Synaptic transmission involves a fast synchronous phase and a slower asynchronous phase of neurotransmitter release that are regulated by distinct Ca²⁺ sensors. Though the Ca²⁺ sensor for rapid ...exocytosis, synaptotagmin I, has been studied in depth, the sensor for asynchronous release remains unknown. In a screen for neuronal Ca²⁺ sensors that respond to changes in Ca²⁺ with markedly slower kinetics than synaptotagmin I, we observed that Doc2—another Ca²⁺, SNARE, and lipid-binding protein—operates on timescales consistent with asynchronous release. Moreover, up- and downregulation of Doc2 expression levels in hippocampal neurons increased or decreased, respectively, the slow phase of synaptic transmission. Synchronous release, when triggered by single action potentials, was unaffected by manipulation of Doc2 but was enhanced during repetitive stimulation in Doc2 knockdown neurons, potentially due to greater vesicle availability. In summary, we propose that Doc2 is a Ca²⁺ sensor that is kinetically tuned to regulate asynchronous neurotransmitter release.
Display omitted
•A sustainable platform for COVID-19 PPE and CO2 to syngas was studied.•Chemical composition and thermal stability of face mask waste were identified.•Ni catalyst promoted syngas ...production from pyrolysis of disposable face mask.
It becomes common to wear a disposable face mask to protect from coronavirus disease 19 (COVID-19) amid this pandemic. However, massive generations of contaminated face mask cause environmental concerns because current disposal processes (i.e., incineration and reclamation) for them release toxic chemicals. The disposable mask is made of different compounds, making it hard to be recycled. In this regard, this work suggests an environmentally benign disposal process, simultaneously achieving the production of valuable fuels from the face mask. To this end, CO2-assisted thermo-chemical process was conducted. The first part of this work determined the major chemical constituents of a disposable mask: polypropylene, polyethylene, nylon, and Fe. In the second part, pyrolysis study was employed to produce syngas and C1-2 hydrocarbons (HCs) from the disposable mask. To enhance syngas and C1-2 HCs formations, multi-stage pyrolysis was used for more C–C and C–H bonds scissions of the disposable mask. Catalytic pyrolysis over Ni/SiO2 further expedited H2 and CH4 formations due to its capability for dehydrogenation. In the presence of CO2, catalytic pyrolysis additionally produced CO, while pyrolysis in N2 did not produce it. Therefore, the thermo-chemical conversion of disposable face mask and CO2 could be an environmentally benign way to remove COVID-19 plastic waste, generating value-added products.
Despite being the most abundant synaptic vesicle membrane protein, the function of synaptophysin remains enigmatic. For example, synaptic transmission was reported to be completely normal in ...synaptophysin knockout mice; however, direct experiments to monitor the synaptic vesicle cycle have not been carried out. Here, using optical imaging and electrophysiological experiments, we demonstrate that synaptophysin is required for kinetically efficient endocytosis of synaptic vesicles in cultured hippocampal neurons. Truncation analysis revealed that distinct structural elements of synaptophysin differentially regulate vesicle retrieval during and after stimulation. Thus, synaptophysin regulates at least two phases of endocytosis to ensure vesicle availability during and after sustained neuronal activity.
In recent years, many of micropollutants have been widely detected because of continuous input of pharmaceuticals and personal care products (PPCPs) into the environment and newly developed ...state-of-the-art analytical methods. PPCP residues are frequently detected in drinking water sources, sewage treatment plants (STPs), and water treatment plants (WTPs) due to their universal consumption, low human metabolic capability, and improper disposal. When partially metabolized PPCPs are transferred into STPs, they elicit negative effects on biological treatment processes; therefore, conventional STPs are insufficient when it comes to PPCP removal. Furthermore, the excreted metabolites may become secondary pollutants and can be further modified in receiving water bodies. Several advanced treatment systems, including membrane filtration, granular activated carbon, and advanced oxidation processes, have been used for the effective removal of individual PPCPs. This review covers the occurrence patterns of PPCPs in water environments and the techniques adopted for their treatment in STP/WTP unit processes operating in various countries. The aim of this review is to provide a comprehensive summary of the removal and fate of PPCPs in different treatment facilities as well as the optimum methods for their elimination in STP and WTP systems.
•There is a large variation in PPCP removal in STPs and WTPs (−157–100%).•PPCP removal is dependent on compound characteristics and process-specific factors.•Advanced treatment technologies are effective for PPCP removal.
Display omitted
Display omitted
•Strategic use of biochar for CO2 capture and storage (CCS).•Porosity of biochar proves a significant determinant for CCS.•Economic viability of biochar is superior in reference to ...other CCS materials.•Carbon negativity of biochar maximizes the effect of CCS.
Dramatic increase of CO2 emissions to sate the global carbon demand for chemicals, goods, and fuels has been regarded as one of the main contributors triggering global warming. Note that CO2 emissions are over the Earth’s full capacity to assimilate carbons via the natural carbon cycle. In these respects, CO2 capture and sequestration have been considered as one of the strategic principles to cancel out CO2 release from the anthropogenic activities in line with the use of fossil fuels. Thus, it is desirable to develop the efficient CO2 sorptive materials that are economically viable. Among CO2 sorptive materials, biochar (i.e., porous carbon-based materials) has been considered as one of the promising candidates. Indeed, a great deal of researches on biomass has been performed. Based on these rationales, this review laid great emphasis on informing the recent studies of activated biochars for CO2 adsorption, which were fabricated from various biomasses. Also, this review offered the up-to-date knowledge on the physicochemical properties of activated biochars in line with their synthesis procedures. Lastly, the effects of biochar properties on CO2 capture and separation was summarized with in-depth assessment of the activated biochars.
