probe was incubated with a solution of neutravidin and washed extensively with washing buffer 1 mm tris hcl ph 7 5 with 0 1 triton x 100 and desalting buffer 1 mm tris hcl ph 7 5 dried and overlaid with energy absorbing matrix and then analysed with maldi tof mass spectrometry the mass spectra fig3 a 3 b and 3 c show the specific capture of neutravidin mh and mh 2 at 7310 and 14652 dalton in a further example the binding of a small molecule to a protein is demonstrated in fig1 a b and c the lactose rhodamine conjugate was specifically retained on a peg pll neutravidin arachis hypogea lectin surface whereas it could not be detected on a peg pll neutravidin fk506 binding protein surface this is another example for the detection of a small molecule protein interaction the example is surprising since binding constant for lactose and this lectin is in the millimolar range suggesting that the presence of the rhodamine moeity has increased the affinity of the small molecule ligand atp was enzymatically synthesized from the reaction of adp creatine phosphate and creatine phosphate kinase in 25 mm ammonium bicarbonate at ph 7 4 adp u2212 was detected at 427 6 dalton and adp na u2212 449 6 dalton see fig4 a the products of the creatine phosphate kinase reaction were detected at 507 6 529 6 551 6 and 573 8 which fits well with the expected molecular weight of atp u2212 and three atp sodium adducts atp na u2212 atp na 2 u2212 and atp na 3 u2212 control reactions in which either one of the substrates adp or creatine phosphate or.