Clam shell repair from the brown ring disease: a study of the organic matrix using Confocal Raman micro-spectrometry and WDS microprobe

Since 1987, the Manila clam Ruditapes philippinarum has been regularly affected by the brown ring disease (BRD), an epizootic caused by the bacterium Vibrio tapetis. This disease is characterized by the development of a brown deposit on the inner face of valves. While most of the clams die from the BRD infection, some of them are able to recover by mineralizing a new repair shell layer, which covers the brown deposit by a process of encapsulation. The purpose of this work was to study the organic matrix of the shells of Manila clams in the inner shell layer before, during and after the brown deposit and during the shell repair process by confocal Raman micro-spectrometry and wavelength dispersive spectrometry (WDS) microprobe. In addition, the organic matrix of the repaired shell layer was extracted and quantified, by using standard biochemical shell matrix extractions protocols. The brown deposit exhibited high luminescence intensity in Raman spectra, and an increase of S, C, Sr (forming two peaks) and a decrease of Ca, Na concentrations (% w/w), using WDS microprobe mapping and cross-sectional transects. The signature of these trace elements was similar to that recorded on periostracal lamina (% w/w). The high S concentration likely corresponds to the presence of a high amount of sulfated organic compounds. Interestingly, on cross-sectional transects, before the brown deposit, a thin layer of the shell showed also a high luminescence, which may suggest that this layer is modified by bacteria. After the brown deposit, at the beginning of the shell repair process, the luminescence and the S concentration remain high, before declining the level found in non-BRD-affected shells. Quantification of the organic matrix shows that the shell repair layer zone is significantly different from non-BRD-affected shell layer, in particular with a much higher amount of insoluble matrix.     

Hydrogel Films Based on Chitosan and Oxidized Carboxymethylcellulose Optimized for the Controlled Release of Curcumin with Applications in Treating Dermatological Conditions

Cross-linked chitosan (CS) films with aldehyde groups obtained by oxidation of carboxymethyl cellulose (CMC) with NaIO₄ were prepared using different molar ratios between the CHO groups from oxidized carboxymethyl cellulose (CMCOx) and NH₂ groups from CS (from 0.25:1 to 2:1). Fourier-transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy demonstrated the aldehyde groups’ presence in the CMCOx. The maximum oxidation degree was 22.9%. In the hydrogel, the amino groups’ conversion index value increased when the -CHO/-NH₂ molar ratio, cross-linking temperature, and time increased, while the swelling degree values decreased. The hydrogel films were characterized by scanning electron microscopy (SEM) and FTIR analysis. The curcumin encapsulation efficiency decreases from 56.74% to 16.88% when the cross-linking degree increases. The immobilized curcumin release efficiency (R_Ef%) and skin membrane permeability were evaluated in vitro in two different pH solutions using a Franz diffusion cell, and it was found to decrease when the molar ratio -CH=O/NH₂ increases. The curcumin R_Ef% in the receptor compartment was higher at pH = 7.4 (18%- for the sample with a molar ratio of 0.25:1) than at pH = 5.5 (16.5%). The curcumin absorption in the skin membrane at pH = 5.5 (47%) was more intense than at pH = 7.4 (8.6%). The curcumin-loaded films’ antioxidant activity was improved due to the CS presence.     

Effect of Bulk and Interfacial Rheological Properties on Bubble Dissolution

This paper describes theoretical calculations of the combined effect of bulk and interfacial rheological properties on dissolution behavior of a bubble in an infinite medium at saturated conditions. Either bulk or interfacial elasticity can stop the bubble dissolution process, and stability criteria are defined for the elastic cases. In the case of an elastic interface with dilation modulus E(d) and a bubble with an initial radius R(0) and initial interfacial tension sigma(0), the bubble is stabilized as it has shrunk to a relative radius of varepsilon=R/R(0)=exp(-sigma(0)/2E(d))). In case of an elastic bulk with modulus G a bubble will shrink until GR(0)=4sigma(0)varepsilon(3)/(1-5varepsilon(4)+4varepsilon(3)) is fulfilled. Bulk and interfacial viscosity can retard the dissolution process if their magnitude exceeds a certain critical value but will never completely stop bubble dissolution. Copyright 2001 Academic Press.     

