LIPOENKEPHALINS: A STUDY OF THE SURFACE ACTIVE AND PHARMACOLOGICAL PROPERTIES OF THESE NEW MORPHINE-LIKE PEPTIDES?

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Abstract
By modifying the physicochemical character of naturally occurring enkephalines, a parallelism between physicochemical behavior and pharmacological activity has been found. This was achieved by introducing alkyl residues of different chain length in position 1 or 5 on the enkephalin sequence. These kinds of substances can be referred to as 1ipoenkephalins and from a physicochemical point of view can be considered as surface active agents. On the other hand, as biological activity is greatly dependent on the conformation or orientation adopted by the molecule, we have also tried to investigate possible conformational or orientation changes when increasing the hydrophobic residue by means of optical rotation measurements and compression isotherm determinations. Finally, as the enkephalin molecule itself suffers an extremely rapid inactivation in brain tissues due to the proteolitic enzyme action, several tests to check the resistance of lipoenkephalins to en zymatic hydrolysis have been carried out, allowing us to confirm that the hydrophobic residue prevents that action.