Conversion L-tryptophan to melatonin in the gastrointestinal tract: the new high performance liquid chromatography method enabling simultaneous determination of six metabolites of L-tryptophan by native fluorescence and UV-VIS detection.

Melatonin is a major biosynthetic product of pineal gland exerting a potent antioxidant and the reactive oxygen metabolites scavenging activities but the mechanism of formation of this indole at extrapineal sources has not been fully elucidated. It is known that the gastrointestinal (GI)-tract plays an important role as a source of melatonin synthesis but the conversion of L-tryptophan into melatonin in the GI-tract of experimental animals and humans should be further examined. In this study, the conversion of L-tryptophan to melatonin was determined in the serum collected from rats administered intragastrically with this amino acid acting as melatonin precursor.

Hypochlorite action on plasma fibronectin promotes its extended conformation in complexes with antibodies.

We investigated the influence of hypochlorite (HOCl/OCl-) on plasma fibronectin (Fn) aggregation and examined an affinity of Fn aggregates to Fn specific antibodies. Human plasma Fn HOCl/OCl(-)-mediated modification was monitored with differential OD method and with measurements of tryptophan fluorescence followed by acrylamide quenching of tryptophan emission. Antibody fibronectin complex formation was examined in ELISA systems with chemiluminescence (CL) detection.

The reactions of hypochlorous acid, the reactive oxygen species produced by myeloperoxidase, with lipids.

Myeloperoxidase (MPO), an abundant enzyme in phagocytes, has been implicated in the pathogenesis of various inflammatory diseases including atherosclerosis. The major oxidant produced by MPO, hypochlorous acid (HOCl), is able to modify a great variety of biomolecules by chlorination and/or oxidation. In this paper the reactions of lipids (preferentially unsaturated fatty acids and cholesterol) with either reagent HOCl or HOCl generated by the MPO-hydrogen peroxide-chloride system are reviewed.

Chemiluminescence of ABEI-labelled IgG triggered by the N-chloramine-H(2)O(2)-p-iodophenol system.

Light is emitted in systems containing N-chloramines or hypochlorite, H(2)O(2) and N-(4-aminobutyl)-N-ethylisoluminol (ABEI). The emission is enhanced by 4-iodophenol (PIP) in alkaline solution (1 mol/L NaOH), while at lower pH range (9-11) PIP is not only inactive but also its presence reduces chemiluminescence (CL) of the monochloramine-H(2)O(2)-ABEI system to the background. Two procedures for ABEI-labelled IgG assays were developed, with PIP in 1 mol/L NaOH and without PIP at pH 11, and the standard curves of free ABEI in these conditions were examined.