Takahiko Nakaoki

Relaxation mechanism in several kinds of polyethylene estimated by dynamic mechanical measurements, positron annihilation, X-ray and 13C solid-state NMR

Abstract Relaxation processes of several kinds of polyethylene films and fibers with different molecular orientational degrees and crystallinities were extensively investigated by the dynamic mechanical relaxation, positron annihilation and 13 C nuclear magnetic relaxation ( 13 C NMR). From complex dynamic tensile modulus, the activation energies of α 1 and α 2 relaxations were determined to be 97–118 and 141–176 kJ/mol, respectively. The activation energy of β relaxation was 114–115 kJ/mol. These values were similar to those of α 1 relaxation reported already. For γ relaxation mechanisms, there existed two mechanisms, γ 1 and γ 2 , the activation energies being 9–11 and 23–25 kJ/mol, respectively. The values were independent of the molecular orientation and crystallinity. The two local motions indicate that non-crystalline phase composes of two regions of non-crystalline phase, rubber-like amorphous phase and interfacial-like amorphous phase. From 13 C NMR measurements of 13 C longitudinal relaxation time for the non-crystalline phase, the activation energy was 20.7 kJ/mol. This value is close to the activation energy (23–25 kJ/mol) of the γ 2 relaxation estimated by the dynamic mechanical measurement. The result by 13 C NMR did not provide two kinds of activation energy, indicating combined influence of the two correlation times. Even so, the activation energies obtained by 13 C NMR indicated that the γ 2 relaxation mainly is due to the motion of the C–C central bond of a short segment (e.g. three to four CH 2 ) within interfacial-like amorphous phase. The γ and β relaxation peaks by the dynamic mechanical measurements corresponded to the first and second lifetime transition of ortho -positronium indicating, in turn, a drastic change in free volume by local mode relaxation.

Conformational order in crystalline states and gels of isotactic, syndiotactic and atactic polystyrenes studied by vibrational spectroscopy

Abstract Stable conformations and their sequential order of isotactic (IPS), syndiotatic (SPS) and atactic polystyrenes (APS) in various aggregation states have been investigated by infrared (IR) spectroscopy, 13 C NMR and X-ray diffraction. It has been demostrated that the partially ordered skeletal conformation existing in IPS/CS 2 gels is of a (3/1) helix (TG) type having the pendant phenyl groups oriented in a disordered fashion, rather than the near-TT [(12/1) helix] form proposed previously for IPS/decalin gels. The process of conformational change during gelation or IPS/CS 2 and APS/CS 2 systems has been followed by IR spectroscopy, and it has been concluded that the construction of regular sequences of a particular conformation promotes the gelation of both crystallizable and non-crystallizable polystyrenes. As-cast film specimens prepared from a chloroform solution are found to be crystalline polymer-solvent complex (the γ phase) having a TTGG conformation. On heating the γ phase transforms to a β phase at about 120°C, accompanied by removal of the solvent, while the TTGG conformation is retained. On further heating, the β phase transforms to an α 1 or α 2 phase at about 200°C accompanied by a change in conformation from TTGG to TT. The process of conformational change (in both type and sequence) during these phase transformations has been clarified by IR spectroscopy.

Enantioselective complexation of chiral linear hosts containing monosaccharide moieties with chiral organic amines

Abstract New chiral linear hosts ( 1–3 , a : peracetylated derivatives, b : permethylated derivatives) containing monosaccharide end groups were designed on the basis of the structural features of permethylated 1F-fructonystose (MeFruNys), which shows a remarkable chiral discrimination ability, and then synthesized. The chiral discrimination ability of their hosts toward chiral organic ammonium guests were evaluated using FAB mass spectrometry and 1H NMR. Their hosts showed chiral discrimination for some guests. As the contrasting compounds ( 4 and 5 ) hardly showed any chiral discrimination, it was clarified that the structural features extracted from MeFruNys are very significant factors for chiral recognition. The 1H NMR shift induced by adding a potassium ion (counter anion: SCN−) in (CD3)2CO suggested that the cation moiety of the chiral guests was located at the binding site consisting of the –O–C–C–O– units and the ring-oxygens of the saccharide moieties. The structure of the complex of host 1b with 1-(1-naphthyl)ethylammonium ion (NEA+) was estimated by the 1H NMR induced shifts and the molecular dynamics simulation.

