ArticleJournal of biochemistry2026
Quantification of L- and D-enantiomers of proline, trans-4-hydroxyproline and cis-4-hydroxyproline in natural samples using differential labelling with 12C- and 13C6-dabsyl chloride, chiral separation and liquid chromatography-mass spectrometry.
Article in Journal of biochemistry, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.
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Abstract
L-Proline (L-Pro) and trans-4-hydroxy-L-proline (t-4-HPL) are major components of collagen and plant cell wall proteins. During their breakdown, free L-Pro and t-4-HPL are produced abundantly and play unique biological roles through complex metabolisms including isomerization. Therefore, it is essential to quantify all the six stereoisomers of proline and 4-hydroxyproline. Here, analytes were first labelled with 12C-dabsyl group, which has strong red colour and stability under light. Secondly, each of the 13C6-dabsyl stereoisomers were added to 12C-dabsylated samples as internal standards before cleanup. Finally, the molar ratio of 12C- and 13C6-dabsyl analytes was determined as the intensity ratio of doublet molecular ions with m/z difference of six in mass spectra, which were obtained by subjecting the cleaned sample to capillary chromatography-mass spectrometry. The total amounts of proline, t-4-HP and cis-4-hydroxyproline were determined using the standard addition method. Linear calibration curves (R2 > 0.99) were obtained in the range of 10-1000 pmol. To determine the molar ratio of D- and L-enantiomers, enantiopure dabsyl analyte fraction was obtained using reverse-phase and chiral chromatography. Mouse serum contained 0.20 μmol/L trans-4-hydroxy-D-proline. Achatina fulica haemolymph contained 0.070 μmol/L D-proline. The Santalum album wood powder contained all the 6 stereoisomers and unexpectedly the D-enantiomer was dominant for trans-4-hydroxyproline.
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