Abstract
The enantiomorphs of sirenin and several analogues of sirenin were tested for their activity in attracting the sperm of Allomyces. Only l-sirenin was active. The uptake of sirenin by the sperm was measured from solutions containing l-sirenin in concentrations from 5 to 10,000 nm. Uptake from 5 and 100 nm followed first order kinetics. At higher concentrations the rate of uptake slowed down, and at the very highest ones it stopped after a few minutes. When sperm had taken up all the sirenin from a 5 nm solution, it took approximately 45 minutes for them to regain full responsiveness. After uptake of sirenin by sperm, none could be recovered from them.