Application of progress curve analysis to in situ enzyme kinetics using 1H NMR spectroscopy.

The steady-state kinetics of enzymes in tissues, cells, and concentrated lysates can be characterized using high-resolution nuclear magnetic resonance spectroscopy; this is possible because almost invariably there are differences in the spectra of substrates and products of a reaction and these spectra are obtainable even from optically opaque samples. We used 1H spin-echo NMR spectroscopy to study the hydrolysis of alpha-L-glutamyl-L-alanine by cytosolic peptidases of lysed human erythrocytes. Nonlinear regression of the integrated Michaelis-Menten expression onto the progress-curve data yielded, directly, estimates of Vmax and Km for the hydrolase; a procedure for analyzing progress curves in this manner was adapted and compared with a commonly used procedure which employs the Newton-Raphson algorithm.

Enkephalin degradation by human erythrocytes and hemolysates studied using 1H NMR spectroscopy.

High resolution (400 MHz) 1H spin-echo NMR spectroscopy was used to monitor the degradation of leucine-enkephalin, and peptide fragments of it, by human erythrocytes and hemolysates. We showed that leucine-enkephalin is rapidly degraded by the cytosolic peptidases of the human erythrocyte, and we have elucidated the most probable pathway of degradation. Computer simulations of the proposed pathway, using a model incorporating the experimentally derived steady-state kinetic parameters obtained for the individual enzyme steps, showed close agreement with the experimental results.

The assimilation of tri- and tetrapeptides by human erythrocytes.

Evidence is presented that tripeptides enter human erythrocytes via saturable transport system(s) at rates similar to those previously described for dipeptides (King, G.F. and Kuchel, P.

Spore Load of Ascosphaera Species on Emerging Adults of the Alfalfa Leafcutting Bee, Megachile rotundata.

The spore load of Ascosphaera species spores on larval chalkbrood cadavers and newly emergent adults of the alfalfa leafcutting bee, Megachile rotundata, was determined. The spore content of chalkbrood cadavers ranged from 3 x 10 to 5 x 10. Adults emerging through zero to nine cadavers carried spores on all body parts examined by scanning electron microscopy.

Clustering hypothesis of some high-temperature superconductors.

Cluster formation in metallic crystal lattices is important for most high-temperature superconductors.

Crystallography of new ternary borides.

The structure of new ternary rhodium borides has been determined. Isomorphism with the corresponding ternary cobalt borides is established.

High superconducting transition temperatures of new rare earth ternary borides.

A new group of ternary borides has been found that show either ferromagnetism or superconductivity. Their general formula is MRh(4)B(4) where M is a transition or rare-earth element. Their superconducting transition temperatures range from approximately 2.