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Formation and destruction of photoinduced paramagnetic centers in melanin-containing fungi
Abstract:
Irradiation of the melanin-containing fungi Cladosporium transchelii, its pigmented mutants, Stemphyllium ilicis, Oidiodendron cerealis, and isolated melanin pigment with UV or visible light leads to an increase in the concentration of paramagnetic centers (PC) in melanin pigments, recorded by the EPR technique. Differences were established in the reaction of melanin of UV-sensitive and UV-resistant cultures to illumination. Paramagnetic centers are generated by a single-quantum mechanism (light with lambda less than 900 nm was active). A mechanism is proposed for processes occurring during illumination of dark-pigmented subjects, which includes photoinduced electron transport in melanin and dark recombination of the PC formed in the process.
Insights
Illuminating fungi and melanin pigments with light increases paramagnetic centers (PC). This photoinduced electron transport mechanism differs between UV-sensitive and UV-resistant fungal melanin.
Area of Science:
- Biophysics
- Mycology
- Photochemistry
Background:
- Melanin pigments in fungi are known for their protective roles.
- The interaction of fungal melanin with light, particularly UV and visible spectra, is not fully understood.
- Paramagnetic centers (PC) in biological molecules can be influenced by light exposure.
Purpose of the Study:
- To investigate the effect of UV and visible light irradiation on melanin pigments in various fungi.
- To characterize the generation mechanism of paramagnetic centers (PC) in melanin upon illumination.
- To explore potential differences in light response between UV-sensitive and UV-resistant fungal melanin.
Main Methods:
- Irradiation of fungal cultures (Cladosporium transchelii, Stemphyllium ilicis, Oidiodendron cerealis) and isolated melanin with UV and visible light.
- Quantification of paramagnetic centers (PC) using Electron Paramagnetic Resonance (EPR) spectroscopy.
- Analysis of light wavelength dependency for PC generation.
Main Results:
- Irradiation significantly increased PC concentration in melanin pigments across tested fungi.
- Distinct differences were observed in the light-induced PC generation between UV-sensitive and UV-resistant fungal strains.
- Paramagnetic centers were generated via a single-quantum mechanism, with light wavelengths below 900 nm being active.
Conclusions:
- Fungal melanin undergoes photoinduced changes upon irradiation, leading to an increase in paramagnetic centers.
- A proposed mechanism involves photoinduced electron transport within melanin followed by dark recombination of generated PC.
- The differential response of melanin from UV-sensitive and UV-resistant fungi suggests varied photoprotective or photoresponsive strategies.