碱脱胶法优化提取蚕丝素蛋白及其构象光谱

采取碱脱胶法对广西产桑蚕茧脱胶条件进行优化,利用苦味酸胭脂红法和扫描电镜对蚕丝脱胶程度进行检测,结果表明,蚕丝在脱胶浴比为1:200,脱胶30 min的条件下,其表面丝胶可脱除效果最好。将蚕丝脱胶所得丝素蛋白分别溶解在CaCl2-EtOH-H2O、LiBr-H_2O和LiBr-EtOH-H_2O3种溶剂中获再生蚕丝素蛋白溶液。在相同条件下,采用红外光谱、拉曼光谱对比研究蚕丝索蛋白的构象,结果表明碱脱胶法得到的天然丝素蛋白以β-折叠构象为主,再生丝素蛋白溶液构象以无规卷曲为主。对比3种溶剂对蛋白构象的影响,结果表明:溶剂中Li~(+)比Ca~(2+)对丝素蛋白的二级结构扰动更显著,倾向破坏蚕丝素蛋白的β-折叠构象,且溶剂中加入适量乙醇会进一步促进金属离子对丝素蛋白构象的影响。     

高含量再生丝素蛋白水溶液的热性能研究

用差示扫描量热仪(DSC),对不同含量的再生丝素蛋白水溶液(质量分数为12%~42%),以及同一含量不同剪切速率(1 000 s-1和2 000 s-1)下溶液热性能的变化进行了对比研究。结果表明,随着含量的增大,再生丝素蛋白水溶液发生相转变的温度逐渐降低;同样,经剪切后的溶液发生相转变的温度均向低温漂移,且随着剪切作用的加强,向低温的漂移越明显。试验表明,丝素水溶液含量的增加和剪切作用可加速溶液从无规线团或α-螺旋向β-折叠构象的转变速度,且随着剪切速率的提高,构象转变的速度也加快。     

再生柞蚕丝素蛋白膜的制备及其结构研究

用硫氰酸锂溶液溶解柞蚕丝素纤维，制备再生柞蚕丝素膜。用物理化学方法研究再生柞蚕丝素蛋白膜的结构特征以及暴露在空气中所发生的结构变化。指出再生柞蚕丝素膜内丝素蛋白的分子构象为α-螺旋和无规线团结构共存。空气环境存放30d后，分子构象只会发生无规线团向α-螺旋结构的少量转化，而不会向β-折叠结构转化。     

水溶性丝素蛋白的制备及其构象转变

通过液氮淬冷和冷冻干燥的方法获得了粒度均一、直径为3～4 mm的水溶性丝素蛋白微珠,并将丝素蛋白微珠分别进行室温保存、-20℃下保存和乙醇浸泡等不同方法处理。通过扫描电子显微镜(SEM)、傅里叶变换红外光谱仪(FT-IR)和X线衍射仪(XRD)等分析技术表征丝素蛋白微珠的形貌、构象和晶相组成。结果表明:液氮淬冷和冷冻干燥制备的丝素蛋白主要为无规线团结构,易溶于水;在室温和-20℃下放置1周后的丝素蛋白发生了由无规线团向β-转角、α-螺旋和β-折叠等构象转变,水溶性变差;经乙醇处理后的丝素蛋白因含有大量的β-折叠构象则不溶于水。     

丝素蛋白/聚乙二醇薄膜结构性质和药物释放研究

以溶液浇注法制备丝素蛋白/聚乙二醇(PEG)混合薄膜,利用傅里叶红外光谱(FT-IR)和差示扫描量热(DSC)分析薄膜材料结构的变化及对其力学性能和溶解性的影响,并以罗丹明B为模型药物构建药物缓释体系,分析罗丹明B从混合薄膜中释放的动力学,探讨利用PEG调节丝素蛋白材料的药物释放性能的可能性。结果显示,PEG与丝素蛋白具有良好的相容性,在作为增塑剂的同时引起丝素蛋白由无规卷曲向β-折叠结构的转变,可以在不同程度上调节混合薄膜的力学性能、耐水性和药物缓释性能。随着PEG含量的增加,丝素蛋白/PEG混合薄膜的拉伸强度和断裂延长率先增加后减小,分别于CPEG为10%和20%附近达到最大值,而在水中的溶失率的变化规律与拉伸强度刚好相反,在CPEG为10%附近达到最小值。与纯丝素蛋白薄膜相比,添加PEG极大延缓了药物模型分子罗丹明B的释放。罗丹明B的释放属于非典型Fickian扩散机理,混合薄膜中丝素的silkⅡ结晶和非结晶区域具有不同的药物释放特征,增加PEG添加量造成罗丹明B释放常数k的下降和扩散指数n的增加。     

掺杂Ca2+对YVO4晶体拉曼性能的影响

采用提拉法(Czochralsk i)生长了不同Ca2+掺杂浓度的CaxY1-xVO4晶体,计算了晶体中Ca2+的分凝系数.结果表明,随着Ca2+掺杂浓度的增加,分凝系数变小;对CaxY1-xVO4晶体进行了XRD分析,计算了其晶胞参数.测试了常温下晶体的拉曼光谱,对其谱线进行了归属,计算了晶体的受激拉曼散射参数,研究发现Ca2+的掺入有利于提高晶体的拉曼性能.     

