Nearly all proteins are surface active--they adsorb, orient, and often denature (undergo conformational changes) at water/air, water/oil, and water/solid interfaces. The absorption of contact activation proteins in blood can lead to coagulation; the adsorption of IgG, complement C3 and/or complement C1 can lead to complement activation; the absorption of lipoproteins may be important in atherosclerosis and thrombogenicity. In the case of tears, tear proteins produce deposits on many types of contact lenses. Although there has been much progress in understanding and controlling protein interfacial activity, it is desirable to be able to directly observe protein--surface and protein--protein interactions--in situ--under physiologically relevant conditions. Direct observation is now possible by scanning force microscopy (SFM). This new and very powerful technique is now applicable to protein interface research. We propose to develop the methods, techniques, and theory to permit the routine observation and interpretation of protein interfacial processes. We will apply the technique to three important studies: 1. The orientation and ordering of immunoglobulins at interface. 2. The competitive adsorption of selected plasma proteins--The Vroman Effect. 3. The direct observation of polyurethane surfaces in water.
