title: All-atom molecular dynamics simulations of an artificial sodium channel in a lipid bilayer: the effect of water solvation/desolvation of the sodium ion.
abstract: All-atom molecular dynamics is used to investigate the transport of Na(+) across a 1,2-dioleoyl-sn-glycero-3-phosphocholine lipid bilayer facilitated by a diazacrown hydraphile. Specifically, the free energy of Na(+) passing through the bilayer is calculated using the adaptive biasing force method to study the free energy associated with the increase in Na(+) transport in the presence of the hydraphile molecule. The results show that water interaction greatly influences Na(+) transport through the lipid bilayer as water is pulled through the bilayer with Na(+) forming a water channel. The hydraphile causes a reduction in the free energy barrier for the transport of Na(+) through the head group part of the lipid bilayer since it complexes the Na(+) reducing the necessity for water to be complexed and, therefore, dragged through with Na(+), an energetically unfavorable process. The free energy associated with Na(+) being desolvated within the bilayer is significantly decreased in the presence of the hydraphile molecule; the hydraphile increases the number of solvation states of Na(+) that can be adopted, and this increase in the number of available configurations provides an entropic explanation for the success of the hydraphile.
authors.affiliation: a School of Health Sciences , University of KwaZulu Natal , Westville Campus, Durban , South Africa.
authors.forename: A A
authors.initials: AA
authors.lastname: Skelton
authors.affiliation: a School of Health Sciences , University of KwaZulu Natal , Westville Campus, Durban , South Africa.
authors.forename: V M
authors.initials: VM
authors.lastname: Khedkar
authors.affiliation: b Chemical Engineering , University of Louisville , Louisville , KY , USA.
authors.forename: J R
authors.initials: JR
authors.lastname: Fried
mesh_terms: D057927:Hydrophobic and Hydrophilic Interactions; D007477:Ions / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry*; D008968:Molecular Conformation; D056004:Molecular Dynamics Simulation; D011789:Quantum Theory; D012964:Sodium / Q000737:chemistry; D015222:Sodium Channels / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D007477:Ions; D008051:Lipid Bilayers; D015222:Sodium Channels; D012997:Solvents; D014867:Water; D012964:Sodium
keywords: free energy calculations; ion complexation; ion solvation; ion transport; molecular dynamics