Selectivity in the mechanism of action of antimicrobial mastoparan peptide Polybia-MP1

Many potent antimicrobial peptides also present hemolytic activity, an undesired collateral effect for the therapeutic application. Unlike other mastoparan peptides, Polybia-MP1 (IDWKKLLDAAKQIL), obtained from the venom of the social wasp Polybia paulista, is highly selective of bacterial cells. The study of its mechanism of action demonstrated that it permeates vesicles at a greater rate of leakage on the anionic over the zwitterionic, impaired by the presence of cholesterol or cardiolipin; its lytic activity is characterized by a threshold peptide to lipid molar ratio that depends on the phospholipid composition of the vesicles. At these particular threshold concentrations, the apparent average pore number is distinctive between anionic and zwitterionic vesicles, suggesting that pores are similarly formed depending on the ionic character of the bilayer. To prospect the molecular reasons for the strengthened selectivity in Polybia-MP1 and its absence in Mastoparan-X, MD simulations were carried out. Both peptides presented amphipathic alpha-helical structures, as previously observed in Circular Dichroism spectra, with important differences in the extension and stability of the helix; their backbone solvation analysis also indicate a different profile, suggesting that the selectivity of Polybia-MP1 is a consequence of the distribution of the charged and polar residues along the peptide helix, and on how the solvent molecules orient themselves according to these electrostatic interactions. We suggest that the lack of hemolytic activity of Polybia-MP1 is due to the presence and position of Asp residues that enable the equilibrium of electrostatic interactions and favor the preference for the more hydrophilic environment.

The gas flow rate increase obtained by an oscillating piezoelectric actuator on a micronozzle

Micronozzles with piezoelectric actuator were fabricated and investigated. The micronozzles were fabricated in glass substrates using a powder-blasting technique, and the actuator is a bimorph structure made from a piezoelectric polymer. The actuator was located at the nozzle outlet, and was driven in an oscillating mode by applying an alternating voltage across the actuator electrodes. With a pressure difference between inlet and outlet, the gas flow rate through the device was increased. This effect was quantified, and compared to a similar micronozzle with no actuator. The increase in the flow rate was defined as the gas flow through the micronozzle with actuator oscillating minus the gas flow without actuator, was found to depend on the inlet pressure, the pressure ratio, and the nozzle throat diameter. (C) 2008 Elsevier B.V. All rights reserved.

Historical carbon budget of the brazilian ethanol program

This work models the carbon neutralization capacity of Brazil`s ethanol program since 1975. In addition to biofuel, we also assessed the mitigation potential of other energy products, such as, bioelectricity, and CO(2) emissions captured during fermentation of sugar cane`s juice. Finally, we projected the neutralization capacity of sugar cane`s bio-energy system over the next 32 years. The balance between several carbon stocks and flows was considered in the model, including the effects of land-use change. Our results show that the neutralization of the carbon released due to land-use change was attained only in 1992, and the maximum mitigation potential of the sugar cane sector was 128 tonnes Of CO(2) per ha in 2006. An ideal reconstitution of the deployment of the sugar cane sector, including the full exploitation of bio-electricity`s potential, plus the capture Of CO(2) released during fermentation, shows that the neutralization of land-use change emissions would have been achieved in 1988, and its mitigation potential would have been 390 tCO(2)/ha. Finally, forecasts of the sector up to 2039 shows that the mitigation potential in 2039 corresponds to 836 tCO(2)/ha, which corresponds to 5.51 kg Of CO(2) per liter of ethanol produced, or 55% above the negative emission level. (C) 2009 Elsevier Ltd. All rights reserved.

The Schenberg spherical gravitational wave detector: the first commissioning runs

Here we present a status report of the first spherical antenna project equipped with a set of parametric transducers for gravitational detection. The Mario Schenberg, as it is called, started its commissioning phase at the Physics Institute of the University of Sao Paulo, in September 2006, under the full support of FAPESP. We have been testing the three preliminary parametric transducer systems in order to prepare the detector for the next cryogenic run, when it will be calibrated. We are also developing sapphire oscillators that will replace the current ones thereby providing better performance. We also plan to install eight transducers in the near future, six of which are of the two-mode type and arranged according to the truncated icosahedron configuration. The other two, which will be placed close to the sphere equator, will be mechanically non-resonant. In doing so, we want to verify that if the Schenberg antenna can become a wideband gravitational wave detector through the use of an ultra-high sensitivity non-resonant transducer constructed using the recent achievements of nanotechnology.

