A unique bacterial protein selectively binds an unstable triferric citrate complex to import iron into Bacillus cereus cells, reports a team from the University of California, Berkeley (Proc. Natl. Acad. Sci. USA, DOI: 10.1073/pnas.1210131109). Iron is an essential element that bacteria commonly sequester by sending ligands, called siderophores, to chelate insoluble Fe(III) in the environment. Selective binding and transport proteins then convey the complexes back into the cells.
Common siderophores include citrate and citratebased ligands. Citrate’s carboxyl and hydroxyl groups coordinate Fe(III). Previously, however, citrate-binding proteins were observed harboring only Fe(citrate)2 and Fe2(citrate)2. Kenneth N. Raymond and colleagues have now identified a B. cereus protein, christened ferric citrate-binding protein C, or FctC, that selectively binds Fe3(citrate)3 even when other iron-citrate species are present in solution. Only a few closely related species have genes for similar proteins, so FctC may give the B. cereus group an advantage by enabling import of iron complexes that other bacteria cannot sequester.
The “12th German Ferrofluid Workshop” was held from Sept 26-28 in the Cloister Benediktbeuern close to Munich. More than 80 attendees presented 53 scientific contributions in 24 talks and a poster for each contribution. During the meeting the general assembly of the “Ferrofluid Society Germany”, which organizes this meeting and others, was held in a closed session. Because of the upcoming DFG Priority Program “Field controlled particle matrix interaction: synthesis, multi-scale modelling and application of magnetic hybrid-materials” the workshop was focused on these topics. Detailed information to the program and the abstracts of the workshop as well as for past workshops can be found here (in the frame “archive").
The next workshop will be organized in combination with the kick-off meeting of the Priority Program in the week of Sept 24-28, 2013 in the Cloister Benediktbeuern again. More information and contact addresses concerning the Priority Program are listed on the pages of the German Research Council (DFG).
Figure: Setup for experimental investigation of magnetically induced deformation of magnetic fluids presented by Jana Popp (Zimmermann group) from Technical University of Ilmenau.
Submitted by Silvio Dutz, Institute of Photonic Technology IPHT, Jena, Germany.
Dr. Thomas Tourdias and colleagues recently published a study where they investigated if a combination of gadolinium-enhanced MRI (dotarem) followed by the injection of ultrasmall superparamagnetic iron oxide particles (USPIO) (sinerem) had advantages for the assessment of disease activity in multiple sclerosis phenotypes. Very interesting and well done study, in which they found that the combination of gadolinium and USPIO in patients with MS can help identify additional active lesions compared with the current standard, the gadolinium-only approach, even in progressive forms of MS. Lesions that enhance with both agents may exhibit a more aggressive evolution than those that enhance with only one contrast agent.
To look at the details, please click here.
DNA molecule control the shape and surface properties of gold-DNA nanoparticles. The findings could be used to create nanoparticles with shapes optimized for sensing, imaging, catalysis, and other applications.
Researchers often use DNA strands to help control morphology in nanoparticle synthesis, but the process has been by trial and error. Chemical biologist Yi Lu
of the University of Illinois, Urbana-Champaign, and coworkers, including Jinghong Li’s group at Tsinghua University, in Beijing, have discovered the method to this madness in preparing gold-DNA nanoparticles. By systematically varying DNA sequences added to solutions used to make gold-DNA nanoparticles, they found that like a genetic code, specific sequences lead
to distinct particle shapes and surface characteristics ( Angew. Chem. Int. Ed., DOI: 10.1002/anie.201203716 ).
A fluorescent molecule that glows brighter in the presence of weak magnetic fields can enable an ordinary microscope to map the fields around magnetic nanoparticles (Nano Lett., DOI: 10.1021/nl202950h). Researchers hope that similar molecules could aid the development of nanostructures for data storage and quantum computing.
When materials scientists design new magnetic nanoparticles, such as those in memory chips, they have to collect detailed information about the strength and distribution of magnetic fields around them. To gather these data, the researchers rely on expensive equipment and complex setups. For example, liquid helium must cool the magnetometers used in superconducting quantum interference device (SQUID) microscopy. Adam E. Cohen, a chemist at Harvard University, and his colleagues envisioned a much simpler measurement based on the chemistry of an indicator molecule.
Normally, magnetic fields have little effect on the course of chemical reactions, says Cohen. When compared to heat energy, the energy from the interaction of a magnetic field and the spin of an electron is extremely small. But Cohen and his colleagues predicted that even very weak magnetic fields could strongly influence the emission of light by specific types of fluorescent molecules.
To create complex colloidal hybrid nanoparticles—materials with various types of nanoparticles fused together—nanoscience researchers at Pennsylvania State University are taking a cue from their colleagues in organic synthesis. Guided by mechanistic considerations, Raymond E. Schaak, Matthew R. Buck, and James F. Bondi use chemical transformations to tack together simpler pieces of the structure in a predictable manner (Nat. Chem., DOI: 10.1038/nchem.1195). “We are trying to bring the elegance of organic total synthesis to the world of inorganic nanostructures,” Schaak tells C&EN. “We approach the synthesis in a stepwise manner; identify plausible reaction mechanisms; and develop, define, and exploit unique solid-state analogs of concepts that underpin organic synthesis but that are not typically in the nanomaterials chemist’s toolbox, such as chemoselective and regioselective reactions, coupling chemistry, and substituent effects.” For example, the researchers create gold-platinum-iron oxide hybrid nanoparticles from the reduction of gold ions in the presence of Pt-Fe3O4. One might expect the resulting gold nanoparticle to fuse to the Pt, the Fe3O4, or both regions of the particle, but the Penn State team found that the gold particle fused exclusively to Pt, demonstrating regioselectivity in their synthetic scheme.
To dissolve blood clots, biomedical engineer Donald Ingber of Harvard University and colleagues modelled nanoparticles after platelets—cells that circulate in the blood and help stop bleeding by forming clots. The nanoparticles are less than 100 nm wide and made of synthetic polymers stuck together like a ball of wet sand. Like platelets, clumps of the particles flow freely in the blood and gravitate toward blocked vessels by sensing a change in blood flow. Once there, they break apart into individual particles that stick to the clot, releasing a drug called tissue plasminogen activator (tPA) that dissolves it.
A three-component metal alloy mediates electrocatalytic reduction of oxygen to water more effectively than pure platinum and platinum-based bimetallic catalysts.
Oxygen reduction is a critical reaction
in fuel cells and metal-air batteries.
Nanoparticulate platinum supported
on carbon is considered the best catalyst
for that reaction, but kinetic factors
prevent platinum from reaching its
theoretical catalytic effectiveness. In
addition, the metal is costly and relatively
scarce. Recent investigations have focused on platinum-based bimetallic substitutes, but three-component systems have not been explored systematically. Vojislav R. Stamenkovic and coworkers prepared bimetallic and trimetallic thin films of platinum alloyed with iron, cobalt, and nickel and compared their measured electrocatalytic activities with their predicted oxygen binding energies. The group’s tests show that a catalyst consisting of 6-nm-diameter particles of PtCoNi (atomic ratio roughly 3:0.5:0.5) is more active for oxygen reduction than platinum-based bimetallic catalysts and four times as active as pure platinum. Check the paper out here.
For more information, check out our Archives.