Simultaneous analysis of ultrafast fluorescence decays of FMN binding protein and its mutated proteins by molecular dynamic simulation and electron transfer theory

Ultrafast fluorescence decays of FMN binding proteins (FBP) from Desulfovibrio vulgaris (Miyazaki F) were analyzed with an electron transfer (ET) theory by Kakitani and Mataga (KM theory). Time-dependent distances among isoalloxazine (Iso) and Trp-32, Tyr-35, and Trp-106 in wild-type FBP (WT), among Iso and Tyr-32, Tyr-35, and Trp-106 in W32Y (Trp-32 was replaced by Tyr-32), and among Iso and Tyr-35 and Trp-106 in W32A (Trp-32 was replaced by Ala-32) were determined by molecular dynamic simulation (MD). Electrostatic energies between Iso anion and all other ionic groups, between Trp-32 cation and all other ionic groups, and between Tyr-32 cation and all other ionic groups were calculated in WT, W32Y, and W32A, from the MD coordinates. ET parameters contained in KM theory, such as frequency (nu 0), a coefficient of the ET process (beta), a critical distance of the ET process ( R 0), standard free energy related to the electron affinity of the excited Iso ( G Iso (0)), and the static dielectric constant in FBP species (epsilon 0), were determined with and without inclusion of the electrostatic energy, so as to fit the calculated fluorescence decays with the observed decays of all FBP species, by a nonlinear least-squares method according to the Marquardt algorithm. In the analyses the parameters, nu 0, beta, and R 0 were determined separately between Trp residues and Tyr residues among all FBP species. Calculated fluorescence intensities with the inclusion of the electrostatic energy fit quite well with the observed ones of all WT, W32Y, and W32A.     

Conformational difference between two subunits in flavin mononucleotide binding protein dimers from Desulfovibrio vulgaris (MF): molecular dynamics simulation

The structural and dynamical properties of five FMN binding protein (FBP) dimers, WT (wild type), E13 K (Glu13 replaced by Lys), E13 R (Glu13 replaced by Arg), E13 T (Glu13 replaced by Thr) and E13Q (Glu13 replaced by Gln), were investigated using a method of molecular dynamics simulation (MDS). In crystal structures, subunit A (Sub A) and subunit B (Sub B) were almost completely equivalent in all of the five FBP dimers. However, the predicted MDS structures of the two subunits were not equivalent in solution, revealed by the distances and inter-planar angles between isoalloxazine (Iso) and aromatic amino acids (Trp32, Tyr35 and Trp106) as well as the hydrogen bonding pairs between Iso and nearby amino acids. Residue root of mean square fluctuations (RMSF) also displayed considerable differences between Sub A and Sub B and in the five FBP dimers. The dynamics of the whole protein structures were examined with the distance (RNN) between the peptide N atom of the N terminal (Met1) and the peptide N atom of the C terminal (Leu122). Water molecules were rarely accessible to Iso in all FBP dimers which are in contrast with other flavoenzymes.     

Simultaneous analysis of photoinduced electron transfer in wild type and mutated AppAs

Photoinduced electron transfer (PET) from Tyr21 to isoalloxazine (Iso) in the excited state (Iso*) is considered to be an initial step of the photosensing function of the blue-light sensing using flavin adenine dinucleotide (BLUF) component of the anti-repressor of the photosynthetic regulation (AppA). The PET mechanism was investigated via fluorescence dynamics of AppA and Kakitani and Mataga (KM) theories as well as by molecular dynamic (MD) simulation. The local structures of both the Y21F and W104F mutant AppAs around the Iso binding sites were quite different from those of the wild type (WT) AppA. The distances between Iso and Trp104 in Y21F, and between Iso and Tyr21 in W104F were shorter by 0.06 nm and 0.02 nm, respectively, compared to the WT. The frequency factor, ν₀, in Tyr21 was 1.15-fold greater than that in Trp104. The critical distance between adiabatic and non-adiabatic PET processes, R₀, was found to be very long in the AppA Tyr21. The large values of ν₀ and R₀ for Tyr21 of AppA compared to those in a non photosensing flavoprotein, FMN binding protein (FBP), were elucidated by hydrogen bond (H bond) chain between Tyr21 and Iso through Gln63. Interaction energies among Iso*, Trp104, Tyr21 and Gln63 in WT were calculated using the semi-empirical PM3 method. The amount of the transferred charge from Trp104 to Iso* in the WT exhibited a maximum at an interaction energy of around ?20 kcal/mol, but decreased as the interaction energy (absolute value) increased.     

