CoM-polynomial and topological coindices of hyaluronic acid conjugates

The molecular structure of corresponding drugs can be examined using a graph theory tool called topological index to learn about their physicochemical and biological properties. Topological index considers the pair of vertices that are connected while topological coindex takes into account the pairs of vertices that are not connected. Many of these topological indices can be readily calculated using various polynomial available in literature. We employ the concept of CoM-polynomial in this study and analyze the structure of hyaluronic acid conjugated with curcumin, paclitaxel, and methotrexate to acquire it. Many conventional topological coincides such as 1st Zagreb coindex, 2nd Zagreb coindex, 2nd modified Zagreb coindex, redefined 3rd Zagreb coindex, forgotten topological coindex, Randi? coindex etc. are also generated for these drugs.     

Improved QSAR Analysis of the Toxicity of Aliphatic Carboxylic Acids

The results of a QSPR study of the toxicity of carboxylic acids in aqueous solution are reported. The molecular set comprises 35 carboxylic acids with the corresponding pK _a values in water. The set of molecular and topological parameters includes electrotopological state of the carboxy and methyl groups, molar refractivity, refractive index, n-octanol-water partition coefficient logKo/w, surface tension, and polarizability. Quite reasonable estimates are obtained, which improve the results of previous theoretical calculations.     

Molecular modeling of wine polyphenols

Due to wide range of health effects of wine polyphenols, it is important to investigate the relationship between their structure and physical properties (quantitative structure–property relationship, QSPR). We have investigated linear, nonlinear (polynomial), and multiple linear relationships between given topological indices and molecular properties of main pharmacological active components of wine, such as molecular weight (MW), van der Waals volume (Vw), molar refractivity (MR), polar molecular surface area (PSA) and lipophilicity (log P). Partition coefficient (log P) was calculated using three different computer program (CLOGP, ALOGPS and MLOGP). The best models were achieved using the MLOGP program. Topological indices used for correlation analysis include: the Wiener index, W(G); connectivity indices, χ(G); the Balaban index, J(G); information-theoretic index, I(G); and the Schultz index, MTI(G). QSPR was performed on the set of 19 polyphenols and, particularly, on the group of phenolic acids, and on the group of flavonoids with resveratrol. The connectivity index has been successfully used for describing almost all parameters. Significant correlations were achieved between the Wiener index and van der Waals volume, as well as molecular weight.     

Polarizabilities and dipole moments of benzaldehyde, benzoic acid and oxalic acid in polar and nonpolar solvents

The purpose of this report is to calculate the orientation polarizability of benzaldehyde, benzoic acid and oxalic acid in polar and nonpolar solvents. The calculations are based on the knowledge of permanent dipole moment of the solutions. Other important physical quantities such as refractive index, density, specific volume, dielectric constant, molar polarization and molar refractivity are also calculated. Dipole moments of the solutions are calculated by using measured dielectric constants of the solutions. The dielectric constant measurements were made at 100 kHz. Relationships between the polarizability and concentration, specific volume, dielectric constant and dipole moment of the solutions are suggested.     

Refractivity and polarizability of mixtures of L-histidine–metformin hydrochloride–water at 30°C

The molar refractivity and polarizability of mixtures of L-histidine (0.01–0.11 mol L^–1)–metformin hydrochloride (0.03, 0.05, 0.07 mol L^–1)–water were calculated from density and refractive index data at 30°C. Enhancement in the polarizability has been observed with increase in L-histidine concentration as well as metformin hydrochloride content in the solution. The molar refractivity and polarizability of solutions increased appreciably after 0.09 mol L^–1 L-histidine in each aqueous solution.     

On topological indices of carbon nanocones and nanotori

Let G be a graph with n vertices and d _i is the degree of its ith vertex (d _i is the degree of v _i). In this article, we compute the redefined first Zagreb index, redefined second Zagreb index, redefined third Zagreb index, augmented Zagreb index of graphs carbon nanocones CNC _k[n], and nanotori [C₄C₆C₈(p,q)]. Also, compute the multiplicative redefined first Zagreb index, multiplicative redefined second Zagreb index, multiplicative redefined third Zagreb index, multiplicative augmented Zagreb index of carbon nanocones CNC _k[n], and nanotori [C₄C₆C₈(p,q)].     

GTI-space: the space of generalized topological indices

A new extension of the generalized topological indices (GTI) approach is carried out to represent “simple” and “composite” topological indices (TIs) in an unified way. This approach defines a GTI-space from which both simple and composite TIs represent particular subspaces. Accordingly, simple TIs such as Wiener, Balaban, Zagreb, Harary and Randić connectivity indices are expressed by means of the same GTI representation introduced for composite TIs such as hyper-Wiener, molecular topological index (MTI), Gutman index and reverse MTI. Using GTI-space approach we easily identify mathematical relations between some composite and simple indices, such as the relationship between hyper-Wiener and Wiener index and the relation between MTI and first Zagreb index. The relation of the GTI-space with the sub-structural cluster expansion of property/activity is also analysed and some routes for the applications of this approach to QSPR/QSAR are also given.     

Semi-empirical topological index: development of QSPR/QSRR and optimization for alkylbenzenes

The semi-empirical topological index, I(ET), was developed and optimized to describe the chromatographic retention of alkylbenzenes on the squalane stationary phase. The simple linear regression between the chromatographic retention and the proposed index, for 122 alkylbenzenes studied, is of good quality (determination coefficient, r(2)=0.9996, standard deviation, S.D.=5.5, and leave-one-out cross-validation correlation coefficient, r(CV)(2)=0.9996). The predictive ability of I(ET) was also verified for stationary phases with two different polarities (SE-30 and Carbowax 20 M), and good results were obtained, especially for the stationary phase with low polarity, showing that the specific molecular interactions occur on highly polar phases. The I(ET) was applied to construct quantitative structure-property relationship (QSPR) models for representative properties such as boiling point, Bp(degrees C), octanol/water partition coefficient, log P, van der Waals volume (V(W)) and molar refractivity (R(M)). Satisfactory quality QSPR models were obtained with Bp, V(W) and R(M) showing that the molecular size and dispersive forces are dominating factors with respect to the chromatographic retention.     

