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F Chiu

Publications and source records attributed to F Chiu.

3 recordsLinked to original sources
PubMed1996

Carboxyl-terminal modification influences subunit assembly of sickle hemoglobin beta chains.

The subunit assembly properties of isolated beta and Des(His-146,Tyr-145) beta chains of sickle hemoglobin were investigated by isoelectric focusing over a protein concentration range from 500-125 microM in heme. Two components (presumably tetramer and monomer) and three components (designated tetramer, dimer and monomer) were visualized for beta s and Des(His-146,Tyr-145) beta s chains, respectively. Intensitometric quantitation of Des(His-146,Tyr-145) beta s chains demonstrated a similar distribution of all three structural components before and after the addition of their heteropartner alpha chains. This is in direct contrast to the reported preferential loss of Des(His-146,Tyr-145) beta A monomer species upon assembly and points to a major role of the beta 6 residue in the overall structural homeostasis of carboxylterminal modified human beta chains.

Biopolymers↗
PubMed1990

Analysis of plasma hippurate in humans using gas chromatography-mass spectrometry: concentration and incorporation of infused [15N]glycine.

To allow in vivo determination of synthetic rates for individual proteins, physiological incorporation of infused [15N]glycine into urinary hippuric acid has been used as an indicator of intrahepatic tracer dilution. Although the kidneys might contribute to hippurate production, the relationship between hepatic, plasma, and urinary hippurate has not yet been established in humans. To further investigate these issues we developed a fast, sensitive, and reliable method for measuring simultaneously hippurate concentrations and in vivo tracer incorporation into hippurate in plasma and urine using stable isotopes and gas chromatography-mass spectrometry. We then tested this assay under several experimental conditions. Reference compounds [( 15N]- and [ring-2H5]hippurate) were synthesized and gave linear standard curves. Postabsorptive hippurate plasma levels in healthy subjects ranged from 1.2 to 10.5 microM and protein binding was 79 +/- 6% (mean +/- SD). Following a bolus dose of [15N]glycine tracer appeared in plasma hippurate; enrichment in hippurate was indistinguishable from that in glycine after an equilibration period of 20 min, indicating a close relationship between intracellular glycine and plasma hippurate. A 16-h infusion of [15N]glycine resulted in identical enrichment levels in urinary and plasma hippurate; glycine enrichment in a hepatic export protein (VLDL-ApoB) was approaching plasma hippurate but not plasma free glycine enrichment. The ability to monitor plasma hippurate is of practical advantage compared to the sampling of urine. Furthermore it allows the monitoring of rapid events in the intrahepatic dilution of an infused glycine tracer. This assay may, therefore, become an important tool in the study of hepatic protein metabolism.

Administration, Oral↗