Chemical cross-linking and

No polymer is ever 100% crystalline at best, patches of crystallinity are present in an otherwise amorphous matrix. In some ways, the presence of these domains of crystallinity is equivalent to cross-links, since different chains loop in and out of the same crystal. Although there are similarities in the mechanical behavior of chemically cross-linked and partially crystalline polymers, a significant difference is that the former are irreversibly bonded while the latter are reversible through changes of temperature. Materials in which chemical cross-linking is responsible for the mechanical properties are called thermosetting those in which this kind of physical cross-linking operates, thermoplastic. 

Networks with tri- and tetra-functional cross-links produced by end-linking of short strands give moduli which are more in accord with the new theory if quantitative reaction can be assumed (3...13) However, the data on polydimethylsiloxane networks, may equally well be analyzed in terms of modulus contributions from chemical cross-links and chain entangling, both, if imperfect reaction is taken into account (J 4). Absence of a modulus contribution from chain entangling has therefore not been demonstrated by end-linked networks. 

Sinz A. Chemical cross-linking and mass spectrometry to map three-dimensional protein structures and protein-protein interactions. Mass. Spectrom. Rev. 25 663-682. 

Back, J.W. et al. (2003) Chemical cross-linking and mass spectrometry for protein structural modeling. J. Mol. Biol. 331, 303-313. 

Dihazi, G.H., and Sinz, A. (2003) Mapping low-resolution three-dimensional protein structures using chemical cross-linking and Fourier transform ion-cyclotron resonance mass spectrometry. Rapid Comm. Mass Spectrom. 17, 2005-2014. 

Jacobsen, R.B., Sale, K.L., Ayson, M.J., Novak, P., Hong, J., Lane, P., Wood, N.L., Kruppa, G.H., Young, M.M., and Schoeniger, J.S. (2006) Structure and dynamics of dark-state bovine rhodopsin revealed by chemical cross-linking and high-resolution mass spectrometry. Protein Sci. 15, 1303-1317. 

Kalkhof, S. et al. (2005a) Chemical cross-linking and high-performance fourier transform ion cyclotron resonance mass spectrometry for protein interaction analysis Application to a calmodulin/target peptide complex. Anal. Chem. 77, 495-503. 

Ledoux, D.N., Be, X.H. and Singh, B.R., Quaternary structure of botulinum and tetanus neurotoxins as probed by chemical cross-linking and native gel electrophoresis, Toxicon, 32, 1095-1104, 1994. 

Enhanced Utility of Polysaccharidases through Chemical Cross-Linking and Immobilization... 

In some situations, crystalline formation can occur because of addition of physical stress such as the stretching of a rubber band. As the rubber band is stretched, the amorphous random chains become aligned, forming small areas that are crystalline and oppose further stretching. Thus, rubber bands contain chemical cross-links and form crystalline domains on extension (Figure 2.22). 

A cross-linked polyolefin foam sheet is produced by two methods using chemical cross-linking and by two methods of radiation cross-linking. The two well-established manufacturing processes for polyolefin foams using radiation cross-linking are the Sekisui process and Toray process. The differences between these two manufacturing methods are mainly in the expansion step, which is almost always done separately. However, the... 

Application of enzymes for protein cross-linking is an alternative to chemical cross-linking and also they are safe to be used in food production and their activity does not change while thermal processing (baking, pasteurization, etc.). 

Both agarose and polyacrylamide gels are solid but porous matrices, which look and feel like clear jelly (Jell-0). These gels are prepared in different ways but both take the form of a slab (or alternatively column), cast like a jelly in a mould. While agarose gels are relatively easy to prepare, polyacrylamide gels are formed by complex polymerization and chemical cross-linking, and as such are usually purchased pre-cast. 

An ideal matrix for gel filtration should consist of partides of a hydrophilic polymer, that is as inert as possible, as rigid as possible, uncharged, and of uniform size (Patel 1993). Suitable materials are naturally occurring polymers, such as agarose or dextran, which have been stabilised by chemical cross linking, and also synthetic polymers such as polyacrylamide. These materials are available as spherical partides of different diameter (10-500 pm) and pore sizes the pore size determines the range of optimal molecular weight separation (Table 4-1). 

Plastic materials are sometimes termed resins . These can be synthetic or natural. Copals are natural resins, some of which can turn into amber, given enough time. This happens by an evaporation of some of the chemicals, while other chemicals cross-link and polymerise. 

A. Sinz, Chemical Cross-Linking and Mass Spectrometry for Investigation of Protein-Protein Interactions. In Mass Spectrometry of Protein Interactions K. M. Downward, Ed. Wiley-lnterscience Hoboken, NJ, 2007 pp 83-107. 

Natural rubber (polyisoprene, PI) mixed with 1.8 PHR DCP for chemical cross-linking and 15 PHR carbon black N660 (Degussa AG, Hiirth, Germany) with a primary particle diameter of 67 nm [142] is microtomed at low temperatures to provide 10 pm thin slices with smooth sample surfaces. These slices are mounted on metallic sample holder discs using pressure sensitive adhesive. 

B. X. Huang, H.-Y. Kim and C. Dass, Probing three-dimensional structure of bovine serum albumin by chemical cross-linking and mass spectrometry, J. Am. Soc. Mass. Spectrom., 15(8) 1237-1247 (2004). 

V. Rossi, C. Gaboriaud, M. Lacroix, J. Ulrich, J. C. Fontecilla-Camps, J. Gagnon, G. J. Arlaud. Structure of the catalytic region of human complement protease Cls study by chemical cross-linking and three-dimensional homology modeling. Biochemistry. 1995, 34, 7311-7321. 

Cumulative action of chemical cross-linking and catalytic dehydration presents arise a necessary and sufficient condition of carbonization, which is observed in the process of thermal-oxidative degradation of PE-MMT nanocomposites. 

The exact nature of the tanning reaction is not known and a number of mechanisms have been proposed. It has been shown, however, that as the process progresses, the degree of unsaturation of the oil reduces, peroxy-derivatives are formed, hydroxyl functions appear and, more specifically, acrolein, CH2=CH CHO, is produced. It is thought that this and other aldehyde compounds are responsible for the chemical cross-linking and that coating the fibres with polymerised oils imparts the special physical characteristics to the leather. 

In reconstituted discoidal HDL, the apolipoproteins form a protective shell, one-helix thick, around the periphery of the discs. The organization of apo Al molecules in such particles has been studied extensively using various spectroscopic techniques, as well as chemical cross-linking and mass spectrometry methods [21,22], There is general agreement that the a-helices of apo Al are aligned perpendicular to the PL acyl chains (Fig. 6A). The precise registry of the apolipoprotein helices is dependent upon the size of the disc, and various models to account for this effect have been proposed [21,22]. The nascent HDL particles created by ABCAl-mediated efflux of cellular PL and cholesterol to apo Al are discoidal with structures like those depicted in Fig. 6B (M.C. Phillips, 2(X)6). 

Thomas, M.J., Bhat, S., Sorci-Thomas, M.G. 2006. The use of chemical cross-linking and mass spectrometry to elucidate the tertiary conformation of lipid-bound apolipoprotein A-I. Curr. Opin. Lipidol. 17 214-220. 

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