Kinetics and mechanism of degradation of klerval, a pseudo-tetrapeptide.

The degradation of klerval (I) was studied as a function of pH. The extent and routes of degradation were found to be pH-dependent. Under strongly acidic conditions (pH<2), the drug predominantly undergoes specific acid-catalyzed hydrolysis of the side-chain amide bond yielding II8), the drug undergoes specific base-catalyzed hyrolysis yielding II and epimerization generating D-epimer. The epimerization appears to occur via the succinimide intermediate in neutral pH region. With increasing pH, however, the epimerization rate increases due to direct epimerization of the peptides.

Method of analysis of recombinant acidic fibroblast growth factor by capillary electrophoresis.

Fibroblast growth factors are a series of well characterized proteins that have intriguing pharmacological properties. Acidic fibroblast growth factor (aFGF) recently appeared in the literature for its efficacy in spinal cord repair in rats. The protein has proven difficult to analyze by capillary electrophoresis, because it has a tendency to unfold, aggregate and precipitate, especially near and above physiological temperatures. By studying the turbidity of capillary electrophoresis running buffers and aFGF at 50 degrees C, conditions were found that stabilize the aFGF solution, thereby allowing the capillary electrophoretic separation of the protein from its recombinant production impurities. The buffer system employs 50 mM phosphate buffer at pH 2.5 with 0.25% hydroxypropylmethylcellulose (HPMC) additive. This system provided the best efficiency and selectivity of the systems studied and was developed for pharmaceutical purity analysis.

Cross-correlation in flow-injection analysis with parallel flow streams and amperometric detection.

Cross-correlation was implemented for flow-injection analysis by using two parallel flow lines, each with amperometric detectors, and driven by peristaltic pumps. One flow line was used to generate the reference signal for an analog correlator circuit and the other to generate the analyte signal. Cross-correlation was performed by multiplying these signals together at a time delay of zero, followed by low pass filtering. Using dopamine as a test system, improvements in signal-to-noise ratios of about two orders of magnitude were found for the correlation signal over the direct measurement of the electrode current.