Cross-linking intermolecular

Formaldehyde fixes proteins in tissue by reacting with basic amino acids— such as lysine,5 7—to form methylol adducts. These adducts can form crosslinks through Schiff base formation. Both intra- and intermolecular cross-links are formed,8 which may destroy enzymatic activity and often immunoreactiv-ity. These formaldehyde-induced modifications reduce protein extraction efficiency and may also lead to the misidentification of proteins during proteomic analysis. 

FORMATION OF INTRA- AND INTERMOLECULAR CROSS-LINKS IN FORMALIN-TREATED RNASE A... 

Fraenkel-Conrat H, Mecham DK. The reaction of formaldehyde with proteins demonstration of intermolecular cross-linking by means of osmotic pressure measurements. J. Biol. Chem. 1949 177 477-486. 

In either dilute or concentrated solutions, additional reactions occur that result in both intra- and intermolecular cross-linking of proteins. There is little direct chemical information from such techniques as nuclear magnetic resonance spectroscopy or mass spectrometry to detail the precise nature of these cross-links.5,6... 

Incubation of proteins in aqueous media at elevated temperatures significantly reduces the number of methylol adducts and intermolecular cross-links. Increasing pressure not only seems to accentuate this process significantly, but also appears to be accompanied by protein cleavage at aspartate residues.13... 

Jennings, M.L., and Nicknish, J.S. (1985) Localization of a site of intermolecular cross-linking in human red blood cell band 3 protein./. Biol. Chem. 260, 5472-5479. 

There is recent evidence that stabilization to elevated temperatures (over 350°C) yields a structure with additional intermolecular cross-linking that results in improved mechanical properties in carbonized fibers [10,11], In addition, it has been noted that the addition of ammonia to the stabilizing environment accelerates stabilization [12],... 

The hypothesis can be checked by the mathematical experiment, if one takes into consideration the probability of the intemolecular cross-linking. Let s assume that sol fraction contains only intramolecularly cross-linked chains while the formation of even one intermole-cular cross-linkage leads to the sol-gel transition. Because only the properties of sol fraction are of our interest we don t need to follow the intermolecularly cross-linked chains. It is rather natural to assume that the probability of the transition into the gel is proportional to the dimensions of the macromolecular coil. 

The coefficient "c" has an analogy with a concentration, as more is "c" more coiled conformation can be intermolecularly cross-linked. 

To answer this question, information obtained from studies of irreversible systems needs to be examined. Irreversible protein processes may occur as a result of intermolecular interactions (i.e., aggregation, chemical modification, intermolecular cross-linking). Although an attempt is generally made to search for conditions that provide maximal reversibility, perhaps by altering the solution conditions (i.e., pH, salt content, lowering the protein concentration) that minimize contact and electrostatic interactions, many systems can still exhibit little or no reversibility. This would be the case for the core protein obtained by limited... 

Figure 12 (a) Lysyl oxidation reaction, (b) cofactor of lysyl oxidase, lysyl tyrosine quinone (LTQ), and (c) an example of the intermolecular cross-link, histidinyl glucosylgalactosyl hydroxylysinorleucine. 

Kuboki Y, Tsuzaki M, Sasaki S, Liu CF and Mechanic GL (1981) Location of the intermolecular cross-links in bovine dentine collagen, solubilization with trypsin and isolation of cross-link peptides containing dihydroxylysinonorleucine and pyridinoline. Biochem Biophys Res Comm 102, 119-126. 

Mechanic, G. Stable intermolecular cross-links in collagen after reduction. In Chemistry and molecular biology of the intercellular matrix, Vol. 1, pp. 305. Balazs, E. A. (ed.). London, New York Academic Press 1970... 

The total number of cross-links per gram is directly proportional to radiation dose. Either RSMW or JRg(Mw)2/3 should be independent of initial molecular weight, depending on whether all repeating units or only those near the surface of the coils have equal probabilities for intermolecular cross-link formation. Complete coil collapse is clearly ruled out by the results. Moreover, detailed calculations (46) show that a trend in the product RgMw due to systematic differences in intramolecular cross-linking, should be observed even for only partially collapsed random coils. If the coil radii in bulk polystyrene were reduced by even as much... 

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