Featured Research

from universities, journals, and other organizations

What light through yonder tiny window breaks? Researchers optimize photoluminescent probes to study dna and more

Date:
September 6, 2012
Source:
Rice University
Summary:
Sorting good data from bad is critical when analyzing microscopic structures like cells and their contents, according to researchers. The trick is to find the right window of time through which to look. A new paper offers a methodology to optimize the sensitivity of photoluminescent probes using time-resolved spectroscopy. Researchers found their technique gave results nearly twice as good as standard fluorescence spectroscopy does when they probed for specific DNA sequences.

Researchers at Rice are working to optimize results from photoluminescent probes essential to the study of microscopic structures like cells, proteins and DNA. The technique doubled the efficiency of a hairpin-shaped probe called a molecular beacon (at left) to find a specific DNA sequence by maximizing the amount of signal pulled from the background noise.
Credit: Marti Group/Rice University

Sorting good data from bad is critical when analyzing microscopic structures like cells and their contents, according to researchers at Rice University. The trick is to find the right window of time through which to look.

A new paper by the Rice lab of Angel Martí, an assistant professor of chemistry and bioengineering, offers a methodology to optimize the sensitivity of photoluminescent probes using time-resolved spectroscopy. Martí and co-author Kewei Huang, a graduate student in his group, found their technique gave results nearly twice as good as standard fluorescence spectroscopy does when they probed for specific DNA sequences.

Their results were reported recently in the American Chemical Society journal Analytical Chemistry.

In spectroscopy, chemicals and materials from proteins to nanotubes can be identified and tracked by their fluorescence -- the light they return when excited by an input of energy, usually from a laser. In the kind of targeted spectroscopy practiced by Martí and his colleagues, a luminescent probe called a molecular beacon is designed to attach to a target like a DNA sequence and then light up.

Improving a probe's ability to detect ever smaller and harder-to-find targets is important to biologists, engineers and chemists who commonly work on the molecular scale to analyze cell structures, track disease or design tiny machines.

One problem, Martí said, has been that even in an experiment lasting a fraction of a second, a spectrometer can return too much information and obscure the data researchers actually want. "In standard fluorescence spectroscopy, you see noise that overlaps with the signal from your probe, the scattering from your solution or cuvettes, plus the noise from the detector," he said. The saving grace, he said, is that not all those signals last the same amount of time.

Time-resolved spectroscopy provides part of the answer, Martí said. Compared with standard spectroscopy, it's like taking a film instead of a snapshot. "We create a kind of movie that allows us to see a specific moment in the process where photoluminescence is occurring. Then we can filter out the shadows that obscure the measurement or spectra we're looking for," he said.

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, Martí 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.

Martí 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, Martí and Huang tested ruthenium- and iridium-based light-switching probes under standard fluorescent and time-resolved spectroscopy. The hairpin-shaped probes' middles are designed to attach to a specific DNA sequence, while the ends are of opposite natures. One carries the fluorophore (iridium or ruthenium), the other a chemical quencher that keeps the fluorescence in check until the probe latches onto the DNA. When that happens, the fluorophore and the quencher are pulled apart and the probe lights up.

The individual signal is a flash too tiny and quick for the naked eye to see. "But our instruments can," Martí said.

"We're trying to show that you can use time-resolved spectroscopy for many applications, but to use it in the right way, you have to do some analysis first," he said. "If you do it in the correct way, then it's a very powerful technique."

The research was supported by the Welch Foundation and the National Science Foundation.


Story Source:

The above story is based on materials provided by Rice University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Kewei Huang, Angel A. Martí. Optimizing the Sensitivity of Photoluminescent Probes Using Time-Resolved Spectroscopy: A Molecular Beacon Case Study. Analytical Chemistry, 2012; 120830130430009 DOI: 10.1021/ac3019894

Cite This Page:

Rice University. "What light through yonder tiny window breaks? Researchers optimize photoluminescent probes to study dna and more." ScienceDaily. ScienceDaily, 6 September 2012. <www.sciencedaily.com/releases/2012/09/120906131408.htm>.
Rice University. (2012, September 6). What light through yonder tiny window breaks? Researchers optimize photoluminescent probes to study dna and more. ScienceDaily. Retrieved April 23, 2014 from www.sciencedaily.com/releases/2012/09/120906131408.htm
Rice University. "What light through yonder tiny window breaks? Researchers optimize photoluminescent probes to study dna and more." ScienceDaily. www.sciencedaily.com/releases/2012/09/120906131408.htm (accessed April 23, 2014).

Share This



More Matter & Energy News

Wednesday, April 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Is North Korea Planning Nuclear Test #4?

Is North Korea Planning Nuclear Test #4?

Newsy (Apr. 22, 2014) — South Korean officials say North Korea is preparing to conduct another nuclear test, but is Pyongyang just bluffing this time? Video provided by Newsy
Powered by NewsLook.com
China Falls for 4x4s at Beijing Auto Show

China Falls for 4x4s at Beijing Auto Show

AFP (Apr. 22, 2014) — The urban 4x4 is the latest must-have for Chinese drivers, whose conversion to the cult of the SUV is the talking point of this year's Beijing auto show. Duration: 00:40 Video provided by AFP
Powered by NewsLook.com
Lytro Introduces 'Illum,' A Professional Light-Field Camera

Lytro Introduces 'Illum,' A Professional Light-Field Camera

Newsy (Apr. 22, 2014) — The light-field photography engineers at Lytro unveiled their next innovation: a professional DSLR-like camera called "Illum." Video provided by Newsy
Powered by NewsLook.com
3 Reasons Why Harley Davidson Is Selling Tons of Epic Hogs

3 Reasons Why Harley Davidson Is Selling Tons of Epic Hogs

TheStreet (Apr. 22, 2014) — Sales of motorcycles have continued to ride back from the depths of hell known as the Great Recession. Excluding scooters, sales of motorcycles increased 3% in 2013. In units, however, at 465,000 sold last year, the total remained about 50% below the peak hit in 2007. Industry leader Harley Davidson’s shareholders have benefited both by the industry recovery and positive headlines emanating from the company. Belus Capital Advisors CEO Brian Sozzi takes you beyond the headlines of the motorcycle maker. Video provided by TheStreet
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins