Delocalized hole transport coupled to sub-ns tryptophanyl deprotonation promotes photoreduction of class II photolyases

Abstract

Ultrafast photoreduction of class II photolyases: the delocalized oxidation hole precedes distal tryptophanyl deprotonation and tyrosine oxidation.

Ultrafast photoinduced flavin dynamics in the unusual active site of the tRNA methyltransferase TrmFO

“…It should be noted in the simpler case of C53A that EAAS3, associated to the first photoproduct following the decay of the excited state, exhibits a marked dip around 564 nm, curiously evoking the shape of a SE band as seen in isotropic spectroscopy. A similar feature has previously been described in the context of the flavin photoreduction of a class II photolyase 50 and assigned to small remnants of excited flavin population.…”

Ultrafast photoreduction dynamics of a new class of CPD photolyases

“…The working buffer composition was: 50 mM phosphate at pH 8.0, 100 mM NaCl, 20% glycerol. D 2 O buffer was prepared by exchange with heavy water (99.9 atom % D, Sigma-Aldrich) as previously described [32,34].…”

“…Polarized transient absorption spectra were recorded by the pump-probe technique, with a white-light continuum probe, as previously described [32,34,39,46]. The pump pulses (70 fs) were tuned at 470 nm using a two-stage noncollinear optical parametric amplifier (NOPA, Clark MXR).…”

“…The polarized differential absorptions ( ΔA ∥ and ΔA ⟂ , not shown) were first corrected from the chirp of the probe beam, independently measured by recording cross-phase modulation [50] in the pure solvent. They were then used to calculate the isotropic transient absorptions ( ΔA iso ) and transient anisotropy (r) using the standard definitions of these quantities [32,34,39]. Note that rotational diffusion of DsNewPHL as a whole is not expected to play any role in the anisotropy dynamics during the time 3.2 ns window of our measurements.…”

“…However, a growing number of alternative electron transfer (ET) pathways have also been reported in different members of the PCSf. These include a non-canonical third Trp as final electron donor [25,26], the hypothetical role of an aspartate (Asp) as a stepping stone between Trps [27], the involvement of tyrosine (Tyr) residues as final or alternative donors [28][29][30][31][32], the absence of canonical proximal Trp [31], the presence of a completely different Trp triad [33][34][35], branched Trp chains [36], or the existence of a fourth distal donor (Trp or Tyr) in the ET chain [32,[37][38][39].…”