Blog Archive

Monday, 21 April 2008

Weekly BioNews 14 - 21 Apr 2008

- Argonne scientists develop techniques for creating molecular movies

April 15, 2008 11:24 PM

They may never win an Oscar, but scientists at the U.S. Department of Energy’s (DOE) Argonne National Laboratory have developed techniques for creating accurate movies of biological and chemical molecules, a feat only theorized up until now.

Biological and organic molecules in solution are far more complex than the standard crystalline structures of salt or metals since they are constantly moving and changing over time. These motions have not yet been seen directly, but scientists using the high intensity x-rays at the Advanced Photon Source have measured images that are “blurred” by these motions and have used them to create more accurate movies of molecular motions.

Computer simulations are currently the only way to visualize molecular motions in solution, but researchers have not had a means to check the accuracy of these simulations for complex molecules. For the first time, scientists can see the movements first hand and compare them to their theoretical counterparts........

A new method that uses nanotechnology to rapidly measure minute amounts of insulin is a major step toward developing the ability to assess the health of the body’s insulin-producing cells in real time.

Among other potential applications, this method could be used to improve the efficacy of a new procedure for treating Type 1 (juvenile) diabetes that has demonstrated the ability to free diabetics from insulin injections for several years. It works by transplanting insulin-producing cells into the livers of diabetics to replace the cells that the disease has disabled or destroyed.The new insulin detection method was developed by a team of Vanderbilt researchers headed by Associate Professor of Chemistry David Cliffel and is reported in the February 18 issue of the journal Analytica Chimica Acta.

To gain this capability, the researchers developed a new electrode for a device called a microphysiometer. The microphysiometer assesses the condition of living cells by placing them in liquid nutrient, confining them in a very small chamber and then measuring variations in their metabolism. The volume of the chamber is only three microliters – about 1/20th the size of an ordinary raindrop – allowing the electrode to detect the minute amounts of insulin released by special pancreatic cells called Islets of Langerhans.....

Researchers at the National Institute of Standards and Technology (NIST) have demonstrated a new imaging system that detects naturally occurring terahertz radiation with unprecedented sensitivity and resolution. The technology may become a new tool chemical and biochemical analyses ranging from early tumor detection to rapid and precise identification of chemical hazards for homeland security instruments.

Terahertz radiation falls between microwaves and infrared radiation on the electromagnetic spectrum, with frequencies from about 300 million cycles per second to about 3 trillion cycles per second. Biological and chemical samples naturally emit characteristic signatures of terahertz radiation, but detecting and measuring them is a unique challenge because the signals are weak and absorbed rapidly by the atmosphere. The NIST prototype imager, described in detail for the first time in a new paper,* uses an exquisitely sensitive superconducting detector combined with microelectronics and optics technologies to operate in the terahertz range. The NIST system has its best resolution centered around a frequency of 850 gigahertz, a “transmission window” where terahertz signals can pass through the atmosphere. The system can detect temperature differences smaller than half a degree Celsius, which helps to differentiate between, for example, tumors and healthy tissue.....

New research demonstrates that novel probe technology based on flexible membranes can replace conventional atomic force microscopy (AFM) cantilevers for applications such as fast topographic imaging, quantitative material characterization and single molecule mechanics measurements.

“Our probes attach directly to AFM systems currently on the market and can collect topography measurements at least 50 times faster than traditional cantilevers because they use electrostatic forces between the membrane and an electrode to move the tip,” said Levent Degertekin, a professor in the George W. Woodruff School of Mechanical Engineering at Georgia Tech. The research team also includes Guclu Onaran and Hamdi Torun, graduate students in the Georgia Tech School of Electrical and Computer Engineering.

Details of the novel force sensing integrated readout and active tip (FIRAT) probe and its biological applications were presented at the American Physical Society meeting in March. This research was funded by the National Institutes of Health and the National Science Foundation.

University of Illinois researchers have developed a technique for imaging cells under an electron microscope that yields a sharper image of the structure of chromatin, the tightly wound bundle of genetic material and proteins that makes up the chromosomes.

Scientists have known for more than a century that proteins, such as histones, aid in packing DNA into the nucleus of a cell. Human cells contain 2 to 3 meters of DNA, which must be kinked and coiled enough to fit into a region 1/10 the width of a human hair.

Despite the use of powerful, high-resolution imaging techniques such as electron microscopy, the mechanism by which this chromatin packing occurs remains a mystery. The densely coiled chromatin fibers are very difficult to visualize, and little is known about how they condense during cell division, or unwind to allow gene expression.