Determination of delta13C values of valine in protein hydrolysate by gas chromatography-combustion isotope ratio mass spectrometry.
A gas chromatographic-combustion isotope ratio mass spectrometric (GC-C-IRMS) method for the determination of [1-13C]valine enrichments in protein hydrolysates is described. Using a quick derivatization method, delta13C values of the N-methoxycarbonyl methyl ester of valine can be determined from baseline separated GC peaks. Evaluation studies with respect to precision, accuracy, linearity, reduction capacity of the CuO combustion furnace and isotope dilution as a result of derivatization, showed that our GC-C-IRMS system allows robust measurement of enrichments of [1-13C]valine in the range 0 to 1.5 MPE (S.D.+/-0.01 MPE, n=3). Therefore this method is suited to determine fractional synthetic rates (FSRs) of proteins as low as one-tenth of the FSR of human albumin, in studies using a primed, continuous (6 h) infusion with [1-13C]valine plasma enrichments of approximately 15 MPE and an hourly sampling schedule.
University Hospital Vrije Universiteit, Department of Clinical Chemistry, Amsterdam, The Netherlands.
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W
Kulik
J A
JA
Meesterburrie
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C
Jakobs
K
K
de Meer
D002247:Carbon Isotopes; D002849:Chromatography, Gas / Q000379:methods*; D005069:Evaluation Studies as Topic; D005740:Gases; D006801:Humans; D006868:Hydrolysis; D013058:Mass Spectrometry / Q000379:methods*; D009589:Nitrogen Oxides / Q000737:chemistry; D015203:Reproducibility of Results; D012709:Serum Albumin / Q000737:chemistry*; D014633:Valine / Q000032:analysis*
D002247:Carbon Isotopes; D005740:Gases; D009589:Nitrogen Oxides; D012709:Serum Albumin; D014633:Valine