Pathological proteins produce polymers

Deposits of distorted or otherwise errant proteins are key to understanding various brain diseases including Alzheimer’s, Parkinson’s, and the prion disease variant-CJD, they are also implicated in the pathology of type II diabetes. However, while such amyloids are a medical nightmare, researchers in Israel suggest that outside the body, synthetic versions of these substances could help us design a whole new range of nanomaterials and biomimetic plastics.

“The potential applications of these supramolecular assemblies exceed those of synthetic polymers,” explains Ehud Gazit of Tel Aviv University, writing in the current issue of Angewandte Chemie with co-author Izhack Cherny. “The building blocks may introduce biological function in addition to mechanical properties, he adds.

Prof. Ehud Gazit

Prof. Ehud Gazit

While the focus on amyloids is usually on their pathology, even in nature they are not always abnormal, misfolded proteins, they do have physiological roles in some organisms. For example, amyloids are an important protective material in the egg envelopes of insects and fish, they help form bacterial biofilms to protect a colony from natural antimicrobial substances that the bacteria may encounter, and they also allow such blooms to attach themselves to surfaces more effectively.

Technically speaking, amyloid fibrils are usually bundles of highly ordered protein filaments composed of ladder-like strands that can stretch to several micrometres in length. In cross-section, amyloids look like ribbons or like hollow cylinders. But, it is their resemblance to synthetic polymers (plastics) rather than their proteinaceous properties that drew the attention of the researchers in Israel.

Building amyloid polymers as templates for nanowires (Credit: Adapted from Angewandte)

Building amyloid polymers as templates for nanowires (Credit: Adapted from Angewandte)

Amyloids, for instance, are almost as strong mechanically as spider silk and by turn spider silk, weight for weight, is stronger than steel. They can also be stretched to many times their original length without splitting. Both properties are inaccessible to scientists working with synthetic polymers, but both properties are highly desirable for a wide range of engineering and technologies.

“The self-assembly properties of amyloids, together with their observed plasticity, makes them attractive natural building blocks for the design of new nanostructures and nanomaterials,” Gazit explains, “These building blocks can be broadly varied by means of simple molecular biological techniques.” The products might be used in novel sensors, tailored, biocompatible coatings, as enzyme mimics for speeding up chemical reactions, and for constructing nanoscale wires filled with silver and coated with gold for molecular electronics applications.

Further reading

Angew. Chem. Int. Edn, 2008, 47, 4062-4069
http://dx.doi.org/10.1002/anie.200703133

Prof. Ehud Gazit homepage
http://www.tau.ac.il/lifesci/departments/biotech/members/gazit/gazit.html

Ocean oxygen starvation

Oxygen-poor regions of tropical oceans are expanding as the oceans warm, limiting the areas in which predatory fishes and other marine organisms can live or enter in search of food, according to a major ongoing marine exploratory project. The phenomenon could cut overall marine biodiversity.

The Collaborative Research Centre programme – Climate: Biogeochemistry Interactions in the Tropical Ocean – funded by the German Research Foundation is working in close cooperation with the University of Kiel, and researchers at the Scripps Institution of Oceanography at the University of California San Diego.

Janet Sprintall (standing, fourth from left) on board CLIVAR cruise R/V Roger Revelle.

Janet Sprintall (standing, fourth from left) on board CLIVAR cruise R/V Roger Revelle.

The project aims to help scientists understand the interactions between climate and biogeochemistry on a quantitative basis as global warming progresses. Now, team member Lothar Stramma of the Leibniz Institute of Marine Sciences in Kiel and Scripps’ Janet Sprintall, and NOAA scientist Gregory Johnson and Volker Mohrholz from the Institute for Baltic Sea Research in Warnemünde, Germany, have analysed a database of ocean oxygen measurements in the tropics at a depth of 300 to 700 metres. They have found that oxygen levels have declined during the past fifty years. The ecological impacts of this increase could have substantial biological and economical consequences, the researchers suggest.

