Synthesis and antioxidant evaluation of coumarin-functionalised chitosan: A potent, non-toxic free radical scavenging compound

In the present study, we designed to link the coumarin molecule to chitosan via a triazole group and synthesized chitosan-coumarin derivatives, which were further quaternized in one step in order to further improve their solubility to obtain a second series of chitosan-coumarin ammonium salt derivatives. The structures of these chitosan derivatives were verified by FT-IR and 1 H NMR. They were tested for their antioxidant activities. The experimental results showed that the derivatives had excellent free radical scavenging ability. The introduction of the coumarin moiety significantly improved the antioxidant activity, and the scavenging capacity was much higher than that of the chitosan feedstock in all three antioxidant tests. Overall, the scavenging capacity of chitosan-coumarin ammonium salt derivatives was slightly higher than that of chitosan-coumarin derivatives, with the highest scavenging rates in all three tests. Compound 8B scavenged 98.74 % (0.01 mg/mL) of superoxide anion radicals, compound 8D scavenged 95.5 % (0.3 mg/mL) of DPPH radicals and compound 8A scavenged 92.97 % (0.2 mg/mL) of hydroxyl radicals. Toxicity assays used L929 cells demonstrated that there was no significant toxicity of the derivatives. The results indicated that the chitosan derivatives described herein were safe and non-toxic and have good antioxidant activity

Field and numerical investigation of groundwater flow and dissolved inorganic nitrogen (DIN) dynamics in a sandy nearshore aquifer

Nutrients delivered to the coastal ocean via submarine groundwater discharge (SGD) can have a major impact on marine ecosystems. The flux of nutrients delivered via this pathway can be modified by biogeochemical processes occurring in coastal nearshore aquifers. This study combines field investigations with numerical simulations to characterize patterns of groundwater flow, salinity and dissolved inorganic nitrogen (DIN) in a permeable nearshore aquifer and to quantify SGD and associated DIN fluxes to the ocean. At the field study site, an upper saline plume (USP) and saltwater wedge with low DIN concentrations were observed together with a fresh groundwater zone with high DIN concentrations. Seawater infiltration predominantly occurred in the intertidal zone, contributing 85% of the total infiltration, with the greatest infiltration occurring in the upper-middle intertidal zone. The simulations indicate that the USP expanded and contracted through the tidal cycle, and the width of the high-DIN freshwater discharge zone also varying. The freshwater discharge zone was narrower around the high tide period due to expansion of the overlying low-DIN zone associated with the USP. Over the simulated period, only approximately 30% of the DIN entering the nearshore aquifer ultimately discharged to the ocean. The findings of this combined field and numerical study are needed to inform future field and numerical investigations examining the fate of DIN in nearshore aquifers

Water exchange frequency affects the fractions of sulfur and heavy metals in mariculture sediments

Water exchange is a key step in mariculture activities. However, the impact of water exchange frequency (WEF) on the environmental behavior of sulfur and heavy metals is not well understood. In this study, the migration and transformation of sulfur and heavy metals in mariculture sediments under different WEFs were investigated. The results indicated that high WEF would be unfavorable to overlying water quality, while increased acid volatile sulfur (AVS) in the sediments (11.13 mu mol/g). High WEF accelerated the release of heavy metals from bottom sediments and their enrichment in the surface layer, leading to an increase in heavy metal content in the surface sediments, with Cd showing particularly significant changes (CV, similar to 20%). Moreover, the WEF also had an obvious effect on the Cd fraction (CV>10%). The increase in acid-soluble Pb inhibited the conversion of AVS to chromium (II)-reducible sulfur (CRS) in the sediments, enhancing the sediment aging process. An appropriate frequency of water exchange (once every 5 days) could increase the abundance and diversity of bacteria and help to shape specific microorganisms. Changes in heavy metals in the surface sediments caused Firmicutes to become the most affected bacterial species by the WEF. The functional flora involved in the sulfur cycle were lesser affected by the WEF (CV, similar to 5%), whereas those involved in the nitrogen cycle were more affected (CV >17%). The findings provide guidance for scientific mariculture

Synergistic effects of ocean acidification and sulfamethoxazole on immune function, energy allocation, and oxidative stress in Trochus niloticus

