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Human biology has a preference for left-handed chiral molecules and an outstanding question is if this is imposed through astrophysical origins. We aim to evaluate the known information about chiral molecules within astrophysical and astrochemical databases, evaluate chemical modeling accuracy, and use high-level CCSD(T) calculations to characterize propylene oxide and other oxirane variants. By comparing these computational values with past laboratory experiments, we find a 99.9% similarity. We also have put together a new database dedicated to chiral molecules and variants of chiral molecules to assist in answering this question., Comment: 11 pages, 4 figures, 12 tables, accepted by Astronomy & Computation Journal

A virtual hands-on computer laboratory has been designed within the Gather online meeting platform. Gather's features such as spatial audio, private spaces and interactable objects offer scope for great improvements over currently used platforms, especially for small-group based teaching. We describe our experience using this virtual computer laboratory for a recent 'Python for Beginners' workshop held as part of the Software Sustainability Institute's 2022 Research Software Camp., Comment: 10 pages, 3 figures

The COVID-19 pandemic disrupted chemistry teaching practices globally as many courses were forced online, necessitating adaptation to the digital platform. The biggest impact was to the practical component of the chemistry curriculum-the so-called wet lab. Naively, it would be thought that computer-based teaching laboratories would have little problem in making the move. However, this is not the case as there are many unrecognized differences between delivering computer-based teaching in-person and virtually: software issues, technology, and classroom management. Consequently, relatively few “hands-on” computational chemistry teaching laboratories are delivered online. In this paper, we describe these issues in more detail and how they can be addressed, drawing on our experience in delivering a thirdyear computational chemistry course as well as remote hands-on workshops for the Virtual Winter School on Computational Chemistry and the European BIG-MAP project.

NMR is a powerful tool for obtaining information on the structural characterization and dynamics of proteins, and nucleic acids, and their complexes. The complexity of the spectra is such that elucidation through computational simulation is a much desired thing. However, the size of most structures of interest is such that they remain out of reach of accurate quantum chemical techniques. Fragmentation methods have been shown to be a viable means of reducing the cost of ab initio calculations to enable the prediction of molecular properties of large systems to chemical accuracy. We look at the systematic molecular fragmentation by annihilation method for a model peptide system and show that this procedure reproduces the shielding constants of a full calculation at only a fraction of the cost. Discussion of the considerations needed in applying this method is discussed and comparison made with the results of the similar fragment molecular orbital and ONIOM methods.

Isomerism is a fundamental chemical concept, reflecting the fact that the arrangement of atoms in a molecular entity has a profound influence on its chemical and physical properties. Here we describe a previously unclassified fundamental form of conformational isomerism through four resolved stereoisomers of a transoid (BF)O(BF)-quinoxalinoporphyrin. These comprise two pairs of enantiomers that manifest structural relationships not describable within existing IUPAC nomenclature and terminology. They undergo thermal diastereomeric interconversion over a barrier of 104 ± 2 kJ mol−1, which we term ‘akamptisomerization’. Feasible interconversion processes between conceivable synthesis products and reaction intermediates were mapped out by density functional theory calculations, identifying bond-angle inversion (BAI) at a singly bonded atom as the reaction mechanism. We also introduce the necessary BAI stereodescriptors parvo and amplo. Based on an extended polytope formalism of molecular structure and stereoisomerization, BAI-driven akamptisomerization is shown to be the final fundamental type of conformational isomerization.

The coordination of bases to chlorophyll magnesium modifies spectroscopic properties in solution as well as in situ in reaction centres. We evaluate the free energies of complexation of one or two pyridine, 1-propanol, diethyl ether or water solvent molecules at 298 and 150 K to rationalise observed phenomena. Various a priori dispersion-corrected density functional theory calculations are performed as well as second-order Møller–Plesset calculations, focusing on the effects of dispersion modifying the intermolecular interactions, of dispersion modifying solvation energies, of entropy, and of basis-set superposition error. A process of particular interest is magnesium complexation in ether at low temperature that is often exploited to assign the Q-band visible absorption spectrum of chlorophyll. Recently, we demonstrated that trace water interferes with this process, but the nature of the resulting complex could not be uniquely determined; here, it is identified as ether.Chlorophyll-a.H2O, consistent with interpretations based on our authoritative 2013 assignment.

