Evaluation of the adsorption affinity of proteins to calcium hydroxyapatites by desorption and pre-adsorption methods

The adsorption affinity of bovine serum albumin (BSA) and lysozyme (LSZ) to calcium hydroxyapatite (CaHAP) was evaluated by desorption and two step adsorption methods. These experiments were carried out at 15°C in a 1×10⁻⁴ mol dm⁻³ KCl solution of pH 6.0. BSA molecules were scarcely desorbed, exhibiting an irreversible adsorption of BSA, though LSZ slightly desorbed. This result supports our previous findings that LSZ adsorbs weakly onto phosphate ions exposed on ac or bc faces of CaHAP while BSA adsorbs strongly onto positively charged sites on ac or bc faces of CaHAP. The amount of adsorbed LSZ was markedly increased by the pre-adsorption of BSA, where LSZ was adsorbed onto BSA-covered CaHAP. On the other hand, the amount of adsorbed BSA was not changed by the pre-adsorption of LSZ. In both pre-adsorption systems it was confirmed by an HPLC method that no protein molecule pre-adsorbed was desorbed after the post-adsorption procedure. Therefore, it was interpreted that the enhancement of adsorption of positively charged LSZ is induced by an electrostatic attractive force through pre-adsorption of negatively charged BSA molecules with a high coverage. However, since the coverage of LSZ onto CaHAP is considerably low, no stimulation of BSA adsorption occurred on the LSZ-covered surface. The formation of double protein adsorbed layers consisting of pre- and post-adsorbed proteins was proposed.     

Photophysics of aromatic molecules with low-lying pi sigma* states: excitation-energy dependence of fluorescence in jet-cooled aromatic nitriles

Excitation-energy dependence of fluorescence intensity and fluorescence lifetime has been measured for 4-dimethylaminobenzonitrile (DMABN), 4-aminobenzonitrile (ABN), 4-diisopropylaminobenzonitrile (DIABN), and 1-naphthonitrile (NN) in a supersonic free jet. In all cases, the fluorescence yield decreases rather dramatically, whereas the fluorescence lifetime decreases only moderately for S1 (pi pi*, L(b)) excess vibrational energy exceeding about 1000 cm(-1). This is confirmed by comparison of the normalized fluorescence excitation spectrum with the absorption spectrum of the compound in the vapor phase. The result indicates that the strong decrease in the relative fluorescence yield at higher energies is due mostly to a decrease in the radiative decay rate of the emitting state. Comparison of the experimental results with the TDDFT potential energy curves for excited states strongly suggests that the decrease in the radiative decay rate of the aminobenzonitriles at higher energies is due to the crossing of the pi pi* singlet state by the lower-lying pi sigma*(C[triple bond]N) singlet state of very small radiative decay rate. The threshold energy for the fluorescence "break-off" is in good agreement with the computed energy barrier for the pi pi*/pi sigma* crossing. For NN, on the other hand, the observed decrease is in fluorescence yield at higher excitation energies can best be attributed to the crossing of the pi pi* singlet state by the pi sigma* triplet state.     

Efficient synthesis of thioesters and amides from aldehydes by using an intermolecular radical reaction in water

The combination of the water-soluble radical initiator, 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (VA-044) and the surfactant, cetyltrimethyl-ammonium bromide (CTAB), was found to be the most suitable condition for the effective and direct synthesis of useful active thioesters (pentafluorophenyl thioesters) in water. In addition, the direct amidation of aldehydes was achieved by the addition of the amines to the thioesterification reaction mixture in water.     

