Bifunctional reagents table

Presumably, a polypeptide ligand modified near the region which binds to the receptor will be inactivated as most of the bifunctional reagents (Table 5.1) are bulky, and on chemical attachment they often neutralize... 

Bis-Pyndoxal Tetraphosphate. A second class of bifunctional reagents, described in 1988, involves two pyridoxal groups linked by phosphates of different lengths (89). As shown in Table 4, the yield of intramolecularly cross-linked hemoglobin increases dramatically with increasing length of the phosphate backbone. It is beheved that the site of reaction of (bis-PL) is between the amino-terminal amino group of one P-chain and the... 

Jakoby and Wilchek, 1977). The table of bifunctional reagents which will be discussed later (Table 5.1) contains numerous useful references. 

The amino group can be activated with bifunctional reagents. A commonly applied procedure is the introduction of an aldehyde function by the bifunctional reagent glutardialdehyde. The activated carrier can be used directly for the covalent bonding of the enzyme as shown in Fig. 7. Table 1 summarizes various examples of enzyme immobilization. 

The conversion of alcohol to the half ester of succinic acid ( hemi-succinate ) introduces a carboxyl group available for conjugation. This method (Table 12.6) has been used for a large number of haptens (Steiner et al., 1969 Den Hollander et al., 1974 Okabayashi et al., 1977). The bifunctional reagent, sebacoyldichloride, converts alcohol to acid chloride which, at pH 8.5, reacts readily with proteins (Bailey and Butler, 1967). 

Wallace and Wofsy (1979) prepared non-cross-reacting haptens (p-aminobenzoyl glutamic acid and p-aminobenzoyl glycine) which, after diazotization can be directly linked to carriers. IgG conjugated with the bifunctional reagent (methyl-4-hydroxybenzimidate) is used (Table 12.12). In the next step, however, an excess of hapten over... 

Table 1 Crosslinking of LHC Il-less oxygen-evolving PS II complexes with bifunctional reagents with different chain lengths...

Alternatively, bifunctional reagents could be used to cross-link the enzymes, which is an auto-immobilization technique, named as cross-linked enzymes (CLEs).This strategy can be considered as a hybrid since the enzyme is also the carrier itself CLEs have been developed in many different variants from enzyme crystals to group of enzyme a ye-gates and for different appHcation purposes (Table 10.1). 

Tetramethyl-D-glucose reaches equilibrium in benzene rapidly through the concerted action of cresol and pyridine as acid-base catalysts (Table 4.3). Bifunctional reagents, like 2-pyridone and benzoic acid, are especially efficient acid-base catalysts in both polar and nonpolar solvents ... 

The /V-ethylpyrazinium 36e and 8-ethylpteridinium salts 40d which show, as we have seen (see Tables I and III), some tendency to undergo a diaddition with monofunctional nucleophiles, are also able to react with 1,3-bifunctional nucleophilic reagents to give cyclization products. Thus, reactions of pyrazinium 36e and pteridinium 40d salts with thioureas afford... 

Under mechanochemical conditions, bifunctional benzil 71 is specifically reduced by NaBU, when used in a 4 1 stoichiometric ratio to quantitatively give racemic benzoin 72 (Scheme 6.26). Such result has never been described in solution reactions of these reagents. Furthermore, both carbonyl groups of 71 were quantitatively reduced to dihydrobenzoin (17/18), if a 2 1 ratio of 71 and NaBU, was applied under the otherwise identical conditions of Table 6.17. This stoichiometric synthesis provides meso-13 and rac-74 in 80% and 20% yields, respectively. This stereoselectivity compares with the reported 100 0 ratio in methanol (2h at 25°C) and the 85 15 ratio of 73/74 in ethanol (overnight). 

With the increasing number of commercially available, extremely pure chiral auxiliaries, thin-layer chromatographic purity control via formation of diastereomers has gained increasing importance. In contrast to direct enantiomer separations, antipode separation via diastereomers usually is not achieved with chiral adsorbents however, enhanced diastereomer selectivity is also noted for asymmetric supports. The type of chiral reagent for formation of the diastereomer depends among other parameters on the structure—mono- or bifunctional—of the compound to be derivatized (see Table 7). 

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