ARLINGTON, Va. - Researchers have created the highest-resolution optical image ever, revealing structures as small as carbon nanotubes just a few billionths of an inch across.
The new method, developed by scientists at the University of Rochester, with colleagues from Portland State University and Harvard University, should literally shed light on previously inaccessible chemical and structural information in samples as small as the proteins in a cell's membrane.
"This is the highest-resolution optical spectroscopic measurement ever made," said Lukas Novotny, professor of optics at Rochester. "There are other methods that can see smaller structures, but none use light, which is rich in information." The research, which appeared in the March 7, 2003, issue of Physical Review Letters, was supported by the National Science Foundation.
The Rochester team's light-based technique, called near-field Raman microscopy, allows researchers to glean a great deal of visual information. Other ultra-high-resolution imaging techniques, such as atomic force microscopes, detect the presence of objects and image them but do not have the ability to directly view the light bouncing off an object.
With the new technique, Novotny and his colleague, Rochester visiting professor Achim Hartschuh, can determine a material's composition as well as its structure. Novotny and his team are also eager to learn characteristics of newly discovered structures, such as crossed or interconnected carbon nanotubes.
The ultimate vision for the project is to garner the information light provides from the proteins on a membrane, which would open the door to designer medicines that could kill harmful cells, repair damaged cells, or even identify never-before-seen strains of disease.
To light up the nanoscale, Novotny and Hartschuh sharpen a gold wire to a point just a few billionths of an inch across. A laser then shines against the side of the gold tip, creating a tiny bubble of electromagnetic energy that interacts with the vibrations of the atoms in the sample. This interaction, called Raman scattering, releases packets of light from the sample that can be used to identify the chemical composition of the material.
In about two years, Novotny and Hartschuh think they will be able to refine the system, already with a resolution of 20 nanometers (billionths of a meter), so that they can image proteins, which are only 5 to 20 nanometers wide, with eventual resolutions revealing much smaller molecules. [David Hart]
U Rochester Nano-Optics Group: http://www.optics.rochester.edu:8080/workgroups/novotny/
Undergraduate Creates Nanofilter for
ARLINGTON, Va. - In the miniaturized world of the "lab-on-a-chip," still a few years away, a pinprick will funnel a tiny droplet of blood into a microscopic maze of fluid circuits, sensors and filters-all housed on a device no bigger than a credit card. With these devices, doctors will get the results from many basic screenings immediately, instead of having to wait for blood samples to be shipped to a lab for analysis.
Nancy Guillen, an undergraduate at the University of Puerto Rico, Mayaguez, and a participant in the National Science Foundation's (NSF) Research Experience for Undergraduates program, spent last summer with a Cornell University research team manufacturing and testing a membrane that could one day be used in such a lab-on-a- chip.
Made from collagen, the main connective tissue protein in the human body, Guillen's membrane has nanometer-sized pores small enough to sift biomolecules by size alone. The membrane is able to block the blood protein hemoglobin while allowing smaller DNA molecules to pass through.
Guillen's project presentation won first place in the Chemical Sciences competition at the 2002 Annual Biomedical Research Conference for Minority Students, held last November in New Orleans. The Cornell team also presented the work in a paper at the Materials Research Society Fall Meeting in December, 2002.
Guillen conducted her research at Cornell's Nanobiotechnology Center, an NSF Science and Technology Center, and manufactured her filter on a chip at the Cornell Nanofabrication Facility, part of the NSF-supported National Nanofabrication Users Network.
In the near future, researchers plan to use the filter to prepare DNA chips for quick medical analyses or screening tests for newborns, and eventually the filters may have applications in implantable devices, such as artificial livers.
Under the guidance of Lori Lepak, a graduate student in the research group of electrical engineering professor Michael Spencer, Guillen's efforts broke new ground on several fronts. Collagen monomers, the raw material Guillen used, are up to 50 times thinner than the collagen fibrils in commercially produced collagen membranes. And, the "spin deposition" technique she used is one of the easiest and cheapest ways to make the 100 nanometer-thick membrane.
Another critical advantage of the collagen building blocks is their biocompatibility, meaning that the membrane would be safe from immune reactions if implanted in a body.
For example, a coating for transplanted pancreatic islet tissues would let glucose and insulin pass through freely, but block the larger immune system molecules that lead to rejection. Therefore, biomedical devices using collagen membranes may someday free organ-transplant recipients from lifetime regimens of powerful immunosuppressant drugs. [David Hart]
Winter residents of Madison, Wisconsin, expect their lakes to be rock-hard with thick ice for ice-fishing, ice-skating, and ice boating. However, this past winter the ice in some Madison-area lakes was not safe for winter sports.
According to Richard Lathrop, a scientist at the National Science Foundation (NSF)'s North Temperate Lakes Long-Term Ecological Research (LTER) site, researchers' routine sampling of lake ice showed that while the top ice layer was hard, the majority of the underlying ice was soft and variable in thickness. The unusual conditions are consistent with LTER research that suggests winter ice around the world is not lasting as long due to global climate changes, said Henry Gholz, LTER program director at NSF.
