title: Photodegradation of 5-methyltetrahydrofolate: biophysical aspects.
abstract: 5-methyltetrahydrofolate (5MTHF) absorbs UV radiation and has an absorption coefficient of 24250+/-1170 M(-1) cm(-1) at 290 nm. It has a weak fluorescence emission in the wavelength region around 360 nm. Our data demonstrated induction of 5-methyldihydrofolate by exposure to UVB and, after continues irradiation, p-aminobenzoyl-L-glutamic acid was found. The photodegradation of 5MTHF follows a first order kinetic with a degradation rate constant of 9.2 x 10(-3) min(-1) under our conditions (fluence rate of 2.15 mW cm(-2), exposure wavelengths from 280 to 350 nm). Our results indicate that a direct degradation of 5MTHF by UV exposure in humans in vivo is rather unlikely. 5MTHF mainly absorbs, and is degraded by, UVB and UVC, radiation that does not penetrate the earth's atmosphere and the human skin well.
authors.affiliation: Department of Radiation Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Montebello, N-0310 Oslo, Norway. arnfinn.hykkerud.steindal@rr-research.no
authors.forename: Arnfinn Hykkerud
authors.initials: AH
authors.lastname: Steindal
authors.forename: Asta
authors.initials: A
authors.lastname: Juzeniene
authors.forename: Anders
authors.initials: A
authors.lastname: Johnsson
authors.forename: Johan
authors.initials: J
authors.lastname: Moan
mesh_terms: D005492:Folic Acid / Q000031:analogs & derivatives* / Q000737:chemistry / Q000528:radiation effects; D008745:Methylation; D008958:Models, Molecular; D010777:Photochemistry; D013056:Spectrophotometry, Ultraviolet
chemical_list: C032418:5,11-methenyltetrahydrohomofolate; D005492:Folic Acid