Picomole analyses of tryptophan by derivatization to 9-hydroxymethyl-beta-carboline.
A new method specific for the determination of subpicomole quantities of tryptophan has been developed by elaboration of the Pictet-Spengler reaction. It permitted reproducible quantitation of tryptophan in less than 1 microliter of plasma ultrafiltrate or 1 mg of brain tissue. Samples deproteinized by trichloroacetic acid were boiled for 15 min with formaldehyde and potassium ferricyanide at controlled acidity, where tryptophan was converted to a single new product identified as 9-hydroxymethyl-beta-carboline. It was quantitated by either direct spectrofluorometry or a reversed-phase HPLC system developed for beta-carbolines. Under our conditions, peptides containing N-terminal tryptophan such as Trp-Leu and delta sleep-inducing peptide gave N-(9-hydroxymethyl-beta-carboline-3-carbonyl) peptides which retained all amino acid residues except tryptophan.
D000818:Animals; D001923:Brain Chemistry; D002243:Carbolines / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D007211:Indoles / Q000032:analysis*; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D013050:Spectrometry, Fluorescence / Q000379:methods*; D013056:Spectrophotometry, Ultraviolet; D014364:Tryptophan / Q000031:analogs & derivatives / Q000032:analysis* / Q000097:blood
D002243:Carbolines; D007211:Indoles; C039095:9-hydroxymethyl-beta-carboline; D014364:Tryptophan