取代基对卟吩结构和性质的影响

运用密度泛函理论(DFT) B3LYP/6-31G(d, p)方法, 对卟吩及其被取代基—CH=CH₂、—COCH₃、—CHOHCH₃、—CHNH₂CH₃或—CHSHCH₃所修饰后的分子构型进行了优化. 同时, 对其电子吸收光谱与核磁共振氢谱也进行了量化计算. 结果表明, 这些取代基有着各自不同的空间构象, 对卟吩环的整体结构没有很大的扰动. 然而, 它们重新调整了卟吩环中原子电荷的分布, 改变了前线分子轨道(LUMO-HOMO)能隙, 结果导致卟吩的吸收光谱与¹H NMR均发生了相应的改变.     

The concept of dual roles design in clean organic preparation

Herein we summarized some clean preparation examples to emphasize the concept of dual roles design (or named as “two birds one stone strategy”) in green and sustainable chemistry. In those examples, the reactants and/or solvent play dual roles rendering a cleaner organic preparation process. Consequently, both the chemical waste and manufacturing cost could be reduced.     

高效液相色谱-电喷雾串联四极杆质谱法研究人尿中毛果芸香碱代谢产物

本文采用高效液相色谱-电喷雾串联四极杆质谱法对人口服毛果芸香碱后的尿样的代谢产物进行了研究.     

The Regulation Effect of Phosphoryl Group on Amino Acid Side Chain

The amino acids' side chains act as the relay device to modulate the chemical reactivity of the N-phosphoryl amino acids. The N-dialkyl phosphoryl cysteine is stable, but the N-dialkyl phosphoryl serine or threoine was converted into many kinds of products at 40℃. The N-dialkyl phosphoryl gltamic acid is a stable compound, while the N-dislkyl phosphoryl aspartic acid was transferred into the peptides, esters and the phosphoryl ester-exchanged products under mild conditions. The N-dialkyl phosphoryl histidine has the similar reactivity through the co-participation of the side chain, carboxyl and phosphoryl groups. A hexacoordinate phosphorus was proposed to account for this differentiation and promotion effect.     

pH Responsivity and micelle formation of gradient copolymers of methacrylic acid and methyl methacrylate in aqueous solution

A series of gradient copolymers of methacrylic acid (MAA)/methyl methacrylate (MMA) with four end-to-end composition profiles (uniform, linear gradient, triblock with linear gradient midblock, and diblock) but all having an average chain composition of ?F(MMA) ≈ 0.5 and an average chain length of 200 were synthesized via model-based, computer-programmed, semibatch atom-transfer radical copolymerization (ATRcoP). These samples allowed us to investigate systematically the effects of the gradient composition profile on the pH responsivity and micelle formation of the copolymers in an aqueous solution. Measurements included light transmittance, TEM, AFM, DLS, (1)H NMR, and pH titration. It was found that linear gradient, triblock, and diblock copolymers formed spherical micelles at high pH. The micelles of the linear gradient copolymer contained MMA units in their hydrophilic shells, and those of the triblock and diblock copolymers had all of their MMA units residing in their cores. The composition profile showed a strong effect on the degree of acid dissociation at a given pH. The conformational transition of the copolymer chains was determined by both the pH value and composition profile. Copolymers having sharper gradients required a lower pH to trigger the conformational transition and a narrower pH range to complete the transition.     

Computational insight into asymmetric uranyl-salophen coordinated with cyclohexenone derivatives

Uranyl–salophen (U–S) complexes, as modified by unilateral benzene and coordinated with cyclohexenones substituted by methyls or fluorines in E/Z-types, were investigated using density functional theory calculations at the level of B3LYP/6–311G** basis set. The results indicated that the O of substituted cyclohexenones could coordinate with U of the asymmetric U–S complexes. When the C=C bond of cyclohexenones was located upward in the twisted salophen plane, the binding energies of the cyclohexenones to the asymmetric U–S and Wiberg bond indices (WBIs) of carbonyl oxygen to uranium (U–O) were higher than those of the C=C bonds located downward. It could be concluded that when cyclohexenones were coordinated to the asymmetric U–S, the major products would be the complexes in which the C=C bond of cyclohexenones locates upward in the configuration. Binding energies of the E-type substituted cyclohexenones to the asymmetric U–S were higher than those for the Z-type ones.     

