21 research outputs found
Développement de systèmes polymère-(poly)peptide en vue de l'immobilisation de vésicules lipidiques
Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal
Alkaloids in Marine Algae
This paper presents the alkaloids found in green, brown and red marine algae. Algal chemistry has interested many researchers in order to develop new drugs, as algae include compounds with functional groups which are characteristic from this particular source. Among these compounds, alkaloids present special interest because of their pharmacological activities. Alkaloid chemistry has been widely studied in terrestrial plants, but the number of studies in algae is insignificant. In this review, a detailed account of macro algae alkaloids with their structure and pharmacological activities is presented. The alkaloids found in marine algae may be divided into three groups: 1. Phenylethylamine alkaloids, 2. Indole and halogenated indole alkaloids, 3. Other alkaloids
Spectroscopie vibrationnelle d’assemblages biomoléculaires. Comprendre les processus de formation, d’interaction et de détection
The elucidation of the relationship between structure and property within biomaterials is still a challenge. The first part of this work deals with the physico-chemical characterization of a particular fibrous protein, silk, in order to improve our understanding of its mechanical behavior. Vibrational spectroscopy under uniaxial traction has allowed us to follow the behavior of the main chemical groups involved as well as the conformational changes. Spectroscopic techniques have also been used to characterize organo-mineral materials within mollusks, to improve our knowledge of these organic and mineral matrix. The behavior within lipidic assemblies, a large family of biomolecules of interest, has been investigated to elucidate the impermeability properties of stratum corneum via the formation of crystalline lipidic domains surrounded by a more fluid matrix. This knowledge has been used for various applications: optimization of chitin extraction, vectorization, design of polymer/peptide hybrid systems for lipid vesicle immobilization. The current projects exploit the exceptional sensitivity of Surface Exalted Raman Spectroscopy (SERS), in addition to the vibrational spectroscopies used. This sensitivity enables the detection of traces of organic molecules, which is of interest in the field of prebiotic chemistry, pollution but also in the field of color chemistry, and heritage materials. The studies carried out will be used for analytical purposes, but also with a more fundamental perspective of understanding the phenomenon of exaltation in SERS, via theoretical calculations, as well as super-resolution imaging. Measurement procedures will be tuned to the particular objects studied in these contexts and a silk-based pollutant sensor will be designed. Ways to improve the sensitivity of SERS will be explored, via the preparation of new metal substrates efficient at both ends of the electromagnetic spectrum, also exhibiting catalytic properties.La compréhension des relations structure – propriété au sein des biomatériaux est toujours un objectif. La première partie de ce travail porte sur la caractérisation physico-chimique d’une protéine fibreuse particulière, la soie, dans le but d’améliorer notre compréhension de son comportement mécanique. La spectroscopie vibrationnelle sous traction uni axiale a permis de suivre le comportement des principaux groupements chimiques sollicités. Les techniques spectroscopiques ont aussi été mises à profit pour caractériser l’organisation au sein de matériaux organo-minéraux chez les mollusques, pour améliorer notre connaissance de ces matériaux. L’organisation au sein d’assemblage lipidique, une grande famille de biomolécules, a été investigué pour élucider les propriétés d’imperméabilité du stratum corneum via la formation de domaines cristallins entourés de plus fluide. Ces connaissances ont été mises à profit pour diverses applications : l’optimisation de l’extraction de la chitine, la vectorisation, la conception de systèmes hybrides polymère / peptides pour l’immobilisation de vésicules lipidiques. Les projets en cours exploitent la sensibilité exceptionnelle de la spectroscopie Raman exaltée de surface (SERS), en complément aux spectroscopies vibrationnelles utilisées. Cette sensibilité est mise à profit afin de développer la détection de traces de molécules organiques, mesures qui présente un intérêt dans le domaine de la chimie prébiotique, de la pollution mais aussi dans le domaine de la couleur, et des matériaux du patrimoine. Les études menées seront mises à profit dans un but analytique, mais aussi avec une perspective plus fondamentale de compréhension du phénomène d’exaltation en spectroscopie SERS, à travers la détection de l’adénine via l’utilisation de calculs théoriques, ainsi que l’imagerie de super-résolution. Les procédures de mesures seront adpatées aux objets particuliers étudiés dans ces contextes et un capteur de polluant à base de soie sera conçu. Des voies d’amélioration de la sensibilité du SERS seront explorées, via la préparation de nouveaux substrats métalliques efficaces aux deux extrémités du spectre électromagnétique, présentant aussi des propriétés catalytiques
Micro-Mechanics of Fresh and 30-year-old Nephila Inaurata Madagascariensis Dragline Silk
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Comparison of embryonic and adult shells of Sepia officinalis (Cephalopoda, Mollusca)
