Rapid Characterization of Molecular Diffusion by NMR Spectroscopy

An NMR‐based approach for rapid characterization of translational diffusion of molecules has been developed. Unlike the conventional method of acquiring a series of 2D ¹³C and ¹H spectra, the proposed approach involves a single 2D NMR spectrum, which can be acquired in minutes. Using this method, it was possible to detect the presence of intermediate oligomeric species of diphenylalanine in solution during the process of its self‐assembly to form nanotubular structures.     

Automated classification of multispectral MR images using unsupervised constrained energy minimization based on fuzzy logic

Constrained energy minimization (CEM) has proven highly effective for hyperspectral (or multispectral) target detection and classification. It requires a complete knowledge of the desired target signature in images. This work presents “Unsupervised CEM (UCEM),” a novel approach to automatically target detection and classification in multispectral magnetic resonance (MR) images. The UCEM involves two processes, namely, target generation process (TGP) and CEM. The TGP is a fuzzy-set process that generates a set of potential targets from unknown information and then applies these targets to be desired targets in CEM. Finally, two sets of images, namely, computer-generated phantom images and real MR images, are used in the experiments to evaluate the effectiveness of UCEM. Experimental results demonstrate that UCEM segments a multispectral MR image much more effectively than either Functional MRI of the Brain's (FMRIB's) automated segmentation tool or fuzzy C-means does.     

天然产物的质谱研究V.负离子快原子轰击及其碰撞活化质谱法在寡糖苷结构分析中的应用

研究了八种含1一3个糖基的糖苷的负离子快原子轰击(NFAB)质谱,NFAB质谱与相应的正离子谱(PFAB)比较,在高质量区示出较明显的准分子离子[M-H][-]峰而无加合离子峰,从而能较明确指示糖苷的分子量, 在所试验的三种底物甘油、硫代甘油和聚乙二醇-200(PEG-200)中,以PEG-200给出的结果最佳,[M-H][-]离子的碰撞活化谱(NFAB-CA谱)产生的特征离子比[M+H][+]离子PFAB-CA谱中相应离子的丰度大,能更为明确地给出糖基连接顺序信息。     

2,3-二烷氧基-5-烷氧羰基苄基胺羧酰胺螯合剂的快原子轰击质谱研究

本文报道了运用快原子轰击电离以及快原子轰击-联动扫描方法对2,3-二烷氧基-5-烷氧羰基苄基胺羧酰胺螯合剂的质谱研究, 阐明了它们的裂解途径, 并以此对它和铁离子相螯合后螯合部位进行推测. 结果表明快原子轰击电离方法为金属配合物的研究提供了一种新的手段.     

Potential of front face fluorescence associated to PLS regression to predict nutritional parameters in heat treated infant formula models

This work shows that front face fluorescence spectroscopy associated to partial least squares (PLS) calibration is a fast and simple method to assess the nutritional impact of heat treatment on milk samples.Emission spectra of tryptophan (Trp) and of advanced Maillard products (AMP) were recorded on intact milk samples non-heated and heated at seven temperatures (72 °C, 80 °C, 87 °C, 95 °C, 100 °C, 110 °C and 115 °C) for six different times (from 2 min to 9.5 min) by means of front face fluorescence. PLS calibrations were constructed in order to indirectly quantify three indicators: vitamin C, protein denaturation and accumulation of Maillard products using the fluorescence of advanced Maillard products and soluble tryptophan method (FAST). The prediction models allowed obtaining an estimation of these indicators with a relative error of 12% for vitamin C and about 18% for the FAST index and soluble whey protein ratio.     

Baylis-Hillman反应的研究进展

介绍子一种形成碳碳键的方法－Baylis-Hillman反应及其研究的最新进展。为克服常见Baylis-Hillman反应反应速度慢的缺点,近来人们发展了许多加快反应速度的方法。运用手性底物或手性催化剂等方法来进行不对称Baylis-Hillman反应从而获得手性Baylis-Hillman加成产物。     

大射电望远镜馈源舱的风激振动及其MTMD减振设计研究

采用修正的Davenport风谱来模拟风荷 ,分析了FAST (Five -hundred -meterApertureSphericalTelescope)大射电望远镜馈源舱在该风荷作用下的振动 ,并根据分析和计算的结果设计了多频调谐质量阻尼器 (MultipleTunedMassDampers) ,计算结果表明 ,这种动力吸振阻尼器可以有效地减少馈源舱的振动     

快原子轰击和碰撞活化质谱法研究三萜皂苷结构

本文用快原子轰击(FAB)和碰撞活化(CA)相配合的方法测定了含3-5个糖基的三萜皂苷的结构.FAB谱能给出分子量信息,由质子化分子的CA谱可推测糖基连接序列.本法的优点在于难挥发,热不稳定的样品可直接进样分析不需制成挥发性衍生物,且样品中杂质经磁场进行质量分离后影响CA谱.本法的局限性在于不能区别糖的立体异构体和确定各糖基或糖基与苷元的连接位置.     

糖苷混合物FAB质谱分析技术的研究

我们曾阐明了糖苷单-化合物分子量的简明, 快速确定方法, 根据糖苷化合物中引入碱金属离子的FAB正离子的加合离子峰而难于找到碎片的加合离子峰, 现在我们在糖苷混合物中, 同时引入两种碱金属离子Na^+和Li(两元素原子量之差为16), 由此得到的糖苷混合物的FAB正离子谱中, 就出现两个一组的多组强峰, 且每组的两峰之质量差为16, 每组中低质量峰为[M+Li]^+峰, 高质量为[M+Li]^+峰, 根据两峰已标出的质量数便可轻易地定出各成分的分子量来。谱图中出现的强峰组数就是糖苷混合物的成分数。     

东亚马氏钳蝎哺乳动物类神经毒素III的快原子轰击酶谱分析

应用快原子轰击酶谱分析检验了东亚马氏钳蝎哺乳动物类神经毒素III的氨基酸序列,对前人用Edman降解法测定的序列作了两处修正:(1)第60位氨基酸残基是脯氨酸而不是色氨酸;(2)C-端氨基酸是组氨酸而不是甘氨酸。分别用羧肽酶B降解和部分胰蛋白酶酶解后的质谱数据进一步证实了以上的修正。在分析中采用了化学修饰方法以减少表面抑制效应,从而得到完整的快原子轰击酶谱。