Adsorption of immunogamma globulin onto various synthetic calcium hydroxyapatite particles

This paper presents data on adsorption of immunogamma globulin (IgG) onto synthetic rodlike calcium hydroxyapatite particles (CaHaps) with various particle lengths and calcium/phosphate (Ca/P) atomic ratios ranging from 1.54 to 1.65 and compares the obtained results to those of acidic (bovine serum albumin, BSA), neutral (myoglobin, MGB), and basic (lysozyme, LSZ) proteins reported before. The effect of electrolyte concentration on IgG adsorption was also examined. The initial rate of IgG adsorption was similar to that of BSA and was slower than that of MGB and LSZ. This fact was interpreted by the difference in the structural stability and molecular weight of these proteins. The isotherms of IgG adsorption onto the CaHap particles were of pseudo-Langmuir type. The saturated amount of adsorbed IgG values (nsIgG) for the particles with mean particle length less than 70 nm decreased with increasing Ca/P ratio. The adsorption behavior of IgG molecules was very similar to that of basic LSZ, though IgG has zero net charge. The nsIgG value was increased with increased mean particle length of CaHaps; the relationship was less significant than that for BSA but similar to those for MGB and LSZ. The similar adsorption behavior of IgG and LSZ suggested that the Fab parts of IgG molecules preferentially adsorb onto CaHap to provide the reversed Y-shaped conformation of IgG. The change of the adsorption mode of IgG molecules from the reversed Y-shaped conformation to side-on by "spreading" the Fc part of IgG molecules onto the particle surface over a longer adsorption time was suggested. The nsIgG value was increased with increasing electrolyte concentration by screening the intra- and intermolecular electrostatic interactions of proteins.     

Dual memory of enantiomeric helices in a polyacetylene induced by a single enantiomer

We report the dual memory of both the enantiomeric right- and left-handed helical conformations induced in a polyacetylene based on the temperature-stimulated helicity inversion of the polymer. The polyacetylene folds into a one-handed helix induced by noncovalent bonding interactions with a single enantiomeric amine. The induced helix underwent a reversible inversion of the helicity by temperature. The diastereomeric right- and left-handed helices obtained at different temperatures could be further memorized when the optically active amine was replaced by an achiral diamine, generating right- and left-handed helices of the mirror images of each other. Consequently, both enantiomeric helices can be produced with a high efficiency from dynamically diastereomeric helical polyacetylenes induced by a single enantiomer.     

First example of the Mislow-Braverman-Evans rearrangement retaining the sulfur atom on the original carbon

Treatment of 1-chloro-2-methylalkenyl p-tolyl sulfoxides with N-lithio 2-piperidone in THF at room temperature resulted in the formation of 1-chloro-2-(hydroxymethyl)alkenyl p-tolyl sulfides in good yields. This reaction is the first example of the Mislow-Braverman-Evans rearrangement retaining the sulfur atom on the original carbon.     

Resolution of racemic aryl dichloromethyl sulfoxides with (−)-menthone

The addition reaction of the sodium α-sulfinyl carbanion of a racemic aryl dichloromethyl sulfoxide to (?)-menthone in the presence of boron trifluoride diethyl etherate gave an adduct as a mixture of two easily separable diastereomers. After separation of the diastereomers, they were each treated with sodium hydride to afford enantiomerically pure aryl dichloromethyl sulfoxides and (?)-menthone both in high yields. This procedure provides a simple and efficient method for the resolution of racemic aryl dichloromethyl sulfoxides.     

A tong-like fluorescence sensor for metal ions: perfect conformational switch of hinge sugar by pyrene stacking

Carbohydrates are among the potential materials for molecular devices, since they are abundant natural resources. However, their rigidity has restricted their use for movable devices. Hinge sugars, 2,4-diamino-2,4-dideoxy-xylopyranosides, shed light on the use of carbohydrates as movable components, as demonstrated by the motion by which all four equatorial substituents can change to an axial orientation in synchronization with a chelation-driven 4C1-1C4 ring flip. In this study, we synthesized a tong-like metal ion sensor, 1,3-di-O-pyrenylmethylated hinge sugar (1), and its model compound, methyl 2,4-di-O-pyrenecarbonyl-xylopyranoside (2), to extend the abilities of hinge sugars as molecular components. From observations of the solvent-dependent conformational and fluorescent behavior of 2, we found that the pyrene stacking assists the 1C4 formation of xylopyranoside by 1.7 kcal mol(-1). We also found that compound 1 produced excimer fluorescence by chelation to Pt2+, Zn2+, Cd2+, Mg2+ or Mn2+, and unexpectedly by addition of acids. 1H NMR measurements ascribed this behavior to the 4C1-1C4 ring flip of hinge sugar in response to chelation or protonation at N2, and revealed rapid and perfect 1C4 formation in the case of Zn2+. These findings will extend the scope of hinge sugars as movable components.     

Magnetic-field-induced Mott transition in a quasi-two-dimensional organic conductor

We investigated the effect of magnetic field on the highly correlated metal near the Mott transition in the quasi-two-dimensional layered organic conductor, kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Cl, by the resistance measurements under control of temperature, pressure, and magnetic field. It was demonstrated that the marginal metallic phase near the Mott transition is susceptible to the field-induced localization transition of the first order, as was predicted theoretically. The thermodynamic consideration of the present results gives a conceptual pressure-field phase diagram of the Mott transition at low temperatures.     

Proximity of pseudogapped superconductor and commensurate antiferromagnet in a quasi-two-dimensional organic system

We performed the single-crystal 13C NMR studies on a quasi-two-dimensional system, deuterated kappa-(BEDT-TTF)2Cu[N(CN)(2)]Br, which is just on the border of the Mott transition. The NMR spectra are separated into two parts coming from the metallic (superconducting) and insulating phases due to the phase separation at low temperature. The examination of the separated spectra revealed that the Mott transition in this system is characterized by the first-order transition between the pseudogapped superconductor and the simplest commensurate antiferromagnet with a moment of 0.26 mu(B)/dimer.     

Ferromagnetic and antiferromagnetic fluctuations of pi-d itinerant electrons disclosed by band-selective NMR

We present a band-selective NMR method to probe the constituent electronic bands separately in the condensed molecular matter. This method is applied to an organic-inorganic pi-d hybrid metal, and its utility to give the static and dynamic spin susceptibilities for the constituent bands is demonstrated. The analysis of the results uncovers an exotic feature; the antiferromagnetic and ferromagnetic correlations are enhanced in separate bands in a single material. This finding provides a novel scope connecting the metal-insulator transitions in this system and the manganese oxides.     

Radical polymerization behavior of a vinyl monomer bearing five‐membered cyclic carbonate structure and reactions of the obtained polymers with amines

Radical polymerization behavior of a vinyl substituted cyclic carbonate, 4‐phenyl‐5‐vinyl‐1,3‐dioxoran‐2‐one ( 1 ), is described. Radical polymerization of 1 proceeded through selective vinyl polymerization to produce polymers bearing carbonate groups in the side chain, in contrast to that of an oxirane analogue of 1 , 1‐phenyl‐2‐vinyl oxirane that proceeds via the selective ring‐opening fashion. Although the homopolymerization of 1 produce polymers in relatively lower yield, copolymerizations effectively provided cyclic carbonate‐containing copolymers. Nucleophilic addition of primary amines to the resulting homopolymers and copolymers produced the corresponding multifunctional polymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 584–592, 2005