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  • Physical Chemistry  (7)
  • 2-hydroxypropyl β-CD
  • Petrocoptis
  • 2005-2009
  • 1990-1994  (10)
  • 1975-1979
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  • 1
    ISSN: 1432-2048
    Keywords: Petrocoptis ; Petroglaucin ; Petrograndin ; Ribosome-inactivating protein ; rRNA N-glycosidase ; Translation (inhibition)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two new N-glycosidase type-1 ribosome-inactivating proteins (RIPs), denoted petroglaucin 1 and petrograndin, respectively, were isolated from the plantsPetrocoptis glaucifolia (Lag.) Boiss sp.viscosa (Rothm.) Laínz andPetrocoptis grandiflora Rothm. These new RIPs do not share H2N-terminal amino-acid sequence homology with petroglaucin (now denoted as petroglaucin 2), the only other type-1 RIP to be isolated fromP. glaucifolia (Arias et al. (1992) Planta186, 532–540). Petroglaucin 1 shares amino-acid sequence homology with RIPs from Cucurbitaceae while petroglaucin 2 and petrograndin do so with saporins and dianthin 30 (Caryophyllaceae). The new RIPs strongly inhibited protein synthesis at subnanomolar concentrations in rabbit reticulocyte lysates and other eukaryotic cell-free systems, but they were inactive on bacterial ribosomes.
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  • 2
    ISSN: 1432-2048
    Keywords: Petrocoptis ; Protein synthesis inhibitor ; Ribosome inactivating protein ; Translation (inhibition)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Petrocoptis glaucifolia, a paleoendemic member of the Caryophyllaceae from the North of Spain, was found to contain at least five proteins that inhibit protein synthesis in a rabbit reticulocyte lysate. One of them, for which the name petroglaucin is proposed, was purified to apparent electrophoretic homogeneity by chromatography through S-Sepharose Fast Flow, Sephadex G-75 and CM-Sepharose Fast Flow. The apparent Mr of the preparation was 27500. This protein does not contain appreciable glycan chains and displays 45.8% of NH2-terminal amino-acid sequence homology with some ribosome-inactivating proteins from Saponaria officinalis, another member of the Caryophyllaceae. Petroglaucin shows the following functional properties: (i) it strongly inhibits the rabbit-reticulocyte-lysate system and Vicia sativa cell-free extracts, both coded by endogenous messengers, and also inhibits poly(U)-directed polyphenylalanine synthesis by Vicia sativa cell-free extracts and purified rat-liver ribosomes; (ii) it shows much less inhibitory capacity in wheat-germ, Cucumis sativus and rat-liver cell-free systems coded by endogenous messengers; (iii) the inhibitory effects on purified rat-liver ribosomes were irreversible; (vi) it promotes the release of adenine from purified rat-liver ribosomes. The total activity of this translational inhibitor has been found to increase up to 11-fold during its purification, indicating that some regulatory factor that normally blocks the translational inhibitory activity of the ribosome-inactivating protein in crude extracts of the plant is removed during purification.
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  • 3
    ISSN: 1573-1111
    Keywords: β-cyclodextrin ; 2-hydroxypropyl β-CD ; phenothiazine ; photochemically-induced fluorescence spectroscopy ; molecular absorption spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The photo-oxidation reaction of phenothiazine has been studied in the presence ofβ-cyclodextrin (β-CD) and 2-hydroxypropylβ-cyclodextrin (HP β-CD). The influence of these organized media on the formation of the oxidation photoproduct upon UV irradiation has been investigated. Phenothiazine forms an inclusion complex with the cyclodextrins. The stoichiometry and formation constant of the complex formed with 2-hydroxypropyl β-CD have been calculated using the changes of the fluorescence emission signal and of the absorbance of the drug upon inclusion. An increase of the fluorescence intensity of the photogenerated product is attained when it becomes included inside the cyclodextrin cavity.
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 651-659 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The solubility behaviour of β-cyclodextrin in aqueous mixtures was studied by determining the interactions between the co-solvent and water. Three clear classes of co-solvent are evident. In the first, including ethanol, tetrahydrofuran and acetone, there is formation of clathrate hydrates by the co-solvent. In these systems the solubilization is a maximum at the mole fraction corresponding to the minimum in the partial excess molar volume. The second class, including such solvents as dimethyl sulphoxide and pyridine, forms strong molecular complexes with water, and here a valley and a plateau region occur in the solubility values. In the third class, including formamide and urea, a steady increase in the solubility is observed. For these highly polar solvents no maxima are observed in intrinsic solvent properties such as the partial excess molar volume.
