Figure 13. Structures of poly(dialkylsilane)s with different main-chain stiffness (74s76) and schematic illustrations of stiffness-dependent polymer wrapping behavior onto SWNT by the high-speed vibration milling (HSVM) method. (Reproduced with permission from ref 133.

Sequence control in chain-growth polymerization is still one of the most challenging topics in synthetic polymer chemistry in contrast to natural macromolecules with completely sequence-regulated structures like proteins and DNA. Here, we report the quantitative and highly selective 1:2 sequence-regulated radical copolymerization of naturally occurring (+)-d-limonene (L) and a maleimide (M) in fluoroalcohol giving chiral copolymers with high glass transition temperatures (220-250 degrees C) originating from the specific rigid cyclic structures of the monomers. Furthermore, the combination with a reversible addition-fragmentation chain transfer (RAFT) agent (C-S) via the controlled/living radical polymerization resulted in end-to-end sequence-regulated copolymers [C-(M-M-L)(n)-M-S] with both highly sequenced chain ends and main-chain repeating units as well as controlled molecular weights.

Disrupted-In-Schizophrenia 1 (DISC1) is a candidate gene for susceptibility to schizophrenia. DISC1 is reported to interact with NudE-like (NUDEL), which forms a complex with lissencephaly-1 (LIS1) and 14-3-3. 14-3-3 is involved in the proper localization of NUDEL and LIS1 in axons. Although the functional significance of this complex in neuronal development has been reported, the transport mechanism of the complex into axons and their functions in axon formation remain essentially unknown. Here we report that Kinesin-1, a motor protein of anterograde axonal transport, was identified as a novel DISC1-interacting molecule. DISC1 directly interacted with kinesin heavy chain of Kinesin-1. Kinesin-1 interacted with the NUDEL/LIS1/14-3-3 complex through DISC1, and these molecules localized mainly at cell bodies and partially in the distal part of the axons. DISC1 partially colocalized with Kinesin family member 5A, NUDEL, LIS1, and 14-3-3 in the growth cones. The knockdown of DISC1 by RNA interference or the dominant-negative form of DISC1 inhibited the accumulation of NUDEL, LIS1, and 14-3-3 at the axons and axon elongation. The knockdown or the dominant-negative form of Kinesin-1 inhibited the accumulation of DISC1 at the axons and axon elongation. Furthermore, the knockdown of NUDEL or LIS1 inhibited axon elongation. Together, these results indicate that DISC1 regulates the localization of NUDEL/LIS1/14-3-3 complex into the axons as a cargo receptor for axon elongation.

Proteins and nucleic acids are sequence-regulated macromolecules with various properties originating from their perfectly sequenced primary structures. However, the sequence regulation of synthetic polymers, particularly vinyl polymers, has not been achieved and is one of the ultimate goals in polymer chemistry. In this study, we report a strategy to obtain sequenceregulated vinyl copolymers consisting of styrene, acrylate and vinyl chloride units using metalcatalysed step-growth radical polyaddition of designed monomers prepared from common vinyl monomer building blocks. Unprecedented ABCC-sequence-regulated copolymers with perfect vinyl chloride -styrene -acrylate -acrylate sequences were obtained by copper-catalysed step-growth radical polymerization of designed monomers possessing unconjugated C = C and reactive C -Cl bonds. This strategy may open a new route in the study of sequence-regulated synthetic polymers.

Rigid-rodlike right (P)- and left (M)-handed helical polyisocyanides (P-poly-L-1 and M-poly-L-1) prepared by the living polymerization of an enantiomerically pure phenyl isocyanide bearing an L-alanine pendant with a long n-decyl chain (L-1) with the mu-ethynediyl Pt-Pd catalyst were found to block copolymerize L-1 and D-1 in a highly enantiomer-selective manner while maintaining narrow molecular weight distributions. The M-poly-L-1 preferentially copolymerized L-1 over the antipode D-1 by a factor of 6.4-7.7, whereas the D-1 was preferentially copolymerized with P-poly-L-1 composed of the same L-1 units, but possessing the opposite helicity by a factor of 4.0. Circular dichroism and high-resolution atomic force microscopy revealed that the enantiomer-selective block copolymerizations proceed in an extremely high helix-sense-selective fashion, and the preformed helical handedness determines the overall helical sense of the polyisocyanides irrespective of the configuration of the monomer units of the initiators during the block copolymerizations. The block copolymers are rigid-rod helical polymers with a narrow molecular weight distribution and exhibit a lyotropic smectic liquid crystalline phase.

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.

Optically active, amphiphilic poly(meta-phenylene ethynylene)s (PPEa) bearing L- or D-alanine-derived oligo(ethylene glycol) side chains connected to the backbone via amide linkages were prepared by microwave-assisted polycondensation. PPEa's exhibited an intense Cotton effect in the π-conjugated main-chain chromophore regions in various polar and nonpolar organic solvents due to a predominantly one-handed helical conformation stabilized by an intramolecular hydrogen-bonding network between the amide groups of the pendants. The stable helical structure was retained in the bulk and led to supramolecular column formation from stacked helices in oriented polymer films as evidenced by X-ray diffraction. Atomic force microscopy was used to directly visualize the helical structures of the polymers in two-dimensional crystalline layers with molecular resolution, and, for the first time, their absolute helical senses could unambiguously be determined.

We report a unique hierarchical amplification of chiral information from a nonracemic guest to macromolecular helicity, followed by a mesoscopic, supramolecular cholesteric twist in water. This remarkable chiral amplification involves two-step chirality transfer processes, which enable the detection and sensing of an extremely small imbalance in chiral guest molecules. The macromolecular helicity with an excess single-handed helix was first induced in the positively charged, chromophoric poly(phenylacetylene), the hydrochloride of poly-(4-(N,N-diisopropylaminomethyl)phenylacetylene) (poly-1-HCl) upon complexation with an oppositely charged nonracemic acid as a dopant through electrostatic interaction in dilute water. Subsequently, the macromolecular helicity was further amplified in the polymer backbone as a greater excess of a single-handed helix through self-assembly into a lyotropic cholesteric liquid crystal (LC). Direct evidence for the hierarchical amplification process of the helical sense excess of the polymer during the cholesteric LC formation was demonstrated by direct comparison of the excess of the one helical sense of the polymer in dilute solution with that in the cholesteric LC state. Poly-1-HCl formed a lyotropic nematic LC in water in the absence of chiral acids, indicating its rigidrod characteristic regardless of the lack of a single-handed helix, as evidenced by the long persistence lengths before (26 nm) and after (28 nm) the one-handed helicity induction in the polymer. X-ray diffraction of the oriented films of the nematic and cholesteric liquid crystalline poly-1-HCls exhibited almost the same diffraction pattern, suggesting that both polymers may have the same helical structure despite the substantial difference in their helical characteristics, dynamically racemic and one-handed helices in dilute solution, respectively. On the basis of the X-ray analyses, the most plausible helical structure of poly-1-HCl is proposed to be a 23 unit/10 turn (23/10) helix.