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Direct Ultraviolet Effects on Biological Systems
Published in Thomas M. Nordlund, Peter M. Hoffmann, Quantitative Understanding of Biosystems, 2019
Thomas M. Nordlund, Peter M. Hoffmann
DNA photolyase is a repair enzyme that reverts UV-induced thymine dimers in DNA by an electron transfer reaction between photoactivated FADH, an electron donor, and the dimer in the DNA-enzyme complex.18 Why should an electron transfer reaction be involved in repair? The original, undamaged thymines each had an intraring C=C double bond. The dimer, in effect, has one of each of the double bonds displaced to the adjacent thymine. There seems to be no electron transfer involved in the damage formation. Why should electron transfer be needed for reversion of the dimer? The answer: nature has apparently found it easier to destabilize the dimer structure by adding an extra electron, at relatively low energy cost, rather than to forcibly redirect the covalent bonds. Adding an extra electron to the dimer structure allows the intraring C=C double bond in one of the thymines to reform, as in the original thymine. The interthymine C–C bonds are then destabilized, causing them to break. But, you say, there is an extra electron floating around somewhere. That’s right—if nothing were done about the extra electron, this scheme would not work. One of the thymines has an extra electron that must go somewhere. Why not put the electron back where it came from? The electron-donating FADH only donated the electron because it was excited by a 300–500 nm photon (see below). After time has elapsed, the FAD excited state (it was the excited state that donated the electron) has decayed back to the ground state, so its more amenable to taking its electron back—which it does. Is that not incredibly clever?!
Industrial Applications of Bacterial Enzymes
Published in Pankaj Bhatt, Industrial Applications of Microbial Enzymes, 2023
Seki et al. reported that subtilisin (serine protease), obtained from Bacillus licheniformis, is an efficient skin exfoliator [192]. Commercial proteases used in the cosmetics industry are basically obtained by using recombinant DNA technology [189]. Another significant enzyme that has a role in the DNA repair mechanism is photolyase. When DNA repair is deficient and melanin cannot protect the skin from the damage caused by solar radiation, the risk of accumulating mutations that create cancer may increase. DNA photolyases overturn these lesions by abolishing thymine dimers, which play a significant role in the DNA repair mechanism [193, 194].
Dynamics of flavin containing radical pairs in SDS micellar media probed by static and pulse magnetic field effect and pulse ADMR
Published in Molecular Physics, 2019
Recently, the attraction to the photochemistry of the flavin systems has been increased in connection with the flavin containing photoreceptor molecule such as phototropin, photolyase, and cryptochrome [16–18]. Since some experimental evidence suggests that the photochemical dynamics of flavins has been considered as the source of the magneto reception of animals and plants [17,19,20], the MFE on the dynamics of RP comprised of flavin has received various attentions [21–23]. Since the flavin derivatives have a mixed character of hydrophobic and hydrophilic, the association feature of them to the hydrophobic molecular system is rather complicated. Previously, we have reported a dependence of the association feature on the hydrophobic character of flavin derivatives by using MFE [24]. Addition to the hydrophobic nature, the Coulomb forces of the ionic structure of the molecules also have a great contribution to the association of the molecules [25,26]. We can think that such character is one of the essential problems of the spin related reaction dynamics in the biological environments [27–29].