The tips of our fingers aren’t the only places we carry a fingerprint. Chemical splodges on our skin create unique, but invisible, patterns. A new technique called molecular cartography maps these chemicals in 3D – it works on entire human bodies, but equally on plants, and on surfaces like this ATM keypad. Swabs from this man’s fingers and each of the keypad keys were analysed for traces of urocanate, a natural chemical which protects skin from UV damage. Chemicals are fleeting – they naturally decay, or rub away, but this chemical detective work paid off. There is a strong trace of urocanate on the fingertips (red), and a weaker trace on some of the keys (yellow and orange), allowing the man’s PIN to be worked out (8-0-1-7). Molecular cartography has a bright future in forensics, agriculture and medicine, where invisible bacterial traces could be followed to a source of infection.
BPoD stands for Biomedical Picture of the Day. Managed by the MRC Laboratory of Medical Sciences until Jul 2023, it is now run independently by a dedicated team of scientists and writers. The website aims to engage everyone, young and old, in the wonders of biology, and its influence on medicine. The ever-growing archive of more than 4000 research images documents over a decade of progress. Explore the collection and see what you discover. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.
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