Friday, November 11, 2011

Controversy over reopening the 'Sistine Chapel' of Stone Age art

Carmen Drahl, C&EN associate editor, points out in the article that Spanish officials closed the tourist mecca to the public in 2002 after scientists realized that visitors were fostering growth of bacteria that damage the paintings. Now, however, they plan to reopen the caves. Declared a World Heritage Site by the United Nations' Educational, Scientific and Cultural Organization (UNESCO), Altamira's rock paintings of animals and human hands made scientists realize that Stone Age people had intellectual capabilities far greater than previously believed.

The article explains how moisture and carbon dioxide from tourists' breath, body heat and footsteps (which kick up bacterial spores) foster growth of bacteria on the cave walls. Those bacteria damage the precious , which supposedly influenced great modern artists like Picasso. Drahl discusses the scientific controversy over limited reopening of the caves to tourism and measures that could minimize further damage to the paintings.

More information: For Cave's Art, An Uncertain Future -

Provided by American Chemical Society (news : web)

Fluoride shuttle increases storage capacity: Researchers develop new concept for rechargeable batteries

 Karlsruhe Institute of Technology (KIT) researchers have developed a new concept for rechargeable batteries. Based on a fluoride shuttle -- the transfer of fluoride anions between the electrodes -- it promises to enhance the storage capacity reached by lithium-ion batteries by several factors. Operational safety is also increased, as it can be done without lithium.

The fluoride-ion battery is presented for the first time in the Journal of Materials Chemistry by Dr. Maximilian Fichtner and Dr. Munnangi Anji Reddy.

Lithium-ion batteries are applied widely, but their storage capacity is limited. In the future, battery systems of enhanced energy density will be needed for mobile applications in particular. Such batteries can store more energy at reduced weight. For this reason, KIT researchers are also conducting research into alternative systems. A completely new concept for secondary batteries based on metal fluorides was developed by Dr. Maximilian Fichtner, Head of the Energy Storage Systems Group, and Dr. Munnangi Anji Reddy at the KIT Institute of Nanotechnology (INT).

Metal fluorides may be applied as conversion materials in lithium-ion batteries. They also allow for lithium-free batteries with a fluoride-containing electrolyte, a metal anode, and metal fluoride cathode, which reach a much better storage capacity and possess improved safety properties. Instead of the lithium cation, the fluoride anion takes over charge transfer. At the cathode and anode, a metal fluoride is formed or reduced. "As several electrons per metal atom can be transferred, this concept allows to reach extraordinarily high energy densities -- up to ten times as high as those of conventional lithium-ion batteries," explains Dr. Maximilian Fichtner.

The KIT researchers are now working on the further development of material design and battery architecture in order to improve the initial capacity and cyclic stability of the fluoride-ion battery. Another challenge lies in the further development of the electrolyte: The solid electrolyte applied so far is suited for applications at elevated temperatures only. It is therefore aimed at finding a liquid electrolyte that is suited for use at room temperature.

Story Source:

The above story is reprinted from materials provided by Karlsruhe Institute of Technology.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

M. Anji Reddy, M. Fichtner. Batteries based on fluoride shuttle. Journal of Materials Chemistry, 2011; DOI: 10.1039/C1JM13535J

Going to extremes to find greener chemicals

That molecular sleuthing using owes its success to an enzyme from a heat-loving bug that hangs out in and thermal vents. Because the enzyme can withstand , we can use it in cycles of that multiply tiny amounts of DNA up into useful quantities, much like a molecular photocopier. Then the  DNA can be sequenced and, hopefully, the crime can be solved.

It’s an example of how the adaptations of ‘extremophiles’ that happily live in seemingly harsh environments can inspire useful , and UCD researcher and Conway Fellow, Dr. Francesca Paradisi is on the case.

Her approach looks at ‘halophile’ organisms that can live in high salt concentrations such as the Dead Sea, and she’s working out whether some of their enzymes could help make chemical processes in industry greener.

Paradisi, who studied chemistry at Bologna in Italy, wasn’t familiar with extremophiles before she came to UCD to work with Professor Paul Engel just after she finished her PhD. But when she saw what his group was doing, she was intrigued by the possibilities.

Now a college lecturer at UCD School of Chemistry and Chemical Biology, she has built up her own team and they have been meticulously screening various halophiles for a type of enzyme called alcohol dehydrogenase (ADH).

