Single molecule study of the DNA denaturation phase transition in the force-torsion space

We use the "magnetic tweezers" technique to reveal the structural transitions that DNA undergoes in the force-torsion space. In particular, we focus on regions corresponding to negative supercoiling. These regions are characterized by the formation of so-called denaturation bubbles, which have an essential role in the replication and transcription of DNA. We experimentally map the region of the force-torsion space where the denaturation takes place. We observe that large fluctuations in DNA extension occur at one of the boundaries of this region, i.e., when the formation of denaturation bubbles and of plectonemes are competing. To describe the experiments, we introduce a suitable extension of the classical model. The model correctly describes the position of the denaturation regions, the transition boundaries, and the measured values of the DNA extension fluctuations.Comment: 5 pages and 4 figur

Universality of One-Dimensional Heat Conductivity

We show analytically that the heat conductivity of oscillator chains diverges with system size N as N^{1/3}, which is the same as for one-dimensional fluids. For long cylinders, we use the hydrodynamic equations for a crystal in one dimension. This is appropriate for stiff systems such as nanotubes, where the eventual crossover to a fluid only sets in at unrealistically large N. Despite the extra equation compared to a fluid, the scaling of the heat conductivity is unchanged. For strictly one-dimensional chains, we show that the dynamic equations are those of a fluid at all length scales even if the static order extends to very large N. The discrepancy between our results and numerical simulations on Fermi-Pasta-Ulam chains is discussed.Comment: 7 pages, 2 figure

Captura incidental de tartarugas-marinhas em currais-de-pesca no litoral do Piauí, Brasil.

CBO2010

"The dearest of our possessions": applying Floridi's information privacy concept in models of information behavior and information literacy

This conceptual paper argues for the value of an approach to privacy in the digital information environment informed by Luciano Floridi's philosophy of information and information ethics. This approach involves achieving informational privacy, through the features of anonymity and obscurity, through an optimal balance of ontological frictions. This approach may be used to modify models for information behavior and for information literacy, giving them a fuller and more effective coverage of privacy issues in the infosphere. For information behavior, the Information Seeking and Communication Model, and the Information Grounds conception, are most appropriate for this purpose. For information literacy, the metaliteracy model, using a modification a privacy literacy framework, is most suitable

Is the internet the right medium for a 'don't quit campaign'?

This paper examines the effectiveness of promoting post-16 education and training via Internet. It examines the differences between those who intend to continue the post-16 schooling and those who do not. The implication of the findings challenges the effectiveness of a 'don't quit campaign' which was to offer support and guidance on the choice of post 16 options. This study found that the campaign has done very little for those who decided not to continue post-16 education. Consequently, disadvantaged young people need constant support and resources to eliminate the disparities between different groups

Enhancing Optical Up-Conversion Through Electrodynamic Coupling with Ancillary Chromophores

In lanthanide-based optical materials, control over the relevant operating characteristics–for example transmission wavelength, phase and quantum efficiency–is generally achieved through the modification of parameters such as dopant/host combination, chromophore concentration and lattice structure. An alternative avenue for the control of optical response is through the introduction of secondary, codoped chromophores. Here, such secondary centers act as mediators, commonly bridging the transfer of energy between primary absorbers of externally sourced optical input and other sites of frequency-converted emission. Utilizing theoretical models based on experimentally feasible, three-dimensional crystal lattice structures; a fully quantized theoretical framework provides insights into the locally modified mechanisms that can be implemented within such systems. This leads to a discussion of how such effects might be deployed to either enhance, or potentially diminish, the efficiency of frequency up-conversion

Restructured products from tilapia industry by products: the effects of tapioca starch and washing cycles.

