二硫化碳氧化性自由基对生物靶分子损伤机理研究

利用脉冲辐解技术研究了二硫化碳（CS2）被氧化生成的阳离子自由基，以时间分辨瞬态吸收光谱方法获取CS2阳离子自由基的特征吸收谱，同时，研究了CS2阳离子自由基损伤生物靶分子的机理，测定了相关的反应动力学常数。结果发现，CS2阳离子自由基能与DNA、dGMP、酪氨酸和色氨酸反应产生亲的产物，在CS2对生物靶分子的氧化损伤中可能起着重要的作用。     

Natural Products Isolated From Species of Halgerda Bergh, 1880 (Mollusca: Nudibranchia) and Their Ecological and Evolutionary Implications

Chemical investigations of five species of molluscan nudibranchs, Halgerda, collected from Australia and Japan were carried out. We identified a novel tryptophan derivative halgerdamine (1) along with the known compounds trigonellin (3), esmodil (4), zooanemonin (5), and C2-α-D-mannosylpyranosyl-L-tryptophan (2) from Halgerda aurantiomaculata. C2-α-D-mannosylpyranosyl-L-tryptophan (2) was previously thought to be a by-product of tryptophan metabolism exclusive to humans. The only other chordates reported to contain this compound are a number of ascidian species from New Caledonia and Australia including Atriolum robustum and Leptoclinides dubius. The occurrence of 2 in a mollusc has not been previously reported. Structure elucidation of 1 was achieved by using high-field 2D NMR spectroscopy. No secondary metabolites were detected in extracts from five of the six other species studied, whereas Halgerda gunnessi contained mixtures of acylated tetrasaccharides. The compounds isolated from Halgerda are different from those found in the close sister taxon, Asteronotus. Specifically, species of Halgerda contain no terpenes, spirodysin, or bromophenols, as does Asteronotus. Furthermore, in contrast to other members of the Nudibranchia such as Chromodoris and Phyllidia, in which compound yields are quite high, several cryptic species of Halgerda seem to lack secondary metabolites, whereas the two highly conspicuous species yield mildly cytotoxic MeOH extracts. Our findings support recent hypotheses regarding progressive evolution of opisthobranchs. In particular, opisthobranchs have evolved to exploit a wider range of food and metabolites than did their ancestors, a demonstration of physiological innovation. Some species of Halgerda may not be chemically protected either via de novo synthesis or by sequestering particularly toxic compounds.     

色氨酸在自制牛血清白蛋白手性柱上的拆分

利用三氯聚氰活化的氨丙基硅胶与牛血清白蛋白反应,快速而经济地制得牛血清白蛋白手性固定相。在反相模式下,将该手性固定相用于色氨酸的拆分,系统探讨了流动相pH值、柱温、有机修饰剂的种类及含量等对手性拆分的影响。色氨酸在自制牛血清白蛋白手性柱上得到了理想的拆分,分离因子可达4.33。     

Sarcomere length determination using front-face fluorescence polarization

Tryptophan is the major intrinsic fluorophore in muscle and is a constituent of proteins that have two preferential alignments both parallel and perpendicular to muscle fibre direction. A simple theoretical model and an experimental method based on front-face fluorescence polarization technique for tryptophan fluorescence anisotropy measurements were used for the estimation of post-rigor sarcomere length in beef in the range 1.6-3.4μm. Fluorescence anisotropy and structure-related model variables displayed changes in cold-shortened samples compared with normal and stretched ones. The anisotropy of contracted samples was lowered by misalignment of fibres in the sample. This method can therefore be used for in-line detection of cold shortening which has meat toughness as a consequence.     

