Gluconolactone, formation

Fig. 8.4 (a) In the presence of oxygen, the glucose oxidase-catalyzed oxidation of y -D-glucose leads to the formation of gluconolactone. (b) Carboxypeptidase A selectively cleaves the substrate, hippuryl-L-phenylalanine, thus leading to the formation of hippuric acid and phenylalanine. 

Kramer and coworkers recently reported on water-soluble dendritic coreshell architectures and studied the influence of the attached carbohydrate shell on the formation and stabilization of metal nanoparticles in water. For this purpose, they used hyperbranched poly(ethylenimine) (PEI) as core molecules and covalently attached different carbohydrates as shells, i.e., glycidol, gluconolactone and lactobionic acid, to obtain the corresponding PEI-glycol, PEI-gluconamide and PEI-lactobionamide. Different molecular weights of PEIX (x = 0.8, 5, 21 or 25 with different Mw = xlO3) were employed [81]. 

The resulting radical probably experiences an electron exchange with the oxidized vanadium centers, resulting in the formation of gluconolactone and regenerating the parent V + centers ... 

The reaction of D-gluconolactone 49 with 018-labeled hydroxide ion under stereoelectronic control (which is axial attack) will furnish 50. Note that the crc (, ri bond formed is antiperiplanar not only to an electron pair orbital on the resultant oxy anion, but also to the axial electron pair orbital on the ring oxygen. This reaction is reversible because the crc G n can also cleave very rapidly with the assistance of the same two stereoelectronic effects that facilitated its formation in the first place. Intramolecular proton transfer culminating in the transformation 50 —> 51 is also reversible. The ctc oh bond in 51 cannot cleave because it is antiperiplanar to only one electron pair orbital on the oxy anion [O ]- and, thus, 54 that retains the labeled oxygen will not form. In other words, if the hydrolysis reaction is interrupted (quenched by an aqueous acid) before completion and the unreacted D-gluconolactone is examined for the presence of O18, it will be discovered to be absent. 

Glucose + Benzoquinone — Gluconolactone + Hydroquinone The rate of hydroquinone formation is followed amperometrically. 

Gluconolactone pH control agent, dyeing Formic acid Sodium formate pH control agent, effervescent beverages L-Tartaric acid... 

The results shown in Table 1 indicate that the original premise was reasonable in that the coulombic outputs of glucose and fructose were essentially the same as that resulting when pyruvate or formate was used as substrates. It is interesting to note that the observed coulombic output for gluconolactone was approximately twice that of pyruvate. 

The association of the +AId with active metabolism was further confirmed by experiments in which the glucose substrate was replaced by fructose (as fructose-6-phosphate) and gluconolactone (as 6-phosphogluconolactone) which are intermediates in the glycolytic and pentose phosphate pathways respectively. Pyruvate was also incorporated into this series to determine what effect this intermediate, which precedes the formation of the terminal product of metabolism, namely lactate, would have on the Aid value. It was expected that pyruvate, because of its position in the metabolic scheme, would show either no effect or manifest an adverse effect on the metabolic behavior of the RBC. The adverse... 

---