NIST Tech Beat - June 16, 2009

Biophysicists long for an ideal material—something more structured and less sticky than a standard glass surface—to anchor and position individual biomolecules. Gold is an alluring possibility, with its simple chemistry and the ease with which it can be patterned. Unfortunately, gold also tends to be sticky and can be melted by lasers. Now, biophysicists at JILA have made gold more precious than ever—at least as a research tool—by creating nonstick gold surfaces and laser-safe gold nanoposts, a potential boon to laser trapping of biomolecules.

JILA is a joint institute of the National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder.

JILA’s successful use of gold in optical-trapping experiments, reported in Nano Letters,* could lead to a 10-fold increase in numbers of single molecules studied in certain assays, from roughly five to 50 per day, according to group leader Tom Perkins of NIST. The ability to carry out more experiments with greater precision will lead to new insights, such as uncovering diversity in seemingly identical molecules, and enhance NIST’s ability to carry out mission work, such as reproducing and verifying piconewton-scale force measurements using DNA, Perkins says. (A one-kilogram mass on the Earth’s surface exerts a force of roughly 10 newtons. A piconewton is 0.000 000 000 001 newtons. See “JILA Finds Flaw in Model Describing DNA Elasticity” NIST Tech Beat, Sept. 13, 2007.)

Perkins and other biophysicists use laser beams to precisely manipulate, track and measure molecules like DNA, which typically have one end bonded to a surface and the other end attached to a micron-sized bead that acts as a “handle” for the laser. Until now, creating the platform for such experiments has generally involved nonspecifically absorbing fragile molecules onto a sticky glass surface, producing random spacing and sometimes destroying biological activity. “It’s like dropping a car onto a road from 100 feet up and hoping it will land tires down. If the molecule lands in the wrong orientation, it won’t be active or, worse, it will only partially work,” Perkins says.

Ideally, scientists want to attach biomolecules in an optimal pattern on an otherwise nonstick surface. Gold posts are easy to lay down in desired patterns at the nanometer scale. Perkins’ group attached the DNA to the gold with sulfur-based chemical units called thiols (widely used in nanotechnology), an approach that is mechanically stronger than the protein-based bonding techniques typically used in biology. The JILA scientists used six thiol bonds instead of just one between the DNA and the gold posts. These bonds were mechanically strong enough to withstand high-force laser trapping and chemically robust enough to allow the JILA team to coat the unreacted gold on each nanopost with a polymer cushion, which eliminated undesired sticking. “Now you can anchor DNA to gold and keep the rest of the gold very nonstick,” Perkins says.

Moreover, the gold nanoposts were small enough—with diameters of 100 to 500 nanometers and a height of 20 nanometers—that the scientists could avoid hitting the posts directly with lasers. “Like oil and water, traditionally laser tweezers and gold don’t mix. By making very small islands of gold, we positioned individual molecules where we wanted them, and with a mechanical strength that enables more precise and additional types of studies,” Perkins says.

The research was supported by a W.M. Keck Grant in the RNA Sciences, the National Science Foundation, and NIST.

* D.H. Paik, Y. Seol, W. Halsey and T.T. Perkins. Integrating a high-force optical trap with gold nanoposts and a robust gold-DNA bond. Nano Letters. Articles ASAP (As Soon As Publishable) Publication Date (Web): June 3, 2009 DOI: 10.1021/nl901404s.

A new National Institute of Standards and Technology (NIST) assay using a “glow or no glow” technique may soon help the U.S. Department of Homeland Security (DHS) defend the nation against a spectrum of biological weapons that could be used in a terrorist attack. One very dangerous toxin on the list is ricin, a protein derived from castor beans that is lethal in doses as small as 500 micrograms—about the size of a grain of salt.

As part of its efforts to address the threat, DHS is working with NIST to create a standardized ricin sample with a known potency. Such a standard is needed both to check the accuracy of detection equipment, and, should an attack occur, to confirm the success of decontamination procedures. A major step toward this goal—the development of a rapid, reliable and precise assay of the potency of a ricin sample—has now been achieved by NIST scientists.

As detailed in an article posted online this week in Assay and Drug Development Technologies,* the new NIST assay uses a commercially available cell line genetically engineered to produce large amounts of green fluorescent protein (GFP). Ricin shuts down ribosomes—the protein manufacturing factories of a cell. Assay cells exposed to the toxin will quickly stop synthesizing GFP. This, in turn, will result in a measurable decrease in fluorescence—a drop that correlates directly to the strength of the ricin present.

