How C-terminal carboxyamidation alters the biological activity of peptides from the venom of the eumenine solitary wasp

Inflammatory peptides display different types of post-transcriptional modifications, such as C-terminal amidation, that alter their biological activity. Here we describe the structural and molecular dynamics features of the mast cell degranulating peptide, eumenine mastoparan-AF (EMP-AF-NH2), found in the venom of the solitary wasp, and of its carboxyl-free C-terminal form (EMP-AF-COO-) characterized by a reduced activity. Circular dichroism indicates that both peptides switch from a random coil conformation in water to a helical structure in TFE and SDS micelles. NMR data, in 30% TFE, reveal that the two peptides fold into an alpha-helix spanning most of their length, while they differ in terms of molecular rigidity. To understand the origins of the conformational flexibility observed in the case of EMP-AF-COO-, a 5 ns MD simulation was carried out for each peptide, in an explicit water/TFE environment. The results show that the two peptides differ in an H-bond between Leu14 NH2 and the backbone carbonyl of Ile11. The loss of that H-bond in EMP-AF-COO- leads to a significant modification of its structural dynamics. In fact, as evidenced by essential dynamics analysis, while EMP-AF-NH2 exists mainly as a rigid structure, EMP-AF-COO- presents two helical stretches that fluctuate in some sort of independent fashion. We conclude that the diverse biological activity of the two peptides is not simply due to the reduction of the net positive charge, as generally suggested, but also to a structural perturbation of the amphipathic alpha-helix that affects their ability to perturb the cell membrane.

Conformational features of cepacian: the exopolysaccharide produced by clinical strains of Burkholderia cepacia

Conformational energy calculations and molecular dynamics investigations, both in water and in dimethyl sulfoxide, were carried out on the exopolysaccharide cepacian produced by the majority of the clinical strains of Burkholderia cepacia, an opportunistic pathogen causing serious lung infection in patients affected by cystic fibrosis, the investigation was aimed at defining the structural and conformational features, which might be relevant for clarification of the structure-function relationships of the polymer. The molecular dynamics calculations were carried out by Ramachandran-type energy plots of the disaccharides that constitute the polymer repeating unit. The dynamics of an oligomer composed of three repeating units were investigated in water and in Me2SO, a non-aggregating solvent. Analysis of the time persistence of hydrogen bonds showed the presence of a large number of favourable interactions in water, which were less evident in Me2SO. The calculations on the cepacian chain indicated that polymer conformational features in water were affected by the lateral chains, but were also largely dictated by the presence of solvent. Moreover, the large number of intra-chain hydrogen bonds in water disappeared in Me2SO solution, increasing the average dimension of the polymer chains. (c) 2005 Elsevier Ltd. All rights reserved.

Nonzero Gap Two-Dimensional Carbon Allotrope from Porous Graphene

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

CRYSTALLINE FRAGMENTS IN GLASSES

The nature of tetrahedral molecular fragments is investigated in SiSe2 glasses using the molecular-dynamics method. The glass consists of both edge-sharing (ES) and corner-sharing tetrahedra. The ES tetrahedra are the building blocks of chain-like-molecular fragments. The two-edge-sharing tetrahedra are the nucleus, and corner-sharing configurations provide connecting hinges between fragments. Statistics of rings and fragments reveals that threefold and eightfold rings are most abundant, chainlike fragments that are typically 10-15 angstrom long occur mostly in eightfold rings, and the longest fragments occur in elevenfold rings.

Generalized simulated annealing: Application to silicon clusters

We have compared the recently introduced generalized simulated annealing (GSA) with conventional simulated annealing (CSA). GSA was tested as a tool to obtain the ground-state geometry of molecules. We have used selected silicon clusters (Sin, n=4-7,10) as test cases. Total energies were calculated through tight-binding molecular dynamics. We have found that the replacement of Boltzmann statistics (CSA) by Tsallis's statistics (GSA) has the potential to speed up optimizations with no loss of accuracy. Next, we applied the GSA method to study the ground-state geometry of a 20-atom silicon cluster. We found an original geometry, apparently lower in energy than those previously described in the literature.

