利用二维同步荧光相关光谱研究温度对胶原溶液中分子聚集行为的影响

采用恒波长同步荧光法和二维相关分析技术研究了不同浓度Ⅰ型胶原溶液中胶原分子聚集行为随温度升高(10~70 ℃)的变化规律。选取0.2,0.4,1.6 mg·mL-1的胶原溶液,在初始温度下各浓度溶液中胶原分子分别处于单分子状态、较低程度和较高程度的聚集态。研究表明：波长差为9 nm的同步荧光光谱中,激发波长282和292 nm处荧光峰分别归属于未参与形成氢键的Tyr(酪氨酸)残基和参与形成氢键的Tyr残基。对升温过程同步荧光数据进行二维相关分析,得两荧光值对温度的响应顺序,进而推测得到：当温度低于30 ℃时,0.2 mg·mL-1溶液中出现了胶原分子间形成Tyr残基参与的氢键的趋势。0.4和1.6 mg·mL-1的溶液中原有聚集体可能发生进一步聚集,形成疏水微区。当逐步接近胶原变性温度(36~38 ℃)时,推测0.4和1.6 mg·mL-1胶原溶液中的疏水微区和聚集体有被破坏的趋势,而0.2 mg·mL-1胶原溶液保持分子间形成氢键的趋势。超过胶原变性温度时,各浓度溶液中胶原分子三股螺旋结构发生松散。当超过45 ℃时,胶原分子三股螺旋结构松散的趋势更为明显。     

胶原蛋白温度效应的Raman光谱研究

在不同温度下对Ⅰ型胶原蛋白进行了拉曼光谱测定。结果表明：随温度的升高，多数谱线向低波数移动，但CH2的变形振动谱线1302cm^-1向高波数移动，苯丙氨酸的特征振动谱线1003cm^-1的波数基本保持不变。同时还给出了拉曼谱线强度随温度的变化关系，得到了0，40，68，90℃四个变性峰，其中40，68℃的峰与DSC(差示扫描量热法)和SHG(二次谐波法)的测量结果一致，0℃的峰为冰冻相变，90℃的变性峰为胶原的二级结构被破坏所致。当温度达到150℃时，谱线强度显著降低，大部分谱线消失，胶原的一级结构遭到破坏。实验还发现胶原纤维在低温区具有较好的复性特性。     

微波辐射炼焦煤中噻吩硫结构的非热效应研究

采用XANES和XPS解析山西炼焦煤中有机硫的赋存特征,选择与煤中结构匹配的噻吩硫模型化合物进行微波辐射和水浴加热,通过Raman光谱比较研究两者对模型化合物中含硫结构的作用机制,利用Materials Studio构建、优化模型化合物结构,用密度泛函理论计算模拟微波场中模型化合物分子构型参数,解析含硫结构对微波的响应机理。结果表明：噻吩硫是炼焦煤中有机硫最主要的赋存形式。微波辐射后,模型化合物碳硫键和硫硫键的Raman谱吸收峰发生红移,温升速度快的模型化合物红移较小;相同温升的水浴加热后,几乎没有红移现象。微波能量不足以使模型化合物中碳硫键和硫硫键断裂,但能够改变分子构型,模型化合物含硫键在微波场中可能存在某种过渡态。微波作用对煤中噻吩硫结构存在非热效应。     

