Fulvenallenyl Radical (CH)-Mediated Gas-Phase Synthesis of Bicyclic Aromatic CH Isomers: Can Fulvenallenyl Efficiently React with Closed-Shell Hydrocarbons?

To understand the reactivity of resonantly stabilized radicals, often found in relevant concentrations in gaseous environments, it is important to determine their main reaction pathways. Here, it is investigated whether the fulvenallenyl radical (CH) reacts preferentially with closed-shell molecules or radicals. Electronic structure calculations on the CH potential energy surface accessed by the reactions of CH with methylacetylene (CHCCH) and allene (HCCCH) were combined with RRKM-ME calculations of temperature- and pressure-dependent rate constants using the automated EStokTP software suite and kinetic modeling to assess the reactivity of CH with closed-shell unsaturated hydrocarbons.

Crossed molecular beam experiments and theoretical simulations on the multichannel reaction of toluene with atomic oxygen.

Despite extensive experimental and theoretical studies on the kinetics of the O(P) + CH (toluene) reaction and a pioneering crossed molecular beam (CMB) investigation, the branching fractions (BFs) of the CHCHO(methylphenoxy) + H, CHO(phenoxy) + CH, and spin-forbidden CHCH (methylcyclopentadiene) + CO product channels remain an open question, which has hampered the proper inclusion of this important reaction in the chemical modelling of various chemical environments. We report a CMB study with universal soft electron-ionization mass-spectrometric detection of the reactions O(P,D) + toluene at the collision energy of 34.7 kJ mol.

Toward an Accurate Black-Box Tool for the Kinetics of Gas-Phase Reactions Involving Barrier-less Elementary Steps.

An enhanced computational protocol has been devised for the accurate characterization of gas-phase barrier-less reactions in the framework of the reaction-path (RP) and variable reaction coordinate variational transition-state theory. In particular, the synergistic combination of density functional theory and Monte Carlo sampling to optimize reactive fluxes led to a reliable yet effective computational workflow. A black-box strategy has been developed for selecting the most suited density functional with reference to a high-level one-dimensional reference potential.

Kinetics of CN ( = 1) reactions with butadiene isomers at low temperature by cw-cavity ring-down in a pulsed Laval flow with theoretical modelling of rates and entrance channel branching.

We present an experimental and theoretical investigation of the reaction of vibrationally excited CN ( = 1) with isomers of butadiene at low temperature. The experiments were conducted using the newly built apparatus, UF-CRDS, which couples near-infrared cw-cavity ring-down spectroscopy with a pulsed Laval flow. The well-matched hydrodynamic time and long ring-down time decays allow measurement of the kinetics of the reactions within a single trace of a ring-down decay, termed Simultaneous Kinetics and Ring-down (SKaR).

: Intrinsic innervation and dopaminergic markers after experimental denervation in rat thymus.

On behalf of the coauthors and with much regret, I must retract our publication entitled "Intrinsic innervation and dopaminergic markers after experimental denervation in rat thymus" published in European Journal of Histochemistry 2010;54(2):e17 for the following reason: Unfortunately, now, after thirteen years, we have realized that some microphotographs published in the paper have been processed to improve the presentation of the images. The three surviving authors of the paper agree that the processing of the presentation images is against the COPE Ethical Editorial Standard, although the presentation images do not alter the integrity of methodological procedures and the results of the research work, obtained from the direct analysis of slides under microscope and rigorous statistical analysis of data; therefore, we, the authors of the above indicated paper, request the retraction of the publication. We apologize for what happened.

Investigation of Methylcyclopentadiene Reactivity: Abstraction Reactions and Methylcyclopentadienyl Radical Unimolecular Decomposition.