The NIST assay yields many advantages over traditional cytotoxicity measuring systems, including: a highly sensitive response to ricin (as little as 1 nanogram per milliliter) within six rather than 24 hours; detection of the toxin long before significant cell death has occurred; results that are highly reproducible; no need for the addition of any reagents; and the flexibility to measure the potency of other ribosome inhibitors, even nanoparticles, with the same precision as ricin.

Partial support for this work was provided by the DHS Science and Technology Directorate.

* M. Halter, J.L. Almeida, A. Tona, K.D. Cole, A.L. Plant and J.T. Elliott. A mechanistically relevant cytotoxicity assay based on the detection of cellular green fluorescent protein. Assay and Drug Development Technologies, Vol. 7, No. 4 (August 2009; posted online the week of June 15, 2009).

A wildfire rages across southern California wildlands towards residential communities, endangering residents and firefighters and sending property up in smoke. This is an increasingly common story, occurring several times a summer. To better understand these Wildland-Urban Interface (WUI) fires and how best to prevent or fight them, researchers at the National Institute of Standards and Technology (NIST) have issued an in-depth study on fire behavior and defensive actions taken in a community during a such a fire.

WUI fires are becoming more prevalent as housing developments push into former wilderness areas. Drought is believed to also be a major contributor to larger wildfires. In addition to southern California, WUI fires also burn across the southern United States and in countries such as Australia, Greece, Italy and Spain. Little research has been conducted on understanding WUI fire behavior and on the effectiveness of current risk mitigation strategies.

The new NIST study examines in detail the events in one representative community during the Oct. 21-22, 2007 “Witch Fire” north of San Diego, Calif. The Witch Fire was the largest of the 2007 California fire storm. The fire burned 197,990 acres (80,124 hectares) and destroyed more than 1,100 homes. Fire damage was estimated at $1.8 billion and suppression costs were $18 million.

For their study, fire researchers Alex Maranghides and Ruddy Mell tracked down every fire captain who worked in the fire at The Trails housing development in Rancho Bernardo to follow the fire’s evolution. The NIST researchers, with the support of The Trails Homeowners Association, also collected event timeline information from homeowners. Of the 274 homes in The Trails neighborhood, 245 were within the fire’s perimeter. Of those, 74 homes were completely destroyed and 16 were partly damaged.

The data collection tracked the fire’s approach from the wildlands, the effects of the fire in the community and defensive actions taken by owners and first responders. Researchers documented the construction characteristics of the destroyed homes and the wildland and residential vegetation damage immediately after the fire.

The study revealed that two-thirds of all the homes destroyed were ignited either directly or indirectly by embers. “This is an important finding because current guidelines to make structures more fire resistant offer little guidance on how to make structures more resistant to an ember attack,” fire researcher Alex Maranghides explains. Researchers also learned that one-third of all structures within the fire perimeter were defended by first responders and/or homeowners.

The NIST report is the first in a series of three publications to understand WUI fire behavior. The second publication, in progress, will examine the role of construction and landscaping on the probability of a structure’s survival. A third report will describe a study that uses the data to build a computer-generated virtual community to test the fire behavior predicted by different fire models and compare the results to the observed fire behavior and structural response.

This study is part of NIST’s Reduced Risk of Fire Spread in Wildland-Urban Interface Communities research within its Building and Fire Research Laboratory, a program to develop first-generation tools by 2013 for improved risk assessment and mitigation in WUI communities at risk from wildfires.

“A Case Study of a Community Affected by the Witch and Guejito Fires,” report may be found at http://fire.nist.gov/wui.

Shape is turning out to be a particularly important feature of some commercially important nanoparticles—but in subtle ways. New studies* by scientists at the National Institute for Standards and Technology (NIST) show that changing the shape of cobalt nanoparticles from spherical to cubic can fundamentally change their behavior.

Building on a previous paper** that examined the properties of cobalt formed into spheres just a few nanometers in diameter, the new work explores what happens when the cobalt is synthesized instead as nanocubes. Nanoparticles of cobalt possess large magnetic moments—a measure of magnetic strength—and unique catalytic properties, and have potential applications in information storage, energy and medicine.

One striking difference is the behavior of the two different particle types when external magnetic fields are applied and then removed. In the absence of a magnetic field, both the spherical and cubic nanoparticles spontaneously form chains—lining up as a string of microscopic magnets. Then, when placed in an external magnetic field, the individual chains bundle together in parallel lines to form thick columns aligned with the field. These induced columns, says NIST physicist Angela Hight Walker, imply that the external magnetic fields have a strong impact on the magnetic behavior of both nanoparticle shapes.

