INVESTIGADORES
CABRERIZO franco Martin
congresos y reuniones científicas
Título:
Photochemistry of dihydrobiopterin and dihydroneopterin in aqueous solution
Autor/es:
M. VIGNONI; M. P. SERRANO; F. M. CABRERIZO; C. LORENTE; C. CLAPAROLS; A. H. THOMAS; E. OLIVEROS
Lugar:
Ferrara, Italia
Reunión:
Simposio; XXIII IUPAC Symposium on Photochemistry; 2010
Institución organizadora:
IUPAC
Resumen:
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Dihydrobiopterin (H2Bip)
and its oxidized analogue, biopterin (Bip), accumulate in the skin of patients
suffering vitiligo, a chronic depigmentation disorder in which the protection
against UV radiation fails [1]. Dihydroneopterin (H2Nep) and
neopterin (Nep) are secreted by human macrophages upon stimulation with
interferon-g [2]. The
photochemistry of H2Bip and H2Nep was studied in neutral
aqueous solutions upon UV-A irradiation (320-400 nm) at room temperature [3].
The photochemical reactions were followed by UV⁄vis spectrophotometry, HPLC,
and enzymatic methods for hydrogen peroxide (H2O2)
determination. Photoproducts were analyzed by means of electrospray ionization
mass spectrometry.
R
-(CHOH)2-CH3
Dihydrobiopterin
(H2Bip)
Biopterin
(Bip)
-(CHOH)2-CH2OH
Dihydroneopterin
(H2Nep)
Neopterin
(Nep)
-OH
Dihydroxanthopterin
(H2Xap)
-
Under anaerobic conditions,
excitation of H2Bip and H2Nep leads to the formation of
at least two isomeric dimers with molecular masses equal to exactly twice the
molecular mass of the reactants. In the presence of O2 the same
reactions were observed, but, in the case of H2Bip, a small
proportion of the reactant is converted into Bip. As the reaction proceeds and
enough Bip accumulates in the solution, a photosensitized process starts, where
Bip photoinduces the oxidation of H2Bip to Bip and H2O2
is formed. As a consequence, the rates of H2Bip consumption and Bip
formation increase as a function of irradiation time, resulting in an
autocatalytic photochemical process. Other oxidized pterins (Pt) can also act
as photosensitizers of H2Bip oxidation, thus revealing a general
mechanism. In the case of H2Nep, the oxidative pathway does not
occur. However, in the presence of an oxidized pterin, photosensitized
oxidation of H2Nep takes place to yield dihydroxantopterin (H2Xap).
[1] Rokos,
H.; Beazley, W. D.; Schallreuter, K. U. Biochem.
Biophys. Res. Commun., 2002, 292, 805811.
[2] Huber, C.; Fuchs, D.; Hausen, A.; Margreiter, R.; Reibnegger, G.;
Spielberger, M.; Wachter, H. J. Immunol.,
1983, 130, 10471050.
[3] Vignoni,
M.; Cabrerizo, F. M.; Lorente, C.; Claparols, C.; Oliveros, E.; Thomas, A. H. Org. Biomol. Chem. 2010, 8, 800-810.
