Fig. 3.

Structural requirements of the copper ion enhancement effect of MOR244-3. (A) Structural relationship between MTMT and its analogs. Odors boxed with solid lines are those with prominent responses in the presence of 30 μM Cu²⁺, and odors boxed with dashed lines are those with less prominent responses, as defined by a more than 50% reduction in efficacy compared with MTMT. Unboxed odors did not elicit MOR244-3 response. (B) Dose–response curves of MOR244-3 to representative sulfur-containing compounds with and without 30 μM exogenous Cu²⁺addition. For odors with a significant response in the absence of exogenous Cu²⁺, as defined arbitrarily by a top value greater than 0.32, dose–response curves with 30 μM of TEPA are also shown. The chemical structures of the respective compounds are shown in the upper left-hand corners. F tests were used to compare the pairs of dose–response curves with or without Cu²⁺. Asterisks represent significance of P values after Bonferonni corrections. **P < 0.01 (n = 3).