[RASMB] hydrodynamic radius

[John Correia]

Does HYDROPRO include the hydration sphere?  Wait that's 34.3 nm vs 27.1
nm?  I presume these are equivalent spherical radii but this might
require an very irregular shape to carry that much extra water?  .  We
have seen apparent changes in x-ray structure vs ultra results
consistent with "compaction" of the crystal relative to solution?  See
our smad work in Biochemistry for a ref : J.J. CORREIA, B.M. Chacko,
S.S. Lam and K. Lin. (2001)  "Sedimentation Studies Reveal a Direct Role
of Phosphorylation in Smad3:Smad4 Homo- and Hetero-Trimerization."
Biochemistry, 40, 1473-1482.  The question is are solvent effects or
desolvation effects due to crystallization conditions "conformational
changes" in a functional sense?




-------------------------------------------------------------------
 Dr. John J. "Jack" Correia
 Department of Biochemistry
 University of Mississippi Medical Center
 2500 North State Street
 Jackson, MS  39216
 (601) 984-1522                                 
 fax (601) 984-1501                             
 email address: jcorreia at biochem.umsmed.edu     
 homepage location: http://biochemistry.umc.edu/correia.html  
 dept homepage location:    http://biochemistry.umc.edu
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>>> "Karthe P." <karthe at onyx.cbse.uab.edu> 07/11/02 02:35PM >>>
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Hello RASMBers:

I am a crystallographer and dont have experience with the techniques of

biophysical charaterisation of proteins.

We recently solved one crystal structure and we think there is a
significant
conformational change in the protein structure in a solution state and
in a 
crystalline state.

So we did ultercentrifugation and obtained the hydrodynamic radius
which 
is 3.4271 E-07 cm.  Then using protein coordinates we calculated
hydrodynamic 
radius (with the program HYDROPRO) which is   2.709E-07 cm.

My question is, can I say the conformation of the molecule in solution
is
different from the crystalline state.

Thanks
Karthe

-- 
******************************************************
P. Karthe Ph.D
Center of Biophysical sciences & Engineering
1025 18th Street South
University of Alabama at Birmingham
Birmingham, AL 35294, USA  

email: karthe at onyx.cbse.uab.edu 
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