Comparison between ultrafast fluorescence dynamics of FMN binding protein from Desulfovibrio vulgaris, strain Miyazaki, in solution vs crystal phases

Ultrafast fluorescence dynamics of FMN binding protein (FBP) from Desulfobivrio vulgaris, strain Miyaxaki F, were compared in solution and crystal phases. Fluorescence lifetimes of FBP were 167 fs (96%) and 1.5 ps (4%) in solution (tau(av) = 220 fs), and 730 fs (60%) and longer than 10 ps (40%) in crystals (tau(av) = 4.44 ps). The quenching of the fluorescence of flavin in the protein was considered to be due to photoinduced electron transfer (ET) from Trp or Tyr to the excited isoalloxazine (Iso) nearby. The average lifetime was 20 times longer in crystal vs in solution. Averaged distances between Iso and nearby Trp-32, Tyr-35, and Trp-106 were 8.42, 7.36, and 8.15 A in solution, respectively (obtained by NMR spectroscopy), and 7.05, 7.72, and 8.49 A in crystal, respectively (obtained by X-ray crystallography). The prolonged lifetime in crystal cannot be elucidated by the change in the distances between the states. It was suggested that the longer lifetime in crystal was ascribed to the absence of water molecules around FBP with rapid motional freedom, which may be the driving force for the ET in flavoproteins.     

Ultrafast fluorescence dynamics of FMN-binding protein from Desulfovibrio vulgaris (Miyazaki F) and its site-directed mutated proteins

Ultrafast fluorescence dynamics of FMN in FMN-binding protein (FMN-bp), and its mutated proteins, W32Y and W32A, were investigated by the fluorescence up-conversion method. Fluorescence lifetimes were 167 fs (96%) and 1.5 ps (4%) in wild-type FMN-bp (WT), and 3.4 ps (23%), 18.2 ps (74%), and 96 ps (3%) at 530 nm in W32Y, and 30.1 ps in W32A. The fluorescence lifetime of W32A, in which Trp-32 was absent, was about 140 times longer than that of WT. Tyr-32 in W32Y was not so effective quencher as Trp-32 in WT. This was explained in terms of different ionization potentials of quenchers and average donor–acceptor distances in the protein.     

Systematic approach to the quantitative voltammetric analysis of the FeIII/FeII component of the [alpha2-Fe(OH2)P2W17O61]7-/8- reduction process in buffered and unbuffered aqueous media

