我们对L-苯丙氨酸进行了全势能面搜索,采用B3LYP方法优化了L-苯丙氨酸的648种可能构象,最终得到了37种稳定存在的构象.分别采用B3LYP、B3PW91、M06-2X、MP2和CCSD(T)计算了L-苯丙氨酸最稳定的10种构象的相对能量,其中M06-2X和MP2方法能够给出较好的结果.对比不同的基组,说明采用aug-cc-pVDZ已经接近达到基组收敛极限.用电子传播子理论P3近似方法计算稳定构象外价壳层轨道的垂直电离能与光电子能谱实验符合的很好;根据构象的相对能量以及理论模拟与实验的光电能谱的比对,说明对气相光电子能谱至少四种构象有贡献.

The full potential energy surface of L-phenylalanine has been searched.A total of 648 unique trial structures were generated by allowing for all combinations of internal single-bond rotamers and were optimized at the DFT/B3LYP level of theory.A total of 37 local minima conformers were found. The relative energies of ten low-lying conformations are carried out with five different methods:B3LYP, B3PW91,M06-2X,MP2 and CCSD(T).Comparing the relative energies of different methods,we find M06-2X and MP2 can predict a good result.Comparing the relative energies of different basis sets,one can draw a conclusion that the aug-cc-pVDZ basis set is high enough to give a convergent result.The vertical ionization energies of the conformers calculated with electron propagator theory P3/aug-cc-pVDZ are in good agreement with the experimental data from photoelectron spectroscopy.The relative energies of the conformations and the comparison between the simulated and experimental photoelectron spectra sh

目的研究湿热灭菌前后玻璃酸钠注射液中玻璃酸钠的分子量及构象。方法采用温度121℃，灭菌时间分别为12，15，18，25min。结果灭菌时间的延长与分子量的下降呈正相关性，样品的构象因子值始终为0．5-0．7。结论灭菌后产品分子量符合国家标准；灭菌过程中玻璃酸钠分子量均一性较好；灭菌操作对玻璃酸钠分子无规则线团构象的影响不大。

Objective To investigate the impact of steam sterilization on the molecular weight and conformation of sodium hyaluronate. Methods The sterilization was carried out at 121℃with duration of 12, 15, 18, 25 minutes, respectively. Results The extension of sterilization time and the decrease of molecular weight showed a positive correlation, the conformation factor values were always between 0.5-0.7. Conclusion The molecular weight of sodium hyaluronate after sterilization is complied with national standards;the molecular weight distribution of sodium hyaluronate in the sterilization process is rather limited;sterilization has little effect on the random coil conformation of sodium hyaluronate.

目的：研究甘氨酸（Gly）阳离子态、阴离子态和两性离子态在气相真空、油相环己烷和水相环境中的构象蜕变行为。方法：运用CAM-B3LYP和B3LYP方法在6-311＋＋G（2d，p）基组水平上对Gly不同离子态，进行几何结构、电子结构、振动分析和热力学函数计算，并运用极化连续模型（PCM）考察溶剂效应。结果：在气相、油相和水相3种环境中得到阳离子态的构象分别有3、3、5种，阴离子态的构象有1、1、3种；3种环境中只有极性强的水相中得到1种两性离子态构象且与中性分子态能量差别不大。两种方法计算得到键角一致，前者计算得到键长稍短，后者能量稍低。结论：Gly在不同环境中构象变化行为不同，环境极性增加，有利于离子态存在。

Objective:To study the conformation disintegration of glycine in cationic, anionic, and zwit-terionic states in gas phase and solvent environments with cyclohexane and water. MethodThe geometric and electronic structures, vibrational frequencies, thermodynamic functions of ionic glycine were calculated fully at the CAM-B3LYP and B3LYP theory levels using 6-311++G (2d, p) basis set. The solvent effects were dealt with the polarizable continuum model (PCM). ResultTo the cationic state, there were 3, 3, and 5 conformers, and to the anionic state, only 1, 1, and 3 conformers existed in three environments, but there was only 1 zwitterionic conformer in the water environment and its energies were higher slightly than the most stable neutral conformer. Two methods got the similar properties values but the former optimized bonds distances were shorter slightly and the latter obtained energy values were a little lower. Conclusion:The conformation disintegration of ionic gly-cine in di

天然无结构的突触核蛋白a-synuclein(AS)与帕金森病密切相关。最近研究发现低盐与高盐环境下 AS 纤维化的速率不同，所形成的纤维结构，细胞毒性与传染性也不一样，但盐效应对 AS 聚集及纤维结构影响的具体分子机制仍不清楚。该文通过生物标记方法在AS的酪氨酸芳香环上引入19F标记的探针，利用19F核磁共振(NMR)方法研究了低盐与高盐环境下AS的构象差异，发现19F NMR对天然无结构蛋白构象变化非常灵敏，AS在低盐中的构象比较紧密，而在高盐下比较松散，这种在溶液中起始的构象差异可能是导致最终AS纤维结构与生物效应不同的原因。

α-synuclein is an intrinsically disordered protein, and is implicated in Parkinson''s disease. Previous studies have found that the aggregation rate, fibril structure, propagation and cytotoxicity of α-synuclein change markedly with salt concentration. However, the underlying molecular mechanisms remain poorly understood. In this work, 3-fluorotyrosine (3FY) labeling was introduced into α-synuclein, and the conformational changes of the protein under different salt concentrations were studied by 19F NMR. It was found that the protein was more compact at low salt concentration than at high salt concentration; and such conformational changes may account for the fibril morphology diversity and physiological effects of the protein at different salt concentrations. It was also concluded that 19F NMR is a sensitive technique to measure conformational change of intrinsically disordered protein.

在293-393K温度范围内，分别采用傅里叶红外光谱、二阶导数红外光谱、四阶导数红外光谱及去卷积红外光谱测定硬脂酸亚甲基面外弯曲振动（ωCH2），来进一步研究温度对于硬脂酸脂肪链构象的影响。实验发现：在1180-1320cm^-1范围内，硬脂酸ωCH2存在“第一特征谱带”和未见文献报道的“第二特征谱带”。硬脂酸脂肪链由全反式有序构象到无序构象的改变的临界温度为353-358K，并进一步研究了温度对于硬脂酸ωCH2红外吸收峰强度的影响。

The temperature effect of stearic acid chain conformation had been studied with the methylene out-of-plane wagging vibration (ωCH2) by FT-IR spectra,second derivative FT-IR spectra,four derivative FT-IR spectra and deconvolution infrared spectra in the temperature range from 293 K to 393 K. The first key frequency band and unreported the second key frequency band were discovered in the band range from 1180 to 1320 cm-1. The critical temperature of stearic acid from all-trans order conformation to disorder conformation was 353-358 K. The temperature effect on bond intensity was discussed also.