Representation of sugars

FIGURE 16.7 Haworth representations of sugar structures, (a) A comparison of the structure offuran with Haworth representations offuranoses. (b) A comparison of the structure of pyran with Haworth representations of pyranoses. (c) Ot-D-Glucopyranose in the Haworth representation (left), in the chair conformation (middle), and as a space-filling model (right). 

Figure 11.3. Representation of sugar units in a carbohydrate chain (a) lUPAC nomenclature (b) CFG nomenclature. (From C E News, August 8, 2005, p. 46.)...

Carbohydrates are polyhydroxy aldehydes and ketones that are commonly known as sugars. A monosaccharide is a carbohydrate composed of one sugar unit and a disaccharide is a carbohydrate composed of two monosaccharide units. An oligosaccharide is composed of 2-10 monosaccharide units a polysaccharide is composed of 10 or more monosaccharide units. An aldose is a carbohydrate that contains an aldehyde unit and a ketose is a carbohydrate that contains a ketone unit. Monosaccharides are categorized by the total number of carbons in the structure triose, tetrose, pentose, hexose, etc. The d and 1 configurations of a monosaccharide are based on the Fischer projection of d-glyceraldehyde. A Fischer projection is an older representation of sugars. 

Haworth form (Section 22.2) The representation of sugars in which they are shown as planar rings with the ring perpendicular to the plane of the paper. 

Fig. 2. A representation of the cellulose chain ia solution, projected against three two-dimensional surfaces. The circles represent the oxygen atoms that link the iadividual glucose residues, and the lines take the place of the sugar residues. This result of a modeling study (39) iadicated a molecule somewhat more...

In solution, most simple sugars and many of their derivatives occur as equilibrium mixtures of tautomers. The presence of a mixture of two anomers of the same ring size may be indicated in the name by the notation a,P-, e.g. a,P-D-gIucose. In formulae, the same situation can be expressed by separating the representation of the ligands at the anomeric centre from the a and P bonds [see examples (a) and (c)], or by use of a wavy line [(b) and (d)] (particularly if hydrogen atoms are omitted). 

Figure 4. Scatchard representation of binding of Ni2+ to pectins in water (A) and in 0.1 M NaN03 (B) at 25°C, with pectins at 2 mequiv. COO-.l-i (V) sugar-beet pectins, (T) citrus pectins.

Figure 17.3 Anatomy of a redox enzyme representation of the X-ray crystallographic structure of Trametes versicolor laccase III (PDB file IKYA) [Bertrand et al., 2002]. The protein is represented in green lines and the Cu atoms are shown as gold spheres. Sugar moieties attached to the surface of the protein are shown in red. A molecule of 2,5-xyhdine that co-crystallized with the protein (shown in stick form in elemental colors) is thought to occupy the broad-specificity hydrophobic binding pocket where organic substrates ate oxidized by the enzyme. Electrons from substrate oxidation are passed to the mononuclear blue Cu center and then to the trinuclear Cu active site where O2 is reduced to H2O. (See color insert.)...

Fig. 10 Two schematic representations of a polaron-like species in DNA. In the top drawing, the base pairs of DNA are represented by the horizontal lines the sugar diphosphate backbone is represented by the vertical lines. The polaronic distortion is enclosed in the box and extends over some number of base pairs. This is shown schematically by drawing the base-pair lines closer together. In the lower figure, a specific potential po-laron is identified, AAGGAA, and the radical cation is presented as being delocalized over this sequence. Movement of the polaron from one AAGGAA sequence to the next requires thermal activation...

Fig.l a Schematic representation of Neomycin-B aiong with the numbering empioyed for the different sugar units, b Seiective 1-D NOE experiments with the ID-DPFGSE NOE puise sequence, corresponding to the inversion of Him, Hp and Hliv (from top to bottom)... 

Fig. 9 Schematic representation of the target conformationally locked aminoglycosides (2-4) and the deoxy derivatives (5, 6). The numbering employed for the different sugar units is indicated for neomycin-B (compound 1)...

Fischer projections provide a fnrther approach to the two-dimensional representations of three-dimensional formulae. They become particularly useful for molecules that contain several chiral centres, and are most frequently encountered in discussions of sugars (see... 

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