“DNA’s helical structure implies that twisting and stretching should be coupled, hence the prediction that DNA should unwind when stretched,” said biophysicist Carlos Bustamante, who led this experiment. “That is why it was such surprise when we directly measured twist-stretch coupling to find instead DNA overwinds when stretched. The DNA molecule, when studied at close range, continues to surprise us!”
Bustamante is a leading authority on the use of single-molecule visualization and manipulation techniques to study the dynamics, structure and kinetics of molecular motors and nucleo-protein assemblies. He holds joint appointments with Berkeley Lab’s Physical Biosciences Division and UC Berkeley’s Departments of Molecular & Cell Biology, Physics, and Chemistry. He is also a Howard Hughes Medical Institute (HHMI) investigator.
The results of this study are reported in the journal Nature, in a letter entitled DNA Overwinds When Stretched, which is now available on-line. Coauthoring this letter with Bustamante were Jeff Gore, Zev Bryant, Marcelo Nöllmann, Mai Le and Nicholas Cozzarelli.
The magic of DNA replication and the transcription of genetic information into the production of proteins depends upon the mechanical properties of the double helix. This is why understanding these mechanical properties has been a scientific priority since the double-helix was first discovered by Watson and Crick more than 50 years ago. Bustamante has been one of the foremost pioneers in this area of research. More than a decade ago, he and his research group tethered DNA molecules to tiny beads and measured their elasticity. Among the many breakthroughs he and his group have achieved is the development of the technique called “rotor bead tracking.”
In rotor bead tracking, a single DNA molecule is anchored to a surface and a magnetized bead is attached to the free end. A point along the double-helix is then biochemically “nicked” to create a single strand of DNA that acts as a free swivel. Immediately below this nick, a plastic bead is attached to the DNA to serve as a “rotor” that will spin in response to torque. Magnets are used to manipulate the magnetized bead, providing a measured and highly controlled amount of tension to stretch the DNA molecule. With the use of a fluorescent coating, the subsequent spinning of the rotor bead in response to the stretching can be recorded.
“As this system is stretched, the elastic rod decreases in diameter,” said Bustamante. “This enables the outer wire to wrap a larger number of times over the length of the rod.”
The twist-stretch coupling results demonstrated by Bustamante and his collaborators holds important implications for how DNA-binding proteins are able to recognize their target sites along the helix. These proteins are known to bend, wrap, loop and twist DNA. Now it has been shown that they can achieve their goals by simultaneously stretching and overwinding a DNA molecule, or by compressing and underwinding it.
“We believe that our work sheds new light on an old and important problem,” said Bustamante, “and that, in addition to improving our understanding of DNA/protein interactions, it will also have implications in nanotechnology. For example, the DNA molecule might provide the energy to power future nanomotors.”
Berkeley Lab is a U.S. Department of Energy national laboratory located in Berkeley, California. It conducts unclassified scientific research and is managed by the University of California.
Lynn Yarris | EurekAlert!
Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery
20.01.2017 | GSI Helmholtzzentrum für Schwerionenforschung GmbH
Seeking structure with metagenome sequences
20.01.2017 | DOE/Joint Genome Institute
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...
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
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...
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...
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...
19.01.2017 | Event News
10.01.2017 | Event News
09.01.2017 | Event News
20.01.2017 | Awards Funding
20.01.2017 | Materials Sciences
20.01.2017 | Life Sciences