The unusual lake ice and water temperature conditions prompted LTER scientists to contact government officials, who in turn notified the public about unsafe ice conditions, especially as warmer weather arrived.
Surprisingly, water temperatures right under the ice have been relatively warm. The cause? The combined effects of a lack of snow cover and a proliferation of ice-free areas that opened up during an early winter warming period. Without snow cover to reflect sunlight off the lakes, the ice and underlying waters were heated by the sun's radiant energy.
Open holes on some of the shallower lakes that did not completely freeze over in early winter allowed winds to mix the water column, bringing warmer bottom water to the surface. Warm surface water temperatures caused premature melting of the ice from underneath, even though air temperatures this winter have been cold. [Cheryl Dybas]
Proteins are the "workhorse" molecules of the body - they carry messages, transport needed chemicals, act as antibodies, provide structure and carry out the multitude of other biological functions in our cells. Their central role makes them an object of intense interest for life scientists, but classifying the billions of different proteins on Earth is a daunting task.
A new 3-D map of the "protein universe," supported by NSF and created by Sung-Hou Kim and colleagues at the University of California at Berkeley and Lawrence Berkeley National Laboratory, simplifies matters by showing that the "universe" of proteins can be grouped into four basic classes, with implications for studies of evolution.
Previous maps have been two-dimensional, like roadmaps, but Kim and colleagues plotted similar proteins near each other in three- dimensional space. By representing the map in 3-D, Kim's team revealed 4 distinct groups of fold-types shown as red, yellow, green, and blue dots on the map.
The map, published in the March 4, 2002 Proceedings of the National Academies of Science, provides a global view for understanding both protein structure evolution of the past and a new tool for designing modern-day drugs.
Although the number of proteins in existence is huge, they are all made from roughly 10,000 common building blocks, called "folds." Kim's team constructed a map using 500 of the most common folds, which make up about 80 percent of known proteins. The new map should be a useful guide to both the past and the future. On one hand, different fold groups seem to have evolved at different times in evolutionary history. Because protein structures are better conserved through generations than DNA sequences, Kim said, the study of protein folds may offer new insight into the evolution of early organisms.
Looking forward, the protein fold map should also help researchers develop new drugs. Most drugs work by interfering with a particular protein's function, but a drug targeted toward one protein may also affect other proteins with similar structures. The map will help researchers avoid unintended adverse effects on "good" proteins by simplifying the search for protein similarities. In addition, gaps in the clusters within each class on the map will indicate protein structures, and potential drug strategies, yet to be discovered. [Roberta Hotinski]
Diamonds may be a scientist's best friend. Researchers have found that tiny inclusions encased in diamonds preserve information about the cycling of material between Earth's atmosphere, crust, and mantle some three billion years ago.
The researchers studied ratios of isotopes - atoms that are of the same type, but have a slightly different size - and tracked distinctive "isotopic signatures" that are unique to rocks that were created in the same place. By tagging a rock throughout its life cycle, researcher can use isotopic signatures to draw conclusions about previously unknown parts of Earth's early history, such as how the atmosphere evolved and the origin of early life forms.
Geologists James Farquhar and Boswell Wing of the University of Maryland at College Park, along with colleagues from other institutions, have shown that sulfide inclusions in diamonds from Botswana contain a characteristic ratio of the three isotopes of sulfur. The finding indicates that these sulfur atoms completed an entire geochemical cycle on Earth, from the air to the rocks to everywhere in between.
"This first documentation of the complete recycling of ancient sulfur adds to our knowledge of the dynamic processes that shaped our planet's evolution," said Sonia Esperanca, a program director in NSF's division of Earth Sciences, which funded the research.
Farquhar believes that the cycle began 3 billion years ago when an ancient volcano introduced sulfur dioxide and hydrogen sulfide gases into the atmosphere. The gases reacted with ultraviolet light in the early atmosphere and produced a unique sulfur "signature" in aerosols that fell to the planet's surface. These aerosols, in turn, became part of sulfide minerals in sedimentary rocks that were eventually cycled back into the Earth's mantle.
Farquhar's research proves that what goes around does indeed come around. The tectonic plate containing these sedimentary rocks eventually slid beneath another tectonic plate and into the interior of the Earth, in a process called subduction. When diamonds formed in Earth's hot interior mantle, the sulfides that had first come from eons-old volcanic gases became trapped in these gemstones. Billions of years later, the diamonds returned to the surface carrying the ancient mixture of sulfur atoms. Eventually, the diamonds were mined and researchers extracted the sulfide inclusions and analyzed them for their sulfur isotopic composition.
"This study demonstrates that distinctive isotopic signatures found in sulfide minerals from diamonds can be used to trace the movement of sulfur through its entire geochemical cycle, and that a mineral as precious as diamond can give us information about the Earth's surface and its early atmosphere," said Farquhar. [Cheryl Dybas]