Week of September 26, 2005

Protein logic digitizes cells

Brain researchers often use the analogy of brain as computer to frame their work. As it turns out, the analogy is also handy for examining the complex biochemical interactions inside individual cells.

Researchers from the University of Cambridge in England have developed a mathematical model of the biochemical interactions of protein molecules within cells that shows that proteins are capable of carrying out the basic binary logic functions of computing. They also showed that this type of binary logic appears to be at work in E. coli. bacteria.

The logic is carried out by the actions of small molecules that bind to the larger protein molecules and change the shapes of the proteins, which switches them between active and inactive states. The protein binding process can implement AND, OR and XOR logic gates.

The work isn't likely to lead to computers made from bacteria anytime soon, but it does present a new perspective for understanding the complex biochemical network of life, which in turn could lead to better understanding and treatment of diseases.

(The Logical Repertoire of Ligand-Binding Proteins, Physical Biology, September 2005)

Spray-on solar cell manufacturing

Researchers from Delft University of Technology in the Netherlands have developed a low-cost spray-on manufacturing technique for making solar cells.

The solar cells have an energy conversion efficiency of five percent. This is considerably lower than traditional silicon wafer solar cells, which have efficiencies of up to 30 percent, but the much simpler manufacturing process has the potential to lower the cost per kilowatt, according to the researchers.

The key component, which is applied by spraying, is a mix of copper indium sulfide and titanium dioxide nanoparticles sandwiched between a thin film of titanium dioxide and a layer of titanium dioxide nanocrystals. The copper indium sulfide nanoparticles absorb sunlight and the titanium dioxide nanoparticles convert photons to electrons.

Other researchers have combined organic dyes with titanium dioxide to make solar cells, but these organic materials degrade more readily when exposed to moisture and oxygen than copper indium sulfide.

The technique could make solar cells an economically competitive form of electricity generation, according to the researchers

(Nanocomposite Three-dimensional Solar Cells Obtained by Chemical Spray Deposition, Nano Letters, September 14, 2005)

Biochip spots cancer signs

The practice of chemically "functionalizing" carbon nanotubes and semiconductor nanowires by attaching DNA or other biomolecules to them has led to prototype biochips that can detect bacteria, viruses, specific types of DNA, or particular proteins molecules.

Researchers from Harvard University had advanced the field with a nanowire sensor array that can detect multiple biochemical signs of cancer. Cancer cells produce different types of proteins, and today's blood tests often look for only one, such as the prostate specific antigen (GSA).

The biochip works by measuring changes in electrical conductance of nanowires as specific protein molecules bind to and release from the chip's nanowires. The researchers tested the biochip using blood samples. The device could eventually be used for clinical diagnostics, including detecting and identifying cancers.

The researchers used a similar technique last year to make a biochip that can detect individual virus particles.

(Multiplexed Electrical Detection of Cancer Markers with Nanowire Sensor Arrays, Nature Biotechnology, published online September 18, 2005)

Plasma pen to fight plaque

In the not too distant future, your dental hygienist might stick what looks like a small blowtorch into your mouth. It shouldn't hurt, though, because the device will be emitting cold plasma rather than hot flame.

Plasmas are ionized gases, meaning the gas atoms carry an electric charge because they have lost or gained electrons. Plasmas typically exist in high-temperature environments like stars, and in low-pressure environments like the vacuum of outer space. Researchers have recently been able to reliably produce cold plasmas, which are room-temperature plasmas at atmospheric pressure.

Researchers from Old Dominion University have developed a low-power, hand-held cold plasma generator that produces a plasma plume several centimeters long.

Plasmas are useful for sterilization because they destroy bacteria by breaking down their cell membranes. The researchers' device could eventually be used for medical and dental care.

(Room-temperature Atmospheric Pressure Plasma Plume for Biomedical Applications, Applied Physics Letters, September 12, 2005)

Bits and pieces

A robust organic thin-film promises high-speed memory; an organic salt turns direct current into alternating current, a job ordinarily handled by electronic circuits in electric motors and refrigerators; an experiment measured how much an atom's wavelength shifts as it approaches a surface, providing a useful benchmark for researchers developing devices at the nanoscale.