The structures and energies of a set of spiropyrans and merocyanines – BIPS [1 ,3 ,3 -trimethylspiro[2H-1-benzopyran-2,2 - indoline], 6-nitroBIPS, and 6,8-dinitroBIPS – are calculated using density functional theory and second-order Møller–Plesset methods. The relative energies of all possible merocyanine isomers in the ground state are determined systematically at a uniform level of theory. Solvent contributions, which have been found to be significant, are also included. Ke

Dalton is a powerful general-purpose program system for the study of molecular electronic structure at the Hartree-Fock, Kohn-Sham, multiconfigurational self-consistent-field, MOller-Plesset, configuration-interaction, and coupled-cluster levels of theory. Apart from the total energy, a wide variety of molecular properties may be calculated using these electronic-structure models. Molecular gradients and Hessians are available for geometry optimizations, molecular dynamics, and vibrational studies, whereas magnetic resonance and optical activity can be studied in a gauge-origin-invariant manner. Frequency-dependent molecular properties can be calculated using linear, quadratic, and cubic response theory. A large number of singlet and triplet perturbation operators are available for the study of one-, two-, and three-photon processes. Environmental effects may be included using various dielectric-medium and quantum-mechanics/molecular-mechanics models. Large molecules may be studied using linear-scaling and massively parallel algorithms. Dalton is distributed at no cost from for a number of UNIX platforms., QC 20140516

Simultaneously measured absorption (ABS) and magnetic circular dichroism (MCD) spectra of the Q-bands of chlorophyll-a (Chl-a) in ether over 150-186 K reveal that the species that forms at low temperature is a chlorophyll hydrate rather than a diether complex. We have recently proposed a new assignment paradigm for the spectra of chlorophillides which, for the first time, quantitatively accounts for a wide range of observed data. Observations performed at low temperature in ether have historically been very important for the interpretation of the spectra of Chl-a. While our assignment for this system initially anticipated only small spectral changes as the temperature is lowered, significant changes are known to occur. Extensive CAM-B3LYP time-dependent density-functional theory (TD-DFT) calculations verify that the observed spectra of the hydrated species conforms to expectations based on our new assignment, as well as supporting the feasibility of the proposed hydration reactions.

This paper presents a systematic study of partitioning schemes for locally dense basis sets in the context of NMR shielding calculations. The partitionings explored were based exclusively on connectivity and utilized the basis sets from the pcS-n series.

The interactions of the metal ions Na+, Mg2+, Ca 2+ and Zn2+ with cytosine have been investigated with inclusion of solvent effects. Computations have been performed at the density functional and Møller-Plesset levels of theory within the IEFPCM solvent

We provide a new and definitive spectral assignment for the absorption, emission, high-resolution fluorescence excitation, linear dichroism, and/or magnetic circular dichroism spectra of 32 chlorophyllides in various environments. This encompases all data

The isomerisation of two isomers of merocyanine, is examined using time-dependent density functional theory with modern functionals. Using an implementation of the branch plane updating algorithm of Maeda et al., a conical intersection which connects the

The interaction of the metal ions Na+, Mg2+, Ca2+, and Zn2+ with cytosine have been reinvestigated at the density functional, Møller-Plesset, and coupled cluster levels of theory, including hitherto unstudied tautomeric forms. It has been found that the

Earlier results for the 11-cis to all-trans isomerisation of the retinal chromophore after photoexcitation, studied using time-dependent density functional theory with the hybrid CAM-B3LYP functional, are compared with new results using other long-range corrected DFT functionals. The TDDFT S0 and S1 minimum energy paths have been compared with the approximate coupled-cluster method RI-CC2. All calculations were consistent in producing an additional avoided crossing minimum on the S1 minimum energy path lying approximately halfway between the 11-cis and all-trans S1 minima. In this minimum on the S1 potential energy surface, the retinal chromophore has inverted bond order in its carbon chain and lower energy than it has in both the 11-cis and all-trans S1 minima.

