The homogeneous catalysis based on the principle of diffusion of ligand-capped metal nanoparticles has recently drawn more interest as regards to its potential as enzyme mimics, which are one of the highest priority areas in the field of biotechnology and medical research. In particular, the ability of simple model nanostructured materials in enhancing or resisting the adsorption of particular substrates similar to that of enzymes is in needs of active investigation. Our research group has recently developed a new catalytic system that exhibits excellent activity and selectivity for the isomerization and/or hydrogenation of alkenes and alkynes. Considering their size (6-8 nm in overall particle diameter), spherical shape, and versatile ligand characteristics, the availability of these well-designed organic ligand-capped nanoparticles with active catalytic metal core will especially benefit the advancement in nanoparticle-based metalloenzyme mimics. For example, by introducing different hydrophobic functional groups in the tail of hydrocarbon chains of organic ligands, we can adjust steric and/or non-covalent interactions in the near-surface environment in a manner analogous to changing amino acid residues (side groups) in an enzyme binding pocket. This approach will allow the investigation of the ability of surface immobilized ligands on precisely tuning catalytic selectivity through these molecular interactions. The proposed four-year SCORE SC3 research program will focus on understanding how near-surface steric controls, non-covalent interactions, and chiral interactions determine the catalytic properties of the modified nanoparticles towards the model organic reactions relevant to the biologically important transformations (olefin reduction and isomerization). Requested funding provides summer and academic support for the PI, support for 1 post-baccalaureate fellow or technician/year, chemicals, supplies, lab consumables for research activity, and travel expenses for dissemination. The work involves four major tasks: 1) Metalloenzyme mimics with near-surface steric controls for chemo selective and regioselective reactions. 2) Metalloenzyme mimics with non-covalent interactions for chemo selective and regioselective reactions. 3) Metalloenzyme mimics with chiral interactions for stereo selective reactions. 4) Metalloenzyme mimics with controlled surface ligand polarity for biologically important reactions in water. This research plan will allow the PI to develop the basic and translational research skills to become an independent expert in nanomaterials structure controls, materials characterizations, and metalloenzyme mimics for biologically important transformations. Simultaneously, this program will provide graduate (M.S.-level, 2 students/year) and undergraduate students (4 students/year) with unique and exciting research opportunities in nanotechnology. Through enrollment in existing research-based classes, students will be offered the opportunity to be participants in an interdisciplinary research program that will collaborate on all aspects of this project - from inception, starting with basic nanoparticulate material synthesis, to completion, with the ultimate evaluation of the catalytic performance of these new metalloenzyme mimics. They will also develop the intellectual capacity to critically analyze existing information as well as develop proficiency in the analysis, interpretation and presentation of complex data sets. PI will actively recruit females and/or minority students, traditionally underrepresented groups in chemistry, to enhance the balanced advancement of research and education (CSULB is designated as a Hispanic Serving Institution). PI has a good track record of participating minority undergraduate research programs such as BUILD (Building Infrastructure Leading to Diversity funed by NIH), MARC (Minority Access to Research Careers funded by NIH), RISE (Research Initiative for Scientific Enhancement funded by NIH), BRIDGES (Bridges to the Baccalaureate funded by NIH), in addition to LSAMP (Louis Stokes Alliance for Minority Participation program funded by NSF) that are currently available in CSULB.
Advancing basic understanding of the relationship between the catalytic properties and the surface adsorbents is important for exploiting small nanoparticles in catalysis, especially with their high potential for enzyme mimics considering their size and spherical shape (6 - 8 nm; a la globular proteins) in addition to versatile ligand characteristics. A few examples are recently reported in the literature in this field, however, a fundamental and systematic investigation covering a large number of aspects is currently lacking for the scientists to design the highly desirable efficient enzyme-like catalyst for biologically important reactions. The unique structura properties of these organic ligand-capped metal nanoparticles make them ideal candidates for use as a model for enzyme catalyzed reactions. The proposed research is a fundamental research investigation focused on understanding how several factors, such as structure and functionality of the ligands, ligand density of the organic ligands adsorbed on the nanoparticle surface, core size of the nanoparticles, and ligand conformational changes, determine the catalytic properties of the modified nanoparticles towards biologically important transformations (olefin reduction and isomerization). The studies would be an important step towards the expansion of the simple model system to more complex ones that mimic the binding pockets of enzymes. Ultimately, the findings will be applied to the development of optimized nanoparticle-based metalloenzymes with high regioselectivity, chemo selectivity, and/or stereo selectivity for biologically important reactions.
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