Reconstruction of volume structure of carbon-based conductive polymer composites

Conductive polymer composites with different carbon fillers are under intensive investigation nowadays due to their unique properties and possible applications in different areas of science and technology. The percolation character of the conductivity behaviour in these materials and influence of nanoscale structure of conductive filler on macroscopic characteristics of composites make it important to determine the 3D structure of the components. Various electrical methods of atomic force microscopy (AFM) are efficient tools for visualization of a conductive network on a sample surface. In this work, we use a combination of AFM methods and ultramicrotomy for the 3D reconstruction of the filler structure in graphene-polystyrene and carbon black-epoxy-amine composites. Common features of the various composites, such as the formation of clusters with similar conductivity and limited number of filler particles forming a conductive network, are discussed

Two structurally distinct and spatially compartmentalized adenylate kinases are expressed from the AK1 gene in mouse brain.

Contains fulltext : 59150.pdf (publisher's version ) (Closed access)Adenylate kinases (AK, EC 2.7.4.3) have been considered important enzymes for energy homeostasis and metabolic signaling. To gain a better understanding of their cell-specific significance we studied the structural and functional aspects of products of one adenylate kinase gene, AK1, in mouse tissues. By combined computer database comparison and Northern analysis of mRNAs, we identified transcripts of 0.7 and 2.0 kilobases with different 5' and 3' non-coding regions which result from alternative use of promoters and polyadenylation sites. These mRNAs specify two distinct proteins, AK1 and a membrane-bound AK1 isoform (AK1beta), which differ in their N-terminal end and are co-expressed in several tissues with high-energy demand, including the brain. Immunohistochemical analysis of brain tissue and primary neurons and astrocytes in culture demonstrated that AK1 isoforms are expressed predominantly in neurons. AK1beta, when tested in transfected COS-1 and N2a neuroblastoma cells, located at the cellular membrane and was able to catalyze phosphorylation of ADP in vitro. In addition, AK1beta mediated AMP-induced activation of recombinant ATP-sensitive potassium channels in the presence of ATP. Thus, two structurally distinct AK1 isoforms co-exist in the mouse brain within distinct cellular locations. These enzymes may function in promoting energy homeostasis in the compartmentalized cytosol and in translating cellular energetic signals to membrane metabolic sensors

Adenylate kinase phosphotransfer communicates cellular energetic signals to ATP-sensitive potassium channels.

Item does not contain fulltextTransduction of energetic signals into membrane electrical events governs vital cellular functions, ranging from hormone secretion and cytoprotection to appetite control and hair growth. Central to the regulation of such diverse cellular processes are the metabolism sensing ATP-sensitive K+ (K(ATP)) channels. However, the mechanism that communicates metabolic signals and integrates cellular energetics with K(ATP) channel-dependent membrane excitability remains elusive. Here, we identify that the response of K(ATP) channels to metabolic challenge is regulated by adenylate kinase phosphotransfer. Adenylate kinase associates with the K(ATP) channel complex, anchoring cellular phosphotransfer networks and facilitating delivery of mitochondrial signals to the membrane environment. Deletion of the adenylate kinase gene compromised nucleotide exchange at the channel site and impeded communication between mitochondria and K(ATP) channels, rendering cellular metabolic sensing defective. Assigning a signal processing role to adenylate kinase identifies a phosphorelay mechanism essential for efficient coupling of cellular energetics with K(ATP) channels and associated functions