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1.
Cs. Novák Zsuzsanna Éhen Marietta Fodor L. Jicsinszky Judit Orgoványi 《Journal of Thermal Analysis and Calorimetry》2006,84(3):693-701
Citronellol
and citronellyl acetate have been entrapped with α-, β- and γ-cyclodextrin
(CD). Evolved gas detection and TG-MS coupling was applied to prove the actual
inclusion complex formation between monoterpens and CDs. The terpene content
was determined by UV-VIS specrophotometry and RP-HPLC and the effect of storage
time on the terpene content was also investigated. The α- and γ-cyclodextrin
inclusion complexes showed higher thermal stabilities vs.
dynamic heating compared to the β-CD complexes. On the contray, the retention
of guest using β-cyclodextrin even after 10 years of storage was much
more pronounced. Experimental data other than 1:1 complex compositions are
assumed. Molecular modeling experiments also suggested multiple complex compositions. 相似文献
2.
H. Aki Y. Nakashima Y. Kawasaki T. Niiya 《Journal of Thermal Analysis and Calorimetry》2006,85(3):685-688
The antibacterial
action of amoxicillin (AMPC) and the inclusion complexes of AMPC with α-, β-
and γ-cyclodextrins (α-CD, β-CD and γ-CD, respectively)
to Escherichia coli B (E.
coli) was evaluated by isothermal titration microcalorimetry and
by petri-dish bioassay method. The effects of the compounds on produced heat
during the exponential phase of the E. coli
growing were measured and the growing rate constants of the cells was calculated
from the power-time (p-t) curve before
and after the treatment with AMPC. Results from the both methods showed that
the antibacterial activity became stronger in the following order: AMPC-βCD
> AMPC-γCD ≈ AMPC-αCD > AMPC only. 相似文献
3.
S. Ponrathnam S. P. Rao S. L. Kapur 《Journal of polymer science. Part A, Polymer chemistry》1978,16(9):2183-2190
Copolymers of methacrylic acid (MAA) and a nonionic hydrophilic monomer N-vinylpyrrolidone (NVP) were synthesized by polymerization in aqueous solution in the absence of metal ions. The NVP content of the copolymers ranged from 2 to 36 mole % with sequences of MAA interrupted at random by a single unit of NVP at all compositions. The pH-induced conformational transition of these copolymers was followed by potentiometric titration and viscosity studies and the results were compared with those of pure poly(methacrylic acid) (PMAA). The negative free energy of transition from the un-ionized compact from to expanded structure showed a gradual decrease with increasing NVP content, and the collapsed conformation observable for PMAA at low degrees of ionization (0 < α < 0.3) disappeared at NVP contents greater than 15 mole%. These findings are supported by viscosity data. The results suggest that long-range methyl–methyl hydrophobic contacts still possible in higher NVP content copolymers are not sufficient to bring about the collapse of the molecule and a minimum average sequence length of about 20 MAA units is required to compact the molecule. Hydrophilic “shielding” of MAA chains by NVP segments could also partly destabilize the collapsed structure. 相似文献
4.
Shengkai Xing Qian Zhang Chong Zhang Qiang Zhao Hongqi Ai Dezhi Sun 《Journal of solution chemistry》2009,38(5):531-543
Thermodynamic parameters for formation of the inclusion complexes of α-, β- and γ-cyclodextrin (α-, β- and γ-CD) with ibuprofen (BF) in Tris-HCl buffer solutions (pH=7.0) have been determined by isothermal titration calorimetry (ITC)
with nanowatt sensitivity, and the inclusion structures have been investigated by using 1H-NMR spectra at 298.15 K. A theoretical study on the inclusion processes between BF and CDs has been performed with the B3LYP/6-31G*//PM3
method in order to investigate the formation mechanism of the inclusion complexes. An analysis of the thermodynamic data indicates
that the stoichiometries of α-, β- and γ-CD with BF are all 1:1 and formation of the inclusion complexes α-CD⋅BF and β-CD⋅BF are driven by enthalpy and entropy, whereas formation of γ-CD⋅BF is an entropy driven process. The 1H-NMR spectra provide clear evidence for the inclusion phenomenon, and show that the isobutyl group and aromatic ring of the
guest molecule are trapped inside the cavity of the CDs. Theoretical calculations suggest that the complex formed by the BF
molecule entering into the cavity of the CD molecule from the wide side is more stable than that from the narrow side. 相似文献
5.
