Mayaro and Dengue are enveloped viruses belonging to Alphavirus and Flavivirus genus, respectively. These families are widely spread in the world, including in Brazil. The infectious cycle comprises many types of protein-protein and protein-nucleic acid interactions. The virus surface is composed by two non-covalently associated subunits, which play a critical role in the viral life cycle. The Mayaro E1 and E2 subunits are responsible for mediating membrane fusion and binding to cell-surface receptors, respectively. On the other hand, Dengue E subunit is responsible for both mechanisms involved in entry into host cells. Although the alphavirus and flavivirus have been extensively studied, the fusion mechanism has not been completely elucidated yet. In this work, we evaluated the correlation between virus conformational changes and the Gibbs free energy of membrane fusion using a calorimetric approach. We demonstrate that pHs lower than 6.0 and high hydrostatic pressure produce E1 trypsin resistant. trypsin resistant. This reorganization of viral protein to the trypsin resistant conformation is very important to membrane fusion. In addition, perturbation of the phospholipid bilayer induced by low pH and high hydrostatic pressure was similar.  However, we observed distinct behaviors at different pHs. At pH 5 or 5.5, there is mixing between Mayaro virus and liposomes. At pH 6, we observed a leakage of aqueous content, in contrast to pHs 5 and 5.5. Ours results show the great importance to understand the viral fusion protein structurally and thermodynamically for the development of efficient antiviral compounds.