Research articles

The main factors affecting the chirality and stability of PANI(+)-HCSA are moiety present, concentration, stereochemistry, chain length of the amino acids, time period for the doping, hydrogen bonding and so on. The corresponding CD spectra exhibited no measurable optical activity and consistent with complete de-doping of ES to EB. Further, on doping the solution, we have got the precipitate, which showed a remarkable optical activity. The CD spectra shows retention of the optical activity in solid phase obtained after de-doping of the solution.

Multivariate analysis was applied to the ¹³C nuclear magnetic resonance spectra of homopolymers, homopolymer blends and copolymers of methyl methacrylate (MMA) and tert-butyl methacrylate (TBMA). The first (PC1) and second (PC2) principal components reflected chemical composition of the copolymers and fraction of the MMA-TBMA dyad sequence (f_MT), respectively. Dyad and triad sequence distributions of copolymers that were obtained at higher conversions were successfully determined by partial least squares regression with those of copolymers obtained at low conversions as a training set.

The natural rubber (NR) without vulcanization is easily deformed and strained during magic-angle spinning (MAS). The elongated NR during MAS forms molecular orientation. The static ¹³C NMR spectra of elongated NR became anisotropic, although the static ¹³C NMR spectra of NR before MAS show isotropic. Angle-dependent ¹³C NMR spectra of strips cut from the restricted elongation NR were different from those from the maximum elongated NR. The disagreement indicated that ¹³C chemical shift depends on not only the molecular orientation but also the magnetic susceptibility resulting from the alignment of NR chains.

The proton and carbon NMR resonances have been assigned for 3A-amino-3A-deoxy(2AS,3AS)-α-, β- and γ-CyDs (3α, 3β and 3γ). In these CyDs, a glucose residue has been replaced by an altro-pyranose unit with an axial hydroxyl group. Assignments were made with one-dimensional NMR and COSY, TOCSY, ROESY and CHSHF (heteronuclear shift correlation) spectra. Titration by NMR shift changes gave amino-group pK_a values of 7.73 and 8.84 for 3β (left) and 6A-amino-6A-deoxy-β-CyD (6β, right), respectively.

The objective of this study is to establish an immobilization method of PNIPAM on silica beads surface-modified by HBPS, which could be applied to cell cultivation. The PNIPAM-modified silica beads with enough loading of N-isopropylacrylamide (cleaved PNIPAM M_n=14 800 and 23 700) shows controlled cell adhesion and detachment due to lower critical solution temperature behavior of PNIPAM.

TEM photographs of PS (a, b) and PMMA (a′, b′) particles prepared by emulsion polymerization at 240 r.p.m. (a, a′) and 500 (b, b′) r.p.m.

It was observed that the peptides resulted in β-sheet structure when the peptide solutions were mixed in combination of the side-chain charges being neutralized by each other. Additionally, formation speeds of the β-sheet structure were different between systems, AD12 and AK12 or AE12 and AK12. These phenomena were also observed under the higher concentration condition by ¹³C CP/MAS NMR. These results indicate that the mixing of the two kinds of peptide solutions will be a trigger for the peptide self-assembly and will be able to control the formation speed by the combination.

Structure and molecular mobility of nascent iPP powder were investigated by differential scanning calorimetry, transmission electron microscopy and solid-state nuclear magnetic resonance (NMR). Combination of NMR with other analytical method provides the deep insight and concluded that the crystalline size of nascent powder is extremely small and the crystalline phase is easily affected by the surrounded noncrystalline phase.

The influence of primary structure difference in the main chain on the dimensional properties of the cylindrical rod brush has been investigated by static light scattering and SAXS measurements to demonstrate that the backbone stiffness is greatly affected by the chemical nature of the main chain.

In this study, we investigated the molecular structure of the composite material of silk fibroin and polyurethane as coating agent of vascular grafts by using solid-state nuclear magnetic resonance (NMR) techniques. To elucidate the structure and dynamics, ¹³C cross-polarization (CP)/magic angle spinning (MAS) NMR studies including NMR relaxation experiments were performed. These observations showed that there is a partial interacted portion between soft segment of PU and SF, in particular, the domain size of PU:SU=1:1 composite was smaller than that of the other composites. This study gave basic information on development of new silk-like materials for vascular grafts.

The influence of the dispersed silicotungstic acid (STA) on the membrane properties was studied. The proton conductivities of the composite membranes are higher than the parent SPAES membrane. Even though IEC and water uptake of the composite membranes decreased with increase in STA content, the proton conductivities and hydrolytic stabilities were increased. The acidity of the sulfonic acid group increased with the incorporation of STA. As the composite membranes showed negligible STA extraction, most of the STA retained in the polymer and this increases the efficiency of the membrane.

The relaxation behaviors for several commercial ultra-high molecular weight polyethylene reactor powders were compared. On the basis of the morphological analyses, the reactor powder consisted of particles and fibrils between them, the relative amounts of which depended on the powder preparation conditions. The results of differential scanning calorimetry analysis could not distinguish these powder characteristics because of the remarkable reorganization of these reactor powders during heating scans. In contrast, molecular motions detected by solid-state proton nuclear magnetic resonance techniques characterize the structural differences between these powders.