The one-electron reduction of [alpha(2)-Fe(III)(OH(2))P(2)W(17)O(61)](7-) at a glassy carbon electrode was investigated using cyclic and rotating-disk-electrode voltammetry in buffered and unbuffered aqueous solutions over the pH range 3.45-7.50 with an ionic strength of approximately 0.6 M maintained. The behavior is well-described by a square-scheme mechanism P + e(-) <--> Q (E(1)(0/) = -0.275 V, k(1)(0/) = 0.008 cm s(-1), and alpha(1) = 1/2), PH(+) + e(-) <--> QH(+) (E(2)(0/) = -0.036 V, k(2)(0/) = 0.014 cm s(-1), and alpha(2) = 1/2), PH(+) <--> P + H(+) (K(P) = 3.02 x 10(-6) M), and QH(+) <--> Q + H(+) (K(Q) = 2.35 x 10(-10) M), where P, Q, PH(+), and QH(+) correspond to [alpha(2)-Fe(III)(OH)P(2)W(17)O(61)](8-), [alpha(2)-Fe(II)(OH)P(2)W(17)O(61)](9-), [alpha(2)-Fe(III)(OH(2))P(2)W(17)O(61)](7-), and [alpha(2)-Fe(II)(OH(2))P(2)W(17)O(61)](8-), respectively; E(1)(0)' and E(2)(0)' are the formal potentials, k(1)(0)' and k(2)(0)' are the formal (standard) rate constants, and K(P) and K(Q) are the acid dissociation constants for the relevant reactions. The analysis for the buffered media is based on the approach of Laviron who demonstrated that a square scheme with fully reversible protonations, reversible or quasi reversible electron transfers with the assumption that alpha(1) = alpha(2), can be well-described by the behavior of a simple redox couple, ox + e(-) <--> red, whose formal potential, E(app)(0)', and standard rate constant, k(app)(0)', are straightforwardly derived functions of pH, as are the values of E(1)(0)', k(1)(0)', E(2)(0)', k(2)(0)', and K(P) (only three of the four thermodynamic parameters in a square scheme can be specified). It was assumed that alpha(app) = 1/2, and the simulation program DigiSim was used to determine the values of E(app)(0)' and k(app)(0)', which are required to describe the cyclic voltammograms obtained in buffered media in the pH range from 3.45 to 7.52 (buffer-related reactions which effect general acid-base catalysis are included in the simulations). DigiSim simulations of cyclic voltammograms obtained in unbuffered media yielded the values of E(1)(0)' and k(1)(0)'; K(Q) was then directly computed from thermodynamic constraints. These simulations included additional reactions between the redox species and H(2)O. The value of the diffusion coefficient of the [alpha(2)-Fe(III)(OH(2))P(2)W(17)O(61)](7-), 2.92 x 10(-6) cm(2) s(-1), was determined using DigiSim simulations of voltammograms at a rotating disk electrode in buffered and unbuffered media at pH 3.45. The diffusion coefficients of all redox species were assumed to be identical. When the pH is greater than 6, instability of P (i.e., [alpha(2)-Fe(III)(OH)P(2)W(17)O(61)](8-)) led to the loss of the reactant and precluded lengthy experimentation.     

Simulation of ultrafast non-exponential fluorescence decay induced by electron transfer in FMN binding protein

The ultrafast non-exponential fluorescence decay of FMN binding protein (FBP) was analyzed with three electron transfer (ET) theories, Marcus theory, Bixon and Jortner theory and Kakitani and Mataga theory. Center to center distances between electron acceptor, the excited isoalloxazine, and donors, Trp-32, Tyr-35 and Trp-106, in FBP were determined by molecular dynamic simulation. Electron transfer parameters containing in these theories were determined so as to fit the calculated decay with the observed decay, according to a non-linear least squares method. Introduction of electrostatic energies between isoalloxazine anion and other ionic groups and between the donor cations and other ionic groups in the protein into any ET theories improved the fitting. The non-exponential behavior in the fluorescence decay is considered to be ascribed to a fluctuation of the protein structure with long period.     

A method for treating the passage of a charged hard sphere ion as it passes through a sharp dielectric boundary

In the implicit solvent models of electrolytes (such as the primitive model (PM)), the ions are modeled as point charges in the centers of spheres (hard spheres in the case of the PM). The surfaces of the spheres are not polarizable which makes these models appropriate to use in computer simulations of electrolyte systems where these ions do not leave their host dielectrics. The same assumption makes them inappropriate in simulations where these ions cross dielectric boundaries because the interaction energy of the point charge with the polarization charge induced on the dielectric boundary diverges. In this paper, we propose a procedure to treat the passage of such ions through dielectric interfaces with an interpolation method. Inspired by the "bubble ion" model (in which the ion's surface is polarizable), we define a space-dependent effective dielectric coefficient, ε(eff)(r), for the ion that overlaps with the dielectric boundary. Then, we replace the "bubble ion" with a point charge that has an effective charge q/ε(eff)(r) and remove the portion of the dielectric boundary where the ion overlaps with it. We implement the interpolation procedure using the induced charge computation method [D. Boda, D. Gillespie, W. Nonner, D. Henderson, and B. Eisenberg, Phys. Rev. E 69, 046702 (2004)]. We analyze the various energy terms using a spherical ion passing through an infinite flat dielectric boundary as an example.     

