Lew M. Hryhorczuk

Metals in Anticancer Therapy: Copper(II) Complexes as Inhibitors of the 20S Proteasome

Selective 20S proteasomal inhibition and apoptosis induction were observed when several lines of cancer cells were treated with a series of copper complexes described as [Cu(L(I))Cl] (1), [Cu(L(I))OAc] (2), and [Cu(HL(I))(L(I))]OAc (3), where HL(I) is the ligand 2,4-diiodo-6-((pyridine-2-ylmethylamino)methyl)phenol. These complexes were synthesized, characterized by means of ESI spectrometry, infrared, UV-visible and EPR spectroscopies, and X-ray diffraction when possible. After full characterization species 1-3 were evaluated for their ability to function as proteasome inhibitors and apoptosis inducers in C4-2B and PC-3 human prostate cancer cells and MCF-10A normal cells. With distinct stoichiometries and protonation states, this series suggests the assignment of species [CuL(I)](+) as the minimal pharmacophore needed for proteasomal chymotryspin-like activity inhibition and permits some initial inference of mechanistic information.

Oxidation of Glutathione by [FeIV(O)(N4Py)]2+: Characterization of an [FeIII(SG)(N4Py)]2+ Intermediate

The mechanism of glutathione (GSH) oxidation by a nonheme ferryl species has been investigated. The reaction of [Fe(IV)(O)(N4Py)](2+) (1) with GSH in an aqueous solution leads to the rapid formation of a green intermediate, characterized as the low-spin ferric complex [Fe(III)(SG)(N4Py)](2+) (2) by UV-vis and electron paramagnetic resonance spectroscopies and by high-resolution time-of-flight mass spectrometry. Intermediate 2 decays to form the final products [Fe(II)(OH(2))(N4Py)](2+) and the disulfide GSSG over time. The overall reaction was fit to a three-step process involving rapid quenching of the ferryl by GSH, followed by the formation and decay of 2, which are both second-order processes.

A New Metabolic Pathway for N,N-Dimethyltryptamine

N,N-Dimethyltryptamine (DMT) undergoes a major structural alteration when added to whole human blood or its red blood cells in vitro. A new high-pressure liquid chromatography (HPLC) peak is present in extracts of these treated tissues. The compound responsible for this peak has been identified by ultraviolet spectrophotometry and by mass spectrometry as dimethylkynuramine (DMK). The enzyme responsible for this appears to be different from tryptophan 2,3-dioxygenase and also from indoleamine 2,3-dioxygenase.

Investigation of the Electronic, Photosubstitution, Redox, and Surface Properties of New Ruthenium(II)-Containing Amphiphiles

A series of pyridine- and phenol-based ruthenium(II)-containing amphiphiles with bidentate ligands of the following types are reported: [(L(PyI))Ru(II)(bpy)(2)](PF(6))(2) (1), [(L(PyA))Ru(II)(bpy)(2)](PF(6))(2) (2), [(L(PhBuI))Ru(II)(bpy)(2)](PF(6)) (3), and [(L(PhClI))Ru(II)(bpy)(2)](PF(6)) (4). Species 1 and 2 are obtained by treatment of [Ru(bpy)(2)Cl(2)] with the ligands L(PyI) (N-(pyridine-2-ylmethylene)octadecan-1-amine) and L(PyA) (N-(pyridine-2-ylmethyl)octadecan-1-amine). The imine species 3 and 4 are synthesized by reaction of [Ru(bpy)(2)(CF(3)SO(3))(2)] with the amine ligands HL(PhBuA) (2,4-di-tert-butyl-6-((octadecylamino)methyl)phenol), and HL(PhClA) (2,4-dichloro-6-((octadecylamino)methyl)phenol). Compounds 1-4 are characterized by means of electrospray ionization (ESI(+)) mass spectrometry, elemental analyses, as well as electrochemical methods, infrared and UV-visible absorption and emission spectroscopies. The cyclic voltammograms (CVs) of 1-2 are marked by two successive processes around -1.78 and -2.27 V versus Fc(+)/Fc attributed to bipyridine reduction. A further ligand-centered reductive process is seen for 1. The Ru(II)/Ru(III) couple appears at 0.93 V versus Fc(+)/Fc. The phenolato-containing 3 and 4 species present relatively lower reduction potentials and more reversible redox behavior, along with Ru(II/III) and phenolate/phenoxyl oxidations. The interpretation of observed redox behavior is supported by density functional theory (DFT) calculations. Complexes 1-4 are surface-active as characterized by compression isotherms and Brewster angle microscopy. Species 1 and 2 show collapse pressures of about 29-32 mN·m(-1), and are strong candidates for the formation of redox-responsive monolayer films.

Stability of a ferryl-peptide conjugate is controlled by a remote substituent.

The formation of a synthetic ferryl-peptide conjugate and mechanistic studies that elucidate its mode of decomposition are presented. A ferryl species is generated from a ligand-dipeptide conjugate 4. The ferryl species [Fe(IV)(4)(O)](2+), noted as compound 5, was characterized by UV-vis spectroscopy and by high-resolution electrospray mass spectrometry. The ferryl-peptide conjugate 5 is stable for over 1 h at room temperature. Ester derivatives of 5 decay at different rates, consistent with the remote ester group controlling the stability of the ferryl. The kinetic isotope effect value (4.5) and rho = -1.3 observed with ester derivatives suggest that the mechanism for decomposition of 5 follows a hydrogen-atom-transfer pathway. The formation and decay of 5 was fit to a two-step process, with the decay being unimolecular with respect to the ferryl 5.

Differential Effect of Carbidopa on the Concentration of Rat Pineal and Hypothalamic Indoleamines

Carbidopa, an aromatic acid decarboxylase inhibitor, has been shown to significantly decrease the pineal concentration of melatonin, N‐acetyl serotonin (NAS), serotonin (5‐HT), and 5‐hydroxyindoleacetic acid (5‐HIAA) but not the hypothalamic concentrations of these indoles. Increased levels of 5‐hydroxytryptophan (5‐HTP) indicate that carbidopa directly inhibits 5‐HTP decarboxylation, thus limiting 5‐HT production. Possible practical implications of selective inhibition of pineal indoleamines by carbidopa are discussed.