Well-defined multifunctional diblock copolymers with terminal functional groups were synthesized by the combination of cationic ring opening polymerization (CROP) and reversible addition-fragmentation chain transfer radical (RAFT) polymerization. Poly(ɛ-caprolactone) (PCL)-based biodegradable macro-RAFT agent was synthesized by CROP of CL from hydroxylated RAFT agents. Subsequently, thermoresponsive poly(N-isopropylacrylamide) derivative was propagated using the biodegradable macro-RAFT agent. Obtained polymers highly preserved terminal dithiobenzoate groups, which were easily converted to thiol groups by aminolysis. Therefore, biotin-maleimide was able to be reacted with terminal group. The present method was promising for preparing block copolymer-based multi-functional polymeric micelles.

Bacteriorhodopsin (bR) has a retinal with all-trans and 13-cis, 15-syn configurations whose isomeric ratio is close to 1 in the dark and the population of 13-cis, 15-syn configuration can be increased under the pressurized condition. Increase of pressure by fast magic angle spinning (MAS) induced dynamics change at around Ala81 and Ala84 in bR together with retinal isomerization from all-trans to 13-cis configurations. We demonstrated that fast MAS NMR provides a pressure sauce for investigating the structure and dynamics change of biomacromolecules.

The local structure of the acidic-treated model peptides,(E)₈GGLGGQGAG(A)₆GGAGQGGYGG, derived from the consensus sequence of Nephila clavipes fibroin major ampullate spidroin 1 was determined using two-dimensional proton-driven spin-diffusion solid-state NMR under off-magic-angle spinning coupled with ¹³C isotope double labeling of specific residues. We observed a positional dependence on the torsion angles of Ala residues in the β sheet. Torsion angle of the Ala residue at the center of poly-Ala domain concentrates around at (ϕ, ψ) = (−150°, 150°), while that of its periphery is distorted and more distributed.

The present work deals with the chemical conjugation of biodegradable polymer, PLGA, with a natural anti-inflammatory drug, GlcN. PLGA–GlcN conjugate was self-assembled into NPs contained nanostructure with the aid of probe sonication. Self-assembled nanostructure is composed of hydrophobic PLGA at the surface and hydrophilic GlcN at inner core, which helps its enhanced transdermal permeation for GlcN delivery. Shortest lag time with high flux value obtained with transdermal permeation of nanostructures on human cadaver skin confirms its ability as efficient GlcN vehicle for treating inflammatory diseases.

A chemical profiling methodology is described for seaweed biomass based on comprehensive characterization of the water-soluble, water-insoluble and solid-state components. For nuclear magnetic resonance (NMR) measurements of seaweed water-insoluble components, an extraction method was developed by modification and optimization of physical pretreatments and extraction processes. Compositional variations were evaluated by NMR and attenuated total reflectance Fourier transform infrared spectroscopy, and subsequently indicated red, brown and green algae-specific profiles derived from multivariate statistical analysis.

The hydrodynamic screening length ξ in κ-carrageenan solution was estimated by observing the restriction on the diffusion of pullulan probes with different molecular weights. Signal intensity of κ-carrageenan chains without gradient I_kappa(0) decreased and ξ increased below the sol-to-gel transition temperature T_sg. It is considered that κ-carrageenan chains formed helical aggregates, and enlarged the networks of solute κ-carrageenan chains and the aggregates.

A series of AB₂-, ABC-, (AB)₂-, A₂B₂- and ABCD-type miktoarm star copolymer Ru(II) complexes were readily synthesized by stepwise chelating reactions between a Ru(II)(DMSO)₄Cl₂ and polymer-substituted 2-(1H-1,2,3-triazol-4-yl)pyridine or 2,6-bis(1H-1,2,3-triazol-4-yl)pyridine ligands. The polymer-substituted 2-(1H-1,2,3-triazol-4-yl)pyridine and 2,6-bis(1H-1,2,3-triazol-4-yl)pyridine ligands were conveniently prepared by the click reaction of ethynylpyridines with well-defined azido-terminated polymers, which were prepared by a combination of living/controlled polymerization procedures and end-substitution reactions.

Isotactic and syndiotactic poly(lactic acid) dimer model compounds were synthesized, and studied by ¹H and ¹³C NMR in three solvents, CDCl₃/CCl₄ (20/80 v/v), CDCl₃ and DMSO-d₆. All the peaks in the ¹H and ¹³C NMR spectra were assigned with the help of two-dimensional NMR. The tacticity splitting of the dimers showed no significant difference among the solvents. The chemical shifts were calculated and compared with the experimental shifts to understand the origin of the tacticity splitting in PLA. The observed tacticity splitting of the chemical shifts between isotactic and syndiotactic ¹H and ¹³C NMR peaks were reproduced particularly well using the combination of Becke’s three parameter hybrid method for conformational energy calculation and Hartree-Fock for chemical shift calculation.