Scientists manipulate molecules inside living cells with temperature gradients

September 30, 2014 by Lisa Zyga, Phys.org feature
Set-up of the thermophoresis technique. Heating is provided from below by an IR laser. The molecules move along the temperature gradient, indicated by arrows. Credit: Reichl and Braun. ©2014 American Chemical Society

(Phys.org) —The ability to make measurements of the biomolecular interactions that occur inside living cells is essential for understanding complex biological processes. But probing the inside of living cells without damaging them is a challenge. The cell membrane shields electrical fields, prohibiting the use of electrophoresis, a technique that is commonly used to analyze biological samples in a variety of areas outside living cells.

Now in a new paper, researchers have demonstrated for the first time that thermophoresis—the movement of molecules due to a rather than an electric field—can be used to measure the movement of DNA and other molecules inside living cells. The paper, by Maren R. Reichl and Dieter Braun at the Ludwig Maximilian University of Munich, is published in a recent issue of The Journal of the American Chemical Society.

"Our work shows that the measurement of thermophoresis in living cells is possible—moreover, in parallel across the cell and not at one single point," Braun told Phys.org.

In the new technique, a temperature gradient is applied across a cell by an infrared laser. Fluorescently marked molecules inside the cell move along this temperature gradient from hotter to colder regions. A camera can record this thermophoretic movement, with every camera pixel measuring thermophoresis simultaneously and independently. The technique can be performed in the natural environment of cells in vivo.

The researchers demonstrated the use of thermophoresis measurements of DNA in the cytoplasm of living cells. Interestingly, the results revealed that DNA movement in the cytoplasm is slowed down, probably due to molecular crowding. In addition to measuring the movement of DNA, the thermophoresis technique could also measure the movement of proteins, pharmaceutical components, and other molecules in cells as long as they can move through the cytoplasm. Ribosomes, for example, are so large and bound to the endoplasmic reticulum that they cannot easily diffuse through the cytoplasm, making them poor candidates for thermophoresis.

Thermophoresis measurements of DNA and the dye molecule BCECF in the cytoplasm of living cells. Credit: Reichl and Braun. ©2014 American Chemical Society

One way that thermophoresis inside living cells can be used is to measure the binding affinities of molecules. As the scientists explain, the binding of a fluorescently marked molecule such as DNA or a protein leads to a change in the thermophoretic depletion strength. Binding affinities can reveal more detailed information about the interactions of these molecules.

"The dream would be to record binding affinities in living , i.e., translating the award-winning microscale thermophoresis (MST) technique of our startup company Nanotemper into ," Braun said. "However, the measurement protocol is not yet robust against the shape of the cell, so some more tricks to make it work will be necessary. But we are optimistic—experimental tricks are our specialty."

Explore further: Researchers model how migration of DNA molecules is affected by charge, salt species, and salt concentration

More information: Maren R. Reichl and Dieter Braun. "Thermophoretic Manipulation of Molecules inside Living Cells." Journal of the American Chemical Society. DOI: 10.1021/ja506169b

Related Stories

A hot road to new drugs

February 24, 2010

The quest for new drugs is generally a lengthy and costly undertaking. German researchers of Ludwig-Maximilians-Universitaet in Munich have now come up with a simpler and more efficient way of going about it. Not only pharmaceutical ...

Live from the scene: Biochemistry in action

August 8, 2011

Researchers can now watch molecules move in living cells, literally millisecond by millisecond, thanks to a new microscope developed by scientists at the European Molecular Biology Laboratory (EMBL) in Heidelberg, Germany. ...

DNA double helix measurements

May 15, 2014

Researchers at the National Physical Laboratory (NPL) and the London Centre for Nanotechnology (LCN) have determined the structure of DNA from measurements on a single molecule using atomic force microscopy (AFM), and found ...

Recommended for you

A way to make cleaner metal-free perovskites at low cost

July 13, 2018

A team of researchers at Southeast University in China has found a way to make metal-free perovskites in a useable form. In their paper published in the journal Science, the group describes their technique and how well it ...

The secret sulfate code that lets the bad Tau in

July 13, 2018

Vampires can turn humans into vampires, but to enter a human's house, they must be invited in. Researchers at the UT Southwestern Medical Center, writing in the Journal of Biological Chemistry, have uncovered details of how ...

Bioengineers create pathway to personalized medicine

July 12, 2018

Engineering cellular biology, minus the actual cell, is a growing area of interest in biotechnology and synthetic biology. It's known as cell-free protein synthesis, or CFPS, and it has potential to provide sustainable ways ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.