Hydrogen bonding donation of N-methylformamide with dimethylsulfoxide and water

20% N-methylformamide (NMF) mixtures with water and with dimethylsulfoxide (DMSO) have been studied. A comparison between the hydrogen bonding (H-bond) donation of N-methylformamide with both solvents in the mixtures is presented. Results of radial distribution functions, pair distribution energies, molecular dipole moment correlation, and geometry of the H-bonded species in each case are shown. The results indicate that the NMF-solvent H-bond is significantly stronger with DMSO than with water. The solvation shell is best organized in the DMSO mixture than in the aqueous one. © 2013 Elsevier B.V. All rights reserved.

On the hydrogen bonding between N-methylformamide and acetone and tetrahydrofuran

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo da dinâmica de solvatação de peptídeos por QM/MM

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Limestone and oyster shell for brown layers in their second egg production cycle

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Strutural and optical approach of CdS@ZnS core-shell system

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Design of concrete platforms offshore using the three-layer shell theory

The concrete offshore platforms, which are subjected a several loading combinations and, thus, requires an analysis more generic possible, can be designed using the concepts adopted to shell elements, but the resistance must be verify in particular cross-sections to shear forces. This work about design of shell elements will be make using the three-layer shell theory. The elements are subject to combined loading of membrane and plate, totalizing eight components of internal forces, which are three membrane forces, three moments (two out-of-plane bending moments and one in-plane, or torsion, moment) and two shear forces. The design method adopted, utilizing the iterative process proposed by Lourenco & Figueiras (1993) obtained from equations of equilibrium developed by Gupta (1896) , will be compared to results of experimentally tested shell elements found in the literature using the program DIANA.

Dynamics of meso and thermo citrate synthases with implicit solvation

The dynamics of hydration of meso and thermo citrate synthases has been investigated using the EEF1 methodology implemented with the CHARNM program. The native enzymes are composed of two identical subunits, each divided into a small and large domain. The dynamics behavior of both enzymes at 30 degrees C and 60 degrees C has been compared. The results of simulations show that during the hydration process, each subunit follows a different pathway of hydration, in spite of the identical sequence. The hydrated structures were compared with the crystalline structure, and the root mean square deviation (RMSD) of each residue along the trajectory was calculated. The regions with larger and smaller mobility were identified. In particular, helices belonging to the small domain are more mobile than those of the large domain. In contrast, the residues that constitute the active site show a much lower displacement compared with the crystalline structure. Hydration free energy calculations point out that Thermoplasma acidophilum citrate synthase (TCS) is more stable than chicken citrate synthase (CCS), at high temperatures. Such result has been ascribed to the higher number of superficial charges in the thermophilic homologue, which stabilizes the enzyme, while the mesophilic homologue denatures. These results are in accord with the experimental found that TCS keeps activity at temperatures farther apart from the catalysis regular temperature than the CCS. (c) 2005 Wiley Periodicals, Inc.

Quantitative comparisons and models of time-averaging in bivalve and brachiopod shell accumulations

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

ESR dating of a subfossil shell from Couve Island, Ubatuba, Brazil

The occurrence of subfossil material in bottom sediments of Couve Island, Ubatuba region, São Paulo State, is confirmed. The analyzed material consists of a bivalve shell that was dated by the electron spin resonance technique. By the additive irradiation method an archaeological absorbed dose of (25 +/- 5) Gy was obtained and calibration with other dating works in the same area allows the inference of an age of (25 +/- 5) x 10(2) years. The importance of this finding and its paleoecological implications could contribute to elucidating the nature of short-term environmental changes in the Brazilian coastline during the Holocene, as well as becoming an important tool to the understanding of the distribution and biological aspects of the bivalve fauna. (C) 2002 Elsevier B.V. Ltd. All rights reserved.

Biology and shell relationship in Clibanarius vittatus (Bosc, 1802) (Crustacea, Diogenidae) from Sao Vicente, SP, Brasil.

This study aimed to characterize the populational structure of Clibanarius vittatus (Bosc, 1802), as well as to determine the morphometric relations between the animal's size and the variables: length of their chelar propodus and the size of the shell opening. C. vittatus is a relatively abundant pagurid on the west Atlantic coast, it occurs in the intertidal region from 38 degrees N to 28 degrees S. The animals in this study were randomly sampled every month on the Paranapu (a) over tilde Beach (46 degrees 23' S e 23 degrees 59' W), S (a) over tilde $ o Vicente (SP), Brazil. The biometrics data were adjusted to the power equation (y = ax(b)), by means of the minimum square method. A total of 427 individuals were collected. The size of the cephalothoraxic shield ranged from 2.5 to 12.7 mm, evidencing a representative sample of the population. The of most commonly genus of Gastropoda shells occupied by the hermits was Thais (97,26%). In relation to the morphometric analyses performed, it was observed a positive correlation between the animal size and the variables length of the chelar propodus and the size of the shells.

