Research
Structure, function, and dynamics of viral membrane peptides
Membrane proteins perform a multitude of tasks in a viral lifecycle. Fusion glycoproteins are specialized membrane-anchored biological machines that play critical roles in viral entry and infection. The membrane fusion mediated by the Spike glycoproteins from different coronaviruses requires an orchestrated participation of functionally relevant domains such as the fusion peptide and the transmembrane domain. The interaction of these segments with membranes drives significant conformational changes in the viral glycoprotein leading to the merge of the virus envelope with the cell membrane. Due to their sequence conservation among coronaviruses, they provide new targets for drug development. We are interested in determining the structural and dynamics determinants leading to the function performed by these membrane-interacting and membrane-spanning domains.
Repurposing and development of membrane fusion inhibitors
The fusion of biological membranes is a ubiquitous event in cell biology. Membrane fusion is essential for several physiological processes including, but not limited to, exocytosis, endocytosis, maintenance of normal mitochondrial function, fertilization, and viral infection. The fusion of two lipid bilayers can be regulated by different physicochemical parameters of the membranes, such as curvature, fluidity, lipid order, hydration, among others, which, in turn, can be modulated by different membranotropic agents. Here, we are interested in investigating the biophysical mechanism by which lipophilic drugs, peptides, and drug-peptide hybrids that display membranotropic activity exhibit an inhibitory action against membrane fusion since understanding the physicochemical parameters that affect the fusion reaction can help in the rational design of broad-spectrum membrane fusion inhibitors.
Mechanism of membrane action of cationic amphiphilic drugs
Cationic amphiphilic drugs (CADs) display an amphipathic structure that allows them to interact with and insert into phospholipid membranes. Once incorporated, CADs can alter a wide range of the physical properties of the bilayer, including lipid packing, membrane curvature, membrane fluidity, the translational and rotational diffusion of lipids, membrane potential, the phase transition temperature, surface charge density, phase coexistence, among others. The biological effects of the CAD's membranotropic activity are diverse. CADs can induce phospholipidosis, cause rupture of biological membranes, promote dissociation of enzymes from the bilayers, interfere with the permeability and local pH of the membranes, affect the activity and distribution of membrane-anchored enzymes, among other effects. In this project, we seek to understand the relationships between the CAD effects in the membrane properties and the function of the drugs in complex biological membranes.
Non-linear thermotropic phase behavior of lipid model membranes
The complex composition of biological membranes gives rise to lateral segregation of their constituents into liquid-disordered and raft-like, liquid-ordered phases. The coexistence of phases or lipid domains has been proposed as a crucial feature for membrane function and for several dynamic cellular processes. It has been shown that the reduction or disappearance of the phase coexistence region promoted by the action of membrane-interacting molecules can cause membrane function impairment. By using electron spin resonance (ESR) in combination with nonlinear least-squares (NLLS) spectral simulations, we have shown that the thermodynamic quantities (free energy, enthalpy, entropy, and heat capacity changes) describing the phase coexistence region of lipid model membranes are temperature-dependent and give rise to a non-linear van't Hoff behavior [Vieira et al 2017]. Our EPR/NLLS/van't Hoff strategy can detect differences in the thermodynamic properties of the two-phase coexistence region even when only very slight changes in the ordering and mobility of the phospholipids take place upon addition of an external agent. In this project, we are interested in understanding from a thermodynamic point of view how membrane-active agents can cause membrane function impairment by modulating phase coexistence in complex biological membranes.