Figure 1. Gel electrophoresis (SDS–PAGE; silver stained) analysis of the purified four-module containing Xenopus interphotoreceptor retinol-binding protein. The major band corresponds to monomeric Xenopus interphotoreceptor retinol-binding protein (xIRBP) molecular weight of 131 kDa. The minor higher molecular weight band represents dimeric form of the protein, which may or may not be an artifact of the analysis itself.