Surface labeling techniques

When HeLa cells were.cultured in medium supplemented with 5 mM sodium butyrate, their content of GM3 increased (Fig.2a). Increases varied from 3.5 to 5-fold depending on the experiment (4,8,12,13). When the butyrate was removed and the cells were cultured in normal medium for 24 h, the GM3 levels returned to those found in untreated cells (Fig. 2a). Similar results were observed when N-[acetyl-3H]-D-mannosamine, a precursor of sialic acid, was also included in the culture medium. In the butyrate-treated cells, radioactivity associated with GM3 increased 6.5-fold and 24 h after butyrate was removed, the amount of labeling returned to control values (Fig. 2b). We also were able to label the GM3 by means of a cell surface labeling technique. Control and butyrate-treated cells were exposed to 10 mM sodium periodate and the oxidized sialyl residues were reduced with NaBSfy. There was 5.5-fold more 3h associated with the GM3 recovered from the butyrate-... 

The direct labeling technique may be applied to either unfixed cells or fixed tissue, provided that the antigen is stable to fixation. Often this must be determined empirically (see Chapter 8). The following protocol presents the simplest approach direct labeling of a surface antigen on unfixed cells in suspension. 

This method, related to FRES, is used to determine the concentration of deuterium-labelled chains as a function of depth at a surface. The technique... 

The study of wear on machine parts, which were labelled by radioisotopes, is an important stage in the development work of the automotive industry. The design of a new motor necessitates hundreds of wear tests to be carried out. These tests can be made by using the radioisotope tracer technique. The surface activation technique, in... 

So far the emphasis has been on adsorption of c.d. ions in the presence of weak or no specific adsorption of the background electrolyte. For most surfaces in contact with common 1-1 electrolytes this is a reasonable approximation. For high concentrations of 1-1 electrolytes or with divalent counterions substantial s.a. is however common. Direct studies of specific adsorption have been made using radio labelling techniques [66, 67]. Also many examples of electrokinetic measurements of specific adsorption can be found in the literature [e.g., 68-72]. 

Isotopic Studies. In this analysis mode the mass spectrometer Is used to determine the relative abundance of different Isotopes of the same element. SIMS Is the only common surface analysis technique that can distinguish the Isotopes of both the light and heavy elements. This mode Is advantageously used In mechanistic studies using Isotopically labelled samples. By using different Isotopes of the same element experiments can be performed without concern for the differences In chemical effects between the species. 

We have been searching for experimental methods that can measure surface viscosities as low as 10 10 g/sec or measure the collisional dynamics that should correspond to the Mann-Cooper model. To qualify, the experimental method must respond to dilute monolayers having densities less than 1014 mojecules/cm2. From our experience with the ESR spin label technique for measuring bulk viscosity effects in ultrathin films (8),... 

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