Search

Glutathione peroxidase is an important enzyme in the endogenous antioxidant defense system. In the current study, we cloned the full-length cDNA sequence that encodes a glutathione peroxidase from Magallana hongkongensis (designated as MhGPx), investigated the tissue expression profile of MhGPx mRNA, and studied the time-dependent effects of cadmium exposure and air exposure at two temperatures (4 °C and 15 °C) on the mRNA level of MhGPx in different tissues (including gill, adductor, mantle, and digestive gland). The full length of MhGPx was 1306 bp. This gene was found to contain a selenocysteine insertion sequence within the 3′ untranslated region, which indicates that the protein it encodes was a selenoprotein. In addition, MhGPx was constitutively expressed in all four selected tissues, and the level of expression in the digestive gland was highest, indicating that MhGPx mRNA expression has tissue-specificity. Under cadmium exposure, mRNA expression was significantly increased on day 1. When exposed to air, the highest MhGPx mRNA expression in the 4 °C group was lower and appeared later than that of the 15 °C group. The results of this study contribute to a better understanding of oyster GPx in response to oxidative stress. [ABSTRACT FROM AUTHOR]

Highlights: A hybrid electrocatalyst consisting of PtNi-W alloy nanocrystals loaded on carbon surface with atomically dispersed W sites was realized. Single-atomic W formed protonic acid sites and established an extended proton transport network at the catalyst surface. Peak power density is enhanced by 64.4% compared to that with the commercial Pt/C catalyst in fuel cell as cathode at ultra-low loading of 0.05 mgPt cm−2. The performance of proton exchange membrane fuel cells is heavily dependent on the microstructure of electrode catalyst especially at low catalyst loadings. This work shows a hybrid electrocatalyst consisting of PtNi-W alloy nanocrystals loaded on carbon surface with atomically dispersed W sites by a two-step straightforward method. Single-atomic W can be found on the carbon surface, which can form protonic acid sites and establish an extended proton transport network at the catalyst surface. When implemented in membrane electrode assembly as cathode at ultra-low loading of 0.05 mgPt cm−2, the peak power density of the cell is enhanced by 64.4% compared to that with the commercial Pt/C catalyst. The theoretical calculation suggests that the single-atomic W possesses a favorable energetics toward the formation of *OOH whereby the intermediates can be efficiently converted and further reduced to water, revealing a interfacial cascade catalysis facilitated by the single-atomic W. This work highlights a novel functional hybrid electrocatalyst design from the atomic level that enables to solve the bottle-neck issues at device level. [ABSTRACT FROM AUTHOR]

This study aimed to explore the effect of κ-carrageenan on the stability of WSP from the muscle of Pinctada martensii and provide data reference for the use of P. martensii meat and improvement of the functional properties and application expansion of different types of aquatic proteins. The effect of κ-carrageenan (2 mg/mL) on WSP (1 mg/mL) stability before and after heat treatment (50~100 °C) in the range of pH 5.0~8.0 was explored using differential scanning (DSC), Fourier transform infrared spectroscopy (FT-IR) and circular dichroism (CD). Turbidity, ζ-potential, particle size, hydrophobicity, and presence of free sulfhydryl groups and total sulfhydryl groups of WSP and κ-WSP were measured. Compared with WSP, light transmittance of κ-WSP decreased after heat treatments at various temperatures (50~100 °C) under the same pH conditions, and the difference of transmittance reached maximum at pH 5.0 and 80 °C. DSC showed that the denaturation temperature of κ-WSP was slightly higher (an average increase of 4.4 ± 1.2 °C) than that of WSP except at pH 4.0 and pH 5.5. At pH 5.0, the ζ-potential value of κ-WSP was higher than (an average increase value of 2.7 ± 0.9) that of WSP with lower particle size distribution, and the hydrophobic content of WSP and κ-WSP showed different trends with increasing temperature. The total thiol groups of both WSP and κ-WSP increased with increasing temperature, except the decrease at 100 °C, while the content of free thiol groups of either WSP or κ-WSP did not change significantly. The FT-IR and CD results showed that the electrostatic combination of WSP and κ-carrageenan did not produce new functional groups, and κ-carrageenan significantly affected the secondary structure of WSP under heat treatment in the range of 80~100°C. These results suggest that κ-carrageenan has a protective effect on the thermal denaturation of WSP of pearl shellfish, and this protective effect is most obvious at isoelectric point (pH 5.0). [ABSTRACT FROM AUTHOR]

Cadmium (Cd) is known to influence the oxidative status of marine organisms and can induce the formation of reactive oxygen species (ROS). Catalase (CAT) is one of the important enzymes involved in scavenging high levels of ROS. In present study, we cloned CAT cDNA and investigated the response of this enzyme at the transcriptional level in the Japanese scallop Mizuhopecten yessoensis exposed to Cd. The full-length CAT cDNA (MyCAT) of 1,870 nucleotides including a 57 bp 5'-UTR, a coding sequence of 1,500 bp and a 313 bp 3'-UTR were identified from the scallop. The deduced amino acid sequence of MyCAT corresponds to 499 amino acids with predicted molecular weight of 56.48 kDa and contains highly conserved motifs of the proximal heme-binding site RLFSYSTH, proximal active signature FNRERIPERVVHAKGGG and three catalytic amino acid residues His, Asn, and Tyr. Its significant homology to CATs from multiple alignments revealed that MyCAT had a high identity with CATs from other mollusks. CAT mRNA expression analysis revealed that expression level was highest in the digestive gland ( p < 0.01) but weak in muscle. Following exposure to 200 and 400 µg/l of Cd, a high amount of Cd was found to have accumulated in the digestive gland and CAT mRNA expression had significantly increased in this organ among 7-day exposed scallops ( p < 0.001). The result demonstrated that antioxidant enzymes such as CAT play important roles in counteracting Cd stress in M. yessoensis. [ABSTRACT FROM AUTHOR]

Marine bivalves accumulate high concentrations of potentially toxic heavy metals in their tissues. We report here our investigation of the accumulation patterns of cadmium (Cd), copper (Cu), and lead (Pb) in tissues of the Japanese scallop Mizuhopecten yessoensis after exposure to artificial seawater containing Cd, Cu, or Pb. Our results revealed that accumulation of these heavy metals by this scallop was associated with certain intracellular metal-binding proteins (MBPs). Cd was accumulated at higher concentrations than Cu and Pb, and most of the accumulated metals were detected in the digestive gland. MBPs from the digestive gland were purified and subjected to a preliminary characterization. Three proteins with molecular masses of approximately 28, 37, and 42 kDa, respectively, were isolated by gel-filtration and anion-exchange column chromatography. Characterization of the partial amino acid sequences of these proteins show high sequence similarity to MBPs and ion-transporters. Metalloprotein profiles in the digestive gland indicated that some proteins were upregulated after metal exposure, suggesting that these proteins are involved in mechanisms of metal accumulation and detoxification in M. yessoensis. [ABSTRACT FROM AUTHOR]