Estimation of molecular weight

The polymers dissolve in l,l,l,3,3,3-hexafluoro-2-propanol [920-66-1/, hot phenols, and /V, /V- dim ethyl form am i de [68-12-2] near its boiling point. The excellent solvent resistance notwithstanding, solvents suitable for measurement of intrinsic viscosity, useflil for estimation of molecular weight, are known (13,15). 

ASTM, Standard Test Method for Estimation of Molecular Weight (Relative Molecular Mass) of Petroleum Oils from Viscosity Measurements, ASTM Standard D-2502-92, 1992. 

Estimation of Molecular Weight of Petroleum Oils from Viscosity Measurements... 

Hedrick, JL Smith, AJ, Size and Charge Isomer Separation and Estimation of Molecular Weights of Proteins by Disc Gel Electrophoresis, Archives of Biochemistry and Biophysics 126, 155, 1968. 

Rodbard, D, Estimation of Molecular Weight by Gel Filtration and Gel Electrophoresis I. Mathematical Principles. In Methods of Protein Separation Catsimpoolas, N. ed. Plenum Press New York, 1976 Vol. 2, p 145. 

Figure 4. Estimation of molecular weight by calibration of Superdex 75HR1030. Standard proteins 1, Albumin (66,000 Da) 2, Carbonic Anhidrase (29,000 Da) 3, Cytochrome c (12,400 Da) 4, Aprotinin, (6,500 Da). The line has been drawn using the equation Ig m = 5.01930882 -2.757789171 r = - 0.9965.

Figure 12 were superimposable on those for detector 2. Therefore, when the plot shown in Figure 14 is linear over the range of compositions involved in the sample, then (according to equations (1-4) ) the composition of the sample is the same at each retention volume. If the variation with retention volume is negligible the copolymer can then possibly be treated as is a homopolymer in GPC interpretation. In particular, intrinsic viscosity measurements could then lead to estimates of molecular weight via the universal calibration curve. 

The brownish, oily nonpolar fractions was chromatographed on the same column as was the polar leachate. One distinct peak, labelled peak A, was observed (Figure 4). An additional peak comprised of several smaller peaks was collected and labelled peak B. Estimates of molecular weight suggest that peak A and B are also between 600 and 1000. 

For accurate determination of protein molecular weight, mass spectrometry and LC-MS have largely displaced SDS-PAGE. However, SDS-PAGE will still be used where estimates of molecular weight suffice or where MS instrument time is limited. 

As discussed above, accurate estimation of molecular weights may not be achieved under native conditions due to molecular shape effects. Performing... 

While nonideal interactions can prevent accurate estimates of molecular weight, they may be exploited to achieve a separation if SEC is being used for preparative isolation or to profile a sample. The same techniques used to suppress nonideal interactions (modulating salt levels, adding organic modifiers, and manipulating pH) can be used to enhance these interactions. 

Estimation of molecular weights of protems by gel filtration. Nature 796, 36-39 (1962). 

Estimation of Molecular Weight Distribution of Polyamide Blocks. The molecular weight distribution of the polyamide blocks was estimated by gel permeation chromatography (GPC) using two instruments, model HLC-802R (Toyo Soda Industry Co., Ltd.) and model GPC-2i U (Waters Associates, Inc.). Polystyrene and nylon oligomer were used as standards. 

Peptide toxins. Of all the toxins produced by freshwater cyanobacteria, the peptide toxins of Microcystis aeruginosa have received the most attention. All research on these peptide toxins indicates they are small, possibly cyclic, with molecular weights estimated at 1200 to 2600 (10,11). Recent work has become more definitive in the estimation of molecular weight and amino acid composition. In 1978 Elleman et al. (12) reported that they had isolated and characterized the peptide toxin of an Australian strain Microcystis which was a pentapeptide with a minimum molecular weight of 654. It consisted of equimolar amounts of alanine, tyrosine, methionine, glutamic and 3-methyl aspartic acid and methylamine. 

The technique of gel filtration is widely used in biochemical research. Chapter 3 described the theory and applications of gel filtration to the experimental procedures of desalting, separation and purification of biomolecules, and estimation of molecular weight of biomolecules. In this experiment, gel filtration procedures will be used to study the dynamic binding of small molecules by proteins. Many of the dynamic processes occurring in biological cells and organisms are the result of interactions between molecules. Often these interactions involve one or more smaller molecules binding to a macromolecule (usually a protein or nucleic acid). 

Apolipoprotein B is the major protein component of LDL, and it appears to be an essential component of chylomicrons, VLDL, and LDL. Unlike other apolipoproteins, apoB is insoluble in aqueous buffers after delipidation with organic solvents, and it does not exchange between lipoprotein particles. This may be because of its molecular weight and insolubility it is by far the largest of the apolipoproteins, although, as noted in Section 4.4.1, estimates of molecular weight vary. 

The volume required to elute a globular protein from a gel-filtration column is a monotonically decreasing function of molecular weight. Thus, by comparing the elution behavior of an unknown protein with that of a series of standards of known molecular weight, an estimation of molecular weight can be interpolated (Fig. 4-2). 

The gel-filtration behavior really depends on the effective size, not mass. Therefore, if the protein differs from the standards in density, an incorrect estimate of molecular weight will result. 

It is well known that lignins exhibit an absorption spectrum with a maximum in the near ultraviolet light tailing into the visible region. Thus, both incident and scattered light intensities are attenuated and, without correction, lead to a low estimation of molecular weights. 

Fractionation depends on the differential solubility of macromolecules with different sizes. It has been displaced in many cases by size exclusion chromatography as a means for measuring molecular weight distributions, but it is till often the only practical way of obtaining narrow fractions in sufficient quantities for the study of physical properties of well-characterized specimens. It is also part of the original procedure for the calibration of solution viscosity measurements for estimation of molecular weights. 

Usefulness of partition coefficients derives from the empirical observation (Figure 5-3) that they may be related to the molecular weight of a solute. Although these observations have been analyzed extensively it must be conceded that as yet they cannot be totally accounted theoretically. When a plot such as that in Figure 5-3 is used to make an estimate of molecular weight, it is advisable to use only the linear region of the plot and to include standard proteins which have molecular weights above and below that of the unknown. 

D-Glucosidases Estimates of Molecular Weight and Molecules per Yeast Cell... 

Hi) Molecular Weight. A Waters Associates gel permeation chromatograph fitted with a model 6000A pump, U6K injector and UV, IR and RI detectors was used for the estimation of molecular weights, molecular weight distribution and copolymer composition. Both analytical and preparative gel columns (Polymer Laboratories Ltd) were employed. Analyses were carried out at 25 t in THF and the column sets were calibrated with monodisperse polystyrene standards (Polymer Laboratories Ltd). 

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