OBJETIVO: Caracterizar o perfil e os diagnósticos de enfermagem do neonato com cardiopatia congênita. MÉTODO: Trata-se de um estudo descritivo, exploratório e retrospectivo. Foram analisados 46 prontuários de neonatos internados no período de novembro de 2000 a dezembro de 2008. RESULTADOS: a maioria era do sexo masculino (61%), com idade média de 15,5dias,as patologias mais prevalentes foram Comunicação interatrial (48%), Persistência do Canal Arterial (33%) e Comunicação interventricular (30%). Os diagnósticos de enfermagem prevalentes foram: risco para diminuição do débito cardíaco (91,3%) e insaturação arterial periférica (80,4%). CONCLUSÃO: conhecer as características do neonato com doença cardíaca congênita favorece a prestação da assistência de enfermagem direcionada pelos diagnósticos de enfermagem.

The isomerization of the 11-cis isomer (PSB11) of the retinal chromophore to its all-trans isomer (PSBT) is examined. Optimized structures on both the ground state and the excited state are calculated, and the dependence on torsional angles in the carbon

Acreditação hospitalar combina segurança com ética profissional, responsabilidade e qualidade do atendimento, melhorando o gerenciamento do serviço, da qualidade da assistência ao paciente. Este estudo descritivo, exploratório, documental, realizado em instituição pública de cardiologia, objetivou identificar dificuldades para certificação de qualidade de nível I, no olhar dos enfermeiros e propor medidas de gerenciamento. A coleta foi realizada, utilizando-se de documentos da acreditação hospitalar. As dificuldades encontradas foram estruturais e operacionais; de organização de processos e gestão de recursos humanos; de evidenciar programa de educação e treinamento continuado institucional e avaliação de efetividade; de interação sistêmica dos componentes, atividades e serviços de apoio técnico à organização; de planejamento, aquisição, armazenamento, rastreabilidade e disponibilização de recursos materiais e a falta de evidencias de documentações atualizadas, disponíveis, aplicadas e sistematizadas. Frente ao diagnóstico, ações estratégicas para resolução do problema e participação do enfermeiro foram desenvolvidas, junto às lideranças e administradores. DOI:https://doi.org/10.15253/2175-6783.2010000400002

We have performed DFT and TD-DFT calculations on Pt(dcbpy)Cl2 (1) and [Pt(ttpy)phenylacetylide]+ (2+) to study the stability of these Pt(II) species upon reduction and photoexcitation; we found that while these compounds are stable upon reduction, photoexcitation of the reduced species leads to dissociation of the ligand set.

The Qy absorption spectrum of Photosystem-I from Thermosynecochoccus elongatus (formerly Synecochoccus elongatus) is calculated using the CAM-B3LYP density functional and INDO schemes based on a quantummechanically refined structure for the entire photosystem obtained using the PW91 density functional. These methods present a priori predictions of the absorption and linear dichroism spectra and include protein electrostatic effects, short range inductive effects, long-range and short-range exciton couplings, and superexchange effects involving aromatic residues and carotenes. CAM-B3LYP is used as it is the only known density functional that correctly describes the Q bands of chlorophylls, all other methods contaminating them with erroneous charge-transfer excitations. A critical feature is found to be the use of fully optimized heavy-atom coordinates, with those obtained from just X-ray crystallography providing a poor description of the electronic properties of the chromophores. The result is a realistic first-principles prediction of the observed absorption band that identifies the nature of the red-shifted chlorophylls as well as the energies of the reactioncenter chlorophylls and the exciton couplings acting between them. The "special pair" appears more like a dimer of dimers than a self-contained functional unit, with the exciton couplings between its members and the accessory chlorophylls exceeding the internal coupling.

Using the long-range corrected (LC) density functional theory (DFT) scheme introduced by Iikura et al. [J. Chem. Phys. 115, 3540 (2001)] and the Coulomb-attenuating model (CAM-B3LYP) of Yanai et al. [Chem. Phys. Lett. 393, 51 (2004)], we have calculated the longitudinal dipole moments and static electronic first hyperpolarizabilities of increasingly long polymehtineimine oligomers. For comparison purposes Hartree-Fock (HF), Moller-Plesset perturbation theory (MP2), and conventional pure and hybrid functionals have been considered as well. HF, generalized gradient approximation (GGA), and conventional hybrids provide too large dipole moments for long oligomers, while LC-DFT allows to reduce the discrepancy with respect to MP2 by a factor of 3. For the first hyperpolarizability, the incorrect evolution with the chain length predicted by HF is strongly worsened by BLYP, Perdew-Burke-Ernzerhof (PBE), and also by B3LYP and PBE0. On the reverse, LC-BLYP and LC-PBE hyperpolarizabilities are correctly predicted to be positive (but for the two smallest chains). Indeed, for medium and long oligomers LC hyperpolarizabilities are slightly smaller than MP2 hyperpolarizabilities, as it should be. CAM-B3LYP also strongly improves the B3LYP results, though a bit less impressively for small chain lengths. The present study demonstrates the efficiency of long-range DFT, even in very pathological cases.

