Modified Cyclodextrins as Enantioselective Hosts for Amino Acids

Two modified β‐cyclodextrins, H‐2 and H‐3 , having a flexible appended moiety were studied for the chiral discrimination of the enantiomers of various amino acids by means of fluorescence as signaling option. These hosts quenched the fluorescence intensities of amino acids upon binding. The d‐ enantiomers were better recognized by these hosts. The association constants (K_s) and enantioselectivity factors (α) of the host?guest complexes were calculated.     

An integrated strategy for the geographical origin traceability of Goji berries by antioxidants characteristic fingerprint based online ultra-performance liquid chromatography-2,2-diphenyl-1-picrylhydrazyl- photodiode array detector-mass spectrometry combined with multivariate statistics analysis

Goji berries are now becoming increasingly popular in the human diet due to their potential health benefits. Unscrupulous traders deliberately mislabel with certain origins to gain illegal profits, which seriously affected the consumers’ benefits. In this study, an online ultra-performance liquid chromatography-2,2-diphenyl-1 -picrylhydrazyl-photodiode array detector-electrospray ionization-quadrupole time of flight mass was developed for rapid screening and identification of the antioxidants from Goji berry; then, the antioxidants characteristic fingerprint was established and explored in the origins discrimination of Goji berries from China combined with multivariate statistics analysis. As a result, twenty-eight compounds were screened from Goji berry extract, 19 of which were identified by accurate molecular and ultraviolet information according to references. Principal components analysis and partial least squares discrimination analysis achieved the accurate classification from the four regions, eight compounds were selected as origin-related antioxidant markers with variable importance in projection >1 and one-way analysis of variance (P<0.05), including rutin, rutin di-hexose, P-coumaric acid tri-hexose, dicaffeoylquinic acid isomer, Quercetin-rhamno-di-hexoside, peak14, peak16, and peak27. This study provides a feasible strategy for the geographical origins discrimination of Goji berries based on antioxidant ingredients difference and will be helpful for improving the quality control level of Goji berries.     

Micro Electrical Impedance Spectroscopy (μEIS) Fabricated on the Curved Surface of a Fine Needle for Biotissue Discrimination

This work presents a novel micro electrical impedance spectroscopy (μEIS) technique that can measure and discriminate the electrical signal responses of biotissues in real time. An EoN (EIS‐on‐a‐needle), EIS on the surface of a fine needle (400 μm in diameter), was fabricated using a newly developed flexible photomask film. The base material of the photomask is parylene‐C, which allows uniform contact on the curved surface of the needle; thus, the designed electrode patterns of the photomask can be transferred onto the needle surface with a high resolution (2.95 % or less in dimensional error). To validate the developed EoN as an electrical sensor, ex vivo experiments with various biotissues—butchered pork (skin, fat, and muscle) and human breast tissues (normal and cancerous)—were conducted by measuring real‐time electrical impedance during a frequency sweep. The conductivities (relative permittivity) of the pork tissues were evaluated by electrical equivalent circuit analysis: 56.6 mS/m (37,800), 68.0 mS/m (74,755), and 74.9 mS/m (26,145) for the skin, fat, and muscle, respectively. Moreover, the normal and cancerous tissues were well distinguished by electrical resistance at 4.04 kHz for various cancer grades (Elston grades 1, 2, and 3). Analysis of the electrical impedance suggests that the EoN can be utilized to diagnose the physiological states of biotissues in clinical use.     

Neutron light output function and resolution investigation of the deuterated organic liquid scintillator EJ-315

In this paper we investigate the light response to fast neutrons and estimate the pulse height resolution of a deuterated liquid organic scintillator, EJ-315, considering the detector's non-linear light response to gamma-rays. Initially, collision data and a neutron beam trigger are recorded in coincidence mode, and incident neutron energy is calculated with a time-of-flight technique. Fast neutrons are further discriminated from gamma-ray background based on the scintillation material decay patterns using a pulse shape discrimination algorithm. A light response matrix composed of multiple neutron energy and their corresponding light outputs is derived. The pulse height resolution property of the EJ-315 is characterized utilizing the derivatives of the pulse height distributions with corrections of the measurements setup uncertainties. Additionally, the EJ-315's pulse height resolution is also characterized by comparing the smoothed derivatives of quasi-monoenergetic neutron pulse height distributions, given by the Peierls-formula-based analytic model, to match the measurement data. Results show rather consistent 10–13% pulse resolution for mono-energetic neutrons with kinetic energy above 2 MeV. The resolution decreases slightly with an increase in neutron energy indicating the improved resolution performance of EJ-315 in the higher energy events.     

