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