Biological Applications of Crystallography

Joseph D. Ng

University of Alabama in HuntsvilleMay 24, 2014

www.uah.edu/nglab

Crystallography is NOT……

34Å

y

x

h

sin = y/h

cos = x/h

tan = y/x

Bragg’s Law

All you need to know…for now

tan-1(y/x)

72o

2.8mm

y

x

h

tan-1(y/x) = 3.2

X-ray

Film

x

x=50mm

y=2.8mm

Bragg’s Law

d= 27.5Å

Let’s calculate Pitch

cos = x/h cos = d/P P=d/cos

P= 34Å

72o

2.8mm

y=Rsiny=Rsin(x/P)

dy/dx=Rcos(x/P)/P

So when x=0

dy/dx = R/P

dy/dx =Rcos()/P

X=0Tan (90o-)= R/P

Let’s calculate Radius!

X=0

R = 10Å

34Å

Hydrogen-bonding patters in the base pairs defined by Watson and Crick

Sample of Crystals Obtained

Advanced Photon Source Argonne National Lab

2.0 Å