Photodynamics of Lys+-Trp protein motifs: hydrogen bonds ensure photostability.

Cation-pi interactions such as Lys(+)-Trp, are highly abundant structural motifs in proteins. Both, experimental and theoretical studies of small prototypical gas phase systems, H+Trp, H+Trp x (H2O)n and H+Gly-Trp, indicate such an arrangement as potential hot spot for photodamage and photoinstability. Here, we study the photodynamical properties of a Lys(+)-Trp pair in the protein human serum albumin (HSA) using nonadiabatic mixed time-dependent density functional theory/molecular mechanics simulations (TDDFT/MM).

On the proton transfer mechanism in ammonia-bridged 7-hydroxyquinoline: a TDDFT molecular dynamics study.

We have investigated the mechanism of proton transfer in the lowest photoexcited state of 7-hydroxyquinoline.(NH3)3 using TDDFT based molecular dynamics. We observe a concerted mechanism according to which all protons are transferred simultaneously in a fast process (approximately 100 fs) that amounts to the net transport of one proton from the oxygen to the nitrogen of 7-hydroxyquinoline.

New paradigm in molecular engineering of sensitizers for solar cell applications.

A novel thiocyanate-free cyclometalleted ruthenium sensitizer for solar cells is designed and developed. Upon anchoring to nanocrystalline TiO(2) films, it exhibits a remarkable incident monochromatic photon-to-current conversion efficiency of 83%. The solar cell employing a liquid-based electrolyte exhibits a short circuit photocurrent density of 17 mA/cm(2), an open circuit voltage of 800 mV, and a fill factor of 0.

Computer simulation of uranyl uptake by the rough lipopolysaccharide membrane of Pseudomonas aeruginosa.

Heavy metal environmental contaminants cannot be destroyed but require containment, preferably in concentrated form, in a solid or immobile form for recycling or final disposal. Microorganisms are able to take up and deposit high levels of contaminant metals, including radioactive metals such as uranium and plutonium, into their cell wall. Consequently, these microbial systems are of great interest as the basis for potential environmental bioremediation technologies.

Microsolvation effects on the excited-state dynamics of protonated tryptophan.

To better understand the complex photophysics of the amino acid tryptophan, which is widely used as a probe of protein structure and dynamics, we have measured electronic spectra of protonated, gas-phase tryptophan solvated with a controlled number of water molecules and cooled to approximately 10 K. We observe that, even at this temperature, the bare molecule exhibits a broad electronic spectrum, implying ultrafast, nonradiative decay of the excited state. Surprisingly, the addition of two water molecules sufficiently lengthens the excited-state lifetime that we obtain a fully vibrationally resolved electronic spectrum.