Supramolecular aggregates formed by L-glutamic acid-oligomers: SANS and SAXS studies of the hydrogen bonded self-assembly
作者:M. Ishida、M. Takai、H. Okabayashi、H. Masuda、M. Furusaka、C. J. O'Connor
DOI:10.1039/b100717n
日期:——
N-Acetyl-L-glutamic
acid oligomeric benzyl esters with various residue numbers (Np
= 4, 5, 6, 8, 10, 12 and 14) have been synthesized by a stepwise procedure. The microstructures of these oligopeptide aggregates in dioxane or benzene have been investigated by IR, small angle neutron scattering (SANS), and small angle X-ray scattering (SAXS) spectra. It has been confirmed from the IR spectral data that preferential stabilization of antiparallel-type β-sheet structures occurs above the critical aggregation concentration and that the population of this antiparallel β-sheet increases with an increase in concentration. On the basis of these IR results, the model of the rod-like aggregate, in which the disk-like β-sheet monomers are one-dimensionally stacked antiparallel to each other, has been presented for analysis of the observed SANS and SAXS intensity profiles. The best fit intensity profiles, calculated with variation only of the aggregation number and with fixed molecular parameters
based on the assumption of polydispersity, have furnished the monomer–monomer bond energies (ακT), corresponding to the hydrogen bonding energies, the number-average aggregation numbers, and the number-average molecular weights for these oligopeptide aggregates. Thus, the rod-like aggregates, formed by these oligopeptides in dioxane or benzene,
can be regarded as supramolecular aggregates.
N-乙酰-L-谷氨酸低聚苄
酯具有不同的残基数(Np=4、5、6、8、10、12和14),通过逐步合成得到。通过红外光谱、小角中子散射(
SANS)和小角X射线散射(
SAXS)光谱,研究了这些
二氧六环或
苯中的寡肽
聚合物的微观结构。红外光谱数据证实,在临界聚集浓度以上,反平行β-片层结构优先稳定,并且这种反平行β-片层数量随着浓度的增加而增加。根据这些红外结果,提出了
棒状
聚合物的模型,其中盘状β-片层单体彼此一维堆积,反平行排列,用于分析观察到的
SANS和
SAXS强度分布。根据多分散性的假设,仅改变聚集数并固定分子参数,计算出最佳拟合强度分布,从而得到单体-单体键能(ακT),对应于
氢键能、数均聚集数和这些寡肽
聚合物的数均分子质量。因此,这些寡肽在
二氧六环或
苯中形成的
棒状
聚合物,可被视为超分子
聚合物。