Photoexcitation of the P4480 state induces a secondary photocycle that potentially desensitizes channelrhodopsin-2

Channelrhodopsins (ChRs) are light-gated cation channels. In spite of their wide use to activate neurons with light, the photocurrents of ChRs rapidly decay in intensity under both continuous illumination and fast trains of light pulses, broadly referred to as desensitization. This undesirable phenomenon has been explained by two interconnected photocycles, each of them containing a nonconductive dark state (D1 and D2) and a conductive state (O1 and O2). While the D1 and O1 states correspond to the dark-state and P3520 intermediate of the primary all-trans photocycle of ChR2, the molecular identity of D2 and O2 remains unclear. We show that P4480, the last intermediate of the all-trans photocycle, is photoactive. Its photocycle, characterized by time-resolved UV/vis spectroscopy, contains a red-shifted intermediate, I3530. Our results indicate that the D2 and O2 states correspond to the P4480 and I3530 intermediates, connecting desensitization of ChR2 with the photochemical properties of the P4480 intermediate

Protein dynamics observed by tunable mid-IR quantum cascade lasers across the time range from 10 ns to 1 s

We have developed a spectrometer based on tunable quantum cascade lasers (QCLs) for recording time-resolved absorption spectra of proteins in the mid-infrared range. We illustrate its performance by recording time-resolved difference spectra of bacteriorhodopsin in the carboxylic range (1800–1700 cm− 1) and on the CO rebinding reaction of myoglobin (1960–1840 cm− 1), at a spectral resolution of 1 cm− 1. The spectrometric setup covers the time range from 4 ns to nearly a second with a response time of 10–15 ns. Absorption changes as low as 1 × 10− 4 are detected in single-shot experiments at t > 1 μs, and of 5 × 10− 6 in kinetics obtained after averaging 100 shots. While previous time-resolved IR experiments have mostly been conducted on hydrated films of proteins, we demonstrate here that the brilliance of tunable quantum cascade lasers is superior to perform ns time-resolved experiments even in aqueous solution (H2O)

Protein conformational changes and protonation dynamics probed by a single shot using quantum-cascade-laser-based IR spectroscopy

Mid-IR spectroscopy is a powerful and label-free technique to investigate protein reactions. In this study, we use quantum-cascade-laser-based dual-comb spectroscopy to probe protein conformational changes and protonation events by a single-shot experiment. By using a well-characterized membrane protein, bacteriorhodopsin, we provide a comparison between dual-comb spectroscopy and our homebuilt tunable quantum cascade laser (QCL)-based scanning spectrometer as tools to monitor irreversible reactions with high time resolution. In conclusion, QCL-based infrared spectroscopy is demonstrated to be feasible for tracing functionally relevant protein structural changes and proton translocations by single-shot experiments. Thus, we envisage a bright future for applications of this technology for monitoring the kinetics of irreversible reactions as in (bio-)chemical transformations

Photoreactions and Structural Changes of Anabaena Sensory Rhodopsin

Anabaena sensory rhodopsin (ASR) is an archaeal-type rhodopsin found in eubacteria. The gene encoding ASR forms a single operon with ASRT (ASR transducer) which is a 14 kDa soluble protein, suggesting that ASR functions as a photochromic sensor by activating the soluble transducer. This article reviews the detailed photoreaction processes of ASR, which were studied by low-temperature Fourier-transform infrared (FTIR) and UV-visible spectroscopy. The former research reveals that the retinal isomerization is similar to bacteriorhodopsin (BR), but the hydrogen-bonding network around the Schiff base and cytoplasmic region is different. The latter study shows the stable photoproduct of the all-trans form is 100% 13-cis, and that of the 13-cis form is 100% all-trans. These results suggest that the structural changes of ASR in the cytoplasmic domain play important roles in the activation of the transducer protein, and photochromic reaction is optimized for its sensor function

A photoswitchable helical peptide with light-controllable interface / transmembrane topology in lipidic membranes

This files collects data from the paper "A photoswitchable helical peptide with light-controllable interface / transmembrane topology in lipidic membranes" by Mónica Gutiérrez-Salazar, Eduardo Santamaría-Aranda, Louise Schaar, Jesús Salgado, Diego Sampedro, Victor A. Lorenz-Fonfria. bioRxiv 2021.03.10.434736; doi: https://doi.org/10.1101/2021.03.10.434736 The ".ogg" file can be open with the software Origin or OriginPro (https://www.originlab.com). A free-of-charge viewer is available at https://www.originlab.com/viewer

Retinal vibrations in bacteriorhodopsin are mechanically harmonic but electrically anharmonic: evidence from overtone and combination bands

These files collects the experimental data presented in the Figures from the manuscript:Lorenz-Fonfria VA, Yagi K, Ito S and Kandori H (2021) Retinal Vibrations in Bacteriorhodopsin are Mechanically Harmonic but Electrically Anharmonic: Evidence From Overtone and Combination Bands. Front. Mol. Biosci. 8:749261. doi: 10.3389/fmolb.2021.749261 The ".ogg" file can be open with the software Origin or OriginPro (https://www.originlab.com). A free-of-charge viewer is available at https://www.originlab.com/viewer/THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

Retinal vibrations in bacteriorhodopsin are mechanically harmonic but electronically anharmonic: evidence from overtone and combination bands

This files collects data from a manuscript submitted with the tittle "Retinal vibrations in bacteriorhodopsin are mechanically harmonic but electronically anharmonic: evidence from overtone and combination bands" by Victor A. Lorenz-Fonfria, Kiyoshi Yagi, Shota Ito, and Hideki Kandori. The ".ogg" file can be open with the software Origin or OriginPro (https://www.originlab.com). A free-of-charge viewer is available at https://www.originlab.com/viewer/THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

Eficiencia energética.- Estudio de la viabilidad técnica y económica para la optimización de los sistemas térmicos en piscinas climatizadas en Murcia

RESUMEN En el presente trabajo se presenta el estudio de viabilidad técnica y económica realizado con el propósito de mejorar la eficiencia energética de 4 distintas piscinas existentes en la ciudad de Murcia. Tras una primera fase de análisis de las instalaciones, donde se evaluó el estado global de la eficiencia de las piscinas, se implementó y modeló cada piscina en el software TRANSOL 3.1, con el fin de obtener los resultados energéticos. El estudio permitió valorar las soluciones más adecuadas, en función del tipo de edificación, de la demanda energética, de la zona climática en el que se ubican los edificios y de las instalaciones ya presentes, disminuyendo los costes económicos y las emisiones de CO2. Los sistemas alternativos que se emplearon fueron de recursos renovables (instalación solar térmica, instalación caldera de biomasa) u otros (cambio combustible de la caldera, uso de manta térmica, etc.). Finalmente se estudió la viabilidad económica de cada alternativa y de la combinación de alternativas, presentando un abanico de posibilidades técnicas de instalaciones energéticamente y económicamente viable