Maltose optical rotation

The specific rotation of maltose in water is +138°. What would be the concentration of a maltose solution that had an optical rotation of +23° if a polarimeter tube 10 cm long was used ... 

Maltose behaves as a normal reducing sugar, showing mutarotation and existing finally in aqueous solution as an equilibrated mixture of the a-form and the S-form Modern ideas about connections between optical rotation and structure are reported in the literature [105]. 

Changes in optical rotation have been popular with those investigating glycoside hydrolysis since Wilhemy in 1850, using the newly invented polarimeter, demonstrated that hydrolysis of glycosides follows the first-order rate equation, k = 1/t log a/(a — x). Rate constants were then ob-tmned for the acid-catalyzed hydrolysis of salicin, - starch, maltose, lactose, methyl a- and /9-n-glucopyranoside, methyl a- and /S-n-galacto-pyranoside, - sucrose, and raffinose. ... 

Later, Machell and Richards and Whistler and BeMiller isolated the compound as a sirup (in yields of about 1%) by treatment of maltose with 0.05 N sodium hydroxide and of cellobiose with 0.05 N potassium hydroxide. There was a divergence in the reported specific optical rotations (in water), namely, —24.1° and -fll°, respectively, which might be attributable to degradation of this labile compound during isolation or storage. The crystalline (2,4-dinitrophenyl)osazone prepared in both investigations was further characterized as its crystalline triacetate. ... 

A more careful examination of the products of action of pullulanase on pullulan showed the presence of a tetrasaccharide, in addition to maltotriose. In the sample examined, the tetrasaccharide was estimated to constitute 7% of the polysaccharide. The complete hydrolysis of this tetrasaccharide to maltose by sweet-potato befo-amylase, as well as optical rotation measurements, characterized it as maltotetraose. As earlier work had suggested that pullulan is a linear molecule, it was, therefore, of interest to ascertain how the maltotetraose units are arranged in the molecule. The two most likely possibilities are illustrated in Fig. 16b,c. 

Figure 1,2. Reversal of maltose hydrolysis catalysed by an extract of dried yeast. The extract, prepared as described in the text, was mixed with solutions of glucose and maltose as described in Table 1.4. At various times (see dates) the amounts of maltose and glucose were estimated from the reducing power and the optical rotation of the solutions. For each experiment (see Table 1.4) the results are plotted as the percentage of the total carbohydrate present as glucose and maltose. (From Hill, 1898 reproduced with the kind permission of the Royal Society of Chemistry from the original paper, (Fig. 5, p. 652).)...

The variations in the optical rotations of aqueous solutions of D-glucose, sucrose, and maltose, etc., on addition of calcium chloride have been investigated. Measurement of the Cotton effects induced by the addition of germanic acid to aqueous solutions of D-fructose in the pH range 6—10 indicated that a... 

This can be analysed by optical rotation, with some rather interesting results. The sugars that were studied a few years ago were OL -methyl-maltoside, cellobiose and trehalose. They have one factor in common, they are composed of two glucose units, but with different linkages, maltose a-1-4, cellobiose B- 1-4, and trehalose 01-1-1. There are thus different conformations of this molecule, which consists of the same two sugar units. 

It is possible to estimate how much of the measured optical rotation is in fact associated with the glycosidic linkage (Rees and Thom, 1977). Knowing the optical rotations of the two monomers, and of the molecule in the crystal state, then measurement of the optical rotation in solution makes it possible to calculate how much of that is due to the two angles and what is likely to be the configuration of the molecule in solution. The results are shown in Table 1. A Monte Carlo simulation in vacuo predicts a value of -28 for maltose and a-methyl-maltoside. This is very close to the experimental values in dimethyl sulphoxide and dioxan. For aqueous solutions there is absolutely no correspondence with the calculated value. The rotation is even of the opposite sign. 

Endo-amylase (a-amylase) has a liquefying effect, since the viscosity of a colloidal starch solution decreases rapidly and the iodine color reaction disappears without the appearance of reducing sugars. The reducing effect develops later, in a second phase, when the fragments have been broken down further. Maltose is released in the a-form (the optical rotation drops, however, due to muta-rotation) hence the name of the enzyme. 

The determination of sugars by polarimetry is carried out preferably with analytically pure derivatives in higher concentration. Mono-, di-, and smaller oligosaccharides are optically active as a result of the presence of their chiral centers and rotate the plane of the polarized light. The highly specific rotation of disaccharides is dependent not only on the wavelength of the light and temperature, but also to a small extent on the concentration as shown by two common examples of simple disaccharides such as maltose and sucrose. 

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