Preparation, characterization and spectroscopy of the europium diphenylphosphinate complex

The purpose of this work is to study the preparation and spectroscopic behavior of the europium diphenylphosphinate complex -Eu(DPP)3. Elemental and thermogravimetric analysis, powder X-ray diffractometry, and infrared spectroscopy were applied to characterize the formula of the final product and the sixfold coordination of the Eu3+ ion. Excitation and emission spectra have been recorded at liquid nitrogen and room temperatures. The 5D0→7F2 transition intensity decreases when T decreases in comparison to the 5D0→7F1 transition intensity. Molecular mechanic calculations were developed in order to obtain the spatial coordinates of the Eu3+ and ligand ions. The simple overlap model was used to calculate the total splitting of the 5D0→7F1 transition, 5D0→7F0/5D 0→7F2 ntensity ratio and the intensity parameters, Ωλ (λ=2 and 4). Good agreements between theoretical predictions and experimental results have been obtained with g=2/3 as the effective charge and α=0.8×10-24 cm3 as the isotropic polarizability of the oxygen. © 1998 Elsevier Science S.A.

Solid-state NMR, ionic conductivity, and thermal studies of lithium-doped siloxane-poly(propylene glycol) organic-inorganic nanocomposites

Hybrid organic-inorganic ionic conductors, also called ormolytes (organically modified electrolytes), were obtained by dissolution of LiClO 4 in siloxane-poly(propylene glycol) matrixes. The dynamic features of these nanocomposites were studied and correlated to their electrical properties. Solid-state nuclear magnetic resonance (NMR) spectroscopy was used to probe the effects of the temperature and nanocomposite composition on the dynamic behaviors of both the ionic species ( 7Li) and the polymer chains ( 13C). NMR, dc ionic conductivity, and DSC results demonstrate that the Li + mobility is strongly assisted by the segmental motion of the polymer chain above its glass transition temperature. The ac ionic conductivity in such composites is explained by use of the random free energy barrier (RFEB) model, which is agreement with their disordered and heterogenous structures. These solid ormolytes are transparent and flexible, and they exhibit good ionic conductivity at room temperature (up to 10 -4 S/cm). Consequently, they are very promising candidates for use in several applications such as batteries, sensors, and electrochromic and photoelectro-chemical devices.

Direct signals for large extra dimensions in the production of fermion pairs at linear colliders

We analyze the potential of the next generation of e+e- linear colliders to search for large extra dimensions via the production of fermion pairs in association with Kaluza-Klein gravitons (G), i.e., e+e- →ff̃G. This process leads to a final state exhibiting a significant amount of missing energy in addition to acoplanar lepton or jet pairs. We study in detail this reaction using the full tree level contributions due to the graviton emission and the standard model backgrounds. After choosing the cuts to enhance the signal, we show that a linear collider with a center-of-mass energy of 500 GeV will be able to probe quantum gravity scales from 0.96 (0.86) up to 4.1 (3.3) TeV at a 2 (5)σ level, depending on the number of extra dimensions. ©2001 The American Physical Society.

Scaling limit of virtual states of triatomic systems

Natural scales determine the physics of quantum few-body systems with short-range interactions. Thus, the scaling limit is found when the ratio between the scattering length and the interaction range tends to infinity, while the ratio between the physical scales are kept fixed. From the formal point of view, the relation of the scaling limit and the renormalization aspects of a few-body model with a zero-range interaction, through the derivation of subtracted three-body T-matrix equations that are renormalization-group invariant.

Relating a gluon mass scale to an infrared fixed point in pure gauge QCD

The condition for the global minimum of the vacuum energy for a non-Abelian gauge theory with a dynamically generated gauge boson mass scale which implies the existence of a nontrivial IR fixed point of the theory was shown. Thus, this vacuum energy depends on the dynamical masses through the nonperturbative propagators of the theory. The results show that the freezing of the QCD coupling constant observed in the calculations can be a natural consequence of the onset of a gluon mass scale, giving strong support to their claim.

