Bounding a molecule in a noisy synthesis

A method of bounding a protein molecule in a very noisy synthesis is considered. It consists of two steps. In the first step ('nonlinear filtration') basic points are chosen that are most likely to belong to the region of the molecule. In the second step ('linear filtration') a compact region with the maximal concentration of these points is searched. Various modifications of the method are analysed. It is shown that the molecular region in a finite-resolution synthesis contains not only the highest positive maxima of the density distribution but also the deepest negative minima.