Abstract: Several specific non-covalent protein complexes were successfully observed by matrix assisted desorption ionization mass spectrometry(MALDI MS). The methods described in this paper include the matrixes use of sinapinic acid(SA) and 6-aza-2-thiothymine(ATT) in neutral pHsolution, as well as the improvement of two-layer sample preparation method to achieve a high sensitivity detection of stable non-covalent complexes. Myoglobin-heme complex was found simultaneously with the sinapinic acid matrix in the various pHsolution(pH=2 or pH=5). The RNase Scomplex showed a striking intensity at the first shot, which was decreased with more laser shots. Most importantly, the observation of specific noncovalent complex in the brome mosaic virus(BMV) coat proteins would open up a new possibility to investigate the assembly and disassembly of viral capsids.

Key words: Non-covalent complex, Non-covalent protein interaction, Matrix assisted desorption ionization mass spectrometry