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 Figure 2 - The yellow spheres represent vesicles. The surfactant bilayer that forms a hydrophobic barrier is illustrated. |
Dateline: 07/09/2000
Vesicles (Figure 2) are abundant in biological organisms, where they often serve the function of transporting various molecules. They are bubble-like structures composed of a lipid bilayer membrane, which can be created by means of biomolecular self-assembly. Vesicles of diameters ranging from 25 nm to 20 microns can be fabricated in a laboratory with some self-assembly technique. For instance, 25 nm vesicles can be made by sonicating a bilayer membrane at high frequencies, while 20 micron vesicles are produced when a low frequency alternating current is applied to the solution.
Zare et. al. has demonstrated the possiblility of carrying out reactions in vesicles containing attoliter to zeptoliter volumes [3]. Each vesicle can contain as little as one molecule of a reagent. In this case, the reagents were deposited by electroporation or by electrofusion, methods involving application of an electrical pulse to propel charged particles through the solution.
It may seem that that shrinking reaction vessels and using molecular assembly lines could be considered a simple extension of current chemical techniques. However, the discrete nature of nanoscale chemistry requires an adaption of the fundamental principles defined by traditional chemistry. For instance, in a previous article entitled 'quantum biology' it was noted that our statistical method for measuring temperature breaks down at the nanoscale. The current definition of temperature is especially meaningless in systems that are not at equilibrium, such as a biological cell. Indeed, the term 'equilibrium' itself loses meaning (breaks down) at the nanoscale due to its statistical definition. In order to study and design nanoscale systems, one cannot rely only on macroscale statistics that have proven invaluable to nearly all fields of science. Since temperature is one of the 7 fundamental units upon which other units rely, it is becoming necessary for nano-scientists to tweak this and other units to better reflect nanoscale phenomena.
Next Page Nanoscale Temperature
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[3] Daniel T. Chiu, Clyde F. Wilson, Frida RyttsŽn, Anette Stršmberg, Cecilia Farre, Anders Karlsson, Sture Nordholm, Anuj Gaggar, Biren P. Modi, Alexander Moscho, Roberto A. Garza-L—pez, Owe Orwar, Richard N. Zare, "Chemical Transformations in Individual Ultrasmall Biomimetic Containers" Science 1999 283: 1892-1895. Abstract.