Modelling of the binding site of the human m1 muscarinic receptor: Experimental validation and refinement

Our model of the human m1 muscarinic receptor has been refined on the basis of the recently published projection map of bovine rhodopsin. The refined model has a slightly different helix arrangement, which reveals the presence of an extra hydrophobic pocket located between helices 3, 4 and 5. The interaction of series of agonists and antagonists with the m1 muscarinic receptor has been studied experimentally by site-directed mutagenesis. In order to account for the observed results, three-dimensional models of m1 ligands docked in the target receptor are proposed. Qualitatively, the obtained models are in good agreement with the experimental observations. Agonists and partial agonists have a relatively small size. They can bind to the same region of the receptor using, however, different anchoring receptor residues. Antagonists are usually larger molecules, filling almost completely the same pocket as agonists. They can usually produce much stronger interactions with aromatic residues. Experimental data combined with molecular modelling studies highlight how subtle and diverse receptor–ligand interactions could be.     

Homolytic versus Heterolytic Dissociation of Alkalimetal Halides: The Effect of Microsolvation

Herein we report density functional calculations of homolytic and heterolytic dissociation energies of the diatomic alkalimetal halides MX (M=Li, Na, K, Rb, and Cs and X=F, Cl, Br, I, and At) and their corresponding microsolvated structures MX?(H₂O)_n (n=1 to 4). Our results show that the homolytic dissociation energy of the MX?(H₂O)_n species increases with the number of water molecules involved in the microsolvated salts. On the other hand, the heterolytic dissociation energy follows exactly the opposite trend. As a result, while for the isolated diatomic alkalimetal halides, homolytic dissociation is always favored over heterolytic dissociation, the latter is preferred for CsF and CsCl already for n=2, and for n=4 it is the preferential mode of dissociation for more than half of the species studied.     

Quiver representations of maximal rank type and an application to representations of a quiver with three vertices

We introduce the notion of ‘maximal rank type’ forrepresentations of quivers, which requires certain collectionsof maps involved in the representation to be of maximal rank.We show that real root representations of quivers are of maximalrank type. By using the maximal rank type property and universalextension functors we construct all real root representationsof a particular wild quiver with three vertices. From this constructionit follows that real root representations of this quiver aretree modules. Moreover, formulae given by Ringel can be appliedto compute the dimension of the endomorphism ring of a givenreal root representation.     

Determination of Volatile Chemical Constitutes in Tea by Simultaneous Distillation Extraction, Vacuum Hydrodistillation and Thermal Desorption

Generally the volatile compounds of tea are quite complicated and are found at trace levels (around 0.1% in total). The top-note of tea usually contains 40–100 main ingredients and is an analytical challenge to obtain qualitative and quantitative information of these volatile constitutes. The objective of this work is to apply the most suitable methods such as simultaneous distillation extraction, vacuum hydrodistillation extraction and direct thermal desorption to accurately determine the chemical components of a top-brand Chinese green tea and to compare the three volatile extraction methods. The analytical results are double confirmed by GC-sniffing, authentic raw materials and internal expert evaluation by reconstituting the top-note profile of the analyzed tea.     

Surface-modified magnetic colloids for affinity adsorption of immunoglobulins

This work describes the preparation, characterization and in vitro adsorption tests of surface-modified magnetoliposomes for affinity binding of (i) anticardiolipin (isotype G) antibodies and (ii) specific isotype E antibodies generated by hypersensitivity reactions in humans with respiratory allergy. In the first case, cardiolipin embedded in the bilayer of magnetoliposomes was used as specific ligand. In the second case, antigenic proteins present in an extract of Dermatophagoids pteronyssinus and Blomia tropicalis mites were covalently coupled on the surface of magnetoliposomes via a diglycolic spacer arm, and used as specific ligands for IgE. Antibody adsorption was performed in a high-gradient magnetophoresis system, using either sera of healthy individuals or a pool of sera from autoimmune or allergic patients. The selectivity and capacity of the system were quantified by a frontal analysis in a capillary column, and by constructing breakthrough curves. The results show that the highest yield and selectivity were obtained if the ligand was extended into the aqueous layer surrounding the magnetoliposome surface. A 100% selectivity was obtained for adsorption of specific IgE, and 8% for IgG. These results demonstrate the potentialities of both types of surface-modified magnetic biocolloids in the field of in vitro diagnosis tests for allergic or autoimmune conditions.