New diagnostic of the most populated conformer of tetrahydrofuran in the gas phase

The most populated conformer of tetrahydrofuran (C(4)H(8)O) has been diagnosed as the Cs conformer in the present study, jointly using experimental electron momentum spectroscopy (EMS) and quantum mechanics. Our B3LYP/6-311++G** model indicates that the C1 conformation, which is one of the three possible conformations of tetrahydrofuran produced by pseudorotation in the gas phase, is a transition state due to its imaginary frequencies, in agreement with the prediction from a recent ab initio MP2/aug-cc-pVTZ study (J. Chem. Phys. 2005, 122, 204303). The study has identified the fingerprint of the highest occupied molecular orbital (HOMO) of the C(s) (12a') conformer as the most populated conformer. The identification of the C(s) structure, therefore, leads to the orbital-based assignment of the ionization binding energy spectra of tetrahydrofuran for the first time, on the basis of the outer valence Green function OVGF/6-31G* model and the density functional theory (DFT) SAOP/ET-PVQZ model. The present study explores an innovative approach to study molecular stabilities. It also indicates that energetic properties are not always the most appropriate means to study conformer-rich biological systems.     

Comparison of stationary phases for packed column supercritical fluid chromatography based upon ionic liquid motifs: a study of cation and anion effects

A class of stationary phases for packed column supercritical fluid chromatography (SFC), referred to as immobilized ionic liquids (IILs), is evaluated with a two-part study: (1) a cation effect study and (2) an anion effect study. The former study compares six different IILs (tripropylphosphonium, tributylphosphonium, methyl-imidazolium, benzyl-imidazolium, triphenylphosphonium, and 4,4′-bipyridyl) on silica gel, evaluating their performance in SFC with all the counter anions as trifluoroacetate (TFA⁻). In the latter study, the stationary phase consisted of a bonded tributylphosphonium cation and varying counter anions (acetate, TFA⁻, chloride, NTf₂⁻, and perchlorate). An order of retentivity was established for the cation effect study, and the favorable behavior of phosphonium-based stationary phases is reported for the first time in SFC. It was not possible to always assign a retentivity order for the anion effect study, but wide variations in selectivity are noted for different anions showing the tunable nature of this class of stationary phases.     

Experimental and theoretical electron momentum spectroscopic study of the valence electronic structure of tetrahydrofuran under pseudorotation

The most populated structure of tetrahydrofuran (THF) has been investigated in our previous study using electron momentum spectroscopy (EMS). Because of the relatively low impact energy (600 eV) and low energy resolution (DeltaE = 1.20 eV) in the previous experiment, only the highest occupied molecular orbital (HOMO) of THF was investigated. The present study reports the most recent high-resolution EMS of THF in the valence space for the first time. The binding energy spectra of THF are measured at 1200 and 2400 eV plus the binding energies, respectively, for a series of azimuthal angles. The experimentally obtained binding energy spectra and orbital momentum distributions (MDs) are employed to study the orbital responses of the pseudorotation motion of THF. The outer valence Greens function (OVGF), the OVGF/6-311++G** model, and density function theory (DFT)-based SAOP/et-pVQZ model are employed to simulate the binding energy spectra. The orbital momentum distributions (MDs) are produced using the DFT-based B3LYP/aug-cc-pVTZ model, incorporating thermodynamic population analysis. Good agreement between theory and experiment is achieved. Orbital MDs of valence orbitals exhibit only slight differences with respect to the impact energies at 1200 and 2400 eV, indicating validation of the plane wave impulse approximation (PWIA). The present study has further discovered that the orbital MDs of the HOMO in the low-momentum region (p < 0.70 a.u) change significantly with the pseudorotation angle, phi, giving a v-shaped cross section, whereas the innermost valence orbital of THF does not vary with pseudorotation, revealing a very different bonding mechanism from the HOMO. The present study explores an innovative approach to study pseudorotation of sugar puckering, which sheds a light to study other biological systems with low energy barriers among ring-puckering conformations.     