Patterns of shell utilization in Petrochirus diogenes (Decapoda, Anomura, Diogenidae) in the Ubatuba region, São Paulo, Brazil

The objective of this study is to investigate the patterns of shell utilization in Petrochirus diogenes in the Ubatuba region, SP, Brazil. Hermit crabs were obtained from 1993 to 1996 with the aid of a shrimp fishery boat equipped with two double-rigged trawling nets. Shells were identified and weighed, and their maximum aperture width was measured. Hermit crabs were weighed, and their shield length was recorded. A total of 634 P. diogenes specimens, occupying shells of 12 gastropod species, was obtained. The shells of Tonna galea, Zidona dufresnei and Strombus pugilis were the most frequently occupied, the first marked by its larger aperture width and lower average weight. Small hermit crabs inhabited a wide variety of gastropod shells due to their higher availability. However, the utilization of T. galea shells became predominant as the crabs attained larger sizes. Differences in weight and aperture width are known to encourage certain shell utilization patterns and may affect growth and reproduction of hermit crabs.

Shell beds as paleoecological puzzles: A case study from the Upper Permian of the Parana Basin, Brazil

Microstratigraphic, sedimentological, and taphonomic features of the Ferraz Shell Bed, from the Upper Permian (Kazanian-Tatarian?) Corumbatai Formation of Rio Claro Region (the Parana Basin, Brazil), indicate that the bed consists of four distinct microstratigraphic units. They include, from bottom to top, a lag concentration (Unit 1), a partly reworked storm deposit (Unit 2), a rapidly deposited sandstone unit with three thin horizons recording episodes of reworking (Unit 3), and a shell-rich horizon generated by reworking/winnowing that was subsequently buried by storm-induced obrution deposit (Unit 4). The bioclasts of the Ferraz Shell Bed represent exclusively bivalve mollusks. Pinzonella illusa and Terraia aequilateralis are the dominant species. Taphonomic analysis indicates that mollusks are heavily time-averaged (except for some parts of Unit 3). Moreover, different species are time-averaged to a different degree (disharmonious time-averaging). The units differ statistically from one another in their taxonomic and ecological composition, in their taphonomic pattern, and in the size-frequency distributions of the two most common species. Other Permian shell beds of the Parana Basin are similar to the Ferraz Shell Bed in their faunal composition (they typically contain similar sets of 5 to 10 bivalve species) and in their taphonomic, sedimentologic, and microstratigraphic characteristics. However, rare shell beds that include 2-3 species only and are dominated by articulated shells preserved in life position also occur. Diversity levels in the Permian benthic associations of the Parana Basin were very low, with the point diversity of 2-3 species and with the within-habitat and basin-wide (alpha and gamma) diversities of 10 species, at most. The Parana Basin benthic communities may have thus been analogous to low-diversity bivalve-dominated associations of the present-day Baltic Sea. The 'Ferraz-type' shell beds of the Parana Basin represent genetically complex and highly heterogeneous sources of paleontological data. They are cumulative records of spectra of benthic ecosystems time-averaged over long periods of time (10(2)-10(4) years judging from actualistic research). Detailed biostratinomic reconstructions of shell beds can not only offer useful insights into their depositional histories, but may also allow paleoecologists to optimize their sampling designs, and consequently, refine paleoecological and paleoenvironmental interpretations.

Use of genetic algorithms and solvation potential to study peptides structure

In this work, genetic algorithms concepts along with a rotamer library for proteins side chains and implicit solvation potential are used to optimize the tertiary structure of peptides. We starting from the known PDB structure of its backbone which is kept fixed while the side chains allowed adopting the conformations present in the rotamer library. It was used rotamer library independent of backbone and a implicit solvation potential. The structure of Mastoporan-X was predicted using several force fields with a growing complexity; we started it with a field where the only present interaction was Lennard-Jones. We added the Coulombian term and we considered the solvation effects through a term proportional to the solvent accessible area. This paper present good and interesting results obtained using the potential with solvation term and rotamer library. Hence, the algorithm (called YODA) presented here can be a good tool to the prediction problem. (c) 2007 Elsevier B.V. All rights reserved.

Predicting peptides structure with solvation potential and rotamer library dependent of the backbone

In this work, genetic algorithms concepts along with a rotamer library dependent of backbone and implicit solvation potential are used to study the tertiary structure of peptides. We starting from known primary sequence and optimize the structure of the backbone while the side chains allowed adopting the conformations present in a rotamer library. The GA, implemented with two force fields with a growing complexity, was used predict the structure of a polyalanine and a poly-isolueucine. This paper presents good and interesting results about the study of peptides structures and about the development of computational tools to study peptides structures. (C) 2007 Elsevier B.V. All rights reserved.

General massive one-loop off-shell three-point functions

In this work we compute the most general massive one-loop off-shell three-point vertex in D-dimensions, where the masses, external momenta and exponents of propagators are arbitrary. This follows our previous paper in which we have calculated several new hypergeometric series representations for massless and massive (with equal masses) scalar one-loop three-point functions, in the negative dimensional approach.