Amino acid end-group in commercial heparin. III. Determination of the number of amino groups of amino acid and hexosamine residues per heparin molecule

The reactions of heparin with 2,4,6-trinitrobenzenesulfonic acid (TNBS) were studied spectrometrically. Seven different commercial heparins were used in this study. The amino groups react with TNBS to form equimolar amounts of trinitrophenylated (TNP) amino groups and bisulfite ions. The TNP-amino groups further react with bisulfite ions to form the monosubstituted anionic sigma complex. The absorption spectrum with two maxima at approximately 350 nm and approximately 420 nm, characteristic of either the TNP-amino groups or the complex, was analyzed for the reaction of TNBS with heparin. It was shown that the reactivities of TNBS with amino groups from α-amino acid and hexosamine residues are greatly different. By combining the results of the reaction kinetics and the reaction of heparin with Sanger's reagent, the number of the α-amino groups and the free amino groups in hexosamine residues were determined. These data have been performed with a range of heparins from different commercial sources, of different activities and physical characteristics. No correlation was found between the free amino contents of these heparins and biological potency. © 1993 John Wiley & Sons, Inc.     

Fluorometric sensing of alkaline Earth metal cations by new lariat ethers having plural pyrenylmethyl groups on the electron-donating sidearms

[structure: see text] New fluorescent compounds (1), lariat ethers having plural pyrenylmethyl groups on the sidearms, were prepared, and their complexation behavior with alkaline earth metal cations was examined by fluorescence spectrometry. The pyrene excimer emission decreased accompanied with an increase in the monomer emission upon complexation with the metal ion. This finding is ascribed to the cooperative participation of one of the two sidearms in the complexation of the crown ring with the metal ion.     

Spectroscopic and Electrochemical Characterization of Cytochrome P450st‐DDAB Films on a Plastic‐Formed Carbon Electrode

We have studied the characterization of thermophilic cytochrome P450 (P450st)‐didodecyldimethylammonium bromide (DDAB) films by using UV‐vis absorption, resonance Raman spectroscopy, and electrochemical methods. The observed Raman spectrum indicated near‐native conformation of the heme iron in DDAB film on the surface of a glass slide, while on the surface of a plastic‐formed carbon (PFC) electrode, the conformation of P450st‐DDAB was very similar to that of heme‐DDAB film, suggesting the release of heme from P450st in DDAB films on PFC electrodes. When NaBr was added as salt to the casting solution, the result of Raman spectrum indicated near‐native conformation of P450st in DDAB film even on the PFC electrode, but no redox potential of P450st which has near native structure was observed. This study suggests the essential experimental conditions when working with heme protein‐DDAB films as, in some cases, heme iron from proteins is released on the surface of the electrode.     

Synthesis and γ-radiolysis of 2′-deoxy-5-fluorouridine and 5-fluorouridine derivatives

Seventeen compounds having a variety of substituents at the 3- and 5′-positions of 2′-deoxy-5-fluorouridine (5-FUdR) and 5-fluorouridine (5-FUR) were synthesized, and their γ-radiolysis in aqueous solutions were studied. The compounds having thioureido (RNHCSNH, R ? H, PhCH₂, acyl) and thiocarbonylamino (XCSNH, X ? PhCH₂S, PhO) groups at the 3-position of 5-FUdR were efficiently cleaved to give 5-FUdR with high G values upon γ-irradiation of their aqueous solutions. The active species for these cleavage reactions were hydrated electron (e^? _aq), H^? and HO^?. However, the compounds having a dimethylsulfoxyimino group at 3-position of 5-FUdR and 5-FUR afforded 5-FUdR and 5-FUR only under the radiolysis conditions where e^? _aq becomes a principal active species. The compound having a 2-benzoylthiazoylthiocarbonylamino group at the 3-position of 5-FUdR showed the highest reactivity toward HO^.. The mechanisms of these γ-radiolysis reactions are discussed. The examination of anticellular activities of γ-irradiated compounds having a thiocarbonylamino group at the 3-position of 5-FUdR toward murine Sarcoma 180 cells revealed that these compounds may be utilized as a candidate for a radiation-induced drug (RID).     

Asymmetric michael addition of aromatic thiols to 2-cyclohexenone and maleic acid esters via formation of crystalline cyclodextrin complexes

The asymmetric Michael addition of aromatic thiols to 2-cyclohexenone and maleic acid esters has been carried out by utilizing their crystalline cyclodextrin complexes suspended in water. The best chiral induction, 30% enantiomeric excess (ee), was achieved in combinations of 2-cyclohexenone and octyl maleate with the crystalline -cyclodextrin complex of benzenethiol (method A) to afford (S)-3-phenylthiocyclohexanone and (S)-octyl-2-phenylthiosuccinate, respectively, whereas the reaction of benzenethiol with 2-cyclohexenone included in -cyclodextrin (method B) inversely induced the chiral recognition to give the (R)-adduct with 4–9% ee.     

