RESUMO
Peptiplexes are soft biomaterials formed through the noncovalent association between cell-penetrating peptides and nucleic acids. Although internalization often involves electrostatic anchoring followed by endocytosis, the mode of action of these transporters remains elusive in many cases, and proper understanding of mechanisms behind their penetrating capabilities necessarily entails structural data at the nanoscopic scale. In this chapter, we examine the structural landscape of peptiplexes, emphasizing the complex behavior of these polyelectrolyte self-assemblies and how supramolecular order impacts their translocation efficiency. We discuss experimental tools commonly used to investigate the structure of peptiplexes and pay special attention to small-angle X-ray scattering (SAXS) as a suitable method for unveiling their nanoscale organization. A roadmap for standard SAXS measurements in CPP/DNA samples is presented alongside a selection of observations from our own experience dealing with SAXS applied to the investigation of CPPs.
Assuntos
Espalhamento a Baixo Ângulo , Peptídeos Penetradores de Células , DNA , Ácidos Nucleicos , Difração de Raios XRESUMO
Abstract Experimental information from small angle X-ray scattering (SAXS) is conjugated with nuclear magnetic resonance (NMR) spectroscopy data for the improvement of protein structure determination, particularly for flexible, multidomain or intrinsically disordered proteins. Individually, each of these techniques presents capabilities and limitations: NMR excels in local information, providing atomic resolution, but is limited by protein size, whereas SAXS yields a global envelope of the protein with lower resolution, but revealing domain positions. Different conjugation methodologies use the complementarity of both technique´s independent constraints to accomplish a comprehensive protein structure determination and dynamics understanding at a moderate computational expense.
Resumen Se conjuga información experimental proveniente de dispersión de rayos X a ángulos pequeños (SAXS) con la espectroscopía de resonancia magnética nuclear (NMR) para perfeccionar la determinación de la estructura protéica, en particular de proteínas flexibles, de multidominio o intrínsecamente desordenadas. Individualmente, cada una de estas técnicas presenta capacidades y limitaciones: NMR se destaca en la información local, proporcionando resolución atómica, pero está limitada por el tamaño de la proteína, mientras que SAXS produce una envoltura global de la proteína con una resolución menor pero revelando las posiciones de los dominios. Las diferentes metodologías de conjugación utilizan la complementariedad de las restricciones independientes de ambas técnicas para seguir estrategias adecuadas de acuerdo con la proteína, logrando una determinación integral de la estructura y una comprensión de las dinámicas del sistema proteico a un costo computacional moderado.