The redox series [M(bpy)2(q)]n+, M = Ru or Os, Q = 3,5-di-tert-butyl-n-phenyl-1,2-benzoquinonemonoimine. Isolation and a complete X and W band EPR study of the semiquinone states (n = 1)

The complexes [M(bpy)(2)(Q)](PF(6)) (bpy = 2,2'-bipyridyl; M = Ru, Os; Q = 3,5-di-tert-butyl-N-phenyl-1,2-benzoquinonemonoimine) were isolated and studied by X and W band EPR in a dichloromethane solution at ambient temperatures and at 4 K. For M = Ru, the (14)N hyperfine splitting confirms the Ru(II)/semiquinone formulation, although at a > 1 mT, the (99,101)Ru satellite coupling is unusually high. W band EPR allowed us to determine the relatively small g anisotropy Delta g = g(1) - g(3) = 0.0665 for the ruthenium complex. The osmium analogue exhibits a much higher difference Delta g = 0.370, which is attributed not only to the larger spin-orbit coupling constant of Os versus that of Ru but also to a higher extent of metal contribution to the singly occupied molecular orbital. The difference Delta E between the oxidation and reduction potentials of the radical complexes is larger for the ruthenium compound (Delta E = 0.87 V) than for the osmium analogue (Delta E = 0.72), confirming the difference in metal/ligand interaction. The electrochemically generated states [M(bpy)(2)(Q)](n+), n = 0, 1, 2, and 3, were also characterized using UV-vis-near-infrared spectroelectrochemistry.     

非晶态聚对苯二甲酸乙二酯等温结晶的介电研究

非晶态PET的介电性质温度谱除α_a松弛和β松弛外,在120—130℃之间由于在升温过程中试样的结晶出现一个损耗峰。比较非晶态试样与结晶后试样介电常数ε′和介电损耗ε″的差别,可在97—113℃温度下用ε′和ε″来表征非晶态PET的等温结晶过程。在结晶的初期,ε′随时间的变化符合Avrami方程,即(ε′(t)-ε′(∞))/(ε′(0)-ε′(∞))=exp(-Kt~n)。在结晶的后期,由介电性质的频率谱Cole-Cole图观察介电松弛强度△ε和β参数在结晶过程的变化。     

Synthesis of Polysiloxane-Bound (Ether-phosphine)palladium Complexes. Stoichiometric and Catalytic Reactions in Interphases(1)

The reaction of two equiv of the monomeric ether-phosphine O,P ligand (MeO)(3)Si(CH(2))(3)(Ph)PCH(2)-Do [1a(T(0)()), 1b(T(0)())] {Do = CH(2)OCH(3) [1a(T(0)())], CHCH(2)CH(2)CH(2)O [1b(T(0)())]} with PdCl(2)(COD) yields the monomeric palladium(II) complexes Cl(2)Pd(P approximately O)(2) [2a(T(0)())(2)(), 2b(T(0)())(2)()]. The compounds 2a(T(0)())(2)() and 2b(T(0)())(2)() are sol-gel processed with variable amounts (y) of Si(OEt)(4) (Q(0)()) to give the polysiloxane-bound complexes 2a(T(n)())(2)()(Q(k)())(y)(), 2b(T(n)())(2)()(Q(k)())(y)() (Table 1) {P approximately O = eta(1)-P-coordinated ether-phosphine ligand; for T(n)() and Q(k)(), y = number of condensed T type (three oxygen neighbors), Q type (four oxygen neighbors) silicon atoms; n and k = number of Si-O-Si bonds; n = 0-3; k = 0-4; 2a(T(n)())(2)()(Q(k)())(y)(), 2b(T(n)())(2)()(Q(k)())(y)() = {[M]-SiO(n)()(/2)(OX)(3)(-)(n)()}(2)[SiO(k)()(/2)(OX)(4)(-)(k)()](y)(), [M] = (Cl(2)Pd)(1/2)(Ph)P(CH(2)Do)(CH(2))(3)-, X = H, Me, Et}. The complexes 2b(T(n)())(2)()(Q(k)())(y)() (y = 4, 12, 36) show high activity and selectivity in the hydrogenation of 1-hexyne and tolan. The dicationic complexes [Pd(P&arcraise;O)(2)][SbF(6)](2) [3a(T(0)())(2)(), 3b(T(0)())(2)()] are formed by reacting Cl(2)Pd(P approximately O)(2) with 2 equiv of a silver salt {P&arcraise;O = eta(2)-O&arcraise;P-coordinated ether-phosphine ligand; 3a(T(0)())(2)(), 3b(T(0)())(2)() = [M]-SiOMe(3); [M] = {[Pd(2+)](1/)(2)P(Ph)(CH(2)CH(2)OCH(3))(CH(2))(3)-}{SbF(6)} (a), {[Pd(2+)](1/)(2)P(Ph)(CH(2)CHCH(2)CH(2)CH(2)O)(CH(2))(3)-}{SbF(6)} (b)}. Their polysiloxane-bound congeners 3a(T(n)())(2)(), 3b(T(n)())(2)() {[M]-SiO(n)()(/2)(OX)(3)(-)(n)} are obtained if a volatile, reversible bound ligand like acetonitrile is employed during the sol-gel process. The bis(chelate)palladium(II) complexes 3a(T(n)())(2)(), 3b(T(n)())(2)() are catalytic active in the solvent-free CO-ethene copolymerization, producing polyketones with chain lengths comparable to those obtained with chelating diphosphine ligands. The polysiloxane-bound palladium(0) complexes 5a(T(n)())(2)()(Q(k)())(4)(), 5b(T(n)())(2)()(Q(k)())(4)() {[M]-SiO(n)()(/)(2)(OX)(3)(-)(n)}(2)[SiO(k)()(/2)(OX)(4)(-)(k)](4), [M] = [(dba)Pd](1/)(2)P(Ph)(CH(2)Do)(CH(2))(3)-} undergo an oxidative addition reaction with iodobenzene in an interphase with formation of the complexes PhPd(I)(P approximately O)(2).4SiO(2) [6a(T(n)())(2)()(Q(k)())(4)(), 6b(T(n)())(2)()(Q(k)())(4)()] {[M]-SiO(n)()(/)(2)(OX)(3)(-)(n)](2)[SiO(k)()(/2)(OX)(4)(-)(k)](4), [M] = [PhPd(I)](1/2)P(Ph)(CH(2)Do)(CH(2))(3)-}, which insert carbon monoxide into the palladium-aryl bond even in the solid state.     

