Size-exclusion chromatography , optically

A. W. Moore, Jr and J. W. Jorgenson, Comprehensive three-dimensional separation of peptides using size exclusion chromatography/reversed phase liquid chromatography/ optically gated capillary zone electrophoresis . Anal. Chem. 67 3456-3463 (1995). 

The conformational mobility of a chromophoric main-chain polymer is often connected to its electronic structure. Therefore, changes in the UV-visible absorption spectra and/or chiroptical properties are spectroscopically observable as thermo-, solvato-, piezo-, or electrochromisms. It is widely reported that o-conjugating polysilanes exhibit these phenomena remarkably clearly.34 However, their structural origins were controversial until recently, since limited information was available on the correlation between the conformational properties of the main chain, electronic state, and (chir)optical characteristics. In 1996, we reported that in various polysilanes in tetrahydrofuran (THF) at 30°C, the main-chain peak intensity per silicon repeat unit, e (Si repeat unit)-1 dm3 cm-1, increases exponentially as the viscosity index, a, increases.41 Although conventional viscometric measurements often requires a wide range of low-dispersity molecular-weight polymer samples, a size exclusion chromatography (SEC) machine equipped with a viscometric detector can afford... 

DSC differential scanning calorimetry SEC size exclusion chromatography POM polarized optical microscopy... 

Figure 5 Fucosylation of the EPS from Lb. delbrueddi bulgaricus Lb291. Size exclusion chromatography of the reaction mixture containing EPS, GDP-fiicose, GDP- [ C]-fucose, MnCl2 and purified a-(l,2)-fucosyltransferase from H. pylori. Level of radioactivity (cpm) has been determined by using a scintillation counter. The optical density was detected at 280 nm.

The method of choice for the determination of these quantities on HDPE resin is gel permeation chromatography. In this chromatographic method a solvent with the dissolved polyethylene flows through a column filled with a porous material. It is usually a gel of cross-linked polymers. Depending upon the size of the polyethylene coils in the solution, they can fit to the pores of the gel, stick there and block them whereby the transport is retarded. Larger polyethylene chains are transported unhindered with the solvent flow. Thus a size-dependent retardation occurs which justifies the other term size exclusion chromatography (SEC). In the chromatogram, which shows polymer concentration (determined for example via optical measurements (refractive index)) as a function of time, the time coordinate corresponds to a polymer molecular mass coordinate and the concentration... 

Francois et al. [97,98] reported on the synthesis of polystyrene-block-poly (para-phenylene) block copolymers via the anionic polymerization to polysty-rene-block-poly(l,3-cyclohexadiene) and subsequent aromatization. The micellar assemblies and molecular dispersed free chains could be separated by size exclusion chromatography and with this method the size of the spherical assemblies was found to be 30-50 A for the poly(pflra-phenylene) core, and 3-15 nm for the full micelle. By evaporating the solvent from solutions in carbondisulphide in moist air, a hexagonal array of empty cells was observed from optical and... 

The porosity of gels is usually determined by equilibrium permeation or size exclusion chromatography by measuring the internal volume, accessible to test molecules depending on their size (molecular weight MW, radius MR). The cumulative pore volume distribution, however, can also be measured optically. By microinterferometry of specimens, embedded in solutions of test molecules, the density of the matrix M, the inner volume and the relative access of defined molecules can be determined by measuring the optical path difference r between the porous specimen of thickness d and the embedding medium in the equilibrium... 

Figure 9.10 Three-dimensional representation of the data volume of a tryptic digest of ovalbumin. Series of planar slices through the data volume produce stacks of disks in order to show peaks. Reprinted from Analytical Chemistry, 67, A. W. Moore Jr and J. W. Jorgenson, Comprehensive three-dimensional separation of peptides using size exclusion chromatogra-phy/reversed phase liquid chromatography/optically gated capillary zone electrophoresis, pp. 3456-3463, copyright 1995, with permission from the American Chemical Society.

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