Large-scale production of phospholipase D from Streptomyces racemochromogenes and its application to soybean lecithin modification.

Phospholipase D (PLD) catalyzes transphosphatidylation, causing inter-conversion of the polar head group of phospholipids and phospholipid hydrolysis. Previously, we cloned PLD103, a PLD with high transphosphatidylation activity, from Streptomyces racemochromogenes strain 10-3. Here, we report the construction of an expression system for the PLD103 gene using Streptomyces lividans as the host bacterium to achieve large-scale production.

Self-organizing surface-initiated polymerization: facile access to complex functional systems.

Facile access to complex systems is crucial to generate the functional materials of the future. Herein, we report self-organizing surface-initiated polymerization (SOSIP) as a user-friendly method to create ordered as well as oriented functional systems on transparent oxide surfaces. In SOSIP, self-organization of monomers and ring-opening disulfide exchange polymerization are combined to ensure the controlled growth of the polymer from the surface.

Latticelike smectic liquid crystal phase in a rigid-rod helical polyisocyanide with mesogenic pendants.

We report a unique macromolecule consisting of a rodlike helical polyisocyanide backbone with a narrow molecular weight distribution and rigid mesogenic chiral pendants linked via a flexible spacer that exhibits lyotropic nematic and latticelike new smectic (lat-Sm) liquid crystal phases at different concentrations. The unprecedented lat-Sm phase is associated with the smectic ordering of both the stiff polymer backbone and the rigid-rod side groups. A detailed investigation of the films using X-ray scattering and atomic force microscopy revealed a novel tilted smectic layer structure of the polymer backbone aligned perpendicular to the smectic layer of the mesogenic pendants, which arrange in an antiparallel overlapping interdigitated manner.

Hierarchical amplification of macromolecular helicity of dynamic helical poly(phenylacetylene)s composed of chiral and achiral phenylacetylenes in dilute solution, liquid crystal, and two-dimensional crystal.

Optically active poly(phenylacetylene) copolymers consisting of optically active and achiral phenylacetylenes bearing L-alanine decyl esters (1L) and 2-aminoisobutylic acid decyl esters (Aib) as the pendant groups (poly(1L(m)-co-Aib(n))) with various compositions were synthesized by the copolymerization of the optically active 1L with achiral Aib using a rhodium catalyst, and their chiral amplification of the macromolecular helicity in a dilute solution, a lyotropic liquid crystalline (LC) state, and a two-dimensional (2D) crystal on the substrate was investigated by measuring the circular dichroism of the copolymers, mesoscopic cholesteric twist in the LC state (cholesteric helical pitch), and high-resolution atomic force microscopy (AFM) images of the self-assembled 2D helix-bundles of the copolymer chains. We found that the macromolecular helicity of poly(1L(m)-co-Aib(n))s could be hierarchically amplified in the order of the dilute solution, LC state, and 2D crystal. In sharp contrast, almost no chiral amplification of the macromolecular helicity was observed for the homopolymer mixtures of 1L and Aib in the LC state and 2D crystal on graphite.

Visualization of synthetic helical polymers by high-resolution atomic force microscopy.

Direct observations of the helical structures of artificial helical polymers, such as helical polyacetylenes and polyisocyanides, by atomic force microscopy (AFM) are described in this tutorial review. The two-dimensional helix bundle formation of specific helical polymers on substrates under solvent vapor exposure permits us to determine their helical structures, including their helical pitch and handedness, at a molecular level by AFM in the tapping mode. The direct observation of supramolecular helical structures based on stereoregular poly(methyl methacrylate)s is also described.

Double-stranded helical polymers consisting of complementary homopolymers.

Two complementary homopolymers of chiral amidines and achiral carboxylic acids with m-terphenyl-based backbones were synthesized by the copolymerization of a p-diiodobenzene derivative with the diethynyl monomers bearing a chiral amidine group and a carboxyl group using the Sonogashira reaction, respectively. Upon mixing in THF, the homopolymer strands assembled into a preferred-handed double helix through interstrand amidinium-carboxylate salt bridges, as evidenced by its absorption, circular dichroism, and IR spectra. In contrast, when mixed in less polar solvents, such as chloroform, the complementary strands kinetically formed an interpolymer complex with an imperfect double helical structure containing a randomly hybridized cross-linked structure, probably because of strong salt bridge formations.

