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C F Yam

Publications and source records attributed to C F Yam.

4 recordsLinked to original sources
PubMed1979

Kinetics of acetylcholinesterase immobilized on polyethylene tubing.

Acetylcholinesterase was covalently attached to the inner surface of polyethylene tubing. Initial oxidation generated surface carboxylic groups which, on reaction with thionyl chloride, produced acid chloride groups; these were caused to react with excess ethylenediamine. The amino groups on the surface were linked to glutaraldehyde, and acetylcholinesterase was then attached to the surface. Various kinetic tests showed the catalysis of the hydrolysis of acetylthiocholine iodide to be diffusion controlled. The apparent Michaelis constants were strongly dependent on flow rate and were much larger than the value for the free enzyme. Rate measurements over the temperature range 6-42 degrees C showed changes in activation energies consistent with diffusion control.

Acetylcholinesterase↗
PubMed1978

Synthesis, opiate receptor affinity, and conformational parameters of [4-tryptophan]enkephalin analogues.

A series of analogues of the opioid peptide enkephalin with tryptophan substituted for phenylalanine in position 4 was synthesized by the solid-phase method. The [Trp4]enkephalin analogues and the corresponding [Phe4]enkephalin analogues displayed nearly parallel affinities in the opiate receptor binding assay throughout the series. In a conformational study fluorescence parameters were measured and intramolecular Tyr-Trp distances were estimated on the basis of resonance energy transfer experiments. No gross conformational differences were observed between analogues with widely differing opiate receptor affinity; however, small but significant changes in the intramolecular distance between the phenol ring and the indole moiety and/or in their relative orientation became apparent in some compounds. Identical intramolecular distances of 9.3 +/- 0.2 angstrom between the two aromatic rings were obtained with [Trp4,Met5]enkephalin, [Trp4,Leu5]enkephalin, and the N-terminal tetrapeptide comprised in the latter two analogues, indicating the existence of folded conformationas in 2 X 10(-5) M aqueous solution and demonstrating conformational analogy between these three peptides. The conformational parameters are discussed in relation to the observed affinities and the putative opiate receptor topography.

Amino Acid Sequence↗
PubMed1977

A sensitive radiometric assay for cysteic acid decarboxylase activity in crude enzyme preparations of rat liver and brain.

1. A method is described for the synthesis of L-[U-14C]cysteic acid from L-[U-14C] cysteine hydrochloride and for its subsequent utilisation as a substrate for cysteic acid decarboxylase activity in liver and brain. 2. The enzyme determination relies on the entrapment of radio-labelled carbon dioxide in Hyamine hydroxide. 3. The assay is sensitive, reliable and convenient and is particularly suitable for measuring the activity of the decarboxylase in crude enzyme preparations.

Animals↗