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gjacobs at chmeds.ac.nz gjacobs at chmeds.ac.nz
Mon Jan 30 16:25:52 EST 1995

(just in fun - this is not really my topic!)

In article <1995Jan27.024118.3087 at alw.nih.gov>, rvenable at deimos.cber.nih.gov (Rick Venable) writes:
> On Thu, 26 Jan 1995 22:53:19 GMT Mohan Srinivasan pontificated:
>> 	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 ?
> I'd say that there is little or no difference.  First, the difference
> between 0 G and 1 G is very small, compared to the high G force in a
> modern ultracentrifuge.  Second, perhaps many astronauts would be dead if
> the change from 1 G to 0 G seriously altered protein folding.  

Nicely put.

> Third, most
> theoretical chemistry programs (molecular dynamics, quantum calculations,
> etc.) ignore gravity completely.  Not that the absence is proof, but many
> leading scientists studying protein folding from a theoretical approach do
> not consider gravity.  After all, the mass of a protein is infintesimal
> compared to the mass of the Earth, and it exists in a buoyant medium.

Just another thought - do proteins care "which way up" they are while they
are folding - I doubt it! (a grativational effect implies a directional


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