Navigation Links
Lollipops and ice fishing: Molecular rulers used to probe nanopores
Date:4/28/2010

Using a pair of exotic techniques including a molecular-scale version of ice fishing, a team of researchers working at the National Institute of Standards and Technology (NIST) have developed methods to measure accurately the length of "nanopores," the miniscule channels found in cell membranes. The "molecular rulers" they describe in a recent paper* could serve as a way to calibrate tailor-made nanoporeswhose diameters on average are nearly 10,000 times smaller than that of a human hairfor a variety of applications such as rapid DNA analysis.

Studies at NIST and other research institutions have shown that a single nanometer-scale pore in a thin membrane can be used as a "miniature analysis laboratory" to detect and characterize individual biological molecules such as DNA or toxins as they pass through or block the passage. Such a system could potentially fit on a single microchip device, for a wide variety of applications. However, making the mini-lab practical requires an accurate definition of the dimensions and structural features of the nanopore.

In new experiments, researchers from NIST and the University of Maryland first built a membranea bilayer sheet of lipid moleculessimilar to that found in animal cells. They "drilled" a pore in it with a protein** designed specifically to penetrate cell membranes. When voltage is applied across the membrane wall, charged molecules such as single-stranded DNA are forced into the nanopore. As the molecule passes into the channel, the ionic current flow is reduced for a time that is proportional to the size of the chain, allowing its length to be easily derived.

If a chain is long enough to reach the narrowest part of the nanoporeknown as the pinch pointthe force of the electrical field behind it will push the molecule on through the rest of the channel. Exploiting this characteristic, the NIST/Maryland team developed a DNA probe method to measure the distances from the openings on each side of the membrane to the pinch point, and in turn, the entire length of the nanopore by adding the two measurements together. The probes consist of DNA strands of known lengths topped on one end by a polymer sphere. The sphere prevents the probe from completely moving through the nanopore while leaving the DNA chain dangling from it free to extend into the channel. If the chain reaches the pinch point, the force that would normally drive a free DNA chain past the junction instead holds the probe in place (since the polymer sphere "locks" it at the other end) and defines the distance to the pinch point. If the chain is shorter than the distance to the pinch point, it will be bounced out of the nanopore, telling researchers that a longer-length chain is needed to measure the distance to the gap.

The NIST/Maryland researchers also developed a second means of measuring the length of the nanopore to confirm the results of the "single lollipop" method. In this system, polymer molecules are allowed to circulate freely in the solution found on the inner side of the membrane. Polymer-capped DNA probes of different lengths are forced one at a time into the nanopore from the opposite side. If the end of a probe's chain is long enough to completely transverse the channel, it will grab hold of a free polymer molecule in solution. This defines the length of the channel.

Additionally, this "ice fishing" method provides insight into the structure of the nanopore. As the DNA chain winds its way through, changes in electrical voltage correspond to the changing shape of the channel. This information can be used to effectively map the passageway.


'/>"/>

Contact: Michael E. Newman
michael.newman@nist.gov
301-975-3025
National Institute of Standards and Technology (NIST)
Source:Eurekalert  

Related biology news :

1. New molecular regulators of hyperthyroidism and goiter
2. Carnegie Mellon scientists investigate initial molecular mechanism that triggers neuronal firing
3. UC health news: molecular pathway may predict chemotherapy effectiveness
4. New molecular clock from LLNL and CDC indicates smallpox evolved earlier than believed
5. Story ideas from Molecular & Cellular Proteomics
6. Lets talk -- new paradigms in the research of the biomolecular composition of water
7. Scientists unveil structure of molecular target of many drugs
8. Potential new therapeutic molecular target to fight cancer
9. NIH selects LIAI for major study on allergy molecular causes and possible treatments
10. Pennsylvania Hospital surgeon receives grant to develop molecular cardiac surgery
11. Leading cause of death in preemies might be controlled by resetting a molecular switch
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
Lollipops and ice fishing: Molecular rulers used to probe nanopores
(Date:9/14/2019)... ... September 12, 2019 , ... ... for drugs, biologics, gene therapies, and consumer health products, today announced that professor ... business. Dr. Schaffer has played an integral advisory role on the gene therapy ...
(Date:9/11/2019)... ... September 10, 2019 , ... Newly released “Dream in ... collaboration that offers a beautiful and thought-provoking journey through five chapters of human ... to Whittaker’s poems and other times, Whittaker wrote to Srinivasan’s paintings. Together, the ...
(Date:8/31/2019)... FRANCISCO (PRWEB) , ... August 30, 2019 , ... ... startup making beautiful, science-backed conception essentials. Natalist empowers consumers in the preconception period ... of essentials to support people each month that are trying to get pregnant. ...
Breaking Biology News(10 mins):
(Date:9/9/2019)... ... September 09, 2019 , ... Visikol CEO Dr. Michael Johnson recently gave a ... best to characterize 3D cell culture models. The inherent problem of characterizing 3D cell ... opaque to image through and therefore traditional wide-field or even confocal microscopy only tells ...
(Date:8/29/2019)... ... August 29, 2019 , ... ... affecting grapevines, a feat they hope will ultimately help protect the multibillion-dollar grape ... several Rochester Institute of Technology faculty and alumni sequenced the microbiome found within ...
(Date:8/25/2019)... ... August 23, 2019 , ... Authors ... status for the scientific research book “Impact of Biofield Treatment on Growth and ... industry as Patchouli. , The book garnered No. 1 status on Amazon ...
(Date:8/14/2019)... ... August 13, 2019 , ... ... prepackaged mobile phases for QC laboratories. After gaining a few significant clients, Lifecycle ... approach into a valued supplier of manufacturing processing solutions, including reagents for tissue ...
Breaking Biology Technology: