Moisture in organic coatings - a review

A review is given on transport and equilibrium sorption of moisture in polymer films and organic coatings. Polymeric material forms the continuous phase of a coating and is therefore important for transport properties. Besides polymer, coatings consist of pigments and fillers and various additives, each of them affecting moisture transport. Firstly, in this paper typical transport and equilibrium characteristics of pure polymer films are covered, and secondly those of coatings, assimilating the impact of pigments, fillers and additives. Discrimination between Fickian and non-Fickian effects is usually based on the appearance of kinetic absorption curves. Several types of curve are dealt with, and models that describe these curves are discussed. These include two-stage sorption, sigmoidal sorption and Case II sorption. The common practice of fitting Fick’s law to kinetic data by means of relaxation parameters is criticized. Transport kinetics is modelled on the basis of kinetic plots, thereby introducing relaxation parameters in Fick’s diffusion law. Although these models describe moisture transport in polymers reasonably, these models imply a lot of curve-fitting , without a clear mechanistic foundation. Equilibrium sorption of moisture in polymeric systems is reflected by their sorption isotherms. Type II and III isotherms of the BET classification are commonly encountered, together with linear isotherms according to Henry’s law. The suitability of porous media adsorption models for polymeric systems is discussed. These models are treated in relation to interactions of water in polymers, since localized binding of water to specific groups may justify the use of these models. Finally, the — substantial — effects of pigments and fillers, as well as coating additives on moisture transport and solubility in coatings are dealt with. Pigments may lower moisture permeation, but non-ideality of pigmentation reduces this effect. Coating additives increase moisture solubility, but only little is known in detail

Lysosomal membrane permeabilization in cell death

18 páginas, 3 figuras, 2 tablas -- PAGS nros. 6434-6451Mitochondrial outer membrane permeabilization (MOMP) constitutes one of the major checkpoint(s) of apoptotic and necrotic cell death. Recently, the permeabilization of yet another organelle, the lysosome, has been shown to initiate a cell death pathway, in specific circumstances. Lysosomal membrane permeabilization (LMP) causes the release of cathepsins and other hydrolases from the lysosomal lumen to the cytosol. LMP is induced by a plethora of distinct stimuli including reactive oxygen species, lysosomotropic compounds with detergent activity, as well as some endogenous cell death effectors such as Bax. LMP is a potentially lethal event because the ectopic presence of lysosomal proteases in the cytosol causes digestion of vital proteins and the activation of additional hydrolases including caspases. This latter process is usually mediated indirectly, through a cascade in which LMP causes the proteolytic activation of Bid (which is cleaved by the two lysosomal cathepsins B and D), which then induces MOMP, resulting in cytochrome c release and apoptosome-dependent caspase activation. However, massive LMP often results in cell death without caspase activation; this cell death may adopt a subapoptotic or necrotic appearance. The regulation of LMP is perturbed in cancer cells, suggesting that specific strategies for LMP induction might lead to novel therapeutic avenuesResearch in our labs is supported by grants from Ministry of Science (BFU-2006-00508) and from Fundación La Caixa (BM06-125-1) to PB and Ligue Nationale contre le Cancer (Equipe labellisée), European Commission (Active p53, Apo-Sys, RIGHT, TransDeath, ChemoRes, DeathTrain), Agence Nationale pour la Recherche, Institut National contre le Cancer, Cancéropôle Ile-de-France and Fondation pour la Recherche Médicale to GKPeer reviewe

Unraveling new genes associated with seed development and metabolism in Bixa orellana L. by expressed sequence tag (EST) analysis.

The tropical tree Bixa orellana L. produces a range of secondary metabolites which biochemical and molecular biosynthesis basis are not well understood. In this work we have characterized a set of ESTs from a nonnormalized cDNA library of B. orellana seeds to obtain information about the main developmental and metabolic processes taking place in developing seeds and their associated genes. After sequencing a set of randomly selected clones, most of the sequences were assigned with putative functions based on similarity, GO annotations and protein domains. The most abundant transcripts encoded proteins associated with cell wall (prolyl 4-hydroxylase), fatty acid (acyl carrier protein), and hormone/flavonoid (2OG-Fe oxygenase) synthesis, germination (MADS FLClike protein) and embryo development (AP2/ERF transcription factor) regulation, photosynthesis (chlorophyll a?b binding protein), cell elongation (MAP65-1a), and stress responses (metallothionein- and thaumatin-like proteins). Enzymes were assigned to 16 different metabolic pathways related to both primary and secondary metabolisms. Characterization of two candidate genes of the bixin biosynthetic pathway, BoCCD and BoOMT, showed that they belong, respectively, to the carotenoid-cleavage dioxygenase 4 (CCD4) and caffeic acid O-methyltransferase (COMT) families, and are up-regulated during seed development. It indicates their involvement in the synthesis of this commercially important carotenoid pigment in seeds of B. orellana. Most of the genes identified here are the first representatives of their gene families in B. orellana.On line first, with supplementary material