Mariana Voicescu Gabriela Ionita Marilena Vasilescu Aurelia Meghea 《Journal of inclusion phenomena and macrocyclic chemistry》2006,54(3-4):217-219
The action of different molar ratios of α, β, γ-cyclodextrin upon the chemiluminescence of the luminol-H2O2 in alkaline buffer Tris-HCl, pH=8.5 has been evidenced. It was found out that α, β, γ- cyclodextrin have an antioxidant capacity, probably due to the free radicals (that are generate in the system) encapsulation in the their cavity. This behaviour depends on α, β, γ-cyclodextrin molar ratio; α-cyclodextrin and γ-cyclodextrin protects more efficiently against free radicals than β-cyclodextrin. These findings could be very important regarding the oxidative stress process. 相似文献
6.
Zhang G. Z. Kitamura T. Yoshida H. Kawai T. 《Journal of Thermal Analysis and Calorimetry》2002,69(3):939-946
The simultaneous DSC-FTIR was used for the observation of crystallization and melting of poly(vinylidene fluoride) (PVDF)
and its blends with poly(methyl methacrylate) (PMMA) and poly(ethyl methacrylate) (PEMA). The isothermal crystallization was
carried out under the condition of both α-form and γ-form crystallized competitively. The crystal growth rate of α -form and
γ -form were evaluated from the absorbance changes at 795 cm-1 (α -form, CH2 rocking) and 810 cm-1 (γ -form, CH2 rocking) obtained by the DSC-FTIR. The crystal growth rate of γ -form decreased at the same crystallization temperature in
the order of PVDF/syn-PMMA, PVDF/PEMA and PVDF/at-PMMA, which was corresponding to the order of interaction parameter. The mechanism of α -g transition of PVDF in the miscible
blends with at-PMMA, syn-PMMA and PEMA was evaluated from the relationship between the decrease of α -form and the increase of γ -form. The critical
crystallization temperature, at which the transformation from α -form to γ -form proceeded only in the solid state, shifted
to higher temperature side in the order of interaction parameter.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
7.
KEIKO TAKAHASHI HIDEKI YOKOMIZO KATSURO ISHIYAMA MASAHIKO KITSUTA MEGUMI OHASHI 《Journal of inclusion phenomena and macrocyclic chemistry》2006,56(1-2):95-99
Asymmetric reduction of indol-3-pyruvic acid (IPA) with NaBH4 in aqueous solution in the presence of various cyclodextrins (α-, β-, γ-, mono-6-amino-6-deoxy-β- and di-6ABamino-6AB-deoxy-β-cyclodextrin) was investigated. From the NMR and circular dichroism spectral studies, the conformation of the CyD–substrate complexes is suggested; the part of carboxylic group stay in the cavity of α-CyD, whole of IPA in β-CyD, two molecules in a γ-CyD cavity, and IPA(s) is/are on the rim of the cavity of mono-6-amino-6-deoxy-β- and di-6ABamino-6AB-deoxy-β-CyD (AβCyD, DAβCyD) with electrostatic interaction between amino group and carboxylic group. This conformational difference provides in the difference in the optical selectivity of reduction. 相似文献
8.
De-zhi Sun Ling Li Xiao-mei Qiu Min Liu Bao-lin Yin 《Journal of solution chemistry》2006,35(11):1537-1549
Interactions between CDs with three substituted phenols, paeonol (Pae), acetovanillone (Ace) and 2-hydroxyl-5-methoxy-acetophone (Hma), which are isomers, have been determined by isothermal titration calorimetry (ITC) and 1H NMR in aqueous solution at 298.2 K. Both the binding thermodynamics and 1H NMR spectra show that the interaction between α-cyclodextrin (α-CD) molecule and each guest molecule is extremely weak. The thermodynamic parameters indicate that the binding processes of β-cyclodextrin (β-CD) with the isomers are mainly entropy driven and that β-CD binds with Pae or Ace in 1:1 stoichiometry, whereas with Hma binds in 1:1 and 2:1 stoichiometries. The thermodynamic parameters also suggest that γ-cyclodextrin (γ-CD) binds each isomer in the same 1:1 stoichiometry. The binding processes of Pae and Hma with γ-CD are enthalpy driven whereas Ace with γ-CD is predominantly driven by entropy. The 1H NMR spectra reveal that the three isomers were trapped into the torus cavity of the β-CD molecule from the narrow side during the binding process. Pae penetrates into the γ-CD cavity from the primary rim of the macrocycle whereas Ace does so from the secondary rim, but Hma appears not interact with the internal cavity of γ-CD at all. 相似文献
9.
