Bifunctional Gas Diffusion Electrode Enables In Situ Separation and Conversion of CO2 to Ethylene from Dilute Stream.

The requirement of concentrated carbon dioxide (CO2 ) feedstock significantly limits the economic feasibility of electrochemical CO2 reduction (eCO2 R) which often involves multiple intermediate processes, including CO2 capture, energy-intensive regeneration, compression, and transportation. Herein, a bifunctional gas diffusion electrode (BGDE) for separation and eCO2 R from a low-concentration CO2 stream is reported. The BGDE is demonstrated for the selective production of ethylene (C2 H4 ) by combining high-density-polyethylene-derived porous carbon (HPC) as a physisorbent with polycrystalline copper as a conversion catalyst. The BGDE shows substantial tolerance to 10 vol% CO2 exhibiting a Faradaic efficiency of ≈45% toward C2 H4 at a current density of 80 mA cm-2 , outperforming previous reports that utilized such partial pressure (PCO2 = 0.1 atm and above) and unaltered polycrystalline copper. Molecular dynamics simulation and mixed gas permeability assessment reveal that such selective performance is ensured by high CO2 uptake of the microporous HPC as well as continuous desorption owing to the molecular diffusion and concentration gradient created by the binary flow of CO2 and nitrogen (CO2 |N2 ) within the sorbent boundary. Based on detailed techno-economic analysis, it is concluded that this in situ process can be economically compelling by precluding the C2 H4 production cost associated with the energy-intensive intermediate steps of the conventional decoupled process.

Synthesis of Hydrogels with Antifouling Properties As Membranes for Water Purification.

Hydrogels have been widely utilized to enhance the surface hydrophilicity of membranes for water purification, increasing the antifouling properties and thus achieving stable water permeability through membranes over time. Here, we report a facile method to prepare hydrogels based on zwitterions for membrane applications. Freestanding films can be prepared from sulfobetaine methacrylate (SBMA) with a crosslinker of poly(ethylene glycol) diacrylate (PEGDA) via photopolymerization. The hydrogels can also be prepared by impregnation into hydrophobic porous supports to enhance the mechanical strength. These films can be characterized by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) to determine the degree of conversion of the (meth)acrylate groups, using goniometers for hydrophilicity and differential scanning calorimetry (DSC) for polymer chain dynamics. We also report protocols to determine the water permeability in dead-end filtration systems and the effect of foulants (bovine serum albumin, BSA) on membrane performance.

Membranes with Surface-Enhanced Antifouling Properties for Water Purification.

Membrane technology has emerged as an attractive approach for water purification, while mitigation of fouling is key to lower membrane operating costs. This article reviews various materials with antifouling properties that can be coated or grafted onto the membrane surface to improve the antifouling properties of the membranes and thus, retain high water permeance. These materials can be separated into three categories, hydrophilic materials, such as poly(ethylene glycol), polydopamine and zwitterions, hydrophobic materials, such as fluoropolymers, and amphiphilic materials. The states of water in these materials and the mechanisms for the antifouling properties are discussed. The corresponding approaches to coat or graft these materials on the membrane surface are reviewed, and the materials with promising performance are highlighted.

Essential fatty acid deficiency induces fatty acid desaturase expression in rat epididymis, but not in testis.

On the molecular level, essential fatty acid deficiency (EFAD) has been associated with induced fatty acid (FA) desaturase expression and activity in several tissues. However, there seem to be exceptions. In the present study, we examine the effects of EFAD in the male rat genital tract, combining FA analysis, gene expression studies, and morphological evaluation of epididymal spermatozoa. When feeding 21-day-old Wistar rats, a fat-free diet for 6 weeks, an increase in 18:1n-9 and 20:3n-9 and a concomitant decrease in the 18:2n-6 and 20:4n-6 species are seen in testis, as well as in liver. However, with regard to desaturase expression the rat testis seems to be unresponsive to EFAD conditions, in contrast to other organs studied. In the sexually mature testis none of the desaturases (SCD1, SCD2, D5D, or D6D) are induced in response to lowered contents of polyunsaturated FAs. This also applies to caput epididymis, while EFAD sensitivity is regained in cauda epididymis, where the desaturases are upregulated. The FA profile of epididymal spermatozoa is increasingly affected by EFAD during the transport from testis to cauda epididymis. Furthermore, a significant increase in the number of abnormal spermatozoa is observed in cauda epididymis.

De novo synthesized RelB mediates TNF-induced up-regulation of the human polymeric Ig receptor.

