bluuebunny/crossref_metadata_2025_split huggingface dataset:
Application of the ORMUCS Method to Structure‐Activity Studies on the Fungicidal Activity of Mepronil Derivatives
Authors: Takahashi Yoshimasa , Sasaki Shin‐Ichi , Tamaru Masatoshi , Shimazaki Isao , Ito Shigetoshi , Kawada Seigo , Suda Yoshitaka 
Published: October 2006

AbstractApplication of the ORMUCS method, proposed by the authors in the previous work, to structure‐activity studies is discussed in comparison with the Hansch approach. Using this method, the correlation between chemical structures of a series of mepronil derivatives and their fungicidal activity were examined with rating score data obtained by green house tests (in vivo test). The activity was highly correlated with the largest width and hydrogen accepting property of a substituent on the benzoyl moiety. This is consistent with the best QSAR equation obtained from Hansch analysis using in vitro data for mycelial growth inhibition on the same series.
A Quantum Chemical Study of Insect Juvenile Hormone Mimics: The Active Conformation and the Electrostatic Similarities
Authors: Nakayama Akira , Richards W. Graham 
Published: October 2006

AbstractThe stable conformations and the electrostatic properties of insect juvenile hormone (JH) mimics are studied using semi‐empirical molecular orbital methods. One of the minimum energy conformations of JH active diphenylethers, a new class of JH mimics, is found to be superimposable on the stable extended structure of methoprene which is one of the most highly active JH mimics within the series of terpenoid compounds. As well as the superimposability of the diphenylether and terpenoid structures, JH active functional groups such as esters, carbamates and oxime O‐ethers are also shown to be superimposable. The electrostatic potentials of these functional groups which are commonly found in the diphenylethers and the terpenoid JH mimics are similar to each other in terms of potential contours and the similarity indices of electrostatic potentials. This may account for the bioisosterism of these active functional groups. Here we postulate a model of molecular recognition at the JH receptor in which the electrostatic interaction is important as well as the size and shape of the molecule. The molecular similarities between different classes of JH mimics in terms of steric and electrostatic properties, which are derived from quantum chemical methods, may help to understand the universality of active structures and aid in the design of new active generations.
Multiple Regression Analysis of Antimalarial Activities of Sulfones and Sulfonamides in Cell‐Free Systems and Principal Component Analysis to Compare with Antibacterial Activities
Authors: Wiese M. , Seydel J. K. , Pieper H. , Krüger G. , Noll K. R. , Keck J. 
Published: October 2006

AbstractThe inhibition of dihydropteroate synthase extracts by sulfones and sulfonamides has been determined. Structural dependency of the observed I50‐values has been quantitatively explained by multiple regression and principal component analysis. New highly active sulfones have been synthesized guided by the derived QSAR. The analysis leads to the conclusion that electronic and steric substituent effects are decisive and that sulfones and sulfonamides are binding to the same receptor site. The LFE‐descriptors used are correlated with the minimal conformational entropy. The results are also compared with the results obtained in cell‐free and whole cell systems of bacteria. The additional influence of cell‐wall permeability on inhibitory efficacy is demonstrated.
Description of Heterocyclic Substituents: A Free‐Wilson Type Approach Using D‐Optimal Designs
Authors: Cativiela Carlos , García José I. , Elguero José , Mathieu Didier , Luu Roger Phan Tan 
Published: October 2006

AbstractIn order to test the hypothesis that structural characteristics in a Free‐Wilson type model can be used to describe heterocyclic substituents, a set of heterocyclic compounds (eighteen carboxaldehydes and their corresponding carboxylic acids) containing only one heteroatom was prepared and some spectroscopical properties were used as experimental responses. Fedorov's algorithm has been used to choose D‐optimal designs. The validity of this methodology is discussed.
Quantum Chemical Studies of H2‐Antagonist‐Receptor Complexes. Cimetidine and Related Compounds
Authors: den Kelder Gabriëlle M. Donneé‐Op , Haaksma Eric E. J. , Timmerman Hendrik 
Published: October 2006