Understanding the reactivities of methylcyclopentadiene and the methylcyclopentadienyl radical is important in order to improve our comprehension of the chemical kinetics leading to the formation, decomposition, and growth of the first aromatic ring, as it has been shown that five-membered-ring species are important intermediates in the reaction kinetics of aromatic species. In this work, the rate constants of some key H-abstraction reactions from methylcyclopentadiene to produce the methylcyclopentadienyl radical and the formation of fulvene and benzene from the latter are theoretically determined. Rate constants are evaluated using the ab initio transition state theory-based master equation approach, determining structures and Hessians of all stationary points at the ωB97X-D/aug-cc-pVTZ level, energies at the CCSD(T) level extrapolated to the complete basis set limit, RRKM rate constants using conventional and variational transition state theory, and phenomenological rate constants through the solution of the one-dimensional master equation.

Intersystem crossing in the entrance channel of the reaction of O(P) with pyridine.

Two quantum effects can enable reactions to take place at energies below the barrier separating reactants from products: tunnelling and intersystem crossing between coupled potential energy surfaces. Here we show that intersystem crossing in the region between the pre-reactive complex and the reaction barrier can control the rate of bimolecular reactions for weakly coupled potential energy surfaces, even in the absence of heavy atoms. For O(P) plus pyridine, a reaction relevant to combustion, astrochemistry and biochemistry, crossed-beam experiments indicate that the dominant products are pyrrole and CO, obtained through a spin-forbidden ring-contraction mechanism.

Crossed-Beam and Theoretical Studies of the O(P, D) + Benzene Reactions: Primary Products, Branching Fractions, and Role of Intersystem Crossing.

Reliable modeling of hydrocarbon oxidation relies critically on knowledge of the branching fractions (BFs) as a function of temperature () and pressure () for the products of the reaction of the hydrocarbon with atomic oxygen in its ground state, O(P). During the past decade, we have performed in-depth investigations of the reactions of O(P) with a variety of small unsaturated hydrocarbons using the crossed molecular beam (CMB) technique with mass spectrometric (MS) detection and time-of-flight (TOF) analysis, combined with synergistic theoretical calculations of the relevant potential energy surfaces (PESs) and statistical computations of product BFs, including intersystem crossing (ISC). This has allowed us to determine the primary products, their BFs, and extent of ISC to ultimately provide theoretical channel-specific rate constants as a function of and .

Theoretical Study of the Extent of Intersystem Crossing in the O(P) + CH Reaction with Experimental Validation.

The extent of intersystem crossing in the O(P) + CH reaction, a prototypical system for spin-forbidden reactions in oxygenated aromatic molecules, is theoretically evaluated for the first time. Calculations are performed using nonadiabatic transition-state theory coupled with stochastic master equation simulations and Landau-Zener theory. It is found that the dominant intersystem crossing pathways connect the T2 and S0 potential energy surfaces through at least two distinct minimum-energy crossing points.

Electronic structure-based rate rules for addition-elimination reactions on mono-aromatic hydrocarbons with single and double OH/CH/OCH/CHO/CH substituents: a systematic theoretical investigation.

The recent interest in bio-oils combustion and the key role of mono-aromatic hydrocarbons (MAHs) in existing kinetic frameworks, both in terms of poly-aromatic hydrocarbons growth and surrogate fuels formulation, motivates the current systematic theoretical investigation of one of the relevant reaction classes in MAHs pyrolysis and oxidation: ipso substitution by hydrogen. State-of-the-art theoretical methods and protocols implemented in automatized computational routines allowed to investigate 14 different potential energy surfaces involving MAHs with hydroxy and methyl single (phenol and toluene) and double (o-,m-,p-C6H4(OH)2, o-,m-,p-CH3C6H4OH, and o-,m-,p-C6H4(CH3)2) substituents, providing rate constants for direct implementation in existing kinetic models. The accuracy of the adopted theoretical method was validated by comparison of the computed rate constants with the available literature data.

State-of-the-Art Quantum Chemistry Meets Variable Reaction Coordinate Transition State Theory to Solve the Puzzling Case of the HS + Cl System.

