Glucose crystal structure

Figure 5.9 Models of hexo-kinase in space-filling and wireframe formats, showing the cleft that contains the active site where substrate binding and reaction catalysis occur. At the bottom is an X-ray crystal structure of the enzyme active site, showing the positions of both glucose and ADP as well as a lysine amino acid that acts as a base to deprotonate glucose.

Reagent 7 is easily prepared from commercially available diacetone-D-glucose and trichloro(cyclopentadienyl)titanium35 (Section 1.3.3.3.8.1.). The monomeric structure of reagent 7 was confirmed by an X-ray crystal structure analysis1 7. Complex 9 is obtained36 analogously from (7 .7 )-tartaric acid derived (R,7 )-2,3-CMsopropylidene-l,l,4,4-tetraphenyl-1,2,3,4-butanetetrol. 

Crystal-structure analysis of Taka amylase A gave similar results, in that it showed that it had an extended cleft which could accommodate six, or possibly seven, a-( 1 — 4)-linked glucose units and two oppositely placed acidic amino acids (Asp-206 and Glu-230) which could interact with the bound substrate similarly to Asp-52 and Glu-35 in lysozyme. 

The x-ray crystal structure of glucose oxidase shows that the flavin sits at the bottom of a funnel-shaped pocket with an opening of about 10 A diameter at the surface of the proteinic core and a depth of about 10 A. The ferricinium... 

Figure 2. A contour diagram of the conformational energy of p-cellobiose computed from eqn. (6) holfing constant all variables except < ), v see ref. 5 for details. The rigid glucose residue geometry was taken from ref. 23, and the valence angle p at 04 was chosen as 116 in accordance with the results of pertinent crystal structure determinations. Contours are drawn at 2,4, 6, 8,10,25, and 50 kcal/mol above the absolute minimum located near ( ), v = -20 , -30 higher energy contours are omitted.

In this study, we assume that crystal structures will have the lowest possible total of intra- and inter-molecular potential energy. However, the partitioning of the potential energy between intra- and inter-molecular terms will vary among crystal structures, distorting the glucose residues away from the shape of lowest energy in a way that will reflect more-or-less random... 

From extensive analysis of recombinant proteins, and the crystal structure of A. thaliana protein, detailed reaction mechanisms have been proposed. The ANS reaction likely proceeds via stereospecific hydroxylation of the leucoanthocyanidin (flavan-3,4-cA-diol) at the C-3 to give a flavan-3,3,4-triol, which spontaneously 2,3-dehydrates and isomerizes to 2-flaven-3,4-diol, which then spontaneously isomerizes to a thermodynamically more stable anthocyanidin pseudobase, 3-flaven-2,3-diol (Figure 3.2). The formation of 3-flaven-2,3-diol via the 2-flaven-3,4-diol was previously hypothesized by Heller and Forkmann. The reaction sequence, and the subsequent formation of the anthocyanidin 3-D-glycoside, does not require activity of a separate dehydratase, which was once postulated. Recombinant ANS and uridine diphosphate (UDP)-glucose flavonoid 3-D-glucosyltransferase (F3GT, sometimes... 

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