Study for elucidating the mechanism for the specific degradation of spider silk by ultraviolet rays

先前，Osaki等人发现Nephila clavata蜘蛛的蚕丝比家蚕（Bombyx mori）的蚕丝更耐紫外线照射。在本研究中，我们着重从分子量的角度研究了蚕丝和蜘蛛丝的紫外线电阻率差异。通常，用十二烷基硫酸钠（SDS PAGE）使蛋白质变性后，用凝胶电泳法测定分子量。通过SDS PAGE分析，蜘蛛丝蛋白的分子量为272 kDa，小于家蚕蛋白的分子量（350 kDa）。我们试图改变蜘蛛丝变性的方法，以实现自然状态。测定了天然蜘蛛丝蛋白的分子量约为600 ~ 700 kDa，比蚕丝大得多。如此大的分子量可能归因于分子量为272 kDa的蛋白质分子的交联。

Previously, Osaki et al. showed that the silk of the Nephila clavata spider was more resistant to UV irradiation than that of the Bombyx mori silkworm. In the present study, we focused on the difference in UV resistivity between silkworm silk and spider silk from the viewpoint of molecular weight. Generally, molecular weight is determined using gel-electrophoresis method after denaturing proteins by sodium dodecyl sulfate (SDS PAGE). Here, the molecular weight of spider silk protein was determined to be 272 kDa, which is smaller than that (350 kDa) of silkworm silk using SDS PAGE.We tried to change the method for denaturing spider silk to realize the native condition. The molecular weight of native spider silk protein was determined to be about 600-700 kDa, which was much larger than that of silkworm silk. Such a large molecular weight may be ascribed to cross-linkages of protein molecules with a molecular weight of 272 kDa.