COMPLEXATION OF PEPTIDES WITH CROWN ETHERS .1. COMPOSITION AND THERMAL-BEHAVIOR OF COMPOUNDS CONSISTING OF OLIGOPEPTIDES AND SOME CROWN ETHERS

Crystals of the complexes 18-crown-6/diglycine, 18-crown-6/diglycine/water, 18-crown-6/triglycine, 18-crown-6/L-alpha-alanyl-L-alpha-alanine and 1,10-diaza-18-crown-6/diglycine/water were obtained. The thermal behaviour of these compounds was investigated by DSC and TGA methods. It was found that the anhydrous complexes have at least two physicochemical transitions in the range 320-470 K: melting of the complexes at 360-380 K and decomposition above 410 K. Two types of water, i.e. weakly and strongly bound with the complex, were observed on heating the hydrated complexes. The enthalpic and entropic changes of the melting process are discussed in terms of the cationic and anionic binding of the peptide molecule to crown ether.