But their group interactions are somewhat different. As the strength of the external field is gradually reduced to zero, the magnetization of the spherical nanoparticles in the columns also decreases gradually. On the other hand, the magnetization of the cubic particles in the columns decreases in a much slower fashion until the particles rearrange their magnetic moments from linear chains into small circular groups, resulting in a sudden drop in their magnetization.

The team also showed that the cubes can be altered merely by observing with one of nanotechnology’s microscopes of choice. After a few minutes’ exposure to the illuminating beam of a transmission electron microscope, the nanocubes melt together, forming “nanowires” that are no longer separable as individual nanoparticles. The effect, not observed with the spheres, is surprising because the cubes average 50 nm across, much larger than the spheres’ 10 nm diameters. “You might expect the smaller objects to have a lower melting point,” Hight Walker says. “However, the sharp edges and corners in the nanocubes could be the locations to initiate melting.”

While Walker says that the melting effect could be a potential method for fabricating nanostructures, it also demands further attention. “This newfound effect demonstrates the need to characterize the physico-chemical properties of nanoparticles extremely well in order to pursue their applications in biology and medicine,” she says.

* G. Cheng, R.D. Shull and A.R. Hight Walker. Dipolar chains formed by chemically synthesized cobalt nanocubes. Journal of Magnetism and Magnetic Materials, May 11, 2009, Vol. 321, issue 10, pp. 1351—1355.

** G. Cheng, D. Romero, G.T. Fraser and A.R. Hight Walker. Magnetic-field-induced assemblies of cobalt nanoparticles. Langmuir, December 2005. See Oct. 20, 2007, Tech Beat article, “Magnetic Nanoparticles Assembled into Long Chains”.

Better predictions of how many valuable materials behave under stress could be on the way from the National Institute of Standards and Technology (NIST), where scientists have recently found evidence* of an important similarity between the behavior of polycrystalline materials—such as metals and ceramics—and glasses.

Most metals and ceramics used in manufacturing are polycrystals. The steel in a bridge girder is formed from innumerable tiny metal crystals that grew together in a patchwork as the molten steel cooled and solidified. Each crystal, or “grain,” is highly ordered on the inside, but in the thin boundaries it shares with the grains around it, the molecules are quite disorderly. Because grain boundaries profoundly affect the mechanical and electrical properties of polycrystalline materials, engineers would like a better understanding of grain boundaries’ formation and behavior. Unfortunately, grain boundary formation in most technically useful alloys has eluded efforts to observe it for a century.

“You’d like to have simple engineering rules regarding how a material’s going to break,” says NIST materials scientist Jack Douglas. “For example, corrosion typically travels along grain boundaries, so polycrystals usually fracture along them. But metals melt and deform at very high temperatures, so observing them under those conditions is a challenge.”

While some scientists had speculated that the molecules in grain boundaries behave similarly to the way molecules do in glass-forming liquids, whose properties are well understood, none had found conclusive evidence to back up such a claim. That started to change when NIST theorist James Warren saw a conference presentation by the University of Alberta’s Hao Zhang concerning some odd “strings” of atoms in his simulation of grain boundary motion using a simulation technique called molecular dynamics. The collective atomic behavior observed in grain boundaries reminded the team of prior findings made at NIST about glass-forming liquids, whose atoms also form strings.

Subsequently, the team showed that the strings of atoms arising in grain boundaries are strikingly similar in form, distribution and temperature dependence to the string-like collective atomic motions generally found in glass-forming liquids—and that properties for both types of substances change with temperature in virtually the same way. “This work represents a paradigm shift in our understanding of grain boundaries,” Douglas says. “All the important qualities relating to atomic motion in both of these types of materials—the development of these string-like atomic motions, or the amplitude at which their atoms rattle—are strikingly similar. For all intents and purposes, grain boundaries are a type of glass.”

Douglas says the findings could permit substantial progress in predicting the failure of many materials important in construction and manufacturing and could improve our understanding of how crystals form boundaries with one another.

* H. Zhang, D.J. Srolovitz, J.F. Douglas and J.A. Warren. Grain boundaries exhibit the dynamics of glass-forming liquids. Proceedings of the National Academy of Sciences. Vol.106, No. 10 (2009).

The National Institute of Standards and Technology (NIST) will be serving up “soccer under glass”—the glass of a microscope lens—when nanosoccer makes its second appearance at the RoboCup games at the international competition in Graz, Austria, from June 29 to July 5, 2009.

Nanosoccer is a Lilliputian event where computer-driven “nanobots” the size of dust mites challenge one another on fields no bigger than a grain of rice. Viewed under a microscope, the nanobots are operated by remote control and move in response to changing magnetic fields or electrical signals transmitted across the microsized arena. “Nanoscale” refers to their mass. The bots are a few tens of micrometers to a few hundred micrometers long, but their masses can be just a few nanograms. They are manufactured from materials such as aluminum, nickel, gold, silicon and chromium.

