Feb 28

Question 1

Refined model should have rms deviations of about ____ and ___ for bond lengths and bond angles respectively?

Answer 1

0.02 Angstroms for bond lengths
2 degrees for bond angles

Question 2

What is the R-factor for refinement? What is the R free value?

Answer 2

It is structure factor (obs-calc)/obs.

Rfree is when 10% of data (or at least 1000 reflections), is then used to monitor teh refinement

Question 3

What is anisotropic B value?

Answer 3

Isotropic is same in all directions, so anisotropic is not. There is different fall-off of diffraction in different directions

Question 4

What does Luzzati plot show?

Answer 4

It is R-factor on y axis, then 1/distance representing resolution on x axis. As R factor goes up, resolution value does too (indicating we have lower resolution). Lines show theroetical change in R factor

Question 5

What does zero occupancy atom mean?

Answer 5

It means that we know atom has to be there, but we don’t know what it is