Low-level chemiluminescence of N-beta-alanyl-L-histidine (L-carnosine)

Oxidized N-beta-Ala-L-His (L-carnosine) emitted low-level CL. The CL specificity was shown by experiments with L-carnosine from six separate vendors, several L-carnosine-like compounds, and nine different oxidizers. Purity of L-carnosine samples was analysed by RP-HPLC-MS, (1)H-NMR, MALDI-TOF-MS and ESI-MS. L-Carnosine CL magnitude varied with source; consequently, detection sensitivity was 5-100 nmol. CL of L-anserine (N-beta-Ala-1-methyl-L-His) was equal to or less than L-carnosine, depending upon oxidizer. H(5)IO(6) (2 mmol/L) in 11 mmol/L NaOH or 20 mmol/L K(3)Fe(CN)(6) + 10 mmol/L H(2)O(2) in 100 mmol/L NaOH were oxidizers of choice. Scavengers of (.)OH(-) radical quenched CL. Kinetic studies revealed a bi-phasic CL comprising a short-lived (<1 s) 'flash' and then prolonged ( approximately 2000 s) 'glow'. A structural basis and mechanism of L-carnosine CL are discussed. L-Carnosine CL could be useful for monitoring its level in biological samples.