Biomedical subjects

C J Markworth

Publications and source records attributed to C J Markworth.

3 recordsLinked to original sources

PubMed2001

Inhibition of potato polyphenol oxidase by anions and activity in various carboxylate buffers (pH 4.8) at constant ionic strength.

The activity of potato polyphenol oxidase (tyrosinase) toward DL-3,4-dihydroxyphenylalanine (K(M) 5.39 mM) was studied using a variety of carboxylate buffers at a common pH and ionic strength. Enzyme activity, greatest in citrate and least in oxalate, correlated with increasing carboxyl concentration and molecular mass. The lower activity in oxalate was attributed to more effective chelation of a copper(II) form of the enzyme by the oxalate dianion. Sodium halide salts inhibited the enzyme. Although there was little difference in inhibition between sodium and potassium salts, the degree and type of inhibition was anion dependent; K(is), values for NaCl and KCl, (competitive inhibitors) were 1.82 and 1.62 mM, whereas Na(2) SO(4) and K(2) SO(4) (mixed inhibitors) had K(is) and K(ii) values in the 250 to 450 mM range.

Buffers↗

PubMed1998

Ratio encoding combinatorial libraries with stable isotopes and their utility in pharmaceutical research.

Combinatorial libraries are an important tool for lead discovery in the pharmaceutical industry. Advances in high throughput screening coupled with combinatorial chemistry can significantly reduce the time to find lead compounds. A major difficulty in developing large combinatorial libraries is the ability to identify active compounds. This paper describes a rapid and sensitive encoding/decoding methodology that utilizes stable isotopes and mass spectrometry. The ability of mass spectrometry to precisely determine the intensity of isotopic abundances provides a unique encoding strategy employing synthetically generated ratios of stable isotopes in a compound as the code. The application of ratio encoding is demonstrated using peptoid and imidazole chemistries. Supporting data demonstrate that the incorporation of one or more stable isotopes using unique-predetermined ratios can encode chemical libraries. In addition, the presence of a unique isotopic pattern in a ligand can facilitate the pharmacokinetic analysis. Isotope incorporation into a compound and subsequently into its metabolites reliably distinguishes products from other molecules in the mass spectrum. This is illustrated by metabolic analyses of peptoid and imidazole compounds.

Amino Acid Sequence↗

PubMed1996

Isotope or mass encoding of combinatorial libraries.

BACKGROUND: Combinatorial chemistry using solid-phase synthesis is a rapidly developing technology that can result in a significant reduction in the time required to find and optimize lead compounds. The application of this approach to traditional medicinal chemistry has led to the construction of libraries of small organic molecules on resin beads. A major difficulty in developing large combinatorial libraries is the lack of a facile encoding and decoding methodology to identify active compounds. RESULTS: Several encoding schemes are described which use the ability of mass spectrometry to ascertain isotopic distributions. Molecular tags are attached to resin beads in parallel or on the linker used for chemical library synthesis. The tags are encoded via a controlled ratio of a number of stable isotopes on the tagging molecules, and range from a single to a complex isotopic distribution. CONCLUSIONS: A novel coding scheme is described that is useful for the generation of large encoded combinatorial libraries. The code can be cleaved after assay and analyzed by mass spectrometry in an automated fashion. An important element of the combinatorial discovery process is the ability to extract the structure-activity relationship (SAR) information made available by library screening. The speed and sensitivity of the mass-encoding scheme has the potential to determine the full SAR for a given library.

Chemistry, Organic↗