枸橼酸铋雷尼替丁胶囊有效成份的紫外分光光度法的测定

提出了对枸橼酸铋雷尼替丁胶囊有效成份进行紫外分光光度测定的新方法，该方法简便、快速、准确度高，能用于纯度较高的样品分析，可作为枸橼酸铋雷尼替丁胶囊药品质量标准控制方法。     

Determination of flurbiprofen in pharmaceutical formulations by UV spectrophotometry and liquid chromatography

In this study, a new and rapid UV spectrophotometric (UV) method and a reversed phase high performance liquid chromatographic (LC) method were developed for quantitative estimation of flurbiprofen, a non-selective, non-steroidal, anti-inflammatory drug (NSAID), in pure form and in pharmaceutical dosage form. The solvent system, wavelength of detection, chromatographic conditions were optimized in order to maximize the sensitivity of both the proposed methods. The linear regression equations obtained by least square regression method were Abs=7.5906×10⁻² concentration (μg/ml) + (−) 4.6210×10⁻² for the UV method, and peak area=1.2652×10² concentration (ng/ml) + 1.4830×10³ for the LC method. The detection limit as per the error propagation theory was found to be 0.34 μg/ml for UV method and 15 ng/ml for LC method. The developed methods were successfully employed with high degree of precision and accuracy for the estimation of total drug content in two commercial ophthalmic drops of flurbiprofen. The results of analysis were treated statistically, as per USP 2000 and International Conference on Harmonization (ICH) guidelines for validation of analytical procedures, and by recovery studies. The results obtained from UV method were comparable with those obtained by using LC. It was concluded that both the developed methods are equally accurate, sensitive, precise, reproducible, robust and rugged and could be applied directly and easily to the pharmaceutical preparations of flurbiprofen. However, LC method is useful at very low level (ng/ml), whereas UV method is suitable at μg/ml level.     

胶束增敏紫外分光光度法测定甲砜霉素的研究

用紫外分光光度法对pH 6.00Na2 HPO4-NaH2 PO4的缓冲介质中甲砜霉素和溴化十六烷基三甲铵( CTMAB)形成的胶束配合物的性能进行了研究.利用胶束的增敏增稳作用,提出了测定甲砜霉素的紫外分光光度新方法,方法线性范围为0.25～95 μg/mL,检出限为0.12 μg/mL.已应用于片剂中甲砜霉素的测定...     

紫外分光光度法测定川芎中内酯的总量

建立中药川芎中总内酯的测定方法. 采用紫外分光光度法, 以瑟丹酸内酯为对照品, 在一定条件下吸光度和瑟丹酸内酯的浓度呈良好的线性关系. 该方法可作为川芎中总内酯的半定量质量控制方法.     

Rapid estimation of global sugars by UV photodegradation and UV spectrophotometry

The UV/UV method developed for the measurement of specific wastewater pollution parameters (ammonium, Kjeldahl nitrogen, total phosphorus) is adapted to the determination of sugars in fruit juices and soft drinks. The procedure is based on the UV spectrophotometric detection of by-products of UV photodegradation of carbohydrates. Time of analysis is greatly reduced by using specific pH conditions and diluted samples.     

Structure elucidation and 3D solution conformation of the antibiotic enduracidin determined by NMR spectroscopy and molecular dynamics

Enduracidin and ramoplanin belong to the large family of cyclodepsipeptide antibiotics, highly effective against Gram-positive bacteria. The primary and 3D solution structure of ramoplanin is already well known, and the primary structure of enduracidin has been determined by a combination of chemical and NMR spectroscopic methods. Both antibiotics share a similar peptide core of 17 amino acids and differ mainly in the length of the acyl chain and the presence of two D-mannose moieties in ramoplanin. Based on the high sequence homology with ramoplanin, the structure in solution of enduracidin is modeled as a cyclic peptide. The tertiary structure thus obtained was refined through molecular dynamics (MD) simulation, in which the interatomic NOE-derived distance restraints were imposed. MD simulations yielded a family of representative 3D structures (RMSD = 0.89), which highlighted a backbone geometry similar to that of ramoplanin in its beta-hairpin arrangement. In contrast, enduracidin displays a different arrangement of the side-chain and of the residues forming the hydrophobic core.     

