title: Properties of the humic-like material arising from the photo-transformation of L-tyrosine.
abstract: The UVB photolysis of L-tyrosine yields species with fluorescence and absorption spectra that are very similar to those of humic substances. By potentiometric measurements, chemical modeling and the application of NMR, mass spectrometry and laser flash photolysis, it was possible to get insights into the structural and chemical properties of the compounds derived by the L-tyrosine phototransformation. The photolytic process follows aromatic-ring hydroxylation and dimerization. The latter is presumably linked with the photoinduced generation of tyrosyl (phenoxy-type) radicals, which have a marked tendency to dimerize and possibly oligomerize. Interestingly, photoinduced transformation gives compounds with protogenic and complexation capabilities similar to those of the humic substances that occur naturally in surface waters. This finding substantiates a new and potentially important abiotic (photolytic) pathway for the formation of humic compounds in surface-water environments.
authors.affiliation: Università di Torino, Dipartimento Chimica, via P. Giuria, 7, 10125 Torino, Italy. Electronic address: silvia.berto@unito.it.
authors.forename: Silvia
authors.initials: S
authors.lastname: Berto
authors.affiliation: Università di Torino, Dipartimento Chimica, via P. Giuria, 7, 10125 Torino, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: De Laurentiis
authors.affiliation: Università di Torino, Dipartimento Chimica, via P. Giuria, 7, 10125 Torino, Italy.
authors.forename: Tiziana
authors.initials: T
authors.lastname: Tota
authors.affiliation: Università di Torino, Dipartimento Chimica, via P. Giuria, 7, 10125 Torino, Italy.
authors.forename: Enrico
authors.initials: E
authors.lastname: Chiavazza
authors.affiliation: Università di Torino, Dipartimento Chimica, via P. Giuria, 7, 10125 Torino, Italy.
authors.forename: Pier Giuseppe
authors.initials: PG
authors.lastname: Daniele
authors.affiliation: Università di Torino, Dipartimento Chimica, via P. Giuria, 7, 10125 Torino, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Minella
authors.affiliation: Università di Torino, Dipartimento di Scienze della Vita e Biologia dei Sistemi, Via Accademia Albertina 13, Torino 10123, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Isaia
authors.affiliation: Clermont Université, Université Blaise Pascal, Institut de Chimie de Clermont-Ferrand, BP 10448, F-63000 Clermont-Ferrand, France; CNRS, UMR 6296, ICCF, BP 80026, F-63177 Aubière, France.
authors.forename: Marcello
authors.initials: M
authors.lastname: Brigante
authors.affiliation: Università di Torino, Dipartimento Chimica, via P. Giuria, 7, 10125 Torino, Italy. Electronic address: davide.vione@unito.it.
authors.forename: Davide
authors.initials: D
authors.lastname: Vione
mesh_terms: D006812:Humic Substances / Q000032:analysis*; D008956:Models, Chemical; D010782:Photolysis; D014443:Tyrosine / Q000737:chemistry*
chemical_list: D006812:Humic Substances; D014443:Tyrosine
keywords: Aromatic amino acids; Ligands for metals; Photochemistry; Protogenic sites; Surface waters