Dear Dr Grover,
Melatonin has been reported to bind to the calcium/calmodulin complex with high affinity (Life Sci (1993)53: 201-207; FASEB (1998) 13: 1401-1408) and it has been shown to inhibit Ca/calmodulin -dependent enzymes in presence of Ca/calmodulin in biochemical assays (Brain Res (1991) 557: 289-292; Biochim Biophys Acta (1996) 1290: 191-196). However, whether melatonin can bind to calmodulin and inhibit the activation of calmodulin-dependent enzymes within cells is not known.
We used 1 to 10µM TFP. At this concentrations TFP has been shown to be a potent calmodulin inhibitor.