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91.
92.
Network forming properties of various proteins adsorbed at the air/water interface in relation to foam stability 总被引:4,自引:0,他引:4
Martin AH Grolle K Bos MA Cohen Stuart MA van Vliet T 《Journal of colloid and interface science》2002,254(1):175-183
A series of proteins was studied with respect to their ability to form a network at the air/water interface and their suitability as foaming agents and foam stabilizers. Proteins were chosen with a range of structures from flexible to rigid/globular: beta-casein, beta-lactoglobulin, ovalbumin, and (soy) glycinin. Experiments were performed at neutral pH except for glycinin, which was studied at both pH 3 and pH 6.7. The adsorption process was followed with an automated drop tensiometer (ADT). Network forming properties were assessed in terms of surface dilational modulus (determined with the ADT), the critical falling film length (L(still)) and flow rate (Q(still)) below which a stagnant film exists (as measured with the overflowing cylinder technique), and the fracture stress and fracture strain measured in surface shear. It was found that glycinin (pH 3) can form an interfacial gel in a very short time, whereas beta-casein has very poor network-forming properties. Hardly any foam could be produced at the chosen conditions with glycinin (pH 6.7) and with ovalbumin, whereas beta-casein, beta-lactoglobulin, and glycinin (pH 3) were good foaming agents. It seems that adsorption and unfolding rate are most important for foam formation. Once the foam is formed, a rigid network might favor stabilizing the foam. 相似文献
93.
Ice structuring proteins - a new name for antifreeze proteins 总被引:1,自引:0,他引:1
Antifreeze proteins (AFPs) have been reported in the academic literature for many years, and are increasingly arousing interest in the technical and popular media, particularly because of their potential applications. However, the term "antifreeze" does not always accurately describe their natural function, or their application in frozen systems, where they do not prevent freezing, but control the size, shape and aggregation of ice crystals. We survey the properties and applications of AFPs and propose a more generally applicable name based on the fact that all AFPs bind to ice and consequently influence crystal growth and interactions: "Ice Structuring Proteins". 相似文献
94.
Immel S Nakagawa T Lindner HJ Lichtenthaler FW 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(18):3366-3371
Periodate oxidation of alpha-cyclodextrin followed by borohydride reduction readily provided an octadeca-hydroxymethyl-substituted 30-crown-12 polyacetal 1, its 30-membered macrocycle being composed of six meso-butanetetrol/glycolaldehyde acetal units, which is, consequently, optically inactive. Its solid-state molecular geometry emerged from the X-ray structural analysis of the well-crystallizing octadeca-acetate 2, which revealed the undulated macrocycle to be molded into three loops with a unique order of succession of the -CHR-CHR-O-CHR-O- units: alternating gauche- and anti-conformations of the meso-butanetetrol portions and consecutive disposition of the glycolaldehyde-acetoxymethyl groups above and below the mean-plane of the macrocycle. In solution, however, as evidenced by 1H- and 13C-NMR spectra, the macrocycle is highly flexible at ambient and higher temperatures, its mobility becoming distinctly restricted only below -20 degrees C. 相似文献
95.
Albrecht Lindner 《Nuclear Physics A》1976,268(2):369-380
We define real functions which form a complete, orthogonal and rotational invariant basis for all problems depending on four directions. Their usefulness is demonstrated for processes of the type . The special case of all four directions in one plane has many applications too, e.g. in two- and three-body problems. 相似文献
96.
From R2POCl [R = (CH3)2N; C6H5] and Ag[SbF6] in polar solvents, extremely hygroscopic donor-acceptor complexes R2POF · SbF5 have been obtained according to equation (1) in ?Inhaltsübersicht”?. The interaction between R2POCl (R = C6H5; CH3) and the Lewis base KP(C6H5)2 proceeds via a complicated redox mechanism (see equat. (2) in ?Inhaltsübersicht”?) yielding diorganophosphinic anhydride, the mixed diorgano-diphenyl-diphosphine, and tetraphenyl-diphosphine. All these reaction products have been identified by IR-spectroscopic, analytic and other chemical methods. 相似文献
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It is shown that s-wave induced reactions with polarized particles can be described much more conveniently in new coordinates. Even with higher partial waves, cross sections can be fitted with less parameters than in conventional expansions. 相似文献