基于二维红外技术研究氧化羧甲基纤维素钠/胶原的相互作用及热稳定性

采用氧化羧甲基纤维素钠(OCMC)作为交联剂,对胶原溶液进行改性并采用二维红外技术分析OCMC与胶原之间的相互作用及其对胶原热稳定性的影响。一维红外图谱显示OCMC交联改性对胶原的主要特征吸收峰即酰胺Ⅰ,Ⅱ和Ⅲ带的峰位与强度无明显影响;改性前后胶原的酰胺Ⅲ带与1 455 cm-1处吸光度的比值A_Ⅲ/A_{1 455}均接近于1.000,以上结果显示交联键的引入不会破坏胶原的三股螺旋结构,但无法获知胶原与OCMC之间的相互作用及胶原结构的变化。以OCMC用量为外扰条件建立二维红外相关图谱,进一步分析两者间相互作用。结合胶原结构与OCMC中基团的响应强度及顺序可知：OCMC首先通过羧基与胶原中精氨酸的胍基或赖氨酸的氨基发生静电作用,随后醛基与胶原氨基之间发生希夫碱反应;两者之间相互作用以希夫碱反应为主。由于静电作用与交联键的引入,改性后胶原的热稳定性得到提升。随着温度的升高,纯胶原与改性胶原的特征吸收峰均发生红移且A_Ⅲ/A_{1 455}值不断降低,说明两者在升温过程中其氢键不断减弱,导致三股螺旋发生解旋,但与纯胶原相比,改性胶原特征吸收峰的红移程度与A_Ⅲ/A_{1 455}值降低幅度较小,证实了改性后胶原的热稳定性有所提高。胶原与改性胶原在升温过程中结构变化的分析结果表明：改性前后胶原二级结构的崩塌均表现为三股螺旋结构被破坏转变成无规卷曲结构;然而在测试温度范围内,三股螺旋结构对温度的敏感度及响应顺序发生明显变化：（1）对于纯胶原,对温度最为敏感的结构是胶原的螺旋结构,而改性胶原的无规卷曲结构是最为敏感的、最不敏感的结构是胶原螺旋结构,反映出改性后胶原的螺旋结构得到稳定;（2）改性后胶原螺旋结构对温度的响应发生滞后,进一步证实胶原的稳定作用主要归功于三股螺旋结构的加固。     

圆二色谱研究胶原模拟多肽三螺旋结构及其热稳定性

胶原是广泛研究和应用的生物材料,具有独特的三螺旋结构,此结构与其生物学性能密切相关。以胶原模拟多肽(collagen mimetic peptide, CMP) 作为胶原的模型分子,通过圆二色谱研究了CMP的三螺旋结构、热稳定性等随序列或长度的改变所发生的规律性变化。根据形成胶原三螺旋结构的重复序列(POG)_n及胶原上α₂β₁整合素识别位点序列GFOGER设计五种不同序列或长度的CMP,采用圆二色谱表征了CMP的三螺旋结构,并通过检测CMP的程序升温变性和程序降温复性过程中圆二色谱的变化,研究了CMP三螺旋结构的热变性过程、解链温度以及复性过程。实验结果显示,五种CMP室温下均以三螺旋结构的形式存在,CMP三螺旋结构的热稳定性随POG的个数增加而增强;不同于胶原,CMP三螺旋结构的热变性是可逆的,升温过程中三螺旋解聚(变性),降温过程又可重新组装(复性),复性过程有明显的“磁滞”现象。研究结果可为进一步研究胶原与CMP分子特征性的三螺旋结构形成规律以及基于CMP的人工类胶原生物材料的研究提供依据。     

基于荧光光谱技术研究胶原蛋白溶液中分子的聚集行为

对胶原分子聚集行为的研究,不仅能改善其理化特性,同时也为其在食品、组织工程和生物医药等领域的应用提供理论指导。基于胶原分子中苯丙氨酸(Phe)和酪氨酸(Tyr)的内源荧光特性,采用常规波长、同步荧光和二维(2D)荧光光谱技术研究了不同浓度和温度下胶原分子的聚集行为。研究结果表明：(1)在激发波长275 nm条件下,胶原分子仅在发射波长303 nm处出现了归属于Tyr的特征峰;选取波长差(Δλ)为15 nm的同步荧光扫描胶原分子,发现其在261和282 nm处出现了分别归属于Phe和Tyr的特征峰。(2)特征峰的荧光强度与胶原浓度呈现良好的线性关系,表明了基于常规波长和同步荧光光谱技术对胶原定量分析的可行性。(3)随着胶原浓度的增加,Tyr和Phe的含量逐渐增大,且胶原分子间距逐渐降低并聚集成纤维束,使得Tyr和Phe相互靠近并参与形成大量的氢键,从而导致荧光强度不断增大。然而随着温度的升高,荧光基团与溶剂碰撞的猝灭机会增大,且胶原分子中Tyr和Phe的荧光量子产率逐渐降低,同时胶原分子动能增大,其聚集体逐渐松散,其三股螺旋结构逐渐坍塌,Tyr和Phe参与形成的氢键被破坏,从而导致荧光强度随温度的升高不断降低。(4)275 nm常规波长的2D荧光光谱分析表明,胶原分子在297,303和310 nm处出现了相关峰,其中303 nm归属于Tyr,297 nm归属于胶原分子聚集过程中参与氢键形成的Tyr;310 nm可能归属于Tyr的激发态,其不断的蓝移形成稳定的基团,以便参与氢键的形成,从而促进了胶原分子的聚集。以浓度为外扰的基团响应顺序为303 nm>297 nm>310 nm;以温度为外扰的基团响应顺序为297 nm>310 nm>303 nm。(5)2D同步荧光光谱分析表明,随着胶原浓度和温度的升高,Phe均比Tyr优先响应。综上,采用常规波长、同步荧光光谱技术均能较好的研究胶原分子在不同浓度和温度下的聚集行为,且为胶原的定量分析提供了一种新的方法,但同步荧光光谱技术可将量子产率较低的Phe显现出来,体现了其具有窄化谱带和提升分辨率的优点。此外,结合2D荧光分析技术,可进一步研究胶原分子基团的响应顺序。     

