Magnetic Colloids from Magnetotactic Bacteria: Chain Formation and Colloidal Stability

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Original entry: William Bonificio, AP 225, Fall 2009


Magnetic Colloids from Magnetotactic Bacteria: Chain Formation and Colloidal Stability. Albert P. Philipse and, Diana Maas. Langmuir 2002 18 (25), 9977-9984

Soft matter keywords

Liposome, C2AB, Vesicle, Protein, Epoxy.


The purpose of this study was to investigate the interactions and colloidal stability of the single domain magnetic nanoparticles produced by magnetotactic bacteria. Magnetotactic bacteria are a really cool type of bacteria that create these iron oxide paramagnetic nanoparticles within their cell walls that align with the earth's magnetic field which in turn direct the the bacteria down towards the ocean floor, to anaerobic conditions where they thrive. These researchers wanted to look at how these magnetic particles would effect the interactions between different bacteria.

Soft matter discussion

Schematic illustration of experiment. Immobilized vesicles 'glued' to mobile vesicles via C2AB.

(a) shows TIR images before and after the introduction of <math>Ca^{2+}</math>. (b) and (c) show TEM images of the liposomes before and after the addition of <math>Ca^{2+}</math>
Open and closed conformations of C2AB, from the paper: Structure of Human Synaptotagmin 1 C2AB in the Absence of Ca2+ Reveals a Novel Domain Association. Kerry L. Fuson,, Miguel Montes,, J. Justin Robert, and, R. Bryan Sutton. Biochemistry 2007 46 (45), 13041-13048

The academic group conducting this research was interested in single domain iron oxide colloids. They noted that the size of the colloids in magnetotactic bacteria (50nm) was much larger than anything that would form spontaneously form ferrofluids (10nm). Because they are so large they are expected to have much stronger dipole forces, and should form different patterns such as chains and rings if removed from the bacteria. The group wants to look at the properties of these colloids when removed from the bacteria, and this is their first study examining the magnetic properties of the bacteria themselves.