There is rarely time to write about every great science story that comes our way. So this year, we’re showing again a „Twelve Days of Christmas“ flyer series, highlighting one science story that fell through holes in 2020, every day from December 25 to January 5. Today: Identification of potential biomarkers (in mice) to correlate time of death in waterlogged corpses.
Correctly estimating the time of death seems very easy in fictional police procedures, but it is one of the more difficult aspects of a forensic professional’s job. This is especially true for corpses in water, where many additional variables make it difficult to determine how long the body has been submerged. A team of scientists at Northumbria University in Newcastle, UK, has come up with a new way to determine this, which includes measuring the levels of certain proteins in the bones. They described their findings in April paper In the journal Proteome Research.
Co-author Noemi Procopio was interested in forensic science since she was 14, but initially studied biotechnology because her native Italy did not have forensic science programs. When she moved to the University of Manchester in the United Kingdom to complete her PhD, she chose to specialize in the application of proteins (the study of proteins on a large scale) in the field, thanks to the influence of the former superintendent, an archaeologist of the application of proteins to the bones.
At the time of her PhD, there was very little research being done on Proteins Orthopedic forensic science and the subfield is still somewhat in its infancy. The results of this work studying bodies in terrestrial environments have been very promising, according to Procopio. But this is the first study to include submerged objects.
Forensic pathologists take samples of the level of decomposition in many areas of the body (face, neck, torso, and extremities), but when the body is in water, other factors can make it difficult to determine what is known as a post-mortem submerged interval (PMSI): salinity, temperature. The depth of the water, the tides, and whether bacteria or sweepers are present, for example.
Procopio’s previous work on using proteins to estimate the postmortem and age of death included pigs, which are closest to the composition of the human body. In this latest study, she chose to work with the bodies of mice, simply for practical reasons. „When you are doing an experimental exploratory study, it is better to use a smaller model,“ Lars said.
Using pigs also requires certain legal permissions to raise pigs, and it’s actually hard to get pigs that died of natural causes, rather than slaughtering them for research purposes – something Procopio was reluctant to do. „I think searching for animals is fundamental in some ways, such as medical research,“ she said. „But for forensic medicine, I think we can use all we have, animals that have already died, instead of killing something for the sake of forensic science.“
Instead, she and her team purchased 22 frozen mice from a reptile food supply center. Fortunately, freezing did not appear to have much effect on decomposition. „If you only freeze and defrost once, that’s not a huge deal in terms of decomposition and how it can be treated,“ Procopio said. They freeze one group of mice at room temperature, and another group at body temperature. Then they put the mouse carcasses in bottles of tap water, salt water, pool water, and chlorinated water. Vial tails were affixed to the bottom of the bottles to ensure that all mice remained at the same depth.
Every week and three weeks, Procopio Et al. Collecting lower leg (tibia) bones from mouse cadavers, extracting proteins and analyzing them using mass spectrometry. They found that the type of water had less effect on protein levels than when the bodies were submerged. For example, the longer the immersion was, the lower the levels of a protein called fructose-diphosphate aldolase. The type of water had an effect on one type of protein: Phytoin-A was likely to change chemically (Deception) In pond water compared to other types of water. This may be an indication that an object was initially submerged in the pool water and then moved to a different location.
Bottom line: These proteins can be excellent biomarkers to help determine the time of death in waterlogged corpses. For future studies, Procopio and her colleagues hope to examine the effects of different temperatures on the bone proteins of submerged cadavers, among other variables, and the ideal transition into ultimately human bodies, „because that’s what we ultimately need in order to apply the results of the work in the forensic case.“ „. It is already cooperating with so-called „corpse farms“ to this end, although the ongoing epidemic has stopped this work.
DOI: The Journal of Protein Research, 2020. 10.1021 / acs.jproteome.0c00060 (About DOIs).
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