Estimation of frequency- and time-dependence of polymer composite system by viscoelasticity in three dimensions

This paper is concerned with the comparison between mechanical properties of polymer composite system and those of each individual constituent. The comparison is mainly performed with respect to the viscoelastic Young's modulus and the relaxation Young's modulus. These mechanical constants may be obtained from the correspondence principle by applying the Laplace transform to the constitutive equation. The calculated results exhibit that the mechanical property of polymer composite system strongly depends on that of matrix with respect to frequency- and time-dependences. That is, as for the vibration and dynamic response in the steady state, the frequency-dependence of peak position about imaginary part of dynamic modulus of composite system is similar to that of matrix, while the magnitude of dynamic modulus depends on volume fraction of dispersed particles to total volume. As for the stress relaxation, the time-dependence of the relaxation Young's modulus of composite system resemble that of matrix each other, while the magnitude depends on the volume fraction of dispersed particles to total volume. This is due to the calculating condition that particle is assumed to be very rigid in comparison with matrix in this paper.     

Experimental determination of ionization potentials of tetraphenylporphine and metallotetraphenylporphines

Gas-phase ionization potentials of tetraphenylporphine and some metallotetraphenylporphines have been determined by the method of photocurrent measurements in nonpolar solvents reported previously [1]. The values obtained range from 5.9 to 6.3 eV, depending on the central metal ion, correlating well with the reported polarographic oxidation potentials. It has been concluded that photoelectron ejection from these complexes in isooctane occurs from the porphyrin π-system in all cases including Co(II) tetraphenylporphine, in which the electron is thought to be removed from the metal in polar solvents.     

220-MHz NMR spectra of acrylic monomer–2-substituted 1,3-diolefin alternating copolymers

An investigation by 220-MHz NMR spectroscopy was carried out on the alternating copolymers of acrylic monomer with 2-substituted 1,3-diolefin. The chain structures were determined. The acrylic monomers used were methyl methacrylate (MMA), acrylonitrile (AN), and methacrylonitrile (MAN); isoprene (IP) and chloroprene (CLP) were the 1,3-diolefins. In the MAN–IP alternating copolymer, the 1-position methylene protons of IP showed an AB quartet peak, confirming the α-1 linkage structure. Similarly, in the MMA–CLP and AN–CLP copolymers, the 1-position methylene protons of CLP showed and AB quartet and an ABX pattern, respectively, confirming the α-1 linkage structure in both these cases also. The α-1 linkage structure was also revealed by the decoupling technique in the MAN–CLP alternating copolymer. The AN–IP and MMA–IP alternating copolymers also possess a bond between the α-position of the acrylic monomer and the 1-position of IP. The monomeric units in the alternating copolymers of acrylic monomers with 2-substituted 1,3-diolefins were generally linked at the α-position of acrylic monomer and the 1-position of 1,3-diolefin. On the other hand, in the Diels-Alder adducts of acrylic monomer with 2-substituted 1,3-diolefin, the reaction takes place between the α-position of acrylic monomer and the 4-position of 1,3-diolefin. The regioselectivity of the alternating copolymers and the Diels-Alder adducts is quite compatible with the expectations from molecular orbital theory.     

Prodrugs of 2',3'-dideoxyinosine (DDI): improved oral bioavailability via hydrophobic esters.

Five ester prodrugs of 2'3'-dideoxyinosine (DDI) were synthesized for the purpose of improving oral bioavailability. The prodrugs, acetate (C2-DDI), octanoate (C8-DDI), stearate (C18-DDI), benzoate (Bz-DDI), and hemisuccinate (Suc-DDI) were proved to quantitatively regenerate their parent drug by enzymatic hydrolysis. Though the chemical stability of the prodrugs under acidic conditions was not improved, their solubility in water was significantly decreased by esterification, except for Suc-DDI. Bioavailability was evaluated by oral administration to rats. Two hydrophobic prodrugs (C8-DDI and Bz-DDI) showed higher absolute bioavailability (23.5% and 31.0%, respectively) than did DDI (15.2%), though that of C2-DDI (11.5%) and Suc-DDI (4.5%) was poor.     

PULSE RADIOLYSIS STUDIES IN MODEL LIPID SYSTEMS: FORMATION AND BEHAVIOR OF PEROXY RADICALS IN FATTY ACIDS

Abstract— Radiolytic formation and peroxidation of fatty acid radicals have been investigated by pulse radiolysis techniques in oleate, linoleate, linolenate and arachidonate systems. A strong absorption band at 280 nm associated with conjugated radicals, R_conj, formed in polyunsaturated fatty acid moieties has been used as a probe for kinetic processes occurring at doubly allylic sites in the hydrocarbon chain. Formation of R_conj by O^- has been found to be more efficient than the less selective OH radical. Peroxidation of R_conj is shown to be somewhat slower, ( k _R+ O₂˜ 3 × 10⁸ M ^-1 s^-1), than O₂ reactions with radicals in oleate ( k _R+ O₂= 1 × 10⁹ M ^-1 s^-1). Peroxy radicals generated in these reactions disappear slowly by essentially second order processes (2 k RO₁˜ 10⁷ M ^-1 s^-1). The superoxide radical, O^-₂, shows little if any reactivity towards 0.01 M linolenate or arachidonate over periods of 20 s.     

