Department News:

233rd American Chemical Society National Meeting
Chicago, Illinois: March 25-29, 2007  

Several members of the department attended the American Chemical Society National Meeting. Pictured (L-R): Dr. Geneive Henry, Richie Saing (2007), Adam Poncheri (2007), Brandi Swartz (2007), Heather Matta (2007) and Dr. Swarna Basu.

Development and implementation of a frequency-domain fluorescence lifetime instrument using lasers and light-emitting diodes, suitable for an undergraduate institution.

Adam J. Poncheri and Swarna Basu.

A frequency-domain fluorescence lifetime instrument, suitable for undergraduate courses (physical chemistry and biochemistry) as well as an undergraduate research program has been developed and implemented. Various excitation sources, such as light-emitting-diodes, a Nd3+:YAG laser and an Ar+-ion laser, have been incorporated into the system, in order to provide a wide range of wavelengths. This will allow the study of molecules ranging from organic dyes to proteins and other biomolecules. Signal modulation using an optical chopper and lock-in amplifier, as well as data acquisition and analysis using LabVIEW software is described. Preliminary experiments using a variety of organic dyes and lanthanide ions have been carried out. The lifetime information will be used to study inter- and intramolecular energy transfer processes and provide important physical and chemical information about the states of molecules.

Fluorescence quenching of Green Fluorescent Protein by various metal complexes and flavonoids: calculation of quenching constants, excited-state lifetimes and intermolecular distances.

Brandi L. Swartz, Deanna Snyder and Swarna Basu.

The interaction of various transition metal complexes and a plant flavonoid (kaempferol) with green fluorescent protein (GFP) as well as bovine serum albumin (BSA) has been investigated using steady-state fluorescence spectroscopy. The mechanism and efficiency of fluorescence quenching in various proteins by these molecules has been studied. The main goal of this project has been to understand the roles played by the location of amino acid residues as well as the identity of the transition metal in the fluorescence quenching process. GFP was chosen due to its unique spectral properties. The Stern-Volmer quenching constant was calculated for each system. The effect of ligand groups in transition metal complexes on observed quenching, possibly by energy transfer, is currently being studied. Fluorescence lifetime experiments using a laser-based instrument will be carried out in order to understand the properties of the excited state of the protein-quencher system.

Polyphenolic compounds from Hypericum punctatum

Heather Matta, Megan Janssen, Jacinth A. M. McKenzie, and Geneive E. Henry

The Hypericum plant genus is known most notably for its anti-inflammatory and anti-depressant activities related to Hypericum perforatum (St. John's Wort). HPLC profiling of H. perforatum and H. punctatum revealed close similarities in the chemical composition of the two species. Examination of the methanol extract of the aerial parts of H. punctatum has led to the isolation of polyphenols. The compounds were purified by silica gel and sephadex LH-20 chromatography, and the structures were determined on the basis of 2D NMR, IR and MS.

Triterpenes and other constituents of Hypericum prolificum

Ritchie S. Saing, Smita Raithore, and Geneive E. Henry

The Hypericum genus is a rich source of structurally diverse natural products. We recently reported the isolation of three new acylphloroglucinol derivatives from the hexane extract of the aerial parts of H. prolificum. We have subsequently examined the acetone extract of the plant, and have isolated triterpenes and other constituents. These compounds were purified by silica gel and Sephadex LH-20 column chromatography, and their structures were determined by IR, MS and NMR analyses.

231st American Chemical Society National Meeting
Atlanta, Georgia: March 26-30, 2006