Abstract: The molecular weight of silk fibroin in 0.1 M KNO3 solution has been determined at various protein concentrations and pH values by the Archibald method. The values calculated from the top meniscus decreased with time, reaching a limiting value of 16000 ± 2000. In sedimentation-velocity experiments, a single peak was observed at all protein concentrations and pH values studied. The sedimentation coefficient at infinite dilution had a value of 1.36 S and did not vary with pH. From 1.36 S, an approximate molecular weight of 21000 is calculated. Since this is close to the limiting value of 16000 it is concluded that the fibroin preparation consists mainly of this component. It has been shown that the change of molecular weight with time was due to the presence of a high-molecular-weight impurity. This fraction was concentrated by preparative centrifugation at 35000 rev./min. It had a sedimentation coefficient of 22.3 S approximating to a molecular weight of 1.2·106. Ultracentrifuge field-relaxation experiments also indicated the presence of heterogeneity and further suggested that the preparation contained essentially only two species, of molecular weight 16000 and about 1.2·106, without any intermediates.
Publication Year: 1965
Publication Date: 1965-01-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 14
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