We found the largest decline in the tropical northeast Atlantic, explains Stramma, whereas the changes in the eastern Indian Ocean were much less pronounced. The researchers concede there is no way of knowing whether or not global warming alone is to blame. There are several natural processes that act on shorter timescales that might reduce oxygen levels, they point out. Sprintall adds that oxygen-poor areas could migrate into coastal areas via currents along the west coast of continents.

Mean dissolved oxygen concentrations in the world’s oceans at a depth of 400 metres (Image courtesy of AAAS/Science)

Mean dissolved oxygen concentrations in the world’s oceans at a depth of 400 metres (Image courtesy of AAAS/Science)

The width of the low-oxygen zone is expanding deeper but also shoaling toward the ocean surface,” said Sprintall, a specialist in observing changes of fluxes in ocean properties such as heat distribution. The team publishes details of their work in the 2nd May issue of Science.

Much of the recent data comes from oxygen sensors added to the 150 Argo floats – a worldwide network of 3000 temperature and salinity sensors. Sprintall says that the value of data from just 150 Argo floats suggests that even greater insights into shifting oxygen levels across the world’s oceans could be obtained if more floats were fitted with oxygen sensors.

Further reading

Science, 2008, 320, 655-658
http://dx.doi.org/10.1126/science.1153847

IFM-GEOMAR homepage
http://www.ifm-geomar.de/index.php?id=6&L=1

The ARGO project homepage
http://www.jimo.ucsd.edu/research/projects/current/A_theme/argo.htm

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Hubble Beater

Cambridge and Caltech astronomers have devised a new digital sensor for their telescopes that effectively cancels out the twinkling caused by the Earth’s atmosphere and allows them to obtain pictures of distant heavenly bodies that are clearer even than those obtained by space telescopes, such as Hubble.

Everyone knows the nursery rhyme, Twinkle, twinkle, little star, none are more frustrated by it than ground-based astronomers hoping to probe the depths of space. Even in the clearest air atop an Andean mountain, the stars still twinkle. Luckily there is now hope for the vertically challenged telescope user in the form of a new high-speed, almost noise-free digital camera developed by a team at the Institute of Astronomy in Cambridge led by Craig Mackay working with Caltech’s Nick Law and his group.

A Lucky break lights up new stars

A Lucky break lights up new stars

Previously, astronomers have tried to develop adaptive optics to correct the blurring caused by atmospheric distortion of the light from distant stars entering a telescope. Unfortunately, these devices have only proven themselves in the infrared region of the spectrum where twinkling can be cancelled out effectively. It is the visible region that has left ground-based astronomers envious of the images obtained by the Hubble Space Telescope. Until now.

The new camera works by recording a sequence of images at twenty frames per second or faster. The system software then checks each image, selects the sharpest and least smeared images and then the images are combined to cancel out the random fluctuations using a technique the team calls Lucky Imaging. The technique is similar to that used to cancel random noise in other areas of science such as spectroscopy, where a sequence of spectra for the same sample are recorded, added together and the peaks and troughs of noise cancel each other out.

Clearer view of the Cat’s Eye Nebula with Lucky Camera

Clearer view of the Cat’s Eye Nebula with Lucky Camera

The team has tested the method with the 5.1 m telescope at Mount Palomar. With its conventional imaging sensors, the telescope produces images an order of magnitude less detailed than those from Hubble. With the Lucky Camera in place, the team was able to obtain images that are actually twice as sharp as those produced by Hubble, all without leaving the comfort of planet Earth. These are the sharpest images ever taken either from the ground or from space, say the researchers, To get sharper pictures you have to use an even bigger telescope. Indeed, they are now investigating the possibility of getting Lucky with the 8.2 m Very Large Telescope of the European Southern Observatory in Chile and the 10 m Keck telescopes on the top of Mauna Kea in Hawaii.

So far, the team has already discovered many multiple star systems which are too close together and too faint to find with any standard telescope. Stars separated by as short a distance as one light-day have been resolved in images of the globular star cluster M13 which lies at a distance of some 25,000 light-years from earth

Further reading

Dr Craig Mackay homepage
http://www.ast.cam.ac.uk/~optics/people/cdm.htm

Lucky image homepage
http://www.ast.cam.ac.uk/~optics/Lucky_Web_Site/index.htm

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