Nanotechnology Now







Heifer International

Wikipedia Affiliate Button


DHgate

Home > Press > Rice physicists help unravel mystery of repetitive DNA segments

Abstract:
Scientists gather clues by measuring forces needed to stretch single strands of DNA

Rice physicists help unravel mystery of repetitive DNA segments

Houston, TX | Posted on December 8th, 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.

####

About Rice University
Located in Houston, Rice University is consistently ranked one of America's best teaching and research universities. Known for its "unconventional wisdom," Rice is distinguished by its: size -- 3,279 undergraduates and 2,277 graduate students; selectivity -- 12 applicants for each place in the freshman class; resources -- an undergraduate student-to-faculty ratio of 5-to-1; sixth largest endowment per student among American private research universities; residential college system, which builds communities that are both close-knit and diverse; and collaborative culture, which crosses disciplines, integrates teaching and research, and intermingles undergraduate and graduate work.

For more information, please click here

Contacts:
Jade Boyd
713-348-6778

Copyright © Rice University

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

SEFCU, SUNY Poly CNSE Announce Winning Student-Led Teams in the 6th Annual $500,000 New York Business Plan Competition April 25th, 2015

Northwestern scientists develop first liquid nanolaser: Technology could lead to new way of doing 'lab on a chip' medical diagnostics April 25th, 2015

Nanotech-enabled moisturizer speeds healing of diabetic skin wounds: Spherical nucleic acids silence gene that interferes with wound healing April 24th, 2015

Fast and accurate 3-D imaging technique to track optically trapped particles April 24th, 2015

Govt.-Legislation/Regulation/Funding/Policy

SEFCU, SUNY Poly CNSE Announce Winning Student-Led Teams in the 6th Annual $500,000 New York Business Plan Competition April 25th, 2015

Northwestern scientists develop first liquid nanolaser: Technology could lead to new way of doing 'lab on a chip' medical diagnostics April 25th, 2015

ORNL reports method that takes quantum sensing to new level April 23rd, 2015

Electron spin brings order to high entropy alloys April 23rd, 2015

Academic/Education

SEFCU, SUNY Poly CNSE Announce Winning Student-Led Teams in the 6th Annual $500,000 New York Business Plan Competition April 25th, 2015

Iranian Female Professor Awarded UNESCO Medal in Nanoscience April 20th, 2015

JPK reports on the use of the NanoWizardŽ 3 AFM system at the Hebrew University of Jerusalem April 14th, 2015

UK National Graphene Institute Selects Bruker as Official Partner: World-Leading Graphene Research Facility Purchases Multiple Bruker AFMs April 7th, 2015

Nanomedicine

Northwestern scientists develop first liquid nanolaser: Technology could lead to new way of doing 'lab on a chip' medical diagnostics April 25th, 2015

Nanotech-enabled moisturizer speeds healing of diabetic skin wounds: Spherical nucleic acids silence gene that interferes with wound healing April 24th, 2015

Fast and accurate 3-D imaging technique to track optically trapped particles April 24th, 2015

A silver lining: UCSB researchers cradle silver nanoclusters inside synthetic DNA to create a programmed, tunable fluorescent array April 23rd, 2015

Announcements

SEFCU, SUNY Poly CNSE Announce Winning Student-Led Teams in the 6th Annual $500,000 New York Business Plan Competition April 25th, 2015

Northwestern scientists develop first liquid nanolaser: Technology could lead to new way of doing 'lab on a chip' medical diagnostics April 25th, 2015

Nanotech-enabled moisturizer speeds healing of diabetic skin wounds: Spherical nucleic acids silence gene that interferes with wound healing April 24th, 2015

Fast and accurate 3-D imaging technique to track optically trapped particles April 24th, 2015

Tools

Fast and accurate 3-D imaging technique to track optically trapped particles April 24th, 2015

ORNL reports method that takes quantum sensing to new level April 23rd, 2015

Quantum 'paparazzi' film photons in the act of pairing up April 22nd, 2015

Richards-Kortum elected to American Academy of Arts and Sciences: April 22nd, 2015

Nanobiotechnology

A silver lining: UCSB researchers cradle silver nanoclusters inside synthetic DNA to create a programmed, tunable fluorescent array April 23rd, 2015

Scientists Use Nanoscale Building Blocks and DNA 'Glue' to Shape 3D Superlattices: New approach to designing ordered composite materials for possible energy applications April 23rd, 2015

UCLA nanoscientists are first to model atomic structures of three bacterial nanomachines: Cryo electron microscope enables scientists to explore the frontiers of targeted antibiotics April 21st, 2015

Rafts on the cell membrane: Researchers from TU Wien (Vienna) shed light on a big secret of cell membranes: The 'lipid rafts', which have been believed to move within the cell membrane, do not really exist April 21st, 2015

NanoNews-Digest
The latest news from around the world, FREE




  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More










ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project