金属离子导致的丝素蛋白的构象转变

蚕丝和蜘蛛丝的优异力学性能一直是科学家们关注的课题^[1-3]。近年来,在蚕丝蛋白结构及其构象方面的研究取得了许多进展^[3-5]。在蚕的腺体中丝素蛋白的构象为silk I（主要是无规线团为主,还有少量的β－转角,α螺旋等）,而在纤维状的丝中为silk Ⅱ（主要是β折叠）。金属离子在蚕叶丝过程中的作用也一直是一个人们关心的问题。Chen等^[6]在研究丝胶（包附在丝素蛋白表层的另外一种蛋白）时发现,在一定pH条件下,Ni^2 离子通过四配位的螯合作用诱导丝素蛋白β折叠的形成。并且,Viney等^[7]根据电感耦合等离子体（ICP－MS）技术推测Ca^2 的增加能使β折叠的形成加速。     

pH值对丝素蛋白构象转变的影响

模仿家蚕吐丝过程中伴随丝素蛋白自然脱水的纤维化过程,研究了再生丝素蛋白在各种pH值的磷酸盐缓冲溶液体系中自然干燥脱水成膜后的构象转变.利用激光拉曼散射光谱及其二维相关光谱,定性分析了丝素蛋白酰胺区(1600～1700cm^-1)散射峰的相关组成及结构.在此基础上,利用¹³CCP-MAS固体核磁共振谱对丝素蛋白丙氨酸C_β峰(δ14.5～22)进行了解析拟合.从而确定了体系中与Silk及Silk构象相关的组成含量与pH值的关系.结果表明,pH=5.2的酸性溶液有利于蚕丝丝素蛋白从Silk向Silk构象转变,而中性与碱性溶液(pH=6.9和8.0)则对丝素蛋白的构象转变影响甚小.     

开放、合作、共赢——图书馆对外文化交流工作新策略

概述了陕西省图书馆近20年对外文化交流工作的开展情况和重要特点,提出图书馆对外文化交流工作应抓住＂丝绸之路经济带＂建设的机遇,通过发展与丝绸之路沿线国家的特色文献资源合作、设立交流之窗或友好馆、利用国际图联平台等方式,更好地推进对外交流与合作工作,真正实现开放、合作、共赢。     

古骆越方国考证

古骆越方国是中国商周时期，以壮族祖先为主建立的地方政权，其范围大致在两广南部到今越南北部以及整个南海。中心在今广西郁江、邕江、左右江一带。骆越方国的主体族群壮侗语族各民族，开发了中国岭南南方直到整个南海，开辟了海上丝绸之路，对祖国做出了很大的贡献。     

Silk fibroin microfibers and chitosan modified poly (glycerol sebacate) composite scaffolds for skin tissue engineering

Porous mSF/PGS and CS/PGS composite scaffolds were prepared by the combination of poly(glycerol sebacate) (PGS) with silk fibroin microfibers (mSF) and chitosan (CS) as modifiers through particulate leaching and freeze-drying techniques. Both mSF/PGS and CS/PGS scaffolds show highly interconnected and open porous structures, and the crosslink density and water absorption of PGS were obviously enhanced by the modifiers. Moreover, the silk fibroin microfiber and chitosan can slow down and control the degradation rate of PGS. The biocompatibility of these porous PGS based composite scaffolds for skin tissue engineering was evaluated by cell culture experiments, and the results indicate of the good attachment, proliferation and deep penetration of cells into these composite scaffolds.     

Fabrication of silk sericin/alginate microparticles by electrohydrodynamic spraying technique for the controlled release of silk sericin

Silk sericin has been recently investigated for many biological roles. This study aimed to develop the new delivery system to control the release of silk sericin. The alginate microparticles encapsulating silk sericin were fabricated by electrospraying technique. Concentrations of silk sericin and alginate polyelectrolyte solutions were investigated. All microparticles had an average size of 264–284 μm and could entrap silk sericin with high entrapment efficiency (84–89%). The microparticles could deliver silk sericin in a rate-controlled manner. This study would show a promising controlled release application of silk sericin protein from alginate microparticles fabricated by the means of electrostatic forces.     

