Cross-Linking with Aldehydes

Gelatin and albumin nanoparticles have been prepared through desolvation of the dissolved macromolecules by either salts (e.g., sodium sulfate or ammonium sulfate) or ethanol [179-182], This is, in principle, similar to a simple coacervation method. The particles can then be insolubilized through cross-linking with an optimum amount of aldehydes. These phase separation methods avoid the use of oils as the external phase. 

Allen (106) also studied cobalt hydroformylation with a polymer-bound catalyst. The polymer was formed from diphenyl-p-styrylphosphine cross-linked with divinylbenzene. 2-Hexene was the substrate, and reaction conditions were 175°C and 1500-3000 psi of 1/1 H2/CO. The product aldehyde was 55% linear, and the effluent product solution contained 20-50 ppm cobalt. 

In a recent report [67], the spirocyclopropyloxy structural motif was incorporated in sulbactam, and the compounds 12a and 12b had good activity against various -lactamases. The mechanism of inhibition of /3-lactamase by 12a or 12b is unique. After the initial acylation, the cyclopropyloxy group can promote the subsequent chemical events to form the aldehyde or the oxycar-benium moiety for further cross-linking with other active site residues of the enzyme (Scheme 5). 

Fig. 5. Relation between the average molecular weight between cross-links, Mc, and the volume fraction of gelatinized collagen (gelatin), v2. The swelling agent is 0.19 mol/1 citric acid - phosphate buffer solution, pH 7.4 at 80 °C. Experimental data obtained after cross-linking with various aldehydes solid circles, formaldehyde open circles, glutaraldehyde squares, glyoxal. The curve is predicted by Eq. (2) with X = 0.52 0.04 [38]...

Amino groups on proteins may be reacted with the bis-aldehyde compound glutaraldehyde to form activated derivatives able to cross-link with other proteins. The reaction mechanism for this modification proceeds by one of several possible routes. In the first option, one of the aldehyde ends can form a Schiff base linkage with e-amines... 

Acetylcholineesterase and choline oxidase A glassy carbon electrode (GCE) modified by electrodepositing sub pm Pt-black particles on the surface. ACh and Ch. micro biosensor arrays were fabricated based on immobilization of AChE—ChO or ChO by cross linking with gentar-aldehyde on Pt-black GCE. Significant enhancement in the performance of these biosensors was achieved. The chronoamperometric response of 1 p biosensor array was linear from 29 to 1200 pM with detection limit of 8.7 pM acetylcholine. [109]... 

Importantly, lipoperoxides can also result in the formation of various aldehydes (malondialdehyde, 4-hydroxynonenal, etc.), which are very reactive and can result in further damage by causing cross-links with proteins and lipids. A single free radical may result in the formation of hundreds of lipoperoxides before it is neutralized. 

Oxidation of some lysine residues to aldehyde derivatives, which cross-link with lysine residues or one another on other strands to solidify the fiber (see here). 

R = H. Ph From polystyryl diphenylphosphine cross linked with 2, S and 20% DVB. - Comparison of olefin formation from aldehydes and ketones using polymeric phosphonium halides with different degree of crosslinking. 

Electrochemistry can be coupled with other physical methods such as fluorescence spectroscopy. An XO-based electrochemiluminescent biosensor for hypoxanthine has been reported. The enzyme was immobilized in a carbon paste electrode with bovine serum albumin cross-linked with glutar-aldehyde. The working principle of the biosensor is illustrated in Scheme 5.6. As already shown (eqn (5.3a)), H2O2 is produced by the catalytic reaction between hypoxanthine and XO immobilized on the electrode surface. In an alkaline or neutral solution, luminol is electrochemically oxidized to a compound that reacts spontaneously with H2O2 to generate chemiluminescent luminol and the ensuing luminescence was used to quantify the amount of hypoxanthine present. 

Poly(vinyl formal) was tried as a consolidant for textiles (Geijer, 1961b Leene, 1963) bnt conld not be redissolved, presnmably because of cross-linking with acid and aldehyde gronps on the degraded textile. 

The enzyme matrix of the Bessman-Schultz sensor is made of thin closely-woven rayon acetate cloth (coated on one side with water-proof pressure-sensitive adhesive) impregnated with a glucose oxidase mixture, dried in air, and cross-linked with glutar-aldehyde. The resultant covalently-bound enzyme is very resistant to degradation by body fluids, showing less than 10 percent decrease in its response to physiological concentrations of glucose after subcutaneous implantation in a rabbit for 11 days and only about 50 percent loss in activity after 6 months. vitro,... 

The reaction of formaldehyde with unsubstituted phenols leads to either soluble or cross-linked resins since condensation occurs at either ortho or para positions. Monosubstituted [35] (ortho or para) phenols give cross-linking with difficulty but phenols doubly substituted in ortho or para positions yield only low molecular weight products. If only one ortho or para position is available on the phenol then the phenol cannot produce resins and reacts with difficulty with aldehydes [33]. Sometimes cresols and phenol are blended together to obtain fully cured resins. In addition to phenol, the other important phenols that are used to give phenolic resins are o-cresol, mixed cresols, / -/e/ r-butylphenol (from isobutylene and phenol), p-phenylphenol (by-product from phenol manufacture), resorcinol, and cardanol (from cashew nutshell liquid). 

A soln. of furfural and p-nitraniline in methanol stirred vigorously 4-5 hrs. in the presence of 20% cation exchange resin of the sulfonated polystyrene type cross-linked with divinylbenzene l-p-nitrophenylpyrrole-2-aldehyde. Y 75%. F. e. s. R. Petit and R. Pallaud, C. r. 258, 230 (1964). 

Following the setup first described by Sinner et Arstad et al ° homopolymerized phosphane-containing monomers with the second-generation Grabbs initiator, cross-linked with p-di(norbom-2-ene-5-yl)benzene and used in the halogenation of alcohols. In a similar approach, an ethyl- l-diazo-2-oxopropylphosphonate-functionalized resin was prepared and used for the conversion of aldehydes into 1-alkynes. Fuchter et also developed a ROMP cap-... 

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