Characterization and in vitro evaluation of bacterial cellulose membranes functionalized with osteogenic growth peptide for bone tissue engineering

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

Proteomic profiling of the molecular targets of interactions of the mastoparan peptide Protopolybia MP-III at the level of endosomal membranes from rat mast cells

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

CHARGED PARTICLE DYNAMICS IN TIME DEPENDENT MAGNETIC FIELDS

In this work we study the behavior of charged particles immersed in a peculiar configuration of magnetic fields, which has a main constant field B(0) and a superimposed, transversal perturbation field B(1) sin(omega(p)t), with B(1) << B(0). By taking Cartesian coordinates and placing B(0) along the z axis and B(1) sin (omega(p)t) on the x axis, an analytical solution for y(t) may be obtained by solving an integrodifferential equation. Besides, the solution z(t) also exhibits a very interesting dynamics, and the entire system is conditioned by resonances between the particle orbit frequencies and the frequency of the magnetic transversal perturbation, omega(p). In this work we also discuss numerical simulations for the related particle trajectories, as well as potential applications in the context of separation phenomena.

Tertiary structural changes of the alpha-hemolysin from Staphylococcus aureus on association with liposome membranes

The interaction of alpha-hemolysin (also called alpha-toxin) from Staphylococcus aureus with mixed egg-yolk phosphatidylcholine/cholesterol liposomes has been investigated using the intrinsic tryptophan fluorescence emission (ITFE) signal. The ITFE intensity of alpha-hemolysin, which was obtained using a novel purification protocol, showed a triphasic increase on incubation with liposomes at low protein/lipid ratios. The first, rapid phase results in an increase in ITFE of 10%, which reflects rapid conformation changes in the alpha-hemolysin on association with the liposome membrane, the second phase of the ITFE increase is associated with a red shift from 334 to 339 nm in the maximum emission wavelength, suggesting the transition to a partially unfolded intermediate in the oligomerization process. The third phase of the ITFE intensity change demonstrates a temporal correlation with the appearance of SDS-stable oligomers. The results demonstrate the feasibility of identification of intermediate protein conformations in complex membrane-associated processes by manipulation of the liposomal membrane composition. (C) 1998 Academic Press.

Interactions of mast cell degranulating peptides with model membranes: A comparative biophysical study

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Crystal structure of a dimeric Ser49 PLA(2)-like myotoxic component of the Vipera ammodytes meridionalis venomics reveals determinants of myotoxicity and membrane damaging activity

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Influence of the Bilayer Composition on the Binding and Membrane Disrupting Effect of Polybia-MP1, an Antimicrobial Mastoparan Peptide with Leukemic T-Lymphocyte Cell Selectivity

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

New Insight into the Mechanism of Action of Wasp Mastoparan Peptides: Lytic Activity and Clustering Observed with Giant Vesicles

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Study of the mechanism of action of anoplin, a helical antimicrobial decapeptide with ion channel-like activity, and the role of the amidated C-terminus

Anoplin, an antimicrobial, helical decapeptide from wasp venom, looses its biological activities by mere deamidation of its C-terminus. Secondary structure determination, by circular dichroism spectroscopy in amphipathic environments, and lytic activity in zwitterionic and anionic vesicles showed quite similar results for the amidated and the carboxylated forms of the peptide. The deamidation of the C-terminus introduced a negative charge at an all-positive charged peptide, causing a loss of amphipathicity, as indicated by molecular dynamics simulations in TFE/water mixtures and this subtle modification in a peptide's primary structure disturbed the interaction with bilayers and biological membranes. Although being poorly lytic, the amidated form, but not the carboxylated, presented ion channel-like activity on anionic bilayers with a well-defined conductance step; at approximately the same concentration it showed antimicrobial activity. The pores remain open at trans-negative potentials, preferentially conducting cations, and this situation is equivalent to the interaction of the peptide with bacterial membranes that also maintain a high negative potential inside. Copyright (C) 2007 European Peptide Society and John Wiley & Sons, Ltd.

