Crosslinking with formaldehyde

Plastics and fibers have been produced from regenerated proteins obtained from a number of sources [17]. The process involves dispersing the proteins in dilute sodium hydroxide followed by extrusion through a spinneret into an acid bath to form the fibers that are then crosslinked with formaldehyde to improve strength. The fibers are used along with silk and wool. 

Heat treatment, on the other hand, elevated cytoplasmic immunoreactivity of Bcl-2. However, nuclear and mitotic Bcl-2 immunoreactivity was clearly present when these cells were fixed with formaldehyde (3.6%), followed by postfixation with methanol for 10 min at -20°C. Treatment with ice-cold methanol makes the cell membrane permeable, allowing antibody access to intranuclear antigens without protein relocalization. Extensive protein crosslinking with formaldehyde is required for maintenance of intranuclear Bcl-2 immunoreactivity. In contrast to Bcl-2, Bax immunoreactivity was detected in nuclear and cytoplasmic compartments regardless of the duration of formaldehyde fixation used. 

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. -" - ... 

An example of the first application is shown in Figure 2, which shows release of the highly water-insoluble hydrocortisone acetate from a gelatin matrix crosslinked with formaldehyde (J ). As indicated by the first-order dependence, drug is released by a simple diffusional process and the crosslinked gelatin simply provides cohesiveness for the drug particles. 

Modification of carbamoylated and carbaminated starches by oxidation and crosslinking with formaldehyde was reported.2623 Crosslinking was used to produce fire-resistant construction boards.1360 A size for cellulose fabrics was produced by crosslinking poly(carbamoylethyl)ethers of starch with formaldehyde.1351... 

The time and temperature of crosslinking with formaldehyde should be optimized for a given cell line and type. For example, between 5 and 60 min at either room temperature or on ice. 

Casein CS -NH-CO- (polypeptide from milk albumin crosslinked with formaldehyde) ... 

Crosslinking with formaldehyde Catalyst, 2 % zinc chloride in wood, then exposed to para-formaldehyde heated to 120°C for 20 min ASE 85 % (4 % weight increase) drastic loss in toughness and abrasion resistance None... 

For decades, rayon has been crosslinked with formaldehyde to improve the poor crimp resistance in the dry state and the dimensional stability in the wet state. Under the pressure of synthetic fiber competition, an effort has been made to produce non-iron cotton fabric. In this high-grade finishing, a distinction is made between treatment with aldehydes, aminoplast precondensates, reactant resins, as they are called, and with nitrogen-free cellulose cross-linking agents. 

In addition, caseinate-based films were crosslinked with formaldehyde (HCHO). The occurrence of covalent bridges between protein chains allows water-insoluble three-dimensional network to be achieved. The crossHnking was combined with plasticizing to produce caseinate films with improved mechanical properties and water resistance which are able to replace synthetic films and to overcome protein film deficiencies. Nevertheless, in spite of crosslinked protein material being water insoluble, it was also shown that during water immersion, plasticizer exuded out of the film, even for highly crosslinked samples. 

Fig. 3. Stress-strain properties of 50% w/w TEA plasticized NaCAS films crosslinked with formaldehyde (HCHO/e-NHj molar ratios reported on each curve) at 53% RH.

Treatment with GTA is a commercially viable process, its efficiency has been optimized, it is inexpensive and completed in a relatively short period and provides more sustained long-term durability than crosslinking with formaldehyde [59,55],... 

The organometallic polymer shown in scheme 3 was synthesized using phosphoric acid, persulfate, or azobisisobutyronitrile (AIBN) as catalyst. Copolymers prepared with methyl methacrylate, styrene, and chloroprene as well as the homopolymer were crosslinked with formaldehyde. These polymers rmderwent reversible chemical oxidation with ceric sulfate. 

Figure 3. Time-resolved extraction of benzene and cyclohexane into isooctane from a freeze-dried PVA-AgNOs membrane (7% Ag by mass, crosslinked with formaldehyde). The membrane thickness was approximately 350 fim.

Hartsuch descrit d modifications through wool s -NH2 groups and -S-S-linkages by crosslinking with formaldehyde (Eq. 1) or benzoquinione, by the addition of an amino group to a ketone (5) The reduction of disulfide bonds with thioglycolic acid and the subsequent formation of new crosslinks between two adjacent chains by dihalogen compounds (Eq. 2,3) is shown below ... 

Some applications of proteins demand a high water resistance. One way to increase the water resistance is to cross-link the protein chains. Dialdehyde crosslinking specifically reacts on free amine functions, while not specific crosslinkers as a formaldehyde resin, reacts both with carboxyl, amine and hydroxyl groups [214]. By crosslinking with formaldehyde, the water sensitivity of protein plastics can be dramatically reduced, particularly at high relative humidity levels [215]. Glutaraldehyde has been shown to be very reactive toward the N-terminal amino groups of peptides as... 

Carboxymethyl hydroxyethyl cellulose Casein, crosslinked with formaldehyde c s c s C S c s CMHEC... 

Recently an NMR study of the proton spin-lattice relaxation as a function of temperature in a series of new proton conducting gel electrolytes was performed based on agar containing acetic acid plasticized with glycerol and crosslinked with formaldehyde. The temperature dependence of the H spin-lattice relaxation showed a well-defined rate maximum whose position depends on the acetic acid concentration. The NMR relaxation curve was similar to those observed in the gelatin-based gel electrolyte, reflecting the high proton mobility in these gel electrolytes. 

Temperature dependence of the H spin-lattice relaxation rates (1/ 7i) in the gel electrolytes measured at the Larmor frequency of 36 MHz ( ) gelatin network and (O) agar network. The electrolytes are formed by the network and acetic acid, plasticized with glycerol and crosslinked with formaldehyde. 

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