Ultrafast photochemistry and electron-diffraction spectra in n → (3s) Rydberg excited cyclobutanone resolved at the multireference perturbative level.

We study the ultrafast time evolution of cyclobutanone excited to the singlet n → Rydberg state through non-adiabatic surface-hopping simulationsperformed at extended multi-state complete active space second-order perturbation (XMS-CASPT2) level of theory. These dynamics predict relaxation to the ground-state with a timescale of 822 ± 45 fs with minimal involvement of the triplets. The major relaxation path to the ground-state involves a three-state degeneracy region and leads to a variety of fragmented photoproducts. We simulate the resulting time-resolved electron-diffraction spectra, which track the relaxation of the excited state and the formation of various photoproducts in the ground state.

Electron and ion spectroscopy of azobenzene in the valence and core shells.

Azobenzene is a prototype and a building block of a class of molecules of extreme technological interest as molecular photo-switches. We present a joint experimental and theoretical study of its response to irradiation with light across the UV to x-ray spectrum. The study of valence and inner shell photo-ionization and excitation processes combined with measurement of valence photoelectron-photoion coincidence and mass spectra across the core thresholds provides a detailed insight into the site- and state-selected photo-induced processes. Photo-ionization and excitation measurements are interpreted via the multi-configurational restricted active space self-consistent field method corrected by second order perturbation theory. Using static modeling, we demonstrate that the carbon and nitrogen K edges of azobenzene are suitable candidates for exploring its photoinduced dynamics thanks to the transient signals appearing in background-free regions of the NEXAFS and XPS.

Converging many-body correlation energies by means of sequence extrapolation.

We present an extrapolation scheme for the correlation energy in many-body theory that requires only a relatively small fraction of the orbitals spanning the virtual space but recovers nearly the whole dynamic correlation energy, independently of the single- or multi-reference nature of the problem. Applications to both ground-state chemistry and photochemistry are discussed that clearly show how such an extrapolation scheme can be used to overcome the scaling walls in ab initio quantum chemistry arising from the sheer number of molecular orbitals needed for very accurate calculations.

Photophysics of Deoxycytidine and 5-Methyldeoxycytidine in Solution: A Comprehensive Picture by Quantum Mechanical Calculations and Femtosecond Fluorescence Spectroscopy.

The study concerns the relaxation of electronic excited states of the DNA nucleoside deoxycytidine (dCyd) and its methylated analogue 5-methyldeoxycytidine (5mdCyd), known to be involved in the formation of UV-induced lesions of the genetic code. Due to the existence of four closely lying and potentially coupled excited states, the deactivation pathways in these systems are particularly complex and have not been assessed so far. Here, we provide a complete mechanistic picture of the excited state relaxation of dCyd/5mdCyd in three solvents-water, acetonitrile, and tetrahydrofuran-by combining femtosecond fluorescence experiments, addressing the effect of solvent proticity on the relaxation dynamics of dCyd and 5mdCyd for the first time, and two complementary quantum mechanical approaches (CASPT2/MM and PCM/TD-CAM-B3LYP). The lowest energy ππ* state is responsible for the sub-picosecond lifetime observed for dCyd in all the solvents. In addition, computed excited state absorption and transient IR spectra allow one, for the first time, to assign the tens of picoseconds time constant, reported previously, to a dark state (nOπ*) involving the carbonyl lone pair. A second low-lying dark state, involving the nitrogen lone pair (nNπ*), does significantly participate in the excited state dynamics. The 267 nm excitation of dCyd leads to a non-negligible population of the second bright ππ* state, which affects the dynamics, acting mainly as a "doorway" state for the nOπ* state. The solvent plays a key role governing the interplay between the different excited states; unexpectedly, water favors population of the dark states. In the case of 5mdCyd, an energy barrier present on the main nonradiative decay route explains the 6-fold lengthening of the excited state lifetime compared to that of dCyd, observed for all the examined solvents. Moreover, C5-methylation destabilizes both nOπ* and nNπ* dark states, thus preventing them from being populated.

Computing the Absorption and Emission Spectra of 5-Methylcytidine in Different Solvents: A Test-Case for Different Solvation Models.

