Size-exclusion chromatography molecular mass determination

Molecular exclusion chromatography is based on the inability of large molecules to enter small pores in the stationary phase. Small molecules enter these pores and therefore exhibit longer elution times than large molecules. Molecular exclusion is used for separations based on size and for molecular mass determinations of macromolecules. In affinity chromatography, the stationary phase retains one particular solute in a complex mixture. After all other components have been eluted, the desired species is liberated by a change in conditions. 

Note Ultrafiltration was used to fractionate the DOM prior to fulvic acid isolation, and the size was determined by high-pressure size exclusion chromatography. The middle and large size fractions had molecular weights corresponding to a range of 1260 to 1470 amu (atomic mass units), and those in the small size fraction had molecular weights of about 1000 amu. 

Molecular weights are determined by end-group analysis (Mn), membrane osmometry (Mn), viscometry (Mv), size exclusion chromatography (Mm), light scattering photometry, and sedimentation (Mw). Any molar mass computed by these methods must be evaluated critically, in view of a dependence on methodology. 

The molecular weight of the native enzymes can be determined in a number of ways, even in the presence of protein contaminants, by using sucrose density gradients or size exclusion chromatography. The major granule starch synthase, I, has a mass of 61,000, which is different than the... 

Size exclusion chromatography is the premier polymer characterization method for determining molar mass distributions. In SEC, the separation mechanism is based on molecular hydrodynamic volume. For homopolymers, condensation polymers and strictly alternating copolymers, there is a correspondence between elution volume and molar mass. Thus, chemically similar polymer standards of known molar mass can be used for calibration. However, for SEC of random and block copolymers and branched polymers, no simple correspondence exists between elution volume and molar mass because of the possible compositional heterogeneity of these materials. As a result, molar mass calibration with polymer standards can introduce a considerable amount of error. To address this problem, selective detection techniques have to be combined with SEC separation. 

Size exclusion chromatography (SEC) is normally used for determining molar mass distribution in polymer and oligomer homologeous mixtures. Values for average molecular masses can be obtained. But it is difficult to get these results of specimen with different chemical heterogeneity SEC cannot provide... 

A HE CHARACTERIZATION OF MODERN HIGH-PERFORMANCE POLYMERS is still a challenge for polymer scientists. Copolymers and complex polymer blends play an important role in many applications (i). A fast, reliable, and comprehensive method is needed to succeed in this task. Size-exclusion chromatography (SEC) is a standard method for the determination of molar mass distributions (MMDs) and molecular weights, if... 

Size-exclusion chromatography has been recently applied, with success, to the analysis of biopolymers derived from biomass, as it is used for the determination of molecular mass distributions of polymeric compounds in general, because of its short analysis time, high reproducibility, and accuracy. This application of SEC has permitted the separation and further detection of polymeric and monomeric residues of biopolymers, as well as the estimation of the degree of polymerization and eventual uses of namral products as additives, not only in... 

The molecular mass of the expressed PA-PLAi was estimated to be 110 kDa by SDS-PAGE, and 97.6 kDa by matrix-associated laser desorption/ionization [48]. A value of 97.6 kDa was also obtained from the deduced amino acid sequence of the open reading frame (ORF) [48]. The enzyme purified from bovine testes had an apparent molecular mass of 440 kDa, as determined by size exclusion chromatography [48], suggesting that PA-PLAi exists as a homotetramer of 98 kDa subunits in solution. The molecular mass of bovine brain PA-PLAi, estimated by the same method, was 200 kDa, suggesting that it exists as a homodimer in the brain [48]. 

MOLECULAR MASS DETERMINATION BY MEANS OF SIZE-EXCLUSION CHROMATOGRAPHY ... 

The determination of molecular mass and molecular mass distribution by size-exclusion chromatography is rapid and easy. However, as it is based exclusively on elution volume, this latter must be determined extremely accurately. Elution volume is a function of log(molar mass) and hence even small errors in the determination of Ve have a dramatic effect. For this reason, either a pump which is both reproducible and precise plus thermostatic control of the system should be... 

Williams, K. and Mozdzer, T. Determination of molecular masses of proteins in solution implementation of an HPLC size exclusion chromatography and laser light scattering service in a core laboratory, http //info.med.yale.edu/wmkeck/biophysics/ Presentation 04 01 02 final.pdf (2003). 

The molecular size of the native enzymes determined by using sucrose density gradients, or size-exclusion chromatography showed that the major granule SSI, has a mass of 60 kDa, while the solubilized GBSSII, was about 93 kDa. ... 

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