Using the long-range correction (LC) density functional theory (DFT) scheme introduced by Iikura et al. [J. Chem. Phys. 115, 3540 (2001)] and the Coulomb-attenuating model (CAM-B3LYP) of Yanai et al. [Chem. Phys. Lett. 393, 51 (2004)], we have calculated a series of properties that are known to be poorly reproduced by standard functionals: Bond length alternation of pi-conjugated polymers, polarizabilities of delocalized chains, and electronic spectra of extended dyes. For each of these properties, we present cases in which traditional hybrid functionals do provide accurate results and cases in which they fail to reproduce the correct trends. The quality of the results is assessed with regard to experimental values and/or data arising from electron-correlated wave function approaches. It turns out that (i) both LC-DFT and CAM-B3LYP provide an accurate bond length alternation for polyacetylene and polymethineimine, although for the latter they decrease slightly too rapidly with chain length. (ii) The LC generalized gradient approximation and MP2 polarizabilities of long polyphosphazene and polymethineimine oligomers agree almost perfectly. In the same way, CAM-B3LYP corrects the major part of the B3LYP faults. (iii) LC and CAM techniques do not help in correcting the nonrealistic evolution with chain length of the absorption wavelengths of cyanine derivatives. In addition, though both schemes significantly overestimate the ground to excited state transition energy of substituted anthraquinone dyes, they provide a more consistent picture once a statistical treatment is performed than do traditional hybrid functionals.

While density functional theory (DFT) has been proven to be extremely useful for the prediction of thermodynamic and spectroscopic properties of molecules, to date most functionals used in common implementations of DFT display a systematic failure to predict the properties of charge-transfer processes. While this is explicitly manifest in Rydberg transitions of atoms and molecules and in molecular charge-transfer spectroscopy, it also becomes critical for systems containing extended conjugation such as polyenes and other conducting polymers, porphyrins, chlorophylls, etc. A new density functional, a Coulomb-attenuated hybrid exchange-correlation functional (CAM-B3LYP), has recently been developed specifically to overcome these limitations, and it has been shown to properly predict molecular charge-transfer spectra. Here, we demonstrate that it predicts qualitatively reasonable spectra for porphyrin, some oligoporphyrins, and chlorophyll. However, alternate density functionals developed to overcome the same limitations such as currentdensity functional theory are shown, in their present implementation, to remain inadequate. The CAM-B3LYP results are shown to be in excellent agreement with complete-active-space plus second-order M011er - Plesset perturbation theory and symmetry-adapted cluster configuration interaction calculations: These depict the N and higher bands of porphyrins and chlorophylls as being charge-transfer bands associated with localization of molecular orbitals on individual pyrrole rings. The validity of the basic Gouterman model for the spectra of porphyrins and chlorophylls is confirmed, rejecting modern suggestions that non-Gouterman transitions lie close in energy to the Q-bands of chlorophylls. As porphyrins and chlorophylls provide useful paradigms for problems involving extended conjugation, the results obtained suggest that many significant areas of nanotechnology and biotechnology may now be realistically treated by cost-effective density-f

The inability of standard density functionals to correctly predict charge-transfer excitation bands is a well-known problem. This shortcoming has been attributed to the incorrect treatment by the functionals of the long-range exchange potential. Accordingly, a number of long-range corrected schemes have been proposed to deal with this situation. We have applied the CAM-B3LYP variant to the zincbacteriochlorin-bacteriochlorin complex, a system which highlights this problem, and have found a significant improvement in the calculation of its excitation bands over other functionals. In particular, the spuriously low charge-transfer states found previously do not appear for CAM-B3LYP.