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Our study illustrates the Cu2+-mediated unfolding of P-CK with disruption of the enzymatic function and the protective restoration role of osmolytes on P-CK inactivation. This study provides information of interest on P-CK as a metabolic enzyme of ectothermic animal in response to Cu2+ binding.

Microplastics are harmful to both marine life and humans. Herein, a pyrolysis–gas chromatography–mass spectrometry (Py-GC/MS) technique for the detection of microplastics in aquatic shellfish is demonstrated. The organic matter in aquatic shellfish was removed by alkali digestion. Subsequently, using hexafluoroisopropanol as the extraction solvent, the extraction method was optimized. The influence of the digestion process on the nature of microplastics was investigated by analyzing the samples before and after the alkali treatment via infrared spectrometry, laser particle sizing, and scanning electron microscopy. Spiked recovery experiments and an analysis of actual samples were performed using PA6 and PA66 as analytes. A quantitative analysis of the characteristic ion fragment produced by high-temperature cracking was performed after chromatographic separation and mass spectrometry identification. The linear range of this method for PA6 and PA66 was 2–64 μg. The limits of detection of PA6 and PA66 were 0.2 and 0.6 μg, while the limits of quantitation were 0.6 and 2.0 μg, respectively. Recovery ranged from 74.4 to 101.62%, with a precision of 4.53–7.56%. The results suggest that the Py-GC/MS technique is suitable for the analysis and detection of trace microplastics in aquatic shellfish.

The purpose of this study was to reveal the role of mitochondria in indicating a change in the freshness of the adductor muscle of Mizuhopecten yessoensis during cold storage and hardening. The adductor muscle hardens after 96 h of cold storage and reaches the maximum degree of hardening in 6 h. In this study, after hardening (102 h), the muscle fiber structure obviously broke and curled, and the sarcomere structure disappeared at 150 h. After hardening (102 h), the morphology of the mitochondria changed, including swelling, cristea breaking and membrane structure disappearance. The arginine phosphate content decreased gradually from the initial 4.618 to 1.306 µmol/g at 48 h, and there was no further obvious change. The ATP content decreased from 6.02 to 1.07 µmol/g in 120 h. The mitochondrial membrane potential (Δφ) was measured by a fluorescence method (JC-1). The changes in freshness could be divided into three classes according to the Δφ difference between the mitochondria in the adductor muscle after adding ADP and CCCP. Mitochondrial function was complete from 0 to 6 h; mitochondrial function began to decline at 6 to 48 h; and mitochondrial function completely disappeared after 48 h. The results showed that the mitochondrial membrane potential compared with other indicators could more sensitively reflect the changes in freshness during the cold storage hardening process of the adductor muscle.