Fractionation of metals and metalloids by chemical bonding from particles accumulated by electrostatic precipitation in an Argentine thermal power plant

A study was undertaken to evaluate the distribution of Al, As, Cr, Cu, Fe, Mn, Ni, Pb, Ti, V and Zn in fly ashes collected in the electrostatic precipitator of a thermal power plant in San Nicolás (Argentina). Five samples were collected during one week of operation. For the fractionation, the scheme applied consisted in extracting the elements in four fractions namely (i) soluble and exchangeable elements; (ii) carbonates, oxides and reducible elements; (iii) bound to sulfidic metals; and (iv) residual elements. Metals and metalloids at μg g^− 1 level were determined in each fraction by inductively coupled plasma optical emission spectrometry (ICP OES). For validation, a standard reference material (SRM 1633 coal fly ash) from NIST was subjected to the same chemical sequential extraction procedure that the samples. X-ray diffraction powder (XRD) analysis and scanning electron microscopy (SEM) were used to characterize the major minerals present in the matrix. Total analyte concentration (in μg g^− 1) varied from 10.6 for Pb to 17,622 for Al. Minimum and maximum concentrations (in μg g^− 1) found in individual samples in the four fractions were: Al, 92.7–9668; As, < 0.3–143; Cr, 2.0–10.4; Cu, < 0.2–35.6; Fe, < 0.3–4992; Mn, < 0.1–128; Ni, < 0.3–139; Pb, < 0.5–9.1; Ti, < 0.3–2243; V, 17.0–112.9; and Zn, < 0.1–68.2. The leachability of the 11 elements under study proved to be different. Low percentages of Al (1%), V (7%) and Cr (8%) were detected in the most bioavailable fraction. Arsenic was found to be most abundant in the non-silicate phase, represented by the second and third fractions, while Cr, Fe, Ni, Pb and Zn were mostly associated to the residual fraction.     

A temperature study on critical micellization concentration (CMC), solubility, and degree of counterion binding of α-sulfonatomyristic acid methyl ester in water by electroconductivity measurements

 For a sodium salt of α-sulfonatomyristic acid methyl ester (14SFNa), one of the α-SFMe series surfactants, critical micellization concentration (CMC), solubility and degree of counterion binding (β) were determined by means of electrocon-ductivity measurements at different temperatures (at every 5 °C) ranging from 15 to 50 °C. The phase diagram of 14SFNa in pure water was constructed from the CMC- and solubility-temperature data, in which the Krafft temperature (critical solution temperature) was found around 0 °C. The changes in the Gibbs energy, ΔG ⁰ _m, enthalpy, ΔH ⁰ _m, and entropy, ΔS ⁰ _m, upon micelle formation as a function of temperature were evaluated taking βvalues into calculation. Received: 28 August 1996 Accepted: 5 November 1996     

Synthesis of monohalocyclopropane derivatives from olefins by the reaction with trihalomethanes and copper

Fluoro-, chloro-, bromo-, and iodocyclopropane derivatives were obtained in 10–80% yields by the reaction of FCHI₂, ClCHI₂, BrCHI₂, and CHI₃, respectively, with Cu in the presence of olefins. The reaction was electrophilic, and proceeded stereospecifically, i.e., cis and trans olefins afforded cyclopropane derivatives whose configurations with respect to the substituents from original olefins were cis and trans, respectively. Since isomeric olefins were not detected in the reaction mixture which would be expected from the insertion of the corresponding free monohalocarbenes into C—H bonds, the reaction seemed to proceed via organocopper intermediates rather than free monohalocarbenes. With respect to the configuration of the halogen introduced by the new reaction, the cis or endo isomers were generally obtained predominantly over the corresponding trans or exo isomers.     

Is the light velocity in vacuum really a constant? Possible breakdown of the linear ω-k relation at extremely high frequencies

We investigate the novel problem of what happens in special relativity and in relativistic field theories whenthree-dimensional space is quantized. First we examine the equation for elastic waves on a linear chain, the simplest example of a quantized medium, and propose, on its analogy, a nonlinearp-k relationp=k(sinhkl)/kl for light and material waves. Here,kl is a new variable which represents the space-quantization effect on the plane wave of wave numberk=|k|. (Note thatkl=0 givesp=k.) This relation makes the light velocity in vacuum dependent onkl. We postulate, however, that the phase and group velocities of each individual light wave are still invariant, and try to generalize special relativity to the case ofkl 0. This can be simply done if the invariance ofkl is assumed. Our results suggest that localization might be a relative concept. One interesting consequence of our proposal is that relativistic field theories become automatically finite. This comes out without violating unitarity or causality. A precise measurement of velocities of high-energy photons or massive particles is desirable for checking our proposal.     