The inclusion complexes of a series of bis-quarternary ammonium surfactants, (C
n
N)2Cl2 (where n = 12, 14, 16) and sodium bis(2-ethylhexyl) sulfosuccinae (AOT), with α-cyclodextrin (α-CD), β-cyclodextrin (β-CD) and γ-cyclodextrin (γ-CD) in aqueous solutions were investigated by using isothermal titration calorimetry (ITC) at 298.15 K. The stability constants,
stoichiometry, and formation enthalpies, entropies and Gibbs energies for the complexes in aqueous solutions have been derived
from the calorimetric data. The values of the binding constant, K
∘
i
, are very large, which indicates that these complexes are quite stable in their aqueous solutions. The enthalpy changes (ΔH
∘) for all of the inclusion processes are negative, showing that the complex process is enthalpy driven. The entropy effect
(TΔS
∘) is negative, so the inclusion process is entropically unfavorable. The large negative Gibbs energy changes indicate that
formation of host-guest inclusion complexes is generally a spontaneous process. The thermodynamic parameters are discussed
in the light of the different structures of the host and guest molecules. 相似文献
10.
Yoon-Ki Joung Hak Soo Choi Tooru Ooya Nobuhiko Yui 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):323-328
We have previously prepared a stimuli-responsive inclusion complex between PEG–b-PEI–g-dextran graft copolymer (PEG–PEI–dex) and γ-cyclodextrin (γ-CD) in order to investigate unique inclusion phenomena, double-axle
inclusion. For further study, a γ-CD derivative, mono-6-O-(2-sulfonato-6-naphthyl)-γ-CD (SN-γ-CD) was additionally synthesized for 1H NMR titration study, which is expected to induce the competition of pendant naphthyl group with external polymer guests.
Consequently, 1H NMR titration results of the inclusion complex of PEG–PEI–dex with SN-γ-CD showed stoichiometric changes, temperature-dependence,
and reversibly pH-responsive properties of the inclusion complexes in terms of chemical shift variation. 相似文献
11.
The comparison of literature data on the dissociation constant of one of the most abundant natural flavonoids, e.g., quercetin,
demonstrates their irreproducibility. The reason for this likely corresponds to the easiness of its oxidation by air oxygen
during the titration process. To eliminate such problems, a modified version of potentiometric titration was proposed with
bubbling a weak flow of an inert gas (nitrogen) through the solution to be titrated in the presence of minimal amounts of
a nonionic surfactant. By virtue of the technique proposed, the values of pK
a for quercetin were measured to be 6.62 ± 0.04 and 9.7 ± 0.3. The first one corresponds to the hydroxyl group in the γ-pyrone
fragment of the molecule, while another agrees with the typical values of pK
a for phenols. 相似文献
12.
A. A. Abdoh M. B. Zughul J. Eric. D. Davies A. A. Badwan 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):503-510
Guest–host interactions were examined for neutral diclofenac (Diclo) and Diclofenac sodium (Diclo sodium) with each of the
cyclodextrin (CD) derivatives: α-CD, β-CD, γ-CD and 2-hydroxypropyl-β-cyclodextrin (HP-β-CD), all in 0.05 M aqueous phosphate
buffer solution adjusted to 0.2 M ionic strength with NaCl at 20 °C, and with β-CD at different pHs and temperatures. The
pH solubility profiles were measured to obtain the acid–base ionization constants (pK
as) for Diclo in the presence and absence of β-CD. Phase solubility diagrams (PSDs) were also measured and analyzed through
rigorous procedures to obtain estimates of the complex formation constants for Diclo/CD and Diclo sodium/CD complexation in
aqueous solutions. The results indicate that both Diclo and Diclo sodium form soluble 1:1 complexes with α-, β-, and HP-β-CD.
In contrast, Diclo forms soluble 1:1 Diclo/γ-CD complexes, while Diclo sodium forms 1:1 and 2:1 Diclo/γ-CD, but the 1:1 complex
saturates at 5.8 mM γ-CD with a solubility product constant (pK
sp = 5.5). Therefore, though overall complex stabilities were found to follow the decreasing order: γ-CD > HP-β-CD > β-CD > α-CD,
some complex precipitation problems may be faced with aqueous formulations of Diclo sodium with γ-CD, where the overall concentration
of the latter exceeds 5.8 mM γ-CD. Both 1H-NMR spectroscopic and molecular mechanical modeling (MM+) studies of Diclo/β-CD indicate the possible formation of soluble isomeric 1:1 complexes in water. 相似文献
13.
