MASS-SPECTROMETRIC APPROACHES TO MOLECULAR CHARACTERIZATION OF PROTEIN-NUCLEIC ACID INTERACTIONS

The recent development of 'soft' ionization-desorption methods has lea d to a breakthrough for the mass spectrometric analysis of biomacromol ecules such as proteins and nucleic acids. In particular, the feasibil ity of electrospray-ionization mass spectrometry (ESI-MS) for the dire ct characterization of non-covalent supramolecular complexes is openin g new analytical perspectives. Examples hitherto analyzed by ESI-MS in clude enzyme-substrate and -inhibitor complexes, homo- and heterodimer s/trimers of leucine zipper polypeptides, and several other DNA- and R NA-binding proteins. Furthermore, the characterization of double-stran ded and higher-order oligo- and polynucleotide complexes by negative-i on ESI has been demonstrated. Ions specific of non-covalent protein an d oligonucleotide complexes can be selectively dissociated by changing the solution conditions and by increasing the desolvation potential. These results form the basis for the molecular characterization of pro tein-nucleotide interactions, thus complementing protein-chemical appr oaches, and other methods of structure determination.