A CHEMICAL CHARACTERIZATION OF ADSORBED DISSOLVED ORGANIC MATERIAL FROM AN ESTUARINE SOURCE (MISSISSIPPI, PROTEINACEOUS)

Interactions between proteins and interfaces are widespread. The role of protein adsorption in tissue culture, biocompatibility, serological tests, emulsification and stability of dispersions is well documented. The proposed role of protein adsorption as a conditioning film required for microbial colonization has far-reaching implications for the design of dental implants and prosthetic devices and for marine engineering. Yet, a comprehensive theory of protein adsorption has remained elusive.;This work presents the results of the first attempt to chemically characterize adsorbable dissolved organic material from naturally-occurring water and to define the role of surface charge on the chemical composition and quantity of the adsorbed material. Pyrolysis - chemical ionization, mass spectrometry and fluorescence spectroscopy were used to characterize adsorbed dissolved organic material (ADOM) from the estuarine waters of Bay St. Louis, MS, as proteinaceous in nature. Microelectrophoretic mobilities and corrosion potential measurements substantiate this conclusion. Adsorbed organic material results in a net negative change and a negative shift in the surface potential similar to that induced by other proteinaceous materials. Surface properties such as potential, charge, and critical surface tension influence the composition of the adsorbed film during the first hour of exposure. However, after four hours it appears that a uniformity is reached and that the composition of the adsorbed material is substratum independent. Voltage clamping experiments were conducted on titanium surfaces exposed in an estuarine (3('o)/oo) and a marine (35('o)/oo) environment. The estuarine environment contained slightly higher concentrations of total organic carbon and amine-containing compounds. The quantity and chemical composition of the ADOM was independent of imposed charge over a wide range of potentials for both locations, but there was a great deal of variation between the sites. A three-fold increase in the amount of adsorbed material was observed from the marine environment, indicating that adsorption increases as ionic strength increases. Furthermore, an enhanced adsorption at the anodic potential, +1.16 V/SCE was observed at the marine site, due to an electrostatic attraction between the adsorbing protein and the titanium surface. The mass pyrograms of ADOM from four locations demonstrate that the chemical composition is site specific.