AbstractMolecular and conformational properties of H2‐receptor antagonists were studied by means of the semiempirical MNDO (Modified Neglect of Differential Overlap) approximation. The compounds investigated were cimetidine (N″‐cyano‐N‐methyl‐N′‐[2‐[(5‐methylimidazol‐4‐yl methyl)thio]ethyl]guanidine) analogues, in which the cyanoguanidine moiety was replaced by various other neutral dipolar groups. A strong relation was found between, H2‐antagonistic activity as measured in vitro on the histamine stimulated guinea pig right atrium, one of the components of the overall MNDO dipole moment, and the lipophilic character of the different substituent groups. The dipole moment component points along the direction of the amidine N′H‐bond suggesting the relevance of hydrogen bond formation upon binding of the ligand to the H2‐receptor molecule. This theoretical study demonstrates that the semiempirical quantum chemical MNDO method might be helpful in calculating molecular properties as e.g. dipole moments, both in cases were experimental data are lacking, and in cases where experimental data are obtained under conditions which deviate strongly from the situation in which the ligand most probably is present when bound to the receptor macromolecule. An incorrect use of quantum chemical properties is discussed.
Electronic and Hydrophobic Constants of Azoxy Groups Containing Electron Withdrawing Functions
Authors: Calvino Rosella , Fruttero Roberta , Garrone Adele , Gasco Alberto 
Published: October 2006

Abstractσ and π constants for azoxy groups containing electron withdrawing functions have been evaluated. The electrical influence of these groups was separated into an induction and a resonance parameter. A new scale of π substituent constants has been derived analysing log P values of phenyldiazenecarbonitrile 2‐oxide derivatives. It is closely parallel with the π scale obtained from the nitrophenyl substituted system.
QSAR Studies on Mifentidine and Related Compounds
Authors: den Kelder G. M. Donné‐Op , Haaksma E. E. J. , van der Schaar M. W. G. , Veenstra D. M. J. , Timmerman H. , Cereda E. , Dubini E. 
Published: October 2006

AbstractThe MNDO semiempirical SCF‐MO method has been used to calculate charge distributions of a series of histamine H2‐receptor antagonists. The investigated compounds concern mifentidine (N‐isopropyl‐N′‐(4‐1H‐imidazol‐4‐yl‐phenyl)formamidine) analogues, in which the imidazole moiety has been substituted or replaced by various aromatic heterocyclic groups. A correlation has been found between H2‐antagonistic activity as determined by inhibition of specific [3H]‐tiotidine binding to the H2 receptors of a guinea pig cortex preparation, and the net atomic charges of two of the atoms (X‐H bond in which X is a nitrogen or carbon atom) in the heterocycle. The binding capacity of the ligand molecule to the receptor is enhanced when the electronic population of atom X and the positive charge on the proton are higher. Assuming that the difference between both charges might effectively serve as a valuable substitute for the hydrogen bond forming capacity of the X‐H group, the conclusion can be drawn that this property of the heterocycle plays an important role in the interaction process of the ligand with its H2‐receptor. The obtained regression equation(s) suggest that the monocation (formamidine moiety protonated) is the species related to pharmacological activity.
Solubility Properties in Biological Media. 12. Regarding the Mechanism of Nonspecific Toxicity or Narcosis by Organic Nonelectrolytes
Authors: Kamlet Mortimer J. , Doherty Ruth M. , Abraham Michael H. , Taft Robert W. 
Published: October 2006

AbstractNarcotic effects of organic nonelectrolytes to the tadpole (logC), minimum blocking concentrations for stoppage of electrical activity in the muscle of the frog, Rana pipiens (logMBC), and binding of nonelectrolytes to bovine serum albumin (log1/C) are well correlated by the following equations, magnified image where VI is the intrinsic (van der Waals) molar volume, and π*, βm and αm are the solvatochromic parameters that scale solute dipolarity/polarizability, hydrogen bond acceptor basicity, and hydrogen bond donor acidity.That increasing solute π* leads to lesser partition into the biosystem compared with its aqueous environment, but also leads to greater toxicity or anesthetic effect is suggested to implicate in the mechanism of toxicity or narcosis a specific association effect between the more dipolar solutes (toxicants) and a molecule involved in the transmission of nervous impulses.
An Index of Molecular Flexibility from Kappa Shape Attributes
Authors: Kier Lemont B. 
Published: October 2006