International audienceDevelopment and evolution of the shell in cephalopods is difficult to establish as there is few species with a calcified shell that could be fossilized (stable in geological time). Internal cuttlebone of sepiids is so particular that homologies are difficult to find. The developmental sequence in embryos give some response elements by comparison with adult cuttlebone. The macro and microstructure of adult shell is well known but an approach at nanostructural level allows to determine structure and composition of the two main parts, the dorsal shield and chambered part. We evidence in the embryonic shell, mainly organic, a light calcification of the shell, which occurs directly as aragonite, as it is all along the formation of the shell and whatever the parts. In embryonic shell, the prismatic and/or lamellar layers, present in adult, are not differentiated and the dorsal shield grows progressively, from posterior to anterior. Despite microstructural differences, all layers of both chambered part and dorsal shield are composed of rounded nanogranules (between 50 and 100 nm), similar to what is found in other mollusc shells
On-site contactless surface analysis of Modern paintings from Galleria Nazionale (Rome) by Reflectance FTIR and Raman spectroscopies
International audienceSeven artworks representing the diversity of paints used around the 1960s and created by German and Italian painters (J. Albers, A. Bonalumi, L. Boille, T. Scialoja and M. Schifano) were studied on-site at the Galleria Nazionale d'Arte Moderna (Rome) with mobile instruments. We present a methodology based on Specular Reflectance Infrared Spectroscopy (SR-FTIR) adapted to unvarnished paintings. Complementary measurements have been performed by Raman spectroscopy. Characteristic bands regarding as-recorded infrared reflectance spectra and Kramers-Kronig Transformation-converted absorbance spectra are identified according to literature and reference spectra recorded on representative commercially available paints. To distinguish the different binders by SR-FTIR, we propose spectroscopic markers as the comparison of the intensity of carbonyl band around 1730-1735 cm−1 with bands at ~1160 (for acrylic), ~1230 (for PVAc), and 1270 cm−1 (for alkyds). On the other hand, oil/resin binders are characterized by intense and thin νCH2, νCH3 IR absorption bands around 2920-2850 cm−1, combined with an intense 1260 cm−1 band and a characteristic concave cradle shape (between ca. 1750 and 1260 cm−1). The results obtained establish the relevance of the implemented mobile non-invasive infrared spectroscopy analytical approach by successfully identifying acrylic, vinylic, oil media and enamel paints, with or without opacifiers, which is supplemented by Raman analyses for pigment identification.HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés
High-resolution structural and elemental analyses of calcium storage structures synthesized by the noble crayfish Astacus astacus
International audienceDuring premolt, crayfish develop deposits of calcium ions, called gastroliths, in their stomach wall. The stored calcium is used for the calcification of parts of the skeleton regularly renewed for allowing growth. Structural and molecular analyses of gastroliths have been primarily performed on three crayfish species, Orconectes virilis, Procambarus clarkii, and more recently, Cherax quadricarinatus. We have performed high-resolution analyses of gastroliths from the native noble crayfish, Astacus astacus, focusing on the microstructure, the mineralogical and elemental composition and distribution in a comparative perspective. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) observations showed a classical layered microstructure composed of 200-nm diameter granules aligned along fibers. These granules are themselves composed of agglomerated nanogranules of 50 nm-mean diameters. Denser regions of bigger fused granules are also present. Micro-Raman spectroscopy show that if A. astacus gastroliths, similarly to the other analyzed gastroliths, are mainly composed of amorphous calcium carbonate (ACC), they are also rich in amorphous calcium phosphate (ACP). The presence of a carotenoid pigment is also observed in A. astacus gastrolith contrary to C. quadricarinatus. Energy-dispersive X-ray spectroscopy (EDX) analyses demonstrate the presence of minor elements such as Mg, Sr, Si and P. The distribution of this last element is particularly heterogeneous. X-ray absorption near edge structure spectroscopy (XANES) reveals an alternation of layers more or less rich in phosphorus evidenced in the mineral phase as well as in the organic matrix in different molecular forms. Putative functions of the different P-comprising molecules are discussed
beta-Phenylethylamine content in marine algae around Turkish coasts
WOS: 000263932500011beta-Phenylethylamine content was investigated in two green, five brown, and ten red marine algae by gas chromatography/mass spectrometry. beta-Phenylethylamine was found in six red algae but was not detected in the brown and green algae studied. The highest amount of beta-phenylethylamine was determined in Gelidium crinale (30.42 mu g g(-1)). This is the first report of beta-phenylethylamine in the algae tested and also the first to quantify beta-phenylethylamine in marine algae
Loliolide in marine algae
WOS: 000264337800009PubMed ID: 19296390Loliolide content was determined in 13 marine algae including red, brown and green algae collected from the Black Sea, the Dardanelles and the Aegean Sea. Identification and quantification were performed by gas chromatography-mass spectrometry. The loliolide content in green alga is 1.76 g g-1, ranges from 0.14 to 4.35 g g-1 in red and from 0.18 to 4.83 g g-1 in brown algae. The results obtained are in the same range as previously reported for algae, as well as terrestrial plants. This article represents the first report of loliolide occurrence in green algae