A step forward in disclosing the secret of stradivari's varnish by NMR spectroscopy

It is commonly thought that the varnishes used by the great violin‐maker Antonio Stradivari may have a role in determining not only the esthetical features but also the acoustic properties of his instruments, and the idea of a “lost secret” is still widespread among musicians and violin‐makers. Previous scientific researches on varnish samples of Stradivari's instruments revealed that they were generally made by a mix of linseed oil with and colophony or metal rosinates in different ratios ranging between 75/25 (oil/resin) and 60/40 (oil/rosinate). However, it is still not clear whether the mixture composition can be related to any structural and/or functional feature of the resulting varnish. To investigate this aspect, we prepared varnishes with different linseed oil/colophony (w/w) ratios and applied NMR techniques to achieve information about their chemical–physical characteristics. Here, we show that the two components strongly interact in the solid state and that only the varnish prepared from 75/25 (w/w) linseed oil/colophony mixture displays unique properties in terms of dynamic homogeneity unlike coatings with other compositions. Our results suggest that the so‐called “secret” of Stradivari's finish could not be related to unknown ingredient(s) but to a specific oil/resin composition that provides the best performance. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3949–3954     

Dynamic NMR spectroscopy in studies of the kinetics of photoinduced chemical exchange in solutions

Modern NMR-based methods of studying the kinetics and mechanisms of reversible photochemical reactions in solutions are surveyed. Detailed consideration of peculiar features of the experimental techniques based on NMR lineshape analysis and double resonance NMR and used for the determination of the effective rate constants for and quantum yields of photoinduced chemical exchange processes is presented. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1631–1641, October, 2006.     

Molecular dynamics of hydrophilic poly(propylene imine) dendrimers in aqueous solutions by 1H NMR relaxation

The local dynamics of three poly(propylene imine) dendrimers with hydrophilic triethylenoxy methyl ether terminal groups were studied in D₂O by the measurement of the ¹H NMR relaxation times, which were treated with the Lipari–Szabo model‐free approach. The results showed that the overall mobility increased with temperature and decreased with increasing dendrimer size. An Arrhenius trend was observed for both overall and local motions. The activation energy of overall tumbling increased from 11.3 to 17.5 kJ/mol with the dendrimer size. The local mobility decreased from the outer part to the inner part of the dendrimer and with the dendrimer size. The spatial restriction of local motions decreased with increasing temperature up to 55 °C and remained constant above 55 °C. Local motions were more restricted when the dendrimer size increased. The results showed that the hydrophilic end groups of the dendrimers were located preferentially at the periphery of the molecules and were extended in the aqueous environment. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2969–2975, 2003     

The Dynamics of the Neuropeptide Y Receptor Type 1 Investigated by Solid-State NMR and Molecular Dynamics Simulation

We report data on the structural dynamics of the neuropeptide Y (NPY) G-protein-coupled receptor (GPCR) type 1 (Y1R), a typical representative of class A peptide ligand GPCRs, using a combination of solid-state NMR and molecular dynamics (MD) simulation. First, the equilibrium dynamics of Y1R were studied using ¹⁵N-NMR and quantitative determination of ¹H-¹³C order parameters through the measurement of dipolar couplings in separated-local-field NMR experiments. Order parameters reporting the amplitudes of the molecular motions of the C-H bond vectors of Y1R in DMPC membranes are 0.57 for the Cα sites and lower in the side chains (0.37 for the CH₂ and 0.18 for the CH₃ groups). Different NMR excitation schemes identify relatively rigid and also dynamic segments of the molecule. In monounsaturated membranes composed of longer lipid chains, Y1R is more rigid, attributed to a higher hydrophobic thickness of the lipid membrane. The presence of an antagonist or NPY has little influence on the amplitude of motions, whereas the addition of agonist and arrestin led to a pronounced rigidization. To investigate Y1R dynamics with site resolution, we conducted extensive all-atom MD simulations of the apo and antagonist-bound state. In each state, three replicas with a length of 20 μs (with one exception, where the trajectory length was 10 μs) were conducted. In these simulations, order parameters of each residue were determined and showed high values in the transmembrane helices, whereas the loops and termini exhibit much lower order. The extracellular helix segments undergo larger amplitude motions than their intracellular counterparts, whereas the opposite is observed for the loops, Helix 8, and termini. Only minor differences in order were observed between the apo and antagonist-bound state, whereas the time scale of the motions is shorter for the apo state. Although these relatively fast motions occurring with correlation times of ns up to a few µs have no direct relevance for receptor activation, it is believed that they represent the prerequisite for larger conformational transitions in proteins.     