The atmospheric reaction of HS with Cl has been reinvestigated to check if, as previously suggested, only explicit dynamical computations can lead to an accurate evaluation of the reaction rate because of strong recrossing effects and the breakdown of the variational extension of transition state theory. For this reason, the corresponding potential energy surface has been thoroughly investigated, thus leading to an accurate characterization of all stationary points, whose energetics has been computed at the state of the art. To this end, coupled-cluster theory including up to quadruple excitations has been employed, together with the extrapolation to the complete basis set limit and also incorporating core-valence correlation, spin-orbit, and scalar relativistic effects as well as diagonal Born-Oppenheimer corrections.

Combined Experimental and Theoretical Studies of the O(P) + 1-Butene Reaction Dynamics: Primary Products, Branching Fractions, and Role of Intersystem Crossing.

Information on the detailed mechanism and dynamics (primary products, branching fractions (BFs), and channel specific rate constants as a function of temperature) for many important combustion reactions of O(P) with unsaturated hydrocarbons is still lacking. We report synergistic experimental/theoretical studies on the mechanism and dynamics of the O(P) + 1-CH (1-butene) reaction by combining crossed molecular beam (CMB) experiments with soft electron ionization mass-spectrometric detection and time-of-flight analysis at 10.5 kcal/mol collision energy () to high-level electronic structure calculations of the underlying triplet and singlet potential energy surfaces (PESs) and statistical Rice-Ramsperger-Kassel-Marcus/Master Equation (RRKM/ME) computations of BFs including intersystem crossing (ISC).

Molecular Modeling of the Interaction of Protein L with Antibodies.

Protein L (PpL) is a bacterial protein which is used in the affinity chromatography stage of the production of monoclonal antibodies because of its ability to form high affinity complexes with the light chains of immunoglobulins. In the present work, the binding interfaces between one domain of PpL and antigen-binding fragments (Fab) have been investigated adopting molecular dynamics with the aim of determining the binding contribution of the residues located at the Fab-PpL interface. Because it is known that PpL binds antibodies through two distinct binding sites with different affinities, simulations were performed for both sites to determine interaction free energies to assess the relative binding contribution of the two sites.

Molecular insight into protein binding orientations and interaction modes on hydrophobic charge-induction resin.

Hydrophobic charge-induction chromatography (HCIC) with 4-mercaptoethyl-pyridine (MEP) as the functional ligand has been developed as a new technology for antibody purification. In the present work, molecular simulation methods were developed to investigate the interactions between the Fc fragment of IgG and a MEP ligand net. The MM/PBSA method was used to evaluate the binding energy for the MEP ligand net at different densities.

Exploring short intramolecular interactions in alkylaromatic substrates.

From proteins and peptides to semiconducting polymers, aliphatic chains on aromatic groups are recurring motifs in macromolecules from very diverse application fields. Fields in which molecular folding and packing determine the macroscopic physical properties that make such advanced materials appealing in the first place. Within each macromolecule, the intrinsic structure of each unit defines how it interacts with its neighbours, ultimately opening up or denying certain backbone conformations.

A Qualitative and Quantitative Study of the Innervation of the Human Non Pregnant Uterus.

Human female reproductive system is closely dependent by hormonal stimulation. Anyway it is now commonly stated that autonomic innervation system regulates, along with hormonal stimulation, the uterine physiology. Cholinergic and adrenergic innervations have a critical role in mediating input to the uterus, but other neurotransmitters and neuropeptides exist that influence uterine physiology, as well.

Reaction Dynamics of O((3)P) + Propyne: I. Primary Products, Branching Ratios, and Role of Intersystem Crossing from Crossed Molecular Beam Experiments.

We performed synergic experimental/theoretical studies on the mechanism of the O((3)P) + propyne reaction by combining crossed molecular beams experiments with mass-spectrometric detection and time-of-flight analysis at 9.2 kcal/mol collision energy (Ec) with ab initio electronic structure calculations at a high level of theory of the relevant triplet and singlet potential energy surfaces (PESs) and statistical calculations of branching ratios (BRs) taking into account intersystem crossing (ISC). In this paper (I) we report the results of the experimental investigation, while the accompanying paper (II) shows results of the theoretical investigation with comparison to experimental results.