Single-component nanodiscs via the thermal folding of amphiphilic graft copolymers with the adjusted flexibility of the main chain

Nanodiscs have attracted considerable attention as structural scaffolds for membrane-protein research and as biomaterials in e.g. drug-delivery systems. However, conventional disc-fabrication methods are usually laborious, and disc fabrication via the self-assembly of amphiphiles is difficult. Herein, we report the formation of polymer nanodiscs based on the self-assembly of amphiphilic graft copolymers by adjusting the persistence length of the main chain. Amphiphilic graft copolymers with a series of different main-chain persistence lengths were prepared and these formed, depending on the persistence length, either rods, discs, or vesicles. Notably, polymer nanodiscs were formed upon heating a chilled polymer solution without the need for any additives, and the thus obtained nanodiscs were used to solubilize a membrane protein during cell-free protein synthesis. Given the simplicity of this disc-fabrication method and the ability of these discs to solubilize membrane proteins, this study considerably expands the fundamental and practical scope of graft-copolymer nanodiscs and demonstrates their utility as tools for studying the structure and function of membrane proteins.

A strategy for the fabrication of nanodiscs via the self-assembly of thermoresponsive amphiphilic graft copolymers is demonstrated.     

Synthetic Studies on Sialoglycoconjugates 22: Total Synthesis of Tumor-Associated Ganglioside,Sialyl Lewis X1

ABSTRACT

The first total synthesis of tumor-associated glycolipid antigen, sialyl Lewis X is described. Glycosylation of 2-(trimethylsilyl)ethyl O-(2-acetamido-4,6-O-benzylidene-2-deoxy-β-D-glucopyranosyl)-(1→3)-O-(2,4,6-tri-O-benzyl-β-D-galactopyranosyl)-(1→4)-2,3,6-tri-O-benzyl-β-D-glucopyranoside (1) with methyl 2,3,4-tri-O-benzyl-1-thio-β-L-fuco-pyranoside (4) gave the α-glycoside (5), which was converted by reductive ring-opening of the benzylidene acetal into the glycosyl acceptor (6). Dimethyl(methylthio)sulfonium triflate-promoted coupling of 6 with methyl O-(methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-α-D-galacto-2-nonulopyranosylonate)-(2→3)-2,4,6-tri-O-benzoyl-1-thio-β-D-galactopyranoside (7) afforded the desired hexasaccharide 8 in good yield. Compound 8 was converted into the α-trichloroacetimidate 11, via reductive removal of the benzyl groups, O-acetylation, removal of the 2-(trimethylsilyl)ethyl group, and treatment with trichloroacetonitrile, which, on coupling with (2S, 3R, 4E)-2-azido-3-O-benzoyl-4-octa-decene-1,3-diol (12), gave the β-glycoside 13. Finally, 13 was transformed, via selective reduction of the azide group, condensation with octadecanoic acid, O-deacylation, and hydrolysis of the methyl ester group, into the title compound 16.     

Equivalent cross-relaxation rate imaging positively correlates with pathological grade and cell density of adipocytic tumors

Objective

Equivalent cross-relaxation rate imaging (ECRI) is an MRI technique used to evaluate qualitative changes in protein-water interactions. We aimed to prospectively evaluate the utility of ECRI for classification of adipocytic tumors.

Materials and Methods

Institutional Review Board approval was obtained and all patients provided informed consent. Study participants included 40 patients with adipocytic tumors who were diagnosed with lipomas (n = 22), atypical lipomatous tissue/well-differentiated liposarcoma (ALT/WDL; n = 9), myxoid/round cell liposarcoma (MyL; n = 6), and dedifferentiated liposarcoma (DDL; n = 3), and 20 control patients for whom subcutaneous fat in the buttock or thigh was analyzed.

Results

Mean ECR values of lipomas, ALT/WDL, and subcutaneous fat were low, and those of MyL and DDL were high. Mean ECR values of MyL and DDL were significantly higher than those of ALT/WDL. The cut-off value was 5.1%. There was a positive correlation between ECR value, pathological grade, and cell density in adipocytic tumors.

Conclusion

The ECR value positively correlates with pathological grade and cell density of adipocytic tumors. Our findings suggest that ECRI is a useful method for preoperative evaluation of adipocytic tumors.     

Dual Meissner effect and magnetic displacement currents

The dual Meissner effect is observed without monopoles in quenched SU(2) QCD with Landau gauge fixing. Magnetic displacement currents that are time-dependent Abelian magnetic fields act as solenoidal currents squeezing Abelian electric fields. Monopoles are not always necessary for the dual Meissner effect. A mean-field calculation suggests that the dual Meissner effect through the mass generation of the Abelian electric field is related to a gluon condensate A(a)(mu)A(a)(mu) not equal 0 of mass dimension 2.