AbstractAn index encoding the structural attribute known as flexibility has been devised based upon the chemical graph. The flexibility definition is based upon the role of molecular size, branching, cycles and heteroatom content. The calculation of the index, phi, uses information from the kappa indexes to encode these contributions. The flexibility index is made equal to the product of kappa‐one and kappa‐two, normalized to the number of atoms in the graph. Examples reveal the structure‐activity potential for the index.
pKa, Log P and MedChem CLOGP Fragment Values of Acidic Heterocyclic Potential Bioisosteres
Authors: Lipinski Christopher A. , Fiese Eugene F. , Korst Robert J. 
Published: October 2006

AbstractLog P values have been measured for twenty phenyl and benzyl five membered heterocycles and alicyclic analogs that might function as acidic bioisosteres. pKa's have been measured by potentiometric titration in water and 1:1 dioxane‐water. From this experimental data, twelve missing fragmental CLOGP values are derived for use in calculating Log P values according to the Pomona College MedChem program. Log P values of some of the simple benzyl and phenyl heterocycles are compared to those measured for four clinically used drugs containing the same acidic moieties. Sulfonyl urea and acyl sulfonamide moieties have similar pKa and Log P values suggesting that these groups might be explored as bioisosteres.
Comprehensive Analysis of Quantitative Structure‐Activity Relationships of Catecholamine‐Uptake Inhibitors
Authors: Terada Yukimasa , Tomita Tatsuya , Inami Yoshiharu 
Published: October 2006

AbstractQuantitative Structure‐Activity Relationships (QSAR) of inhibitors of dopamine (DA)‐ and norepinephrine (NE)‐uptake have been analyzed quantitatively. Previously, we reported that several series of congeners are susceptible to similar substituent effects, and these structurally diverse compounds interact with common receptor points by the hydrophobic interaction of a phenyl group and the hydrogen bonding of a nitrogen atom. In this report, we extended this concept to derive an equation that quantitatively interprets the activity of 113 compounds comprising 6 skeletal groups.Excellent QSAR equations were obtained in which all parameters used were physicochemically significant. Of the parameters adopted therein, the root mean square (rms) of the distances between corresponding pharmacophore was an especially valuable parameter to compare the activity of the structurally diverse compounds. On the other hand, a substituent existing in a specific region of the inhibitor molecule causes steric hindrance with the receptor and interferes with an effective binding of the inhibitor. Lastly, it was concluded that a degree of correspondence of proper pharmacophore to the receptor points, as well as the volume of that specific region, principally determines the binding ability of that congener, and the substituent effect of each compound is added to that fundamental affinity.
Studies of Performance of Graph Theoretical Indices in QSAR Analysis
Authors: Ośamiałowski Krzysztof , Kaliszan Roman 
Published: October 2006

AbstractComparative studies of performance in exemplary QSAR of the most commonly used structural descriptors derived from molecular graphs were performed. Three diverse series of test compounds were selected for which various property measures existed. One group of compounds were polychlorinated dibenzofurans of determined gas chromatographic retention indices. The second group comprised isomers of general formula C4H8O of known boiling points, refractivity indices and densities. Third set of agents consisted of 2‐substituted isonicotinic acid hydrazides of determined antibacterial activity. The following graph theoretical indices were considered: the Kier and Hall [22] generalized molecular connectivity indices, the Balaban distance sum connectivity index calculated after Barysz et al. [23], the indices of molecular shape of Kier [24], the information indices of neighbourhood symmetry of Sarkar et al. [25] and of Basak et al. [26]. Auxiliary structural parameters, e.g., molecular surface area, were also employed. Significant correlation with molecular mass and intercorrelations among the graph theoretical indices were observed excepting the group of information content indices. For the compounds and properties studied the graph theoretical indices considered appeared unable to provide a size‐independent, meaningful input to property description.
H‐Bond Contribution to Octanol‐Water Partition Coefficients of Polar Compounds
Authors: Raevsky Oleg A. , Schaper Klaus‐J. , Seydel Joachim K. 
Published: October 2006

