(Press-News.org) Good chemists are passive-aggressive — they manipulate molecules without actually touching them.
In a feat of manipulating substances at the nanoscale, UCLA researchers and colleagues demonstrated a method for isolating two molecules together on a substrate and controlling how those two molecules react when excited with ultraviolet light, making detailed observations both before and after the reaction.
Their research is published today in the journal Science.
"This is one step in measuring and understanding the interactions between light and molecules, which we hope will eventually lead to more efficient conversion of sunlight to electrical and other usable forms of energy," said lead study author Paul S. Weiss, a distinguished professor of chemistry and biochemistry who holds UCLA's Fred Kavli Chair in Nanosystems Sciences. "Here, we used the energy from the light to induce a chemical reaction in a way that would not happen for molecules free to move in solution; they were held in place by their attachment to a surface and by the unreactive matrix of molecules around them."
Weiss is also director of UCLA's California NanoSystems Institute (CNSI) and a professor of materials science and engineering at the UCLA Henry Samueli School of Engineering and Applied Science.
Controlling exactly how molecules combine in order to study the resulting reactions is called regioselectivity. It is important because there are a variety of ways that molecules can combine, with varying chemical products. One way to direct a reaction is to isolate molecules and to hold them together to get regioselective reactions; this is the strategy used by enzymes in many biochemical reactions.
"The specialized scanning tunneling microscope used for these studies can also measure the absorption of light and charge separation in molecules designed for solar cells," Weiss said. "This gives us a new way to optimize these molecules, in collaboration with synthetic chemists. This is what first brought us together with our collaborators at the University of Washington, led by Prof. Alex Jen."
Alex K-Y. Jen holds the Boeing-Johnson Chair at the University of Washington, where he is a professor of materials science and engineering and of chemistry. The theoretical aspects of the study were led by Kendall Houk, a UCLA professor of chemistry and biochemistry who holds the Saul Winstein Chair in Organic Chemistry. Houk is a CNSI researcher.
The study's first author, Moonhee Kim, a graduate student in Weiss' lab, managed to isolate and control the reactions of pairs of molecules by creating nanostructures tailored to allow only two molecules fit in place. The molecules used in the study are photosensitive and are used in organic solar cells; similar techniques could be used to study a wide variety of molecules. Manipulating the way molecules in organic solar cells come together may also ultimately lead to greater efficiency.
To isolate the two molecules and align them in the desired — but unnatural — way, Kim utilized a concept similar to that of toddler's toys that feature cutouts in which only certain shapes will fit.
She created a defect, or cutout, in a self-assembled monolayer, or SAM, a single layer of molecules on a flat surface — in this case, gold. The defect in the SAM was sized so that only two organic reactant molecules would fit and would only attach with the desired alignment. As a guide to attach the molecules to the SAM in the correct orientation, sulfur was attached to the bottoms of the molecules, as sulfur binds readily to gold.
"The standard procedure for this type of chemistry is to combine a bunch of molecules in solution and let them react together, but through random combinations, only 3 percent of molecules might react in this way," UCLA's Houk said. "Our method is much more targeted. Instead of doing one measurement on thousands of molecules, we are doing a range of measurements on just two molecules."
After the molecules were isolated and trapped on the substrate, they still needed to be excited with light to react. In this case, the energy was supplied by ultraviolet light, which triggered the reaction. The researchers were able to verify the proper alignment and the reaction of the molecules using the special microscope developed by Kim and Weiss.
The work was funded by the U.S. Department of Energy, the National Science Foundation, the Air Force Office of Scientific Research and the Kavli Foundation.
INFORMATION:The California NanoSystems Institute at UCLA is an integrated research facility located at UCLA and UC Santa Barbara. Its mission is to foster interdisciplinary collaborations in nanoscience and nanotechnology; to train a new generation of scientists, educators and technology leaders; to generate partnerships with industry; and to contribute to the economic development and the social well-being of California, the United States and the world. The CNSI was established in 2000 with $100 million from the state of California. An additional $850 million of support has come from federal research grants and industry funding. CNSI members are drawn from UCLA's College of Letters and Science, the David Geffen School of Medicine, the School of Dentistry, the School of Public Health and the Henry Samueli School of Engineering and Applied Science. They are engaged in measuring, modifying and manipulating atoms and molecules — the building blocks of our world. Their work is carried out in an integrated laboratory environment. This dynamic research setting has enhanced understanding of phenomena at the nanoscale and promises to produce important discoveries in health, energy, the environment and information technology.
END
EAST LANSING, Mich. — Man's best friend may provide more than just faithful companionship: A new study led by a Michigan State University researcher shows people who owned and walked their dogs were 34 percent more likely to meet federal benchmarks on physical activity.
