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931.
Srinivasan K Kayalvizhi K Sivakumar K Stalin T 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,79(1):169-178
The photophysical, electrochemical and photoprototropic behaviors of diphenylamine (DPA) in aqueous β-cyclodextrin (β-CD) solution have been investigated using absorption spectroscopy and cyclic voltammetric techniques. Absorption of the neutral and cationic form of DPA is enhanced due to the formation of a 1:1 complex with β-CD. The formation of this complex has been confirmed by Benesi-Hildebrand plot and docking studies by RasMol tool methods. The solid complex of β-CD with DPA is investigated by FT-IR, XRD and AFM methods. The thermodynamic parameters (ΔG, ΔH and ΔS) of inclusion process are also determined. The pK(a) values of neutral-monocation equilibria have been determined with absorption (conjugate acid-base) titrations. A mechanism is proposed to explain the inclusion process. 相似文献
932.
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934.
In order to expand the applications of plant protein in food formulations, enhancement of its functionalities is meaningful. Herein, the effects of ultrasonic (20 KHz, 400 W, 20 min)-assisted pH shift (pH 10 and 12) treatment on the structure, interfacial behaviors, as well as the emulsifying and foaming properties of perilla protein isolate (PPI) were investigated. Results showed that the solubility of PPI treated by ultrasonic-assisted pH shift (named UPPI-10/12) exceeded 90 %, which was at least 2 and 1.4 times that of untreated PPI and ultrasound-based PPI. Meanwhile, UPPI-10/12 possessed higher foamability (increasing by at least 1.2 times) and good emulsifying stability. Ultrasonic-assisted pH shift treatment decomposed large PPI aggregates into tiny particles, evident from the dynamic light scattering (DLS) and atomic force microscopy results. Besides, this approach induced a decrease in α-helix of PPI and an increase in β-sheet, which might result in the exposure of the hydrophobic group on the structural surface of PPI, thus leading to the increase of surface hydrophobicity. The smaller size and higher hydrophobicity endowed UPPI-10/12 faster adsorption rate, tighter interfacial structure, and higher elastic modulus at the air- and oil–water interfaces, evident from the cryo-SEM and interfacial dilatational rheological results. Thus, the emulsifying and foaming properties could evidently enhance. This study demonstrated that ultrasonic-assisted pH shift technique was a simple approach to effectively improve the functional performance of PPI. 相似文献
935.
936.
937.
Xiao‐Juan Han Zhen‐Qiang Dong Min‐Min Fan Yan Liu Jian‐Hu li Yi‐Fu Wang Qi‐Juan Yuan Bang‐Jing Li Sheng Zhang 《Macromolecular rapid communications》2012,33(12):1055-1060
A novel pH sensitive shape‐memory polymer (SMP) is prepared by cross‐linking the β‐cyclodextrin modified alginate (β‐CD‐Alg) and diethylenetriamine modified alginate (DETA‐Alg): The pH reversible β‐CD‐DETA inclusion complexes serve as a reversible phase, and the cross‐linked alginate chains serve as a fixing phase. It is shown that this material can be processed into temporary shape as we needs at pH 11.5 and recover to its initial shape at pH 7. The recovery ratio and the fixity ratio were 95.7 ± 0.9% and 94.8 ± 1.1%, respectively. Furthermore, this material showed good degradability and biocompatibility. Because the shape transition pH value is quite close to that of our body fluid and this pH triggered shape‐memory effect is convenient and safe to use, this material has a high potential for medical application. 相似文献
938.
《Journal of Coordination Chemistry》2012,65(2):293-304
Abstract Protonation constants and the protonation scheme of 1,4,7-triazacyclononone-1,4-diacetate (NO2A) have been determined by pH potentiometry and 1H NMR techniques; shielding constants valid for the entire pH range have been calculated. It has been pointed out that the most basic site in the molecule is the unsubstituted secondary amino group. The first two protonation steps belong to ring nitrogens, the third and fourth ones to the carboxylates; the last nitrogen is protonated in very acidic solutions only. Stability constants of complexes of NO2A with selected divalent and trivalent metal ions were determined; with them no indication of kinetic inertness was found. In NO2A complexes the relative contribution of the triazacyclononane ring to the log K ML values is greater for soft than for hard metal ions, compared to corresponding values for 1,4,7-triazacyclononane-1,4,7-triacetate. 相似文献
939.
940.
Yury N. Vorobjev 《Journal of computational chemistry》2012,33(8):832-842
An advanced implicit solvent model of water–proton bath for protein simulations at constant pH is presented. The implicit water–proton bath model approximates the potential of mean force of a protein in water solvent in a presence of hydrogen ions. Accurate and fast computational implementation of the implicit water–proton bath model is developed using the continuum electrostatic Poisson equation model for calculation of ionization equilibrium and the corrected MSR6 generalized Born model for calculation of the electrostatic atom–atom interactions and forces. Molecular dynamics (MD) method for protein simulation in the potential of mean force of water–proton bath is developed and tested on three proteins. The model allows to run MD simulations of proteins at constant pH, to calculate pH‐dependent properties and free energies of protein conformations. The obtained results indicate that the developed implicit model of water–proton bath provides an efficient way to study thermodynamics of biomolecular systems as a function of pH, pH‐dependent ionization‐conformation coupling, and proton transfer events. © 2012 Wiley Periodicals, Inc. 相似文献