The ability of fluorescence microscopy to study labeled structures like cells has now been empowered to deliver greater spatial and temporal resolutions that were not possible before, thanks to a new method developed by University of Illinois researcher Gabriel Popescu and Ru Wang from his lab. Using this method, they were able to study the critical process of cell transport dynamics at multiple spatial and temporal scales and reveal, for the first time, properties of diffusive and directed motion transport in living cells.
Popescu leads the Quantitative Light Imaging Laboratory at Illinois' Beckman Institute, while Wang of the lab is first author on the paper reporting the method in Physical Review Letters. The new approach, called dispersion-relation fluorescence spectroscopy (DFS), labels molecules of interest with a fluorophore whose motion, the researchers write, "gives rise to spontaneous fluorescence intensity fluctuations that are analyzed to quantify the governing mass transport dynamics. These data are characterized by the effective dispersion relation."
That ability to study the directed and diffusive transport characteristics of cellular dispersion through a wide range of temporal and spatial scales is more comprehensive than using just fluorescence microscopy. It provides more information than existing methods, such as fluorescence correlation spectroscopy (FCS), which is widely used for studying molecular transport and diffusion coefficients at a fixed spatial scale.
This study used DFS to focus on the cell cytoskeleton subunit actin and found that "the fluorescently labeled actin cytoskeleton exhibits active transport motion along a direction parallel to the fibers and diffusive on the perpendicular direction." Those results, the researchers said, describe at what scale and when directed versus diffusive motion is taking place in the cell.
"So for the first time we think we're able to tell those apart and the spatial scales at which each is dominant," Popescu said.
"Some traditional methods are good at measuring local transport and some are good at measuring the larger scales," Wang said. "Our method gives a fuller view of what happens inside the cell, to the patterns of traffic. So we can look at both the local scale and at larger scales, and ask at which scale the motion transitions from random to directed motion."
Popescu said the multiplicity of scales the method offers over techniques like fluorescence correlated spectroscopy is key. Such knowledge would be valuable for researchers interested in the basic science of cellular dynamics, as well as those working in biomedical research, such as in analysis of a drug's effect on the body. This technique can be used with current fluorescence microscopy methods.
"I think that the beauty of this method is that you can use a commercial fluorescent microscope that is found everywhere to collect and analyze data in a very simple way," Wang said. "You don't need complicated expertise. Everyone can use it."
The method relies on taking time-resolved sequential data from fluorescent spectroscopic microscopy images and transforming them using the Fourier transform. This computational method enables easier understanding of the image data, providing a different representation of the image. Taking advantage of the respective frequency domains of patterns in the data, as this method does, is especially useful for trying to understand cellular dynamics like transport.
"So for the first time we saw this universal transport behavior in a living system: a clear combination of diffusive transport, like Brownian motion, and directed, deterministic transport," Popescu said. "As a general trend, we found that diffusion is dominant at short scales and directed transport at large distances."
Beckman Institute for Advanced Science and Technology: http://www.beckman.uiuc.edu/
This press release was posted to serve as a topic for discussion. Please comment below. We try our best to only post press releases that are associated with peer reviewed scientific literature. Critical discussions of the research are appreciated. If you need help finding a link to the original article, please contact us on twitter or via e-mail.
Sheets of programmable matter can be made to pop into complex 3D shapes 100 times taller than their original thickness when heated, and could find uses in medicine
A particle physics student has used his downtime to build a Lego model of the world's most powerful particle accelerator, the Large Hadron Collider (LHC), and is now lobbying the toy company to take it to market.
Get the full the story behind a $761 jar of peanut butter and other exorbitantly priced everyday objects used by scientists
Satellite imagery shows 20 new craters around holes discovered last year in Siberia
Young maths whizz from Iran uses simple equations to paint stunning images that bizarrely look like marine objects, and makes a fractal Africa
A new breed of the hyper-accurate clocks could help scientists detect the elusive ripples in space-time faster and cheaper
Replacing the spark plugs in engines with lasers could lead to more complete fuel combustion and greener cars
After a two-year hiatus, the Large Hadron Collider will restart soon, twice as strong and with some "dark" mysteries to unlock
Global antibiotic resistance is imperilling our existence. We need clever ways to find new bug-beating drugs
If dark matter turns out to interact with photons, its glow would be visible at the edges of spiral galaxies – now we just have to find it