Electron and nuclear dynamics of molecular clusters in ultraintense laser fields. IV. Coulomb explosion of molecular heteroclusters

In this paper we present a theoretical and computational study of the temporal dynamics and energetics of Coulomb explosion of (CD4)(n) and (CH4)(n) (n=55-4213) molecular heteroclusters in ultraintense (I=10(16)-10(19) W cm(-2)) laser fields, addressing the manifestation of electron dynamics, together with nuclear energetic and kinematic effects on the heterocluster Coulomb instability. The manifestations of the coupling between electron and nuclear dynamics were explored by molecular dynamics simulations for these heteroclusters coupled to Gaussian laser fields (pulse width tau=25 fs), elucidating outer ionization dynamics, nanoplasma screening effects (being significant for I< or =10(17) W cm(-2)), and the attainment of cluster vertical ionization (CVI) (at I=10(17) W cm(-2) for cluster radius R(0)< or =31 A). Nuclear kinematic effects on heterocluster Coulomb explosion are governed by the kinematic parameter eta=q(C)m(A)/q(A)m(C) for (CA(4))(n) clusters (A=H,D), where q(j) and m(j) (j=A,C) are the ionic charges and masses. Nonuniform heterocluster Coulomb explosion (eta >1) manifests an overrun effect of the light ions relative to the heavy ions, exhibiting the expansion of two spatially separated subclusters, with the light ions forming the outer subcluster at the outer edge of the spatial distribution. Important features of the energetics of heterocluster Coulomb explosion originate from energetic triggering effects of the driving of the light ions by the heavy ions (C(4+) for I=10(17)-10(18) W cm(-2) and C(6+) for I=10(19) W cm(-2)), as well as for kinematic effects. Based on the CVI assumption, scaling laws for the cluster size (radius R(0)) dependence of the energetics of uniform Coulomb explosion of heteroclusters (eta=1) were derived, with the size dependence of the average (E(j,av)) and maximal (E(j,M)) ion energies being E(j,av)=aR(0) (2) and E(j,M)=(5a/3)R(0) (2), as well as for the ion energy distributions P(E(j)) proportional to E(j) (1/2); E(j)< or =E(j,M). These results for uniform Coulomb explosion serve as benchmark reference data for the assessment of the effects of nonuniform explosion, where the CVI scaling law for the energetics still holds, with deviations of the a coefficient, which increase with increasing eta. Kinematic effects (for eta>1) result in an isotope effect, predicting the enhancement (by 9%-11%) of E(H,av) for Coulomb explosion of (C(4+)H(4) (+))(eta) (eta=3) relative to E(D,av) for Coulomb explosion of (C(4+)D(4) (+))(eta) (eta=1.5), with the isotope effect being determined by the ratio of the kinematic parameters for the pair of Coulomb exploding clusters. Kinematic effects for nonuniform explosion also result in a narrow isotope dependent energy distribution (of width DeltaE) of the light ions (with DeltaE/E(H,av) approximately 0.3 and DeltaE/E(D,av) approximately 0.4), with the distribution peaking at the high energy edge, in marked contrast with the uniform explosion case. Features of laser-heterocluster interactions were inferred from the analyses of the intensity dependent boundary radii (R(0))(I) and the corresponding average D+ ion energies (E(D,av))(I), which provide a measure for optimization of the cluster size at intensity I for the neutron yield from dd nuclear fusion driven by Coulomb explosion (NFDCE) of these heteroclusters. We infer on the advantage of deuterium containing heteronuclear clusters, e.g., (CD4)(n) in comparison to homonuclear clusters, e.g., (D2)(n/2), for dd NFDCE, where the highly charged heavy ions (e.g., C4+ or C6+) serve as energetic and kinematic triggers driving the D+ ions to a high (10-200 keV) energy domain.     

