1.3.7.5 hanging drop vapour diffusion method with 18% PEG-8000, 0.025 M MES-NaOH at pH 6.5, 0.05 M Ca(OAc)2 at pH 6.5, and 5% dioxane (or 5% ethanol) 685125 1.3.7.5 high-field electron paramagnetic resonance spectroscopy of frozen solutions and single crystals of the one-electron reduced protein-substrate complex of mutant D102N. Spectra reveal a biliverdin radical with a very narrow g tensor. This g tensor is consistent with a biliverdin radical where the carbonyl oxygen atoms on both the A and the D pyrrole rings are protonated 698489 1.3.7.5 high-field electron paramagnetic resonance spectroscopy of frozen solutions and single crystals of the one-electron reduced protein-substrate complex of mutant D105N. Spectra reveal a biliverdin radical with a very narrow g tensor with principal values 2.00359(5), 2.00341(5), and 2.00218(5). This g tensor is consistent with a biliverdin radical where the carbonyl oxygen atoms on both the A and the D pyrrole rings are protonated 698489 1.3.7.5 PcyA–biliverdin IXalpha complex by the hanging-drop vapor-diffusion method, PcyA is folded in a three-layer alpha/beta/alpha sandwich structure, in which biliverdin IXalpha in a cyclic conformation is positioned between the beta-sheet and C-terminal alpha-helices 676847 1.3.7.5 purified recombinant enzyme mutant V225D in complex with substrates biliverdin IXalpha or biliverdin XIIIalpha, mixing of 0.0009 ml of protein solution, containing 11.5 mg/ml protein and biliverdin, with 0.0009 ml of reservoir solution containing 0.8-1.0 M NaH2PO4, 1.0-1.2 M K2HPO4, and 100 mM sodium acetate, pH 4.0, 20°C, a few days, X-ray diffraction structure determination and analysis at 1.9 A resolution 711117 1.3.7.5 purified recombinant mutant enzymes, hanging drop vapour diffusion method, dithionite-treated reduced D105N PcyA crystals from 1.45-1.8 M ammonium sulfate, 0.15-0.4 M NaCl, and 0.1 M HEPES, pH 7.0, dithionite-treated reduced H88Q PcyA crystals from 1.7-2.2 M ammonium sulfate, 0.26-0.32 M NaCl, and 0.1 M sodium cacodylate, pH 7.0, 20°C in the dark, cryoprotectant solution is consisting of 30% v/v ethylene glycol in mother liquor, X-ray diffraction structure determination and analysis at 1.5 A resolution 724288 1.3.7.5 purified recombinant wild-type and mutant enzymes, hanging drop vapor diffusion method, mixing of 0.002 ml of protein solution containing 15 mg/mL protein and 0.67 mM biliverdin IXalpha, with 0.002 ml of reservoir solution containing 1-1.25 M sodium citrate, 0.1-0.4 M NaCl, and 0.1 M Tris HCl, pH 7.0, 21°C, 1-2 weeks. Crystal trials are set up under green safelight and stored in the dark, X-ray diffraction structure determination and analysis at 1.18-1.49 A resolution 724131 1.3.7.5 purified recombinant wild-type PcyA and PcyA-E76Q mutant in complex with 18EtBV or biloverdin IXalpha and biliverdin XIIIalpha, hanging drop vapor diffusion method, 20°C, method optimization, protein solution containing wild-type PcyA or mutant E76Q and bilin is mixed with reservoir solutions containing 0.85 M sodium citrate, 0.1 M sodium cacodylate, pH 7.0, for the PcyA-18EtBV complex and 2.0 M ammonium sulfate, 0.2 M NaCl, and 0.1M sodium cacodylate, pH7.0, for the PcyA-BV13 complex, for the mutant a reservoir solution containing 1.7 M ammonium sulfate, 2% PEG 400, and 0.1 M HEPES, pH 7.0, is used, X-ray diffraction structure determination and analysis at 1.04-1.48 A resolution 712411 1.3.7.5 quantum mechanical approaches show that the propensity of biliverdin to bind PcyA is dominated by electrostatic interactions, especially related to residues Arg149 and Lys221, while H-bonds are formed with His88 and Ser114. The antioxidant activity is dependent on the intramolecular noncovalent bond interactions. The surrounding residues increase the antioxidant character of biliverdin by 2 eV 742318 1.3.7.5 structure of the I86D-BVH+ complex and the protonation states of residues Asp105 and Glu76 in PcyA. Asp105 adopts a fixed conformation in the I86D mutant, but has dual conformations in wild-type PcyA which reflects the protonation states of biliverdin 742524 1.3.7.5 substrate-free form of PcyA by the hanging-drop vapor-diffusion method, at 2.5 A resolution, the side-chain of Asp105 is located at a site that would be underneath the biliverdin IXa A-ring in the PcyA-biliverdin IXa complex and hydrogen-bonded with His88, biliverdin IXa may be protonated by a mechanism involving conformational changes of these two residues before reduction 673657