Label triangulation

Some model experiments have been carried out based on the use of label triangulation of heavy metal markers [51,162,163]. Using a related nomenclature to Section... 

Label triangulation using deuterated proteins within a multimeric protein structure was first apphed to DNA-dependent RNA polymerase [52,191-194] to... 

Fig. 30. The 19 protein neutron map of the 30S ribosomal subunit determined by label triangulation (right). The proteins are depicted as spheres whose volumes are to scale. For clarity, several spheres are drawn unfilled. The centre-to-centre distance between S13 and S17 is 17.3 nm [490]. The left view shows the electron microscopy model of the 30S subunit and the sites of the antigenic determinants from immune electron microscopy techniques [490]. Note that most of the protein is located to the top of the model as viewed, while the RNA is predominant in the lower half.

Plots should be clearly labeled, and the trial/study identity should be marked in the vicinity of the trial. Plots should be clearly triangulated to fixed points so that at a later date independent third parties can identify separate plots on the basis of documentation. 

This method requires low sample concentration in order to avoid interparticle interference effects. However, if an equimolar mixture of unlabelled and bilabelled particles (A + D) and an equimolar mixture of the two singly labelled particles (B -I- C) are measured, subtraction of the two scattering curves permits 7,2 to be measured at high concentration since the interparticle effects are eliminated [52], This is important for the triangulation of subunits in large systems such as the ribosome, since otherwise the label concentration becomes extremely low. 

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