Silk‐Ion Jelly: a novel ion conducting polymeric material with high conductivity and excellent mechanical stability

In this work, a thin, flexible and mechanically stable polymer conducting material (Silk‐Ion Jelly) was developed though application of Ion Jelly on to silk fabrics. Ion Jelly was prepared through jellification of a room temperature ionic liquid, 1‐butyl‐3‐methyl‐imidazolium dicyanamide ([bmim][dca]) using gelatin and water and applied to silk fabrics using two different processes: impregnation and in‐situ. Various parameters influencing ionic conductivity such as Ion Jelly composition (ratio of [bmim][dca], water and gelatin) and incorporation as well as the type of application process were thoroughly investigated. It was observed that the Ion Jelly compositions containing lower gelatin and water ratio as well as application through in‐situ process at high temperature (200 °C) led to considerable improvement in conductivity, mainly due to increased [bmim][dca] concentration, structural flexibility and reduced silk crystallinity. Silk‐Ion Jelly prepared using optimized conditions showed excellent mechanical stability and possessed high room temperature conductivity (2.9 × 10^?3 S. cm^?1), similar to [bmim][dca], and therefore, this novel ion conducting material may find potential applications in electrochemical devices due to its eco‐friendly preparation route using biomaterials and green solvents. Copyright © 2012 John Wiley & Sons, Ltd.     

Highly enantioselective acylation of chlorohydrins using Amano AK lipase from P. fluorescens immobilized on silk fibroin–alginate spheres

Aromatic, allylic, and aliphatic compounds containing a chlorohydrin group were selected as substrates for the enzymatic kinetic resolution mediated by Amano AK lipase from Pseudomonas fluorescens immobilized in silk friboin-alginate spheres. Thus, the enantioselectivity of the process was sufficient for the production of the desired alcohols and acetates in good yields and high enantiomeric purities. This Letter provides a simple, cheap, and practical protocol for enantioselective synthesis of chlorohydrins and reinforces the versatility of silk fibroin as supports for heterogeneous catalysts.     

Wet-spinning of Regenerated Silk Fiber fromAqueous Silk Fibroin Solutions: Influence ofCalcium Ion Addition in Spinning Dope on thePerformance of Regenerated Silk Fiber简

Ca（II） ions are added in the spinning dope to adjust the solidification rate of regenerated silk fibroin （RSF） solution during the wet-spinning process since Ca（II） ions are proved to be favorable to maintain the stable silk fibroin network in our previous work. The results show that when Ca（II）/RSF ratios are 1/50 and 1/20, the resulted RSF fibers exhibit good performance with the breaking energy more than 70 kJ/kg. However, higher Ca（II）/RSF ratio （for example, 1/10） hinders the solidification of spinning dope and results in poor RSF fibers. These observations together with earlier papers from this laboratory confirm that to produce tough silk fibers the spinning conditions must allow sufficient time for the adjustment of silk fibroin molecular chains.     

Effect of Silk Fibroin Reinforcement on the Properties of Potato Starch-Polyvinyl Alcohol Blend Films

Starch and polyvinyl alcohol composite films, reinforced with raw and methylmethacrylate-grafted silk fibroin particles, were prepared by the solution-casting method on leveled plates. Silk fibroin was used as reinforcement for starch and polyvinyl alcohol (St/PVA) blends in order to improve their mechanical and water-resistance properties. The composites were plasticized with citric acid and cross-linked with gluteraldehyde. The reinforced films showed an increase in tensile strength with decrease in elongation at break. The optimized samples were characterized by scanning electron microscopy and were studied for their antibacterial properties. The biodegradable behavior was studied by the soil burial method.