Surface activity properties of cysteine-substituted C-terminal melittin analogues.

In order to extend our knowledge of factors important in the surface activity of melittin, cysteine was substituted for lysine-21 and lysine-21/glutamine-25 in a pair of synthetic peptide analogues. The first of these changes resulted in only modest effects on secondary structure (determined in 50% trifluoroethanol), emulsification and surface tension properties. Introduction of a second cysteine greatly reduced both the rate of surface tension decay and the equilibrium surface tension attained, although secondary structure (determined in 50% trifluoroethanol) was only slightly affected by this modification. This latter peptide completely lacked emulsification and haemolytic properties and was found to oligomerise readily due to the formation of intermolecular, disulphide bridges. These results indicate that oligomerisation abolishes surface activity in melittin.

Variable association of HLA-A2 in men with early-onset Alzheimer disease.

In the present study, we attempted to replicate the finding of an increased frequency of HLA-A2 in men with early-onset (less than or equal to 60 years) Alzheimer disease (AD). HLA data obtained on 167 patients (including 19 men with early-onset AD) from three geographic regions (North Carolina, Great Britain, and Finland) failed to replicate the result. A recent prospective study from Oregon, however, confirmed the association. Studies demonstrating the association suggest its presence in sporadic rather than familial AD. These results indicate a variable HLA/AD association, with some factor such as geographic region or disease familiality contributing to this variability.