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The main objective of our research program is the study of the conformation and orientation of natural and synthetic macromolecules by infrared and Raman spectroscopy. The goals of these studies is to establish the close relationships that exist between the structure of these macromolecules and their functions and properties. Vibrational spectroscopy is particularly well suited for such investigations since each band in the spectra represents an intrinsic probe of a particular region of a molecule. In addition, the orientation of the macromolecules in organized systems such as monolayer films and oriented polymer samples is readily determined by polarization measurements. Natural macromolecules and oriented polymers are currently investigated in our laboratory.
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Our work on natural macromolecules involves proteins and biological membranes. In order to better understand membrane mechanisms and functions, the interaction between proteins and lipids in model membrane systems composed of either vesicles or oriented films of phospholipids and small lipid-interacting proteins or peptides is investigated. Most of our efforts on membranes involve the use of monolayer films transferred on solid substrates (Langmuir-Blodgett films) or studied in situ at the air-water interface by polarization modulation reflection absorption spectroscopy (PM-IRRAS). The conformation of proteins and polypeptides is also investigated by two-dimensional infrared (2D-IR) spectroscopy and at the air-water interface.
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Several properties of polymers are modulated by the molecular orientation in these materials. Vibrational spectroscopy is particularly well suited to study polymer orientation since it allows the determination at the molecular level of the orientation of the different components of multicomponent systems such as polymer blends, copolymers and semi-crystalline polymers. In addition to orientation determination by static measurements of the infrared linear dichroism, we use polarization modulation infrared linear dichroism (PM-IRLD) to follow the dynamics of orientation following either tensile deformation or photoisomerization in the case of polymers containing azobenzene side chains. These experiments are carried out by PM-IRLD and 2D-IR spectroscopy using both continuous and step-scan FTIR spectroscopy.
Description of research grants
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