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Effect of Microhydration on the Temporary Anion States of Pyrene.

ABSTRACT: The influence of incremental hydration (≤4) on the electronic resonances of the pyrene anion is studied using two-dimensional photoelectron spectroscopy. The photoexcitation energies of the resonances do not change; therefore, from the anion's perspective, the resonances remain the same, but from the neutral's perspective of the electron-molecule reaction, the resonances decrease in energy by the binding energy of the water molecules. The autodetachment of the resonances shows that hydration has very little effect, showing that even the dynamics of most of the resonances are not impacted by hydration. Two specific resonances do show changes that are explained by the closing of specific autodetachment channels. The lowest-energy resonance leads to efficient electron capture as observed through thermionic emission and evaporation of water molecules (dissociative electron attachment). The implications of low-energy electron capture in dense molecular interstellar clouds are discussed.

SUBMITTER: Lietard A

PROVIDER: S-EPMC9084602 | biostudies-literature | 2022 Apr

REPOSITORIES: biostudies-literature

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Effect of Microhydration on the Temporary Anion States of Pyrene.

Lietard Aude A Verlet Jan R R JRR

The journal of physical chemistry letters 20220414 16

The influence of incremental hydration (≤4) on the electronic resonances of the pyrene anion is studied using two-dimensional photoelectron spectroscopy. The photoexcitation energies of the resonances do not change; therefore, from the anion's perspective, the resonances remain the same, but from the neutral's perspective of the electron-molecule reaction, the resonances decrease in energy by the binding energy of the water molecules. The autodetachment of the resonances shows that hydration has ...[more]

PMID: 35420036

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Project description:BackgroundA precise determination of time since death plays a major role in forensic routine. Currently available techniques for estimating the postmortem interval (PMI) are restricted to specific time periods or cannot be applied for individual case-specific reasons. During recent years, it has been repeatedly demonstrated that Western blot analysis of postmortem muscle protein degradation can substantially contribute to overcome these limitations in cases with different background. Enabling to delimit time points at which certain marker proteins undergo distinct degradation events, the method has become a reasonable new tool for PMI delimitation under various forensic scenarios. However, additional research is yet required to improve our understanding of protein decomposition and how it is affected by intrinsic and extrinsic factors. Since there are temperature limits for proteolysis, and investigators are confronted with frozen corpses, investigation of the effects of freezing and thawing on postmortem protein decomposition in the muscle tissue is an important objective to firmly establish the new method. It is also important because freezing is often the only practical means to intermittently preserve tissue samples from both true cases and animal model research.MethodsSets of dismembered pig hind limbs, either freshly detached non-frozen, or thawed after 4 months of freeze-storage (n = 6 each), were left to decompose under controlled conditions at 30 °C for 7 days and 10 days, respectively. Samples of the M. biceps femoris were regularly collected at predefined time points. All samples were processed via SDS-PAGE and Western blotting to identify the degradation patterns of previously characterized muscle proteins.ResultsWestern blots show that the proteins degrade predictably over time in precise patterns that are largely unaffected by the freeze-and-thaw process. Investigated proteins showed complete degradation of the native protein band, partly giving rise to degradation products present in distinct time phases of the decomposition process.ConclusionThis study provides substantial new information from a porcine model to assess the degree of bias that freezing and thawing induces on postmortem degradation of skeletal muscle proteins. Results support that a freeze-thaw cycle with prolonged storage in frozen state has no significant impact on the decomposition behavior. This will help to equip the protein degradation-based method for PMI determination with a robust applicability in the normal forensic setting.

Dataset Information

Effect of Microhydration on the Temporary Anion States of Pyrene.

Publications

Effect of Microhydration on the Temporary Anion States of Pyrene.

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