Cross-links, covalent

Aggregation of floe for formation of cross-linking Covalent binding... 

The weak supramolecular interactions (H-bonds, coordination or van der Waals interactions, etc.) positioning the molecular components to give the supramolecular architectures are typically several orders of magnitude less robust than the cross-linked covalent bonds formed in a specific polymerization process. Accordingly, the sole solution to overcome these difficulties is to improve the binding (association) efficiency of the molecular components generating supramolecular assemblies. At least in theory, an increased number of interaction moieties and the selection of the... 

HAO from Nitrosomonas europaea is a homotrimer of 64kDa subunits that is located in the periplasm. Each subunit contains eight hemes c, bound by typical CXXCH motifs. The catalytic heme has a third covalent bond to the protein between the 5-meso carbon of the porphyrin and the Ce 1 ring carbon of tyrosine467 from a different subunit, thus providing the cross-link covalent attachment of the three subunits. This heme has a Soret band at 463 nm in the reduced form, and is designated by heme P460. 

Fig. 20 a The polyrotaxane formed by a-CD and PEO with 2,4-dinitro-phenyl end caps, b The figure-of-eight cross-link covalently cross-linked cyclodextrins. c Schematic diagram of the polyrotaxane gel prepared from the sparse polyrotaxane by covalently cross-linking cyclodextrins using cyanuric chloride as crosslinking agent [89]... 

The kinetics of electron transfer reactions between spinach plastocyanin and [Fe(CN)6] ", [Co(phen)3] , and Fe(II) cytochrome c have been studied as a function of ionic strength. Applications of the equations of Van Leeuwen support the proposal of two sites of electron transfer, with [Co(phen)3] binding near residues 42-45 and the interaction of [Fe(CN)6] at a hydrophobic region near the copper ion. Pulse radiolysis has been employed to measure the rates of electron transfer from Ru(II) to Cu(II) in plastocyanins from Anabaena variabilis and Scenedesmus obliquus which have been modified at His-59 by [Ru(NH3)5] . The small intramolecular rates (<0.082 and <0.26 s , respectively) over a donor-acceptor distance of 12 A indicate that electron transfer from the His-59 site to the Cu center is not a preferred pathway. A more favorable route, via the acidic (residues 42-44) patch ( 14 A to Cu), is supported by the rate of >5 x 10 s for the reduction of PCu(II) by unattached [Ru(NH3)5im] . The intramolecular electron transfer from Fe(II) in horse cytochrome c to Cu(II) in French bean plastocyanin ( 12 A from heme edge to Cys-84 S), in a carbodiimide cross-linked covalent complex, proceeds with a rate of 1.05 x 10 s . The presence of the... 

Fig. 26 Left Shape-memory response curve of an elastomer containing 2 mol% of UPy pendant side groups. Right Proposed shape-memory mechanism (states 1—5) involving thennoieveisible H-bonding. Colored side groups represent H-bonding groups in the hot (red) and cold (blue) states darker lines represent the lightly cross-linked covalent netwoik. Adopted with pennissirai liom [144]. Copyright 2(X)7, John Wiley Sons, Inc.

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