergent - Temperature- Size and shape of the drops- Pressure

Application

1. The various atomic arrangement present in graphite diamond can be study using x-ray diffraction.2. the lattice structure of crystal can be revealed using x-ray diffraction 3. protein, antibody, DNA, RNA, lipids and other bio molecules structure can be study4. bond such as covalent bonds and ionic that exist between molecule can be study.5. the molecular structure of penicillin, vitamin B12, insulin etc can be determine using x-ray diffraction.

Reference Avinash Upadhyay, Himalaya publishing house,

Biophysical Chemistry, Fourth edition, chapter 11, , pg no. 523-535.

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