9(10)-alkoxystearic acids lengthen the circadian period of a fatty acid auxotroph of Neurospora crassa.

9- and 10-Alkoxystearic acids with alkoxy groups of varying size were synthesized by solvomercuration of methyl oleate. These "knobbed" fatty acids were used to supplement a Neurospora strain carrying the cel mutation, which confers a partial fatty acid deficiency. Supplemental unsaturated or short-chain fatty acids are known to lengthen dramatically the circadian period of spore formation (conidiation) in cel strains. A similar dramatic lengthening was obtained with the alkoxy supplements. The change in period, however, did not correlate positively with the size of the knob. Smaller knobbed analogs gave somewhat greater period lengthening and were removed from the medium faster. It may be that the knobbed analogs cause period lengthening by an indirect effect on Neurospora membranes rather than, or in addition to, a direct perturbation.