摘要
聚谷氨酸(PGA)和聚谷氨酸钠(PGA-Na)在不同的相对湿度(R H)下,用红外光谱仪测得它们的结构和侧链非离子化羧基的变化.固态PGA-Na(平均分子量[MW]8000),在50%R H以下能保持无规卷曲结构,在50—70%R H之间为β-折叠,70%R H以上为x-螺旋.以二氧六环:水二1.5:1(V/V)的混合液作为溶剂的PGA(MW8000)溶液,涂为膜后,在各种相对湿度下保持α-结构,但侧链非离子化羧基有变化,而且这种变化是可逆的.当PGA分散在水中成悬浮液后涂成的膜,在很宽的相对湿度范围内,保持α-螺旋不变,直至96%R H.才出现β-折叠,而且是不可逆的.
The changes which occurred in both non -ionic sidechains and structure of Pol-y-glutamic acid (PGA, MW 80000) and Sodium Poly-glutamate (PGA-Na, Sigma MW 80000) have been studied by infrared spectroscopy under various relative humidities ( R. H. ). For films of PGA - Na, if remains random coil structure less than 50% R. H.. It becomes β- sheet from 50% to 70% R. H. and α-helix greater than 70% R. H. The films which cast from a solution of the PGA in dioxane-water mixture (1.5: 1 by volume) remain α-helix at different relative humidities, but changes of non - ionized carboxyl in the side chain of PGA have been observed and are reversible. The films which cast from a suspension of the PGA in water remain α -helix at the range of wide relative humidities. Its β- sheet is only observed when the relative humidity is raised up to 96%, but no reversible α -β interconversion has been obtained
出处
《生物物理学报》
CAS
CSCD
北大核心
1990年第4期453-457,共5页
Acta Biophysica Sinica
基金
国家自然科学基金资助课题
