FURTHER STUDIES OF MOLECULAR WEIGHT IN AQUEOUS SOLUTION OF LOW-SULFUR WOOL-PROTEIN-COMPONENT-8 AND A REINTERPRETATION OF PREVIOUS RESULTS

In a previous sedimentation equilibrium study in 0.01 m sodium tetraborate it was found that at lowconcentration the measured molecular weight of the reduced and alkylated low-sulfur wool protein, component 8, increased with increasing protein concentration. The variation of molecular weight was satisfactorily explained as the consequence of a rapid reversible equilibrium between a monomer of mol wt 23,000, dimer, and trimer. The present paper gives the results of frontal analysis gel filtration on Sephadex G-200 and osmotic pressure experiments which show that component 8 is almost certainly not involved in such an equilibrium in 0.01 m sodium borate. These results together with those from more high-speed sedimentation equilibrium experiments and the use of two-species plots indicate that the component 8 used in these studies is a mixture of more than 95% of a protein ofmol wt 45,000 and less than 5% of one of mol wt 14,000. Calculations using these figures show that the results of the highspeed sedimentation equilibrium experiments can indeed be explained on this basis and it is concluded that the molecular weight of component 8 is 45,000. © 1969, American Chemical Society. All rights reserved.