Local conformation of glassy polystyrenes with different stereoregularity

Abstract The molecular structure of glassy polystyrenes with different stereoregularity was investigated by infrared, Raman, and solid state high resolution 13 C NMR spectroscopies. The characteristic bands observed in infrared spectrum closely relates to the regular sequence length of conformational arrangement. The out-of-plane mode of phenyl ring in 500–600 cm −1 region, which is one of the most conformational sensitive bands for polystyrene, provided no characteristic peaks concerned with longer regular sequence than four monomers. Raman spectrum showed that most of the bands providing different peaks among polystyrenes with different stereoregularity are assumed local phenyl ring modes. Solid state high resolution 13 C NMR is available to estimate the gauche content in terms of analysis based on γ- gauche effect. We determined that the gauche content takes 25.0, 27.9, and 34.3% for glassy state of syndiotactic, atactic, and isotactic polystyrenes, respectively. This indicates that the conformational structure of sPS tends to take trans sequence. Since a large content of trans sequence would make the molecular dimension wide, the glassy sPS provided the smallest density for polystyrenes with different stereoregularity.

Structural study of syndiotactic polypropylene gel by solid-state high resolution 13C n.m.r.

Abstract The molecular conformation and the phase structure of syndiotactic polypropylene gel were studied by infra-red and solid-state high resolution 13 C n.m.r. spectroscopies. It was found that the trans—trans—gauche—gauche molecular conformation, that is most energetically stable in the bulk crystalline state of this polymer, is also formed in the gel. However, the methylene resonance lines of the gel observed in solid-state 13 C n.m.r. spectrum are somewhat different from that of the bulk crystal. The origin of this difference is attributed to a difference in the intermolecular interaction. The investigation of the phase structure revealed that the gel generally comprises three phases; the crystalline phase, noncrystalline amorphous phase, and crystalline—amorphous interphase in a similar manner to the bulk crystals. About 64% of solvent molecules in the gel are incorporated in the crystalline—amorphous interphase as bound solvent and another 34% are in the amorphous phase as free solvent.

High-resolution solid-state 13C n.m.r. study of isotactic polypropylene gel

Abstract The molecular conformational structure of isotactic polypropylene (iPP)/ o -dichlorobenzene gel is investigated by means of solid-state high-resolution 13 C n.m.r. spectroscopy. It was revealed from the resonance line of methylene carbon at the position generating one γ-gauche effect that the gel-forming crystal takes a 3 1 helical molecular conformation. However, the resonance lines observed for the gel were very broad. In order to deconvolute overlapping peaks, the Lorentzian type peak was converted to Gaussian one by computational analysis. The crystalline component of the resonance line consists of two peaks, of which the chemical shifts were identified with those for the α-iPP crystal. However, the peak intensity ratio of the downfield line to the upfield one in the gel, 1:2, was opposite to the 2:1 ratio in the α-iPP crystal usually reported for melt crystallised films. This is thought to be due to the difference of interchain interaction within the crystal cell. The crystal structure and the crystallinity of the gel were independent of the polymer concentration. The gel-forming crystal did not take a polymer—solvent complex as in the case of polystyrene gel.

Comparison of Absorption Kinetics of Ethanol and Butanol into Different Size Nanopores Present in Syndiotactic Polystyrene and Poly(P-Methylstyrene)

The absorption kinetics of ethanol and butanol isomers diffused into the pores of the crystal units of syndiotactic polystyrene (sPS) and syndiotactic poly(p-methylstyrene) (sPPMS) cast from m-xylene was investigated by infrared spectroscopy. The OH stretching mode of these alcohols absorbed in the pores of sPS and sPPMS was observed at 3592 cm−1, which does not correlate with the presence of hydrogen bonding. This finding indicates that the alcohol molecules are isolated from others in the small pores of the crystal units. The diffusion of ethanol into the pore of sPPMS was about ten times faster than that of sPS. The number of ethanol molecules included in the unit cell of the crystal was 3.9 and 7.6 for sPS and sPPMS at equilibrium. This corresponds to the incorporation of 1.9 and 3.8 ethanol molecules in one cavity in the crystal unit for sPS and sPPMS, respectively. Experiments probing the absorption of differently shaped butanol isomers showed that three of them were absorbed in the pores of both sPS and sPPMS, while tert-butanol was only absorbed by sPPMS. Apparently, only the pores of sPPMS are enough large to absorb tert-butanol. The diffusion coefficient of tert-butanol into the pore of sPPMS was about twenty-five times slower than that of n-butanol.

