Direct Observation of Millisecond to Second Motions in Proteins by Dipolar CODEX NMR Spectroscopy

We present a site-resolved study of stow (ms to s) motions in a protein in the solid (microcrystalline) state performed with the use of a modified version of the centerband-only detection of exchange (CODEX) NMR experiment. CODEX was originally based on measuring changes in molecular orientation by means of the chemical shift anisotropy (CSA) tensor, and in our modification, angular reorientations of internuclear vectors are observed. The experiment was applied to the study of stow (15)N-(1)H motions of the SH3 domain of chicken a-spectrin. The protein was perdeuterated with partial back-exchange of protons at labile sites. This allowed indirect (proton) detection of (15)N nuclei and thus a significant enhancement of sensitivity. The diluted proton system also made negligible proton-driven spin diffusion between (15)N nuclei, which interferes with the molecular exchange (motion) and hampers the acquisition of dynamic parameters. The experiment has shown that approximately half of the peaks in the 2D (15)N-(1)H correlation spectrum exhibit exchange in a different extent. The correlation time of the slow motion for most peaks is 1 to 3 s. This is the first NMR study of the internal dynamics of proteins in the solid state on the millisecond to second time scale with site-specific spectral resolution that provides both time-scale and geometry information about molecular motions.

Fast and reliable analyses of sulphite in fruit juices using a supramolecular amperometric detector encompassing in flow gas diffusion unit

A new compact system encompassing in flow gas diffusion unit and a wall-jet amperometric FIA detector, coated with a supramolecular porphyrin film, was specially designed as an alternative to the time-consuming Monier-Williams method, allowing fast, reproducible and accurate analyses of free sulphite species in fruit juices. In fact, a linear response between 0.64 and 6.4 ppm of sodium sulphite. LOD = 0.043 ppm, relative standard deviation of +/- 1.5% (n = 10) and analytical frequency of 85 analyses/h were obtained utilising optimised conditions. That superior analytical performance allows the precise evaluation of the amount of free sulphite present in foods, providing an important comparison between the standard addition and the standard injection methods. Although the first one is most frequently used, it was strongly influenced by matrix effects because of the unexpected reactivity of sulphite ions with the juice matrixes, leading to its partial consumption soon after addition. In contrast, the last method was not susceptible to matrix effects yielding accurate results, being more reliable for analytical purposes. (C) 2011 Elsevier Ltd. All rights reserved.

Intrachain Energy Migration to Weak Charge-Transfer State in Polyfluorene End-Capped with Naphthalimide Derivative

Polyfluorene end-capped with N-(2-benzothiazole)-1 8-naphthalimide (PF-BNI) is a highly fluorescent material with fluorescence emission modulated by solvent polarity Its low energy excited state is assigned as a mixed configuration state between the singlet S(1) of the fluorene backbone (F) with the charge transfer (CI) of the end group BNI The triexponential fluorescence decays of PF-BNI were associated with fast energy migration to form an intrachain charge-transfer (ICCT) state polyfluorene backbone decay and ICCT deactivation Time-resolved fluorescence anisotropy exhibited biexponential relaxation with a fast component of 12-16 ps in addition to a slow one in the range 0 8-1 4 ns depending on the solvent showing that depolarization occurs from two different processes energy migration to form the ICCT state and slow rotational diffusion motion of end segments at a longer time Results from femtosecond transient absorption measurements agreed with anisotropy decay and showed a decay component of about 16 ps at 605 nm in PF BNI ascribed to the conversion of S(1) to the ICCT excited state From the ratio of asymptotic and initial amplitudes of the transient absorption measurement the efficiency of intrachain ICCT formation is estimated in 0 5 which means that on average, half of the excited state formed in a BNI-(F)(n)-BNI chain with n = 32 is converted to its low energy intrachain charge-transfer (ICCT) state

Nuclear magnetic resonance water relaxation time changes in bananas during ripening: a new mechanism