剪切速率对高浓度再生丝素水溶液构象的影响

对高浓度的再生丝素水溶液（15％～37％）在不同剪切速率下（1000s-1和2000s-1）的构象变化进行了研究，对剪切前后的溶液进行了DSC和Raman对比测试。发现经过剪切，丝素溶液更客易发生从无规线团或α-螺旋向β-折叠构象的转变，且转变的程度随所受剪切速率的增加而提高。而且当丝素浓度低于27％时对剪切不敏感；超过30％时则对剪切敏感。     

再生丝素与无机纳米粒子复合膜的结构与性能

用溶胶-凝胶法制备了纳米二氧化钛再生丝素复合膜,并用扫描电镜(SEM)、X射线(XRD)、热重分析(TGA、DTG)对复合丝素膜的结构与性能进行了表征。结果表明:加入纳米二氧化钛颗粒后再生丝素膜的热转变温度提高;再生丝素的结晶构象由S ilk I向S ilk II转变,结晶度增加。     

再生丝素水溶液在存放过程中的结构变化

通过拉曼光谱法研究了不同浓度的再生丝素水溶液在常温下存放不同时间的构象变化。发现再生丝素水溶液在静置存放过程中会有结构的变化即无规巷曲和α螺旋向β折叠结构的转变，并且浓度越大，构象转变越快。当溶液处于流动状态时，其构象转变速度要快于静置状态下的转变。同时发现对于新鲜制备出的再生丝素水溶液随浓度的增加，也会发生构象的转变。     

低温下离子液体[BMIM][TFSI]的拉曼光谱

结合差示扫描量热技术和变温拉曼光谱,研究了咪唑类离子液体1-丁基-3-甲基咪唑双三氟甲磺酰亚胺盐([BMIM][TFSI])的相变和分子构象随温度的变化。研究结果表明:样品从常温降至190 K过程中,一直保持液态,继续降温至184 K左右出现玻璃化转变。升温过程中,在240 K左右出现放热峰,同时有新的拉曼峰出现,表明[BMIM][TFSI]由无序结构转变为有序的结晶相。当温度升高到270 K左右时,[BMIM][TFSI]熔化回到初始液态,说明[BMIM][TFSI]在温度变化过程中的相变是可逆的。通过对[BMIM][TFSI]分子构象的拉曼特征峰进行定量分析可知:在常温液态时反式和顺式两种构象共存,但随着温度降低,反式构象的比例增加。升温时,伴随240 K时结晶态的转变,反式构象消失,表明通过冷结晶得到的晶体仅有顺式构象。     

丝素在NMMO·H2O中的溶解及溶液流变性能的研究

探讨了丝素在N-甲基吗啉-N-氧化物一水合物(NMMO.H2O)中的溶解行为,结果发现:天然蚕丝纤维脱胶后得到的丝纤维可以直接溶解在NMMO.H2O中,但是很难得到高于10%浓度的溶液,因而无法用于纺丝.而由再生丝素水溶液制得的再生丝素膜则易于溶解在NMMO.H2O中,并可以得到浓度高达25%的再生丝素/NMMO.H2O溶液,在上述研究的基础上,本文还对再生丝素/NMMO.H2O的流变行为进行了初步研究.     

Preparation and Characterization of Silk Fibroin Aerogel

Silk protein fibroin,as a biomedical material,has good biocompatibility,biodegradability,regulation and excellent physical and chemical properties. In this work,a low density porous silk fibroin material is prepared from fibroin solution by high-speed shearing with impeller. By adjusting shear rate of the stirrer,silk fibroin aerogel with different sizes of the aperture is prepared. In general, this aerogel has small porosity, uniform pores, good mechanical properties and slow rate of degradation. It is observed that increasing the shear rate results in higher porosity of aerogel,while the diameter of the aerogel becomes smaller. This silk aerogel may offer a new option as biomaterial for the tissue engineering application based on the information on the structural behaviors.     

Effects of metal ions on recombinant calcineurin A subunit

Effects of metal ions on activities and solution conformations of calcineurin A subunit have been examined. The ability of several metal ions to activate calcineurin A has been tested with Ni²⁺> Mn²⁺> Mg²⁺/Ca²⁺. The corresponding CD spectra and intrinsic fluorescent emission spectra show that calcineurin A exists in different metal ion-dependent conformation states. Effects of the different concentritions of Ni²⁺ on activities and solution conformations of calcineurin A have been tested too. Results indicate that effects of these metal ions to activate calcineurin are due to their conformational changes.     