Polyurethane and PTFE membranes for guided bone regeneration: Histopathological and ultrastructural evaluation

Objective: The purpose of this study was to research a membrane material for use in guided bone regeneration. Study design: In this study, 25 male Wistar rats were used to analyze the biocompatibility and degradation process of biomembranes. The morphological changes in subcutaneous implantations were assessed after 7, 14, 21, 28 and 70 days. The materials were made of polyurethane polymer (AUG) obtained from vegetal oil (Ricinus communis) and polytetrafluoroethylene membrane (PTFE). The surface characteristics of the physical barriers in scanning electronic microscopic (SEM) were also evaluated. Results: In both groups, the initial histological analysis showed moderate inflammatory infiltrate, which was predominantly polymorphonuclear. There was also a presence of edema, which was gradually replaced by granulation tissue, culminating in a fibrous capsule. In the AUG group, some multinucleated giant cells were present in the contact interface, with the space previously occupied by the material. However, membrane degradation was not observed during the period studied. According to the present SEM findings, porosity was not detected in the AUG or PTFE membranes. Conclusion: The researched material is biocompatible and the degradation process is extremely slow or may not even occur at all.

Influence of Osteopenia in Autogenous Bone Graft Healing With or Without Expanded Polytetrafluoroethylene Membranes: Histologic and Histomorphometric Study in Rats

Purpose: The aim of this study was to quantitatively evaluate and qualitatively describe autogenous bone graft healing with or without an expanded polytetrafluoroethylene (e-PTFE) membrane in ovariectornized rats. Materials and Methods: Eighty Wistar rats, weighing approximately 300 g each, were used. A graft was obtained from the parietal bone and fixed to the sidewall of each animal's left mandibular ramus. The animals were randomly divided into four experimental groups (n = 20 in each group): group 1, sham operated and autogenous bone graft only- group 2, sham operated and autogenous bone graft covered by e-PTFE membrane; group 3, ovariectornized (OVX) and autogenous bone graft only- group 4, OVX and autogenous bone graft covered by e-PTFE membrane. The animals were sacrificed at five different time points: immediately after grafting or at 7, 21, 45, or 60 days after grafting. Histologic examination and morphometric measurement of the sections were performed, and values were submitted to statistical analyses. Results: Both groups (sham and OVX) experienced loss of the original graft volume when it was not covered by the membrane, whereas use of the membrane resulted in additional bone formation beyond the edges of the graft and under the membrane. Histologic analysis showed integration of the grafts in all animals, although a larger number of marrow spaces was found in OVX groups. Conclusions: Association of bone graft with an e-PTFE membrane resulted in maintenance of its original volume as well as formation of new bone that filled the space under the membrane. Osteopenia did not influence bone graft repair, regardless of whether or not it was associated with e-PTFE membrane, but descriptive histologic analysis showed larger numbers of marrow spaces in the bone graft and receptor bed and formation of new bone in the OVX animals. INT J ORAL MAXILLOFAC IMPLANTS 2009;24:1074-1082

Overspinning a nearly extreme charged black hole via a quantum tunneling process

We examine a nearly extreme macroscopic Reissner-Nordstrom black hole in the context of semiclassical gravity. The absorption rate associated with the quantum tunneling process of scalar particles whereby this black hole can acquire enough angular momentum to violate the weak cosmic-censorship conjecture is shown to be nonzero.

Electrically charged topological solitons

Two new families of T-dual integrable models of dyonic type are constructed. They represent specific A(n)((1)) singular non-abelian affine Toda models having U(1) global symmetry. Their I-soliton spectrum contains both neutral and U(I)-charged topological solitons sharing the main properties of 4-dimensional Yang-Mills-Higgs monopoles and dyons. The semiclassical quantization of these solutions as well as the exact counterterms and the coupling constant renormalization are studied. (C) 2001 Elsevier B.V. B.V. All rights reserved.

Signature of charged to neutral Higgs boson decay at the LHC in SUSY models

We study the signature of H+/- decay into h(0)W at the LHC in SUSY models. It has only marginal viability in the MSSM. But in the singlet extensions like the NMSSM one can have a spectacular signature for H+/- decay into (h(0), A(0))W over a significant domain of parameter space. (C) 1999 Published by Elsevier B.V. B.V. All rights reserved.

Search for doubly charged Higgs boson pair production in the decay to mu(+)mu(+)mu(-)mu(-) in p(p)over-bar collisions at root s=1.96 TeV

A search for pair production of doubly charged Higgs bosons in the process p (p) over bar -->H++H---->mu(+)mu(+)mu(-)mu(-) is performed with the D0 run II detector at the Fermilab Tevatron. The analysis is based on a sample of inclusive dimuon data collected at an energy of roots=1.96 TeV, corresponding to an integrated luminosity of 113 pb(-1). In the absence of a signal, 95% confidence level mass limits of M(H-L(+/-+/-))>118.4 GeV/c(2) and M(H-R(+/-+/-))>98.2 GeV/c(2) are set for left-handed and right-handed doubly charged Higgs bosons, respectively, assuming 100% branching into muon pairs.