This new proposal outlines four specific objectives for biomedical research in which continuous introduction ion spray mass spectrometry will be used to monitor noncovalent interactions between important biological macromolecules. The broad, long-term objectives of this work are to advance our fundamental chemical and biological understanding of noncovalent interactions which constitute the essential basis of molecular recognition in the biological world. Specific aims include the following: (1) Studies on protein-effector noncovalent interactions, including enzyme-substrate, receptor-ligand and low MW antibody-antigen complexes will be conducted, to gain a better understanding of what non-covalent interactions are most suitable for mass spectrometric detection. (2) Ion spray MS will be used to examine the noncovalent binding in double-stranded nucleic acids, as well as the binding of DNA to various drugs, in an attempt to observe molecular ions corresponding to these species. Further work will examine other H-bonded nucleic acid complexes, including triple-helical DNA and circular DNA complexes. The formation of noncovalent DNA complexes of anticancer, antileukemic and antibacterial drugs will be investigated. (3) Protein-protein and protein-DNA interactions will be monitored by ion spray MS to gain a better understanding of the weak associative interactions in their complexation. Various protein structural motifs important in transcriptional activation and other genome regulatory processes will be studied. (4) MS studies on macromolecular aggregates will be initiated using two novel ion spray techniques -- real-time reaction monitoring and noncovalent complex detection -- to characterize structural changes and elucidate some of the detailed biochemical events involved in DNA replication by the bacteriophage T4.