AbstractA quantitative description of the hydrogen bond contribution to logP is presented for carbonyl and hydroxyl compounds. A two parameter Eq. correlating the hydrophobicity with molecular volume and sum of free energy H‐bond acceptor ability is derived for carbonyl compounds. If compounds with hydroxyl groups are included also H‐bond donor abilities have to be considered. It can be concluded that hydrogen bonds play a very important role for the formation/presentation of hydrophobic properties of polar compounds. A quantitative description of the hydrogen bond contribution to logP values of such compounds is possible by means of free energy H‐bond acceptor and donor factor values only. Negative logP values result from the negative contribution of H‐bond acceptor ability.
SD‐modelling and Prediction by WHIM Descriptors. Part 5. Theory Development and Chemical Meaning of WHIM Descriptors
Authors: Todeschini Roberto , Gramatica Paola 
Published: October 2006

AbstractWHIM descriptors are 3‐dimensional molecular indices that represent different sources of chemical information. WHIM descriptors contain information about the whole 3D‐molecular structure in terms of size, shape, symmetry and atom distribution. These indices are calculated from (x, y, z)‐coordinates of a molecule within different weighting schemes in a straightforward manner and represent a very general approach to describe molecules in a unitary conceptual framework. A set of 40 simple heterogeneous compounds is used to show the main characteristics, some properties and the modelling power of WHIM descriptors by using simple scatter plots of the descriptors, Principal Component Analysis and predictions of simple physicochemical properties.
A general approach for the quantitative analysis of bisphosphonates in human serum and urine by high‐performance liquid chromatography/tandem mass spectrometry
Authors: Zhu Lee S. , Lapko Veniamin N. , Lee Jean W. , Basir Yousef J. , Kafonek Chris , Olsen Richard , Briscoe Chad 
Published: October 2006

AbstractBisphosphonates are extremely hydrophilic and structurally similar to many endogenous phosphorylated compounds, making their selective extraction from serum or urine very challenging. Many bisphosphonates lack strong chromophores for sensitive UV or fluorescence detection. We report here the first general approach to enable sensitive and selective quantitation of N‐containing bisphosphonates by liquid chromatography/tandem mass spectrometry (LC/MS/MS) following derivatization with diazomethane. The novelty of the strategy lies in performing the derivatization on silica‐based anion‐exchange sorbents as an integrated step in the sample purification by solid‐phase extraction (SPE). The ‘on‐cartridge’ reaction with diazomethane not only led to higher efficiency of derivatization, but also enabled a more discriminatory recovery of the drug's derivatives. The derivatized bisphosphonates demonstrated improved chromatographic separation and increased sensitivity of the detection. The general applicability of the approach was demonstrated by validation of bioanalytical methods for risedronate and alendronate in human serum and urine. Sensitivity was achieved at the pg/mL level with merely 100–200 µL of sample. Copyright © 2006 John Wiley & Sons, Ltd.
Design and experimental evaluation of a QFT contact task controller for electro‐hydraulic actuators
Authors: Niksefat N. , Sepehri N. , Wu Q. 
Published: October 2006

AbstractThis paper presents design and experimental evaluation of a robust contact task controller for an electro‐hydraulic actuator that operates under significant system uncertainties and nonlinearities. The designed controller allows the actuator to follow a free space trajectory, and upon contact with an uncertain environment exert a desired force, by stably passing through the transition phase from free space to constrained space. The scheme is essentially the combination of two distinct control laws that are individually designed for position regulation in free space and force regulation during sustained contact. Both controllers are designed, using a nonlinear approach within the framework of quantitative feedback theory (QFT), to satisfya priorispecified stability, tracking and disturbance rejection specifications. They are then combined with a simple switching law to form a contact task controller. Due to the existence of a switching, the resulting control system is non‐smooth. The stability of the controller is then analysed using an extended version of Lyapunov's second method under the condition of existence and uniqueness of Filippov's solution. Experiments, performed on a typical industrial hydraulic actuator, include motion through free space, contact with the environment and the transition between the two. The proposed QFT contact task control scheme enjoys the simplicity of fixed‐gain controllers, is easy to implement, requires very little computational effort, is robust to the variation of hydraulic functions as well as environmental stiffness, and results in responses with good performance in both transient and steady‐state periods. Additionally, the controller only requires measured contact force and actuator position as feedback; this makes the controller attractive for industrial implementation. Copyright © 2006 John Wiley & Sons, Ltd.
Output feedback stabilization of nonlinear networked control systems with non‐decreasing nonlinearities: a matrix inequalities approach
Authors: Cheng Teddy M. , Savkin Andrey V. 
Published: October 2006