用新紫外光度法测定水中亚硝酸盐氮的研究

碱性品红与亚硝酸根在硫酸介质中反应 ,反应产物在近紫外区有一吸收峰 ,其λmax在 2 6 5nm .其NO-2 -N含量在 0～ 0 .6mg/L范围内符合比尔定律 ,ε=1.2 0 5× 10 4L·mol- 1·cm- 1,据此建立了一个简单、快速、选择性好的测定亚硝酸盐氮的新方法 .用于地表水、地下水的测定 ,结果与盐酸萘乙二胺比色法一致 .     

Autooxidation Mechanism of Pyrogallol and Its Free Radical Effects Studied by Means of ESR, UV and NMR*

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Warifteine and methylwarifteine: 1H and 13C assignments by two‐dimensional NMR spectroscopy

The identity and structures of warifteine and methylwarifteine, two tertiary bisbenzylisoquinoline alkaloids of an unusual type, were elucidated and verified by 2D NMR spectroscopy. Complete ¹H and ¹³C NMR spectral assignments were obtained. Copyright © 2003 John Wiley & Sons, Ltd.     

The tautomerism of Omeprazole in solution: a 1H and 13C NMR study

The tautomerism of 5(6)-methoxy-2-([(4-methoxy-3,5-dimethyl-2-pyridinyl)methyl] sulfinyl)-1H-benzimidazole (omeprazole) was determined in solution, K(T) = 0.59 in THF at 195 K, in favor of the 6-methoxy tautomer. The assignment of the signals was made by comparison with its two N-methyl derivatives in acetone-d6 and through theoretical calculations of the absolute shieldings (GIAO/DFT/6-311++G**).     

13C and1H NMR study of molecular motion in the deoxycholic acid-ferrocene solid inclusion compound

Using solid-state ¹³ C NMR spectroscopy and also measurements of proton spin-lattice relaxation times T ₁ and second moments M ₂ , we have investigated molecular motion in solid inclusion compounds of deoxycholic acid with ferrocene in the interval 100–400 K. We have identified various dynamic processes occurring with participation of molecules of the matrix and the included molecules. We have shown that in addition to rapid reorientations of the cyclopentadienyl rings, the ferrocene molecules undergo 180° jumps about the C ₂ axis. We have determined the parameters for all the molecular motions. We discuss the conformational state of the included molecules.A. N. Nesmeyanov Institute of Heteroorganic Compounds, Russian Academy of Sciences, Moscow 117813. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 586–593, March, 1992.     

紫外分光光度法测定富马酸二甲酯的含量

本文研究了用紫外分光光度法测定富马酸二甲酯含量的方法 ,探讨了测定过程中有关条件的变化对测定的影响 ,获得了测定的适宜条件 :波长 2 1 0± 2nm ;温度 1 9～ 2 5℃ ;无水乙醇为溶剂 ;测定体系的pH为7.2 5～ 8.2 5。DMF的含量与溶液的吸光度的关系为P =0 .0 933A +0 .0 4 1 6,经与色 -质谱分析结果对比表明本法具有较高的准确性