X-ray diffractionBiophysics

W. K. Röntgen (1845 – 1923) Wife’s hand

Ruhmkorff inductor

X-ray tube with rotating anode

Syncrotron in Grenoble

X-ray spectrum of rhodium

qUh max

Λmin

K series

U

345.12min Å

(Duane – Hunt limit)

White radiation

Bremsstrahlung

Moseley-law

σ= 1 for K lines

σ= 7.4 for L lines

2)Z(

K

Diffractometer

Note: diffraction is a special geometry dependent spectroscopy

X-ray diffraction facility

= AD - BC

(2')

(2)

(1')

(1)

a

D

C

BA

Laue diagram

Condition for constructive interference:

k)cos(cosa 0

Δ = AD - BC

Incident beam

X

Z

Yα0 β0

γ0

Diffraction pattern of a crystal

X-ray pattern of whale myoglobin

Debye-Scherrer method

Bragg scattering condition

kλ= 2dsinδ

(3)

(2)

(1)

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Diffraction from 2-D lattice

Incident beamReflected beam

e1/P

m

Sources of secondary X rays

zero order 0

1

3

2

-1

-2

-3third order

P

Row of scatterers

1

1’

Note: If the number of scatterers increases the diffraction pattern becomes sharper

helix axis

equator

meridian

e1/P

m

Continuous helix

helix axis

equator

meridian

Diffraction pattern of continuous helix

12

3

1/P

P: pitch of helix

X-ray diffraction of helix structure

1/R

-1

+1

1/p

Generation of diffraction pattern

14.3 nm

Striated muscle

Relaxed state

Rigor state

Sarcoplasmatic reticulum

I4-1 supernova