The tilapia fileting industry generates large amounts of nutritionally significant waste material, and the recovery of this material is important. The manufacture of restructured products from mechanically recovered fish meat (MRFM) obtained from tilapia fileting allows the use of proteins of high biological value that would otherwise be discharged into the environment. The objective of this study was to evaluate the effect of washing cycles (either one cycle or five cycles) and of the addition of tapioca starch (20% vs. a no-starch control) on the characteristics of surimi obtained from MRFM produced by the tilapia industry and destined for use in restructured products. To evaluate the quality attributes of the product, the structure of a surimi protein matrix and its relationship to selected physicochemical parameters and morphological characteristics was assessed. Both the number of washing cycles and the starch addition were found to influence the moisture, protein and lipid content of the MRFM surimi. Higher whiteness was found after five washing cycles. Because the tapioca starch acted as a stabilizer, the fat globules were more stable and well distributed, and an emulsion with better properties resulted. A homogeneous network of fat globules linked to the protein matrix by a layer of tapioca starch was formed. Another advantage of this approach is that tapioca starch is gluten free. This property is important for specific groups in the population, e.g., celiac-intolerant consumers.Autoria na publicação: FABÍOLA HELENA FOGAÇA

RIP1-HAT1-SirT complex identification and targeting in treatment and prevention of cancer

Purpose: Alteration in cell death is a hallmark of cancer. A functional role regulating survival, apoptosis, and necroptosis has been attributed to RIP1/3 complexes.Experimental Design: We have investigated the role of RIP1 and the effects of MC2494 in cell death induction, using different methods as flow cytometry, transcriptome analysis, immunoprecipitation, enzymatic assays, transfections, mutagenesis, and in vivo studies with different mice models.Results: Here, we show that RIP1 is highly expressed in cancer, and we define a novel RIP1/3-SIRT1/2-HAT1/4 complex. Mass spectrometry identified five acetylations in the kinase and death domain of RIP1. The novel characterized pan-SIRT inhibitor, MC2494, increases RIP1 acetylation at two additional sites in the death domain. Mutagenesis of the acetylated lysine decreases RIP1-dependent cell death, suggesting a role for acetylation of the RIP1 complex in cell death modulation. Accordingly, MC2494 displays tumor-selective potential in vitro, in leukemic blasts ex vivo, and in vivo in both xenograft and allograft cancer models. Mechanistically, MC2494 induces bona fide tumor-restricted acetylated RIP1/caspase-8-mediated apoptosis. Excitingly, MC2494 displays tumor-preventive activity by blocking 7,12-dimethylbenz(α)anthracene-induced mammary gland hyperproliferation in vivoConclusions: These preventive features might prove useful in patients who may benefit from a recurrence-preventive approach with low toxicity during follow-up phases and in cases of established cancer predisposition. Thus, targeting the newly identified RIP1 complex may represent an attractive novel paradigm in cancer treatment and prevention

Equilibrium Properties of A Monomer-Monomer Catalytic Reaction on A One-Dimensional Chain

We study the equilibrium properties of a lattice-gas model of an $A + B \to 0$ catalytic reaction on a one-dimensional chain in contact with a reservoir for the particles. The particles of species $A$ and $B$ are in thermal contact with their vapor phases acting as reservoirs, i.e., they may adsorb onto empty lattice sites and may desorb from the lattice. If adsorbed $A$ and $B$ particles appear at neighboring lattice sites they instantaneously react and both desorb. For this model of a catalytic reaction in the adsorption-controlled limit, we derive analytically the expression of the pressure and present exact results for the mean densities of particles and for the compressibilities of the adsorbate as function of the chemical potentials of the two species.Comment: 19 pages, 5 figures, submitted to Phys. Rev.

Polar and hydrogen-bonding effects of alcohols on the emission spectrum of styrene-triethylamine system

The emission spectra of styrene (ST)-triethylamine (TEA) systems were measured under steady-state illumination conditions in some THF-protic solvent mixtures. The fluorescence spectrum of the ST-TEA system in THF consists of two bands (band A at 304 nm (fluorescence of ST) and band B at 460 nm (emission from an exciplex)). The intensity of band A increased and that of band B decreased with increasing amounts of protic solvents in THF-protic solvent mixtures. The increase in the intensity of band A was explained by the decrease in the concentration of free amine owing to the hydrogen-bonding interaction (or protonation) between TEA and protic solvents. The decrease in the intensity of band B was considered to be caused by the decrease in the concentration of free amine on the addition of protic solvents and the enhanced conversion of the exciplex to an ion pair with increasing solvent polarity. The polar effect was expressed as a function of the relative permittivity of the solution.</p