Retinal photoisomerization versus counterion protonation in light and dark-adapted bacteriorhodopsin and its primary photoproduct

Discovered over 50 years ago, bacteriorhodopsin is the first recognized and most widely studied microbial retinal protein. Serving as a light-activated proton pump, it represents the archetypal ion-pumping system. Here we compare the photochemical dynamics of bacteriorhodopsin light and dark-adapted forms with that of the first metastable photocycle intermediate known as “K”. We observe that following thermal double isomerization of retinal in the dark from bio-active all-trans 15-anti to 13-cis, 15-syn, photochemistry proceeds even faster than the ~0.5 ps decay of the former, exhibiting ballistic wave packet curve crossing to the ground state. In contrast, photoexcitation of K containing a 13-cis, 15-anti chromophore leads to markedly multi-exponential excited state decay including much slower stages. QM/MM calculations, aimed to interpret these results, highlight the crucial role of protonation, showing that the classic quadrupole counterion model poorly reproduces spectral data and dynamics. Single protonation of ASP212 rectifies discrepancies and predicts triple ground state structural heterogeneity aligning with experimental observations. These findings prompt a reevaluation of counter ion protonation in bacteriorhodopsin and contribute to the broader understanding of its photochemical dynamics

Spectroscopic fingerprints of DNA/RNA pyrimidine nucleobases in third-order nonlinear electronic spectra

Accurate ab initio modeling of spectroscopic signals in nonlinear electronic spectra, such as bidimensional (2D) spectra, requires the computation of the electronic transitions induced by the incoming pump/probe pulses, resulting in a challenging calculation of many electronic excited states. A protocol is thus required to evaluate the variations of spectral properties, like transition energies and dipole moments, with the computational level, and to estimate the sensitivity of the spectra to these variations. Such a protocol is presented here within the framework of complete and restricted active space self-consistent field (CASSCF/RASSCF) theory and its second-order perturbation theory extensions (CASPT2/RASPT2). The electronic excited-state manifolds of pyrimidine nucleobases (thymine, uracil, and cytosine) are carefully characterized in vacuo employing high-level RAS(0,0|10,8|2,12)//SS-RASPT2 calculations. The results provide a reference data set that can be used for optimizing computational efforts and costs, as required for studying computationally more demanding multichromophoric systems (e.g., di- and oligonucleotides). The spectroscopic signatures of the 2D electronic spectrum of a perfectly stacked uracil–cytosine dimer model are characterized, and experimental setups are proposed that can resolve non-covalent interchromophoric interactions in canonical pyrimidine nucleobase-stacked dimers

Integrated receivers with bottom subcooling for automotive air conditioning: detailed experimental study of their filling capacity

The use of the integrated receiver in condensers for common automotive air conditioning - A/C - systems is widespread, because of its thermodynamic and operational advantages. Many studies have been already conducted on estimating the effect of the subcooling value. However, this study aims at determining the most important factors affecting the length of the refrigerant stable operating plateau and how the receiver filling is affected by geometrical and thermodynamic boundary conditions, by means of an experimental campaign built using design of experiments - DOE - techniques. Results demonstrate how the receiver diameter and the axle spacing between its inlet and outlet holes have the highest influence on the receiver operation. Finally, these results have been used to set up a numerical model able to accurately estimate the filling efficiency of the integrated receiver, in terms of volume of the operating plateau compared to the net available receiver volume

Simulating Plasmon Resonances of Gold Nanoparticles with Bipyramidal Shapes by Boundary Element Methods

Computational modeling and accurate simulations of localized surface plasmon resonance (LSPR) absorption properties are reported for gold nanobipyramids (GNBs), a class of metal nanoparticle that features highly tunable, geometry-dependent optical properties. GNB bicone models with spherical tips performed best in reproducing experimental LSPR spectra while the comparison with other geometrical models provided a fundamental understanding of base shapes and tip effects on the optical properties of GNBs. Our results demonstrated the importance of averaging all geometrical parameters determined from transmission electron microscopy images to build representative models of GNBs. By assessing the performances of LSPR absorption spectra simulations based on a quasi-static approximation, we provided an applicability range of this approach as a function of the nanoparticle size, paving the way to the theoretical study of the coupling between molecular electron densities and metal nanoparticles in GNB-based nanohybrid systems, with potential applications in the design of nanomaterials for bioimaging, optics and photocatalysis

Impact Forecasting to Support Emergency Management of Natural Hazards

Forecasting and early warning systems are important investments to protect lives, properties, and livelihood. While early warning systems are frequently used to predict the magnitude, location, and timing of potentially damaging events, these systems rarely provide impact estimates, such as the expected amount and distribution of physical damage, human consequences, disruption of services, or financial loss. Complementing early warning systems with impact forecasts has a twofold advantage: It would provide decision makers with richer information to take informed decisions about emergency measures and focus the attention of different disciplines on a common target. This would allow capitalizing on synergies between different disciplines and boosting the development of multihazard early warning systems. This review discusses the state of the art in impact forecasting for a wide range of natural hazards. We outline the added value of impact-based warnings compared to hazard forecasting for the emergency phase, indicate challenges and pitfalls, and synthesize the review results across hazard types most relevant for Europe

The propagation and seismicity of dyke injection, new experimental evidence

To reach the surface, dykes must overcome the inherent tensile strength of the country rock. As they do, they generate swarms of seismic signals, frequently used for forecasting. In this study we pressurize and inject molten acrylic into an encapsulating host rocks of (1) Etna basalt and (2) Comiso limestone, at 30 MPa of confining pressure. Fracture was achieved at 12 MPa for Etna basalt and 7.2 MPa for Comiso limestone. The generation of radial fractures was accompanied by acoustic emissions (AE) at a dominant frequency of 600 kHz. During “magma” movement in the dykes, AE events of approximately 150 kHz dominant frequency were recorded. We interpret our data using AE location and dominant frequency analysis, concluding that the seismicity associated with magma transport in dykes peaks during initial dyke creation but remains significant as long as magma movement continues. These results have important implications for seismic monitoring of active volcanoes