    Additional Material: 6 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 22 (1990), S. 905-914 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The stability of some Schiff-bases formed between PLP and different amino acids has been investigated in a wide range of pH. The kinetic constants of formation of these compounds and their hydrolysis rate constants have been determined. Results show that the α-position of the carboxyl group of amino acid plays an important role on the mechanism of water attack upon the C=N—bond. The absence of ionic groups in the surroundings of that bond must be an important factor of stability. Bulky hydrophobic substituents in the amino acid, near the amine part, protect the imine bond against hydrolysis.
    Additional Material: 3 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 24 (1992), S. 67-78 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We studied the formation and hydrolysis of the Schiff base of pyridoxal-5′ -phosphate (PLP) and n-dodecylamine (DOD) by kinetic methods and found the formation rate constants to be much larger than those reported for related systems. This can be ascribed to the occurrence of local concentration of charges in the vicinity of the carbinolamine, which stabilizes the corresponding transition state of the dehydration reaction. On the other hand, the hydrolysis rate constants of our system were considerably smaller as a result of the 12-atom hydrocarbon chain acting as a bulky hydrophobic rest protecting the imine bond from attack by water.
    Additional Material: 4 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 22 (1990), S. 1017-1026 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This article presents the kinetic of formation of pentacyano(3-pyrazincarboxylate)ferrate(II) from pyrazincarboxylate and pentacyanoaquoferrate(II) ions in various isodielectric water-cosolvent mixtures at 298 K. The rate law is in the form d[Fe(CN)5(3-pzCO2)4-]/dt = kf[Fe(CN)5H2O-3] [pzCO2-]. Plots of log(kf/dm3 mol-1 s-1) vs. Dm-1 (where Dm is the bulk dielectric constant of the medium) and log(kf/dm3 mol-1 s-1) vs. the Grunwald-Winstein parameter are nonlinear for some of the mixtures and to each mixture corresponds a different behavior in respect to the above parameters. The plots of log(kf/dm3 mol-1 s-1) vs. the mol fraction of water are straight lines over the entire composition range studied, except for the water-methanol mixture. It is evident that the solvation phenomenon plays a dominant role and that the rate of formation is mediated by the dual solvent vectors, the overall basicity and acidity of the solvent mixtures.
    Additional Material: 4 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 25 (1993), S. 865-874 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A kinetic study on the basic hydrolysis of cephaloridine at pD= 10.5 was carried out by using the 1H—NMR technique. Epimerization at H7, a nucleophilic attack of hydroxyl ion on the β-lactam carbonyl group followed by the release of the pyridine molecule, and isomerization of the double bond at position 3 in the dihydrothiazine ring were the major reactions observed.Based on the results obtained, it should be emphasized that the presence of a pyridine group at 3′ results in a slightly increased formation constant for the exo methylene compound relative to other cephalosporins with different substituents at that position.The activation energy for the epimerization constant and the cleavage of the β-lactam ring at pD 10.5 was 21.2 kcal/mol. © 1993 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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  • 9
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Salt effects on the oxidation of the iron(II) complexes Fe(CN)4(bpy)2-, cis-(CN)2(bpy)2 and Fe(bpy)32+ by S2O82- as well as on the reaction Fe2+ + Co(NH3)5Cl2+ have been studied in concentrated electrolyte solutions at 298.2 K. We have gone from anion-anion to cation-cation reaction with the intermediate cases of anion-neutral and cation-anion reactions. Results show that the main cause of the kinetic salt effects observed is the interaction between supporting electrolytes and the solvent. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 26 (1994), S. 571-575 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions of the title substrate with a series of secondary alicyclic amines are subjected to a kinetic study in 44 wt% aqueous ethanol, 25.0°C, and ionic strength 0.2 M (KCl). The Brönsted-type plot (log kN vs. pKa of the amine, where kN is the second-order rate coefficient) obtained is linear with slope β = 0.53, which indicates a concerted mechanism. The predicted Brönsted break for a hypothetical stepwise mechanism is pKa0 = 8.7, which was not observed (pKa range of amines: 6-11). The same reaction in water is stepwise, which shows that the tetrahedral intermediate found in water is much destabilized by the change of solvent from water to aqueous ethanol. © 1994 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
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