Search PubMed⌕ Search

Biomedical subjects

L B Kier

Publications and source records attributed to L B Kier.

At least 37 records · Page 2Linked to original sources
PubMed1988

Amino acid side chain parameters for correlation studies in biology and pharmacology.

Fifteen physicochemical descriptors of side chains of the 20 natural and of 26 non-coded amino acids are compiled and simple methods for their evaluation described. The relevance of these parameters to account for hydrophobic, steric, and electric properties of the side chains is assessed and their intercorrelation analyzed. It is shown that three principal components, one steric, one bulk, and one electric (electronic), account for 66% of the total variance in the available set. These parameters may prove to be useful for correlation studies in series of bioactive peptide analogues.

Amino Acid Sequence↗
PubMed1983

General definition of valence delta-values for molecular connectivity.

The molecular connectivity valence delta-values have been defined in terms of the count of nonhydrogen valence electrons on a valence-state atom as screened from the nucleus by the core electrons. The core is defined as the nonvalence electrons minus 1. This general definition expresses the valence delta-values for second and third quantum level atoms and halogens. Valence delta-values have been derived for higher oxidation states of sulfur and phosphorus. The internal consistency of these delta-values is tested by their ability to closely correlate molar refraction values with 1 chi v. It is found that a second variable, the count of the number of alpha hydrogen atoms, greatly increases the quality of the correlation. Some biological SAR applications reveal the general utility of these findings.

Chemical Phenomena↗
PubMed1981

Derivation and significance of valence molecular connectivity.

The physical basis for valence molecular connectivity was studied. The delta v and delta values are cardinal numbers describing the electronic structure of atoms in their valence states. The value delta v + delta describes the volume of a bonding atom while the value delta v - delta describes the electronegativity. By using the principle of electronegativity equalization, bond electronegativity is defined as (delta vi delta vj)-1/2, and the valence molecular connectivity index (l chi v) is derived as a sum of these bond descriptions. The valence chi index is interpreted in terms of the information encoded, describing both the volume and electronic characteristics of bonds in molecules. Examples of close relationships with molecular volume and electronic properties are shown. A new way of estimating valence state electronegativity is proposed from a count of exterjacent electrons divided by the quantum number squared for at least the first three quantum levels.

Amino Acids↗
PubMed1981

Quantitation of solvent polarity based on molecular structure.

A numerical index is proposed that ranks solvents according to their polarity. It is based entirely on structure, encoding the relative content of exterjacent electrons in the molecule. The index is the first-order valence molecular connectivity index, 1Xv. The index is modified for the number of isolated functional groups in the molecule. A comparison with solvent polarity indexes based on several experimental methods reveals a good relationship. The polarity index proposed can be quickly calculated, it does not depend on the availability of the actual molecule, and it permits prediction of solvent polarity or the polarity of mixtures.

Chemical Phenomena↗
PubMed1980

Molecular structure influencing either a sweet or bitter taste among aldoximes.

A series of cyclohexylaldoximes was examined for their sweet or bitter taste using discriminant analysis. The structures of the molecules were described using molecular connectivity. A two-variable linear discriminant function and critical value were computed that correctly assigned 17 of the 20 molecules to their observed sweet or bitter taste categories. The same discriminant function can predict correctly the taste categories of seven of eight additional molecules.

Chemical Phenomena↗
PubMed1980

Use of molecular negentropy to encode structure governing biological activity.

A drug molecule is considered to be an information source with an information content available to receptive tissue. In nonspecific interactions, much of the information content has quality as judged by the receptor. Quantitation of the information content using Shannon's equation gives the molecular negentropy. This index is shown to rank molecules according to symmetry and to encode structural characteristics influencing physical properties and biological activity in certain cases.

Alcohols↗
PubMed1980

Structure-activity relationships of benzohydroxamic acid inhibitors of ribonucleotide reductase.

A structure-activity relationship study of 28 substituted benzohydroxamic acids that inhibit ribonucleotide reductase was undertaken to discern the structural features of the molecule contributing to the inhibitory potency of these compounds. An equation containing three molecular connectivity indexes, but not including Hammett sigma values, was developed which gives close correlation with observed values for ribonucleotide reductase inhibition. It is postulated that the inhibitory potency involves two parts of the benzohydroxamic acid molecule. One is the hydroxamic portion, which complexes with the metal component of the enzyme, providing a qualitative effect. The other is an interaction involving the benzene ring and its substituents and may provide the quantitative aspect of the observed inhibition values.

Chemical Phenomena↗
PubMed1980

Structural information from molecular connectivity 4 chi PC index.

The molecular connectivity 4 chi PC index was examined for its ability to describe uniquely molecules containing substituted benzene rings. The subgraphs comprising this index were shown to encode information about the number, placement, and type of ring substituents. Several examples illustrate the ability of the index to describe structure-influencing properties.

Aspergillus niger↗
PubMed1979

Molecular connectivity study of halocarbon anesthetics.

The structure--activity relationships of 45 halogenated hydrocarbons using molecular connectivity were studied. A very good correlation was obtained between the anesthetic activity and the molecular connectivity term o chi v in addition to the polar hydrogen factor, QH. The equation reported accounts for the quantifies the known structure--activity observations on general anesthetics. The results are discussed briefly with reference to the mechanisms of action of general anesthetics.

Anesthetics↗