Crosslinked with aldehydes

The asymmetrical molecular structure of collagen permits the formation of rigid gels highly rigid structures are obtained at 0.1% concentration by UV irradiation or chemical crosslinking with aldehydes. ... 

In response to the need for a fiber of low flaimnabil ity (LOI of 31) and low toxic gas formation on burning, Kohjin company developed and marketed a vinyon-vinyl (50 50) matrix (polychlal) fiber under the trade names Cordela and Cordelan. The fiber is believed to be formed through grafting of vinyl chloride to polyvinyl alcohol followed by mixing of the resultant copolymer with additional polyvinyl alcohol. The polymer mixture is wet spun, oriented, and crosslinked with aldehydes. The fiber has a kidney-shaped cross section, and no outer skin is evident. The fiber is... 

K. Szablikowski, W. Lange, R. Kiesewetter, and E. Reinhardt. Easily dispersible blends of reversibly crosslinked and uncrosslinked hydrocolloids, with aldehydes as crosslinker (Abmischungen von mit Alde-hyden Reversibel Vemetzten Hydrokolloidmischungen und Unvemet-zten Hydrokolloiden mit Verbesserter Dispergierbarkeit). Patent EP 686666, 1995. 

The carbonyl-reactive group on these crosslinkers is a hydrazide that can form hydrazone bonds with aldehyde residues. To utilize this functional group with carbohydrate-containing molecules, the sugars first must be mildly oxidized to contain aldehyde groups by treatment with sodium periodate. Oxidation with this compound will cleave adjacent carbon-carbon bonds which possess hydroxyl groups, as are abundant in polysaccharide molecules (Chapter 1, Sections 2 and 4.4). 

The crosslinking of polymeric materials by Mannich reaction includes the polycondensation of acetone with oligomeric polyalkyleneamines and aldehydes (see also 480, Chap. IV) and, more relevantly, polyamides (430, Chap. Ill) crosslinked with benzidine and formaldehyde. Macromolecular materials such as cellophane and polyglucosamine (Fig. 183), deriving from natural substances, are also subjected to the reaction. 

In the crosslinking with formaldehyde of proteic macromolecules, such as casein, the polymer behaves at the same time as both substrate and amine reagent.Studies of the reaction between formaldehyde and ettllagen stress the importanee of aldehyde coneentration and pH value in the process. It is found that the number of methylene bridges formed for each collagen molecule (molecular weight about 10,(XK)) is nearly 15 the amino groups of lysine, hydroxylysine, and histidine present in the maeromol-ecule are suitable for the occurrence of the Mannich reaction. -" - ... 

Many other guanosine lesions have been investigated, the majority of which are those derived from polyaromatic hydrocarbons (PAHs), though adducts with smaller reactive species are also reported. Reaction with aldehydes, such as acrolein and crotonaldehyde leads to the formation of propano-dG adducts such as (86) and its a- and y-hydroxy derivatives as well as ring-opened derivatives like (87). Derivatives (87) can further react with other nucleobases, particularly guanine, leading to crosslinking. The reaction with aldehydes is... 

It is worth emphasising the ease of the reaction of amines and amides with aldehydes, since it explains the need to use purified solvents when dealing with amino acids, peptides and proteins, to avoid such side-reactions. Glutaraldehyde has been used for crosslinking proteins (from the earliest days in the leather industry, too) but it is toxic and therefore less in favour in laboratory work now. 

Chlorinated and/or oxidized starches crosslinked with glyoxal were used to produce a high-strength size for paper.573 Coating adhesives were also prepared by crosslinking glycidyl esters.1385 In addition, esters of starch with inorganic acids (such as starch phosphates) were crosslinked with various aliphatic and aromatic aldehydes in the presence of urea, melamine and similar compounds.1322... 

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