Ocean acidification, a major consequence of climate change, poses significant threats to marine organisms, particularly when combined with other environmental stressors such as chemical pollution. This study investigated the physiological responses of Trochus niloticus to a 28-day exposure of ocean acidification and/or sulfamethoxazole, a commonly detected antibiotic in the South China Sea. Exposure to either acidification or sulfamethoxazole individually triggered adaptive responses through immune activation, antioxidant reactions, and metabolic adjustments. However, concurrent exposure resulted in significant adverse effects, including compromised immunity, oxidative damage, and disrupted energy budget. These findings provide new insights into how ocean acidification interacts with antibiotic pollution to synergistically impact marine gastropods, suggesting that multiple stressors may pose greater threats to T. niloticus populations than single stressors alone

Water exchange frequency affects the fractions of sulfur and heavy metals in mariculture sediments

Water exchange is a key step in mariculture activities. However, the impact of water exchange frequency (WEF) on the environmental behavior of sulfur and heavy metals is not well understood. In this study, the migration and transformation of sulfur and heavy metals in mariculture sediments under different WEFs were investigated. The results indicated that high WEF would be unfavorable to overlying water quality, while increased acid volatile sulfur (AVS) in the sediments (11.13 mu mol/g). High WEF accelerated the release of heavy metals from bottom sediments and their enrichment in the surface layer, leading to an increase in heavy metal content in the surface sediments, with Cd showing particularly significant changes (CV, similar to 20%). Moreover, the WEF also had an obvious effect on the Cd fraction (CV>10%). The increase in acid-soluble Pb inhibited the conversion of AVS to chromium (II)-reducible sulfur (CRS) in the sediments, enhancing the sediment aging process. An appropriate frequency of water exchange (once every 5 days) could increase the abundance and diversity of bacteria and help to shape specific microorganisms. Changes in heavy metals in the surface sediments caused Firmicutes to become the most affected bacterial species by the WEF. The functional flora involved in the sulfur cycle were lesser affected by the WEF (CV, similar to 5%), whereas those involved in the nitrogen cycle were more affected (CV >17%). The findings provide guidance for scientific mariculture

A method for breeding new anti-vibrio variety of clam

本发明涉及海产经济贝类遗传育种技术领域，特别是一种毛蚶抗弧菌新品种的育种方法。具体为利用半致死浓度的副溶血弧菌胁迫成体毛蚶，对15％存活的个体进行恢复以8％留种率筛选获得抗弧菌毛蚶种贝，进行室内车间育肥将毛蚶培育至性腺发育成熟，并于诱导产卵前通过灭活的副溶血弧菌诱导毛蚶产生可遗传的免疫因子；而后诱导毛蚶产卵，获得毛蚶F1代抗弧菌品系，再将F1代采用“北育南养”的繁育和养殖技术快速将毛蚶苗种培育至性成熟；此后，每年按照胁迫筛选种贝、增强子代免疫力和“北育南养”的方式连续选育即获得遗传稳定、性状优良的毛蚶抗弧菌新品种。本发明方法可显著提高毛蚶的抗弧菌能力和养殖存活率，提高毛蚶养殖业的良种保存与供应能力

A method for breeding new anti-vibrio variety of clam

本发明涉及海产经济贝类遗传育种技术领域，特别是一种毛蚶抗弧菌新品种的育种方法。具体为利用半致死浓度的副溶血弧菌胁迫成体毛蚶，对15％存活的个体进行恢复以8％留种率筛选获得抗弧菌毛蚶种贝，进行室内车间育肥将毛蚶培育至性腺发育成熟，并于诱导产卵前通过灭活的副溶血弧菌诱导毛蚶产生可遗传的免疫因子；而后诱导毛蚶产卵，获得毛蚶F1代抗弧菌品系，再将F1代采用“北育南养”的繁育和养殖技术快速将毛蚶苗种培育至性成熟；此后，每年按照胁迫筛选种贝、增强子代免疫力和“北育南养”的方式连续选育即获得遗传稳定、性状优良的毛蚶抗弧菌新品种。本发明方法可显著提高毛蚶的抗弧菌能力和养殖存活率，提高毛蚶养殖业的良种保存与供应能力

Field and numerical investigation of groundwater flow and dissolved inorganic nitrogen (DIN) dynamics in a sandy nearshore aquifer

