Inositol trisphosphate is a second messenger that controls many cellular processes by generating internal calcium signals. It operates through receptors whose molecular and physiological properties closely resemble the calcium-mobilizing ryanodine receptors of muscle. This family of intracellular calcium channels displays the regenerative process of calcium-induced calcium release responsible for the complex spatiotemporal patterns of calcium waves and oscillations. Such a dynamic signalling pathway controls many cellular processes, including fertilization, cell growth, transformation, secretion, smooth muscle contraction, sensory perception and neuronal signalling.

Inositol trisphosphate and calcium signalling

The universality of calcium as an intracellular messenger depends on its enormous versatility. Cells have a calcium signalling toolkit with many components that can be mixed and matched to create a wide range of spatial and temporal signals. This versatility is exploited to control processes as diverse as fertilization, proliferation, development, learning and memory, contraction and secretion, and must be accomplished within the context of calcium being highly toxic. Exceeding its normal spatial and temporal boundaries can result in cell death through both necrosis and apoptosis.

The versatility and universality of calcium signalling

The development in the field of coordination polymers or metal-organic coordination networks, MOCNs (metal-organic frameworks, MOFs) is assessed in terms of property investigations in the areas of catalysis, chirality, conductivity, luminescence, magnetism, spin-transition (spin-crossover), non-linear optics (NLO) and porosity or zeolitic behavior upon which potential applications could be based.

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Engineering coordination polymers towards applications

A review was presented to demonstrate a historical description of the synthesis of light-emitting conjugated polymers for applications in electroluminescent devices. Electroluminescence (EL) was first reported in poly(para-phenylene vinylene) (PPV) in 1990 and researchers continued to make significant efforts to develop conjugated materials as the active units in light-emitting devices (LED) to be used in display applications. Conjugated oligomers were used as luminescent materials and as models for conjugated polymers in the review. Oligomers were used to demonstrate a structure and property relationship to determine a key polymer property or to demonstrate a technique that was to be applied to polymers. The review focused on demonstrating the way polymer structures were made and the way their properties were controlled by intelligent and rational and synthetic design.

Synthesis of Light-Emitting Conjugated Polymers for Applications in Electroluminescent Devices

Graphenes as potential material for electronics.

Spatiotemporal characterization of intracellular Ca2+ rise during the acrosome reaction of mammalian spermatozoa induced by zona pellucida.

Raman and infrared spectra have been studied on variously hydrogenated trans‐polyacetylenes which are prepared by exposing Na‐doped trans‐polyacetylene films to ethanol. Raman spectra have been analyzed by reference to the relations between the number of trans‐conjugated double bonds (NC=C) and the ν1 and ν3 frequencies. NC=C’s of increased short segments are correlated with the distribution of dopants. Information on (CH2)k groups and very short (CH=CH)n groups including isolated (CH=CH) is obtained from infrared spectra and hydrogenation processes are proposed. Upon iodine doping the hydrogenated films exhibit three infrared bands which are similar to the well‐known three‐band pattern of doped polyacetylene, while they give poor electrical conductivities at the maximum iodine doping. Hence, the three bands of doped polyacetylene do not straightforwardly correlate with the overall conductivity. The infrared results strongly indicate that a relatively short conjugated segment with methylene groups at both...

Vibrational spectroscopic study on partly hydrogenated trans‐polyacetylenes

Polyacetylene films prepared by the liquid crystal polymerization method with gravity flow technique are investigated through measurements of scanning electron micrographs, polarized infrared absorption spectra, and electrical conductivities. It is explored that the films have significant orientation of conjugated polyene chains along fibril alignment, and that upon doping by I2 or AsF5 they exhibit the highest electrical conductivity among those reported so far. By taking account of both morphological structure and activation energy for electrical conduction, the high conductivity is rationalized with preferential increase of parallel fraction of fibril achieved in the highly oriented polyacetylene films.

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Highly Conducting Polyacetylene Films Prepared in a Liquid Crystal Solvent

We have synthesized novel liquid crystalline conducting polymers by introducing liquid crystalline group into acetylene monomer and polymerizing them with Ziegler-Natta [Fe(acac)3 - AlEt3] and metathesis [M0Cl5 - Ph4Sn] catalysts. The liquid crystalline group is composed of a phenylcyclohexyl (PCH) or biphenyl (BP) moiety as a mesogenic core, a trimethylene chain [-(CH2)3-] as a spacer, and an alkyl chain (-CnH2n+1, n = 2, 3, 5 ∼ 8) as a terminal group. The polymers are abbreviated as PPCHn03A and PBPn03A.



All polymers prepared exhibited solubility in organic solvents and smectic liquid crystallinity characterized with fan-shaped texture in polarizing optical microscopy. Phase transitions and the corresponding enthalpy changes were also evaluated by means of differential scanning calorimetry (DSC). Macroscopic alignments of the polymers were performed in the liquid crystalline phase by shear-stress or magnetic force field of 0.7 − 1.0 tesla, which resulted in an enhancement by two orders in electrical conductivity of iodine-doped cast films. Changes of the electronic and geometrical structures of the polymer upon the iodine-doping were elucidated by examining the effective conjugation length of a polyene chain, cis and trans thermal isomerization, and spin distribution of unpaired electrons through ultraviolet / visible (UV-Vis) and electron spin resonance (ESR) measurements.

Morphological alignment of liquid crystalline conducting polyacetylene derivatives

Highly aligned polyacetylene films are synthesized by three different methods in which nematic liquid crystals are used as an ordered matrix solvent: Method 1, polymerization of acetylene is carried out in a quiescent nematic solution in which a Ti(OBu)4-AlEt3 Ziegler-Natta catalyst is dissolved homogeneously; Method 2, macroscopic alignment is attained by gravity flow of the nematic liquid crystal-catalyst system; and Method 3, the nematic liquid crystal-catalyst solution is aligned under a magnetic field. Characterization of these films is carried out through SEM observation and measurements of polarized visible and infrared absorption spectra. Results indicate that as-prepared films have highly aligned fibrils. Upon doping by I2 and AsF5, these films exhibit high electrical condactivity of the order of 104 S/cm.

Hideki Shirakawa

Papers

Spatiotemporal characterization of intracellular Ca2+ rise during the acrosome reaction of mammalian spermatozoa induced by zona pellucida.

Vibrational spectroscopic study on partly hydrogenated trans‐polyacetylenes

Highly Conducting Polyacetylene Films Prepared in a Liquid Crystal Solvent

Morphological alignment of liquid crystalline conducting polyacetylene derivatives

Synthesis, Characterization, and Properties of Aligned Polyacetylene Films