In article <Pine.SGI.3.91.950126174410.2174A-100000 at helix.nih.gov>, Mohan Srinivasan <smohan at helix.nih.gov> writes:
|>|> Hi All-
|>|> Can proteins fold in a different way in the absence of
|> gravity ? I believe that their density changes (compacts) when
|> spun in ultracentrifuges at high rpm's (high G). So, the reverse
|> (low G) should be also true. Gravity is one of the forces apart
|> from the nuclear forces. Does folding depend only on nuclear
|> forces ? I am not sure though. Was any study made in this direction
|> during space experiments ? Could anyone throw some light ?
|>|> Mohan Srinivasan Ph.D | email: smohan at helix.nih.gov|> DCBDC/NCI/Bldg 37 Rm 2B10,NIH,9000 Rockville Pike| phone: 301 496 2202
|> Bethesda, MD 20892, USA | fax : 301 402 1031
|>|>|>
Just to add yet another NIH voice to this--
The magnitude of gravitational forces is extremely small compared to
the magnitude of electrostatic forces. That's why a kitchen magnet
can hold a note to the fridge with the entire gravitational force
of the Earth pulling against it.
Of course, electrostatics (salt bridges, Hbonds, vdW, etc.) do not
determine folding by themselves--entropic considerations are nearly
equal. The free energy of stabilization of most folded proteins'
structure is typically 20 kcal/mol at 25C, but the aggregate size of
the electrostatic forces holding the folded structure together is
on the order of thousands of kcal/mol. Entropy nearly balances
electrostatics.
And yes, some protein crystals have been grown on the Shuttle,
but they're usually so fragile that they're unusable.
--
_____________
| ___/_
| |/ /
-- /\ // /--
|| || / /||
|| || / / ||
|| ||/ / ||
John Kuszewski || |/ /| ||
johnk at spasm.niddk.nih.gov || / /|| ||
\/ / / || \/
that's MISTER protein G to you! |/__/| |
/_________|