Evaluation of compatibility of tablet excipients and novel synthesized polymer with lamivudine

The present study describes compatibility of anti-HIV drug lamivudine with various selected excipients and a novel synthesized polymer, for the development of its controlled release formulation. Differential scanning calorimetry (DSC), isothermal stability study (ISS) and Fourier transform infrared (FT-IR) spectral analysis were performed to access the compatibility. The compatibility study was performed with various common excipients like spray dried lactose, polyvinyl pyrrolidine K-30, magnesium stearate, talc and a novel synthesized polymer cross-linked sago starch with lamivudine.     

盐酸左氧氟沙星与替硝唑联用对慢性盆腔炎的治疗效果评价

目的观察替硝唑联合盐酸左氧氟沙星治疗慢性盆腔炎的治疗效果。方法将天津河北区妇产科医院诊治的慢性盆腔炎患者随机分为研究组与对照组,对照组使用左氧氟沙星进行治疗,研究组替硝唑联合盐酸左氧氟沙星对患者进行治疗,对比两组的治疗效果与不良反应。结果经过治疗,研究组总有效率为93.3%,明显高于对照组83.3%(P0.05);研究组不良反应率5.0%低于对照组13.3%(P0.05)。结论替硝唑联合盐酸左氧氟沙星对于慢性盆腔炎患者来说,具有疗效好、安全性较高、不良反应较少等特点。     

Complementary use of inter-laboratory certification study data

The agreed purpose of an inter-laboratory certification study is to characterise a certified reference material (CRM). In addition to this, any (successful) certification study may also be utilised as a laboratory/method performance study by the participants. The intention of this note is to emphasise the complementary use of certification study data by the participants of the certification study and to explain the options involved. On this occasion, an apparent paradox arising in the interpretation of certification study data is resolved. The procedures for bias correction and estimation of bias-related uncertainty contributions discussed on this occasion are, however, generally applicable to normal CRM use. Received: 4 February 1999 / Revised: 16 July 1999 / Accepted: 21 July 1999     

Complementary use of inter-laboratory certification study data

The agreed purpose of an inter-laboratory certification study is to characterise a certified reference material (CRM). In addition to this, any (successful) certification study may also be utilised as a laboratory/method performance study by the participants. The intention of this note is to emphasise the complementary use of certification study data by the participants of the certification study and to explain the options involved. On this occasion, an apparent paradox arising in the interpretation of certification study data is resolved. The procedures for bias correction and estimation of bias-related uncertainty contributions discussed on this occasion are, however, generally applicable to normal CRM use. Received: 4 February 1999 / Revised: 16 July 1999 / Accepted: 21 July 1999     

Evaluation of The Peak Capacity of Various RP-Columns for Small Molecule Compounds in Gradient Elution

Peak capacity is the commonly used measure of separation efficiency in gradient elution. This study focuses on the effect of column characteristics (particle size and column length) and operating parameters (gradient time and flow rate) on the peak capacity for small molecule compounds in gradient elution. The goal of this study is to develop a practical strategy to maximize the separation efficiency (i.e., peak capacity) under different constraints (analysis time or pressure limit). Using both experimental data and theoretical modeling, the current study reveals that the peak capacity increases with both gradient time and column length in a non-linear fashion. Marginal peak capacity is proposed to characterize the non-linear increase of peak capacity over the gradient time and column length. This study also attempts to understand the maximum peak capacity achievable under certain pressure limits using Neue’s peak capacity model. The results of this study provide a better understanding of the UPLC technology, and can also help to develop practical strategies to maximize the separation efficiency in gradient elution to meet the separation needs.     

分子相似性方法用于药物反相色谱定量结构色谱保留关系的研究

 应用分子相似性方法研究药物的反相色谱定量结构 色谱保留关系 (QSRR)。在全面考察药物的分子结构参数的基础上 ,采用分子相似性计算方法 ,将化合物结构信息变量转换为相似系数变量 ,并结合人工神经网络技术 ,对 16 2种药物进行反相色谱定量结构与色谱保留关系的研究。成功地应用分子相似性方法实现了对容量因子这一色谱保留参数的预测 ,建立了物理意义明确、预测能力较强的分子结构参数与反相色谱流动相溶剂强度和容量因子之间的定量关系模型 ,实验验证的结果也比较理想。     

Pilot-scale bioremediation of PAH-contaminated soils

Applied Biochemistry and Biotechnology - The Institute of Gas Technology (IGT) conducted a pilot-scale study at a former manufactured gas plant (MGP) site in New Jersey. The objective of the study...     

