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Biomedical subjects

M L Bowers

Publications and source records attributed to M L Bowers.

4 recordsLinked to original sources
PubMed1999

Electrochemical detection of catecholamines at sub-5 fg levels by redox cycling.

Two simple modifications to a commercially available thin layer electrochemical detector cell permitted the attainment of ultra-low detection levels of two neurotransmitter catecholamines. An ESA model 5041 analytical cell was modified with a glassy carbon embedded ceramic composite electrode to allow the use of a thin 12 microm gasket. Also a capillary HPLC column was connected directly to the detector cell using a 30 microm i.d. fused silica capillary. These modifications permitted the extensive redox cycling of the electrochemically reversible catecholamines. The ensuing amplified analytical signal allowed the detector cell to achieve efficiencies of 1300%. This resulted in a mass limit of detection of 4 fg and a concentration limit of detection of 116 pM for dopamine with an S/N of 3.

Catecholamines↗
PubMed1991

A new analytical cell for carbohydrate analysis with a maintenance-free reference electrode.

An electrochemical cell for carbohydrates that uses a completely maintenance-free reference electrode has been introduced. The cell consists of three electrodes: a gold working electrode, a stainless steel counter electrode, and a palladium reference electrode. Other fluid-path cell components are fabricated of PEEK, Kel-F, and Teflon. The solid state palladium reference electrode requires no filling solutions and hence has no additional junction potentials. This versatile, pH-sensitive reference electrode allows the cell to compensate for pH shifts in the gold working electrode, resulting in better reproducibility. The cell functioned well for more than 2700 injections of a glucose standard over 6 weeks without maintenance of any kind. The control module uses a three pulse waveform that allows for selectable potentials and pulse durations as well as an adjustable delay period prior to the acquisition of the analytical signal.

Electrochemistry↗
PubMed1987

Further consideration of flavin coenzyme biochemistry afforded by geometry-optimized molecular orbital calculations.

Investigation of lumiflavin and several other isoalloxazine ring derivatives has been carried out by geometry-optimized molecular orbital calculations. The results have provided insight into the flexibility of the flavin cofactor in the reduced and oxidized states, the regions of the fused three-ring system that should play an important role in flavin electron transfers, and the structural and functional role of the xylene and heteroatomic portions of the flavin system. The significance of these results is reviewed in relation to the experimentally identified chemical and biochemical properties of the flavin nucleotide coenzymes.

Chemical Phenomena↗