Insight of corrosion mitigation performance of SABIC iron in 0.5 M HCl solution by tryptophan and histidine: Experimental and computational approaches

The inhibitory strength of two amino acids namely, tryptophan (Tryp) and histidine (Hist) on the corrosion of SABIC iron (SABIC Fe) in a 0.5 M HCl solution was examined utilizing mass loss (MS), electrochemical (PDP and EIS) and theoretical studies. Density functional theory (DFT) and Monte Carlo (MC) simulation were inspected for Tryp and Hist inhibitors. All the corrosion parameters and theoretical data obtained from these studies confirm the inhibiting impact of the two amino acids. The efficacy of inhibition augment with augmentation the concentration of two amino acids from 100 to 500 ppm and reducing at elevated temperature. The effectiveness of the inhibition depends on the presence of some active centers that accelerate the adsorption process and the molar mass of the inhibitors. The inhibition efficacy of Tryp is greater than that of Hist reaching 92.09% at a concentration of 500 ppm while in the presence of Hist it is 89.37% using PDP measurements. Inhibition was demonstrated by spontaneous adsorption of Hist and Tryp on the surface of SABIC Fe according to the Langmuir adsorption isotherm. PDP curves clarified that the Tryp and Hist compounds acted as mixed type inhibitors. A variety of thermodynamic and kinetics parameters were computed and explained. SEM images demonstrate that the protective layer constructed on the surface of S– Fe in the presence of both amino acids. The results obtained from DFT are in complete agreement with the experimental work. Tryp and Hist compounds are adsorbed horizontally onto the surface of Fe (110).     

磷酰化甲硫氨酸与色氨酸之间电子转移的脉冲辐解研究

用脉冲辐解动态吸收光谱法研究了Ｂｒ２＾－、Ｃｌ２＾－自由基引发Ｎ－二异丙基磷酰化甲硫氨酸与色氨酸的分子间电子转移机理，测定电子转移反应的速率常数，从分子结构观点解释了磷酰基对电子转移机理的影响。     

Monitoring aerobic sludge digestion by online scanning fluorometry

With sludge samples from two wastewater treatment plants, batch experiments of aerobic sludge digestion were conducted under different dissolved oxygen (DO) and solids concentrations. A fluorometer capable of online excitation and emission scanning was used to monitor the digestion process. Three major fluorescence peaks were observed. The peak at excitation/emission maxima of 290/350 nm was attributed to the fluorescence of proteinaceous materials in the sludge, with tryptophan residues being the primary contributor. The sources for the other two peaks (at 370/430 nm and 430/510 nm) remain unknown. The well-known biological fluorescence from reduced nicotinamide adenine dinucleotides (NADH and NADPH), at excitation/emission maxima of 340/460 nm, was found very weak in the aerobic digestion systems studied. It was buried under the broad peak at 370/430 nm and was detectable only in the early stage of the experiment that had the highest solids loading (at 4.8%) and was operated under low DO (0.2-1.0mg/L) conditions. On the other hand, the profile of the protein fluorescence (PF) correlated well with that of the volatile solids (VS) reduction in all the experiments. A semi-empirical exponential decay function was developed, which described well the profiles of both normalized VS and normalized PF. The feasibility of following the real-time performance of aerobic sludge digestion by monitoring PF was clearly demonstrated.     

Thermal and dielectric properties of newly developed L-tryptophan-based optically active polyimide and its POSS nanocomposites

A new chiral diamine L-methyl-2-[(3,5-diaminobenzoyl)amino]-3-(1H-indol-3yl)propanoate was synthesized using L-tryptophan (essential amino acid) as starting material. The structure of the synthesized diamine was supported by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (¹H and ¹³C-NMR) and mass spectral techniques. The diamine was polymerized with 3,3’,4,4’-benzophenone tetracarboxylic dianhydride via thermal imidization method to produce thermally stable chiral polyimide (PI) with low dielectric constant. Additionally, polyimide nanocomposites were also prepared by incorporating amino functionalized polyhedral oligomeric silsesquioxane (POSS) into the PI matrix. The polyimide and PI/POSS nanocomposites were characterized by FT-IR spectroscopy. The PI was found to have specific optical rotation of –41.4°. The inherent viscosity was found to be 0.77 dLg^?1 indicating that a high molecular weight PI was formed. Surface morphology of the neat PI and nanocomposites was studied by scanning electron microscopy, transmission electron microscopy and atomic force microscopy (AFM) that reveal uniform distribution of the nanoparticles in the PI matrix. DSC analysis indicates that the T_g of the PI and its nanocomposites are in the range of 222–250 °C. The T_10% was found to be in the range of 402.4–470.5 °C for the PI and its nanocomposites. The dielectric constant values are in the range of 3.5–2.1.