Biologists and physicists from the University of California, Santa Barbara (UCSB), have discovered living nanoscale 'necklaces'. They were studying "microtubules from the brain tissue of a cow to understand the mechanisms leading to their assembly and shape." And unexpectedly, they found that some divalent cations pushed these microtubules, which are nanotubes derived from cell cytoskeleton, to assemble into 'necklaces' of different shapes. Now they think their discovery could be used to deliver drugs or genes. These 'necklaces' also could be used to build biosensors or new optical nanomaterials. Read more...
Here is the description of the discovery.
The scientists studied microtubules from the brain tissue of a cow to understand the mechanisms leading to their assembly and shape. Microtubules are nanometer-scale hollow cylinders derived from cell cytoskeleton. In an organism, microtubules and their assembled structures are critical components in a broad range of cell functions -- from providing tracks for the transport of cargo to forming the spindle structure in cell division. Their functions include the transport of neurotransmitters in neurons. The mechanism of their assembly within an organism has been poorly understood.
the researchers report the discovery of a new type of higher order assembly of microtubules. Positively-charged large, linear molecules (tri-, tetra- and penta-valent cations) resulted in a tightly bundled hexagonal grouping of microtubules -- a result that was predicted. But unexpectedly, the scientists found that small, spherical divalent cations caused the microtubules to assemble into a "necklace." They discovered distinct linear, branched and loop shaped necklaces.
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This image shows the "schematics of higher-order assembly of nanometer-scale microtubules" (Credit: UCSB). Here is a link to a larger version (936 KB). |
And what can we expect from these living necklaces?
The scientists envision applications based on both the tight bundle and living necklace phases. For example, metallization of necklace bundles with different sizes and shapes would yield nanomaterials with controlled optical properties.
A more original application is in the area of using the assemblies -- encased by a lipid bilayer -- as drug or gene carriers where each nanotube may contain a distinct chemical, as noted by the team. In delivery applications the shape of the bundle determines its property. For example, the linear necklace phase with its higher surface to volume ratio would have a larger contact area and a faster delivery rate compared to the tight bundle phase.
The research work has been published online by the Proceedings of the National Academy of Sciences under the intriguing title "Higher-order assembly of microtubules by counterions: From hexagonal bundles to living necklaces." It should appear in the printed version on November 16, 2004. Here is a link to the abstract of the paper.
For more information, you can visit the Materials Research Laboratory website at UCSB, and more specifically, the Biomaterial Microstructures page.
Sources: UCSB news release, via EurekAlert!, November 8, 2004; and various other websites
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