This work studied the effects of electromagnetic fields (EMF) with frequencies between 100 and 400 Hz and a fixed strength of 12 mT on cold storage of grass carp at 4 °C for 30 min, and Ca 2+ ATPase enzyme activities, and lipid and protein oxidations in samples were measured to assess changes in intracellular Ca 2+ concentration and oxidative stability. Results showed higher Ca 2+ ATPase activities in samples treated with EMF frequencies. Significant ( p < 0.05) decreases occurred in protein oxidation for samples treated between 100 and 300 Hz, but an increase was observed for treatment with 400 Hz. However, the lipid oxidation increased for samples treated up to 200 Hz and decreased with further increase in frequency to 300 and 400 Hz. Nuclear magnetic resonance analysis showed that exposure to different frequencies of EMF could reduce the association of water molecules with protein for both bound and immobilized water. Overall, treatments of EMF between 100 and 400 Hz could improve grass carp quality during cold storage.
To determine furaltadone metabolites 5-methylmorpholino-3-amino-2-oxazolidinone (AMOZ) residual levels in ctenopharyngodon idellus, direct competitive enzyme-linked immunosorbent assay (dcELISA) was developed based on a single-chain variable fragment (scFv)-alkaline phosphatase (AP) fusion protein. Firstly, VH and VL gene sequences were cloned from hybridoma cell lines secreting monoclonal antibody against AMOZ derivative, and then the productive VH and VL genes were assembled to a scFv gene and engineered to produce scFv-AP fusion protein. The fusion protein was further identified as a bifunctional reagent for immunoassay, then a sensitive one-step dcELISA against AMOZ derivative was developed with a half-maximal inhibitory concentration (IC50) and limit of detection (LOD) of 10.62 and 4.83 ng/mL, respectively. The recovery values of AMOZ from spiked fish samples determined by dcELISA were in 71.31%∼82.88%. The results suggested that the prepared scFv-AP fusion protein in this work can be used for rapid and convenient immunoassays to detect AMOZ residues in fish samples.
Biological interaction with extremely low-frequency electromagnetic fields (ELF-EMF) is complex and the 50 and 60 Hz frequencies are among a few ‘window’ frequency ranges reported with a stimulating effect. In the current study, ELF-EMF at frequencies from 40 to 70 Hz were examined for their possible significance in inducing biological effects during chilled storage of grass carp ( Ctenopharyngodon idellus ) at 4 °C for 4 and 6 h. The myofibrillar protein extracted from the grass carp was analyzed and the results indicate significant (p < 0.05) increases in Ca 2+ ATPase activity and pH, and a reduction in the total sulfhydryl content during the treatment of 50 and 60 Hz frequencies for both storage durations, in particular, the treatment of 50 Hz had pronounced effects with higher correlations. Therefore, the 50 Hz might be associated with the ‘window’ effect, enhancing myofibrillar protein quality during chilled storage.
危险品化学品经营许可证（带存储）