Fingerprint developing of coffee flavor by gas chromatography-mass spectrometry and combined chemometrics methods

In this paper, chromatographic fingerprint was firstly used for quality control of tobacco flavors. Based on gas chromatography-mass spectrometry (GC-MS) and combined chemometrics methods, a simple, reliable and reproducible method for developing chromatographic fingerprint of coffee flavor, one of tobacco flavors, was described. Six coffee flavor samples obtained from different locations were used to establish the fingerprint. The qualitative and quantitative analysis of coffee flavor sample from Shenzhen was completed with the help of subwindow factor analysis (SFA). Fifty-two components of 68 separated constituents in coffee flavor sample from Shenzhen, accounting for 88.42% of the total content, were identified and quantified. Then, spectral correlative chromatography (SCC) was used to extract the common peaks from other five studied coffee flavor samples. Thirty-eight components were found to exist in all six samples. Finally, the method validation of fingerprint analysis was performed based on the relative retention time and the relative peak area of common peaks, sample stability and similarity analysis. The similarities of six coffee flavor samples were more than 0.9104 and showed that samples from different locations were consistent to some extent. The developed chromatographic fingerprint was successfully used to differentiate coffee flavor from coco flavor and some little difference sample prepared with coffee flavor and coco flavor by both similarity comparison and principal component projection analysis. The developed method can be used for quality control of coffee flavor.     

Arbitrary-norm hyperplane separation by variable neighbourhood search

^** Email: alejandro.karam{at}hec.ca^*** Email: gilles.caporossi{at}gerad.ca^**** Email: pierre.hansen{at}gerad.ca We consider the problem of separating two sets of points ina Euclidean space with a hyperplane that minimizes the sum ofp-norm distances to the plane of points lying on the ‘wrong’side of the plane. A variable neighbourhood search heuristicis used to determine the plane coefficients. For a set of exampleswith L₁-norm, L₂-norm and L-norm, for which the exact solutioncan be computed, we show that our algorithm finds it in mostcases and gets good approximations in the others. The use ofour heuristic solutions for problems in these norms can dramaticallyaccelerate exact algorithms. Our method can be applied on verylarge instances that are intractable by exact algorithms. Sincethe proposed approach works for truly arbitrary norms (otherthan the traditional 1, 2 and ), we can explore for the firsttime the effects of the choice of p on the generalization propertiesof p-norm hyperplane separation.     

叶黄素的几类降解反应研究

类胡萝卜素是一大级一泛存在于动植物体内的四储类化合物,它们不仅颜色鲜艳,也是一类重要香味物质的前体。在Ｍ的烟０－Ｉ中已有１８种类型的胡萝卜素被分离和日表征。其中卜胡萝卜素和叶黄素是主要成分ｌ‘］。烟叶采收后,类胡萝卜素经生物降解,会生成一系列有挥发性芳香化合物,它什对卷烟的吸味、品质有很大的影响Ｉ２］。本文设计了四种化学方法,对叶黄素进行氧化降解,产物用ＧＣ／ＭＳ进行检测。结果表明,在适当条件下对叶黄素进行化学法氧化降解,可以得到如：氢化异佛尔酮、环氧紫萝兰酮、二氢弥猴桃内＠纺ｏ茶香螺酮等有重要…     

New approaches to chiral discrimination in coupling between molecules

Results in the coupling of chiral molecules are reviewed from elementary points of view and some new results are given. We show that interactions between chiral molecules can be treated by using molecular quantum electrodynamics in electric and magnetic dipole approximation in ways different from standard diagrammatic perturbation theory. The interactions are the dispersive coupling of ground-state chiral molecules and excitation transfer, with emphasis on chiral discrimination. For ground-state molecules the coupling is dealt with first by calculating the coupling, at all separation distances, of electric and magnetic dipoles induced in the two molecules by fluctuations in the vacuum radiation field. The second method is the response by one chiral molecule to the field generated by the other. Excitation transfer is treated as the response by the accepting ground-state molecule to the dipole field of the donor. A novel variant in finding the rate of excitation transfer is by using Poynting's theorem. Received: 17 June 1998 / Accepted: 6 October 1998 / Published online: 16 March 1999     

