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Medieval light catches the colours of disease

点击量:   时间:2017-10-26 01:01:01

By Charles Seife THE physics behind the glowing reds and vibrant blues of medieval stained-glass windows might soon provide a simple test for antibodies against HIV and other pathogens. When light hits metal, the photons send electrons in the metal rushing back and forth. If the piece of metal is tiny, a few wavelengths of light can set up a resonance in the particle, forming a large electron wave, or plasmon, which sloshes back and forth—much as singing in a small space causes some notes to set the chamber vibrating. When a particle resonates in this way, it absorbs those wavelengths that set off the resonance. This is how stained glass, which contains tiny metal particles, absorbs some colours but allows others to blaze through. Sheldon Schultz, a physicist at the University of California, San Diego, told the AAAS that similar “plasmon resonant particles” will give doctors a colourful way of detecting antibodies in a blood sample. The idea is to coat metal particles with the proteins or antigens that are recognised by the target antibodies. If antibodies are present in a sample of serum stuck to a slide, the particles will latch onto the antibodies. When exposed to light, they will absorb—and then re-emit—certain wavelengths. Seen from above, the particles will appear to glow with a colour that depends on the size of the particle. If there are no antibodies on the slide, the particles will be washed away and there will be no colour reaction. Schultz says his antigen-coated particles, which will be produced by Seashell Technology, a company in San Diego, should hit the market within a year. “You can label DNA and all biological objects,