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Early Career: Emergent Atomic and Magnetic Structures

Characterization
Determining the nature of the macromolecule-mediated magnetic nanoparticle formation:

Uniform magnetic nanoparticles with large magnetic moment and controlled magnetic anisotropy have important technological applications from data storage and quantum computing to catalysis and drug delivery.  The Emergent Magnetic and Atomic Structures Group works to determine the nature of macromolecule‐mediated magnetic nanoparticle formation: i.e., the mechanism of particle nucleationand growth, the emergence of crystal structures, and the development of ferromagnetism in the individual bio‐templated magnetic nanocrystals. By utilizing advanced electron microscopy techniques, we work towards gaining a better understanding of how the assembly of biomacromolecules dictates nanoparticle formation and functional properties.

Correlative electron microscopy of magnetotactic bacteria in liquid:

Magnetotactic bacteria biomineralize ordered chains of uniform magnetite or greigite magnetosome nanocrystals with nearly perfect crystal structures and species-specific morphologies. As a result, these microorganisms are one of the best model systems for investigating the molecular mechanisms of biomineralization. Using the liquid cell scanning transmission electron microscopy (STEM) holder, we can image biomineralizing microorganisms in their natural environment with nanometer resolution. This correlative fluid cell STEM and fluorescence microscopy technique is a first step in directly observing biomineralization of magnetite in viable magnetotactic bacteria. We expect this technique to be generally applicable for in vivo imaging of a wide range of biomineralizing organisms.

Tuning the bacterial iron biomineralization:

Iron is biomineralized by many different microorganisms, and tweaking this process exerts control over the magnetic properties of biogenic materials. Biomioneralization can be controlled to yield nanocrystals with tunable composition and magnetic properties. Comprehensive characterization of biominerals reveals the key factors affecting bacterial iron biomineralization.

Equipment:

  • Continuous fluid flow Cell Holder Platform, equipped with a turbopumping station (Hummingbird Scientific) and digital camera (Leica)
  • Vapor Delivery system Module for use with the continuous fluid flow liquid cell holder(Hummingbird Scientific)
  • Nano eNabler Molecular Printer (BioForce Nanosciences)
  • Magnetherm V 1.5 AC system (Nanotherics), equipped with a fiber optic thermometer
  • Auxiliary equipment: oven; vacuum oven; stand-alone portable RGA module (Stanford Research); controlled temperature circulation bath; Gatan 626 TEM cryo-holder and fully equipped Cryo-Plunger Vitribot (Gatan); glow discharge unit (Pelco); 2 ozone plasma cleaners (BioForce); Midmark 11autoclave sterilizer (Ritter); Shlenk line, glovebox (Vac. Atm.) equipped with a cold storage box and solvent trap; acrylic glovebox unit for cell assembly under argon flow equipped with Leica camera setup unit; two laminar flow hoods; centrifuge and microcentrifuge; direct Immersion ultrasonic horn apparatus (Sonics and Materials)miscellaneous other devices making researchers’ lives a bit easier.

Project Leader(s):

Postdoctoral Research Associate(s):

  • A novel approach to image viable magnetotactic bacteria in their native environment has been reported. Magnetotactic bacteria naturally form ordered chains of magnetic crystals in a process known as biomineralization. The magnetic particles formed by these microorganisms are nearly perfect crystals, making magnetotactic bacteria one of the model systems for studying the fundamental mechanisms of biomineralization. The scientists used a combination of scanning transmission electron microscopy (STEM) and fluorescence microscopy techniques.

  • For the first time, scientists have visualized the first steps of bacterial protein involvement in the formation of crystal seeds, or nucleation. Magnetotactic bacteria are a group of bacteria that naturally produce magnetic crystals and the protein Mms6 is thought to play an important role in this process.