ac detective
CS-Eye: Copenhagen Accelerator MS meets forensic pathology.
he poets will tell you that the eyes are the windows to the soul, but according to recent work by forensic pathologist Niels Lynnerup and colleagues at the University of Copenhagen and the University of Aarhus (Denmark), your eyes may also provide scientists with a glimpse of your birth—or more specifically, your birth year. In a situation like the devastating tsunami that struck the coast of Thailand in 2004, says Lynnerup, such a simple piece of information can be critical to identifying the thousands of Your eyes can now give away your age. people who perished. “We’re always looking at environment and food chain. For Lynnew methods to identify people,” he explains. “You might say we’re trying to nerup and colleagues, this spike provided a chronological reference point. develop a forensic toolbox, so that we’ll Using AMS, the researchers examalways have something that’s appropriined eye lenses from 13 deceased people ate for the specific problem.” of varying ages and compared the 14C Recently, Lynnerup was reading levels in the sample proteins with a caliabout eye formation and learned that bration curve of published atmospheric crystallines, proteins found in the eye 14C levels from the past 90 years (PLoS lens, form almost entirely by the end of ONE 2008, 3, e1529). With the exthe first postnatal year. Furthermore, the structure of the lens is such that the ception of the oldest case studied—an 80-year-old person—the researchers proteins are cut off from the rest of the were able to identify the age of the test body and therefore do not exchange subjects to within 1.5 years with 95% over time. confidence. The revelation led him to conclude Lynnerup is quick to point out that that if he could correlate some type of the idea of dating unchanging human molecular signature with an environtissues is not unique to his group. Other mental timeline, he could determine researchers had performed similar exthe ages of people from the proteins in periments using 14C signatures of dental their eye lenses. Lynnerup and his team enamel (Nature 2005, 437, 333–334). eventually realized that high-precision “One can immediately understand accelerator MS (AMS) and the isotopic that dental enamel has an immutable echo left behind by the nuclear bomb tests of the 1950s and 1960s might pro- nature,” he says. “I mean, it is a hard ceramic-like tissue. That the lens convide the solution. Before the 1963 Test Ban Treaty, nu- tains molecules just as immutable—even though it changes form whenever [the clear testing programs produced a draeye focuses] on something—was for me matic spike in atmospheric 14C levels. Since then, these levels have declined as somewhat surprising.” the isotope has been absorbed into the Because the technique uses only a
© 2008 American Chemical Societ y
single radiocarbon reference point, Lynnerup acknowledges that its utility is not unlimited. “The method will still be useful for 100 years or more, but it will become less precise,” he says. “Now, we can utilize the very steep [isotopic] increase, so there is a very marked change from year to year. But as atmospheric 14C levels go back to normal, the differences become less and less.” The researchers also note that sample integrity will be an issue. For these experiments, they extracted lenses up to 3 days postmortem. Beyond this point, they found that lens degradation and putrefaction made it impossible to extract the lens intact. Although his primary interest is forensics and identifying the dead, Lynnerup also sees a place for his method to help the living by improving our understanding of human disease. “This might be a method to date single tissues,” he says—an idea first suggested by the group working on dental enamel (Cell 2005, 122, 133–143). “For instance, if you had a tumor where some of the central bits necrotize and don’t change, it might be possible to radiocarbon date some of the earliest parts of the tissue so that you can say more precisely when a given tumor started,” he adds. Perhaps most exciting to Lynnerup, however, is how the research shows the power of an interdisciplinary approach to science. In this case, forensic pathologists, nuclear physicists, and eye pathologists met to share thoughts and goals. “I think the approach is very stimulating and leads to other ideas,” he says. “You talk to other people with a completely different mindset.” That’s the benefit of adding new eyes to an old challenge, one might say. a —Randall C Willis shutterstock/ losevsky pavel
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