The optical spectra of 5-methylcytidine in three different solvents (tetrahydrofuran, acetonitrile, and water) is measured, showing that both the absorption and the emission maximum in water are significantly blue-shifted (0.08 eV). The absorption spectra are simulated based on CAM-B3LYP/TD-DFT calculations but including solvent effects with three different approaches: (i) a hybrid implicit/explicit full quantum mechanical approach, (ii) a mixed QM/MM static approach, and (iii) a QM/MM method exploiting the structures issuing from molecular dynamics classical simulations. Ab-initio Molecular dynamics simulations based on CAM-B3LYP functionals have also been performed. The adopted approaches all reproduce the main features of the experimental spectra, giving insights on the chemical-physical effects responsible for the solvent shifts in the spectra of 5-methylcytidine and providing the basis for discussing advantages and limitations of the adopted solvation models.

Tracking the primary photoconversion events in rhodopsins by ultrafast optical spectroscopy.

Opsins are a broad class of photoactive proteins, found in all classes of living beings from bacteria to higher animals, which work either as light-driven ion pumps or as visual pigments. The photoactive function in opsins is triggered by the ultrafast isomerization of the retinal chromophore around a specific carbon double bond, leading to a highly distorted, spectrally red-shifted photoproduct. Understanding, by either experimental or computational methods, the time course of this photoisomerization process is of utmost importance, both for its biological significance and because opsin proteins are the blueprint for molecular photoswitches. This paper focuses on the ultrafast 11-cis to all-trans isomerization in visual rhodopsins, and has a twofold goal: (i) to review the most recent experimental and computational efforts aimed at exposing the very early phases of photoconversion; and (ii) discuss future advanced experiments and calculations that will allow an even deeper understanding of the process. We present high time resolution pump-probe data, enabling us to follow the wavepacket motion through the conical intersection connecting excited and ground states, as well as femtosecond stimulated Raman scattering data allowing us to track the subsequent structural evolution until the first stable all-trans photoproduct is reached. We conclude by introducing computational results for two-dimensional electronic spectroscopy, which has the potential to provide even greater detail on the evolution of the electronic structure of retinal during the photoisomerization process.

Modelling vibrational coherence in the primary rhodopsin photoproduct.

Molecular dynamics simulations of the rhodopsin photoreaction reveal coherent low frequency oscillations in the primary photoproduct (photorhodopsin), with frequencies slightly higher than observed in the experiment. The coherent molecular motions in the batho-precursor can be attributed to the activation of ground state vibrational modes in the hot photo-product, involving out-of-plane deformations of the carbon skeleton. Results are discussed and compared with respect to spectroscopic data and suggested reaction mechanisms.

A global investigation of excited state surfaces within time-dependent density-functional response theory.

This work investigates the capability of time-dependent density functional response theory to describe excited state potential energy surfaces of conjugated organic molecules. Applications to linear polyenes, aromatic systems, and the protonated Schiff base of retinal demonstrate the scope of currently used exchange-correlation functionals as local, adiabatic approximations to time-dependent Kohn-Sham theory. The results are compared to experimental and ab initio data of various kinds to attain a critical analysis of common problems concerning charge transfer and long range (nondynamic) correlation effects. This analysis goes beyond a local investigation of electronic properties and incorporates a global view of the excited state potential energy surfaces.

Computational evidence in favor of a two-state, two-mode model of the retinal chromophore photoisomerization.

In this paper we use ab initio multiconfigurational second-order perturbation theory to establish the intrinsic photoisomerization path model of retinal chromophores. This is accomplished by computing the ground state (S(0)) and the first two singlet excited-state (S(1), S(2)) energies along the rigorously determined photoisomerization coordinate of the rhodopsin chromophore model 4-cis-gamma-methylnona-2,4,6,8-tetraeniminium cation and the bacteriorhodopsin chromophore model all-trans-hepta-2,4, 6-trieniminium cation in isolated conditions. The computed S(2) and S(1) energy profiles do not show any avoided crossing feature along the S(1) reaction path and maintain an energy gap >20 kcal small middle dotmol(-1). In addition, the analysis of the charge distribution shows that there is no qualitative change in the S(2) and S(1) electronic structure along the path. Thus, the S(1) state maintains a prevalent ionic (hole-pair) character whereas the S(2) state maintains a covalent (dot-dot) character. These results, together with the analysis of the S(1) reaction coordinate, support a two-state, two-mode model of the photoisomerization that constitutes a substantial revision of the previously proposed models.

