DEFECT FORMATION ON SURFACES BOMBARDED BY ENERGETIC MULTIPLY-CHARGED PROTEINS - IMPLICATIONS FOR THE CONFORMATION OF GAS-PHASE ELECTROSPRAYED IONS

Indirect information on the conformation of highly charged molecular i ons may be obtained by monitoring their collisional cross sections and the course of simple gas-phase reactions such as hydrogen-deuterium e xchange. In this work, another indirect but more visually oriented app roach is explored: electrosprayed protein ions are accelerated toward a highly oriented pyrolytic graphite surface and the resulting single- ion defects are imaged by scanning force and tunneling microscopy. All protein impacts generated shallow hillocks: the shapes depended on th e identity and charge state of the incident protein. Lysozyme and myog lobin, both compact, globular proteins in the native state, produced c ompact, almost circular hillocks. However, hillocks generated by myogl obin that had been denatured in the solution phase were elongated, and the elongation was positively correlated with the charge state of the ion. It appears that structural information about gas-phase multiply charged proteins can be derived from imprints generated by energetic p rotein impacts on surfaces.