The alpha 1(I) and alpha 2(I) chains of collagen separate in sodium dodecyl sulfate-polyacrylamide gel electrophoresis due to differences in sodium dodecyl sulfate binding capacities.

The alpha 1(I) and alpha 2(I) chains of rat tail collagen, indistinguishable with respect to their chain lengths, are well separated in polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS). In the present study, the results demonstrated: 1) the alpha 2 chain maximally binds SDS in an amount of 1.6 g/g which is significantly larger than 1.4 g/g found for the alpha 1 chain; 2) the alpha 2 chain acquires electrophoretic mobility in a free solution 14% higher than that of the alpha 1 chain as the result of the larger amount of SDS bound; 3) although both of the chains have virtually the same hydrodynamically effective size, the above difference in mobility persists in a gel, and brings about the separation in a high resolution. It was also found that the alpha 2 chain binds appreciable amounts of SDS in the initial phase of the binding where the alpha 1 chain hardly binds SDS.