NMR OF SILK FIBROIN .2. C-13 NMR-STUDY OF THE CHAIN DYNAMICS AND SOLUTION STRUCTURE OF BOMBYX-MORI SILK FIBROIN
NMR OF SILK FIBROIN .2. C-13 NMR-STUDY OF THE CHAIN DYNAMICS AND SOLUTION STRUCTURE OF BOMBYX-MORI SILK FIBROIN
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DOI：
10.1021/ma00135a017
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发表时间：
1984-01-01
期刊：
影响因子：
5.5
通讯作者：
MINAGAWA, H
中科院分区：
文献类型：
--
作者：
ASAKURA, T;WATANABE, Y;MINAGAWA, H
~（13）C NMR谱已被应用于B的链动力学。家蚕丝素蛋白溶液和保存在完整蚕的丝腺中的丝素蛋白。除了Gly残基的C“和C= 0峰以及Ala残基的C= 0峰之外，所有峰都是尖锐的：对于后面的这些峰观察到轻微的分裂，表明对丝纤蛋白的氨基酸序列的敏感性。13 C NMR谱测定的氨基酸组成与氨基酸分析测定的丝素蛋白的氨基酸组成非常接近，表明在13 C NMR谱中观察到丝素蛋白中的结晶和非结晶两种结构域。根据自旋-晶格弛豫时间和Ala、Gly和Ser C“碳原子的核Overhauser增强效应（假设log x2分布模型）确定的节段运动的平均相关时间在40 ℃时为10-10 s量级。此外，模型中的宽度参数p被确定为11-14，表明相关时间的广泛分布。这些是典型的无规卷曲聚合物。围绕C“-C”键的内旋转速率按Ala、Ser、Tyr的顺序降低。Tyr残基的侧链运动受到强烈阻碍，尽管Tyr OH去质子化的PKn值表明OH基团与丝纤蛋白的任何氨基酸残基之间不存在分子内或分子间氢键。随着浓度的增加，Tx值减少，节段运动的平均相关时间增加。这是讨论有关的外观的丝I型构象伴随的链的聚集。
13C NMR spectroscopy has been applied to the chain dynamics of B. mori silk fibroin in solution and the silk fibroin stored in the silk gland of the intact silkworm. All the peaks were sharp except for the C “and C= 0 peaks of the Gly residue and the C= 0 peak of the Ala residue: a slight splitting was observed for these latter peaks, indicating sensitivity to the aminoacid sequence of the silk fibroin. The aminoacid composition determined by 13C NMR spectroscopy was very close to that for silk fibroin determined from amino acid analysis, indicating that both domains, ie, crystalline and noncrystalline, in the fibrous protein were observed in thespectrum. The mean correlation times of the segmental motion, determined from the spin-lattice relaxation times and nuclear Overhauser enhancements of the Ala, Gly, and Ser C “carbons assuming a log x2 distribution model, were of the order of 10-10 s at 40 C. Moreover, the width parameter, p, in the model was determined to be 11-14, indicating a broad distribution of correlation times. These are typical of a random coil polymer. The rate of internal rotation around the C “-C^ bond decreases in the order Ala, Ser, Tyr. Theside-chain motion is strongly hindered for the Tyr residue although the pK „value for Tyr OH deprotonation indicates absence of intra-or intermolecular hydrogen bonding between the OH group and any amino acid residues of the silk fibroin. A decrease in the Tx values and an increase of the mean correlation times of the segmental motion were observed with increasing concentration. This is discussed in relation to the appearance of the silk I type conformation accompanying theaggregation of the chain.