The tremendous amount of food waste from diverse sources is an environmental burden if disposed of inappropriately. Thus, implementation of a biorefinery platform for food waste is an ideal option to ...pursue (e.g., production of value-added products while reducing the volume of waste). The adoption of such a process is expected to reduce the production cost of biodegradable plastics (e.g., compared to conventional routes of production using overpriced pure substrates (e.g., glucose)). This review focuses on current technologies for the production of polyhydroxyalkanoates (PHA) from food waste. Technical details were also described to offer clear insights into diverse pretreatments for preparation of raw materials for the actual production of bioplastic (from food wastes). In this respect, particular attention was paid to fermentation technologies based on pure and mixed cultures. A clear description on the chemical modification of starch, cellulose, chitin, and caprolactone is also provided with a number of case studies (covering PHA-based products) along with a discussion on the prospects of food waste valorization approaches and their economic/technical viability.
Display omitted
•The tremendous amount of food waste (FW) is produced from diverse sources.•To resolve FW problems, implementation of a biorefinery platform for FW is essential.•The adoption of such a process can produce value-added products while reducing the waste.•This review focuses on current technologies for the production of polyhydroxyalkanoates (PHA).•Prospects of FW valorization are discussed along with their economic/technical viability.
•CO2 plays a critical role in characteristics of pyrolytic products.•The use of CO2 improves thermal efficiency of pyrolysis of waste feedstocks.•CO2-assisted pyrolysis suppresses harmful chemical ...formation.
Pyrolysis is a thermochemical conversion method for the production of energy and chemicals from carbonaceous substances. In this review, we emphasize the recent progress in the pyrolysis of waste feedstocks in the presence of carbon dioxide (CO2). CO2-assisted pyrolysis is compared to typical pyrolysis (i.e., pyrolysis under inert environment, such as nitrogen). It has been shown that CO2 plays a crucial role in increasing the yield of combustible permanent gas (e.g., carbon monoxide) while decreasing tar yield. CO2-assisted pyrolysis is also an attractive technique to treat waste (municipal solid waste, plastic waste, etc.) because CO2 enhances the thermal cracking of volatile species, thereby suppressing the formation of harmful chemical compounds, such as benzene derivatives and polycyclic aromatic hydrocarbons. In addition to highlighting the recent achievements in the CO2-assisted pyrolysis processes, we discuss the points that should be considered for future research.
Rare earth elements (REEs) are essential raw materials for emerging renewable energy resources and ‘smart’ electronic devices. Global REE demand is slated to grow at an annual rate of 5% by 2020. ...This high growth rate will require a steady supply base of REEs in the long run. At present, China is responsible for 85% of global rare earth oxide (REO) production. To overcome this monopolistic supply situation, new strategies and investments are necessary to satisfy domestic supply demands. Concurrently, environmental, economic, and social problems arising from REE mining must be addressed. There is an urgent need to develop efficient REE recycling techniques from end-of-life products, technologies to minimize the amount of REEs required per unit device, and methods to recover them from fly ash or fossil fuel-burning wastes.
Dolichol and natural rubber are representative cis-polyisoprenoids in primary and secondary metabolism, respectively. Their biosynthesis is catalyzed by cis-prenyltransferase (CPT) by sequential ...condensations of isopentenyl diphosphates (IPPs) to a priming molecule. Although prokaryotic CPTs have been well characterized, the mechanism of eukaryotic CPTs in cis-polyisoprene biosynthesis was only recently revealed. It was shown that eukaryotes have evolved a unique protein complex, comprised of CPT and CPT-binding protein (CBP), to synthesize cis-polyisoprenoids. In the context of this new discovery, we found discrepancies in literature for CPT or CBP biochemical assays and in vivo CPT complementation using rer2 (yeast CPT) yeast mutant. Our study here shows that rer2 revertants occur at a frequency that cannot be disregarded and are likely accountable for the results that cannot be explained by the CPT/CBP heteroprotein complex model. To make a stable mutant, SRT1 gene (secondary CPT expressed at a basal level in yeast) was additionally deleted in the rer2Δ mutant background. This stable rer2Δ srt1Δ strain was then used to individually or simultaneously express Arabidopsis CPT1 (AtCPT1, At2g17570) and CBP (AtLEW1, At1G11755). We found that the simultaneous expression of Arabidopsis CPT1 and AtLEW1 effectively complements the rer2Δ srt1Δ strain, whereas the individual expression of AtCPT1 alone or AtLEW1 alone failed to rescue the yeast mutant. Microsomes from the dual expresser showed an efficient incorporation of IPPs into cis-polyisoprenoid (30% in 2h). These results showed that the CPT/CBP heteroprotein complex model is valid in Arabidopsis thaliana. Experimental details of these results are described in this methodology paper.
PDF
