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A review is given of the infrared and Raman data which detect interactions of the CONH group through hydrogen bonding (solvent effects, selfassociation, internal chelations) and with ions using the vNH, Amide I, II, III bands of amides, oligopeptides and polypeptides. Examples are given whereby through vibration spectroscopy these various interactions can be related to secondary structure changes. The last part is devoted to critical remarks on tre interpretation of polypeptides and proteins spectra (170 references).

Les interactions eau-amide-sel sont etudiees, par spectrometrie de vibration, en solution quaternaire dans deux solvants organiques (CH3 CN et THF) et en melange ternaire. Les aides utilises sont le N,N-dimethylacetamide et le N-methyl-acetamide; les sels des perchlorates, des halogenures de tetra-butylammonium et le bromure de lithium. Nos resultats etablissent la fixation des anions sur les hydrogenes de l’eau et sur le groupement NH dans le cas du NMA et la fixation des cations sur le groupement carbonyle des amides meme en presence d'une grande quantite d’eau. Des doubles interactions [math] ont ete mises en evidence. Le role des anions dans la formation de ces especes est discute. Nos analyses montrent que les interactions observees avec un site du groupement peptidique le perturbent dans son ensemble. Une comparaison est proposee entre nos resultats et les phenomenes de transition de structure de polypeptides en presence d’eau et de sels.

The identification, by their infrared spectra, of species formed by specific interactions between water and three salts (LiClO4, BrNBuO4, LiBr) leads to some understanding of the microscopic structure of salt saturated aqueous solutions. The concepts “structure-maker”, “structure-breaker”, are criticised.

Les interactions eau-sel (LiBr, BrNBu4 , LiClO4 ) sont etudiees en solution diluee dans plusieurs bases organiques. L’evolution du spectre de l’acetonitrile, des vibrations du cation environne par le solvant et du spectre de libration de l’eau, lorsqu’on ajoute l’eau aux melanges sel-acetonitrile traduisent la solvatation preferentielle des sels par l’eau. Les differentes especes eau-sel formees sont caracterisees par le spectre de vibration de valence de l’eau (H2 O, D2 O, HOD), dans ces conditions. L’influence des solvants et des effets cooperatifs est discutee.

The surrounding medium may play an important role in the activity of biological macromolecules. The action of salts, among others, may modify the macromolecular conformation, such as for gelatin, lithium bromide induced mutarotation of polyproline (Ramachandran, 1967; Von Hippel, 1969), or conformational changes of polyglycine (Baron, 1973). The ion transfer through membranes takes place through antibiotic-salts interactions (Mumoz et al., 1972; Ovchinnikov and Ivanov, 1975). These biological molecules may be either polypeptide chains, as in proteins, or chains with alternate ester and peptide groups, as in depsipeptides, or cyclic ethers and methyl esters. We therefore thought it of interest to start an investigation, through infrared and Raman spectroscopy, of the interactions between some esters and amide molecules and alkaline Earths or alkaline salts. Infrared and Raman spectroscopy are well adapted for studying short life interactions, and Raman laser spectroscopy makes it possible to examine aqueous solutions. On certain points the present work cross-checks the results obtained from quantum chemistry calculations (Pullman, 1974; Perricaudet, 1973). We shall first show how the organization of carbonyl groups around the cations may be determined through infrared and Raman spectroscopy. We shall then discuss the nature of interactions between cations and these molecules.