Structures that put a spin on light reveal tiny amounts of DNA with 50 times better sensitivity than the best current methods, a collaboration between the University of Michigan and Jiangnan University in China has shown. Highly sensitive detection of DNA can help with diagnosing patients, solving crimes and identifying the origins of biological contaminants such as a pathogen in a water supply. “It really does not matter where the target DNA is from,” said Nicholas Kotov, the Joseph B. and Florence V. Cejka Professor of Chemical Engineering at U-M. “In order to detect a specific DNA, we just need to know a small portion of its sequence.” Current DNA analysis methods rely on copying segments of a strand of DNA. The process unzips the double helix and then short, lab-made ‘primer’ DNA strands attach to each half of the original DNA. These primers kick-start the copying process, using the unzipped DNA as a template. Targeted segments of DNA can be replicated in this way, doubling every cycle. If enough DNA is produced before copying errors become a major problem, then further analysis can show whether the sample matches a suspect, for example. But if the primers were very selective

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