Two- and three-dimensional smectic ordering of single-handed helical polymers.

Rodlike polymers with precisely defined architectures are ideal building blocks for self-assembled structures leading to novel nanometer-scale devices. We found that the living polymerization of a single isocyanide enantiomer bearing an l-alanine pendant with a long n-decyl chain simultaneously produced diastereomeric right- and left-handed helices with different molecular weights and narrow molecular weight distributions. Each single-handed, rodlike helical polymer with a controlled length and handedness isolated by a facile solvent fractionation method with acetone self-assembled to form well-defined two- and three-dimensional smectic ordering on the nanometer scale on a substrate and in a liquid crystalline state as evidenced by direct atomic force microscopic observations and X-ray diffraction measurements, respectively.

Two-dimensional surface chirality control by solvent-induced helicity inversion of a helical polyacetylene on graphite.

We report the direct evidence for the macromolecular helicity inversion of a helical poly(phenylacetylene) bearing l- or d-alanine pendants with a long alkyl chain in different solvents by atomic force microscopy observations of the diastereomeric helical structures. The diastereomeric helical poly(phenylacetylene)s induced in polar and nonpolar solvents self-assembled into ordered, two-dimensional helix bundles with controlled molecular packing, helical pitch, and handedness on graphite upon exposure of each solvent. The macromolecular helicity deposited on graphite from a polar solvent further inverted to the opposite handedness by exposure to a specific nonpolar solvent, and these changes in the surface chirality based on the inversion of helicity could be visualized by atomic force microscopy with molecular resolution, and the results were quantified by X-ray diffraction of the oriented liquid crystalline, diastereomeric helical polymer films.

Helix-sense controlled polymerization of a single phenyl isocyanide enantiomer leading to diastereomeric helical polyisocyanides with opposite helix-sense and cholesteric liquid crystals with opposite twist-sense.

We report the unprecedented helix-sense controlled polymerization of enantiomerically pure phenyl isocyanides bearing an l- or d-alanine pendant with a long alkyl chain. The polymerization with an achiral nickel catalyst diastereoselectively proceeds, resulting in either a right- or left-handed helical polymer, whose helix-sense can be controlled by the polymerization solvent and temperature. Both the diastereomeric right- and left-handed helical polymers further self-assemble into lyotropic cholesteric liquid crystals with opposite twist-senses.

Inhibition of D-serine accumulation in the Xenopus oocyte by expression of the rat ortholog of human 3'-phosphoadenosine 5'-phosphosulfate transporter gene isolated from the neocortex as D-serine modulator-1.

D-serine in mammalian brains has been suggested to be an endogenous co-agonist of the NMDA-type glutamate receptor. We have explored the molecules regulating D-serine uptake and release from the rat neocortex cDNA library using a Xenopus oocyte expression system, and isolated a cDNA clone designated as dsm-1 (D-serine modulator-1) encoding a protein that reduces the accumulation of D-serine to the oocyte. dsm-1 is the rat orthologue of the human 3'-phosphoadenosine 5'-phosphosulfate transporter 1 (PAPST1) gene.

Cloning of a D-serine-regulated transcript dsr-2 from rat cerebral neocortex.

D-serine is now considered to be an endogenous co-agonist of the NMDA receptor in mammalian brain. To obtain insight into the molecular mechanisms underlying D-serine metabolism and function, we explored transcripts that are responsive to D-serine in the neocortex of the 8-day-old infant rat by a differential cloning technique, RNA arbitrarily primed PCR. We isolated a novel D-serine inducible transcript, D-serine-responsive transcript-2 (dsr-2), that was exclusively expressed in the brain.

Effects of psychotomimetic and antipsychotic agents on neocortical and striatal concentrations of various amino acids in the rat.

A subcutaneous injection of small and moderate doses (1.6, 3.2, 4.