[RASMB] Sedimentation of rods

[Walter Stafford]

Hi All,
	I have had a lot of experience with rods (alpha-helical, coiled-coils) ranging from tropomyosin (2.7S, M=70,000) to light meromyosin (LMM, molar mass 150,000) to myosin rod and paramyosin molar mass (110,000) : all of different lengths. Paramyosin and myosin rod are the logest 126.0 nm and 180 nm respectively and they have sedimentation coefficients on the order of 3.01S. John is correct. The increase in mass  is compensated for by the increase in frictional coefficient so that sedimentation coefficient does not vary much with molar mass. This true for any series of rods of constant diameter, but s will depend on the diameter.
_________________________
Walter Stafford
wstafford3 at walterstafford.com



On May 8, 2014, at 11:41, Laue, Thomas wrote:

> Hi all-
> We are looking at a protein that forms rods. I have little background on systems like this, and am looking for some guidance. In particular, my recollection is that for long rods, as the rod length increases, the s collapses back to a constant ~2.7 s. 
> Any wisdom will be welcome.
> Best wishes,
> Tom
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