Mineral crystallization is ubiquitous in environmental and biological systems and its progression in these settings reflects an inexorable link between the two. Particle aggregation, such as oriented attachment, is a common mechanism of mineral growth. During mineralization, biopolymers, including proteins, peptoids, carbohydrates, and metabolites, operate as control agents, interacting with both the precursor ions and mineral surfaces to regulate particle aggregation. While these effects enable organisms to control the formation of hierarchical structures that provide solutions to functional requirements, the widespread presence of biopolymers in the extracellular pore space of soils also produces uncontrolled effects over abiotic mineralization, impacting the phases and morphologies of soil minerals. However, despite the importance of mineral-biopolymer interactions in regulating mineralization, a mechanistic understanding remains elusive. Key EMSL capabilities have allowed us to investigate in detail organic-mineral surface interactions and mechanisms of mineralization. Our recent work, enabled by EMSL ex-situ and in situ TEM, mass spectrometry, and computational facilities, shed light on the mechanism by which self-organized assemblies of hematite nanoparticles (referred to as “mesocrystals”) form through interface-driven hematite assembly when oxalate is present. The challenge now is that the dependence of particle assembly on features of organic ligands is difficult to decipher, because many factors, including binding affinity to the mineral, ligand-ligand interactions, headgroup charge, hydrophobicity, and ligand molecular volume vary simultaneously from one ligand to the next. Building on this previous work, the aim of this proposal is to utilize the capabilities of EMSL to explore the impact of biomolecules and small molecule protein-mimetics on mineral growth via particle aggregation (e.g. oriented attachment). Our proposed research utilizes a combination of oxide minerals — hematite (Fe2O3), anatase (TiO2), and rutile (TiO2) with well characterized surfaces and a class of synthetic organic ligands, known as peptoids, that are modular in nature, thus enabling systematic variations in each of the above ligand characteristics. Specifically, we will apply in situ AFM and ATR-FTIR to probe biopolymer-mineral interactions, and utilize in situ solution- and solid-state NMR to monitor the changes in the speciation and dynamics of both biopolymer and minerals over the course of growth. We will also use in situ liquid-phase TEM to directly image mineral growth via aggregation processes in solution at nm resolution to determine the mechanisms by which the biopolymer-mineral interaction alter mineralization pathways. We will use a combination of AIMD and classical MD to simulate the effect of biopolymers on liquid/solid interfacial structures, interpret experimental results, and predict interactions of biopolymers with the minerals. We believe the data from the advanced characterization techniques in EMSL will provide the basis to pursue DOE OBER funding for research into the molecular mechanisms of biopolymer-mineral interactions and the pathways and dynamics of mineral aggregation kinetics.