The Nanogram 2009 demonstration will consist of two qualifier events and one competition event: the two-millimeter dash in which nanobots seek fast times for a goal-to-goal sprint across the playing field; a slalom course where the path between goals is blocked by “defenders” (polymer posts); and a ball handling “shootout” exercise that requires robots to move “nanoballs” (spheres about the diameter of a human hair) into the goal. Unlike the initial Nanogram demonstration at the 2007 RoboCup in Atlanta, performance in the qualifier events will determine which robots compete in the shootout.

The teams competing in Graz will include ETH Zurich (Zurich, Switzerland), Johns Hopkins University (Baltimore, Md.), the U.S. Naval Academy (Annapolis, Md.), the University of Waterloo (Waterloo, Ontario, Canada) and the Universite’ de Sherbrooke (Quebec, Canada).

Nanosoccer contests “road test” agility, maneuverability, response to computer control and the ability to move objects—all skills that future industrial nanobots will need for tasks such as microsurgery within the human body or the manufacture of tiny components for microscopic electronic devices.

NIST organizes the Nanogram 2009 events with the RoboCup Federation, an international organization dedicated to fostering innovations and advances in artificial intelligence and intelligent robotics by using the game of soccer as a testing ground. NIST’s goal in coordinating nanosoccer competitions between the world’s smallest robots is to show the feasibility and accessibility of technologies for fabricating MicroElectroMechanical Systems (MEMS), tiny mechanical devices built onto semiconductor chips and measured in micrometers (millionth of a meter). The contests also drive innovation in this new field of robotics by inspiring young scientists and engineers to become involved.

NIST Discovers How Strain at Grain Boundaries Suppresses High-Temperature Superconductivity

Researchers at the National Institute of Standards and Technology (NIST) have discovered that a reduction in mechanical strain at the boundaries of crystal grains can significantly improve the performance of high-temperature superconductors (HTS). Their results* could lead to lower cost and significantly improved performance of superconductors in a wide variety of applications, such as power transmission, power grid reliability and advanced physics research.

One of the main challenges in developing long-length, high-quality HTS wires is to mitigate the effect of granularity on wire performance because grain boundaries are prone to block current flow. Dislocations—defects in the crystalline structure—that grow in number with increasing grain-boundary angle strongly reduce the superconducting crosssection of the grain boundary.

Switching to thin-film designs has led to great improvements in grain alignment and significantly improved performance in, for instance, yttrium-barium-copper-oxide (YBCO) coated conductors. But even in these highly aligned superconductor films grain boundaries still limit their performance. The effect of dislocations can further be mitigated by chemical doping of the grain boundaries—for instance by replacing some of the yttrium atoms with calcium—but it has been difficult to apply this technique to long wire lengths.

Although it is well known that dislocations cause part of the grain boundary crosssection to become non-superconducting, the effect of strain—which extends from the dislocations into the remaining superconducting bridges over the grain boundary—was previously unknown. NIST’s Danko van der Laan and his collaborators have found that this strain plays a key role in reducing current flow over grain boundaries in YBCO. Furthermore, when the strain was removed by applying compression to the grain boundaries, the superconducting properties improved dramatically.

The new understanding of the effects of strain on current flow in thin-film superconductors could significantly advance the development of these materials for practical applications and could lower their cost. Some of the most promising uses are in more efficient electrical transmission lines, which already have been successfully demonstrated by U.S. power companies, and increased electric power grid reliability. NIST has research programs in both these areas. Improved HTS thin-film conductors could also enable more powerful high-field particle accelerators and advanced cancer treatment facilities.

* D.C. van der Laan, T.J. Haugen and P.N. Barnes. Effect of compressive uni-axial strain on grain boundary critical current density in YBa₂Cu₃O_7-δ superconducting films, Physical Review Letters Accepted papers, June 9, 2009.

NIST Seeks Proposals for $20 Million Program to Create Measurement Science and Engineering Fellowships

The National Institute of Standards and Technology (NIST) has announced that it is establishing a financial assistance program to help selected institutions develop and implement a NIST measurement science and engineering fellowship program. The new fellowship program is funded under the American Reinvestment and Recovery Act of 2009.

NIST expects to award up to $20 million to support up to five grants to U.S. higher education institutions, nonprofit and commercial organizations, or state, local or Indian tribal governments to partner with NIST in managing the fellowships. The awards will last for up to three years.

