IP + macrocycles have the potential to act as electrophiles. mercaptoethanol (5 mM), at 37 o C for 24 hours. LC-MS analysis of the solutions showed that the IP+ MP were stable under these conditions; no new peaks were observed. A similar experiment was done using the amine nucleophiles hydrazine and piperidine with the same result. We conclude that the IP+ MP are stable under physiological conditions with respect to reaction with nucleophiles.