A “quasi‐flexible” automatic docking processing for studying stereoselective recognition mechanisms. Part I. Protocol validation

The main purpose of this work is the development and validation of a general scheme based on a systematic and automatic “quasi‐flexible” docking approach for studying stereoselective recognition mechanisms. To achieve our goals we explore the conformational and configurational space for small‐ or medium‐size flexible molecules in a systematic way, seeking a method that is both reasonably accurate and relatively fast from the computational point of view. In particular, we have developed a general computational protocol for the global molecular interaction evaluation (“Glob‐MolInE”) to efficiently explore the orientational and conformational space of flexible selectors and selectands used in modern chiral high‐performance liquid chromatography (HPLC); the enantioselective binding of the selector (S)‐N‐(3,5‐dinitrobenzoyl)‐leucine‐ n‐propylamide (S)‐ 1 towards the selectand N‐(2‐naphthyl)‐alanine methyl ester 2 has been studied; the global minimum obtained for the homochiral associate [S( 1 )/S( 2 )] (Pop. >99%) is very close (RMS≃0.20) to the crystallographically determined structure. © 2000 John Wiley & Sons, Inc. J Comput Chem 21: 515–530, 2000     

近红外光谱LASSO特征选择方法及其聚类分析应用研究

近红外光谱技术是一种通过分析样本的特征光谱数据,实现定性或定量分析的无损检测方法,特征数据的完整性和代表性决定了所建模型的性能,而现有分析方法只能实现光谱子区间特征筛选,导致分析模型稳定性差、且难以再优化。为实现近红外光谱区间高维数特征提取,有效提高近红外光谱定性分析模型的精度和稳定性,提出一种基于最小绝对收缩和选择算法(LASSO)的光谱特征筛选方法,并以我国特色高值外贸产品云南松茸为分析对象进行聚类应用研究,讨论了该方法对于高维光谱特征筛选的有效性、分析对比了LASSO筛选特征变量及主元分析(PCA)降维算法所建松茸真伪甄别及食用菌分类模型的预测精度及稳定性。通过调研发现,云南产鲜松茸因其独特外形易于分辨,而片状的干松茸失去其独有的外形特征,导致国内干松茸掺假事件屡禁不止。选取云南产松茸、杏鲍菇、老人头、姬松茸四种干样共166样本数据进行分析,采用光谱范围为900～1 700 nm的NIRQuest512型近红外光谱仪获得166×512维原始光谱数据,剔除异常数据后采用标准正态变换对光谱数据进行预处理。在此基础上,利用LASSO筛选出全光谱区间的特征变量,再使用Kennard-Stone法并结合典型线性(KNN)和非线性建模(BP)算法,构建松茸真伪甄别模型和食用菌分类模型,对两种模型进行盲样测试,并分析了LASSO与PCA算法的不同点,最后使用蒙特卡罗方法检测两种模型的稳定性。实验结果表明基于LASSO光谱特征选择的松茸真伪甄别模型和食用菌分类模型预测精度和稳定性均高于PCA方法,其中基于原始光谱数据所建真伪甄别模型的预测准确率为69.57% (BP)和60.87% (KNN),食用菌分类模型准确率为67.39% (BP)和65.22% (KNN),基于LASSO特征筛选的真伪甄别模型预测准确率分别达到100% (BP)和78.26% (KNN),食用菌分类模型预测准确率分别达到89.13% (BP)和80.43% (KNN),对两种模型进行10次蒙特卡罗实验,其结果平均值分别为99.93%和97.22%,由此可知,与PCA等数据降维算法相比,LASSO可实现全光谱区间的光谱特征选择和数据降维,有效地提高了近红外定性分析模型的预测性能,为近红外分析提供了一种新的特征筛选方法。