Molar Adjustment Factor

The molar adjustment factors (re mannitol) were determined directly, and after metha-nolysis in IN HCl/methanol at 85° for 24 hr and 2N HCl/methanoI at 100° for 24 hr. 

Molar Adjustment Factors of Monosaccharides Commonly Occurring in Glycoproteins and Glycopeptides"... 

Monosaccharide Molar Adjustment Factor (re Arabinitol) Molar Adjustment Factor (re Mannitol) Molar Adjustment Factor (re Penseitol)... 

Figure 3. Graph of mole ratio against total peak area ratio for the determination of molar adjustment factors (a) shows the standard curve for mannose (b) shows the standard curve for iV-acetylglucosamine determined directly ( ) and after methanoly sis for 24 hr in liV HCl/methanol at 85° ( ) and in 2N HCl/methanol at 100° (O).

Total peak area ratio multiplied by molar adjustment factor. 

Terminal sialic acids are released in a good yield under mild acidic conditions like formic acid, pH 2 (1 h, 70 X), 0.1 N H2SO4 or 0.1 N HCl (1 h, 80 "C) (Schauer 1978). These conditions do not lead to N-deacylation however, 0-deacylation occurs to an extent of about 50%. Mild acid hydrolysis has frequently been chosen to release N,0-acylneuraminic acids from biological materials for identification by g.l.c./m.s. Derivatization procedures are presented in sections II. 3 and II.4. For g.l.c./m.s., see section III.2. Quantitative g.l.c. procedures after pertrimethyl-silylation (section II.4) have been worked out by Casals-Stenzel et al (1975). Because of partial 0-deacylation during hydrolysis and subsequent isolation, quantitative analysis of the various N,0-acylneuraminic acids present in native biological material is still a serious problem. The nonavailability of pure N,0-acylneuraminic acids as standard compounds makes it also difficult to determine reliable molar adjustment factors for g.l.c. analysis. 

Remarks 1. The amount of added internal standard depends on the carbo-hydrate-content in the sialoglycoconjugate 2. When too much acetic anhydride is added, the primary hydroxyl functions of mannitol are 0-acetylated giving rise to an additional small peak in the gas chromatogram. The same holds for the primary hydroxyl function of NeuSAc methyl ester methyl glycoside 3. Molar adjustment factors of monosaccharides except NeuSAc are determined by application of the methanolysis procedure on standard mixtures of sugars and internal standard. For NeuSAc the molar adjustment factor is determined using a... 

Table 9.9 (6) gives some guidelines for proper SEC separation conditions when analyzing polymer standards with narrow molar mass distribution on a single 30-cm column. The conditions have to be adjusted when running industrial polymers (which are normally much wider in molar mass distribution). Depending on the width of the MMD, concentrations can be increased by a factor of 3 to 10 for such samples. As a general rule, it is advisable to keep the concentration of the injected solution lower than c [ j] < 0.2. 

For heterocychc libraries in a positional scan format, a key factor is in being able to devise a method for efficiendy carrying out the construction of the library in the positional scan format. For peptide hbraries, the Houghten laboratory was able to employ mixtures of building blocks where the molar ratios had been adjusted to account for reactivity (kinetic rate) differences of incoming building blocks and thereby achieve equimolar mixtures. A non-peptide, two-dimensional positional scan library, identified as an indexed combinatorial library, was reported recently [63], In this work a novel acetyl-... 

The optimum ammonia synthesis reaction rate depends on several factors including pressure, temperature, H2-to-N2 molar ratio, concentration of impurities and catalyst activity. Therefore the H2-to-N2 molar ratio is adjusted to suit the requirements in the ammonia synthesis. This adjustment occurs before the compression step. 

We also observed that the PC chains possess a preferred ability to form inclusion compounds with y-CD in solution, when competing with PMMA and PVAc. From the XH NMR spectrum of the coalesced 1 1 1 PC/PMMA/PVAc blend (not shown), the molar ratio of PC PMMA PVAc was determined to actually be 1.6 1 1.4 compared to the initial molar ratio of 1 24 24, respectively, used in solution to form their common y-CD-IC. Despite the initial 1 24 24 PC PMMA PVAc molar ratio in solution, the PC component in the coalesced PC/PMMA/PVAc blend is still prevalent over the PMMA and PVAc components, which indicates that there may be additional factors that govern the inclusion process from a multiguest system. We believe that this very strong preference of the host y-CD molecules for PC chains, rather than the other two possible guests, is due to their different hydrophobicities. Although the final molar ratio of the coalesced ternary blend can be somewhat controlled by modifying the initial molar ratio of polymers in their common solution, our eventual aim is to be able to adjust, as desired, the constituent polymer ratios in coalesced ternary blends. 

There is no systematic correlation between the preexponential factor Dqi and more direct measures of the size of a penetrant, such as its molar volume at OK. [5] In the absence of such a correlation, and of suitable experimental data for diffusion in PVDC, Dqi was treated as a single adjustable parameter. Equations (1) and (6) were used to fit ln[D(V D,d)] to ln[D(P D,d)], at 298.15K, for the idealized completely amorphous PVDC system. The results of this fit are shown in Figure 6. Unlike D(P D,d), D(V D,d) has the expected slightly convex shape, allowing it to fall off increasingly rapidly with increasing d. 

From a consideration of detailed results on the conformational equilibria of aldopentopyranose derivatives, it has been pointed out92- 9 that a more sophisticated model is required before conformational populations can be reliably predicted, at least with acylated derivatives. Even with adjustment of the original parameters in order to take revised values for the anomeric equilibrium of D-lyxopyranose tetraacetate and the conformational equilibrium of /3-D-arabinopyranose tetraacetate into account, the observed data cannot be accommodated within the framework of this model, except on a very broad, qualitative basis. Other possible factors that should be considered " include polar contributions from substituents other than that on C-1, attractive interactions between syn-diaxial acyloxy groups, non-bonded interactions between atoms that have unshared pairs of electrons,repulsive interactions between gauche-vicinal groups, the effect of solvent pressure, and differences between the molar volume of conformers. 

The qualitative reasoning expressed in Le Chatelier s principle is a helpful guide a system at equilibrium adjusts so as to minimize any stress applied to it. For hydration-dehydration equilibria, the key stress factor is the water concentration. Adding water to a hydration-dehydration equilibrium mixture causes the system to respond by consuming water. More alkene is converted to alcohol, and the position of equilibrium shifts to the right. When we prepare an alcohol from an alkene, we use a reaction medium in which the molar concentration of water is high—dilute sulfuric acid, for example. 

For example, the experimental conditions can be adjusted such that the molecular diffusion is the dominating mechanism (high pressure). This can be experimentally confirmed by the validation of the independence of the steady state flux with respect to the total pressure because the total molar concentration c is proportional to the total pressure while the molecular diffusivity is inversely proportional to pressure (eq. 13.2-12). In this regime, eq. (13.2-12) can be used to determine the tortuosity factor if the binary diffusion coefficient D b is known. 

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