Transcript What are we studying in the EPR lab?

Precession Method used in Orientation for Single
Crystals of L-lys HCl 2H2O and L-arg HCl H2O
Yiying Zhou
Department of Physics and Astronomy
Georgia State University
Outline
• What are we study in EPR lab ?
• Why choose lysine and arginine?
• Precession method used in orienting the
crystal of l-lys Hcl 2H2O and l-arg Hcl H2O
What are we studying in
the EPR lab?
1) How to detect the free radicals?
• EPR technique is the only analytical technique to measure
free radical
2) Why use single crystals?
• Single crystals permits taking full advantage of the ESR
technique for purposes of radical identification .
• The structure information about the molecules and their
surroundings can be provided by Crystallography
Molecular Structure of L- arg HCl H2O
Unit cell parameters
a = 11.044Å
b = 8.481Å
c = 11.214 Å
ß = 91.31
Monoclinic labeling to space group of
P21 and there are two molecules in
each unit cell.
Molecular Structure of L- lys HCl 2H2O
Unit cell parameters:
a = 11.044Å
b = 8.481Å
c = 11.214 Å
ß = 91.31
Monoclinic labeling to space group of P21
and there are two molecules in each unit
cell.
Distribution of Hydrogen bonds according to the participating amino acids
and DNA base or backbone group
It is important to properly locate and
assign the axis of crystal
• The systems of crystal are anisotropic and thus the
magnitude of hyperfine coupling constants, the important
magnetic parameters to assign the free radicals, depend
strongly on orientation in external magnetic field.
• In order to calculate the hyperfine coupling constants
(which are generally described by eigenvalues and eigenvectors or
tensor) from ENDOR data, it is necessary to take ESR and
ENDOR data at lease at two different crystal lattice planes,
which means rotate the crystal with two certain different
axes and scan the external magnetic field in the plane
perpendicular to the rotation axis respectively.
Principle of Precession Method:
• 1) Bragg law:
• 2) Ewald Construction
N  = 2d sin 
OP = 1/d410 = (2/ )  sin 
3) Precession method
Photos of layer screen and Cirle
Circle
Layer screen
Sin  =
t/2
F

t=Fd
hkl
(1)
(2)
Procession Camera
F = 60 mm
 = 0.7107Å
Diffraction Pattern for single crystal of
l-lys Hcl 2H2O
(1)
(2)
(3)
Diffraction pattern for Single crystal of
l- arg HCl H2O
(1)
(2)
(3)
Table 1 Parameter of Unit Cell
Table 2 Spacing of Diffaction Pattern
l-lys Hcl
2H2O
d3 = t3 / (60mm 
0.7107 Å)
(Å-1)
d32
(Å-1)2
d32 = (ha*)2 + (kb*)2
+ (lc*)2
(Å-1)2
Layer 1
0.1540
0.0237
0.0238 (110)*
Layer 2
0.1554
0.0241
0.0238 (110)*
Layer3
0.2286
0.0523
0.0523 (021)*
d32
(Å-1)2
d32 = (ha*)2 + (kb*)2
+ (lc*)2
(Å-1)2
l-argHCl
H2O
d3 = t3 / (60mm 
0.7107 Å)
(Å-1)
Layer1
0.1498
0.0224
0.0222(110)*
Layer2
0.1485
0.0220
0.0218(011)*
Layer3
0.1488
0.0221
0.0218(011)*
Table 3.Comparison of Results of line3
Crystal transferring
Reference
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1) Luscombe, N, M.; Roman, A.L; Nucleic Acids Research, 2001, 29,
2860
2) Dow, J; Jeansen, L. H.; Acta Cryst., 1970, B26, 1662
3) R.R. Bugayong; A. Sequeira; Acta Cryst., 1972, B28, 3214
4) A. Ducruix; R. Giege; Crystallization of Nucleic Acids and
Proteins; 1992 Oxford University Press.
5) Martin J. Buerger; The Procession Method in x-ray crystallograph;
John Wiley and Sons, Inc
6) John A. Weil; James R. Bolton; Electron Paramagnetic Resonance;
1994 John Wiley & Sons, Inc.
Thanks