Structure and properties of organic molecules. 1. Three-dimensional topological indices of alkanes

The Winer and Schultz three-dimensional topological indices of alkanes are considered and compared with ordinary two-dimensional indices. Methods of index design and details of calculations are discussed. Unlike two-dimensional indices, three-dimensional ones adequately reflect differences between both structural and rotational isomers. Regression analysis of property-index correlations for formation enthalpy, molar volume, evaporation heat, and boiling temperature is performed using various two- and three-parameter (linear, quadratic, exponential, logarithmic, and power) functions. The ability of three-dimensional indices to correlate with these properties is found to be as good as that of two-dimensional ones. Tver State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 39, No. 3, pp. 484–492, May–June, 1998. This work was supported by RFFR grant No. 96-03-32384.     

Analytical expressions for topological properties of polycyclic benzenoid networks

Quantitative structure‐activity and structure‐property relationships of complex polycyclic benzenoid networks require expressions for the topological properties of these networks. Structure‐based topological indices of these networks enable prediction of chemical properties and the bioactivities of these compounds through quantitative structure‐activity and structure‐property relationships methods. We consider a number of infinite convex benzenoid networks that include polyacene, parallelogram, trapezium, triangular, bitrapezium, and circumcorone series benzenoid networks. For all such networks, we compute analytical expressions for both vertex‐degree and edge‐based topological indices such as edge‐Wiener, vertex‐edge Wiener, vertex‐Szeged, edge‐Szeged, edge‐vertex Szeged, total‐Szeged, Padmakar‐Ivan, Schultz, Gutman, Randić, generalized Randić, reciprocal Randić, reduced reciprocal Randić, first Zagreb, second Zagreb, reduced second Zagreb, hyper Zagreb, augmented Zagreb, atom‐bond connectivity, harmonic, sum‐connectivity, and geometric‐arithmetic indices. In addition we have obtained expressions for these topological indices for 3 types of parallelogram‐like polycyclic benzenoid networks.     

取代脂环烃物理化学性质的拓扑化学研究

为了探讨有机化合物的分子结构与理化性质的关系,作者在以前的工作基础上,基于一阶分子连通性拓扑指数构建了一个信息拓扑指数.将拓扑指数与取代脂环烃系列分子的气态标准生成热、气态标准熵、气态标准生成自由能、沸点、临界温度、临界压力、临界体积、汽化热、密度、热容及表面张力等十一种热力学性质及物理化学性质相关联,用一个通用公式对各类性质进行概括,然后用已有的实验数据与拓扑指数进行回归分析,得到一系列计算各性质的经验公式.回归结果发现,分子的理化性质与拓扑指数有较好的相关性,有5类性质的复相关系数大于0.99.用经验公式对各类性质进行重新计算,其结果与实验值比较符合,用实验值对计算值作图,发现各数据点紧靠对角线,说明误差较小.残差分布呈正态分布.     

On the Determination of Partial Molar Volumes,Partial Molar Refractions,Mean Electronic Polarizabilities and Effective Molecular Radii from Dilute Multi-component Data alone using Response Surface Models

A quaternary system consisting of three solutes, namely ethanol, diethylene glycol (DEG) and triethylene glycol (TEG) in benzene at 298.15 K and 1.0125 × 10⁵ Pa was studied. An experimental design in the range of concentration 0.006 < x _solute−i < 0.023 was explored, optimizing the metric distance among the solutes to avoid clustering. On-line simultaneous experimental measurements using a densitometer and a refractometer were utilized to measure bulk solution density and bulk refractive index, respectively. Response surface models describing the total molar volume and total molar refraction were employed to determine the partial molar volumes and the partial molar refractions of each solute from the dilute multi-component data alone. Neither densities nor refractive indices of any of the pure components were used and no binary information was required for the analysis. Definitions for the mean electronic polarizability and the effective molecular radius of a solute based on the partial molar refraction were introduced. Subsequently, the mean electronic polarizabilities and the effective molecular radii for each solute in multi-component solutions, as well as the solvent were determined. The results obtained for the partial molar volumes, partial molar refractions, electronic polarizabilities and the effective molecular radii were in good agreement with those obtained from independent binary experiments as well as those from literature binary data.     

神经网络用于色谱研究(Ⅰ)─GC保留值估算

神经网络用于色谱研究（Ⅰ）──ＧＣ保留值估算李志良,八重治,梁本熹,石乐明（湖南大学化学化工系,长沙,４１００８２;日本国立丰桥技术科学大学,中国科学院化工冶金研究所）关键词神经网络,修饰反向传播算法,气相色谱保留值神经网络（ＮＮ）近年来获得突破性进...     

An improved estimation of water-organic liquid interfacial tension based on linear solvation energy relationship approach

An equation based on the linear solvation energy relationship (LSER) was proposed to predict the interfacial tension between organic liquid and water. The equation takes into account five parameters characterizing properties of the organic liquid molecule: excess molar refraction, solute dipolarity/polarizability, effective hydrogen bond acidity, effective hydrogen bond basicity, and the McGowan molar intrinsic volume. The proposed equation provides a better approximation of the interfacial tension than a similar one derived earlier by Freitas et al. (J. Phys. Chem. B 101 (1997, 7488-7493), which is based on seven terms.