Scientists have found proteins whose content in the bones of the deceased is gradually changing, if the corpse is kept in the water. Also with time comes the destruction of the amide groups of certain proteins. A study published in the journal Journal of Proteome Research, will help forensic experts to determine the time the corpse spent in the water.
One of the main issues of forensic medical thanatology — when the death occurred, or what is the postmortem interval. It is especially difficult to understand how long ago the person died, if the corpse was in the water. Protection in this case is affected by many factors: salinity, bacterial and chemical composition, the depth at which there was a corpse, and tides. Water scavengers and currents can separate and carry away a body part that may confuse forensic experts.
Standard methods for determining post-mortem interval based on subjective assessment and provide a high level of error. And objective parameters — education of corpse wax and colonization of a corpse by bacteria, algae and insects — independent from the salinity of the water, its temperature and the time of year.
Actively developing molecular approaches to the analysis of the decomposition of the bodies. Thanks to modern mass spectrometry it is possible to know the protein composition of tissues — knownthat in the dead body, he gradually changed. Less external factors affect the decomposition of protein of the bones, and hence their composition depends primarily from post-mortem interval. The changes that occur in the bones after death, was studied in several studies (1, 2, 3). The method proved to be effective — a degree of decomposition of proteins corresponds to the post — mortem interval but it is still not used for fabrics that are in the water.
British scientists from Northumbria University under the guidance of Procopio Noemi (Noemi Procopio) investigated changes in protein composition of mouse bone 22 corpses, which were stored for one or three weeks in different water (tap, salt, or chlorinated water from a pond). The tails of animals pasted to the bottom of the vessels to the body was located at the same depth. Proteins were extracted from the tibia and were analyzed using liquid chromatography combined with tandem mass spectrometry (a method which allows qualitatively and quantitatively determine substances in biological samples).
The contents 112 of proteins significantly differed between different periods of postmortem storage in water (p < 0.01), and only one protein differed from the corpses, which were stored in different types of water. Hence, the chemical composition of the environment does not affect the distribution of proteins.
Scientists selected 30 proteins, the content of which is most strongly differed between the groups. Of them chose specific for skeletal muscles and bones of the molecule, the number of which in bone tissue gradually decreased between the three time points: before exposure to water, a week and three weeks. In addition, estimated deamidation of proteins — removal of amide groups that occurs during degradation of proteins.
Best postmortem interval correlated to the protein content of glycolysis aldolase A, which is synthesized only in skeletal muscle. Deamidation of two peptides (they correspond to parts of proteins fetuin-A and insulin-like growth factor) and coagulation factor VIII gradually increased from the time the corpse was lying in water. The latter molecule was subjected to deamidation, if the body has been buried or lying on the ground, so it can be used to confirm that the body was in the water.
Forensic experts are studying and conducting research on “the farm of corpses”, where people can leave their bodies. At this range in Australia, scientists noticedthat one of the stages of decomposition of the corpse spread his arms out to the sides. This is probably due to degradation of the tendons.