Asymmetric halogenation and hydrohalogenation oftrans-cinnamic acid in crystalline cyclodextrin complexes

Asymmetric halogenation and hydrohalogenation oftrans-cinnamic acid have been achieved in the microcrystals of cyclodextrin complexes. The bromination of the organic acid in the cavity of -cyclodextrin gave theerythro-dibromide in 40 % optical yield which was much larger than that from the resolution treatment of the racemic dibromide with -cyclodextrin and the absolute configuration was opposite in sign. The asymmetric induction in the gas-solid reaction was not due to optical resolution but to the reaction itself which was influenced by the chiral frame of cyclodextrin. The reaction shows the molecular size effect that the acid in the cavity of -cyclodextrin reacted with smaller hydrogen bromide but did not with larger bromine and chlorine. In contrast, the guest molecule in the wider cavity of -cyclodextrin reacted with bromine and chlorine as well as hydrogen bromide. The stereospecificities of the gas-solid halogenations of the acid in -cyclodextrin were similar to those of the both reactions in the solid state and in carbon tetrachloride solution without -cyclodextrin: bromination of the acid yieldederythro-2, 3-dibromo-3-phenylpropionic acid stereospecifically in 100 % in three different conditions, but chlorination gave an excess ofthreo-2, 3-dichloro-3-phenylpropionic acid to theerythro-isomer in 7287 % yields.     

Solid-state optical properties of a chiral supramolecular fluorophore consisting of chiral (1R,2R)-1,2-diphenylethylenediamine and fluorescent carboxylic acid derivatives

By using (1R,2R)-1,2-diphenylethylenediamine as a chiral molecule and 2-anthracenecarboxylic acid as a fluorescent molecule, we created a chiral supramolecular organic fluorophore having circularly polarized luminescence properties in the solid-state.     

Linear free energy relationships for carbon-13 NMR chemical shifts of substituted benzoic acids1

In order to examine ¹³C-SCS of substituted benzoic acids, chemical shifts of the acid form (I) and the dissociated form (II) have been obtained separately. Single substituent parameters, σ⁰ or σ⁺ are correlated with the shifts for the carboxyl (δ_co) or ipso carbons (δ_ipso), respectively. Among the available five equations which are developed for the analysis with dual (or divided) substituent parameters (DSP), the Swain-Lupton equation (eqn 3) and the Taft-Swain-Lupton equation (eqn 4) give much better correlations, not only for δ_co and δ_ipso but also for the results for ring carbons (C(2), C(5), C(6)), except for those attached to or neighboured by substituents. It is concluded that the SCS of aromatic compounds are best analyzed with substituent parameters derived from reactions or equilibria on the basis of linear free energy relationships.     

Perfectly dissolved boron nitride nanotubes due to polymer wrapping

We report for the first time that boron nitride nanotubes (BNNTs) may be dissolved in organic solvents by wrapping them with a polymer. Transmission electron microscopy and cathodoluminescence studies indicate the strong pi-pi interactions between BNNTs and the polymer. A band gap ranging from 5.2 to 5.5 eV was documented for the BNNTs independent of their geometrical characteristics by using ultraviolet-visible absorption experiments on composite films and thin BNNT films prepared from solutions.     

Synthesis and characterization of soluble polymides from 2,5-bis(4-aminophenyl)-3,4-diphenylthiophene and aromatic tetracarboxylic dianhydrides

2,5-Bis(4-aminophenyl)-3,4-diphenylthiophene, a polyimide-forming monomer, was prepared in three steps starting from benzyl chloride and sulfur. Novel polyimides were synthesized from the diamine and pyromellitic dianhydride or 3,3′, 4,4′-benzophenonetetracarboxylic dianhydride (BTDA). Polymerization was carried out either by the usual two-step procedure that included ring-opening polyaddition giving polyamic acids, followed by cyclodehydration to polyimides, or by the direct one-pot procedure involving cyclodehydration in situ. The polyimide derived from the diamine and BTDA, especially that prepared by the one-pot procedure in m-cresol containing isoquinoline, is soluble in various organic solvents and gave a yellow, transparent, tough, and flexible film. Solubility of this polyimide varied by the preparative method and by the copolymerization with bis(4-aminophenyl) ether. All the polyimides are highly thermally stable and exhibited no appreciable decomposition up to 450°C in air and nitrogen atmospheres.