Thomsen J K, Jakobsen H J, Nielsen N C, Petersen T E, Rasmussen L K
Department of Chemistry, University of Aarhus, Denmark.
Eur J Biochem. 1995 Jun 1;230(2):454-9. doi: 10.1111/j.1432-1033.1995.tb20582.x.
Solid-state magic-angle spinning 31P-NMR spectroscopy was used to characterize the structure and composition of native casein micelles. The features of the magic-angle spinning 31P-NMR spectra, including overlapping resonances from mobile/immobile phosphorylated serine residues and inorganic calcium phosphates, have been determined using different experimental techniques and assigned by comparison with spectra of the presumed constituents within the casein micelle. Comparison with 31P-NMR spectra of alpha s1-, alpha s2-, and beta-caseins in dissolved and freeze-dried forms demonstrated that a major fraction of the phosphoserines in these proteins was in an immobilized state within the micelle. Likewise, from 31P-NMR spectra of the C-terminal part of kappa-casein, it was shown that this region of the micelle has a considerable conformational mobility. Finally, magic-angle spinning 31P-NMR spectra for a series of inorganic calcium phosphates and mineralized bone tissue revealed that the micellar inorganic calcium phosphates exhibit structural similarities to hydroxyapatite and hence resemble mineralized bone tissue.
固态魔角旋转31P核磁共振光谱用于表征天然酪蛋白胶粒的结构和组成。利用不同的实验技术确定了魔角旋转31P核磁共振光谱的特征，包括来自可移动/不可移动磷酸化丝氨酸残基和无机磷酸钙的重叠共振，并通过与酪蛋白胶粒内假定成分的光谱进行比较来进行归属。与溶解和冻干形式的αs1-、αs2-和β-酪蛋白的31P核磁共振光谱比较表明，这些蛋白质中的大部分磷酸丝氨酸在胶粒内处于固定状态。同样，从κ-酪蛋白C末端部分的31P核磁共振光谱可知，胶粒的该区域具有相当大的构象流动性。最后，一系列无机磷酸钙和矿化骨组织的魔角旋转31P核磁共振光谱表明，胶粒无机磷酸钙与羟基磷灰石具有结构相似性，因此类似于矿化骨组织。