无线电引信的超宽谱辐照效应及其防护

 探讨了超宽谱高功率微波对无线电引信的辐照效应、耦合机理和防护方法。利用超宽谱高功率微波辐照源对多姿态的无线电引信进行了辐照实验并对结果进行了分析，实验表明当引信和弹体的轴向与超宽谱高功率微波的电场极化方向一致时，引信最容易被引爆，辐照效应最明显。通过理论分析和辐照实验找出超宽谱高功率微波能量耦合机理为：引信和弹体上感应的瞬变电压通过引信电源电路传递到执行电路，瞬变电压上升率超过了电路中晶闸管的断态电压临界上升率，使晶闸管意外导通，导致引信误动作。在不影响引信工作特性前提下，采取增加防护器件和替换敏感器件的加固方法，可以提高引信抗干扰能力。采用综合防护加固方法可使引信在超宽谱高功率微波辐照下不再产生误动作，达到了防护加固的目的。     

微波场对Co／La2O3上的甲烷部分氧化制合成气的影响

考察了微波场对Ｃｏ／Ｌａ２Ｏ３上的甲烷部分氧化制合成气的催化活性及产物选择性的影响，为揭示微波场与物质之间的相互作用规律进行了有意义的探索，结果表明，微波辐照下的反应有如下特点；在达到相同的ＣＨ４转化率时，微波活化方式下催化剂床层温度远比常规加热低得多，且产物中Ｈ２和ＣＯ选择性明显高于后者，微波活化方式的优越性还表现为：当微波加热的温度等于或高于１０７３Ｋ时，甲烷的转化率高达９９．３％以上，Ｈ２Ｏ     

温度对鱼鳞胶原蛋白二级结构的影响

从草鱼鱼鳞中提取酶溶性胶原蛋白(PSC),通过SDS-PAGE电泳分析为典型Ⅰ型胶原蛋白且达到电泳纯。在此基础上利用傅里叶变换红外光谱(FTIR)、拉曼光谱(Raman)和圆二色谱(CD)研究了温度对鱼鳞胶原蛋白二级结构的影响。FTIR分析表明：鱼鳞胶原蛋白具有典型的胶原蛋白特征吸收带,酰胺Ⅰ、酰胺Ⅱ和酰胺Ⅲ带的特征吸收频率分别出现在1658,1552和1238cm-1处。随温度升高,酰胺A和酰胺B峰位向低波数移动,1658cm-1处吸收峰裂解成多个吸收峰;1552cm-1处的吸收峰在35℃微略红移,随后发生明显蓝移;1238cm-1处吸收峰随温度升高向低波数移动。在拉曼光谱中,胶原蛋白的酰胺Ⅰ、酰胺Ⅱ和酰胺Ⅲ带的特征吸收频率分别出现在1669,1557和1245cm-1处,都较红外光谱的波数高;此外,921和855cm-1处脯氨酸的特征谱峰在拉曼光谱中体现出来。圆二色谱分析表明,胶原蛋白溶液在221.6和204.4nm分别有一正、负峰,具有典型胶原蛋白三螺旋结构的特征圆二色谱峰型。胶原蛋白冻干品的FTIR光谱和Raman谱线大都在35～60℃时发生波数和强度改变,而胶原蛋白乙酸溶液的CD谱线在20～35℃之间发生剧烈改变。由此可以判断胶原蛋白在固态和溶液状态下,变性温度存在一定差异,胶原蛋白冻干品比其乙酸溶液更稳定。     

