Vicky L. Bevilacqua

Lactate dehydrogenase kinetics and inhibition using a microplate reader

A lactate dehydrogenase (LDH) enzyme kinetics laboratory experiment has been developed in which students obtain kinetic data using a microplate spectrophotometer (reader). These instruments have the capability of reading absorbances of many samples in a very short time frame. In this experiment 12 samples are prepared at a time and the absorbances read in less than 1 min. In a 3‐hr laboratory period, students collect data at five different substrate concentrations without inhibitor and also in the presence of two different concentrations of inhibitor. Students have enough time to repeat each part if they obtain too much scatter in their data. The enzyme examined, LDH, correlates with the study of metabolism and has particular relevance for students who are interested in medical careers. The LDH assay itself is not new, but the microplate format and the use of urea as a quench reagent are novel features. Students plot Michaelis–Menten and Lineweaver–Burk plots and calculate values for Vmax, apparent Vmax (Vmaxapp), Km, apparent Km (Kmapp), kcat, and KI. Students typically obtain results correctly showing that oxalic acid is a competitive inhibitor and oxamic acid is a noncompetitive inhibitor when lactate is the substrate of the reaction.

Main Group Metal Halide Complexes with Sterically Hindered Thioureas: Part XVII. The Crystal and Molecular Structures of Two New Tellurium Chloride Complexes with 1,3-dimethyl-2(3H)-imidazolethione

Abstract In an attempt to determine the crystal and molecular structure of previously reported [TeCl2(dmit)4] (1) [dmit=1,3-dimethyl-2(3H)-imidazolethione], recrystallization in hot acetonitrile yielded two new complexes, [TeCl2(dmit)2] (2) and [TeCl4(dmit)2] (3) as determined by X-ray crystallography. The structure of 2 consists of a cis-substituted square planar geometry with the thione rings both oriented on the same side of the TeS2Cl2 plane. The complex undergoes very slow decomposition in air. The structure of 3 is a near-octahedral arrangement with the thione ligands trans to each other

Further studies into the feasibility of using aqueous alum solutions in the destruction of VX

The destruction of phosphorus based chemical warfare agents using aqueous buffer mixtures of aluminum sul- fate (alum) and sodium aluminate is pursued. The production of VX (O-ethyl-S-(2-(diisopropylamino)ethyl)-methylphos- phonothiolate) hydrolysis products ethyl methyl phosphonic acid (EMPA), an aluminum complex of EMPA, and S-(2- (diisopropylamino)ethyl)methylphosphonothiolate (EA-2192) is characterized in acidic and basic alum buffers. The study employs 31 P high resolution magic angle nuclear magnetic resonance spectroscopy (HRMAS NMR) for both quantitative and qualitative analysis. The acidic buffer results in a slower reaction rate and is less effective than the basic buffer.