Cu（Ⅱ） effect on the conformation of regenerated silk fibroin in dilute aqueous solution

Much attention has been paid to the natural mechanism of silkworm spinning due to the impressive mechanical properties of the natural fibers. In this work, we studied the effect of Cu（Ⅱ） ions on the secondary structure of Bombyx mori regenerated silk fibroin （SF） in dilute solution by circular dichroism （CD）. The results indicate that a given amount of Cu（Ⅱ） induces the SF conformational transition from random coil to β-sheet, however, further addition of Cu（Ⅱ） is unfavorable for this conversion. Meanwhile, the conformational changes induced by Cu（Ⅱ） follow a nucleation-dependent aggregation mechanism, which is similar to that found in Prion protein （PrP） denaturation and Aβ-peptide aggregations, leading to the neurodegenerative disease. This work would help one understand further the natural spinning process of silkworm. Additionally, it would be significant for the study of the nervous system diseases, because silk fibroin, extracted in large amounts from Bombyx mori silkworm gland, could be a proper model to study PrP denaturation and Aβ-peptide aggregations.     

Preparation of insoluble fibroin films and its tensile property

Silk fibroin is becoming a promising biomate-rial because of its excellent biocompatibility. However, theregenerated fibroin is usually soluble in water and its me-chanical properties should be improved. Although manymethods, such as adding other polymers or treating withmethanol, can ameliorate the mechanical properties andinsolubility, the biocompatibility of fibroin is usually dam-aged in these processes. In this article, it is first reported thatthe insoluble fibroin films are directly prepared withoutmethanol treatment. According to the results of Fouriertransform infrared spectroscope (FTIR) and the X-ray dif-fraction (XRD), the amount of IS-sheet conformation in-creased with the increasing of concentration. When fibroinfilms are dried from 15 wt% at 60℃, the films become in-soluble in water. More importantly, The tensile strength andelongation of the insoluble fibroin films dried from 15% so-lution at 60℃ reached 15.9 MPa and 49.4% respectively in the wet state, which is distinctly superior to the fibroin films treated with methanol.     

家蚕丝素溶液的粘弹性研究

采用Coucttc流变仪对家蚕丝素溶液的粘弹性进行研究。对于生丝丝素溶液,当丝素浓度较稀时(如4w/v％),溶液表现出牛顿流动行为;当丝素浓度较高时(如25W/V％),溶液表现出复杂的非牛顿流动行为。成烈的家蚕丝腺中的丝素,在剪切速率大于0.25s~1时,能引起纤维化。     

Synthesis and luminescence properties of Ca2SiO4-based red phosphors with Sm3+ doping for white LEDs

Sm³⁺-activated Ca₂SiO₄ red phosphors were prepared by the conventional high-temperature solid-state reaction method, and the effects of sodium (Na⁺) and samarium (Sm³⁺) ions doping concentrations on their crystal structure and luminescent properties were investigated by X-ray diffraction (XRD) and fluorescent spectrofluorometer. XRD patterns demonstrate that a well-crystalline structure forms in the phosphors when they are treated by calcination at 1200°C for 4 h, and the excitation spectra exhibit good absorption in the range between 350 and 420 nm. Under the irradiation of 405 nm near-ultraviolet (NUV) light, the spectra of the phosphors show a main emission peak at 601 nm attributed to the ⁴G_5/2??⁶H_7/2 transition of Sm³⁺ ions, and its intensity is greatly influenced by the concentrations of Sm³⁺ and Na₂CO₃. When the concentrations of Sm³⁺ ions and Na₂CO₃ are 2mol% and 6mol%, respectively, the optimal emission intensity can be obtained. From strong absorption in the near ultraviolet zone, the Na_0.06Sm_0.02Ca_1.92SiO₄ phosphor is a promising red-emitting phosphor for white light emitting diodes (W-LEDs).     

Effect of calcium ions on the secondary structures of photosystem II and its relations with photoinhibition

Calcium ions play an important role in the oxygen-evolving process of photosystem II as demonstrated in many experiments. The changes of the secondary structures of PS II induced by the depletion of Ca²⁺ were reported. The results indicated that the removal of Ca²⁺ led to the transition of ahelix to turns and sheet structures. While Ca²⁺ was re-added to the media, only the structures changed to turns could be recovered. The protein conformational changes of PS II during the donor side photoinhibition induced by the depletion of ca²⁺ were also studied. This showed that the protein conformational changes differed between the control and Ca²⁺-depleted samples in a short period of illumination (within 10 min). However, the changes became similar when the illumination time was increased.     

Fine Structure of Regenerated Silk Fibroin Solids

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