脉冲微波辐照影响心肌细胞膜蛋白构象及其机制的研究

应用显微傅里叶变换红外光谱技术研究了脉冲微波辐照对心肌细胞膜蛋白质构象、功能的影响和相关分子机制。结果表明,辐照可对心肌细胞的细胞膜蛋白质结构产生明显影响。细胞膜脂质中—CH₂—、磷脂结构中CO、蛋白质酰胺Ⅰ,Ⅱ带的伸缩振动峰消失或位移。辐照后心肌细胞膜蛋白质二级结构也出现明显变化,α-螺旋和β-折叠结构减少,二级结构无序化程度增加。上述变化均与辐照剂量呈正相关。结果提示受脉冲微波辐照后,心肌细胞膜蛋白构象的完整性受损,膜稳定性及流动性下降,膜上多种生物活性结构被破坏,上述变化构成了细胞膜功能丧失、细胞形态和结构损伤、细胞凋亡等病理学效应的生物化学基础。文章首次从蛋白质构象角度阐述了微波辐照对心肌细胞膜损伤的分子病理机制。     

Ultrasonic irradiation in the enzymatic extraction of collagen

The application of ultrasonic irradiation (40 KHz, 120 W) in the enzymatic extraction of bovine tendon collagen has been investigated. Our results show that using the ultrasonic irradiation increases the yield of collagen up to ～124% and significantly shortens the extraction time in comparison with the conventional pepsin isolation method. Such improvements are attributed to the enhancement of the enzyme activity and the dissolution of collagen substrate because the ultrasonic irradiation disperses the pepsin aggregates and opens up the collagen fibrils, thus the enzymatic hydrolysis is facilitated. AFM imaging shows the same fibrillar structure of tendon collagens generated from both the methods. The CD and FT-IR measurements reveal that the triple helix structure of collagen remains intact even after the ultrasonic irradiation. This study shows that the mild ultrasound irradiation can effectively improve the efficiency of pepsin extraction of natural collagen without any compromise of the resultant collagen quality.     

长波紫外辐射对Ⅰ型胶原损伤的拉曼光谱研究

应用拉曼光谱技术研究了长波紫外(Ultraviolet-A,UV-A)辐射对Ⅰ型胶原的损伤,检测了Ⅰ型胶原及其经过90min的UV-A辐射后的拉曼光谱,得到了一个较完整的Ⅰ型胶原紫外损伤机制。实验结果表明:90min的UV-A辐射导致Ⅰ型胶原分子内氢键断裂、氢键体系发生变化,肽链的螺旋度减少,逐渐解螺旋,无规卷曲等无序构象增加。此外,UV-A辐射使Ⅰ型胶原分子内脯氨酸的羟基化程度降低。这些变化必然会引起Ⅰ型胶原三螺旋结构的损伤,并导致皮肤光老化过程中组织内胶原纤维的破坏。     

Fourier transform of the collagen triple-helical structure and its significance

The Fourier transforms of the collagen molecular structure have been calculated taking into consideration various side chain atoms, as well as the presence of bound water molecules. There is no significant change in the calculated intensity distribution on including the side chain atoms of non-imino-acid residues. Taking into account the presence of about two bound water molecules per tripeptide unit, the agreement with the observed x-ray pattern is slightly improved. Fourier transforms have also been calculated for the detailed molecular geometries proposed from other laboratories. It is found that there are no major differences between them, as compared to our structure, either in the positions of peak intensity or in the intensity distribution. Hence it is not possible to judge the relative merits of the various molecular geometries for the collagen triple helix from a comparison of the calculated transforms with the meagre data available from its x-ray fibre pattern. It is also concluded that the collagen molecular structure should be regarded as a somewhat flexible chain structure, capable of adapting itself to the requirements of the different side groups which occur in each local region.     