Synthesis and pharmacological activity of 4-amino-5-chloro-2-methoxy-N-[(2S,4S)-1-ethyl-2-hydroxymethyl-4- pyrrolidinyl]benzamide (TKS159) and its optical isomers

Of 4-amino-5-chloro-2-methoxy-N-(1-ethyl-2-hydroxymethyl-4- pyrrolidinyl)benzamide, four optical isomers, (2S,4S)-1 (TKS159), (2S,4R)-25, (2R,4S)-26 and (2R,4R)-27, were prepared from optically active 4-amino-1-ethyl-2-hydroxymethylpyrrolidine di-p-toluenesulfonate [(2S,4S)-14, (2S,4R)-17, (2R,4S)-20 and (2R,4R)-23, respectively]. The requisites, (2S,4S)-14, (2S,4R)-17, (2R,4S)-20 and (2R,4R)-23, were prepared from a commercially available trans-4-hydroxy-L-proline. The absolute configurations of (2S,4S)-1 (TKS159), (2S,4R)-25, (2R,4S)-26 and (2R,4R)-27 were spectroscopically determined. Of the benzamide derivatives, four optical isomers, (2S,4S)-1, (2S,4R)-25, (2R,4S)-26 and (2R,4R)-27, showed a relatively potent affinity for 5-hydroxytryptamine 4 (5-HT4) receptors in a radioligand binding assay ([3H]GR113808). The activities of 25-27 were less effective than that of 1 for the gastric emptying of a phenol red semisolid meal in rats. All this suggests that the most potent of the isomers was 4-amino-5-chloro-2-methoxy-N-[(2S,4S)-1-ethyl-2- hydroxymethyl-4-pyrrolidinyl]benzamide (1).     

Rapid determination of 89Sr and 90Sr in radioactive waste using Sr extraction disk and beta-ray spectrometer

A rapid determination method in which beta-ray spectrometry was combined with solid phase extraction using Sr Rad Disk was developed for the determination of ⁸⁹Sr and ⁹⁰Sr in low-level radioactive waste. Various amounts of ⁸⁹Sr, ⁹⁰Sr, and ⁹⁰Y retained by the Sr Rad Disk was measured by a beta-ray spectrometer, and it was found that both ⁸⁹Sr and ⁹⁰Sr were simultaneously determined with <30% error (2σ) at ⁸⁹Sr/⁹⁰Sr radioactivity ratio of 0.3 to 45. The present method was successfully applied to actual radioactive liquid waste samples arising from nuclear facilities in Japan Atomic Energy Agency. Strontium was simply separated from interfering nuclides such as ¹³⁷Cs and ¹⁵⁴Eu, and matrix components by the Sr Rad Disk, and the results obtained by beta-ray spectrometry was in good agreement with that of the conventional analysis.     

Topological polymer chemistry by dynamic selection from electrostatic polymer self-assembly

A collection of recent developments in topological polymer chemistry is presented. First, topological isomerism occurring on randomly coiled, flexible polymer molecules having cyclic and linear structures is discussed. Second, an electrostatic self-assembly and covalent fixation strategy has been developed for the synthesis of polymeric topological isomers. These isomers have double cyclic, manacle-, and theta-shaped constructions, and are prepared by using either linear or star telechelic polymer precursors having moderately strained cyclic ammonium salt groups, which carry multifunctional carboxylate counteranions. A technique of reversed-phase chromatography (RPC) is demonstrated as an effective means to separate polymers with different topologies, especially polymeric topological isomers. A further extension of topological polymer chemistry has been observed by dynamic selection from electrostatic polymer self-assembly to enable the effective formation of tadpole-shaped, cyclic-linear hybrid topologies.