The results, said epidemiologist Mathew Reeves, show that promoting dog ownership and dog walking could help many Americans – of which fewer than half meet recommended levels of leisure-time physical activity – become healthier.
"Walking is the most accessible form of physical activity available to people," ...
A new study says chimps, gorillas and other primates grow old gracefully much like humans. The findings come from the first-ever multi-species comparison of primate aging patterns reported in the March 11 issue of Science.
It was long thought that humans, who have relatively long life spans, age more slowly than other animals. But new research funded by the National Science Foundation's Division of Environmental Biology suggests the pace of human aging may not be so unique after all.
We had good reason to think human aging was unique, said co-author Anne Bronikowski ...
LA JOLLA, CA – March 10, 2011 – Scientists from The Scripps Research Institute have determined a new structure from a medically important superfamily of proteins. The structure should help instruct the design of a new kind of therapeutics for conditions ranging from Parkinson's disease to inflammation.
The study, published on March 10, 2011, in Science Express, an advance, online publication of selected research from the journal Science, provides important insights into how this large family of proteins, called G protein-coupled receptors (GPCRs), can recognize and respond ...
A University of Alberta researcher says grocery retailers need to take heed that a jump at the pumps will be a blow to their bottom line. Alberta School of Business professor Yu Ma notes that if stores want to survive, they'll have to change their tactics in the face of rising gas prices in order to attract shoppers "hungry" for better deals.
Ma and his colleagues say that when the price of gas rises, the monthly grocery bill is the prime target for cuts. The researchers noted that there are two sets of decisions made in the gas versus grub dilemma. The first choice deals ...
The basketball is in your hands. The score is tied and there are only a few seconds left on the clock. You have the ball about 10 feet away from the basket on the right side of the court, just outside the free-throw lane. It's decision time: Is it best to try a direct shot to win the game on a swish? Or do you use the backboard and bank home the winning basket?
Time's up; the buzzer sounds. Were you a hero or a goat?
New research by engineers at North Carolina State University show that you had a better chance of scoring that particular game-winning bucket ...
New Orleans, LA – LSU oncologist Vince D. Cataldo, MD, is the lead author of a review article reporting two chemotherapy drugs now indicated for second and third-line therapy in patients with advanced non-small-cell lung cancer are remarkably effective in treating a certain subset of these patients. Dr. Cataldo, a Clinical Assistant Professor of Medicine at LSU Health Sciences Center New Orleans School of Medicine, practicing at LSU's Earl K. Long Medical Center and Hematology-Oncology Clinic in Baton Rouge, and his colleagues say these drugs should be considered as a first-line ...
COPENHAGEN (11 March 2011) — Recent droughts and floods have contributed to increases in food prices. These are pushing millions more people into poverty and hunger, and are contributing to political instability and civil unrest. Climate change is predicted to increase these threats to food security and stability. Responding to this, the world's largest agriculture research consortium today announced the creation of a new Commission on Sustainable Agriculture and Climate Change.
Chaired by the United Kingdom's Chief Scientific Adviser, Professor Sir John Beddington, ...
Earth's biodiversity—the number of microorganisms, plants, and animals, their genes, and their ecosystems (such as rainforests and grasslands)—is declining at an alarming rate, even faster than the last mass extinction 65 million years ago. In fact, two thirds of the terrestrial species that exist today are estimated to be extinct by the end of this century. Humans are an integral part of this extensive network of life. We depend on biodiversity for goods and services; we impact biodiversity via rapidly expanding human population growth, consumption of resources, and ...
Postmenopausal women have a new health message to hear. Two annual dental checkups aren't enough. Older women need more, according to research findings from the Case Western Reserve University School of Dental Medicine and the Cleveland Clinic.
That message comes from a comparison study of women on and off bone-strengthening bisphosphonate therapies for osteoporosis.
Leena Palomo, assistant professor of periodontics from the dental school, and Maria Clarinda Beunocamino-Francisco from the Center for Specialized Women's Health at the clinic, set out to study the ...
HOUSTON – (March 10, 2011) – Stem cells derived from a patient's own bone marrow were safely used in pediatric patients with traumatic brain injury (TBI), according to results of a Phase I clinical trial at The University of Texas Health Science Center at Houston (UTHealth). The results were published in this month's issue of Neurosurgery, the journal of the Congress of Neurological Surgeons.
"Our data demonstrate that the acute harvest of bone marrow and infusion of bone marrow mononuclear cells to acutely treat severe TBI in children is safe," said Charles S. Cox, Jr., ...
