Biomedical subjects

Gerald H Lushington

Publications and source records attributed to Gerald H Lushington.

24 records · Page 2Linked to original sources

PubMed2003

Discovery and structural modification of inhibitors of methionine aminopeptidases from Escherichia coli and Saccharomyces cerevisiae.

A series of pyridine-2-carboxylic acid derivatives were synthesized according to the leads from the screening, and potent inhibitors have been obtained by structural modification. They have shown submicromolar inhibition of the enzymes (for example, for 9n, IC(50) = 130 nM for EcMetAP1 and IC(50) = 380 nM for ScMetAP1). They represent small-molecule MetAP inhibitors with novel structures different from alkylating fumagillin derivatives and peptidic bestatin-based MetAP inhibitor.

Aminopeptidases↗

PubMed2003

First isocyanoazulene and its homoleptic complexes.

An efficient synthesis of remarkably stable 6-isocyanoazulene (CN6Az), the first nonbenzenoid organic isocyanide, is described. Its superb pi-accepting potential as a ligand was demonstrated through cyclic voltammetry studies on the binary complexes [Cr(CN6Az)6]0/+. The paramagnetic shift patterns for [Cr(CN6Az)6]+, the only azulenic pi-system studied by paramagnetic NMR, suggest that Cr(dpi) --> CN6Az(ppi*) electron delocalization involves both rings of the azulenyl substituents in [Cr(CN6Az)6]+. This conclusion is supported by density functional theory calculations on the complex [Cr(CN6Az)6][BF4].

Azulenes↗

PubMed2002

First homoleptic complexes of isocyanoferrocene.

Interaction of aminoferrocene with a 65/35 mol % mixture of phenyl formate/phenol followed by subsequent dehydration of the resulting ferrocenylformamide with POCl3 produced a high yield of air- and thermally stable, peach-colored isocyanoferrocene (CNFc). Combining 6 equiv of CNFc with bis(naphthalene)chromium(0) afforded orange-red Cr(CNFc)6, the first homoleptic complex of CNFc. Successive one-electron oxidations of the latter with Ag+ quantitatively produced saddle-brown [Cr(CNFc)6]+ and forest-green [Cr(CNFc)6]2+. The compounds [Cr(CNFc)6]0,1+,2+ are air-, light-, and thermally robust and are remarkable due to the incorporation of seven potentially electroactive transition metal ions within a relatively compact ML6 motif. Their properties demonstrate that the pi-accepting potential of the ferrocenyl substituent, customarily compared to an alkyl group, may have been underestimated. Indeed, the donor/acceptor ratio of the CNFc ligand appears to be similar to those of aryl isocyanides but quite different from those of alkyl isocyanides. Spectroscopic (including multinuclear paramagnetic NMR), magnetic, structural, and electrochemical characteristics of the above substances are discussed. In addition, a DFT analysis of the Frontier molecular orbitals of CNFc is presented.

Crystallography, X-Ray↗

PubMed2002

How the mutation glycine96 to alanine confers glyphosate insensitivity to 5-enolpyruvyl shikimate-3-phosphate synthase from Escherichia coli.

The enzyme 5-enolpyruvyl shikimate-3-phosphate (EPSP) synthase (EC 2.5.1.19) is essential for the biosynthesis of aromatic compounds in plants and microbes and is the unique target of the herbicide glyphosate. One of the first glyphosate-insensitive enzymes reported was a Gly96Ala mutant of EPSP synthase from Klebsiella pneumoniae. We have introduced this single-site mutation into the highly homologous EPSP synthase from Escherichia coli. The mutant enzyme is insensitive to glyphosate with unaltered affinity for its first substrate, shikimate-3-phosphate (S3P), but displays a 30-fold lower affinity for its second substrate, phosphoenolpyruvate (PEP). Using X-ray crystallography, we solved the structure of Gly96Ala-EPSP synthase liganded with S3P to 0.17 nm resolution. The crystal structure shows that the additional methyl group from Ala96 protrudes into the active site of the enzyme. While the interactions between enzyme and S3P remain unaffected, the accessible volume for glyphosate binding is substantially reduced. Exploiting the crystallographic results for molecular modeling, we demonstrate that PEP but not glyphosate can be docked in the Gly96Ala-modified binding site. The predicted PEP binding site satisfies the earlier proposed interaction pattern for PEP with EPSP synthase and corroborates the assumption that glyphosate and PEP target the same binding site.

3-Phosphoshikimate 1-Carboxyvinyltransferase↗

PubMedDate not supplied

Solution-phase parallel synthesis of a library of delta(2)-pyrazolines.

A parallel synthesis of a library (80 members) of 2-pyrazolines in solution phase is described. The 2-pyrazoline core was accessed through the [3 + 2] cycloaddition of nitrilimines with enoyl oxazolidinones. The cycloaddition provided two regioisomers, the major product being the C regioisomer. The oxazolidinone moiety was further reduced to the primary alcohol, producing another library of 5-hydroxymethyl-2-pyrazolines. The Lipinski profiles and calculated ADME properties of the compounds are also reported.

Combinatorial Chemistry Techniques↗

PubMedDate not supplied

Stability and electronic properties of nitrogen nanoneedles and nanotubes.

The electronic structures and stability of nitrogen nanostructures, nanotubes, and fiberlike nanoneedles of various diameters, formed by units N2m (m = 2-6), were studied by quantum chemistry computational modeling methods. The geometrical structures with various cross-sections and terminal units, their energetic stability, and their rather peculiar electron density distributions were investigated. The tightest nitrogen nanoneedle (NNN) studied theoretically in this work is the structure (N4n with D2h symmetry, whereas the nitrogen nanotube (NNT) with the largest diameter discussed here is the structure (N12)n with D2 symmetry. These families of NNNs and NNTs can be considered as nanostructures not only for potential applications as devices in nanotechnology or as possible scaffold structures but also as ligands in synthetic chemistry and high-energy density materials (HEDMs). As a consequence of the lone-pair electrons present around the walls of these NNNs and NNTs, these nitrogen nanostructures and the nitrogen nano-bundles (NNB) formed by aligning and combining them using intermediate carbon atoms, can have highly variable electronic properties controlled by the changing charge environment. In particular, for extended systems based on the units studied here, the band gaps of each of these systems can be affected greatly by the local charge of the environment.

Journal Article↗