Modification with glutaraldehyde

Xiao, Z., Xie, Y., Adamopoulos, S., Mai, C. Effects of chemical modification with glutaraldehyde on the weathering performance of Scots pine sapwood. Wood Sci. Technol. 46, 749-767 (2012)... 

Inactivation of photophosphorylation by GA modification seems to be biphasic a first slow phase is followed by a faster phase (Fig. 1). The biphasicity is more apparent if photophosphorylation by the modified thylakoids is assayed under low light intensities. The rate of the fast phase is not affected by the energization state of the miem>brane, but is increased if DTT and Mg " " are present during modification (not shown). The basal rate of electron transport (H2O - FeCN) is not affected by GA modification, but FeCN reduction coupled to ATP formation is inhibited (Table 1), suggesting that modification with glutaraldehyde affects the ATP synthetase. 

FIGURE 3. (Right) Modification with glutaraldehyde Effect on pH supported by ATP hydrolysis. Thylakoids were modified with 0.025% GA for the indicated times. A tCH ] ratio (in/out) O, , rates of Pj -ATP exchange and ATP hydrolysis, respectively. 

In many cases, silicon organic compounds are used as connecting links between a silica surface and a biomolecule. The most popular technique utilizes the modification of a hydroxy-functionalized surface with 3-aminopropyltriethoxysilane (APTES) [2] followed by crosslinking with glutaraldehyde (GA) (Fig. 1 A). 

Zeolite membranes are amenable by surface modification with a variety of chemical functional groups using simple silane chemistry, which may provide alternative surface chemistry pathways for enzyme immobilization. In this context, Shukla et al. [238] have recently used a chemically modified zeolite-clay composite membrane for the immobilization of porcine lipase using glutaraldehyde to provide a chemical linkage between the enzyme and the membrane. The effects of pH, temperature, and solvent on the performance of such biphasic zeohte-membrane reactors have been evaluated in the hydrolysis of olive oil to fatty acids. 

Enzymes have also been immobilized on collagen membrane after its stepwise modification to esters, hydrazides and azides [171]. Another method of enzyme electrode preparation consists of enzyme immobilization on polyacryl acid modified with p-nitroaniline and by a subsequent reduction of N02-groups with titanous chloride and following diazota-tion of resulting aromatic amines [150]. An enzyme electrode has also been prepared by the direct immobilization of an enzyme on the surface of a Pt-electrode which was formerly modified first with 3-aminopropyl triethoxysilane and secondly with glutaraldehyde and bovine serum albumin [172]. Enzymes can also be immobilized on p-benzoquinone-carbon paste[173] or on the graphite electrode after its activation with cyanuric chloride [174]. In a similar way an enzyme electrode has been prepared by using iridium diiodide electrode as a support [175]. 

Amino acid esterases were generated from RNase by using a variety of indole derivatives as modifiers and, perturbing the conformation by titration to an acid pH.23 29 Crosslinking with glutaraldehyde was used to stabilize this new conformation. When assayed with L-tryptophan ethyl ester, the modified RNase was found to possess two pH optima one at 6 and the other at 7.5. Purification of the crude reaction mixture demonstrated the presence of two types of amino acid esterases which account for the two pH optima. After the conformational modification process, the native activity of RNase is lower. After purification of the crude mixture no native RNase activity can be measured in the fractions containing amino acid esterase activity. 

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