The Schenberg data acquisition and analysis: results from its first commissioning run

The Mario Schenberg gravitational wave detector has started its commissioning phase at the Physics Institute of the University of Sao Paulo. We have collected almost 200 h of data from the instrument in order to check out its behavior and performance. We have also been developing a data acquisition system for it under a VXI System. Such a system is composed of an analog-to-digital converter and a GPS receiver for time synchronization. We have been building the software that controls and sets up the data acquisition. Here we present an overview of the Mario Schenberg detector and its data acquisition system, some results from the first commissioning run and solutions for some problems we have identified.

Azo-group dihedral angle torsion dependence on temperature: A theorerical-experimental study

Quantum chemical calculations were carried out to explain the observed shifts in the absorption spectrum of different azo-aromatic compounds due to changes in the dihedral angle of the azo-group. Our results reveal that the pi-pi* transition presents a hypsochromic shift and an oscillator strength drop upon increase of the dihedral angle. Nevertheless, the pi-pi* transition exhibits the opposite behavior. This effect is attributed to the reduction in the pi-electron conjugation length of the molecule. Experimentally, we performed temperature dependence measurements of the linear absorption spectrum. Both the theoretical and experimental results demonstrate that small energy changes are mirrored in the electronic transitions of conjugated linear molecules. (C) 2010 Elsevier B.V. All rights reserved.

Excited-state absorption spectroscopy in oxidized Cytochrome c

This work reports on the excited-state absorption spectrum of oxidized Cytochrome c (Fe(3+)) dissolved in water, measured with the Z-scan technique with femtosecond laser pulses. The excited-state absorption cross-sections between 460 and 560 nm were determined with the aid of a three-energy-level model. Reverse saturable absorption was observed below 520 nm, while a saturable absorption process occurs in the Q-band, located around 530 nm. Above 560 nm, a competition between saturable absorption and two-photon absorption was inferred. These results show that Cytochrome c presents distinct nonlinear behaviors, which may be useful to study electron transfer chemistry in proteins by one- and two-photon absorption. In addition, owing to these nonlinear optical features, this molecule may be employed in applications involving photodynamics therapy and saturable absorbers. (C) 2009 Elsevier B.V. All rights reserved.

Nonlinear refractive index of RECOB (RE = Gd and La) crystals

The Z-scan technique is employed to obtain the nonlinear refractive index (n (2)) of the Ca(4)REO(BO(3))(3) (RECOB, where RE = Gd and La) single crystals using 30 fs laser pulses centered at 780 nm for the two orthogonal orientations determined by the optical axes (X and Z) relative to the direction of propagation of the laser beam (k//Y// crystallographic b-axis). The large values of n (2) indicate that both GdCOB and LaCOB are potential hosts for Yb:RECOB lasers operating in the Kerr-lens mode locking (KLM) regime.

Experimental and theoretical investigation of first hyperpolarizability in aminophenols

This work reports theoretical and experimental studies on the first hyperpolarizability (beta) of aminophenols, evaluating the influence of the NH(2) group position relative to the OH group on the hyperpolarizability. A new extension of hyper-Rayleigh scattering technique using picosecond pulse trains was employed to obtain the experimental absolute values of (beta). The theoretical static beta(0) values were calculated using AMI method implemented in the AMPAC program. The theoretical and experimental data show a clear dependence between beta and the relative position of the electron donor (D) and acceptor (A) groups, presenting the 2-aminophenol the higher values. Moreover, calculations show excellent qualitative agreement between theoretical and experimental data, which are improved when the simulations considering the solvated molecule in a combination of discrete solvent molecules interacting with the solute and the application of continuous dielectric model. Besides, the study indicates that the experimental hyperpolarizabilities seem to be a property of the solute-solvation shell system. These facts have affirmed that the theoretical approach employed can be successfully used to foresee the variation in beta due to modifications in the D/A position. Moreover, a theoretical study of the ground state absorption is performed and compared with experimental data. (C) 2008 Elsevier B.V. All rights reserved.

Remote Spectroscopy in the Visible Using Fibers on the Optical Internet Network

The work presented here demonstrates the feasibility of using the single-mode fibers of an optical Internet network to deliver visible light between separate laboratories as a way to perform remote spectroscopy in the visible for teaching purposes. The coupling of a broadband light source into the single-mode fiber (SMF) and the characterization of optical losses as a function of the wavelength are discussed. Sample spectra were measured with a portable spectrometer controlled by an acquisition program developed with the LabVIEW software that allows the data to be collected and analyzed.