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Additional file 1: Supplementary Fig. 1. Original files of SDS-PAGE and Western blots of purified recombinant proteins. SDS-PAGE and Western blot analysis were performed to verify recombinant protein production and identity.

Stereocomplex formation based on chiral recognition was examined in racemic mixtures (PnG) of α-helical poly(γ-alkyl l -glutamate) (PnLG) and poly(γ-alkyl d -glutamate) (PnDG), where n, the carbon number of the side-chain alkyl groups, was varied from 1 to 6. When enantiomorphic solutions of PnG with relatively short side chains of n = 1–3 were mixed in DMF, precipitation occurred as fine fibrils with an equimolar content of PnLG and PnDG, demonstrating the formation of a stereocomplex of l and d molecules. The precipitates included 10–12 vol% of DMF solvent and possessed tetragonal packing structure of α-helices. The tetragonal packing symmetry, which is unusual in the α-helical polypeptide system, was considered to be produced by “knobs-into-holes” packing of side chains between l and d helices regularly arrayed in a lattice.

合成一种分子量分布窄、两嵌段侧链不同的新型聚(-苄基-L-谷氨酸)和聚(-十二烷基-L-谷氨酸)的二嵌段聚肽(poly(-benzyl-L-glutamate)-b-poly(-dodecyl-L-glutamate), PBLG-b-PDLG),并研究该嵌段聚肽的分子结构、热性能及液晶性.PBLG-b-PDLG的合成是利用N-羧酸内酸酐(N-carbonyl anhydride, NCA)法,以正己胺为引发剂,在0℃的条件下的氯仿溶液中,先将-苄基-L-谷氨酸NCA开环聚合获得了末端带胺基的活性PBLG-NH2沉淀后,再以其为引发剂加入-十二烷基-L-谷氨酸的NCA继续反应.氢核磁共振波谱(1H-NMR)和凝胶渗透色谱(GPC)用于表征两嵌段的摩尔比、分子量及其分布,发现嵌段聚肽的分子量分布只有1.07~1.09.由红外光谱(IR)的分析得知PBLG-b-PDLG的二次结构为刚直棒状的-螺旋结构.利用示差扫描量热分析法(DSC)考察材料的热性质,发现不同组成的PBLG-b-PDLG有不同的热行为,而在100℃附近都出现了微弱的热致相转变.采用偏光显微镜观察PBLG-b-PDLG磁场取向膜的相变行为中发现其相结构不同于一般无规共聚物所呈现的胆甾液晶结构,同时用在PBLG-b-PDLG的二氯乙烷溶致液晶溶液中观察到一般近晶相所呈现的扇形织构.

We studied the helix–helix transition of poly( β -phenylpropyl l -aspartate) (3PLA) embedded in a right-handed α -helical ( α R ) poly( γ -phenylethyl l -glutamate) (2PLG) or left-handed α -helical poly( γ -phenylethyl d -glutamate) (2PDG) matrix. Binary mixtures were prepared with 3PLA:2PLG (2PDG) mole fractions of 9:1 to 1:9. In all these mixtures, the 3PLA molecule exhibited helical sense inversion even if dispersed or isolated into the hard-rod matrix, and the inversion rate of the embedded 3PLA molecule was relatively higher than that of the pure system. Thus, it was concluded that the transition occurs in only a limited space and more easily for the isolated molecule. Further, the 3PLA molecule recognized the chiral environment produced by the surrounding polymers. For 3PLA surrounded by a 2PDG matrix, the helix–helix transition temperature was lower and the transition rate on cooling was slower than those for 3PLA surrounded by a 2PLG matrix. This is reasonable since the left-handed matrix helps right-handed to left-handed helical inversion.

Steady shear flow viscosities was measured for nematic liquid crystals (LCs) in the aromatic copolyesters composed of 4-hydroxybenzoic acid (HBA), 6-hydroxy-2-naphthoic acid (HNA), telephthalic acid, and biphenol whose molar contents are 0.73 − x, 0.27 − x, x, and x, respectively. Second harmonic generation (SHG) measurements showed that a SHG-active polar nematic LC formed by poly(HBA/HNA) with x = 0 is altered to a conventional nonpolar nematic LC with an increase in x more than 0.07. The shear-rate dependence of melt viscosity measured for nematic LCs of all the copolymers showed four characteristic regions; a Newtonian plateau in lowest shear-rate region 0 in addition to the well-known three regions, low-shear-rate shear-thinning region I, intermediate Newtonian plateau region II and high-shear-rate shear-thinning region III. The SHG-activity in nematic LCs reflected on the Newtonian plateau region 0. The viscosity of the SHG-active nematic LCs in this region 0 was 10 times higher than that of the non...

