This work consists on the development of a novel methodology, relatively simple and economic, in order to achieve the isolation and sequence of the C-terminal end of proteins.

The result is located inside the necessities of diverse projects of molecular biology's field that require the identification and characterization of new proteins isolated from their sources, and the comparison of their sequence with the references of their databases of established sequences.

In this respect, although there is an established and automated method for the sequence of N-terminal group, the same thing does not occurs with the C-terminal end, where there are alteration differences, and advantages-disadvantages correspondance has not allowed establishing a definitive variant.

In the developed methodology, it is used an acid anhydride under conditions of selective blockade of the group amino of peptics previously obtained by tryptic action, which generates peptides' mixture that contains at least a positive load in the basic amino acid located in the C-terminal of each peptide, except in the last one, which should be neuter. Such a difference facilitates the use of a chromatographic column of very small volume to separate this peptide.

There have been characterized, with this method, diverse commercial proteins such as C cytochrome, myoglobins and some recombinants obtained in the CIGB like the streptokinase, TAB-A and mucor pepsin, among others, analyzing C-ternimal peptide isolated by mass spectrometry.

For all these reasons, the result is novel and constitutes in essence a contribution to the scientific knowledge inside an area of scientific-technical expansion of genetic engineering and molecular biology, with application inside this sphere.

This contribution to knowledge, together to the scientific rigor with which it is carried out, are some of the elements that made the scientific committee of methods event in protein structures analysis, which took place in Germany, request its publication in the summary book of this congress, which represents one of the most important in the field of proteins' structural studies. This selection highlights the interest and acceptance of the work to the level of the international scientific community highly specialized in this subject.