No abstract

Isolated rat hepatocytes were incubated in a medium containing 0.1 mM [32P]phosphate (0.1 mCi/ml) before exposure to epinephrine. glucagon or vasopressin. 32P-labeled glycogen synthase was purified from extracts of control or hormone-treated cells by the use of specific antibodies raised to rabbit skeletal muscle glycogen synthase. Analysis of the immunoprecipitates by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate indicated that a single 321'-labeled polypeptide, apparent M , 88 000, was removed specifically by the antibodies and corresponded to glycogen synthase. Similar electrophoretic analysis of CNBr fragments prepared from the immunoprecipitate revealed that 32P was distributed between two fragments, of apparent M, 14000 (CB-1) and 28000 (CB-2). Epinephrine, vasopressin or glucagon increased the 32P content of the glycogen synthase subunit. CB-2 phosphorylation was increased by all three hormones while CB-lwas most affected by epinephrine and vasopressin. These effects correlated with a decrease in glycogen synthase activity. From studies using rat liver glycogen synthase, purified by conventional methods and phosphorylated in vitvo by individual protein kinases, it was found that electrophoretically simi1a.r CNBr fragments could be obtained. However, neither cyclic-AMP-dependent protein kinase nor three different Ca2 +-dependent enzymes (phosphorylase kinase, calmodulin-dependent protein kinase, and protein kinase C) were effective in phosphorylating CB-2. The protein kinases most effective towards CB-2 were the Ca2+ and cyclic-nucleotide-independent enzymes casein kinase 11 (PC,,,) and F,/GSK-3. The results demonstrate that rat liver glycogen synthase undergoes multiple phosphorylation in whole cells and that stimulation of cells by glycogenolytic hormones can modify the phosphorylation of at least two distinct sites in the enzyme.

Insulin causes rapid phosphorylation of the beta subunit (Mr = 95,000) of its receptor in broken cell preparations. This occurs on tyrosine residues and is due to activation of a protein kinase which is contained in the receptor itself. In the intact cell, insulin also stimulates the phosphorylation of the receptor and other cellular proteins on serine and threonine residues. In an attempt to find a protein that might link the receptor tyrosine kinase to these serine/threonine phosphorylation reactions, we have studied the interaction of a partially purified preparation of insulin receptor with purified preparations of serine/threonine kinases known to phosphorylate glycogen synthase. No insulin-dependent phosphorylation was observed when casein kinases I and II, phosphorylase kinase, or glycogen synthase kinase 3 was incubated in vitro with the insulin receptor. These kinases also failed to phosphorylate the receptor. By contrast, the insulin receptor kinase catalyzed the phosphorylation of the calmodulin-dependent kinase and addition of insulin in vitro resulted in a 40% increase in this phosphorylation. In the presence of calmodulin-dependent kinase and the insulin receptor kinase, insulin also stimulated the phosphorylation of calmodulin. Phosphoamino acid analysis showed an increase of phosphotyrosine content in both calmodulin and calmodulin-dependent protein kinase. These data suggest that the insulin receptor kinase may interact directly and specifically with the calmodulin-dependent kinase and calmodulin. Further studies will be required to determine if these phosphorylations modify the action of these regulatory proteins.

No abstract

Despite the importance of structure and properties in organic mixed conductors, there exist very few material systems where the effects of relative crystallinity, crystallite size, and doping concentration could be effectively decoupled, while the resultant organic electrochemical transistors exhibit excellent device performance and stability. The film crystallinity and doping concentration could be independently controlled by adjusting the stoichiometry of the connector versus the pyrrole monomer, leading to the effective modulation of mixed conductivities and electrochemical characteristics as confirmed by electrochemical impedance analysis, organic electrochemical transistor characterization, and moving front measurement. The comprehensive structural and functional analyses suggest that there exist two distinct domains: the low crystallinity domain where carrier concentration is well controlled and the high film crystallinity domain where ion mobility is finely tuned. We believe that our study can provide general insights into the structure and properties of polymeric mixed conductors as well as the design principles governing their applications to biochemical sensing, bioelectric recording, and stimulation devices with customized properties.

No abstract

The pedestal of the rechargeable zinc–air battery (ZAB) is based on high‐performance bifunctional oxygen reduction/evolution reactions (ORR/OER) electrocatalysts. Herein, without any template or surfactant, in situ grown nitrogen‐doped carbon‐nanotube (NCNT)‐embedded with two phases of bimetal CoFe alloys and CoFe2O4 spinel oxide are constructed, using inexpensive materials of glucose, urea, and cobalt/iron acetates by programing the pyrolysis temperature. The obtained catalyst with optimal cobalt/iron acetates mass ratio (1:1) denoted as CoFe–CoFe2O4–NCNT not only exceeds Pt–Ru/C in terms of ORR half‐wave potentials [(0.88 vs 0.84 V versus reversible hydrogen electrode (RHE)] and limiting current densities (6.40 vs 5.40 mA cm−2), but also manifests superior OER activity with the potentials of (1.58 vs 1.67 V versus RHE) at 10 mA cm−2. Therefore, CoFe–CoFe2O4–NCNT exhibits a smaller ΔE value of (0.70 V versus RHE), surpassing that of Pt–Ru/C (0.85 V versus RHE) and shows excellent stability as well as outstanding methanol tolerance compared with the Pt–Ru/C commercial catalyst. In addition, CoFe–CoFe2O4–NCNT applied as a bifunctional air electrode in rechargeable ZAB displays a promising rechargeability performance with high‐discharge and low‐charge potentials and a relatively stable potential gap under 550 cycles, outperforming those of Pt–Ru/C.

The close-packed crystal nanostructure and electrochemical properties of the composite P(Py:BPDSA:Py)-GO are analyzed.