Molecular recognition of biomolecules in the gas phase

Abstract

The first chapter introduces the most relevant noncovalent forces for gas phase experiments. Chapters 2-5 contain work on small clusters of biologically relevant molecules. In Chapter 2, it is shown that the unusual properties of arginine lead to extensive noncovalent clustering of this amino acid, when sampled by ESI-MS. The stability of the zwitterionic form of arginine for clusters without a net charge is addressed by theoretical methods in Chapter 3. In Chapter 4, the properties of the unusually abundant serine octamer are examined. Experiments demonstrate that this octamer has a strong preference to be homochiral. A structure for the serine octamer is proposed that is cubic and has a zwitterionic core. The results gathered from the serine octamer demonstrate that a homochiral preference can exist for very small clusters or ?nanocrystals.? The first gas phase synthesis for ATP is given in Chapter 5. ATP is easily synthesized in the gas phase from a cluster of three AMP molecules bound by a sodium salt bridge. Subsequent CAD spectra following the gas phase synthesis are identical to those obtained from an authentic sample of ATP in separate experiments. Chapters 7-9 deal with the molecular recognition of amino acid side chains in ESI-MS experiments. The ability of 18C6 to recognize and selectively attach to lysine residues is explored. Recognition of arginine side chains is accomplished in a similar manner by utilizing the larger dibenzo-30-crown-10 ether (DB30C10). The two techniques are mutually compatible, allowing for both crowns to be added to the same solution. Chapters 10-11 combine the recognition of 18C6 with various chemical functionalities in order to mediate peptide chemistry in the gas phase. In Chapter 10, a new class of molecules termed ?molecular mousetraps? is described. The mousetraps combine the recognition of 18C6 with the chemical reactivity of diazo groups. The resulting molecules are capable of noncovalently attaching to any molecule that contains a protonated primary amine. CAD can be utilized to activate the complex. In Chapter 11, the mousetraps are utilized in experiments with peptides. It is shown that covalent attachment can be achieved in a quantitative fashion.