Lipid phase transitions and a possible lipid-protein lattice structure as an activity regulator in maturing spermatozoa

: This study was performed, in order to define the sperm-egg interaction as a membrane-membrane interaction, to validate the hypothesis that the physical structure of the biomembranes can dictate their overall fusion behavior and that the sperm membranes undergo 'fusion-favoring' modifications during epididymal maturation. Informations from the lipophilic domains, aqueous compartments and the protein components were gathered. The lipophilic domains were found to undergo profound alterations in their local viscosity, polarity, molecular ordering and lateral diffusion patterns. The rotational mobility of proteins appeared to be restricted, and the aqueous compartments transformed to a more viscous state at the late phase of maturation. Correlative evidence suggests a possible relation between the specific protein activation/inactivation reported earlier and the physical changes reported herein.