小米蛋白质的理化特性研究

Physicochemical properties of foxtail millet protein

小米蛋白质主要以蛋白体的形式存在，直径在1～1．5μm之间；蛋白体位于淀粉粒之间的间隙或“镶嵌”于淀粉粒之间。小米蛋白质中清蛋白和球蛋白含量很少，其中质量分数45．6％为醇溶蛋白，质量分数21．1％为碱溶蛋白，剩余的蛋白质要用质量分数1％十二烷基磺酸钠（SDS）或质量分数1％SDS＋体积分数2％2一巯基乙醇（2-ME）才能提取出来。还原条件下的聚丙烯酰氨凝胶电泳图（SDS-PAGE）显示：清蛋白和球蛋白都有多条谱带，清蛋白的谱带主要集中在高分子量范围内，而球蛋白的主要集中在低分子量范围内，47．2、32．9、22．7、11．0kD谱带明显；醇溶蛋白在21．7kD谱带明显；碱溶蛋白在高分子量和低分子量范围内都有谱带；质量分数1％SDS、质量分数1％SDS＋体积分数2％2-ME提取的蛋白质的谱带在高分子量范围内与碱溶蛋白的相似，在低分子量范围内与醇溶蛋白的相似，但13．0kD谱带特别明显；小米淀粉粒内部含分子量为60kD的淀粉粒蛋白。

Foxtail millet protein exists mostly as protein body, which has a diameter of 1～1.5μm. The protein bodies are located or inserted among starch granules. The albumin and globulin are very limited in foxtail millet protein, of which 45.6 % （w/w）is alcohol-soluble and 21.1% （w/w） is alkaline-soluble. The residue protein can be extracted only by 1 % （w/w） SDS or 10%（w/w） SDS＋2%（v/v） 2-ME solution. SDS-PAGE at reduced conditions revealed that both albumin and globulin contain many bands. The bands of albumin appears mainly in high molecular domain, while these of globulin in low molecular domain, and bands of 47. 2,32, 9,22. 7,11.0 kD were prominent, The alcohol-soluble protein contains molecular weight of 21.7 kD as major polypeptide components. The bands of alkaline-soluble protein appears in both high and low molecular do mains. The protein extracted by 1%（w/w） SDS and 1% （w/w）SDS--2%（v/v）2-ME, which contained a band of 13.0 kD as major band, have a similar SDS-PAGE profile as that of alkaline-soluble protein in high molecular domain and as that of alcohol- / soluble protein in low molecular domain. The starch granule associated protein of 60 kD existed in the inner part of foxtail rail let starch granules.