BACKGROUND: Nuclear magnetic resonance studies of banana fragments during ripening show an increase on the water transverse relaxation time (T(2)) and a decrease in water self-diffusion coefficient (D). As T(2) and D are normally directly correlated, we studied these two properties in intact bananas during ripening, in an attempt to rule out the effect of injury on the apparent discrepancies in the behavior of T(2) and D. RESULTS: The results show that injury in bananas causes a decrease in T(2) of the water in vacuoles (T(2vac)). They also show that T(2vac) increased and D decreased during ripening, ruling out the injury effect. To explain the apparent discrepancies, we propose a new hypothesis for the increase in T(2) values, based on the reduction of Fe(3+) ions to Fe(2+) by galacturonic acid, produced by the hydrolysis of pectin and a decrease in internal oxygen concentration during ripening. CONCLUSION: As injury alters T(2) values it is necessary to use intact bananas to study relaxation times during ripening. The novel interpretation for the increase in T(2vac) based on reduction of Fe(+3) and O(2) concentration is an alternative mechanism to that based on the hydrolysis of starch in amyloplasts. (C) 2010 Society of Chemical Industry

On the statistical estimation of diffusion processes: a survey

Data available on continuos-time diffusions are always sampled discretely in time. In most cases, the likelihood function of the observations is not directly computable. This survey covers a sample of the statistical methods that have been developed to solve this problem. We concentrate on some recent contributions to the literature based on three di§erent approaches to the problem: an improvement of the Euler-Maruyama discretization scheme, the use of Martingale Estimating Functions and the application of Generalized Method of Moments (GMM).

On the statistical estimation of diffusion processes - a partial survey

Data available on continuous-time diffusions are always sampled discretely in time. In most cases, the likelihood function of the observations is not directly computable. This survey covers a sample of the statistical methods that have been developed to solve this problem. We concentrate on some recent contributions to the literature based on three di§erent approaches to the problem: an improvement of the Euler-Maruyama discretization scheme, the employment of Martingale Estimating Functions, and the application of Generalized Method of Moments (GMM).

How the full opening of the capital account to highly liquid financial markets led Latin America to two and a half cycles of ‘mania, panic and crash’

Latin America has recently experienced three cycles of capital inflows, the first two ending in major financial crises. The first took place between 1973 and the 1982 ‘debt-crisis’. The second took place between the 1989 ‘Brady bonds’ agreement (and the beginning of the economic reforms and financial liberalisation that followed) and the Argentinian 2001/2002 crisis, and ended up with four major crises (as well as the 1997 one in East Asia) — Mexico (1994), Brazil (1999), and two in Argentina (1995 and 2001/2). Finally, the third inflow-cycle began in 2003 as soon as international financial markets felt reassured by the surprisingly neo-liberal orientation of President Lula’s government; this cycle intensified in 2004 with the beginning of a (purely speculative) commodity price-boom, and actually strengthened after a brief interlude following the 2008 global financial crash — and at the time of writing (mid-2011) this cycle is still unfolding, although already showing considerable signs of distress. The main aim of this paper is to analyse the financial crises resulting from this second cycle (both in LA and in East Asia) from the perspective of Keynesian/ Minskyian/ Kindlebergian financial economics. I will attempt to show that no matter how diversely these newly financially liberalised Developing Countries tried to deal with the absorption problem created by the subsequent surges of inflow (and they did follow different routes), they invariably ended up in a major crisis. As a result (and despite the insistence of mainstream analysis), these financial crises took place mostly due to factors that were intrinsic (or inherent) to the workings of over-liquid and under-regulated financial markets — and as such, they were both fully deserved and fairly predictable. Furthermore, these crises point not just to major market failures, but to a systemic market failure: evidence suggests that these crises were the spontaneous outcome of actions by utility-maximising agents, freely operating in friendly (‘light-touch’) regulated, over-liquid financial markets. That is, these crises are clear examples that financial markets can be driven by buyers who take little notice of underlying values — i.e., by investors who have incentives to interpret information in a biased fashion in a systematic way. Thus, ‘fat tails’ also occurred because under these circumstances there is a high likelihood of self-made disastrous events. In other words, markets are not always right — indeed, in the case of financial markets they can be seriously wrong as a whole. Also, as the recent collapse of ‘MF Global’ indicates, the capacity of ‘utility-maximising’ agents operating in (excessively) ‘friendly-regulated’ and over-liquid financial market to learn from previous mistakes seems rather limited.