The temperature-concentration phase diagram was constructed for lyotropic solutions of poly(γ-phenylpropyl L-glutamate) in m-cresol in the temperature range from 0 to 70 °C and in the concentration range from 0 to 100 vol %. Visual and microscopic observations and the X-ray measurement were employed to determine the phase structures and phase boundaries. The well-known transition from the isotropic phase to the cholesteric phase is observed in the low concentration range of 8 to 14 vol %, as predicted using the Flory lattice theory and reported from experiments. At higher concentrations, however, a novel phase behavior is observed. The cholesteric phase is transformed to the hexagonal columnar phase through the coexistence region. The critical concentration of the columnar phase appearing from the cholesteric one is 49 vol %. The removal of solvents from this columnar solution leads to the solid state structure with the hexagonal packing symmetry. Thus, the phase diagram was well clarified, and found to include three phases: isotropic, cholesteric, and columnar phases. According to this phase diagram, at high temperatures, the isotropic-cholesteric-columnar phase transition takes place upon increasing the concentration, whereas at low temperatures, the isotropic solution directly transforms to the columnar phase. Similar phase diagrams are presumed for other poly(γ-alky L-glutamates) and poly(γ-phenylalky L-glutamates), although the critical concentration of the columnar phase will increase with an increase in side-chain length.

Second harmonic generation (SHG) measurements were performed on the nematic liq. crystal formed from polar arom. polyester which comprises 4-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid in a molar ratio of 73/27. The polymer is com. available and called Vectra. The shear-oriented nematic liq. crystal of Vectra shows strong SHG mostly along the n-director. Since no elec. poling is made, the obsd. SHG activity indicates that the polar ordering is spontaneously formed in the nematic liq. crystal. From detailed analyses of the SHG intensity profiles measured with combinations of polarizer and analyzer directions to the n-director, the nematic liq. crystal is found to possess the Cs packing symmetry; in other words, it is not uniaxial but biaxial, and the polarization arises in the symmetry plane. To search the origin of the spontaneous polarization, a series of Vectra polymers were prepd. with various d.p. (DP) and two chem. modified Vectras. Of interest is that the DP of polymer significantly affects the polar structure. When DP is decreased, the SHG activity in the nematic liq. crystal disappears completely. Since the dipole moment increases with DP, the huge dipole moment of polymer is considered to be responsible for the polar ordering. In one of the two chem. modified Vectras, terephthalic acid (TA) and biphenol (BP) in an equimolar content are introduced. As expected from the dissipation of head-tail character in constituent polymer, the nematic liq. crystals lose completely the SHG activity only with an incorporation of 5 mol % of TA and BP. In another modified Vectra including 3-hydroxybenzoic acid (m-HBA), the head-tail character is not lost, but their liq. crystallinity is destabilized because of kink conformation induced by the m-HBA unit. In this system, the SHG is invariably obsd. for the nematic liq. crystals, but as one of the significant effects, polar biaxial nematic liq. crystal of Vectra is altered to the polar uniaxial one by the introduction of m-HBA above 5 mol %.

Second-harmonic generation (SHG) properties of α-helical and ω-helical polypeptides have been investigated by using crystalline films prepared by casting lyotropic liquid crystal solutions of poly(γ-phenylpropyl L-glutamate) (3PLG) and poly(β-benzyl L-aspartate) (PBLA) under a high electric field. The crystalline films generated SH light upon irradiation of the Nd:YAG laser, which ensures that the films have a polar structure. The in-plane anisotropy of the polarized SH light intensity is well explained by theoretical descriptions under the C6 and C4 symmetries for 3PLG and PBLA, respectively. On the basis of the SHG results, the hyperpolarizability tensor components of the individual polypeptide helical molecules are characterized as βZXX/βZZZ=1.2, βXZX/βZZZ=3.8, and 2βZXX/βXZX=0.7 for the α-helix 3PLG, and βZXX/βZZZ=3.8, βXZX/βZZZ=5.0, and 2βZXX/βXZX=1.5 for the ω-helix PBLA, where the z-axis is set as the helical axis. Quantum chemical calculation is successfully performed to reveal the general character of the polypeptide helix, βZXX>βZZZ.

We present an interesting phenomenon of the mechanically aligned monodomain state of polar nematic liquid crystals transforming into the polydomain one. This unusual transformation may result from mismatching of the dipolar vectors. By stretching or shear-flowing the polar nematic liquid crystal, the perfect orientation can be achieved with respect to the long molecular axis, but the misorientation exists with respect to the polar vector. After the prolonged annealing, then, the free energy of the molecules is minimized by producing new defects which satisfy the continuity of polar orientation, but lead to the loss of macroscopic molecular orientation.