Individual evaluation of cardiac marker expression and self‐beating during cardiac differentiation of P19CL6 cells on different culture substrates

Cell-based therapies using self-beating cardiomyocytes have been attracting great attention for use in cardiac regeneration, although an effective procedure to improve cardiac differentiation and self-beating induction is required. The purpose of this study is to clarify the effect of the culture substrate on cardiac maturation by separately evaluating the cardiac differentiation step and the beating induction step in vitro. To this end, the well-studied cardiomyocyte-like progenitor cell line P19CL6 and neonatal cardiomyocytes (NCMs) were selected and cultured on substrates coated with collagen type I (Col-I), gelatin (Gel), fibronectin (FN), or poly-l-lysine (PLL). It was found that the cardiac differentiation step, which was assessed using cardiac marker gene expression (GATA-binding protein 4 (GATA4), myocyte-specific enhancer factor 2D (MEF2D), and hyperpolarization-activated cyclic nucleotide-gated potassium channel 4 (HCN4)) in the P19CL6 embryonal carcinoma cells, was greatly enhanced on Col-I, Gel, and PLL. In contrast, the spontaneous beating step, which was directly assessed by counting the beating colonies and measuring contractile protein gene expression (α-myosin heavy chain (α-MHC), troponin C type 1 (TnC1), and troponin T type 2 (TnT2)) in the rat NCMs, was enhanced on the FN and PLL surfaces. In the present study, for the first time, it was found that PLL enhances both the cardiac differentiation and the beating induction steps of cardiac maturation, which can aid in preparing beating cardiomyocytes for regenerative medicine.

Rapid and Sensitive Detection of Brain-Derived Neurotrophic Factor with a Plasmonic Chip

Plasmonic chips, which are grating replicas coated with thin metal layers and overlayers such as ZnO, were applied in immunosensors to improve their detection sensitivity. Fluorescence from labeled antibodies bound to plasmonic chips can be enhanced on the basis of a grating-coupled surface plasmon resonance (GC-SPR) field. In this study, as one of the representative candidate protein markers for brain disorders, the brain-derived neurotrophic factor (BDNF) was quantitatively measured by sandwich assay on a plasmonic chip and detected on our plasmonic chip in the concentration of 5–7 ng/mL within 40 min. Furthermore, BDNF was detected in the blood sera from three types of mice: wild-type mice and two types of mutant mice. This technique is promising as a new clinical diagnosis tool for brain disorders based on scientific evidence such as blood test results.

Label-Free Separation of Induced Pluripotent Stem Cells with Anti-SSEA-1 Antibody Immobilized Microfluidic Channel

When induced pluripotent stem cells (iPSCs) are routinely cultured, the obtained cells are a heterogeneous mixture, including feeder cells and partially differentiated cells. Therefore, a purification process is required to use them in a clinical stage. We described a label-free separation of iPSCs using a microfluidic channel. Antibodies against stage-specific embryonic antigen 1 (SSEA-1) was covalently immobilized on the channel coated with a phospholipid polymer. After injection of the heterogeneous cell suspension containing iPSCs, the velocity of cell movement under a liquid flow condition was measured. The mean velocity of the cell movement was 2.1 mm/sec in the unmodified channel, while that in the channel with the immobilized-antibody was 0.4 mm/sec. The eluted cells were fractionated by eluting time. As a result, the SSEA-1 positive iPSCs were mainly contained in later fractions, and the proportion of iPSCs was increased from 43% to 82% as a comparison with the initial cell suspension. These results indicated that iPSCs were selectively separated by the microfluidic channel. This channel is a promising device for label-free separation of iPSCs based on their pluripotent state.