[Anaerobic bacteria in oral infections of dental origin. The characteristics of Bacteroides species and diagnosis]. / Batteri anaerobi nelle infezioni orali di origine dentale. Caratteristiche di specie e diagnosi per i bacteroides.

Pyogenic orofacial infections are generally the result of a mixed aerobic and anaerobic infection. The aerobic germ, particularly the Bacteroides, have a prevailing role, even though their etiopathogenetic role is not clear yet.

[The clinical and therapeutic aspects of epulis gravidarum]. / Aspetti clinici e terapeutici dell'epulide gravidica.

Preventive oral hygiene performed with particular care is the only possible means of preventing the occurrence and the recurrence of phlogistic phenomena of the stomatologic apparatus of pregnant women. However in the case of epulis surgical treatment of the lesion completes preventive care, followed by a plan of postpartum hygiene to eliminate local causes and to prevent recurrences together with therapy for the elimination of periodontal pockets and infrabony pockets, to a restitution ad integrum of the general conditions of the oral cavity.

[Dental treatment during pregnancy]. / Il trattamento odontoiatrico durante la gravidanza.

Applying the basics of preventive dentistry at the primary level will broaden the scope of prenatal care. Dentists should encourage all patients of childbearing age to seek oral health counseling and examination as soon as they learn they are pregnant. Specific printed information on oral hygiene, plaque control, nutrition and tooth development should be available for pregnant patients. Emergency problem should be alleviated immediately. Indicated medications should not be with held because of pregnancy but patients must be informed of benefits and risks. Consultation with the patient's physician is always appropriate.

[The interaction between antibiotic therapy and contraceptive drugs]. / Interazione tra terapia antibiotica e farmaci anticoncezionali.

Although the interaction between antibiotics prescribed by the dentist and the estroprogestinics has been Known for some time, to reduce the effects of oral contraception, the dentist tends to underestimate this possible possible complication. In this review the antibiotics taken into consideration and their mechanism of interaction with the oral contraceptives are discussed. The dentist's approach towards a patient in fertile age is suggested. In conclusion the use of oral estroprogestinics as a contraceptive method is affirmed to be not an obstacle to the administration of antibiotics, but a thorough anamnesis and a cautious prescription, together with informing the patient of the risks is necessary.

[Gingivitis in pregnancy. The clinical manifestations, pathogenesis and treatment]. / Gengiviti gravidiche. Manifestazioni cliniche, patogenesi e trattamento.

During pregnancy, manifestations of different nature can occur on the oral mucosa ranging from extended edema to haemorrhagic stomatitis. Alterations are more evident when poor dental care and hygiene are present. An important role in this gingival attentions is attributed to an increase in the estrogenic concentration originating from placentae and progesteron. The problem must be dealt with suitable preventive care.

[The microbiological aspects of dental caries: the evaluation of a protocol for isolating Streptococcus mutans]. / Aspetti microbiologici della carie dentaria: valutazione di un protocollo di isolamento dello Streptococcus mutans.

The role of Streptococcus mutans in the etiopathogenesis of dental caries to set up a protocol for the culture and the identification of the bacterium, in order to obtain the isolation in an heterogeneous age, sex and stomatognathic population is described. A selected culture medium for mutans, Mitis Salivarius agar enriched with Bacitracin (MSB-agar), has been used as well as biochemical method based on carbohydrates fermentation by amplified bacterial flora for the identification of the bacterial genus.

[The prevention of bacterial endocarditis]. / Profilassi delle endocarditi batteriche.

The paper examines the prevention of bacterial endocarditis in risk patients undergoing outpatient treatment. The hypothesis of possible bacteremia provoked by either diagnostic or therapeutic surgery should be carefully assessed. For this purpose antibiotic prophylaxis should be commenced, using different methods and doses according to the type of patient, in association with hygienic and behavioural norms which the specialist will recommend and monitor.

[The nephropathic patient in ambulatory surgical practice]. / Il paziente nefropatico nella pratica chirurgica ambulatoriale.

The aim of this study was to define a correct preoperative approach to be used in patients affected by chronic renal insufficiency in order to neutralise possible risks associated with the pathology in question.