Receptor Specificity and Threshold Concentration in Chemotaxis of the Phaeophyte Cutleria multifida

Sexual reproduction has a decisive function during the life cycle of all organisms. In the marine brown alga Cutleria multifida, multifidene (1), a low molecular weight olefinic hydrocarbon, has been recognized as a chemical messenger for gamete union. Comparative activity tests with 32 specially designed synthetic analogous of the natural attractant demonstrate the high specifity and low threshold concentration (6.5 × 10-12 mol/L) of the gamete’s receptor system toward its natural signal (1). The findings establish the double bonds of multifidene (1) as the molecular coordination points in the messenger-receptor interaction. A tentative model is presented, which takes into account the evidence, that unpolar, but highly polarizable functional groups in the correct spatial arrangement are necessary for maximal mutual interaction