AbstractThis paper addresses an output feedback stabilization problem of a class of nonlinear systems with nonlinearities satisfying the non‐decreasing propertyvialimited‐capacity communication channels. Using ideas from absolute stability theory, we propose an algorithm that consists of an observer and a coder/decoder‐controller pair. Sufficient conditions for the stabilization problem are provided and presented in terms of linear matrix inequalities. Copyright © 2006 John Wiley & Sons, Ltd.
The visual compass: Performance and limitations of an appearance‐based method
Authors: Labrosse Frédéric 
Published: October 2006

AbstractIn this article we present an algorithm to estimate the orientation of a robot relative to an orientation specified at the beginning of the process. This is done by computing the rotation of the robot between successive panoramic images, grabbed on the robot while it moves, using a subsymbolic method to match the images. The context of the work is simultaneous localization and mapping (SLAM) in unstructured and unmodified environments. As such, very few assumptions are made about the environment and the robot's displacement. The algorithm's performance depends on the value of a number of parameters being determined to provide overall good performance of the system. The performance is evaluated in different situations (trajectories and environments) with the same parameters and the results show that the method performs adequately for its intended use. In particular, the error is shown to be drifting slowly, in fact much slower than unprocessed inertial sensors, thus only requiring infrequent realignment, for example, when relocalizing in a topological map. Limitations of the proposed methods are also shown and discussed. © 2006 Wiley Periodicals, Inc.
Cochlear implantation in the irradiated temporal bone
Authors: Adunka O F , Buchman C A 
Published: October 2006

Objective: To demonstrate the feasibility and complexities of cochlear implantation in the setting of bilateral temporal bone osteoradionecrosis.Study design: Case report.Setting: Tertiary care referral centre.Case description: A 66-year-old woman with bilateral temporal bone osteoradionecrosis and profound hearing loss, following treatment for tonsillar cancer, underwent cochlear implantation. Prior canal wall down mastoidectomy and subsequent temporal bone resection with free flap reconstruction had been performed on the implanted ear. The contralateral ear received a canal wall down mastoidectomy. A completely dehiscent mastoid segment of the facial nerve and extensive fibrosis were evident in the implanted ear. Only minimal fibrous reaction was found within the cochlea, allowing for full electrode insertion. At three months, speech recognition testing documented a consonant-nucleus-consonant (CNC) word score of 54 per cent.Conclusions: This report demonstrates the feasibility of cochlear implantation after temporal bone surgery and free flap reconstruction in the setting of diffuse osteoradionecrosis. The patient's excellent open-set speech understanding using the cochlear implant implies that radiation did not severely damage the central auditory pathways. Thus, some patients with radiation-induced hearing loss may be appropriate cochlear implant candidates. Special attention should be paid to surgical planning, as complications related to wound healing, electrode insertion and facial nerve injury may be more likely.
Scientists unearth clues to soil contamination by comparing old and new soil samples
Authors: Lapenis Andrei G. , Torn Margaret S. , Harden Jennifer W. , Hollocker Kurt , Babikov Boris V. , Timofeev Anayoly I. , Hornberger Michelle I. , Natiis Randy 
Published: October 2006

Oil contamination during the era of industrialization is a complex but important topic for those involved in land use planning and health assessment [Feshbach, 1995]. One of the most direct ways to estimate the anthropogenic contamination of soil is to compare soil samples collected before the intensive industrialization period with modern samples taken from the same locations.Quantitative information about postindustrial trends in soil chemistry is usually derived from old measurements of the soil's chemical composition.The use of such old data, however, poses important limitations. First, in most cases, the sampling site locations were identified with the name of the closest administrative district [Lindert et al., 1996] or nearest village or town [Sherbakov and Vaseneva, 1996], rather than the specific location of the sampling site. Because of significant natural variability in soil properties, a difference of only a kilometer yields pronounced differences in soil composition and structure. Other challenges arise from using different soil analysis methods. For instance, the 100‐year‐old measurement of soil humus by the so‐called “dry combustion” method can underestimate humus and organic carbon content by ∼40% [Sherbakov and Vaseneva, 1996].