title: Theoretical studies on the binding of rhenium(I) complexes to inducible nitric oxide synthase.
abstract: Considering our interest in the design of innovative radiometal-based complexes for in vivo imaging of nitric oxide synthase (NOS), we have recently introduced a set of M(CO)3-complexes (M=(99m)Tc, Re) containing a pendant N(ω)-NO2-L-arginine moiety, a known inhibitor of the enzyme. Enzymatic assays with purified inducible NOS have shown that the non-radioactive surrogates with 3-(Re1; Ki=84 μM) or 6-carbon linkers (Re2; Ki=6 μM) are stronger inhibitors than the respective metal-free conjugates L1 (Ki=178 μM) and L2 (Ki=36 μM), with Re2 displaying the highest inhibitory potency. Aiming to rationalize the experimental results we have performed a molecular docking study combined with molecular dynamics (MD) simulations and free energy perturbation (FEP) calculations. The higher inhibitory potency of Re2 arises from the stronger electrostatic interactions observed between the "Re(CO)3" core and the residues Arg260 and Arg382. This interaction is only possible due to the higher flexibility of its C6-carbon spacer, which links the N(ω)-NO2-L-arginine moiety and the "Re(CO)3" organometallic core. Furthermore, FEP calculations were carried out and the resultant relative binding energies (ΔΔGbind(calc)=0.690±0.028 kcal/mol,Re1/L1 and 1.825±0.318 kcal/mol, Re2/L2) are in accordance with the experimental results (ΔΔGbind(exp)=0.461±0.009 kcal/mol,Re1/L1 and 1.129±0.210 kcal/mol, Re2/L2); there is an energetic penalty for the transformation of the Re complexes into the ligands and this penalization is higher for the pair Re2/L2.
authors.affiliation: Unidade de Ciências Químicas e Radiofarmacêuticas, IST/ITN, Instituto Superior Técnico, Universidade Técnica de Lisboa, Estrada Nacional 10, 2686-953 Sacavém, Portugal. Electronic address: oliveira@nmr.mgh.harvard.edu.
authors.forename: Bruno L
authors.initials: BL
authors.lastname: Oliveira
authors.forename: Irina S
authors.initials: IS
authors.lastname: Moreira
authors.forename: Pedro A
authors.initials: PA
authors.lastname: Fernandes
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Ramos
authors.forename: Isabel
authors.initials: I
authors.lastname: Santos
authors.forename: João D G
authors.initials: JD
authors.lastname: Correia
mesh_terms: D020134:Catalytic Domain; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000378:metabolism; D006860:Hydrogen Bonding; D007527:Isoenzymes; D008024:Ligands; D008958:Models, Molecular; D008968:Molecular Conformation; D062105:Molecular Docking Simulation; D056004:Molecular Dynamics Simulation; D052247:Nitric Oxide Synthase Type II / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D012211:Rhenium / Q000737:chemistry* / Q000378:metabolism; D013816:Thermodynamics
chemical_list: D004791:Enzyme Inhibitors; D007527:Isoenzymes; D008024:Ligands; D012211:Rhenium; D052247:Nitric Oxide Synthase Type II
keywords: Docking; Free energy perturbation calculations; Molecular dynamics; Nitric oxide synthase; Rhenium; Technetium