Photovoltaic Device with over 5% Efficiency Based on an n‐Type Ag2ZnSnSe4 Absorber

The kesterite material Cu₂ZnSn(S,Se)₄ (CZTSSe) is an attractive earth‐abundant semiconductor for photovoltaics. However, the power conversion efficiency is limited by a large density of I–II antisite defects, which cause severe band tailing and open‐circuit voltage loss. Ag₂ZnSnSe₄ (AZTSe) is a promising alternative to CZTSSe with a substantially lower I–II antisite defect density and smaller band tailing. AZTSe is weakly n‐type, and this study reports for the first time on how the carrier density is impacted by stoichiometry. This study presents the first‐ever photovoltaic device based on AZTSe, which exhibits an efficiency of 5.2%, which is the highest value reported for an n‐type thin‐film absorber. Due to the weakly n‐type nature of the absorber, a new architecture is employed (SnO:F/AZTSe/MoO₃/ITO) to replace conventional contacts and buffer materials. Using this platform, it is shown that the band tailing parameter in AZTSe more closely resembles that of CIGSe than CZTSSe, underscoring the strong promise of this absorber. In demonstrating the ability to collect photogenerated carriers from AZTSe, this study paves the way for novel thin‐film heterojunction architectures where light absorption in the n‐type device layer can supplement absorption in the p‐type layer as opposed to producing a net optical loss.     

The inhibitory effects of polyoxyethylene detergents on human erythrocyte acetylcholinesterase and Ca2+ + Mg2+ ATPase

The activities of acetylcholinesterase and Ca2+ + Mg2+ ATPase were measured following treatment of human erythrocyte membranes with nonsolubilizing and solubilizing concentrations of Triton X-100. A concentration of 0.1% (v/v) Triton X-100 caused a significant inhibition of both enzymes. The inhibition appears to be caused by perturbations in the membrane induced by Triton X-100 incorporation. No acetylcholinesterase activity and little Ca2+ + Mg2+ ATPase activity were detected in the supernatant at 0.05% Triton X-100 although this same detergent concentration induced changes in the turbidity of the membrane suspension. Also, no inhibition of soluble acetylcholinesterase was observed over the entire detergent concentration range. The inhibition of these enzymes at 0.1% Triton X-100 was present over an eightfold range of membrane protein in the assay indicating an independence of the protein/detergent ratio. The losses in activities of these two enzymes could be prevented by either including phosphatidylserine in the Triton X-100 suspension or using Brij 96 which has the same polyoxyethylene polar head group but an oleyl hydrophobic tail instead of the p-tert-octylphenol group of Triton X-100. The results are discussed in regard to the differential recovery of enzyme activities over the entire detergent concentration range.     

Playing God and tampering with nature: popular labels for real concerns in synthetic biology

Public engagement in science with diverse cross-sections of the community is considered a critical aspect of responsible biotechnological innovation. While the research community shows willingness to engage with both ambivalent and supportive audiences about potentially disruptive technological advances, there is less enthusiasm for engaging with groups who hold deeply opposing views to such advances. ‘Playing God’ and ‘tampering with nature’ are popular examples of intrinsic objections often made in opposition to the development or use of novel genetic technologies. Historically appearing in arguments against the pursuit of genetically modified organisms in agriculture and food industries, intrinsic objections have previously been labelled by the science community as inconsistent, non-scientific, and vague. Now found in a range of innovation contexts, the domain of synthetic biology appears to attract such objections consistently. We present the findings from a large Australian study (N?=?4593) which suggests ‘playing God’ objections and their variants can be multilayered and, at times, accompanied by meaningful information about risk perceptions. We use qualitative analysis of open-ended responses from an online survey to show how these objections are articulated in response to selected synthetic biology applications across environmental and health domains. Our research invites a rethink of how the synthetic biology community perceives, and engages with, people who express intrinsic objections. These people may additionally hold extrinsic concerns that may be potentially addressed, or at least reasonably considered, through dialogue. We offer some concluding remarks for engaging with publics who employ these types of arguments to communicate unease with aspects of technology development and use.

     

Ascorbate protects against tert-butyl hydroperoxide inhibition of erythrocyte membrane Ca2+ + Mg2(+)-ATPase

