The present invention provides a method of analyzing the physiological function of a target substance by inactivating the physiological function of the target substance, comprising the steps of: (a) binding to the target substance a photoactive compound represented by formula (I): ##STR00001## (in the formula, Q is a group for binding this compound with the target substance) to form a composite comprising the target substance and the photoactive compound; and (b) irradiating the obtained composite with light to inactivate the function of the target substance to which the photoactive compound has been bound, or to inactivate the function of the target substance at the site where the photoactive compound has been bound.