Effects of hydration on the acid-base interactions and secondary structures of poly-L-lysine probed by 15N and 13C solid state NMR.
Effects of hydration on the acid-base interactions and secondary structures of poly-L-lysine probed by 15N and 13C solid state NMR.
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15N和13C固态NMR探测氢化对聚-L-赖氨酸酸碱相互作用和二级结构的影响
DOI：
10.1039/c002730h
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
H. H. Limbach
中科院分区：
文献类型：
--
作者：
A. Dos;V. Schimming;M. Chan-Huot;H. H. Limbach
本文用高分辨固体~（15）N和~（13）C核磁共振谱研究了在酸存在下连续水合对固体聚-L-赖氨酸（PLL）~（15）N标记侧链氨基的影响。通常，水合导致形成由柔性侧链铵基团、酸性阴离子和少量水组成的局部“离子流体”相。相关的本地动态减少的宽度的不均匀加宽的15 N氨基信号发现的干燥状态。由α-螺旋和β-折叠片的混合物组成的游离碱PLL的水合作用通过与水的氢键结合产生的氨基信号的小的低场位移来监测，最终达到pH 13时PLL在水中的值。观察到两种构象无差异。PLL×HF采用类似的二级结构，具有孤立的NHF氢键;水合作用仅导致小的低场位移，但与水溶液中铵基团的形成相容。掺杂有少量HCl的PLL含有铵基团，其被相邻的游离氨基内部溶剂化。两种氮环境的特征在于不同的化学位移。每个氨基少于一个水分子的水合作用已经导致化学位移平均化，该化学位移平均化由质子沿沿着NH-氢键的快速运动以及侧链和阴离子的快速运动引起。 相比之下，全掺杂PLL×HBr和PLL×HCl的水合作用更为复杂。这些体系仅以β-折叠片构象存在，形成烷基铵盐结构。对于（i）干燥状态、（ii）湿β-折叠片和（iii）湿α-螺旋，观察到单独的15 N信号分量，湿α-螺旋在水合后连续形成。这些环境之间的交换是缓慢的，但水的运动导致两个潮湿的环境中的每一个内的平均氨基信号。这些结果表明，不同的环境形成域。由于NHBr或NHCl氢键被NHO氢键取代导致高场位移，因此观察到的分离信号是三个畴中水含量不同的结果。与以前的X射线粉末衍射研究一致，我们观察到在PLL×HBr的情况下，每个氨基超过3个水分子的α-螺旋区域占主导地位，在PLL×HCl的情况下，大约5个水分子，这是由于β-折叠片之间的有限空间和与氯化物相比更大体积的溴化物引起的。
Using high resolution solid state 15N and 13C NMR spectroscopy we have studied the effects of successive hydration on the 15N labeled side chain amino groups of solid poly-L-lysine (PLL) in the presence of acids. Generally, hydration leads to the formation of local “ionic fluid” phases composed by flexible side chain ammonium groups, acid anions and small amounts of water. The associated local dynamics reduces the widths of the inhomogeneously broadened 15N amino signals found for the dry states. The hydration of free base PLL—which consists of mixtures of α-helices and β-pleated sheets—is monitored by a small low-field shift of the amino group signal arising from hydrogen bonding with water, reaching eventually the value of PLL in water at pH 13. No difference for the two conformations is observed. PLL×HF adopts a similar secondary structure with isolated NHF hydrogen bonds; hydration leads only to small low-field shifts which are nevertheless compatible with the formation of ammonium groups in aqueous solution. PLL doped with small amounts of HCl contains ammonium groups which are internally solvated by neighboring free amino groups. Both nitrogen environments are characterized by different chemical shifts. Hydration with less than one water molecule per amino group leads already to a chemical shift averaging arising from fast proton motions along NHN-hydrogen bonds and fast side chain and anion motions. By contrast, the hydration of fully doped PLL×HBr and PLL×HCl is more complex. These systems exist only in β-pleated sheet conformations forming alkyl ammonium salt structures. Separate 15N signal components are observed for (i) the dry states, for (ii) wet β-pleated sheets and for (iii) wet α-helices which are successively formed upon hydration. Exchange between these environments is slow, but water motions lead to averaged amino group signals within each of the two wet environments. These results indicate that the different environments form domains. As the replacement of NHBr or of NHCl hydrogen bonds by NHO hydrogen bonds leads to high-field shifts the observation of separated signals is the result of different water content in the three domains. In agreement with previous X-ray powder diffraction studies we observe a dominance of the α-helical regions at above 3 water molecules per amino group in the case of PLL×HBr and at about 5 water molecules in the case of PLL×HCl, an effect arising from the limited space between β-pleated sheets and the larger volume of bromide as compared to chloride.
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影响因子：
15
作者：
Shasad Sharif;E. Fogle;M. Toney;G. Denisov;I. Shenderovich;G. Buntkowsky;P. Tolstoy;Monique Chan Huot;H. Limbach
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作者：
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DOI：
--
发表时间：
1978
期刊：
影响因子：
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通讯作者：
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DOI：
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1973
期刊：
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影响因子：
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作者：
S. Sharif;G. S. Denisov;M. D. Toney;H. H. Limbach
通讯作者：
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