The program is designed to provide financial assistance to increase the number of research and collaboration opportunities at NIST in measurement science and engineering fields that contribute to the agency’s mission to advance innovation.

Fellows under this program will work on projects with NIST research scientists and engineers at the agency’s programs in Gaithersburg, Md., Boulder, Colo., and Charleston, S.C. NIST expects the program to support approximately 100 fellowship positions, with the exact number to depend upon the levels and durations of the awarded fellowships. The awards could range from part-time and summer fellowships for undergraduates to full-time positions for postdoctoral fellows or practicing scientists and engineers.

The deadline for applications is 3 p.m., Eastern time, July 27, 2009. Applications may be submitted on paper to the National Institute of Standards and Technology, 100 Bureau Drive, Stop 1060, Gaithersburg, MD 20899-1060.

Applications may also be submitted via the Internet at Grants.gov (www.grants.gov). Search for Funding Opportunity Number 2009-NIST-ARRA-MSE-FELLOWSHIP-01 or CFDA Number 11.609.

For more detailed information on the Measurement Science and Engineering Fellowship Program, see:

NIST, DOD, Intelligence Agencies Join Forces to Secure U.S. Cyber Infrastructure

The National Institute of Standards and Technology (NIST), in partnership with the Department of Defense (DOD), the Intelligence Community (IC), and the Committee on National Security Systems (CNSS), has released the first installment of a three-year effort to build a unified information security framework for the entire federal government. Historically, information systems at civilian agencies have operated under different security controls than military and intelligence information systems. This installment is titled NIST Special Publication 800-53, Revision 3, Recommended Security Controls for Federal Information Systems and Organizations.

“The common security control catalog is a critical step that effectively marshals our resources,” says Ron Ross, NIST project leader for the joint task force. “It also focuses our security initiatives to operate effectively in the face of changing threats and vulnerabilities. The unified framework standardizes the information security process that will also produce significant cost savings through standardized risk management policies, procedures, technologies, tools and techniques.”

This publication is a revised version of the security control catalog that was previously published in response to the Federal Information Security Management Act (FISMA) of 2002. This special publication contains the catalog of security controls and technical guidelines that federal agencies use to protect their information and technology infrastructure.

When complete, the unified framework will result in the defense, intelligence and civil communities using a common strategy to protect critical federal information systems and associated infrastructure. This ongoing effort is consistent with President Obama’s call for “integrating all cybersecurity policies for the government” in his May 29 speech on securing the U.S. cybersecurity infrastructure.

The revised security control catalog in SP 800-53 provides the most state-of-the-practice set of safeguards and countermeasures for information systems ever developed. The updated security controls—many addressing advanced cyber threats—were developed by a joint task force that included NIST, DOD, the IC and the CNSS with specific information from databases of known cyber attacks and threat information.

Additional updates to key NIST publications that will serve the entire federal government are under way. These will include the newly revised SP 800-37, which will transform the current certification and accreditation process into a near real-time risk management process that focuses on monitoring the security state of federal information systems, and SP 800-39, which is an enterprise-wide risk management guideline that will expand the risk management process.

The National Institute of Standards and Technology (NIST) has released the final version of an updated publication to help organizations and employees secure their computer systems for telecommuters.

Guide to Enterprise Telework and Remote Access Security (Special Publication 800-46 Revision 1) is intended to help organizations mitigate risks associated with the enterprise technologies they use for telework—working by computer from home or locations other than the office—including remote access solutions and client devices such as laptops and smart phones. A copy of the report can be downloaded at http://csrc.nist.gov/publications/nistpubs/800-46-rev1/sp800-46r1.pdf (http://csrc.nist.gov/publications/PubsSPs.html for the complete catalog of SP 800 series publications).

The Visiting Committee on Advanced Technology (VCAT) of the National Institute of Standards and Technology (NIST), the agency’s primary private-sector advisory group, has sent its 2008 annual report to Congress.

The VCAT was established by Congress in 1988 to review and make recommendations on NIST’s policies, organization, budget and programs. The 2008 report includes specific recommendations on NIST’s efforts to promote and support U.S. technological innovation and industrial competitiveness in areas such as partnerships, planning and research directions.

The report also emphasizes NIST’s important role in the economic well-being of the nation and expresses the Committee’s strong support for NIST’s investment priority areas in energy, information technology, health care, environment, manufacturing and physical infrastructure.

The next NIST VCAT meeting will be held on Oct. 14-15 in Boulder, Colo. VCAT meetings are open to the public. For more information, see www.nist.gov/director/vcat/.

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Editor: Michael Baum

Date created: June 16, 2009
Date updated: June 17, 2009
Contact: inquiries@nist.gov