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Objective: This study aimed to explore the feasibility of low-frequency electric field assisted controlled freezing-point storage (CFPS) technology improving the quality of shrimp. Methods: Low-frequency electric field was applied on the basis of controlled freezing-point storage (LFEF+CFPS) to preserve prawns, and the contents of malondialdehyde and salt soluble protein, as well as the changes of Ca2+-ATPase activity, pH value, shear force, color difference and protein molecular weight of prawns were monitored. Results: Compared with the conventional CFPS, the LFEF+CFPS had no significant effect on the content of malondialdehyde, salt-soluble protein, pH, shear force and color of prawn meat. However, after 3 days of storage, LFEF + CFPS treatment significantly inhibit the decrease of Ca2+-ATPase activity, and the Ca2+-ATPase activity of LFEF+CFPS treatment group stored for 15 days was 2.20 times that of the CFPS treatment group. In addition, LFEF + CFPS treatment significantly inhibited the decrease in the density of myosin heavy chain, actin and tropomyosin bands. Conclusion: Compared with conventional CFPS treatment, LFEF + CFPS treatment significantly inhibited the decrease of Ca2+-ATPase activity and protein degradation, maintained the stability of protein structure and properties, and slowed down the deterioration of prawn meat quality.

The stable chromium isotope system has been widely used as a redox proxy to reconstruct the oxygenation history of ocean atmosphere systems. However, the Cr isotope mass balance in modern oceans (i.e., inputs and outputs) remains poorly constrained. To investigate the influence of seawater‐peridotite reaction on the global marine Cr isotope mass balance, we report high‐precision Cr isotope data (δ53Cr) on a series of fresh and altered abyssal peridotites from the Gakkel Ridge and the Southwest Indian Ridge (SWIR). The least altered peridotites give a δ53Cr value of −0.08 ± 0.06‰ (2SD, n = 4) for the oceanic mantle which is consistent with the established δ53Cr of the Bulk Silicate Earth. Compared to fresh peridotites, a subset of altered peridotites exhibit a loss of isotopically light Cr with relatively positive δ53Cr values (up to 0.04‰). These altered peridotites are characterized by significant Cr loss and likely have been subject to serpentinization. By contrast, seafloor weathering has limited influence on the Cr concentrations and isotopic compositions of the altered peridotites. Monte Carlo (MC) simulations of marine alteration suggest a net Cr flux into seawater from altered abyssal peridotites of ∼3.5 × 108 mol/yr, which is on the same order of magnitude as the riverine input flux of 108–109 mol/yr. Furthermore, the MC results suggest that the peridotite‐sourced net Cr flux has a negative δ53Cr signature (−0.33 ± 0.21‰, 2SD). Thus, seawater‐peridotite interactions must be considered when evaluating the modern oceanic Cr isotope mass balance. Plain Language Summary: The stable chromium isotope system is an emerging paleoredox proxy for tracing Earth's atmospheric oxygenation over geological timescales. However, accurately inferring past Earth's atmospheric oxygenation levels using chromium isotopes requires a more precise understanding of the elemental and isotopic cycling of chromium, particularly within the oceans. By studying abyssal peridotites which are rocks found beneath the oceanic crust, we find that specific types of alterations in these rocks, particularly the process of serpentinization, have an impact on the chromium isotopes. These findings provide insights into the mechanisms involved in transporting chromium from the deep Earth mantle to the oceans. We discover that these altered rocks release a flux of isotopically light chromium into the ocean, which is comparable to the amount coming from rivers. Our study sheds new light on the complex interactions between seawater and abyssal peridotites, which potentially exert a profound impact on the global marine Cr isotope mass balance. Key Points: The first data set of stable Cr isotopic compositions for abyssal peridotitesSeafloor weathering has insignificant impact on the Cr isotopic compositions of abyssal peridotitesSeafloor alteration exerts a key control on the Cr isotopic composition of seawater [ABSTRACT FROM AUTHOR]

A new SEK15-derived polyketide compound, strepolyketide D (1), was isolated from salt-lake-derived Streptomyces sp. DBC5, together with two known analogues (2-3). Their structures were elucidated based on spectroscopic analysis of IR, MS, 1 D and 2 D NMR. Compound 2 elicited moderate antioxidation with IC50 value of 39.26 μg/ml. The results of the study revealed that salt-lake actinomycetes of Lake Dabancheng appear to have immense potential as a source of polyketide compounds. [ABSTRACT FROM AUTHOR]