With samples loaded into the spectrometer, researchers yell "Action!" by firing a laser that excites the target. In an edit of the resulting "movie" (which can be done in real time by the spectrometer), they chop off the front and back to narrow the data set to a range that might last only 80-billionths of a second, when the probe signal is strongest and the background signals are absent.
But it's critical to know just the right window of time to look at, Mart said. That's where the Rice methodology removes any uncertainty. They let researchers analyze all the factors, such as the emission intensity and decay of the specific probe with and without the target and the anticipated level of background noise. The experiment can then maximize the signal-to-background noise ratio. The technique works even with probes that are less than optimal, he said.
In combination with a technique called fluorescence lifetime microscopy, the Rice calculations may improve results from other diagnostic tools that gather data over time, such as magnetic resonance imaging machines used by hospitals.
Mart said the equations were the common-sense results of years of working with fluorescent spectroscopy. But, he said, when he looked for materials to help teach his students how to use time-resolved techniques to improve probes' resolution, he found none.
"I thought there must be some publication out there that would describe the tools we use, but there weren't any," he said. "So we've had to write them."
To prove their method, Mart and Huang tested ruthenium- and iridium-based light-switching probes under standard fluorescent and time-resolved spectroscopy. T
|Contact: David Ruth|