Micron diameter particles containing or composed solely of
polystyrene have been reported to become highly
fluorescent shortly after immobilization in a visible optical trap
(488.0 nm). It has been proposed that extensive
regions of conjugation in the polymer backbone are responsible for this
emission. Raman spectroscopic
evidence is described in this report that confirms the presence of
polymer backbone conjugation. In some
experiments Raman signals were enhanced by incorporating silver
nanoparticles into the micron-diameter
polystyrene particles by photoreduction of silver ion. By
monitoring the intensity changes of the C−H and
CC stretching regions while an individual particle is immobilized in
the optical trap, the generation of
extensive conjugation regions can be observed over time. In
addition, the presence of the silver nanoclusters
increased the rate and magnitude of the reactions that lead to
polystyrene conjugation.
Rapid generation of polystyrene conjugation in
individual micron-diameter particles isolated in a visible
wavelength radiation trap is reported. Double-bond formation, as a
result of radical recombination and hydrogen
abstraction, in the backbone of the polymer chain is monitored by
observing the magnitude and duration of
emission from the polymeric particles. These processes, which
ultimately lead to polymer degradation, are
observed to be strongly dependent upon the thermal conductivity and
polarity of the solvent used to suspend
the particles. Doping the polymer with chemical modifiers
containing chromophores in order to reduce
photodegradation is demonstrated to be counterproductive.
Conventional aminopeptidase methods require cell concentrations of approximately 10s to 101°cells/mL and an Incubation period In the labeled substrates of 20 h. In order to obtain the large number of cells required to perform this assay, a 36-48-h growth period must precede the assay. An Improved procedure Is described that combines time-resolved fluorometry and a nondestructive whole cell Immobilization procedure. This method has reduced cell concentrations 80 000-fold from that required for the standard assay, has reduced the room-temperature incubation period from 20 h to 3 min, and has shortened the total turnaround time for the assay from 2.5 days to approximately 3-7 h.At present a major goal of "improved" microbial identification techniques is to reduce the time required for identification. The turnaround time can be broken into two specific elements. The first is the growth period required to isolate
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