二维红外相关光谱法研究温度对交联胶原结构的影响

采用傅里叶红外光谱和二维相关分析研究了改性前后胶原在升温(25～115℃)过程中结构的变化。结果显示,改性前后胶原的特征吸收峰强度降低,峰值向低波数移动,其中酰胺II带的变化最明显,降低了～10cm-1,表明维系胶原三股螺旋结构稳定的氢键被破坏,结构发生改变。在1 515cm-1处自相关峰强度最强,说明温度对酰胺II带的影响最大。与未改性胶原相比,改性胶原的相关程度更弱,表明改性胶原结构受温度影响要小,交联提高了胶原的热稳定性;改性后胶原结构变化的顺序也不一样。由此可见,二维红外相关分析法能提供由温度引起的胶原结构动态变化的微观信息,对进一步研究改性胶原结构和功能之间的关系有一定的意义。     

Study of electret effect of rat skin by thermally stimulated discharge analysis

The thermally stimulated discharge (TSD) spectra of three types of rat skin treated and untreated by negative polypropylene (PP) electret were measured. The natural rat skin shows an excellent electret effect due to the lamellar lipid structure, reticular structure of collagen and protein space structure related hydrogen bond network and non-covalent bond system. Hydration intensifies the skin electret effect. Electret could change the lamellar lipid structure and charge state of skin surface by alteration of dipolar orientation, intermolecular non-covalent action and protein transformation from α helix to β sheet. The regulation of skin electret effect depends on tightly bound water.     

Improvement of Structural,Rheological, and physicochemical properties of type I collagen by calcium lactate combined with ultrasound

Type I collagen has a relatively stable quality while quite resistant to digestion because of the complex triple helix structure. This study was conducted to explore the acoustic conditions of ultrasound (UD)-assisted calcium lactate processing of collagen and control the processing process through its sono-physico-chemical effects. The findings demonstrated that UD might lower the average particle size of collagen and increase its zeta potential. In contrast, the rise in calcium lactate concentration could dramatically limit the impact of UD processing. This may be because of its low acoustic cavitation effect, as demonstrated by the phthalic acid method (the fluorescence value decreased from 81245.67 to 18243.67). Poor changes in tertiary and secondary structures confirmed the detrimental effect of calcium lactate concentration on UD-assisted processing. Although UD-assisted calcium lactate processing can significantly alter the structure of collagen, the integrity of the collagen is basically preserved. Furthermore, the addition of UD and a trace amount of calcium lactate (0.1%) increased the roughness of the fiber structure. At this relatively low calcium lactate concentration, ultrasound improved the gastric digestibility of collagen by nearly 20%.     

Improvement of gelation properties of silver carp surimi through ultrasound-assisted water bath heating

The present work investigated the effects of water bath heating coupled with different ultrasound treatments on the gel properties, protein conformation, microstructures and chemical interactions of silver carp surimi at low/high salt levels. Results showed that the gel strength, hardness, springiness and water holding capacity (WHC) of surimi gels at low salt concentration were inferior to those at high salt content, regardless of the treatments. Compared with the traditional water bath heating, ultrasonic-assisted treatments significantly improved the gelation properties of surimi at the same salt level. In fact, ultrasound treatment also facilitated the unfolding of α-helix structure of the protein, with the resulting exposure of internal groups further enhancing hydrophobic interactions and hydrogen bonds between protein molecules, thereby leading to the formation of denser microstructures with smaller holes. Furthermore, the most noteworthy ultrasonic treatment group was ultrasound-assisted preheating (U + W) group, whose gelation performance under low salt condition, was comparable with that of the traditional two-stage heating (W + W) group with high salt content. Overall, ultrasound-assisted water bath preheating proved to be a feasible approach to improve the gel properties and microstructures of low-salt surimi gels.     

Optically detected cyclotron resonance in a high mobility 2D electron gas

We study the properties of high mobility GaAs/GaAlAs quantum well structure by monitoring the microwave induced changes in the low-temperature photoluminescence of the 2DEG as a function of the external magnetic field. The most pronounced changes are observed at cyclotron resonance conditions, but weak features are also visible at cyclotron resonance replicas. Possible observation of microwave induced shift in the Landau-level structure of magneto-photoluminescence is reported in addition to the effects of carrier heating which are conventionally bracketed together with microwave irradiation.