molecular mechanisms underlying the association of a pro-A molecular model was constructed simulating a pentapeptide tein with a surface. Understanding how a protein adsorbs protein, leucine enkephalin, near a crystalline polyethylene (PE) may suggest ways in which the adsorption process can be surface surrounded by explicit water molecules. A molecular dymodified or controlled.
namic simulation of the model was performed to examine the Recently, molecular dynamics (MD) simulations were forces exerted on the protein by the surface and the water moleused to develop interaction force fields for crystalline polycules. The orientational distribution functions of the water moleethylene and leucine enkephalin, a small pentapeptide (6).
cules were examined to determine if and how structured or ordered
These MD simulations provided a reasonable demonstration water in the model contributed to the attractive and repulsive of how the protein approaches and gathers near a surface by forces between the protein and the surface. The results of the simulations showed that there is relatively strong spatial and orien-providing a molecular model of the forces present on the tational structuring of the water adjacent to the PE surface, and protein due to atomic interactions with the surface and with a lesser amount of structuring near the protein. The distribution the solvent. The results of these simulations only showed is a function of the orientation of the protein with respect to the how the protein responds to external forces and did not surface. The proximity of the protein to the surface has a strong adequately explain why the observed forces existed. Howinfluence on the density and structure of water between the protein ever, it is believed that solvent interactions in the system and surface. A linear correlation between the force of water on played a key role in the protein's behavior near a surface.
the protein and the angular distribution of water molecules was
The objective of this research was to study the structure observed in the most dense region of water between the protein of water near the protein and the adsorbent surface and deterand surface. When the protein presents its polar side toward the mine what effect the water structure has upon the forces nonpolar PE surface, the water structure near the protein disrupts exerted on the protein. The spatial and orientational distributhe normal structure of water near the surface. Additionally, the orientational structure of the water between them causes an asym-tion functions (SDF and ODF) of the water were the princimetric force on the protein, pushing it away from the surface. ple areas of examination. When the nonpolar side of the protein is presented toward the Previous MD simulations of water at an interface have fo-PE, there is less disruption of water structure, and the interaction cused on interfaces that included metals, several simulated hyforces are attractive. ᭧ 1998 Academic Press drophobic surfaces, and spherical cavities (10-15). Attempts Key Words: Water structure; polyethylene; enkephalin; molecuhave also been made to study the SDF and ODF of water lar dynamics; protein adsorption. around a protein using MD simulations (16-18). The data from the research of Komeiji et al. (16) suggest that the environment of the protein atoms influences the structure of the SIMULATION PROCEDURE formation (3-5), protein denaturation (6), fouling (7), and surface degradation (8). The problem with current methods
This research used MD simulations to determine what used to study protein adsorption is that none reveals the influence solvent structure has in the behavior of proteins near a solid surface (19). The approach was to determine the solvent effects by calculating the spatial and orientation