Cytoskeletal Signaling: Is Memory Encoded in Microtubule Lattices by CaMKII Phosphorylation?

Memory is attributed to strengthened synaptic connections among particular brain neurons, yet synaptic membrane components are transient, whereas memories can endure. This suggests synaptic information is encoded and ‘hard-wired’ elsewhere, e.g. at molecular levels within the post-synaptic neuron. In long-term potentiation (LTP), a cellular and molecular model for memory, post-synaptic calcium ion (Ca2+) flux activates the hexagonal Ca2+-calmodulin dependent kinase II (CaMKII), a dodacameric holoenzyme containing 2 hexagonal sets of 6 kinase domains. Each kinase domain can either phosphorylate substrate proteins, or not (i.e. encoding one bit). Thus each set of extended CaMKII kinases can potentially encode synaptic Ca2+ information via phosphorylation as ordered arrays of binary ‘bits’. Candidate sites for CaMKII phosphorylation-encoded molecular memory include microtubules (MTs), cylindrical organelles whose surfaces represent a regular lattice with a pattern of hexagonal polymers of the protein tubulin. Using molecular mechanics modeling and electrostatic profiling, we find that spatial dimensions and geometry of the extended CaMKII kinase domains precisely match those of MT hexagonal lattices. This suggests sets of six CaMKII kinase domains phosphorylate hexagonal MT lattice neighborhoods collectively, e.g. conveying synaptic information as ordered arrays of six “bits”, and thus “bytes”, with 64 to 5,281 possible bit states per CaMKII-MT byte. Signaling and encoding in MTs and other cytoskeletal structures offer rapid, robust solid-state information processing which may reflect a general code for MT-based memory and information processing within neurons and other eukaryotic cells

An exafs and volumetric study of the formation of hydrides on Pd particles encaged in Y-zeolite

EXAFS performed on 10 Å particles of Pd in the network of a Y-zeolite has shown that in vacuum the structure of the metal is similar to that of the bulk.The lattice expansion observed on the EXAFS data when 500 mbar H2 is introduced, is slightly smaller than what is observed on the bulk upon the formation of the β-hydride.It is inferred that on small clusters, where the number of sites is reduced, the stoichiometry of the hydride is reduced to 0.4 H/Pd instead of 0.6

Selective Growth Of Decagonal Ai-Co Thin Films By Reactive Diffusion: Kinetic And Thermodynamic Aspects

AbstractWe report on the formation by reactive diffusion of a pure decagonal quasicrystalline film in Al/Co bilayer and multilayer structures of overall composition Al13CO4. We show that this method is highly selective since several stable phases which exist around this composition are never observed. The quasicrystal is not the first reaction product but is obtained as a second reaction step by a peritectoid reaction between Al9Co2 and the remaining cobalt. DSC analysis allows the determination of both the enthalpy of formation of the decagonal quasicrystal (ΔHf = -31500 ± 2000 J/g-atom) and its activation energy of growth (2.6 ± 0.5 eV).</jats:p

First stages in the formation of ultra thin nickel layers on Cu(111) and Ge(111) and dissolution: an AES comparative study

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