Relative Molecular Mass, Mr

The cDNA clone for the neonatal rabbit fast-twitch skeletal muscle Ca -ATPase encodes for 1001 amino acids giving a product with an estimated molecular weight of 110 331 Da [8], The clone for the Ca -ATPase of slow-twitch skeletal muscle sarcoplasmic reticulum (S-Ca -ATPase) encoded for 997 amino acids with a relative molecular mass (Mr) of 109 529 kDa [42],... 

Using regression analysis on a data set of about 50 different molecules, it was found that a. = —4.4,8 = —0.5, Df = 12 cm2/s, and =2.5x 10 5 cm2/s [192], A graphic representation of the effect of relative molecular mass (Mr) and distribution coefficient on corneal permeability is shown in Fig. 13. One observes a rapid reduction in permeability coefficient with decreasing P and increasing Mr. The addition of pores to the model, a mathematical construct, is necessary to account for permeability of polar molecules, such as mannitol and cromolyn. These would also be required for correlating effects of compounds, such as benzalkonium chloride, which may compromise the... 

Disulphonated dyes of relative molecular mass (Mr) about 400-600 that are somewhat sensitive to dyeability differences in the substrate and show the lowest wet fastness of all dye classes used on wool... 

Note The calculation of relative molecular mass, Mr, of organic molecules exceeding 2000 u is significantly influenced by the basis it is performed on. Both the atomic weights of the constituent elements and the natural variations in isotopic abundance contribute to the differences between monoisotopic- and relative atomic mass-based values. In addition, they tend to characteristically differ between major classes of biomolecules. This is primarily because of molar carbon content, e.g., the difference between polypeptides and nucleic acids is about 4 u at Mr = 25,000 u. Considering terrestrial sources alone, variations in the isotopic abundance of carbon lead to differences of about 10-25 ppm in Mr which is significant with respect to mass measurement accuracy in the region up to several 10 u. [41]... 

TableS.7. Relative molecular mass Mr of multiples of atoms and residues...

C. Determining the Relative Molecular Mass, Mr 141 Relaxation times T1 and T2... 

Sedimentation velocity. Tire relative molecular mass Mr can also be measured from observation of the velocity of movement of the boundary (or boundaries for multicomponent systems) between solution and solvent from which the macromolecules have sedi-... 

Here R is in the cgs (cm-gram-second) unit of 8.31 x 107 erg mol-1 deg-1. Using this equation the relative molecular mass Mr, which is numerically the same as M, can be evaluated from the sedimentation constant s. Since s, D, and v must all be measured with care, the method is demanding. It is often necessary to measure s and D at several concentrations and to extrapolate to infinite dilution. It is also customary to correct the data to give the values s°20 w and D°20 w expected at 20°C in pure water at infinite dilution. 

The mass of 1 mole of a compound is called its molar mass. If you write the molar mass of a compound without any units then it is the relative formula mass, often called the relative molecular mass (Mr). So the relative formula mass of water is 18. 

Using a mass spectrometer, the relative molecular mass (Mr) of this organic compound was found to be 56. We need to find out the number of empirical formulae units present ... 

Relative formula mass (RFM) The sum of the relative atomic masses of all those elements shown in the formula of the substance. This is often referred to as the relative molecular mass (Mr). 

Figure 9-8 Diffusion coefficients of organic compounds in LDPE depending on their relative molecular mass, Mr. C-6 to C-24 are hexane to tetracosan 1 undecalactone, 2 phenylethyl alcohol. 3 isoamyl acetate. 4 diphenyl methane, 5 diphenyl ether, A 7-OH to 18-OH are alcohols (heptanol to 1-octadecanol).

In this respect one solution for the estimation of a Dp-value is to correlate the diffusion coefficient with the relative molecular mass, Mr, of the migrant and with matrix specific parameters at a given temperature T in Kelvin. This approach has already been successfully used (Piringer 1993,1994 Limm and Hollifield 1996). The estimation of the diffusion coefficient can be achieved for example using the following heuristic correlation (Piringer 1994 Baner et al. 1996) ... 

Table 15-6 Polyethylene samples with different densities, pP (g/cm3), and additives with relative molecular masses, Mr, and initial concentrations, cR0 (mg/kg).

Figure 2.1. Major physiologically active retinoids. Relative molecular masses (Mr) retinol, 286.5 retinaldehyde, 284.4 retinoic acid, 300.4 13,14-dihydroxy-retinol, 318.5 4-oxoretinol, 301.5 retroretinol, 286.5 14-hydroxy-retroretinol, 302.5 anhydroretinol, 269.6 4-oxo-retinoic acid, 315.4 4-hydroxyretinoic acid, 316.4 dehydroretinol, 284.4 retinyl acetate, 328.5 and retinyl palmitate, 524.9. 

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