Zwitterionic Structure Of The Molecular Dynamics Simulation Of Poly 13 Alanine (polyalanine13) Peptide Chain Of Natural Behavior In Aqueous Solutions To Maintain,

The hypothesis of "Maintain of normal conformation" predicted theoretically that zwitterionic structure is not apt to change the normal conformations of contacting proteins and therefore will be blood compatible. While recent experimental studies on surface-grafted zwitterionic biomaterials have proved good blood compatibility, the validity of this hypothesis still needs to be testified from the interactions between zwitterionic surface and biosystem on the sub-molecular level. For the natural protein/biomolecule-water interaction is critical in maintaining the normal conformation of protein/biomolecule under physiological condition, to understand the surface-induced change of protein/biomolecule-water interaction has a fundamental sense in investigating the blood compatibility of biomaterials surface. Molecular dynamics simulation using empirical force fields provides one of the most direct methods of theoretically investigating the behaviors of complex molecular systems and is well-suited for the simulation of biosystem -surface interactions. However, all-atom modeling of proteins is not feasible in current work due to the limited computational resources. PolyAlanine13(A13)with a typical second structure ofα-helix was then selected to develop the biosystem-surface model. Zwitterionic surface and hydrophobic surface were modeled to present different surface chemistry to A13. In addition, single A13 in aqueous environment without any surface influences was simulated to represent the natural situation. The objectives of present research were to provide details of sub-molecular level biosystem -surface interactions, and by comparing adsorption behaviors and conformational changes of A13 over different surfaces, influences of different surfaces to A13-water interaction and the molecular mechanisms leading to these influences can be evaluated. Over 12 ns molecular dynamics simulations with GROMACS43a1 force field had been applied to aforementioned two cases. The results showed that zwitterionic surface behaves better to maintain the natural behavior of A13 in water; whereas the hydrophobic surface which significantly affects the natural behavior of A13 in water has been recognized as less blood compatible experimentally. Although more complicated protein needs to be studied, this finding should be a good first proof to the hypothesis of "Maintain of normal conformation"...