Nutrients delivered to the coastal ocean via submarine groundwater discharge (SGD) can have a major impact on marine ecosystems. The flux of nutrients delivered via this pathway can be modified by biogeochemical processes occurring in coastal nearshore aquifers. This study combines field investigations with numerical simulations to characterize patterns of groundwater flow, salinity and dissolved inorganic nitrogen (DIN) in a permeable nearshore aquifer and to quantify SGD and associated DIN fluxes to the ocean. At the field study site, an upper saline plume (USP) and saltwater wedge with low DIN concentrations were observed together with a fresh groundwater zone with high DIN concentrations. Seawater infiltration predominantly occurred in the intertidal zone, contributing 85% of the total infiltration, with the greatest infiltration occurring in the upper-middle intertidal zone. The simulations indicate that the USP expanded and contracted through the tidal cycle, and the width of the high-DIN freshwater discharge zone also varying. The freshwater discharge zone was narrower around the high tide period due to expansion of the overlying low-DIN zone associated with the USP. Over the simulated period, only approximately 30% of the DIN entering the nearshore aquifer ultimately discharged to the ocean. The findings of this combined field and numerical study are needed to inform future field and numerical investigations examining the fate of DIN in nearshore aquifers

Insights into the hydrogen-fueled bioreduction of vanadium(V) by marine<i> Shewanella</i> sp. FDA-1: Process and mechanism

Microbial-driven V(V) reduction plays a crucial role in its biogeochemical cycle, yet the mechanisms underlying this bioreduction remain inadequately understood. While the effectiveness of organic compounds as electron donors in facilitating bacterial reduction of V(V) has been established, the role of inorganic electron donors in initiating this process at the level of pure cultured bacteria has not been explored. In this study, we report on a marine Shewanella sp. FDA-1 that utilizes hydrogen (H-2) as an energy source to reduce V(V). In addition, the reduction mechanism was investigated through a combination of genomics, RT-qPCR, heterologous expression of key proteins, extracellular secretion analyses, and electron transfer activity assays. Our results demonstrate that H-2 serves as an effective electron donor, enabling Shewanella sp. FDA-1 to reduce V(V) across various salinities (2-7 %) and pH values (5-9). When exposed to 5 mM V(V), the presence of 1-20 mL of H-2 resulted in V(V) bioreduction rates ranging from 0.039 to 0.11 h(-1) (R-2 > 0.73). Amorphous V(IV) compounds were characterized as reduction products using XRD, XPS, FTIR, and SEM. Mechanistic studies indicate that the glutathione system, cytochromes, and extracellular substances such as riboflavin play important roles in V(V) reduction (p < 0.05). Furthermore, our findings reveal that the addition of H-2 and lactate triggers different response sequences among these three reduction pathways, suggesting distinct reduction mechanisms between organic and inorganic electron donors. These insights enhance our understanding of microbial vanadium transformation and provide valuable guidance for developing novel H2-based remediation technologies for vanadium-contaminated environments

Efficient purification and excitation energy transfer characterization of phycoerythrin 545 from<i> Rhodomonas</i> sp.

Cryptomonad phycoerythrin 545 (PE545) is an important type of phycobiliprotein in basic research and technological innovations. Herein, we report a minimalistic hydrophobic chromatography method for its purification. High purity was achieved, with a purity ratio (A545/A280) of 13.66 and a recovery ratio of 78.63 %. Following SDS-PAGE, Coomassie Brilliant Blue staining revealed three bands at 9 kDa, 10 kDa, and 20 kDa, corresponding to alpha 1, alpha 2 and beta subunits. Multiple spectral characteristics were analyzed to ensure that optical activity was consistent with that of the natural protein. Absorption and fluorescence spectroscopies of purified PE545 displayed a strong absorption peak at 545 nm, a shoulder peak at 564 nm, and a fluorescence emission peak at 587 nm, which confirmed unchanged energy transfer properties. Furthermore, the structural and functional integrity, especially the existence of strongly coupled central chromophore pairs with excitation delocalization, was verified by circular dichroism and ultrafast absorption spectroscopy. From the studies of ultrafast absorption spectroscopy of excitation energy transfer (EET) of PE545, four decay components with lifetimes at 0.5 ps, 2.2 ps, 63 ps, and 3000 ps were obtained. In addition, the dynamics of these components confirmed the EET pathways from the central PEB chromophore pairs to the peripheral pigments and localized in the lowest state. Our work will be of considerable value for both fundamental research and applications of PE545