采用石墨炉原子吸收光谱法（graphite furnace atomic absorption spectrometry，GFAAS）测定不同品种、不同加工精度大米及大米4种蛋白质中的镉含量。选用镉含量较高的大米为实验原料，采用Osborne分级法提取大米中的4种蛋白质（清蛋白、球蛋白、醇溶蛋白和谷蛋白），以及超滤、离子交换色谱从镉含量较高的大米蛋白中分离纯化出均一纯度的大米镉结合蛋白（rice Cd-binding protein，RCBP），十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（sodium dodecyl sulfate-polyacrylamide gel electrophoresis，SDS-PAGE）鉴定RCBP的纯度及测定分子质量。结果表明：籼米中镉含量高于糯米及粳米；随着加工精度的增加，同种大米中的镉含量依次降低。4种大米蛋白中的镉含量分别为0.66、0.31、0.63、0.23μg/g，清蛋白中镉含量最高。超滤分离大米清蛋白（rice albumin，RA）得到大米超滤清蛋白（rice ultrafiltration albumin，RUA），离子交换色谱纯化RUA得到目标镉结合蛋白（组分c）， SDS-PAGE鉴定组分c为单一条带，分子质量为14 kD。%A graphite furnace atomic absorption spectrometry (GFAAS) method was used to determine the cadmium content in rice grains from different varieties and at milling levels, as well as in four rice seed storage proteins (albumin, globulin, prolamin and glutelin) obtained through the Osborne sequential extraction method. Moreover, rice cadmium-binding protein (RCBP) was separated and purified to homogeneity by using ultrafiltration and ion exchange chromatography. The purity and molecular mass of RCBP were identified. The results showed that the cadmium content in indica rice was higher than that in glutinous rice and japonica rice and the cadmium content in rice decreased with the increase of milling level. The cadmium contents of rice albumin, globulin, prolamin, and glutelin were 0.66, 0.31, 0.63 and 0.23μg/g, respectively. RCBP (fraction c) with high purity and good homogeneity as well as molecular mass of 14 kD was prepared from rice albumin (RA).
展开▼
