Hydroxyproline interference during the gas chromatographic analysis of D/Laspartic acid in human dentine

The proportion of D- to L-enantiomers of aspartic acid in metabolically iso lated proteins has been used by forensic scientists to estimate ape at deat h. We have demonstrated the interference of a derivative of hydroxyproline (N-TFA isopropyl Hyp eater) with the N-TFA isopropyl L-Aspartic (Asp) acid ester during gas chromatography of amino acids. This has serious implicatio ns for the accurate quantification of the D- to L-Asp ratio extracted from collagenous proteins. Having demonstrated the potential for this co-elution in amino acid standards, acid-soluble dentine proteins and non-mineralised collagen, we argue that this problem can be overcome either by high resolu tion separation or by analysis of the (Hyp-poor) non-collagenous protein fr action.