Sodium dodecyl sulfate modification

The protein was purified by a dialysis procedure, denatured and analysed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Western blotting indicated that the protein of interest consisted of two components, one of which increased in concentration as the purification proceeded. The authors initially suggested that this could be due to the presence of a number of species produced by modification of the amino acid side-chains, for example, by glyco-sylation, or by modification of the C- or N- terminus. 

The physical meaning of the g (ion) potential depends on the accepted model of an ionic double layer. The proposed models correspond to the Gouy-Chapman diffuse layer, with or without allowance for the Stem modification and/or the penetration of small counter-ions above the plane of the ionic heads of the adsorbed large ions. " The experimental data obtained for the adsorption of dodecyl trimethylammonium bromide and sodium dodecyl sulfate strongly support the Haydon and Taylor mode According to this model, there is a considerable space between the ionic heads and the surface boundary between, for instance, water and heptane. The presence in this space of small inorganic ions forms an additional diffuse layer that partly compensates for the diffuse layer potential between the ionic heads and the bulk solution. Thus, the Eq. (31) may be considered as a linear combination of two linear functions, one of which [A% - g (dip)] crosses the zero point of the coordinates (A% and 1/A are equal to zero), and the other has an intercept on the potential axis. This, of course, implies that the orientation of the apparent dipole moments of the long-chain ions is independent of A. 

To the filtered seawater (500 ml about 1.5 xg U) is added 0.05 M ferric chloride (3 ml), the pH is adjusted to 6.7 0.1 and the uranium present as (U02(C03)3)4- is adsorbed on the colloidal ferric hydroxide which is floated to the surface as a stable froth by the addition of 0.05% ethanolic sodium dodecyl sulfate (2 ml) with an air-flow (about 10 ml min-1) through the mixture for 5 min. The froth is removed and dissolved in 12 M hydrochloric acid-16 M nitric acid (4 1) and the uranium is salted out with a solution of calcium nitrate containing EDTA, and determined spectrophotometrically at 555 nm by a modification of a Rhodamine B method. The average recovery of uranium is 82% co-adsorbed WO4- and M0O4- do not interfere. 

The easiest way to detect a protein modification seems to be the mass measurement of all peptides generated by enzymatic digestion. The comparison with the predicted peptide masses from the sequence of the protein identifies unmodified peptides and unexplained masses would give indications to modified peptides. Unfortunately, this is not a suitable approach in practice. In many peptide mapping experiments done with the MALDI mass mapping technique, up to 30% of the measured masses remain unexplained. This is probably due to protein contaminations from human keratins, chemical modifications introduced by gel electrophoresis and the digestion procedure, and other proteins present at low levels in the piece excised from the sodium dodecyl sulfate gel. The detection of a protein modification requires a more specific analysis. 

In this modification, the ionic micelle has been considered as the charged phase, which has difficulties from the thermodynamic viewpoint. The precise measurement of the surface tension of aqueous sodium dodecyl sulfate solutions revealed the cotlnuous decrease of surface tension above the cmc and indicated that the charged phase separation model is not correct (27). ... 

One of the most useful techniques for visualization of the proteome is two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis (2-D SDS-PAGE). This technique possesses unmatched resolving power for separation of proteins [2-4] and has been used extensively to analyze proteins [5-8], their regulation [9-18], and posttranslational modifications [19-22], Several tech-... 

A DNA extraction protocol that has proved useful for most ancient tissues is a modification of the protocol initially published by Blin and Stafford.20 Approximately 0.1 g of small pieces of soft tissue is added to 5 ml of extraction buffer containing 10 mM Tris-HCl (pH 8.0), 2 mM ethylenediaminetetraacetic acid (EDTA), 10 mM NaCl, 1% (w/v) sodium dodecyl sulfate (SDS), 10 mg/ml dithiothreitol (DTT), and 0.5 mg/ml proteinase K. Incubation at 37° with gentle agitation overnight will allow most or all of the tissue to go into solution. An equal volume of phenol, equilibrated with 1 M Tris-HCl (pH 8.0), is added. When the phenol is being equilibrated, care should be taken to use uncontaminated Tris buffer and to measure the pH only on aliquots that are removed from the water phase and then discarded. Two phenol extractions and one chloroform extraction are performed, and the water phase is concentrated and purified on a Centricon 30 microconcentrator (Amicon, Danvers, MA). The reten-tate can be stored frozen, preferably in a few aliquots. In all cases solutions should be manipulated with DNA-free positive displacement pipettes. 

Another modification of CE is micellar electrokinetic chromatography (MEKC), which is widely used for the separation of nonpolar compounds. The molecules in question partition into micelles (nonpolar layer) with mechanisms similar to those observed with reverse-phase chromatography. An anionic surfactant, sodium dodecyl sulfate, is commonly used as a micellar... 

Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of ghost membrane proteins was performed by a modification of the method of Laemmli (17). Samples were reduced with p-mercaptoethanol and run in 11% gels. Molecular weight (MW) standards were obtained from Pharmacia Canada Ltd. 

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