alignment in a magnetic field
 

hi all,

I have a general question about alignment in a magnetic field.
For me, alignment in alignment media is easier to grasp because of interactions that I am familiar with as a chemist.

But, whats the principle behind molecules that align in a magnetic field?
There are a lot of examples like cyanometmyoglobin (from the Prestegard paper) where paramagnetic susceptibility plays a role. Thats understandable from my side.
But what about for instance short DNA dimers (helices), collagen gels or bacteriophages?
I could not really find a nice (clear to me) explanation, why these molecules align...

Does anyone of you knows more about it?
thanx a lot!
Hydrazin

Elongated molecules like DNA helices, bacteriophage etc. have intrinsic large magnetic susceptibility anisotropies which aligns them in magnetic fields (similar to magnetic dipoles). Check out papers from the 80s by A. A. Bothner-By for more details.