DNA/RNA: Building Blocks of Life Under UV Irradiation

International audienceDuring the last 10 years, intense experimental and theoretical work has proven the existence of ultrafast nonradiative decay routes for UV-excited monomeric nucleic acid bases, accounting for their high photostability. This mechanism has been explained by the occurrence of easily accessible conical intersections connecting the first excited ππ* state with the ground state. However, recent studies of substituent and solvent effects indicate that the situation is more complicated than what was initially thought, notably by the presence of dark excited states. Moreover, the actual shape of the excited-state potential energy surface may induce nonexponential dynamics. Further efforts are needed in order to clarify how various environmental factors affect the structural and dynamical aspects of the nucleic acid base excited states

Femtosecond fluorescence studies of DNA/RNA constituents

International audienceIn this overview, femtosecond fluorescence studies of various DNA constituents are presented, ranging from the monomeric chromophores to different model helices. In order to interpret the experimental results in terms of fundamental processes on the molecular scale they are discussed in the light of recent theoretical calculations. The ultrafast fluorescence decay observed for the monomers is explained by the involvement of highly efficient conical intersections (CI) between the first singlet excited state and the ground state. For the model helices, the picture is more complex, but fluorescence anisotropy data reveal collective effects

Assessing solvent effects on the singlet excited state lifetime of uracil derivatives: a femtosecond fluorescence upconversion study in alcohols and D2O

The excited state lifetimes of uracil, thymine and 5-fluorouracil have been measured using femtosecond UV fluorescence upconversion in various protic and aprotic polar solvents. The fastest decays are observed in acetonitrile and the slowest in aqueous solution while those observed in alcohols are intermediate. No direct correlation with macroscopic solvent parameters such as polarity or viscosity is found, but hydrogen bonding is one key factor affecting the fluorescence decay. It is proposed that the solvent modulates the relative energy of two close-lying electronically excited states, the bright ΠΠ and the dark nΠ states. This relative energy gap controls the non-radiative relaxation of the ΠΠ state through a conical intersection close to the Frank-Condon region competing with the ultrafast internal conversion to the ground state. In addition, an inverse isotope effect is observed in D2O where the decays are faster than in H2O

Singlet excited state dynamics of uracil and thymine derivatives: A femtosecond fluorescence upconversion study in acetonitrile

The excited state properties of uracil, thymine and four analogous uracil compounds have been studied in acetonitrile by steady-state and time-resolved spectroscopy. The excited state lifetimes were measured using femtosecond UV fluorescence upconversion. The excited state lifetimes of uracil and its 1- and 3-methyl substituted derivatives are well described by one ultrafast (6100 fs) component. Five substituted compounds show a more complex behavior, exhibiting longer excited state lifetimes and bi-exponential fluorescence decays. These longer decays are substantially faster in acetonitrile than in aqueous solution showing that the excited state deactivation mechanism is in part governed by the solvent

A Fuzzy Inference System for the Assessment of Indoor Air Quality in an Operating Room to Prevent Surgical Site Infection

Indoor air quality in hospital operating rooms is of great concern for the prevention of surgical site infections (SSI). A wide range of relevant medical and engineering literature has shown that the reduction in air contamination can be achieved by introducing a more efficient set of controls of HVAC systems and exploiting alarms and monitoring systems that allow having a clear report of the internal air status level. In this paper, an operating room air quality monitoring system based on a fuzzy decision support system has been proposed in order to help hospital staff responsible to guarantee a safe environment. The goal of the work is to reduce the airborne contamination in order to optimize the surgical environment, thus preventing the occurrence of SSI and reducing the related mortality rate. The advantage of FIS is that the evaluation of the air quality is based on easy-to-find input data established on the best combination of parameters and level of alert. Compared to other literature works, the proposed approach based on the FIS has been designed to take into account also the movement of clinicians in the operating room in order to monitor unauthorized paths. The test of the proposed strategy has been executed by exploiting data collected by ad-hoc sensors placed inside a real operating block during the experimental activities of the “Bacterial Infections Post Surgery” Project (BIPS). Results show that the system is capable to return risk values with extreme precision

