Analysis of enzyme kinetic measurements for an organic-medium biocatalyst

Summary Enzyme kinetic data for oxidation of phenolic substrates in an organic-medium polyphenol oxidase biocatalytic system, were analysed by techniques relating specifically to non-aqueous biocatalysis. The results were related to steric, hydrophobic, and electronic character in the substrates; steric and hydrophobic character were found to influence the kinetics. Molecular modelling and kinetic results together gave an estimate of steric capacity in the binding site in the organic medium.     

Hemodynamics of miniature swine during +Gz stress with and without anti-G support

Nine unanesthetized, chronically instrumented, female miniature swine (MS) (avg wt, 39.7 kg) were exposed to head-to-tail inertial load (+Gz) levels of +3, +5, and +7 Gz for 60 s, with and without anti-G-suit inflation. Venous flow (VF) was measured by an electromagnetic flow sensor around the inferior thoracic vena cava at the diaphragm. Central venous pressure (CVP), abdominal venous pressure (AVP), eye-level blood pressure (ELBP), and esophageal pressure (EP) were also measured before, during, and after +Gz. There was a progressive significant decrease from control of both ELBP (P less than 0.001) and VF (P less than 0.05) during the three +Gz exposures, both with and without G-suit inflation. Without G-suit inflation, most of the MS were unable to tolerate +5 and +7 Gz. Although VF was significantly (P less than 0.02) improved by G-suit inflation during +Gz there was no significant difference in VF between the three +Gz levels, with or without G-suit inflation. The MS does a spontaneous straining maneuver (cyclic Valsalva) during +Gz with G-suit support. Using EP as a trigger, the data were grouped as strain or no strain (relaxation). A continuous AVP-to-CVP gradient existed during G-suit inflation, which increased dramatically during no strain with increasing +Gz, and was associated with an increase in VF. Thus, the majority of VF occurred during relaxation between strains, even though relaxation time was shortened as +Gz increased. Although ELBP is obviously dependent on cardiac output and venous return, the progressive reduction in ELBP with increased +Gz loads was not significantly related to changes in VF at the diaphragm which was maintained, although at a reduced rate, by the AVP-to-CVP gradient during G-suit inflation.     

Purification of hog renin by affinity chromatography using the synthetic competitive inhibitor (D-Leu6)octapeptide.

The renin substrate analog His-Pro-Phe-His-Leu-D-Leu-Val-Tyr ([D-Leu6]-octapeptide) acts as a potent inhibitor of renin because of the D-amino acid substitution at the cleavage site. This inhibitor was coupled to CNBr-activated Sepharose 4B to yield a support for affinity chromatography. Hog renin with a specific activity of 1.2 Goldblatt units/mg was in one step purified 195-fold to a final specific activity of 234 Goldblatt units/mg. Application of a pH gradient from 5.0 to 7.5 to the support was found to be the most successful elution program, probably because the [D-Leu6]-octapeptide is not an inhibitor for renin at neutral pH.