Apoptose em otorrinolaringologia e cabeça e pescoço

This paper intend to review recent advances in our understanding of programmed cell death, or apoptosis, and discuss implications of these basic science advances in the development of causes and potential treatments of a variety of diseases of the head and neck. Conclusions: apoptosis is now understood to be important in the normal development and survival of all multicellular organism. Deregulation of this normally tighly controlled process underlies a variety of disease states, including neoplasia, autoimmune disease, and disorders of the central nervous system. A better understanding of this process and regulation may help otolaryngologists better understand diseases relevant to this specialty and will lead to improved therapeutic interventions.

Weakly bound atomic trimers in ultracold traps

The scaling dependence of the recombination parameter as a function of the ratio between the energies of the atomic dimer and the most excited trimer states was derived. The scaling function tends to a unversal function in the limit of zero-range interaction or infinite scattering length. This paper reports on how one can obtain the trimer binding energy of a trapped atomic system, from the three-body recombination rate and the corresponding two-body scattering length.

The effects of low laser irradiation on angiogenesis in injured rat tibiae

The influence of He-Ne laser radiation on the formation of new blood vessels in the bone marrow compartment of a regenerating area of the mid-cortical diaphysis of the tibiae of young adult rats was studied. A small hole was surgically made with a dentistry burr in the tibia and the injured area received a daily laser therapy over 7 or 14 days transcutaneously starting 24 h from surgery. Incident energy density dosages of 31.5 and 94.5 Jcm-2 were applied during the period of the tibia wound healing investigated. Light microscopic examination of histological sections of the injured area and quantification of the newly-formed blood vessels were undertaken. Low-level energy treatment accelerated the deposition of bone matrix and histological characteristics compatible with an active recovery of the injured tissue. He-Ne laser therapy significantly increased the number of blood vessels after 7 days irradiation at an energy density of 94.5 Jcm-2, but significantly decreased the number of vessels in the 14-day irradiated tibiae, independent of the dosage. These effects were attributed to laser treatment, since no significant increase in blood vessel number was detected between 8 and 15 non-irradiated control tibiae. Molecular mechanisms involved in low-level laser therapy of angiogenesis in post-traumatic bone regeneration needs further investigation.

Quercetin reduces Staphylococcus aureus interaction with neutrophils

Flavonoids, including quercetin, have been reported to modulate the ability of Staphylococcus aureus to adhere to host tissue without exhibiting direct antibacterial activity. In the present study, we evaluated the interaction of S. aureus pretreated with 40 μg/mL of quercetin with neutrophils to assay oxidative burst stimulation, using luminol-amplified chemiluminescence. S. aureus pre-incubated with subinhibitory concentration of quercetin induced significantly less light emission by neutrophils than did untreated bacteria. The results of the present study demonstrate that quercetin decreases S. aureus uptake by neutrophils.

Multiple minima hypersurfaces procedures for biomimetic ligands screening

In this work the interaction of the pesticide carbaryl with two groups of biomimetic ligands, peptides and MIPs was screened by multiple minima hypersurfaces (MMH) procedures, through the AM1 semiempirical method. Data related to the properties of the molecular association of the complex biomimetic ligand-pesticide were obtained and compared with another molecular modeling algorithm named Leapfrog, as included in the Sybyl software package, and experimental results from the literature, remarking good correlation between them. All important MMH program parameters (cells number, box size, conformers) were studied and optimized with the aim of getting the minimum computation time without losing the correlation with experimental data. The data demonstrated that MMH approach can be used as a fast biomimetic ligand screening tool for MIPs. In the case of peptides the computation time was not comparable with the molecular dynamics methods conventionally used for this approach. © 2011 Springer Science+Business Media B.V.