Xiu-Kui Qu Lan-Ying Zhu Ling Li Xi-Lian Wei Feng Liu De-Zhi Sun 《Journal of solution chemistry》2007,36(5):643-650
As a continuation of our previous investigation, interactions between cyclodextrin (β-CD), γ-cyclodextrin (γ-CD) and alkyl trimethylammonium bromides in aqueous solutions have been studied with titration calorimetry and 1H NMR at 298.15 K. The results are discussed in terms of the amphiphilic interaction of CD with surfactants and the iceberg
structure formed by water molecules existing around the hydrophobic tail of surfactant molecules. The stoichiometry of the β-CD–surfactant system is 1:1 whereas that of the γ-CD–surfactant system is 1:2. The corresponding formation enthalpy (negative) of the complexes of the two systems decreases
with an increase in the number of carbon atoms (n) in hydrophobic chain of surfactant molecule, C
n
H2n+1, whereas the entropy increases with the enlargement of n. 相似文献
14.
Zusammenfassung Der Verlauf des dielektrischen Verlustfaktors w?hrend γ-Bestrahlung bei verschiedenen Me?temperaturen zwischen 20 °C und 100 °C wurde bei 9,4 GHz an PMMA, MMA-AN und PVC untersucht.
Die Gesamtdosis lag maximal bei 1 · 107 R. Der Verlauf des Verlustfaktors über der γ-Bestrahlungsdosis h?ngt von der umgebenden Atmosph?re — Luft oder Stickstoff — und von der Temperatur der Probe w?hrend der
Bestrahlung ab. Für PMMA und PVC unterscheidet sich das Verhalten des Verlustfaktors unter γ-Bestrahlung stark bei Bestrahlung unter- oder oberhalb der Einfriertemperatur dieser Stoffe. Ein Einflu? der Dosisleistung
auf den Verlauf des Verlustfaktors unter Bestrahlung konnte im untersuchten Bereich nicht festgestellt werden.
Summary For three polymers the dielectric loss factor was measured at 9400 Mc as a function of γ-radiation dose for different temperatures and different surrounding atmospheres of the samples. The maximal dose was 1 · 107 R. For temperatures higher than the glass transition temperature the dependence of the loss factor on γ-radiation was quite different from that at temperatures below the glass transition (PMMA, PVC).相似文献
15.
The stoichiometry, stability, and structure of the inclusion complex between the photosurfactants, 2-[4-(4-alkylphenylazo)
phenoxy]ethyltrimethylammonium bromides (alkyl=ethyl, and butyl, where the abbreviations are EZ and BZ, and ZT for both, respectively),
and γ-cyclodextrins (γ-CDx) in aqueous solution have been studied by the induced circular dichroism (ICD) and UV/VIS spectra
as well as the potentiometric titration method. It is shown that the trans-ZT/γ-CDx systems form not only 1:1 (EZ) or 2:2 (BZ) but also 2:1 (ZT:γ-CDx) inclusion complexes. On the contrary, the steric
hindrance of cis-ZT destabilizes the inclusion so that there is only 1:1 complex formation with γ-CDx. The thermodynamic discussion suggests
that the stability of ZT complex is governed by the hydrophobic and the van der Waals interaction between the photosurfactants
and cyclodextrins. However, the van der Waals interaction is more predominant in the trans-ZT/α-CDx system than in the β- and γ-CDx’s except for (BZ/γ-CDx)2 system. Moreover, the alkylchain-length dependence of the free energy changes of complex formation of ZT and CDx are less
than those of micellization of ZT because the cavity depth of CDx is limited to incorporate all hydrophobic parts of ZT. Finally,
the iso-equibrium temperature is estimated by the compensation plot of thermo-dynamic parameters.
Received: 29 August 1996 Accepted: 13 November 1996 相似文献
16.
