Abstract
The present review provides an overview of the current research status on the effects of influencing factors on postmortem protein degradation used to estimate the PMI (postmortem interval). Focus was set on characteristics of internal and external influencing factors and the respective susceptibility and/or robustness of protein degradation. A systematic literature search up to December 2020 was conducted on the effect of influencing factors investigated in the context of postmortem protein degradation in the tissues of animals and humans using the scientific databases PubMed and Google Scholar, as well as the reference lists of eligible articles. We identified ten studies investigating a total of seven different influencing factors in degrading tissues/organs (n = 7) of humans and animals using six different methodological approaches. Although comparison of study outcomes was impeded by the high variety of investigated factors, and by high risk of bias appraisals, it was evident that the majority of the influencing factors concerned affected protein degradation, thus being able to modulate the precision of protein degradation-based PMI estimation. The results clearly highlight the need for a thorough screening for corresponding factors to enable the introduction of appropriate correction factors and exclusion criteria. This seems especially relevant for the protein degradation-based study of human PMI to increase the reliability and precision of the method and to facilitate a broader applicability in routine forensic casework.
Highlights
After death, a decomposing body undergoes complex unavoidable and irreversible biochemical, physical and physicochemical changes due to the lack of circulating oxygen, the cessation of anabolic production of metabolites, altered enzymatic reactions, and advancing cellular degradation [1]
We aim to reveal and to summarize the current research status regarding the types of influencing factors acting upon postmortem protein degradation, and the susceptibility and/or robustness of the degradation processes to each of these factors in human and animal tissue
The set of direct conclusions that can be drawn from the present literature analysis is that: (i) it confirms that a variety of factors are able to influence/modulate postmortem protein degradation; (ii) it highlights a largely unexplored complexity of the matter; and (iii) extensive further research and standardization is required to establish and finetune protein decomposition analysis as a most promising tool of forensic PMI determination
Summary
A decomposing body undergoes complex unavoidable and irreversible biochemical, physical and physicochemical changes due to the lack of circulating oxygen, the cessation of anabolic production of metabolites, altered enzymatic reactions, and advancing cellular degradation [1]. Intrinsic factors include body mass and surface area, and age, sex, antemortem medical conditions, the presence of injuries/trauma, level of bacterial activity, and cause of death, among others [3,4,5]. Extrinsic factors include the presence and type of clothing and other insulation of the body, and the environmental conditions at the death scene, in particular temperature, moisture, intensity of air flow, depth of burial, and activity of insects and microorganisms, etc. A thorough understanding of the susceptibility of postmortem changes to such factors is crucial, because these likely affect both the appearance of the changes as well as the rate of decay, either accelerating or decelerating the progression of postmortem events [7].
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