Reaction Dynamics of O((3)P) + Propyne: II. Primary Products, Branching Ratios, and Role of Intersystem Crossing from Ab Initio Coupled Triplet/Singlet Potential Energy Surfaces and Statistical Calculations.

The mechanism of the O((3)P) + CH3CCH reaction was investigated using a combined experimental/theoretical approach. Experimentally the reaction dynamics was studied using crossed molecular beams (CMB) with mass-spectrometric detection and time-of-flight analysis at 9.2 kcal/mol collision energy.

Neurotransmitters and Neuropeptides Expression in the Uterine Scar After Cesarean Section.

Peptides and neuropeptides influence the uterine disorders of healing or cicatrization, chronic pelvic pain and disorder of pregnancy, labor and puerperium. They also promote changes in the lower uterine segment (LUS) during pregnancy, labor and delivery. We investigated the tissue quantity of neurotensin (NT), neuropeptide tyrosin (NPY) and Protein Gene Product 9.

Laminin and Collagen IV: Two Polypeptides as Marker of Dystocic Labor.

Collagen IV and Laminin are localized in cells and tissue of numerous human organs including the uterus, where these polypeptides control either age changes, or uterus growth in pregnancy, or ripening and dilatation in labor. Authors examined the polypeptides distribution of collagen IV and Laminin in the human pregnant uterus, in normal and dystocic labor, to clarify their physiologic role, by distribution and/or their changes in prolonged dystocic labor. We collected lower uterine segment (LUS) fragments during cesarean section (CS); these biopsies were treated with basic morphological staining for the observation of microscopic- anatomic details.

Isomer-Specific Chemistry in the Propyne and Allene Reactions with Oxygen Atoms: CH3CH + CO versus CH2CH2 + CO Products.

We report direct experimental and theoretical evidence that, under single-collision conditions, the dominant product channels of the O((3)P) + propyne and O((3)P) + allene isomeric reactions lead in both cases to CO formation, but the coproducts are singlet ethylidene ((1)CH3CH) and singlet ethylene (CH2CH2), respectively. These data, which settle a long-standing issue on whether ethylidene is actually formed in the O((3)P) + propyne reaction, suggest that formation of CO + alkylidene biradicals may be a common mechanism in O((3)P) + alkyne reactions, in contrast to formation of CO + alkene molecular products in the corresponding isomeric O((3)P) + diene reactions, either in combustion or other gaseous environments. These findings are of fundamental relevance and may have implications for improved combustion models.

Human Lymphatic Mesenteric Vessels: Morphology and Possible Function of Aminergic and NPY-ergic Nerve Fibers.

Background: The lymphatic vessels have been studied in different organs from a morphological to a clinical point of view. Nevertheless, the knowledge of the catecholaminergic control of the lymphatic circulation is still incomplete. The aim of this work is to study the presence and distribution of the catecholaminergic and NPY-ergic nerve fibers in the whole wall of the human mesenteric lymphatic vessels in order to obtain knowledge about their morphology and functional significance.

Relevance of the Channel Leading to Formaldehyde + Triplet Ethylidene in the O((3)P) + Propene Reaction under Combustion Conditions.

Comprehension of the detailed mechanism of O((3)P) + unsaturated hydrocarbon reactions is complicated by the existence of many possible channels and intersystem crossing (ISC) between triplet and singlet potential energy surfaces (PESs). We report synergic experimental/theoretical studies of the O((3)P) + propene reaction by combining crossed molecular beams experiments using mass spectrometric detection at 9.3 kcal/mol collision energy (Ec) with high-level ab initio electronic structure calculations of the triplet PES and RRKM/master equation computations of branching ratios (BRs) including ISC.