Glucose units for

Briefly summarized, S-1000 shows better resolution in the high dp range, whereas the CL 2B system resolves low dp components better. Due to these differences in separation performance, the degree of polymerization distribution and degree of polymerization average values for the same sample obtained from broad scb— nb/lcb-transformed dextran calibration yielded dp = 29,900 glucose units for the S-1000 system and dp = 21,100 glucose units for the CL 2B system (Fig. 16.18). 

Cycloamyloses are also referred to as eyelodextrins, eycloglucans, or Schardinger dextrins, preceded, in each case, by a Greek letter to denote the number of glucose units (< - for 6, 0- for 7, y- for 8, etc.). 

Several other high inductions have been reported by using crown ethers as catalysts (Scheme 10.8). The Toke group has used a chiral crown 11 (Chart 10.2), which incorporates a glucose unit, for the addition of 2-nitropropane to a chalcone (Scheme 10.8) [38], Several other effective chiral crowns (12-17, Chart 10.2 and Scheme 10.8) are noted [24e,39-42,48b]. An interesting study of the Michael addition under both solvent-free (0% ee) and liquid-liquid conditions (up to 70% ee) was reported by Diez-Barra and co-workers, who also addressed the question of free -OH quats (28, 58% ee) verses O-benzyl quats (30, 46% ee) [43]. 

Ott s value of 6 D-glucose units for /3-dextrin was later used by Freuden-berg as ammunition in defense of his early molecular weights. Although Freudenberg now agrees that -dextrin contains 7 units, it seems most incongruous that he should have placed much faith in the exact value of a number whose companions were obviously incorrect. 

Amylosucrase 173) from Neisseria perflava utilizes sucrose for the synthesis of polysaccharides with properties intermediate between those of glycogen and amylopectin 174). Apparently, there are two enzymes responsible for this synthesis one enzyme converts sucrose into an amylose-type polysaccharide and the other enzyme, which is of the Q-enzyme type, breaks the straight chains to produce highly branched molecules. The resultant branched polysaccharides have about 12 D-glucose units for each nonreducing end unit. 

The degree of polymerization (DP) of the cellulose reported is up to 22 with respect to the glucose unit for the artificial synthesis, while it is of the order of 2000 for the biosynthesis by AX. The crystal structure formed is cellulose 11 (the thermodynamically stable form having the antiparallel chain orientation) for the artificial synthesis, when the crude enzyme is used, or a mixture of cellulose 11 and I (thermodynamically metastable form having the parallel chain orientation), when the purified enzyme is used, while it is purely cellulose I for the biosynthesis. Moreover, the reaction-induced self-assemblies have some differences as will be detailed later. The clarifications of these differences are an important subject left in future. 

Cation (Section 1 2) Positively charged ion Cellobiose (Section 25 14) A disacchande in which two glu cose units are joined by a 3(1 4) linkage Cellobiose is oh tamed by the hydrolysis of cellulose Cellulose (Section 25 15) A polysaccharide in which thou sands of glucose units are joined by 3(1 4) linkages Center of symmetry (Section 7 3) A point in the center of a structure located so that a line drawn from it to any element of the structure when extended an equal distance in the op posite direction encounters an identical element Benzene for example has a center of symmetry Cham reaction (Section 4 17) Reaction mechanism m which a sequence of individual steps repeats itself many times usu ally because a reactive intermediate consumed m one step is regenerated m a subsequent step The halogenation of alkanes is a chain reaction proceeding via free radical intermediates... 

Cyclodextrins are macrocyclic compounds comprised of D-glucose bonded through 1,4-a-linkages and produced enzymatically from starch. The greek letter which proceeds the name indicates the number of glucose units incorporated in the CD (eg, a = 6, /5 = 7, 7 = 8, etc). Cyclodextrins are toroidal shaped molecules with a relatively hydrophobic internal cavity (Fig. 6). The exterior is relatively hydrophilic because of the presence of the primary and secondary hydroxyls. The primary C-6 hydroxyls are free to rotate and can partially block the CD cavity from one end. The mouth of the opposite end of the CD cavity is encircled by the C-2 and C-3 secondary hydroxyls. The restricted conformational freedom and orientation of these secondary hydroxyls is thought to be responsible for the chiral recognition inherent in these molecules (77). 

Cellulose triacetate is obtained by the esterification of cellulose (qv) with acetic anhydride (see Cellulose esters). Commercial triacetate is not quite the precise chemical entity depicted as (1) because acetylation does not quite reach the maximum 3.0 acetyl groups per glucose unit. Secondary cellulose acetate is obtained by hydrolysis of the triacetate to an average degree of substitution (DS) of 2.4 acetyl groups per glucose unit. There is no satisfactory commercial means to acetylate direcdy to the 2.4 acetyl level and obtain a secondary acetate that has the desired solubiUty needed for fiber preparation. 

Amylases are exoen2ymes that attack amylose chains and result in the successive removal of maltose units from the nonreducing end. In the case of amylopectin, the cleaving stops two to three glucose units from the a-1,6-branching points. ( -Amylase [9000-91-3] is used for the production of maltose symps and for adjunct processing in breweries. The most important commercial products are made from barley or soybeans. 

The Jordi glucose-DVB column is a highly polar GPC column used for separating polar compounds. Modified glucose units are bonded to the DVB backbone to yield a hydrophilic surface (Fig. 13.16). 

FIGURE 16.13 Degree of polymerization distribution (m dpD d) for synthesized amylose -type nb/lcb glucans calculated from dextran-calibrated — amylose-converted calibration of S-SOO/S-IOOO dp. = SSI [glucose units]. 

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