Conformation of Macromolecules in the Gas Phase: Use of Matrix-Assisted Laser Desorption Methods in Ion Chromatography

Science  10 Mar 1995:
Vol. 267, Issue 5203, pp. 1483-1485
DOI: 10.1126/science.267.5203.1483


Conformational data for macromolecules in the gas phase have been obtained by the coupling of a matrix-assisted laser desorption ion source to an ion chromatograph. A series of polyethylene glycol (PEG) polymers "cationized" (converted to a cation) by sodium ions (Na+PEG9 to Na+PEG19) and a protonated neurotransmitter protein, bradykinin, were studied. Mobilities of Na+PEG9 to Na+PEG19 are reported. Detailed modeling of Na+PEG9 with molecular mechanics methods indicates that the lowest energy structure has the Na+ ion "solvated" by the polymer chain with seven oxygen atoms as nearest neighbors. The agreement between the model and experiment is within 1 percent for Na+PEG9, Na+PEG13, and Na+PEG17, giving strong support to both the method and the deduced structures. Similar agreement was obtained in initial studies that modeled experimental data for arginine-protonated bradykinin.

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