Growth Hormone Releasing Hexapeptide is able to form Nanotubes: a complementary study by Small Angle X-Ray Scattering, Transmission Electron Microscopy and Molecular Dynamic Simulations

BARBOSA, LRS; SANTANA, H; AVILA, CL; CABRERA, I; PÁEZ, R; FALCÓN, V; PESSOA, JR. A; VENTOSA, N; VECIANA, J; ITRI, R

Carlos Paz, Cordoba

Congreso; XLII Reunion Anual de la Sociedad Argentina de Biofisica; 2013

Sociedad Argentina de Biofisica

Growth hormone releasing peptide belongs to a class of synthetic growth hormone secretagogues, which stimulate growth hormone secretion from somatotrophs in several species including humans. Besides, it was recently used in vivo in the treatment of amyotrophic lateral sclerosis (ALS) disease. In the present study, we investigated the self-assembling properties of GHRP-6, using small angle X-ray scattering, transmission electronic microscopy (TEM) as well as molecular dynamics simulation. The combined results demonstrated that GHRP-6 self-assembles into very long nanotubes, with inner and outer cross-sections of 7(1) and 13(1) nm, respectively, at 20 mg/mLin phosphate buffer solution at pH 7.4. At concentrations > 30 mg/ml, both SAXS and cryo-TEM results indicate that the shape of the long aggregates remains the same and a bundle of nanotubes are disposed in a hexagonal arrangement in solution, with a very well defined center-to-center distance of circa15 nm, according to SAXS data analysis These results indicates that GHRP-6 self-assembles like dimers in the cylinder wall. Molecular dynamics simulations also reflect the capability of the peptides to self-assemble like amphiphilic molecules in aqueous solutions, giving additional details about the arrangement of the peptides within the nanotube.