Regression Models to Study the Total LOS Related to Valvuloplasty

Background: Valvular heart diseases are diseases that affect the valves by altering the normal circulation of blood within the heart. In recent years, the use of valvuloplasty has become recurrent due to the increase in calcific valve disease, which usually occurs in the elderly, and mitral valve regurgitation. For this reason, it is critical to be able to best manage the patient undergoing this surgery. To accomplish this, the length of stay (LOS) is used as a quality indicator. Methods: A multiple linear regression model and four other regression algorithms were used to study the total LOS function of a set of independent variables related to the clinical and demographic characteristics of patients. The study was conducted at the University Hospital “San Giovanni di Dio e Ruggi d’Aragona” of Salerno (Italy) in the years 2010–2020. Results: Overall, the MLR model proved to be the best, with an R2 value of 0.720. Among the independent variables, age, pre-operative LOS, congestive heart failure, and peripheral vascular disease were those that mainly influenced the output value. Conclusions: LOS proves, once again, to be a strategic indicator for hospital resource management, and simple linear regression models have shown excellent results to analyze it

Optical Properties of Guanine Nanowires: Experimental and Theoretical Study

International audienceLong nanowires formed by ca. 800 guanine tetrads (G4-wires) are studied in phosphate buffer containing sodium cations. Their room temperature optical properties are compared to those of the monomeric chromophore 2-deoxyguanine monophosphate (dGMP). When going from dGMP to G4-wires, both the absorption and the fluorescence spectra change. Moreover, the fluorescence quantum yield increases by a factor of 7.3 whereas the average fluorescence lifetime increases by more than 2 orders of magnitude, indicating emission associated with weakly allowed transitions. The behavior of G4-wires is interpreted in the light of a theoretical study performed in the frame of the exciton theory combining data from molecular dynamics and quantum chemistry. These calculations, carried out for a quadruplex composed of three tetrads, reveal the existence of various exciton states having different energies and oscillator strengths. The degree of delocalization of the quadruplex Franck−Condon excited states is larger than those found for longer duplexes following the same methodology. The slower excited-state relaxation in G4-wires compared to dGMP is explained by emission from exciton states, possibly limited on individual tetrads, whose coherence is reserved by the reduced mobility of guanines due to multiple Hoogsteen hydrogen bonds

Postoperative Management of Zygomatic Arch Fractures: In-House Rapid Prototyping System for the Manufacture of Protective Facial Shields

Zygomatic fractures account for 10% to 15% of all facial fractures. The surgical management of isolated zygomatic arch fractures usually requires open reduction treatment without fixation through an intraoral access. Therefore, the main problem in the non-fixed treatment of zygomatic arch fractures is related to the difficulty in obtaining a stable reduction for a period long enough to guarantee the physiological bone healing process. We propose an innovative "in-house" rapid prototyping (RP) protocol for the 3D-zygoma mask manufacture of a patient-specific protective device to apply after zygomatic arch fracture reduction. Our study includes 16 consecutive patients who underwent surgical open reduction for an isolated zygoma fracture without fixation between January 2017 and February 2018. The patients received regular postoperative checks at weeks 1 and 2. Before the device was removed, a multiple choice questionnaire was administered to measure the degree of wearability of the mask. The estimated cost of the production is around &OV0556;5 per case and the construction time is around 90 minutes. Based on the encouraging results, obtained in our experience, we hope that other studies can be conducted to confirm our procedure and improve its functionality in the field of facial trauma

Peptide Bond Distortions from Planarity: New Insights from Quantum Mechanical Calculations and Peptide/Protein Crystal Structures

By combining quantum-mechanical analysis and statistical survey of peptide/protein structure databases we here report a thorough investigation of the conformational dependence of the geometry of peptide bond, the basic element of protein structures. Different peptide model systems have been studied by an integrated quantum mechanical approach, employing DFT, MP2 and CCSD(T) calculations, both in aqueous solution and in the gas phase. Also in absence of inter-residue interactions, small distortions from the planarity are more a rule than an exception, and they are mainly determined by the backbone ψ dihedral angle. These indications are fully corroborated by a statistical survey of accurate protein/peptide structures. Orbital analysis shows that orbital interactions between the σ system of Cα substituents and the π system of the amide bond are crucial for the modulation of peptide bond distortions. Our study thus indicates that, although long-range inter-molecular interactions can obviously affect the peptide planarity, their influence is statistically averaged. Therefore, the variability of peptide bond geometry in proteins is remarkably reproduced by extremely simplified systems since local factors are the main driving force of these observed trends. The implications of the present findings for protein structure determination, validation and prediction are also discussed