Perlovich G. L. Hansen L. K. Bauer-Brandl A. 《Journal of Thermal Analysis and Calorimetry》2001,66(3):699-715
X-ray, DSC and solution calorimetric investigations were carried out for α-, β- and γ-modifications of glycine. Particular
attention was paid to kinetic and thermochemical aspects of γ- → α-phase transition. The temperature of this phase transition
turned out to be sensitive to a) conditions under which the crystals of the γ-modification were grown, b) tempering of crystals
c) form (geometry) of crystals. Kinetics of this phase transition of single crystals of γ-phase in rhomboedric form can be
described by the equation for two-dimension nuclei growth, whereas for crystals of triangle geometry the equation for three
dimension growth is valid. On the basis of energy parameters describing growth of α-form in γ- →α-phase transition, the kind
of structure defects, which are responsible for this phase transition, was estimated. Taking into account the Δsol
H
m, the absolute values of the lattice energies of the investigated polymorphs indescending order are follows: γ->α->β-modification.
The obtained results are discussed with respect to the peculiarity of the crystal lattice structures, particularly the network
of hydrogen bonds. The β-modification of glycine is monotropically related to the other forms, whereas γ-and α-polymorphs
are enantiotropically-related phases.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
A sequence-ordered, periodic copolymer of ethylene, ethylene, and acrylic acid, poly (ethylene-per-ethylene-per-acrylic acid) (PEEA), with M
w=1.44×105 has been synthesized by alternating copolymerization of 1,3-butadiene and methyl acrylate, followed by hydrogenation and
hydrolysis. Aqueous solution and dissociation properties of the alkali-soluble PEEA were explored by potentiometric titration
and intrinsic viscosity at 25 °C. The pH values of PEEA were almost constant (pH = 6.48 ∼ 6.55) with an increasing degree
of dissociation (α) from 0.3 to 0.8 at C
s=50 mN NaCl. Correspondingly, the plots of negative logarithm of apparent dissociation constant (pK
a) against α showed a reversed S-shape curve over the whole α, indicating an extensive precipitation and subsequent tran-sition
from compact to coiled conformation. The intrinsic viscosity steeply increased with α above 0.4 up to 9.97 dl/g at α = 1.0.
Good agreement between the observed electrostatic potential and that calculated from the rod model with a smeared charge density
was observed in the region of α higher than 0.9. The dissociation and dissolution processes of PEEA with neutralization in
water were described.
Received: 14 April 1998 Accepted: 3 June 1998 相似文献
18.
Marzena Jamrógiewicz Kamila Sadowska Jan F. Biernat 《Journal of inclusion phenomena and macrocyclic chemistry》2006,56(3-4):355-362
The effect of β-cyclodextrin on o-ethoxybenzenediazonium salt coupling with pyrrole, imidazole and 2-methylimidazole has been studied. The differences in the
reaction course, the overall yield and products distribution have been analyzed. Experiments without cyclodextrins and selected
reactions with α- and γ-cyclodextrins have been performed for comparison. The results are discussed in terms of co-conformation of azole molecules
embedded in cyclodextrin cavity. 相似文献
19.
Cheng Yang Gaku Fukuhara Asao Nakamura Yumi Origane Tadashi Mori Takehiko Wada Yoshihisa Inoue 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):433-437
The complexation behavior of 6-amino-6-deoxy-γ-cyclodextrin (CD), 6A,6X-diamino-6A,6X-deoxy-γ-CDs and 3A-amino-3A-deoxy-altro-γ-CD with 2-anthracenecarboxylic acid (AC) was studied by NMR, UV–vis and circular dichroism spectroscopy. These modified γ-CD derivatives were found to form stable 1:2 host-guest ternary complexes with AC in aqueous solution. Compared with native
γ-CD, the primary-face-aminated γ-CDs exhibited remarkably enhanced overall association constants as a result of the additional electrostatic interactions
between the oppositely charged host and guest. In contrast, the ternary complex formation of the secondary-face-aminated γ-CD with AC was hindered. 相似文献
20.
J. Báscuas L. García-Río J. R. Leis M. Méndez-Pérez 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):603-606
A kinetic study was carried out on the solvolysis of ortho benzoyl chlorides in the presence of α-, β- and γ-Cyclodextrin (CD). The solvolysis mechanism of benzoyl chlorides is sensitive
to the substituents, and to the solvent in which the reaction takes place. In water, the behaviour exhibited by benzoyl chlorides
which have electron-attracting groups, is consistent with an associative mechanism whilst electron-donating substituents induce
a dissociative mechanism. The results obtained in the presence of CD show a decrease in the observed rate constant, k
obs, as the CD concentration increases. This behaviour can be explained if these substrates undergo solvolysis through a dissociative
path in the presence of α-, β- and γ-CD. 相似文献