Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Rice physicists help unravel mystery of repetitive DNA segments

07.12.2010
With new tools that can grab individual strands of DNA and stretch them like rubber bands, Rice University scientists are working to unravel a mystery of modern genomics. Their latest findings, which appear in Physical Review Letters, offer new clues about the physical makeup of odd segments of DNA that have just one DNA base, adenine, repeated dozens of times in a row.

These mysterious "poly(dA) repeats" are sprinkled throughout the human genome. Scientists have also found them in the genomes of animals, plants and other species over the past decade. But researchers do not know why they are there, what function they perform or why they occur only with the DNA base adenine and not the other three DNA bases -- cytosine, guanine and thymine.

"Previous investigations of poly(dA) have suggested that adenine bases stack in a very uniform way," said Ching-Hwa Kiang, a co-author of the new study and assistant professor of physics and astronomy at Rice. "Our investigation focused on what happens when single strands of poly(dA) were stretched and these stacks were pulled apart."

Kiang's research group specializes in studying the physical and mechanical properties of proteins and nucleic acids, and their primary tool is one of the mainstays of nanotechnology research -- the atomic force microscope, or AFM. The business end of an AFM is like a tiny phonograph needle. The tip of the needle is no more than a few atoms wide, and the needle is at the end of an arm that bobs up and down over the surface of what is being measured. While nanotechnologists use the device to measure the thickness of samples, Kiang's group uses it in a different way.

To begin her experiments, Kiang first places a thin coating of the proteins she wishes to study on a flat surface. This is placed under the AFM arm so the bobbing AFM needle can dip down and grab the ends of one of the proteins. As the arm retracts, it unravels the protein.

All proteins fold into a characteristic shape. Like tiny springs, they remain in this compact "lowest energy" state unless they are pried apart.

The new study on poly(dA) was conducted by Kiang, Rice graduate student Wuen-shiu Chen and colleagues at Rice and National Chung Hsing University (NCHU) in Taiwan. The team discovered that poly(dA) behaves differently depending upon the speed with which it is stretched. When the AFM bobbed rapidly, the poly(dA) segments behaved like any other segment of single-stranded DNA. But when the AFM motion was slowed, the team found that the amount of force required to stretch the poly(dA) changed. At two particular locations, the strand lengthened for a short distance without any additional force at all.

"Typically, single strands of DNA behave like a rubber band: The resistance increases as they stretch, meaning you have to pull harder and harder to continue stretching them," Kiang said. "With poly(dA), we found these two points where that doesn't apply. It's as if you have to pull harder and harder, and then for a brief time, the band stretches with no additional force whatsoever."

Kiang said the exact causes and implications of the phenomenon are unclear. But scientists know that double-stranded DNA must be pried apart at discrete locations so that the cell's machinery can read the genetic code and convert it into proteins. There has been some speculation that the adenine repeats play a role in ordering genomic information; Kiang said the new findings raise even more questions about the role the repeats might play in gene regulation and genome packaging and how they might be potential targets for cancer drugs.

The research was supported by the National Science Foundation, the Welch Foundation and the Rice Institute of Biosciences and Bioengineering's Hamill Innovation Fund. Study co-authors include Rice undergraduate students Zephan Chen and Ashton Gooding, exchange graduate student Wei-Hung Chen from NCHU and NCHU Professor of Chemistry Kuan-Jiuh Lin.

Jade Boyd | EurekAlert!
Further information:
http://www.rice.edu

More articles from Physics and Astronomy:

nachricht SF State astronomer searches for signs of life on Wolf 1061 exoplanet
20.01.2017 | San Francisco State University

nachricht Molecule flash mob
19.01.2017 | Technische Universität Wien

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Helmholtz International Fellow Award for Sarah Amalia Teichmann

20.01.2017 | Awards Funding

An innovative high-performance material: biofibers made from green lacewing silk

20.01.2017 | Materials Sciences

Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery

20.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>