Collaborative Research; Protein Mediated Magnetite Biomineralization

点击翻译按钮获取中文摘要

There is increasing demand for magnetic nanoparticles in emerging areas of technology and medicine (e.g., high-density data storage, targeted drug delivery, scaffolding for tissue regeneration). The "ideal" particle for many of these applications is a nanometer scale magnet that has defined shape and morphology, narrow size distribution, high crystallinity, and controlled magnetic direction. Magnetotactic bacteria (MTB) have the innate capacity to synthesize crystals of the mineral magnetite (Fe3O4) that meet all of these criteria. In this proposal, investigators will study the protein-directed crystallization of magnetite by MTB. MTB exercise strict genetic control over the size, composition, and morphology of their nanomagnetic crystals. Investigators will examine the so-called Mms proteins (Mms-5, 6, 12, 13; or homologues like MamC) to identify the key catalytic domains that direct nucleation and growth of Fe3O4. In vivo biomineralization experiments will be performed using wild-type strains (e.g., Magnetospirillum magneticum) as well as mutationally altered strains generated during this project. In vitro crystallization experiments will be carried out using recombinant proteins, or peptides that mimic key motifs. Structural and magnetic properties of the in vivo vs. in vitro mineral products will be characterized using electron microscopy, atomic force microscopy, confocal laser scanning microscopy, and magnetometry. Those proteins or peptides that catalyze novel mineral products will be further examined using molecular dynamics simulations in silico. The knowledge to be gained from these studies will allow to fabricate nanometer scale, single domain magnetic crystals that are designed to elicit a particular magnetic response. This project also includes an educational outreach component for middle- and high-school students and teachers. Teachers will spend 3-4 weeks each year with the PIs learning how to collect and isolate MTB from environmental samples as well as characterize MTB with various forms of optical and electron microscopy. Based on this experience, the teachers will design experiments to use in their own classrooms. Investigators will also direct two field camps: an annual, domestic camp on environmental microbiology and one international field camp on biomineralization. Student participants will learn to design and test scientific hypothesis though field studies, lab experiments, and instrumental analyses (e.g., electron microscopy). The students will present their results at an annual science symposium.