It’s an enzyme that many organisms - including ourselves - produce naturally, and it is used in chemical processes in the food and pharmaceutical industries. So why might an ADH from a salt-loving organism be particularly useful? 

“The idea is that enzymes that are produced by these halophiles, due to their particular high-salt environment, will be more likely to adjust to a solvent situation - when you have high salt you have less water around the ,” explains Dr. Paradisi.

The trick is to find enzymes that tick several boxes: they are easy to purify from the organism, they are stable so they don’t need too much cosseting and their special properties can make a range of chemical processes greener.

So Paradisi’s team has been cloning, isolating and analyzing various ADH enzymes from three types of halophile to see what kinds of talented enzymes they produce naturally.

The lab has been focusing on three main organisms: Halobacterium salinarium, Haloarcula marismortui and Haloferax volcanii, explains Dr. Paradisi, but the initial work has been difficult because so little is known about how to purify the proteins.

However, despite the newness of the area, already they are turning up promising candidate enzymes, and soon the group will publish the first of the findings in the journal Extremophiles.

Their approach is also attracting the interest of industry: Dr. Paradisi’s group has an ongoing collaboration with Spanish biotech company Arquebios, and she is in talks with other potential partners.

She stresses that the organisms used in this process are safe. “These organisms are completely harmless, and they are generally growing in a highly-salted environment so as soon as you put them in water in the sink they burst.”

So what is the ultimate goal? To develop a system where a specially engineered bug can produce useful amounts of one or more useful enzymes like a biological printing press, explains Dr. Paradisi, whose work has received funding from the Environmental Protection Agency, Science Foundation Ireland, IRCSET and Merck.

“Enzymes are a little different from small chemicals that you would find in nature - they are quickly reproduced and we can clone them,” she says. “So we are looking to use a host cell that can be engineered in such a way that it produces a higher amount of the extremophile enzymes.”

More information: 'Characterization of alcohol dehydrogenase (ADH12) from Haloarcula marismortui, an extreme halophile from the Dead Sea'

Provided by University College Dublin

Researchers suspend, image single DNA molecules

Researchers in the lab of Harold Craighead, the Charles W. Lake Professor of Engineering, used advanced nanofabrication techniques to make it easier to see how single molecules of DNA subtly change during a chemical process called methylation. A better understanding of this process could lead to further study into of numerous diseases, including Alzheimer's, Parkinson's, diabetes and cancer.

This work was published online Oct. 7 in the journal Analytical Chemistry.

DNA is normally packed tightly into the nucleus of a cell and housed into chromosomes. Within chromosomes lie many chemical perturbations that modify how genes are expressed, without anything to do with the underlying DNA sequence, explained Aline Cerf, a postdoctoral associate who led the study.

Studying these chemical modifications is a relatively new field called epigenetics. The researchers focused on a particular process in which a section of the DNA, called 5-cytosine, becomes methylated -- its chemical structure changes by the addition of a (CH3).

Cerf and colleagues first took genetic material extracted from cells and suspended it in solution. Using a technique called , they made a stamp, consisting of micrometer-sized wells, out of (PDMS). The solution of coiled was deposited onto the PDMS stamp, which was then moved at a controlled speed across a . The molecules became trapped by capillary forces in the wells, and stretched.

The result was an ordered array of elongated molecules that were transferred by contact onto a support to be imaged and studied.

In related work, the researchers also published a paper in the journal Nano Letters, Sept. 16, which details how their molecular arrays could be transferred to and imaged on substrates of graphene -- single-layer sheets of carbon atoms. This let them get even better pictures of the molecules by allowing the use of transmission electron microscopy for imaging of the added tags and the underlying base sequence in the DNA.

"The DNA molecule arrays can be tagged, separated and lined up to quickly read off the genetic and epigenetic information," Craighead said.

Researchers have in the past studied these same molecules while still contained in their nuclei, he said, but this new technique simplifies that process.

"We're no longer dealing with bundles of molecules that are hindering the information of another one," Craighead said. "We are taking the equivalent of the DNA contained in one cell and spreading it out on a surface, so you can look at all of these things and search for and study things of interest that will no longer be lost in this disordered world we were in before. Aline's results have brought us out of that world."

Provided by Cornell University (news : web)