How the full opening of the capital account to highly liquid financial markets led Latin America to two and a half cycles of ‘mania, panic and crash’

Latin America has recently experienced three cycles of capital inflows, the first two ending in major financial crises. The first took place between 1973 and the 1982 ‘debt-crisis’. The second took place between the 1989 ‘Brady bonds’ agreement (and the beginning of the economic reforms and financial liberalisation that followed) and the Argentinian 2001/2002 crisis, and ended up with four major crises (as well as the 1997 one in East Asia) — Mexico (1994), Brazil (1999), and two in Argentina (1995 and 2001/2). Finally, the third inflow-cycle began in 2003 as soon as international financial markets felt reassured by the surprisingly neo-liberal orientation of President Lula’s government; this cycle intensified in 2004 with the beginning of a (purely speculative) commodity price-boom, and actually strengthened after a brief interlude following the 2008 global financial crash — and at the time of writing (mid-2011) this cycle is still unfolding, although already showing considerable signs of distress. The main aim of this paper is to analyse the financial crises resulting from this second cycle (both in LA and in East Asia) from the perspective of Keynesian/ Minskyian/ Kindlebergian financial economics. I will attempt to show that no matter how diversely these newly financially liberalised Developing Countries tried to deal with the absorption problem created by the subsequent surges of inflow (and they did follow different routes), they invariably ended up in a major crisis. As a result (and despite the insistence of mainstream analysis), these financial crises took place mostly due to factors that were intrinsic (or inherent) to the workings of over-liquid and under-regulated financial markets — and as such, they were both fully deserved and fairly predictable. Furthermore, these crises point not just to major market failures, but to a systemic market failure: evidence suggests that these crises were the spontaneous outcome of actions by utility-maximising agents, freely operating in friendly (light-touched) regulated, over-liquid financial markets. That is, these crises are clear examples that financial markets can be driven by buyers who take little notice of underlying values — investors have incentives to interpret information in a biased fashion in a systematic way. ‘Fat tails’ also occurred because under these circumstances there is a high likelihood of self-made disastrous events. In other words, markets are not always right — indeed, in the case of financial markets they can be seriously wrong as a whole. Also, as the recent collapse of ‘MF Global’ indicates, the capacity of ‘utility-maximising’ agents operating in unregulated and over-liquid financial market to learn from previous mistakes seems rather limited.

In situ differentiation of labile/inert metal species in Brazilian tropical rivers by means of a time-controlled batch-procedure based on TEPHA resin

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

The Predation of Artemia Nauplii by the Larvae of the Amazon River Prawn, Macrobrachium amazonicum (Heller, 1862), is Affected by Prey Density, Time of Day, and Ontogenetic Development

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Construtivismo de marco teórico-pedagógico a grife: um estudo a partir das mensagens veiculadas na internet

This thesis is resulted of a research on propagated the social representations of constructivism in the Internet, which as had estimated basic the idea of Moscovici (1961) of that the media it has determinative paper in the popularization of the scientific theories, in formation e propagation of the social representations and in the construction of behaviors human beings. Understanding the Internet as latest space of circulation of social communications, therefore, privileged field (and still not explored) for studies of social representations, we choose this half midiático as investigative field of our research, it if it constitutes in the "great ocean of the new informational planet" (LEVY, 2000, p. 126), besides making possible the interaction with different forms of images, different individuals, different ' world ', configuring itself as important space of symbolic production e of analysis of the representational process in the world contemporary. Based in these questions, we trace as objective to analyze the circulating speech propagated on-line on the constructivism, searching to apprehend the social representations shared the respect. This objective was constructed in face of the insertion of the theory constructivist in the educational way has two decades more than, as well as of its consolidation as reference in different social contexts, mainly in midiático. The question that directed the research was: as this theory obtains to penetrate in some layers of our society, to influence the world readings e the behaviors of different people? That modifications it suffers in this trajectory and which the paper of the Internet in this process? The corpus of the research was constituted of the substances on the theory found in the Internet, in pages in Portuguese of Google, in the period of 27 of July of 2004 the 17 of August of 2004. The data they had been analyzed on the basis of the project of analysis of content elaborated for Moscovici (1961) and in the estimated theoreticians of the social communication, in special of the hypermedia. The results had disclosed that the Internet participates of determinative form in the process of popularization of the constructivism theory, not only spreading out its estimated theoretician- methodological for the domain public (diffusion), but propagating positive beliefs and images of its postulates (propagation) and using them it service of interests politicians e financiers (propaganda). The popularization of the constructivism in the Internet and social representations of this theory propagated configure one process in which the theory passes of pedagogical theoretical landmark for grief, assuming a commercial character extremely and the status of solution for problems of the education and the society, stirring up attitudes and behaviors in public, most general possible, that comes to take care of to the interests politicians e marketing. Recognizing the diversity, the permanent renewal of information and the negotiation of directions gifts in the Internet, as well as the innumerable ones forms of access to the information found by it, we consider results of the research as fruits of the inherent characteristics to this way midiático, to the time where we call the attention for relativity these results, for the plasticity of knowing them and sensible propagated on-line e for the great challenge that the hypermedia imposes to the study of communication phenomena, of the social representations and in educational quarrels and for the necessity of new research that they investigate the forms of socialization of the information and communication propitiated by hypermedia and its implications in the construction of the symbolic universes and in practical social

