Proposed electron transfer pathway between 3NTDO-F_DS2 and 3NTDO-O_DS2.

<p>(A) Ferredoxin is shown in brown color at the top of 3NTDO-O_DS2; Iron and sulphur are shown in magenta and yellow. (B) A line is drawn from Rieske center of 3NTDO-F_DS2 to the mononuclear iron of 3NTDO-O_DS2 through the Rieske cluster of 3NTDO-O_DS2. (C) Proposed electron transfer pathway from Rieske cluster of ferredoxin to active site mononuclear iron of oxygenase of NDO is plotted in ball and stick model, the residues of chain A and chain C of oxygenase are shown in green and cyan color.</p

Comparison of active site residues of 3NTDO-O_DS2 and NBDO.

<p>The residues responsible for regioselectivity of 3NTDO-O_DS2 (A) and NBDO (B) are shown in green and orange stick model, respectively. The mononuclear iron center (large magenta sphere) is coordinated with two histidine and one aspartic residue.</p

Docked conformations of 3-nitrotoluene in the active site of 3NTDO-O_DS2.

<p>(A) 3-methylcatechol product orientation (B) 4-methyl-2-nitrophenol orientation. The distance between mononuclear iron and carbon atoms of benzene ring is shown in red dotted lines. The ligands His208, His211, Asp360 and mononuclear iron (magenta) are shown in ball and stick model. The active site residues are shown in stick and 3-nitrotoluene is in orange color.</p

Oxidation products ratios^b (%) formed by 3NTDO and its variants with mononitrotoluenes.

<p>^bProduct ratios were determined from by theintegration of Gas chromatography mass spectrometry (GC-MS) total ion current chromatogram. Results reported are the average of at least three independent experiments, and standard deviations were less than 7%.</p

Overall structure of ferredoxin and oxygenase components of 3NTDO.

<p>(A) 3NTDO-F_DS2, the Rieske center and coordinating side chain residues are shown in stick representation. (B) 2Fo-Fc electron density contoured at 1.0 σ level in the Rieske cluster of ferredoxin shown as a ball and stick model and in blue wire mesh. (C) 3NTDO-O_DS2, the three αsubunits are colored green, blue and red and β subunits are in yellow, grey and cyan. The Rieske center and the catalytic iron are shown in CPK model representation. (D) 2Fo-Fc electron density contoured at 1.5σ level in the vicinity of catalytic iron center with the ligand His206, His211 and Asp360 shown as a ball and stick model. (E) View along the molecular threefold axis of 3NTDO-O_DS2. The iron, sulphur, nitrogen and water are shown in magenta, yellow, blue and red colors, respectively.</p

Segregation into Chiral Enantiomeric Conformations of an Achiral Molecule by Concomitant Polymorphism

An analogue of the green fluorescent protein (GFP) luminophore crystallizes from a methanol solution impregnated with dichloromethane, into a pair of chiral crystals. Thermal analysis, fluorescence emission studies, and crystal packing analysis show that the two crystals are different materials. The two polymorphs arise from the rotation of a monosubstituted benzene ring about a C–N bond which results in the formation of two strong bifurcated C–H···O intermolecular bonds to oxygen O(6). The color difference has been ascribed to a difference in the packing of the two crystal forms. Theoretical studies supported by low temperature NMR show low kinetic energy barriers (∼10 kJ mol^–1) separating the asymmetric units of the two crystal structures, suggesting that the driving force for the polymorphism could be the result of packing of two different asymmetric units

Segregation into Chiral Enantiomeric Conformations of an Achiral Molecule by Concomitant Polymorphism

An analogue of the green fluorescent protein (GFP) luminophore crystallizes from a methanol solution impregnated with dichloromethane, into a pair of chiral crystals. Thermal analysis, fluorescence emission studies, and crystal packing analysis show that the two crystals are different materials. The two polymorphs arise from the rotation of a monosubstituted benzene ring about a C–N bond which results in the formation of two strong bifurcated C–H···O intermolecular bonds to oxygen O(6). The color difference has been ascribed to a difference in the packing of the two crystal forms. Theoretical studies supported by low temperature NMR show low kinetic energy barriers (∼10 kJ mol^–1) separating the asymmetric units of the two crystal structures, suggesting that the driving force for the polymorphism could be the result of packing of two different asymmetric units

Excited State Relaxation Dynamics of Model Green Fluorescent Protein Chromophore Analogs: Evidence for <i>Cis–Trans</i> Isomerism

Two green fluorescent protein (GFP) chromophore analogs (4<i>Z</i>)-4-(<i>N</i>,<i>N</i>-dimethylaminobenzylidene)-1-methyl-2-phenyl-1,4-dihydro-5<i>H</i>-imidazolin-5-one (DMPI) and (4<i>Z</i>)-4-(<i>N</i>,<i>N</i>-diphenylaminobenzylidene)-1-methyl-2-phenyl-1,4-dihydro-5<i>H</i>-imidazolin-5-one (DPMPI) were investigated using femtosecond fluorescence up-conversion spectroscopy and quantum chemical calculations with the results being substantiated by HPLC and NMR measurements. The femtosecond fluorescence transients are found to be biexponential in nature and the time constants exhibit a significant dependence on solvent viscosity and polarity. A multicoordinate relaxation mechanism is proposed for the excited state relaxation behavior of the model GFP analogs. The first time component (τ₁) was assigned to the formation of twisted intramolecular charge transfer (TICT) state along the rotational coordinate of N-substituted amine group. Time resolved intensity normalized and area normalized emission spectra (TRES and TRANES) were constructed to authenticate the occurrence of TICT state in subpicosecond time scale. Another picosecond time component (τ₂) was attributed to internal conversion via large amplitude motion along the exomethylenic double bond which has been enunciated by quantum chemical calculations. Quantum chemical calculation also forbids the involvement of hula-twist because of high activation barrier of twisting. HPLC profiles and proton-NMR measurements of the irradiated analogs confirm the presence of <i>Z</i> and <i>E</i> isomers, whose possibility of formation can be accomplished only by the rotation along the exomethylenic double bond. The present observations can be extended to <i>p</i>-HBDI in order to understand the role of protein scaffold in reducing the nonradiative pathways, leading to highly luminescent nature of GFP