Secretory Abs, which operate in a principally noninflammatory fashion, constitute the first line of acquired immune defense of mucosal surfaces. Such Abs are generated by polymeric Ig receptor (pIgR)-mediated export of dimeric IgA and pentameric IgM. TNF activates a proinflammatory gene repertoire in mucosal epithelial cells and also enhances pIgR expression. In this study we show that TNF-induced up-regulation of the human pIgR critically depends on an NF-kappa B site and flanking sequences within a 204-bp region of the first intron in the pIgR gene, a region largely overlapping with a recently characterized IL-4-responsive enhancer. The intronic NF-kappa B site was rapidly bound by NF-kappa B p65/p50 heterodimers present in nuclear extracts after TNF treatment of HT-29 cells, but a more delayed binding of RelB agreed better with the slow, protein synthesis-dependent, transcriptional activation of the pIgR gene. Overexpression of NF-kappa B p65 caused transient up-regulation of a pIgR-derived reporter gene, whereas overexpression of RelB showed a stronger and more sustained effect. Finally, we demonstrated that inhibition of endogenous RelB by RNA interference severely reduced the TNF responsiveness of our pIgR-derived reporter gene. Thus, TNF-induced signaling pathways required for up-regulated pIgR expression appear to differ from those of the proinflammatory gene repertoire.

Expression and regulation of delta5-desaturase, delta6-desaturase, stearoyl-coenzyme A (CoA) desaturase 1, and stearoyl-CoA desaturase 2 in rat testis.

In mammalian cells, essential polyunsaturated fatty acids (PUFAs) are converted to longer PUFAs by alternating steps of elongation and desaturation. In contrast to other PUFA-rich tissues, the testis is continuously drained of these fatty acids as spermatozoa are transported to the epididymis. Alteration of the germ cell lipid profile from spermatogonia to condensing spermatids and mature spermatozoa has been described, but the male gonadal gene expression of the desaturases, responsible for the PUFA-metabolism, is still not established. The focus of this study was to characterize the expression and regulation of stearoyl-CoA desaturase 1 (SCD1), stearoyl-CoA desaturase 2 (SCD2), and Delta5- and Delta6-desaturase in rat testis. Desaturase gene expression was detected in testis, epididymis, and separated cells from seminiferous tubulus using Northern blot analysis. For the first time, SCD1 and SCD2 expression is demonstrated in rat testis and epididymis, both SCDs are expressed in epididymis, while testis mainly contains SCD2. Examination of the testicular distribution of Delta5- and Delta6-desaturase and SCD1 and SCD2 shows that all four desaturases seem to be localized in the Sertoli cells, with far lower expression in germ cells. In light of earlier published results showing that germ cells are richer in PUFAs than Sertoli cells, this strengthens the hypothesis of a lipid transport from the Sertoli cells to the germ cells. As opposed to what is shown in liver, Delta5- and Delta6-desaturase mRNA levels in Sertoli cells are up-regulated by dexamethasone. Furthermore, dexamethasone induces SCD2 mRNA. Insulin also up-regulates these three genes in the Sertoli cell, while SCD1 mRNA is down-regulated by both insulin and dexamethasone. Delta5- and Delta6-desaturase, SCD1, and SCD2 are all up-regulated by FSH. A similar up-regulation of the desaturases is observed when treating Sertoli cells with (Bu)2cAMP, indicating that the desaturase up-regulation observed with FSH treatment results from elevated levels of cAMP. Finally, testosterone has no influence on the desaturase gene expression. Thus, FSH seems to be a key regulator of the desaturase expression in the Sertoli cell.

Partitioning of polyunsaturated fatty acid oxidation between mitochondria and peroxisomes in isolated rat hepatocytes studied by HPLC separation of oxidation products.

The extent of mitochondrial and peroxisomal contribution to beta-oxidation of 18-, 20- and 24-carbon n-3 and n-6 polyunsaturated fatty acids (PUFAs) in intact rat hepatocytes is not fully clear. In this study, we analyzed radiolabeled acid soluble oxidation products by HPLC to identify mitochondrial and peroxisomal oxidation of 24:5n-3, 18- and 20-carbon n-3 and n-6 PUFAs. Mitochondrial fatty acid oxidation produced high levels of ketone bodies, tricarboxylic acid cycle intermediates and CO(2), while peroxisomal beta-oxidation released acetate. Inhibition of mitochondrial fatty acid oxidation with 2-tetradecylglycidic acid (TDGA), high amounts of [14C]acetate from oxidation of 24:5n-3, 18- and 20-carbon PUFAs were observed. In the absence of TDGA, high amounts of [14C]-labeled mitochondrial oxidation products were formed from oxidation of 24:5n-3, 18- and 20-carbon PUFAs. With 18:1n-9, high amounts of mitochondrial oxidation products were formed in the absence of TDGA, and TDGA strongly suppressed the oxidation of this fatty acid. Data of this study indicated that a shift in the partitioning from mitochondrial to peroxisomal oxidation differed for each individual fatty acid and is a specific property of 24:5n-3, 18- and 20-carbon n-3 and n-6 PUFAs.[14C]22:6n-3 was detected with [3-14C]24:5n-3, but not with [1-14C]24:5n-3 as the substrate, while [14C]16:0 was detected with [1-14C]24:5n-3, but not with [3-14C]24:5n-3 as the substrate. Furthermore, the amounts of 14CO(2) were similar when cells were incubated with [3-14C]24:5n-3 versus [1-14C]24:5n-3. These findings indicated that the proportion of 24:5n-3 oxidized in mitochondria was high, and that 24:5n-3 and 24:6n-3 were mostly beta-oxidized only one cycle in peroxisomes.