Determination of the oxygen and nitrogen interstitial diffusion coeficient in niobium by mechanical spectroscopy

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

Best site for embryo transfer: the upper or lower half of endometrial cavity?

BACKGROUND: the objective of the present study was to determine the importance of the site of embryo transfer (upper or lower half endometrial cavity) on implantation and clinical pregnancy rates. METHODS: A total of 400 transfers guided by ultrasound were randomly assigned to two groups according to the distance between the uterine fundus and the catheter tip at the time of embryo placement. Group I (n=200) consisted of transfers corresponding to a distance of <50% of the endometrial cavity length (ECL), i.e. transfer in upper half of the cavity; and group II (n=200) consisted of transfers corresponding to a distance of greater than or equal to50%, of the ECL, i.e. transfer in lower half of cavity. The Student's t-test, Mann-Whitney test and Fisher's exact test were used where appropriate. RESULTS: the general characteristics of the study population and the main transfer cycle characteristics had an equal distribution (P>0.05) between groups I and II. No significant difference in implantation or pregnancy rates was observed between groups I and II. CONCLUSION: the implantation or pregnancy rates were similar whether the embryos were deposited in the upper or lower half of the endometrial cavity.

Effective diffusion coefficients behavior in osmotic dehydration of apple slices considering shrinking and local concentration dependence

The mass transfer during osmotic dehydration of apple slices immersed in 40, 50 and 60% (w/w) aqueous sucrose solutions was investigated to evaluate the influence of solution concentration on diffusivities. In the mathematical model, the diffusion coefficients were functions of the local water and sucrose concentration. The mass transfer equations were, simultaneously, solved for water and sucrose using an implicit numerical method. Material coordinates following the shrinkage of the solid were used. The predicted concentration profiles were integrated and compared to experimental data, showing a reasonable agreement with the measured data. on average, the effective diffusion coefficients for water and sucrose decreased as the osmotic solution concentration increased; that is the behavior of the binary coefficients in water-sucrose solutions. However, the diffusivities expressed as a function of the local concentration in the slices varied between the treatments. Water diffusion coefficients showed a remarkable variation throughout the slice and unusual behavior, which was associated to the cellular structure changes observed in tissue immersed in osmotic solutions. Cell structure changes occurred in different ways: moderate plasmolysis at 40%, accentuated plasmolysis at 50% and generalized damage of the cells at 60%. Intact vacuoles were observed after a long time of exposure (30 h) to 40 and 50% solutions. Effects of the concentration on tissue changes make it difficult to generalize the behavior of diffusion coefficients.

Configuration-dependent diffusion can shift the kinetic transition state and barrier height of protein folding

We show that diffusion can play an important role in protein-folding kinetics. We explicitly calculate the diffusion coefficient of protein folding in a lattice model. We found that diffusion typically is configuration- or reaction coordinate-dependent. The diffusion coefficient is found to be decreasing with respect to the progression of folding toward the native state, which is caused by the collapse to a compact state constraining the configurational space for exploration. The configuration- or position-dependent diffusion coefficient has a significant contribution to the kinetics in addition to the thermodynamic free-energy barrier. It effectively changes (increases in this case) the kinetic barrier height as well as the position of the corresponding transition state and therefore modifies the folding kinetic rates as well as the kinetic routes. The resulting folding time, by considering both kinetic diffusion and the thermodynamic folding free-energy profile, thus is slower than the estimation from the thermodynamic free-energy barrier with constant diffusion but is consistent with the results from kinetic simulations. The configuration- or coordinate-dependent diffusion is especially important with respect to fast folding, when there is a small or no free-energy barrier and kinetics is controlled by diffusion. Including the configurational dependence will challenge the transition state theory of protein folding. The classical transition state theory will have to be modified to be consistent. The more detailed folding mechanistic studies involving phi value analysis based on the classical transition state theory also will have to be modified quantitatively.