Tropomyosin (Tm) is a dimeric coiled-coil protein, composed of 284 aminoacids (410Å), that forms linear homopolymers through head-to-tail interactions. The head-to-tail complex involves the overlap of approximately 11 N-terminal residues of one molecule with 11 C-terminal residues of another Tm molecule, stabilized by electrostatic forces. This interaction allows the formation of continuous cables of Tm in both sides of the actin filament, which makes possible the cooperative interaction among sets of 7 actins, 1 tropomyosin and 1 troponin complex in each thin filament strand in muscle. In spite of a large body of experimental information concerning the structure and function of Tm, there are few reports concerning the head-to-tail interaction and no high resolution structural information regarding this complex is available. We used a recombinant  C-terminal Tm fragment (Tm_{143-284 5OHW269}) containing a 5-hydroxytryptophan probe (5OHW) at position 269, located fifteen residues from the C-terminus of the polypeptide chain to study complex formation with the N-terminal fragment (ASTm_1-142). Fluorescence emission intensity changes of Tm_{143-284 5OHW269} upon titration with N-terminal fragments allowed us to calculate dissociation constants (K_d) and interaction energies (ΔGº) under different conditions  (+/- 5mM MgCl₂, pH 7.0, pH 8.0). Several mutations were screened: D275, H276 and D280 in the C-terminus, and D2, K5, K6 and K7 in the N-terminus, were changed to alanine residues. The ΔGº of binding between the several combinations of fragments allowed us to calculate a thermodynamic double mutant cycle, which was used to identify interactions between charged residues in the head-to-tail complex. These data were translated into ambiguous distance restraints which were used to drive the docking process of the wild type N- and C-terminal fragments of Tm, using a protein docking program. The final solutions were chosen by the quality of the fitting to the input data. They also predict new contacts that help to stabilize the interface. The accuracy of our model will be improved by the design of other double-mutants and NMR experiments.