Unraveling at Micro- and Macro-scale the Mineral Surface Reactions of Amino Acids and Small Peptides Using Phage Display Technology Coupled with Synchrotron-Based Spectroscopy

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Intellectual merit: The latest terrestrial N cycle paradigm considers soluble organic nitrogen (SON) as a rate limiting step for regulating the overall N availability in ecosystems. Our lack of understanding of the micro-scale processes/mechanisms of interactions between soil minerals and SON compounds hinders our ability to predict N flux between different soil compartments at the ecosystem-scale. To address this issue, an interdisciplinary approach that combines a broad array of novel molecular, biological, and synchrotron-based spectroscopic techniques is proposed to investigate the interaction mechanisms between soil minerals and amino acids and small peptides, two key components of soil SON. Novel methods will be used to achieve the research. The phage display technique will be used to screen, in a short period of time, billions of random small peptide sequences for those peptides displaying a selective affinity for a particular mineral surface. Macro-scale adsorption isotherms for amino acids and small peptides on four minerals commonly found in soil will be obtained. Using the samples collected from the adsorption isotherms experiment, polarization-dependent N (1s) near-edge x-ray absorption fine structure (NEXAFS) will be used to investigate, at micro-scale, the average molecular surface orientation. Lastly, a microbial essay method will be used to understand at micro-scale how molecular surface organization on mineral surfaces affects the microbial utilization of adsorbed amino acids and small peptides.Broader impacts: The PIs are cooperating with two local high schools (The Mississippi School for Mathematics and Science and The West Oktibbeha County High School) to recruit future minority undergraduate students for summer research projects. Those summer research projects will provide minority high school students opportunities to gain hands?]on experience in biogeochemistry research and state of the art instrumentations, to obtain insight into the nature of both undergraduate and graduate school, to work with university professors and graduate students as an interdisciplinary team, and to have informed choices about how to advance their future career. The students will also be given the opportunity to attend regional or national meetings and to visit national laboratories. The work from these students and the research of this proposal will be showcased at their high schools and highlighted in state competitions such as the Engineering Fair and the Young Scientist Division at the Mississippi Academy of Science.