The overall goal of this project is to understand the formation and function of the acquired enamel pellicle. The hypothesis is that the proteins constituting this pellicle structure derive essentially from salivary secretions. Since some salivary proteins exhibit in vitro a specific and selective adsorption to hydroxyapatite surfaces and since some of these components have been detected immunologically in the in vivo formed pellicle there is considerable indirect support for this hypothesis. The desirable direct route to prove this hypothesis, however, is a much more difficult task and has therefore not been pursued. This route is to isolate and characterize first the pellicle components and then trace their origin in salivary secretions. The progress made in our laboratory on salivary pellicle precursor proteins in conjunction with recent advances in protein chemistry as well as in molecular biology have made it feasible for the first time to test this hypothesis directly. The application encompasses a research plan which represents the first essential steps in this direction. The specific aims are: 1. To use the macaque proline-rich phosphoglycoprotein (MPRP) as a model pellicle precursor protein to determine incorporation, survival and competititon of MPRP and its constituent peptides in the in vivo formed acquired enamel pellicle. 2. To identify, isolate and determine the amino acid sequence of individual proteins and peptides of young and old human acquired enamel pellicles. 3. To differentiate between pellicle components which originate from salivary secretions and pellicle components derived from non-glandular sources. 4. To use a human submandibular gland cDNA library to identify and to determine the amino acid sequence of the parent molecules of pellicle components in glandular secretions. The work proposed will provide the basis for understanding the protection or failure of protection of teeth in the oral cavity at a molecular level.