硫酸交联壳聚糖干膜的13C CP MAS NMR研究

以不同浓度硫酸交联的壳聚糖干膜为研究对象,在国内首次采用¹³C CP MAS NMR技术从分子水平上对壳聚糖膜的结构进行研究,结果表明干膜壳聚糖分子的构象能直观地反映出膜的交联状况,交联状况与膜的分离性能密切相关,但仅对干膜的考察还不够全面.     

PAC Studies of BSA Conformational Changes

The structure of biological molecules plays an important role in many biological processes. The variation of ambient parameters such as pH, temperature or pressure can influence important properties of protein molecules like conformation or stability. By means of the perturbed angular correlation (PAC) technique and atomic force microscopy (AFM) a conformation change of bovine serum albumin (BSA) molecules has been studied as a function of the pH value of the BSA solution. The observed decrease of the rotational correlation time and the increase of molecule diameter as a function of pH were attributed to conformational changes of bovine serum albumin induced by different pH values of the BSA solution.     

Conformational mobility and intramolecular rearrangements of bis(3-thioxo-1-phenylpropenyl) sulfide

Possible intramolecular transformations of bis(3-thioxo-1-phenylpropenyl) sulfide were studied by the quantum-chemical semiempirical AM1 method. A group of the most stable, potentially spectroscopically discernible rotamers was distinguished. A possibility of intramolecular rearrangements giving thiirane structures was considered. The ability of bis(3-thioxo-1-phenylpropenyl) sulfide for spontaneous trimerization was evaluated. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2255–2261, December, 1999.     

The effect of the physical state on the equilibrium conformation of 2-arylpyrroles

The equilibrium torsion angles of 2-arylpyrroles in the liquid and solid phases were estimated by UV spectroscopy. In solution, compounds containing no substituents in positions 1, 3, and 2′ possess an average torsion angle of 24°, those containing one substituent have an angle of 29°, and in the case of two and three substituents, the angles are 53° and 65°, respectively. Phase transitions lead to flattening of the molecules in almost all cases. The average torsion angles in the compounds with no substituents in positions 1, 3, and 2′ decrease by ≈5° on passing from the gas to the liquid state and by ≈25° on going from the liquid to the solid state. The geometric parameters of 2-arylpyrroles with one or two substituents in positions 1, 3, and 2′ are less sensitive to phase transitions, while trisubstituted derivatives even retain their equilibrium conformations upon phase transitions. Deceased. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1472–1479, August, 1997.     

Anionic polymerization of 2,7‐di‐t‐butyldibenzofulvene: Synthesis,structure, and photophysical properties of the oligomers with a π‐stacked conformation

2,7‐Di‐t‐butyldibenzofulvene (tBu₂DBF), a bulky dibenzofulvene derivative, was polymerized using n‐butyllithium as initiator in tetrahydrofuran at ?78 °C and in toluene at 0 °C. tBu₂DBF afforded mainly oligomers up to trimer even at [monomer]₀/[initiator]₀ = 20 ([monomer]₀ = 0.2 M) at ?78 °C and 0 °C, indicating that this monomer is much less reactive than dibenzofulvene (DBF), its parent compound. The reaction at the same [monomer]₀/[initiator]₀ ratio at an elevated [monomer]₀ gave a small amount of insoluble polymer. The oligomers indicated a hypochromic effect in the absorption spectra and only monomer emission in the fluorescent spectra. The conformation of the trimer and the dimer was examined by means of NOESY NMR spectra and semiempirical calculations. In the trimer conformation, the fluorene moieties of the central and the initiation‐side monomeric units were found to be closely stacked on top of each other, while the termination‐side monomeric unit appeared to be in a faster conformational dynamics compared with the other monomeric units. Although the dimer seemed to have a relatively flexible conformation, a π‐stacked structure appeared to be involved in the conformational dynamics to show hypochromicity. The results of this study suggest that the reported intramolecular excited dimer (excimer) formation of the poly‐ and oligo(DBF)s [J Am Chem Soc 2003, 125, 15474] is based on a slight, local conformational change upon photo absorption, leading to a closer π‐stacked alignment of two neighboring fluorene units than that in the ground state. Such a local conformational transition may be difficult for the tBu₂DBF trimer because of steric repulsion of the t‐butyl groups. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 561–572, 2006     

A Novel Conformation Investigation on Newly Synthesized Compound of Diethyl Puerarin-7-yl Phosphate

1INTRODUCTION Puerarin(4?,7-dihydroxy-8-β-D-glucosylisoflavo ne),whose chemical structure is shown in Fig.1,is a C-glycoside compound.It is present in a large amount of active components of Puerariae radix,a com-monly used Chinese herb,which exerts sedative and antipyretic actions and is often used to treat influ-enza,wrist stiffness and headache[1].A number of investigations were carried out internationally to iden-tify the physiological activities of puerarin such as antiproliferative…     

光谱法研究钙离子对丝素蛋白溶解过程中结构的影响

为研究丝素蛋白在氯化钙溶液溶解过程中结构的阶段性变化特征,通过荧光光谱、紫外可见吸收光谱和拉曼光谱技术探讨了不同溶解时间下钙离子对丝素蛋白结构的影响情况。结果表明,在90℃左右,丝素蛋白与氯化钙溶液(Ca Cl2∶H2O=111∶180,质量比)作用0~30 min的时间段内,随着溶解时间的延长,钙离子逐渐渗透到丝素蛋白分子中,与丝氨酸(Ser)、酪氨酸(Tyr)侧链羟基进行配位而形成螯合物,丝素蛋白逐渐溶胀,分子结构变得松弛,埋藏在非结晶区内的色氨酸(Trp)和Tyr也逐渐暴露出来,分子构象由β-折叠向α-螺旋或无规线团转变。此外,外源性荧光探针(ANS)的结果表明,随着溶解时间的延长,丝素蛋白中的疏水性基团逐渐暴露于溶液中。电镜结果表明,丝素蛋白在氯化钙溶液的作用下逐渐由带状转变为片层状,最终呈球状结构。这些结果对调控丝素蛋白在氯化钙溶液中的溶解过程有着较为重要的现实意义。     

First genetic analysis of Cryptosporidium from humans from Tasmania,and identification of a new genotype from a traveller to Bali

Little is known about the molecular composition of Cryptosporidium species from humans living in the insular state of Tasmania, Australia. In the present study, we genetically characterized 82 samples of Cryptosporidium from humans following conventional coproscopic testing in a routine, diagnostic laboratory. Using a PCR‐coupled single‐strand conformation polymorphism (SSCP) technique, targeting portions of the small subunit rRNA (SSU), and 60 kDa glycoprotein (gp60) loci, we identified two species of Cryptosporidium, including C. hominis (subgenotypes IbA10G2, IdA16, IeA12G3T3, and IfA19G1) and C. parvum (IIaA16G1R1 and IIaA18G3), and a new operational taxonomic unit (OTU) that genetically closely resembled C. wrairi. This OTU was further characterized using markers in the actin, Cryptosporidium oocyst wall protein (COWP), and 70 kDa heat shock protein (hsp70) genes. This study provides the first characterization of species and genotypes of Cryptosporidium from Tasmania, and presents clear genetic evidence, using five independent genetic loci, for a new genotype or species of Cryptosporidium in a Tasmanian person with a recent history of travelling to Bali, Indonesia. It would be interesting to undertake detailed molecular‐based studies of Cryptosporidium in Indonesia and neighbouring countries, in conjunction with morphological and experimental investigations of new genotypes.