Formulation of Piperine–Chitosan-Coated Liposomes: Characterization and In Vitro Cytotoxic Evaluation

The present research work is designed to prepare and evaluate piperine liposomes and piperine–chitosan-coated liposomes for oral delivery. Piperine (PPN) is a water-insoluble bioactive compound used for different diseases. The prepared formulations were evaluated for physicochemical study, mucoadhesive study, permeation study and in vitro cytotoxic study using the MCF7 breast cancer cell line. Piperine-loaded liposomes (PLF) were prepared by the thin-film evaporation method. The selected liposomes were coated with chitosan (PLFC) by electrostatic deposition to enhance the mucoadhesive property and in vitro therapeutic efficacy. Based on the findings of the study, the prepared PPN liposomes (PLF3) and chitosan coated PPN liposomes (PLF3C1) showed a nanometric size range of 165.7 ± 7.4 to 243.4 ± 7.5, a narrow polydispersity index (>0.3) and zeta potential (−7.1 to 29.8 mV). The average encapsulation efficiency was found to be between 60 and 80% for all prepared formulations. The drug release and permeation study profile showed biphasic release behavior and enhanced PPN permeation. The in vitro antioxidant study results showed a comparable antioxidant activity with pure PPN. The anticancer study depicted that the cell viability assay of tested PLF3C2 has significantly (p < 0.001)) reduced the IC₅₀ when compared with pure PPN. The study revealed that oral chitosan-coated liposomes are a promising delivery system for the PPN and can increase the therapeutic efficacy against the breast cancer cell line.     

Effect of solvent composition on chiral recognition ability of molecularly imprinted DIDE derivatives.

In the present study, molecularly imprinted materials from the tetrapeptide derivative, H-Asp(OcHex)-Ile-Asp(OcHex)-Glu(OBzl)-CH2-, were adopted as samples to study the effect of the polarity of the environment on the chiral (molecular) recognition ability. The optimum composition, with the best chiral recognition, is a 50 vol% aqueous ethanol solution.     

The influence of correlation on the interpretation of Hund's multiplicity rule: A quantum Monte Carlo study

A systematic quantum Monte Carlo study of 2p atoms (C, N, O) and 3p atoms (Si, P, S) is performed to investigate the influence of correlation on the interpretation of Hund's multiplicity rule, which is an extension of our previous study of the carbon atom [J. Chem. Phys. 121, 7144 (2004)] to heavier atoms. The accuracy in the present study is significantly improved as compared with the previous study. A detailed analysis of the correlation contribution to individual energy components of the total energy is given beyond the self-consistent Hartree-Fock calculation. The stability of the highest spin-multiplicity state of all the atoms is ascribed to the greater electron-nucleus attraction energy that is gained at the cost of increasing the electron-electron repulsion energy as well as the kinetic energy. The present study demonstrates that correlation does not change the above conclusion due to the Hartree-Fock theory to support Boyd's less screening mechanism.     

基于液相色谱-质谱联用技术的妊娠期糖尿病患者脐带血代谢组学网络分析

妊娠期糖尿病（GDM）患病率呈现逐年上升的趋势，探究其对母婴之间代谢影响变得尤为重要。该研究基于液相色谱-质谱的代谢组学技术，分析GDM条件下脐带血血清代谢组的变化。采用正交偏最小二乘判别分析模型（OPLS-DA）与网络模型结合进行分析。结果表明代谢标志物花生四烯酸（AA）为关键代谢网络节点。通路分析显示，GDM会引起不饱和脂肪酸代谢异常，而该通路变化可能是GDM影响母婴代谢的重要分子机制。该文建立的代谢组学网络分析方法为研究GDM母婴间代谢变化提供了新的思路。     

