Molecular weight averages from sedimentation equilibrium

Molecular weights of polysaccharides in solution can also be measured by osmotic pressure and light scattering. Osmotic pressure yields the number average molecular weight, which can be usefully used with Mw from sedimentation equilibrium as a measure of polydispersity Preston and Wik [28] have done this for example with hyaluronic acid. The ratio Mw/Mn the polydispersity index is often given as a measure of polydispersity, and can be related to the width of a molecular weight distribution via the well-known Herdan [96] relation ... 

Figure 3.15. The dissociation of /3-lactoglobulin B at low pH. Idealized curves for the weight-average molecular weight as a function of concentration from sedimentation equilibrium measurements. = pH 2.58, ionic strength 0.15 = pH 2.20, ionic strength 0.15 = pH 2.58, ionic strength 0.10. 40.2 fringes - 10 g/liter. (From Albright and Williams 1968. Reprinted with permission of AVI Publishing Co., Westport, Conn.)...

Average molecular weights were determined for the acetylated lignin samples from sedimentation equilibrium at different rotor speeds and positions in the cell... 

Fio. 14. Molecular weight data from high speed sedimentation equilibrium analysis of a-chains ( ) and the fragments of a ( ) and a ( ) resultii from dq don with an ensyme from tadpole. The arrows indicate the average values from several experiments. (Kang el al., 1966b.)... 

The molecular weight of the enzyme has remained remarkably constant from the bacteria to the higher mammals (Table VIII). The molecular weight from all species averages 36,500, and the deviations from this value fall within the experimental range of the methods used, in this case sedimentation equilibrium in the ultracentrifuge or electrophoresis of the SDS-enzyme-complexes on polyacrylamide gel. 

Munk has developed a new algorithm for the analysis of sedimentation equilibrium data from a single experiment to obtain the average molecular weight and its polydispersity, providing that the Schultz-Zimm distribution function and a certain thermodynamic behaviour can be assumed. Simultaneous curve fitting to the equilibrium sedimentation data for three different concentrations facilitated the discovery that filamin monomer and dimers are in equilibrium while the tetrane forms irreversibly. ... 

G(S), and crosslinking, G(X), from measurements of average molecular weights is extended by utilizing. It is useful to determine and simultaneously by sedimentation equilibrium in the ultracentrifuge. 

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