We will apply chemical labeling and mass spectrometric methods to the study of protein adsorption on biomaterials. We believe that with these methods, we can assign the conformational changes that occur within proteins following adsorption to specific sites on the protein. We have recently published a study that demonstrated that the chemical labeling of lysine groups on fibrinogen increased when the solution concentration decreased. We now wish to use quantitative mass spectrometry combined with the chemical labeling technique to further explore changes in fibrinogen conformations upon adsorption to two biomaterials, PET and PTFE. Quantitative mass spectrometry is difficult to achieve with proteins. Our collaborators at Washington University have demonstrated a technique that is quite promising in reducing errors associated with protein quantification by tandem mass spectrometry. The combination of methods, chemical labeling of adsorbed proteins to detect changes in protein conformation and quantitative mass spectrometry, may lead to advances in the study of protein adsorption on biomaterials. The use of the new techniques will be directed towards answering questions about the impact of fibrinogen's post-adsorptive conformational changes on the adhesion of platelets to biomaterials. We will demonstrate that: Aim 1: Adsorption of fibrinogen to biomaterials leads to changes in the solvent exposure of lysine and tyrosine groups near sites that promote biological activity. Aim 2: The degree of solvent exposure at these sites correlates with platelet adhesion to adsorbed fibrinogen. PUBLIC HEALTH RELEVANCE: The biological response that is mounted against artificial implanted materials constrains the use of medical devices such as vascular grafts, endovascular stents and many other devices that are in contact with flowing blood. A major mediator of the response is the protein fibrinogen, which adsorbs to materials and supports platelet and leukocyte adhesion. The proposed project will probe the conformational changes in adsorbed fibrinogen that lead to biological responses, which will allow us to better understand the biocompatibility of materials.