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Fernandez-Vidal M.,University of California at Irvine | Fernandez-Vidal M.,CSIC - Institute of Chemical and Environmental Research | White S.H.,University of California at Irvine | Ladokhin A.S.,University of Kansas Medical Center
Journal of Membrane Biology

The free energy of transfer of nonpolar solutes from water to lipid bilayers is often dominated by a large negative enthalpy rather than the large positive entropy expected from the hydrophobic effect. This common observation has led to the idea that membrane partitioning is driven by the "nonclassical" hydrophobic effect. We examined this phenomenon by characterizing the partitioning of the well-studied peptide melittin using isothermal titration calorimetry (ITC) and circular dichroism (CD). We studied the temperature dependence of the entropic (-TΔS) and enthalpic (ΔH) components of free energy (ΔG) of partitioning of melittin into lipid membranes made of various mixtures of zwitterionic and anionic lipids. We found significant variations of the entropic and enthalpic components with temperature, lipid composition and vesicle size but only small changes in DG (entropy-enthalpy compensation). The heat capacity associated with partitioning had a large negative value of about -0.5 kcal mol-1 K-1. This hallmark of the hydrophobic effect was found to be independent of lipid composition. The measured heat capacity values were used to calculate the hydrophobic-effect free energy ΔGhΦ, which we found to dominate melittin partitioning regardless of lipid composition. In the case of anionic membranes, additional free energy comes from coulombic attraction, which is characterized by a small effective peptide charge due to the lack of additivity of hydrophobic and electrostatic interactions in membrane interfaces [Ladokhin and White J Mol Biol 309:543-552, 2001]. Our results suggest that there is no need for a special effect - the nonclassical hydrophobic effect - to describe partitioning into lipid bilayers. © The Author(s) 2010. Source

Ruckebusch C.,University of Lille Nord de France | Sliwa M.,University of Lille Nord de France | Pernot P.,University Paris - Sud | de Juan A.,University of Barcelona | Tauler R.,CSIC - Institute of Chemical and Environmental Research
Journal of Photochemistry and Photobiology C: Photochemistry Reviews

Nowadays, time-resolved spectroscopy data can be routinely and accurately collected in UV-vis femtosecond transient absorption spectroscopy. However, the data analysis strategy and the postulation of a physically valid model for this kind of measurements may be tackled with many different approaches ranging from pure soft-modeling (model-free) to hard-modeling, where the elaboration of a parametric spectro-temporal model may be required. This paper reviews methods that are used in practice for the analysis of femtosecond transient absorption spectroscopy data. Model-based methods, common in photochemistry, are revisited, and soft-modeling methods, which originate from the chemometrics field and that recently disseminated in the photo(bio)chemistry literature, are presented. These soft-modeling methods are designed to suit the intrinsic nature of the multivariate (or multi-way) measurement. Soft-modeling tools do not require a priori physical or mechanistic models to provide a decomposition of the data on the time and wavelength dimensions, the only requirement being that these two (or more) dimensions are separable. Additionally, Bayesian data analysis, which provides a probabilistic framework for data analysis, is considered in detail, since it allows uncertainty quantification and validation of the model selection step. © 2011 Elsevier B.V. Source

Suarez-Serrano A.,IRTA - Institute of Agricultural-Alimentary Research and Technology | Alcaraz C.,IRTA - Institute of Agricultural-Alimentary Research and Technology | Ibanez C.,IRTA - Institute of Agricultural-Alimentary Research and Technology | Trobajo R.,IRTA - Institute of Agricultural-Alimentary Research and Technology | And 2 more authors.
Ecotoxicology and Environmental Safety

In the Ebro River basin, point and diffuse pollution of heavy metals stems mainly from industry and agriculture. Bioaccumulation patterns were examined under different pollution sources (point and diffuse) using levels of heavy metals (As, Cd, Cr, Cu, Hg, Pb and Zn) in abdominal muscle tissue of Procambarus clarkii. P. clarkii captured under point source effects presented the highest concentrations of Hg, Pb and As; and were related with distance to the source of industrial waste sediments. Mean Hg levels in crayfish exposed to point sources of metals significantly exceeded legal allowed values established by the European Union legislation. In the Ebro Delta, high levels of As, Cr, Cu and Zn were associated with traditional agriculture activity (diffuse pollution) as well. These results demonstrate the potential of P. clarkii to bioaccumulate heavy metals from both point and diffuse sources and hence potentially transfer these metals to higher trophic levels. © 2009 Elsevier Inc. Source

Freire C.,University of Granada | Ramos R.,University of Granada | Lopez-Espinosa M.-J.,University of Granada | Lopez-Espinosa M.-J.,Center for Public Health Research | And 5 more authors.
Environmental Research

The main source of human exposure to mercury is the consumption of fish contaminated with methylmercury, which may adversely affect early neurodevelopment. This study assessed mercury levels in hair of preschoolers in Spain, where fish consumption is elevated, with the aim of investigating the influence of their fish intake and other factors on mercury exposure, and evaluating their association with cognitive development. A population-based birth cohort from Granada (Spain) was studied at the age of 4 yr. Total mercury (T-Hg) levels were determined in children's hair, and daily fish intake was assessed by a food frequency questionnaire. The McCarthy Scales of Children's Abilities (MSCA) were used to assess children's motor and cognitive abilities. Complete data were gathered on 72 children, and multivariate analyses were performed to evaluate the influence of mercury exposure and fish intake on MSCA outcomes. Mean concentration of T-Hg in hair was 0.96 μg/g (95% confidence interval=0.76; 1.20 μg/g). T-Hg levels were associated with higher frequency of oily fish consumption, place of residence, maternal age, and passive smoking. After adjustment for fish intake, T-Hg levels ≥1 μg/g were associated with decrements in the general cognitive (-6.6 points), memory (-8.4 points), and verbal (-7.5 points) MSCA scores. Higher mercury exposure in children from this Mediterranean area was associated with cognitive development delay. Studies on the putative benefits of fish intake during early development should consider mercury exposure from different fish species. © 2009 Elsevier Inc. All rights reserved. Source

Tauler R.,CSIC - Institute of Chemical and Environmental Research | Da Silva J.C.G.E.,University of Porto
Journal of Fluorescence

The performance of multivariate curve resolution (MCR-ALS) to decompose sets of excitation emission matrices of fluorescence (EEM) of nanocomposite materials used as analytical sensors was assessed. The two fluorescent nanocomposite materials were: NH 2-polyethylene glycol (PEG200) functionalized carbon dots, sensible to aqueous Hg(II) (CD); and, CdS quantum dots attached to the dendrimer DAB, sensible to the ionic strength of the aqueous medium (CdS-DAB). The structures of these sets of EEM, obtained as function of the Hg(II) concentration and ionic strength, are characterized by collinear properties (CD) and non-linear spectral variations (CdS-DAB). MCR-ALS was able to detect that the source of the collinearities is the presence of different size CD that show similar affinity towards Hg(II). Moreover, MCR-ALS was able to model the non-linear spectral variations of the CdS-DAB that are induced by varying ionic strength. The chemometric pre-processing of the fluorescent data sets using soft-modelling multivariate curve resolution like MCR-ALS is a critical step to transform these nanocomposites with interesting fluorescent proprieties into analytical useful nanosensors. © 2011 Springer Science+Business Media, LLC. Source

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