Advertisement

If you have an ACS member number, please enter it here so we can link this account to your membership. (optional)

ACS values your privacy. By submitting your information, you are gaining access to C&EN and subscribing to our weekly newsletter. We use the information you provide to make your reading experience better, and we will never sell your data to third party members.

ENJOY UNLIMITED ACCES TO C&EN

Environment

Science Concentrates

July 18, 2005 | A version of this story appeared in Volume 83, Issue 29

Surface effects on NH3 adsorption

Bonding interactions between ammonia and carbon nanotubes depend strongly on the nature of the nanotubes' surfaces, according to a study that addresses fundamental issues in nanotube-based chemical sensing. Discrepancies between earlier theoretical studies, which indicate that ammonia bonds to nanotubes weakly, and experimental studies, which point to robust bonding, led Eric Borguet, associate professor of chemistry at Temple University, Philadelphia, and coworkers to probe the influence of sample preparation and other factors on ammonia adsorption by using experimental and theoretical methods. Working with scientists at Temple; the University of Pittsburgh; and Emory University, Atlanta, Borguet has found that pristine samples, such as those considered in the earlier theoretical work, bind ammonia weakly. In contrast, the presence of surface defect sites or oxygen-containing functional groups, such as that shown, leads to a several-fold increase in binding energy, the team reports (J. Am. Chem. Soc. 2005, 127, 10533).

Protein loss and early Alzheimer's

Depletion of the protein dynamin 1 in neurons may explain the early cognitive declines that show up in Alzheimer's patients before any visible damage to the structure of the brain, according to Adriana Ferreira, assistant professor in the department of cell and molecular biology at Northwestern University, and colleagues (J. Biol. Chem., published online July 8, dx.doi.org/10.1074/jbc.M503259200). Dynamin 1 is essential for proper functioning of the brain's synapses and for memory formation and information processing. In tests with neural cells and with a mouse model of Alzheimer's disease, the researchers have found that the amyloid-ß protein--which aggregates into plaques as the disease progresses--reduces dynamin 1 levels. Ferreira's team has shown that amyloid-ß may act through two possible routes: It abnormally activates calpain, a protein that cleaves dynamin 1, and it may also decrease production of dynamin 1. Drugs that inhibit calpain or increase production of dynamin 1 could be useful in treating Alzheimer's disease, the team suggests.

 

Birds drop pollution

Credit: IMAGE COURTESY OF MARK MALLORY

Exposure to pollutants like DDT is a well-publicized threat to birds' survival. But birds themselves may be spreading contaminants into the environment--through their poop. The northern fulmar (shown) is an Arctic seabird that lives on cliffs atop Canada's Devon Island. The birds eat a diet of plankton and fish from the surrounding ocean and deposit their droppings into freshwater ponds below. Jules M. Blais, associate professor in the biology department at the University of Ottawa, and colleagues have found that the pond sediments contain high levels of DDT, mercury, hexachlorobenzene, and other organochlorine compounds (Science 2005, 309, 445). The droppings may be a significant source of contamination in the Arctic ecosystem, the authors write. "The combined effects of biomagnification and biological transport dwarf the amount transported from atmospheric pathways alone," they point out.

Probing gene expression in single cells

Most gene expression methods report the average expression in a large cell population, losing information from individual cells. Weihong Tan and coworkers at the University of Florida now show that fluorescent nucleic acid probes known as molecular beacons can be used to monitor simultaneously the expression of multiple genes in single live cells. The probe fluoresces when it binds to its target, causing a conformational change that separates a quencher and fluorophore attached to either of its ends. As a demonstration, the researchers inject molecular beacons with different fluorophores directly into single cells to monitor expression of genes encoding ß-actin and manganese superoxide dismutase (Anal. Chem. 2005, 77, 4713). They measure the expression of the genes before and after exposing the cells to lipopolysaccharide, which stimulates expression of manganese superperoxide dismutase. By taking the ratio of the fluorescence to that of a reference probe, the researchers can compare gene expression from cell to cell. Tan plans to use the technique to study fundamental questions in neuroscience and cancer.

 

Cleaning up fullerenols

Advertisement
Credit: COURTESY OF ANDREW BARRON

One route suggested for attenuating the potential toxicity of fullerenes is to hydrolyze the molecules. Recent studies show that a fullerene's toxicity seems to decrease as the number of hydroxyl groups on its surface increases. Although fullerenols may be less toxic, they are far more mobile in the environment than their all-carbon counterparts. Fullerenols' potential accumulation in the environment prompted Andrew R. Barron and Robin Anderson of Rice University to develop a route to immobilize the molecules in aqueous solution. They have found that, within a wide pH range, fullerenols react rapidly and irreversibly with various metal salts to form insoluble metal-hydroxyfullerene aggregates (J. Am. Chem. Soc. 2005, 127, 10458). Barron and Anderson suspect that the fullerenols, despite their considerable size, are chelating the metal ions. Calculations on a simplified system show that as many as three fullerene diols can comfortably chelate a ferric ion (shown; C = gray, O = red, Fe = green). The team says their results could be a route to fullerenol remediation if the aggregates prove to be nontoxic. 

 

Article:

This article has been sent to the following recipient:

0 /1 FREE ARTICLES LEFT THIS MONTH Remaining
Chemistry matters. Join us to get the news you need.