中药质量研究的新进展

综述了国内中药质量研究的最新进展．内容包括:(1)微量元素与中药质量的关系研究;(2)有机成分与中药质量的关系研究．     

Preferred conformation of the glycosidic linkage of methyl-beta-mannose

The conformational preference of the glycosidic linkage of methyl-beta-mannose was studied in the gas phase and in aqueous solution by ab initio calculations, and by molecular dynamics (MD) and Car-Parrinello molecular dynamics (CPMD) simulations. MD simulations were performed with various water potential functions to study the impact of the chosen water potential on the predicted conformational preference of the glycosidic linkage of the carbohydrate in solution. This study shows that the trans (t) orientation of the glycosidic linkage of methyl-beta-mannose is preferred over its gauche clockwise (g+) orientation in solution. CPMD simulations clearly indicate that this preference is due to intermolecular hydrogen bonding with surrounding water molecules, whereas no such information could be demonstrated by MD simulations. This study demonstrates the importance of ab initio molecular dynamics simulations in studying the structural properties of carbohydrate-water interactions.     

有关普通高中学生化学问题解决归因的特点研究

本文在理论探讨归因对学生学习和未来发展的影响基础上,自编了以问题解决为重点的中学生化学学习归因量表,通过初步调查,得出如下结论:学生的整个化学学习归因无性别差异,都归为能力、努力、运气、教师、环境、基础等因素。在化学问题解决成功归因中,男生倾向于努力及经验(内在稳定因素),女生倾向于努力及教师的作用(外在不稳定因素);在化学问题解决失败归因中,男生倾向于努力归因(不稳定可控因素),而女生倾向于能力归因(稳定不可控因素)。     

Evaluation of Effectiveness of a Toothpaste Containing Tea Tree Oil and Ethanolic Extract of Propolis on the Improvement of Oral Health in Patients Using Removable Partial Dentures

The aim of this study was to evaluate the effect of toothpaste containing natural tea tree essential oil (TTO) and ethanolic extract of propolis (EEP), on microflora and selected indicators of oral health in patients using removable acrylic partial dentures. Fifty patients with varying conditions of hygiene were divided into two groups. The study group received the toothpaste with TTO and EEP, while the control group received the same toothpaste but without TTO and EEP. At the first visit, oral hygiene and hygiene of the prostheses were carried out. Control visits took place 7 and 28 days later and compared to baseline. Indexes like API (Approximal Plaque Index), mSBI (modified Sulcus Bleeding Index), OHI-s (simplified Oral Hygiene Index), and DPI (Denture Plaque Index) were assessed in three subsequent stages, and swabs were collected from floor of the mouth area to assess the microbiota. After 7 and 28 days of using the toothpaste with TTO and EEP, a statistically significant decrease of the examined indicator values were observed in the study group as compared to the values upon the initial visit. The number of isolated strains of microorganisms in the study group was decreased or maintained at the same level, whereas in the control group an increase in the number of isolated strains was observed. The observed stabilization of oral microbiota in patients from the study group confirms the beneficial activity of toothpaste containing EEP and TTO compared to the control group.     

Spectral and thermal studies of some 4-(O-acetyl)glycopyranosylaminopyrimidine derivatives

A spectral study (IR and UV spectroscopies) of seven 4-(O-acetyl)glycopyranosylaminopyrimidine derivatives has been carried out. The thermal study of the compounds allowed us to characterize the following processes: (i) desolvations, (ii) solid-solid transitions, (iii) melting, (iv) pyrolytic decompositions. Through the IR spectral study it was established that pyrolytic decompositions of all the compounds start with the acetyl groups. The reaction orders and activation energies of the deacetylation processes have been calculated.     

Polymorphic Characterization and Bioavailability of Nomegestrol Acetate

Polymorph screening is currently one of the most important strategies of innovators and generic companies from both pharmaceutical and intellectual property rights perspectives. Different polymorphs may have varying physicochemical properties which influence the bioavailability. The purpose of this study was to investigate the crystal structures and physicochemical properties of Nomegestrol acetate(NOMAC) polymorphs. Forms I and II(dioxane solvate) were isolated and prepared by systemic crystallization screening in this study, and the forms are reported for the first time. A structural analysis and comparison of all the forms are presented. This study was also the first time to apply a rapid and feasible ultra-highperformance-liquid chromatography(UHPLC)-electrospray ionization(ESI)-tandem mass spectrometry(MS) method to determine plasma levels of NOMAC within 3.0 mins. And this study demonstrated that the optimal crystal Form I displayed higher bioavailability than API indicating that Form I could be an alternative solid form that needs further research.