Electrospray ionization time-of-flight mass spectrometry is a good tool for the characterization of noncovalent complexes because of "soft" ionization and condition. Under our experimental conditions. the nonspecific noncovalent interactions of egg-white lysozyme with β －cyclodextrin have been observed by electrospray ionization/time- of flight mass spectrometry. Some mass spectrometic feature, such as ion abundance enhancement by selecting appropriate nozzle potential, and stoichimetries, show that the noncovalent complexes between lysozyme and β－cyclodextrin have been formed at a ratio of 1:1, 1:2, 1:3 in higher concentration and almost left ratio 1:1 in lower concentration of β－cyclodextrin. These results imply that the complexes should be nonspecific complexes. In addition, we founded that the appropriate condition, such as addition of some organic solvent of suitable SCIEX chamber temperature, is conductive to the ionization of noncovalent conplexes.

Key words: TIME-OFF FLIGHT MASS SPECTROMETRY, LYSOZYME, CYCLODEXTRIN, COMPLEX