The incubation of erythrocyte suspensions or isolated membranes containing a residual amount of hemoglobin (0.04% of original cellular hemoglobin) with tert-butyl hydroperoxide (tBHP, 0.5 mM) caused significant inhibition of basal and calmodulin-stimulated Ca2+ + Mg2(+)-ATPase activities and the formation of thiobarbituric acid reactive products measured as malondialdehyde. In contrast, the treatment of white ghosts (membranes not containing hemoglobin) with tBHP (0.5 mM) did not lead to appreciable enzyme inhibition within the first 20 min and did not result in malondialdehyde (MDA) formation. However, the addition of either 10 microM hemin or 100 microM ferrous chloride + 1 mM ADP to white ghosts produced hydroperoxide effects similar to those in pink ghosts (membranes with 0.04% hemoglobin). The concentrations of hemin and ferrous chloride which caused half-maximal inhibition of Ca2+ + Mg2(+)-ATPase activity at 10 min were 0.5 and 30 microM, respectively. The effects of several antioxidants (mannitol, thiourea, hydroxyurea, butylated hydroxytoluene, and ascorbate) were investigated for their protective effects against oxidative changes resulting from tBHP treatment. Over a 30-min incubation period only ascorbate significantly reduced the enzyme inhibition, MDA formation, and protein polymerization. Thiourea and hydroxyurea decreased MDA formation and protein polymerization but failed to protect against the enzyme inhibition. Butylated hydroxytoluene was similar to thiourea and hydroxyurea but with better protection at 10 min. Mannitol, under these conditions, was an ineffective antioxidant for all parameters tested.     

Insulin protects pancreatic acinar cells from cytosolic calcium overload and inhibition of plasma membrane calcium pump

Acute pancreatitis is a serious and sometimes fatal inflammatory disease of the pancreas without any reliable treatment or imminent cure. In recent years, impaired metabolism and cytosolic Ca(2+) ([Ca(2+)](i)) overload in pancreatic acinar cells have been implicated as the cardinal pathological events common to most forms of pancreatitis, regardless of the precise causative factor. Therefore, restoration of metabolism and protection against cytosolic Ca(2+) overload likely represent key therapeutic untapped strategies for the treatment of this disease. The plasma membrane Ca(2+)-ATPase (PMCA) provides a final common path for cells to "defend" [Ca(2+)](i) during cellular injury. In this paper, we use fluorescence imaging to show for the first time that insulin treatment, which is protective in animal models and clinical studies of human pancreatitis, directly protects pancreatic acinar cells from oxidant-induced cytosolic Ca(2+) overload and inhibition of the PMCA. This protection was independent of oxidative stress or mitochondrial membrane potential but appeared to involve the activation of Akt and an acute metabolic switch from mitochondrial to predominantly glycolytic metabolism. This switch to glycolysis appeared to be sufficient to maintain cellular ATP and thus PMCA activity, thereby preventing Ca(2+) overload, even in the face of impaired mitochondrial function.     

Hydroperoxides selectively inhibit human erythrocyte membrane enzymes

Treatment of washed erythrocytes with tert-butyl hydroperoxide (0.5 mM, 10 min) inhibited basal Ca2+ + Mg2+-ATPase activity by 40% and calmodulin-stimulated activity by 54%. The inhibition was accompanied by the formation of methemoglobin and the aggregation of some membrane proteins into a high-molecular-weight polymer. Membranes, isolated from washed erythrocytes, showed a similar pattern of inhibition. Basal Ca2+ + Mg2+-ATPase activity was inhibited 50% at 10 min and 70% at 30 min while calmodulin-stimulated activity was inhibited 70% at 10 min and 84% at 30 min. Thiobarbituric acid-reactive products formed slowly during the first 10 min and then increased sharply between 10 and 30 min. The polymerization of membrane proteins was also observed during the tert-butyl hydroperoxide exposure. Inhibition of erythrocyte membrane enzymes was selective. The Na+ + K+-stimulated Mg2+ ATPase, like the Ca2+ + Mg2+-ATPase, was sensitive to membrane oxidation but the activities of Mg2+-ATPase and acetylcholinesterase were less inhibited by tert-butyl hydroperoxide. Acetylcholinterase was found to be very resistant to hydroperoxide treatment with less than 10% loss of activity. The effects of two other hyproperoxides on enzyme inhibition were studied also. Cumene hydroperoxide (0.5 mM) was found to be as potent as tert-butyl hydroperoxide but hydrogen peroxide at 10 mM did not produce thiobarbituric acid-reactive products or inhibit Ca2+ + Mg2+-ATPase activity until after 20 min. The selective effects of peroxides on these enzyme activities are discussed.     

SIDE effects associated with use of nevirapine in HIV treatment naïve patients with respect to baseline CD4 count

The rapid growth of bioscience in China is considered.     

A simple method for hemoglobin measurement in cell culture system.

A simple method of hemoglobin analysis in a cell culture system is described. Hemoglobins synthesized in cell cultures are labeled with radioactive amino acids. The cell extract containing radiolabeled hemoglobin is mixed with A, F, S, C, hemoglobin markers and separated by cellulose acetate electrophoresis. Individual bands of hemoglobin are cut from the gel and analyzed for radioactivity. This method is especially useful for determination of newly synthesized minute amount of hemoglobin in cell extracts that are difficult to visualize by staining procedure.