Specificity, optical

The specific optical rotations of pure a and p o mannopyranose are +29 3° and -17 0° respectively When either form is dissolved in water mutarotation occurs and the observed rotation of the solution changes until a final rotation of +14 2° is observed Assuming that only a and p pyranose forms are present calculate the percent of each isomer at equilibrium... 

The a-carbon of glutamic acid is chiral. A convenient and effective means to determine the chemical purity of MSG is measurement of its specific rotation. The specific optical rotation of a solution of 10 g MSG in 100 mL of 2 A/HQ is +25.16. Besides L-glutamic acid [56-86-0] D-glutamic acid [6893-26-1] and the racemic mixture, DL-glutamic acid [617-65-2] are known. Unique taste modifying characteristics are possessed only by the L-form. 

Specific optical rotation values, [a], for starch pastes range from 180 to 220° (5), but for pure amylose and amylopectin fractions [a] is 200°. The stmcture of amylose has been estabUshed by use of x-ray diffraction and infrared spectroscopy (23). The latter analysis shows that the proposed stmcture (23) is consistent with the proposed ground-state conformation of the monomer D-glucopyranosyl units. Intramolecular bonding in amylose has also been investigated with nuclear magnetic resonance (nmr) spectroscopy (24). 

One particularly widely used test is the National Bureau of Standards (NBS) smoke chamber test. This provides a measure of the obscuration of visible light by smoke in units of specific optical density. The NBS smoke test can be run in either of two modes ... 

Sucrose, in contrast, is a disaccharide of almost universal appeal and tolerance. Produced by many higher plants and commonly known as table sugar, it is one of the products of photosynthesis and is composed of fructose and glucose. Sucrose has a specific optical rotation, of +66.5°, but an... 

Normal measurements of optical activity are concerned with the ability of the optically active substance to rotate the plane of polarization of plane polarized light, its specific optical rotatory power ( ) being given by... 

A classical, and still most useful, physicochemical parameter for characterizing glycosaminoglycans is their specific optical rotation. For pure heparins from common sources, [a]80 = + 45 to + 53 ° (see Table II). The actual value depends on the relative proportions of monosaccharide constituents (that is, the L-idosyluronic acid residues make a less positive contribution than the n-glucosyluronic residues), and on the degree of sulfation of the preparation (that is, although sulfate groups may have little direct influence on the molecular rotation, they lower the value by acting as diluents ). 

Many enzymes have absolute specificity for a substrate and will not attack the molecules with common structural features. The enzyme aspartase, found in many plants and bacteria, is such an enzyme [57], It catalyzes the formation of L-aspartate by reversible addition of ammonia to the double bond of fumaric acid. Aspartase, however, does not take part in the addition of ammonia to any other unsaturated acid requiring specific optical and geometrical characteristics. At the other end of the spectrum are enzymes which do not have specificity for a given substrate and act on many molecules with similar structural characteristics. A good example is the enzyme chymotrypsin, which catalyzes hydrolysis of many different peptides or polypeptides as well as amides and esters. 

Zirconia nanopowders have attracted much attention recently due to their specific optical and electrical properties [38] and as catalysts [39]. Liang et al. [40] have synthesized pure Zr02 nanopowders via sonochemical method. In this study, the use of ultrasound has dramatically reduced the temperature of reaction and made the reaction conditions very easy to maintain. 

Fig. 26. a Specific optical rotations for the model building blocks for core 78, interior building block 79 and peripheral unit 80 of dendrimers of type 77 b calculated average optical rotations for the doubly branching dendrimers of Oth to 4th generation c measured optical rotations in CHC13 at different temperatures and concentrations [94]... 

M Determined by HPLC analysis using DAICEL CHIRACEL AD-H (hexane/2-propanol 9 1). M Absolute configuration was determined by comparison of the sign of specific optical rotation with the reported one. idl Reaction was carried out at room temperature. t l Reaction was carried out at 0 °C. 

Dissolve 0.500 g in 1 M sodium hydroxide, and dilute to 10.0 mL with the same solvent. The specific optical rotation is —61.0° to —65.0°, calculated with reference to the dried substance. 

Flaming mode, sample thickness unkown, Dm-maximum specific optical density. cAlumina trihydrate. 

SPECIFIC OPTICAL DENSITY 10-2 SPECIFIC OPTICAL DENSITY 10-2... 

The specific optical rotation of bromocriptine mesilate in different solvents is given below for 20° C corrected for loss on drying. A Perkin Eliper polarimeter 241 was used, the actual concentration being 10 mg/ml. 

Specific Optical Density of Smoke Generated by Solid Materials [NIST (NBS) Smoke Chamber], 1993. 

Activity in the field was, however, expanding. For example, in 1927 Drew and Haworth (65) obtaind a crystalline polymeric powder by the action of hydrogen chloride on the lactone of 2,3,4-trimethyl-l-arabonic acid. Citing the increase in melting point and molecular weight, and loss of specific optical rotation, they ascribed a cyclic, high polymer structure to this polyester. 

Achilefu S (2004) Lighting up tumors with receptor-specific optical molecular probes. Technol Cancer Res Treat 3 393—409... 

Determination of specific optical rotation of pharmaceutical substances... 

The two characteristic parameters related to optical activity of the pharmaceutical substances, namely (a) optical rotation, and (b) specific optical rotation, can be measured satisfactorily by the help of a Polarimeter as stated below ... 

DETERMINATION OF SPECIFIC OPTICAL ROTATION OF PHARMACEUTICAL SUBSTANCES... 

The specific optical rotation of a solid substance is usually determined by measuring the angle of rotation at the wavelength of the sodium D-line at a temperature of 20°C, and calculating the result with reference to a layer 1 dm thick of a solution containing 1 g of the substance per ml. It is pertinent to mention here that the specific optical rotation of a solid is always expressed to a given solvent and concentration. 

Procedure Determine the angle of rotation of the freshly prepared 4% w/v solution of adrenaline in 1 M hydrochloric acid with the help of a previously checked polarimeter. The mean value of at least five similar determinations is employed in the calculation of the specific optical rotation. 

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