Laboratoire P.A.S.T.E.U.R

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Repair of the (6–4) Photoproduct by DNA Photolyase Requires Two Photons

It takes two (photons) to tango: Single-turnover flash experiments showed that the flavoenzyme (6–4) photolyase uses a successive two-photon mechanism to repair the UV-induced T(6–4)T lesion in DNA (see picture). The intermediate (X) formed by the first photoreaction is likely to be the oxetane-bridged dimer T(ox)T. The enzyme could stabilize the normally short-lived T(ox)T, allowing repair to be completed by the second photoreaction.

Ultraviolet-Induced Fluorescence of Polydopamine-Coated Emulsion Droplets

Polydopamine (PDA), a multifunctional biomaterial with strong adhesion and coating properties, exhibits melanin-like optoelectronic properties but is virtually devoid of intrinsic fluorescence. Herein we disclose the first PDA-based system that can develop fluorescence without chemical manipulation.

Mass Transport at Infinite Regular Arrays of Electrodes

Mass transport at infinite regular arrays of microband electrodes was investigated theoretically and experimentally in unstirred solutions. Even in the absence of forced hydrodynamics, natural convection limits the convection-free domain up to which diffusion layers may expand. Hence, several regimes of mass transport may take place according to the electrode size, gap between electrodes, time scale of the experiment, and amplitude of natural convection. They were identified through simulation by establishing zone diagrams that allowed all relative contributions to mass transport to be delineated. Dynamic and steady-state regimes were compared to those achieved at single microband electrodes. These results were validated experimentally by monitoring the chronoamperometric responses of arrays with different ratios of electrode width to gap distance and by mapping steady-state concentration profiles above their surface through scanning electrochemical microscopy.

Biomolecular hydration dynamics: a jump model perspective

The dynamics of water molecules within the hydration shell surrounding a biomolecule can have a crucial influence on its biochemical function. Characterizing their properties and the extent to which they differ from those of bulk water have thus been long-standing questions. Following a tutorial approach, we review the recent advances in this field and the different approaches which have probed the dynamical perturbation experienced by water in the vicinity of proteins or DNA. We discuss the molecular factors causing this perturbation, and describe how they change with temperature. We finally present more biologically relevant cases beyond the dilute aqueous situation. A special focus is on the jump model for water reorientation and hydrogen bond rearrangement.

Photochemical properties of Spinach and its use in selective imaging

We propose a dynamic model that accounts for the photochemical behavior of the Spinach system, a recently described fluorescent probe for RNA imaging. We exploit the dynamic fluorogen exchange and the unprecedented photoconversion properties in a non-covalent fluorescence turn-on system to significantly improve signal-to-background ratio during long-term microscopy imaging.