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Monday, 31 January 2005
Researchers Discover Living Nanoscale "Necklace"Daniel J. Needleman, Miguel A. Ojeda-Lopez, Uri Raviv, Herbert P. Miller, Leslie Wilson and Cyrus R. Safinya, University of California, Santa Barbara
In an interdisciplinary endeavor at the University of California Santa Barbara
(UCSB), a team of researchers in physics and biology have made a discovery at
the nanoscale level that could be instrumental in the production of
miniaturized materials with many applications. Dubbed a "living necklace," the
unexpected finding could influence the development of vehicles for chemical,
drug, and gene delivery, enzyme encapsulation systems and biosensors, circuitry
components, as well as templates for nanosized wires and optical materials.
Using bovine brain tissue, scientists studied nanometer-scale hollow cylinders
derived from cell cytoskeleton, microtubules, to understand the mechanisms
leading to their assembly and shape. 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 to aiding in the transport of neurotransmitters.
However, the mechanism of their assembly within an organism has been poorly
understood. In a recent paper in the Proceedings of the National Academy of
Sciences, researchers report the discovery of a new type of higher order
assembly of microtubules. Unexpectedly, the scientists found that small,
spherical divalent cations caused microtubules to assemble into a "necklace."
They discovered distinct linear, branched and loop shaped necklaces. From a
formal theoretical physics perspective, the living necklace phase is the first
experimental realization of a new type of membrane where the long microtubule
molecules are oriented in the same direction but can diffuse within the living
membrane. Researchers explained that the living necklace bundle is highly
dynamic and that thermal fluctuations will cause it to change shape. Based on
both the tight bundle and living necklace phases, the scientists envision broad
applications from nanomaterials with controlled optical properties to drug or
gene carriers (using the assemblies encased by a lipid bilayer where each
nanotube may contain a distinct chemical). This work was performed using SSRL
Beam Line 4-2 as well as the electron and optical microscopy at UCSB.
The research was supported by the National Science Foundation, the National
Institutes of Health, and the Department of Energy.
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