Solution Properties of Synthetic Polypeptides. XX. Light-Scattering Study of Poly-N5-(2-hydroxyethyl)L-glutamine in the Helix—Coil Transition Region
Solution Properties of Synthetic Polypeptides. XX. Light-Scattering Study of Poly-N5-(2-hydroxyethyl)L-glutamine in the Helix—Coil Transition Region
复制标题
聚-N5-(2-羟乙基)L-谷氨酰胺在螺旋-螺旋过渡区域的光散射研究。
DOI：
10.1295/polymj.8.281
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发表时间：
1970
期刊：
影响因子：
2.8
通讯作者：
H. Fujita
中科院分区：
文献类型：
--
作者：
Tomohisa Ohta;T. Norisuye;A. Teŕamoto;H. Fujita
通过光散射测量来跟踪聚-N5-(2-羟乙基)L-谷氨酰胺(PHEG)在2-丙醇的水性混合物中的螺旋-螺旋转变。对于所研究的两个样本中的每一个，均方根回转半径曲线<S2>1/2vs。螺旋分数 fN 呈现出较宽的最小值。这种行为与之前的旋光色散数据一致，表明 PHEG 的转变具有非常低的协同性。通过 Teramoto 等人的方法分析了 <S2> 的数据，得出随机卷曲部分的有效键长为 14.7A，每个单体残基的螺旋节距为 1.97A。后一个值与 α 螺旋预期的 1.5A 的差异归因于螺旋部分和相邻随机卷曲残基之间的短程相互作用。发现弗洛里粘度常数 Φ 在 fN 高达 0.9 的范围内几乎保持恒定（约 2×1021）。这一事实表明，对于转变的大部分，高分子量 PHEG 分子的平均形状是球对称的，如无规卷曲。
The helix—coil transition of poly-N5-(2-hydroxyethyl)L-glutamine (PHEG) in aqueous mixtures of 2-propanol was followed by means of light-scattering measurements. For each of the two samples investigated, the curve for the root-mean-square radius of gyration ‹S2›1/2vs. helical fraction fN exhibited a broad minimum. This behavior was consistent with the previous optical rotatory dispersion data, which had indicated that the transition of PHEG was characterized by very low cooperativity. The data for ‹S2› were analyzed by the method of Teramoto et al., to give 14.7A for the effective bond length of the randomly coiled portions and 1.97A for the pitch of the helix per monomer residue. The disparity of the latter value from the 1.5A expected for the α-helix was attributed to short-range interactions between the helical sections and the neighboring random coil residues. The Flory viscosity constant Φ was found to stay almost constant (about 2×1021) over the range of fN up to 0.9. This fact was taken to suggest that, for substantial portions of the transition, the average shape of a high molecular weight PHEG molecule is spherically symmetric like random coil.