铀酰-Salophen受体对α, β-不饱和羰基化合物及手性客体的分子识别

基于密度泛函理论(DFT)的计算方法,研究了不对称铀酰-salophen受体对α, β-不饱和羰基化合物客体及手性小分子的分子识别。理论计算结果表明:配合物中受体的U原子与客体的O3原子配位,且受体与客体之间结合能随受体上芳环取代基的增大而增大; R₂, R₃-系列配合物中U―O3键的稳定性比R₁-系列的更强;配位后的α, β-不饱和羰基化合物中C＝C与C＝O之间的共轭效应减弱。而且,通过圆二色谱(CD)及结合能计算表明:芘基铀酰-salophen (受体3)对(R)-1-(2-萘基)乙胺的分子识别选择性优于(S)-1-(2-萘基)乙胺。因而,这些研究结果为不对称铀酰-salophens具有分子识别能力提供了新的信息。     

蛋白质功能的扩展与人工金属结合位点的理性设计

生物体系中金属离子在调节金属蛋白的结构和功能中发挥着至关重要的作用。本文综述了利用人工金属结合位点的理性设计来扩展蛋白质功能范围的研究进展,包括在蛋白分子内部通过探索潜在的结合金属位点、重新设计已有的金属结合位点、以及设计全新的金属结合位点的方法来设计人工金属结合位点,和在蛋白分子表面进行设计,来获得结构及功能的转化、研究与纳米材料间的相互作用、以及进行蛋白质分子的自组装。这些研究进展极大地丰富了我们对金属蛋白结构与功能关系的认识。同时,也赋予了我们控制及利用感兴趣蛋白的能力。     

N-PHOSPHORYL AMINO ACIDS AND PEPTIDES: PART I. THE CRYSTAL AND MOLECULAR STRUCTURE OF N-(O,O-DIISOPROPYL PHOSPHORYL)-TRANS-4-HYDROXY-D,L-PROLINE

Abstract

The crystal and molecular structure of N-(O,O-diisopropyl phosphoryl)-trans-4-hydroxy-D,L-proline has been determined by X-ray diffraction analysis and is compared with proline or hydroxyproline residue in a peptide chain described in the literature. The compound crystallized in orthorhombic system with space group P2₁2₁2₁, a=6.934(2), b=8.694(3), c=26.727(7) Å, V=1611.3(8) ų, Z=4, Dx=1.22 g/cm³. The structure was solved by direct method and refined by anisotropic least squares to a discrepancy index R=0.072. In the compound, the nitrogen atom is trigonal and its remaining 2p orbital is conjugated with the P?Oπ system; the conformation of the phosphorimidate function is favoured by the trans orientation of the P=O bond with respect to the N-C4 bond. In the pyrrolidine ring moeity, the C2-C1-N-C4 atoms are nearly copolnar and the C3 atom is out of the plane by about 0.47 Å.     

Fluorescence of proteins induced by two-photo absorption

At room temperature, the UV fluorescence of trypsin, thyroglobulin, hemoglobin and ablumin are observed; these molecules undergo two-photon absorption when they are excited with the radiation of a frequency-duplicated Q-switched Nd:YAG laser. It is shown that the fluorescence of these proteins comes from the tryptophan residues and that it has a red shift of about 20 nm relative to the one-photon fluorescence. We suggest that the weak emission from tyrosine arises from the forbidden two-photon transition. The influence of concentration on the fluorescence of hemoglobin and tryptophan is discussed. The two-photon absorption cross-sections are estimated.