Polymorphic forms of nylon 3

The crystal structure of nylon 3 was studied, and four crystalline modifications were observed. Modification I, as determined from the x-ray diffraction pattern of drawn fibers, is similar to the α crystal structure of nylon 6. The unit cell is monoclinic; a = 9.33 Å, b = 4.78 Å, (fiber identity period), c = 8.73 Å, and β = 60°. The theoretical density for nylon 3 with four monomeric units in the unit cell is 1.39 g/cm³, and the observed density is 1.33 g/cm³. The space group is P2₁. The nylon 3 chains are in the extended planar zigzag conformation. Although other odd-numbered nylon form triclinic or pseudohexagonal crystals when oriented, drawn nylon 3 crystals are monoclinic. In addition to modification I, modifications II, III, and IV were studied. Lattice spacings of modifications II and III are equal to those of modification I. However x-ray diffraction intensities are different. Infrared spectra of those forms indicate an extended planar zigzag conformation of the chains. Modification IV is thought to correspond to the so-called smectic hexagonal form. No γ crystals were found, and it appears that polyamide chains with short sequences of methylene groups cannot form crystals of this type.     

Syntheses and biological activities of endothelin-1 analogs.

Endothelin-1 analogs replaced by various amino acids at position 21, namely [X21]-ET-1, were synthesized, and their agonistic vasoconstrictor activity on rat thoracic aortic strips and receptor binding activity on rat brain membrane fraction were examined to elucidate their structure-activity relationship. The vasoconstrictor activities of [Tyr21]- and [Phe21]-ET-1 were one order of magnitude smaller than that of ET-1, and those of [His21]-, [Gly21]-, [Ser21]-, [Ala21]- and [Lys21]-ET-1 were more than two orders of magnitude smaller than that of ET-1. On the other hand, the replacements by Ile, Glu, Gln and Pro resulted in distinguished losses of the vasoconstrictor activities. In addition, preincubation with these analogs did not blunt ET-1-induced vasoconstriction and showed no antagonistic activity. The binding inhibitory activities of these analogs against 125I-ET-1 were approximately conformable to the vasoconstrictor activities with only a slight exception. These findings demonstrate that the phenyl group at position 21 is important for both the vasoconstrictor activity and the receptor binding activity.     

Gas transport in poly [bis(trifluoroethoxy) phosphazene] above the T(1) transition

Gas permeation measurements were performed by the time-lag method for 13 gases in poly [bis(trifluoroethoxy) phosphazene] above the mesophase transition, T (1) transition, of the crystals. Hysteresis was found in the temperature dependence of the permeability coefficients for CO₂, O₂, and N₂ in the transition region as observed by dilatometry and differential scanning calorimetry. Independently the solubility of CO₂ was determined gravimetrically above and below T(1). Noticeable change and hysteresis were also observed in the temperature dependence of the solubility coefficients. Diffusion of CO₂ in the measophase is suggested from the permeation and sorption measurements. Gas transport parameters of CO₂ in the mesophase are estimated, and the contributions of the mesophase and the crystalline phase to gas transport are considered.     

Pyrolysis of sulfoxide. III. Conversion of 2-(phenylsulfinyl)enoate to 2,4-dienoate and synthesis of pellitorine

2,4-Dienoate was prepared by pyrolysis of 2-(phenylsulfinyl)enoate. N-Isobutyl-E,E-2,4-decadieneamide (pellitorine) was synthesized from decanoic acid in a satisfactory yield.     

Coexistence of light and heavy carriers associated with superconductivity and antiferromagnetism in CeNi0.8Bi2 with a Bi square net

We found that the ZrCuSiAs-type crystal CeNi(0.8)Bi(2) with a layered structure composed of alternate stacking of [CeNi(x)Bi(1)](δ+) and Bi(2)(δ-) exhibits a superconductive transition at ～4 K. The conductivities, magnetic susceptibilities, and heat capacities measurements indicate the presence of two types of carriers with notable different masses, i.e., a light electron responsible for superconductivity and a heavy electron interacting with the Ce 4f electron. This observation suggests that 6p electrons of Bi(2) forming the square net and electrons in CeNi(x)Bi(1) layers primarily correspond to the light and heavy electrons, respectively.     

Regio- and Stereoselective Oxidation of Ene-Type Chlorinated Olefins

Regio- and stereoselective oxidation of ene-type chlorinated olefins has been achieved by using potassium 2-propanenitronate as an oxidant and tetrakis(triphenylphosphine)palladium as a catalyst.     

Diffusion or bounce back in relativistic heavy-ion collisions?

The time evolution of pseudorapidity distributions of produced charged hadrons in d + Au collisions at = 200 GeV is investigated. Results of a nonequilibrium statistical relativistic diffusion model with three sources are compared with a macroscopic “bounce-back” model that does not allow for statistical equilibration at large times, but instead leads to motion reversal. When compared to the data, the results of the diffusion approach are more precise, thus emphasizing that the system is observed to be on its way to thermal equilibrium.     

Enzymatic synthesis and characterization of amphiphilic block copolymers of poly(ethylene oxide) and amylose

Amphiphilic A‐B block copolymers, ω‐methoxypoly(ethylene oxide)‐amylose copolymers (MPEO‐amylose), were synthesized by an enzymatic reaction using potato phosphorylase from an MPEO (M_w = 5.0×10³)‐maltopentaosylamine derivative as a primer and α‐D ‐glucose‐1‐phosphate as a substrate. MPEO‐amyloses with various molecular weights of amylose (DP = 26, 36, 73 and 112) were obtained. None of the MPEO‐amyloses (5 mg/ml) precipitate in water containing 10 vol.‐% DMSO even after 24 h. The MPEO‐amyloses effectively form complexes with iodine in water.