UV-B mediated oxidative degradation of tryptophan residues to <i>N</i>-formylkynurenine in Pol λ and its N-terminal deletion mutants.

<p>(A) Normalized tryptophan fluorescence intensity per tryptophan residue in untreated control or (B) 4 h of UV-B exposed full length recombinant Pol λ, Del 1, Del 2 and Del 3 fragments. Fluorescence spectra were measured using excitation wavelength of 365 nm with the emission wavelengths ranging from 390 to 530 nm and emission scan speed of 240 nm/min, using 0.05 mg/mL of purified protein samples for analyzing the UV-B induced oxidation of tryptophan to <i>N</i>-formylkynurenine. (C) Tryptophan fluorescence spectra of 0.05 mg/ml of BSA (Sigma fraction V) under control or after 1 and 4 h of UV-B exposure. (D) Fluorescence spectra of control and UV-B BSA were measured using excitation wavelength of 365 nm with the emission wavelengths ranging from 390 to 530 nm to monitor the UV-B induced oxidation of tryptophan to <i>N</i>-formylkynurenine. (E) Normalized tryptophan fluorescence intensity per tryptophan residue in 4 h of UV-B exposed full length recombinant Pol λ and BSA. Fluorescence spectra were measured using excitation wavelength of 365 nm with the emission wavelengths ranging from 390 to 530 nm to compare the UV-B induced oxidation of tryptophan to <i>N</i>-formylkynurenine in Pol λ and BSA.