Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Salt controls size of DNA structures, could improve gene therapy

30.07.2003


Georgia Tech Associate Professor Nicholas Hud (left) and Ph.D. student Christine Conwell -- along with Ph.D. student Igor Vilfan (not shown) -- have made a significant advance in controlling the size of DNA toroids. The finding could improve the efficiency of gene delivery for medical treatment and disease prevention
Georgia Tech Photo: Gary Meek


Scientists are seeking to understand the natural mechanism of DNA condensation into nanostructures - in particular, toroids. Toroids resemble tightly wound garden hoses. Shown here is a micrograph of a DNA toroid.
Image Copyright: Proceedings of the National Academy of Sciences


Researchers have found they can control the size of densely packed DNA structures by changing the salt concentration in solutions containing DNA. The finding could improve the efficiency of gene delivery for medical treatment and disease prevention.

Scientists are seeking to understand the natural mechanism of DNA condensation into nanostructures -- in particular, toroids, which look like tightly wound garden hoses. Densely packed DNA is nature’s efficient way of transporting genetic information, done particularly well by sperm cells and viruses.

Researchers want to mimic this process to improve DNA delivery for gene therapy and DNA-based vaccines, but they face many challenges in the laboratory where DNA in solution typically exists in an extended, rather than condensed state. Scientists have been able to cause DNA to condense into toroids by adding positively charged molecules to samples, but they have had difficulty finding the right molecules to achieve consistent, optimal toroid sizes of less than 50 nanometers.



However, scientists at Georgia Institute of Technology have made a significant advance in controlling the size of DNA toroids. In the July 18, 2003 online issue of the journal Proceedings of the National Academy of Sciences (PNAS), they report that reducing salt concentrations below normal laboratory solution levels shrinks both the diameter and thickness of DNA toroids. This finding resulted from a combined investigation of how static DNA loops and solution conditions might be used to control toroid dimensions.

"But even without static loops present, DNA produces smaller toroids if you reduce the salt concentration," said Nicholas Hud, an associate professor of biochemistry who is leading the study funded by the National Institutes of Health. "We found a systematic relationship between reducing salt and reducing toroid size. It is surprising that such a study was not previously done because salt concentration is such a fundamental parameter in studying molecules in solution, particularly such highly charged molecules as DNA."

Protocols for preparing DNA for delivery to cells often call for salt conditions that differ from those DNA encounters when injected into body tissues, Hud noted. "If you change the salt conditions during DNA delivery, it will change particle size and have a dramatic effect on the efficiency of gene delivery," he added. "This could explain why some researchers aren’t getting as good a rate of transfection (the incorporation of DNA into a cell) as they should."

In the study reported in PNAS, Hud and his Ph.D. students Christine Conwell and Igor Vilfan also describe using the positively charged, inorganic molecule hexammine cobalt (III) to condense a DNA molecule containing a specially designed sequence. The synthetic sequence causes a region of the DNA molecule to bend into two loops of 25 nanometers each in diameter. In other words, these nanoscale loops were "programmed" into the DNA sequence.

Hud theorized years ago that the spontaneous formation of loops along DNA is the first step necessary for toroid formation, and a key factor in determining toroid size, he said.

"Now, we’ve made these loops always present there," Hud explained. "When we add positively charged molecules that bind to the DNA, the loops provide a built-in starting point for DNA condensation. The loops also act as a template upon which the rest of the DNA rolls up to form a toroid. The toroid forms because the positively charged molecules make DNA want to stick to itself…. and we found that our static loops reduce DNA particle size and tighten particle distribution."

Hud describes as serendipitous the additional finding that lowering the salt concentration in DNA solution also reduces the size of toroids. Together, these results helped Hud’s team develop models for DNA toroid formation. The researchers’ data can now serve as a test for theoretical models of DNA condensation, they say.

Meanwhile, Hud’s team is exploring how the order in which they add salts to DNA solutions affects particle size and shape -- whether salts should be added before or after the DNA condensation process is prompted by positively charged molecules.

"By studying the fundamental process of DNA condensation we hope to determine all the factors that help produce particles of smaller size and narrower size distribution. The combined effects of these factors should help us to produce the optimal particles for gene delivery," Hud added.

He believes a systematic approach to the high-stakes goal of developing an efficient, artificial gene delivery method will pay off.

"There have been a lot of attempts to improve DNA delivery by simply mixing molecules and empirically testing to determine their efficiency," Hud said. "But DNA condensates are difficult to understand…. We might be missing something in our information about what’s happening from the lab bench to the delivery of DNA to cells. We want to understand the nature of DNA particles all the way from the test tube to the cell."

Technical Contact: Nick Hud, +1-404-385-1162, hud@chemistry.gatech.edu

Jane Sanders | Georgia Institute of Technology
Further information:
http://gtresearchnews.gatech.edu

More articles from Life Sciences:

nachricht Link Discovered between Immune System, Brain Structure and Memory
26.04.2017 | Universität Basel

nachricht Researchers develop eco-friendly, 4-in-1 catalyst
25.04.2017 | Brown University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

Scientist invents way to trigger artificial photosynthesis to clean air

26.04.2017 | Materials Sciences

Ammonium nitrogen input increases the synthesis of anticarcinogenic compounds in broccoli

26.04.2017 | Agricultural and Forestry Science

SwRI-led team discovers lull in Mars' giant impact history

26.04.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>