Abstract
Twoโdimensional (2โD) electrophoresis is a very useful technique for the analysis of proteins in biological tissues. The complexity of the 2โD maps obtained causes many difficulties in the comparison of different samples. A new method is proposed for comparing different 2โD maps, based on five steps: (i) the digitalisation of the image; (ii) the transformation of the digitalised map in a fuzzy entity, in order to consider the variability of the 2โD electrophoretic separation; (iii) the calculation of a similarity index for each pair of maps; (iv) the analysis by multidimensional scaling of the previously obtained similarity matrix; (v) the analysis by classification or cluster analysis techniques of the resulting map coโordinates. The method adopted was first tested on some simulated samples in order to evaluate its sensitivity to small changes in the spots position and size. The optimal setting of the method parameters was also investigated. Finally, the method was successfully applied to a series of real samples corresponding to the electrophoretic bidimensional analysis of sera from normal and nicotineโtreated rats. Multidimensional scaling allowed the separation of the two classes of samples without any misclassification.