Thermochemistry of key soot formation intermediates: C3H3 isomers

Accurate standard enthalpies of formation for allene, propyne, and four C3H3 isomers involved in soot formation mechanisms have been determined through systematic focal point extrapolations of ab initio energies. Auxiliary corrections have been applied for anharmonic zero-point vibrational energy, core electron correlation, the diagonal Born-Oppenheimer correction (DBOC), and scalar relativistic effects. Electron correlation has been accounted for via second-order Z-averaged perturbation theory (ZAPT2) and primarily through coupled-cluster theory, including single, double, and triple excitations, as well as a perturbative treatment of connected quadruple excitations [ROCCSD, ROCCSD(T), ROCCSDT, and UCCSDT(Q)]. The correlation-consistent hierarchy of basis sets, cc-pVXZ (X = D, T, Q, 5, 6), was employed. The CCSDT(Q) corrections do not exceed 0.12 kcal mol(-)1 for the relative energies of the systems considered here, indicating a high degree of electron correlation convergence in the present results. Our recommended values for the enthalpies of formation are as follows: Delta(f)H(o)(0)(propargyl) = 84.76, Delta(f)H(o)(0) (1-propynyl) = 126.60, Delta(f)H(o)(0) (cycloprop-1-enyl) = 126.28, Delta(f)H(o)(0)(cycloprop-2-enyl) = 117.36, Delta(f)H(o)(0)(allene) = 47.41, and Delta(f)H(o)(0)(propyne) = 46.33 kcal mol(-1), with estimated errors no larger than 0.3 kcal mol(-1). The corresponding C3H3 isomerization energies are about 1 kcal mol(-1) larger than previous coupled-cluster results and several kcal mol(-1) below those previously obtained using density functional theory.     

Dynamics of (H(-), H(2)) collisions: a time-dependent quantum mechanical investigation on a new ab initio potential energy surface

A global analytical potential energy surface for the ground state of H(3)(-) has been constructed by fitting an analytic function to the ab initio potential energy values computed using coupled cluster singles and doubles with perturbative triples [CCSD(T)] method and Dunning's augmented correlation consistent polarized valence triple zeta basis set. Using this potential energy surface, time-dependent quantum mechanical wave packet calculations were carried out to calculate the reaction probabilities (P(R)) for the exchange reaction H(-)+H(2)(v, j)-->H(2)+H(-), for different initial vibrational (v) and rotational (j) states of H(2), for total angular momentum equal to zero. With increase in v, the number of oscillations in the P(R)(E) plot increases and the oscillations become more pronounced. While P(R) increases with increase in rotational excitation from j=0 to 1, it decreases with further increase in j to 2 over a wide range of energies. In addition, rotational excitation quenches the oscillations in P(R)(E) plots.     

Synthesis and reactivity of W3Te74+ clusters and chalcogen exchange in the M3Q7 (M = Mo, W; Q = S, Se, Te) cluster family

Heating WTe(2), Te, and Br(2) at 390 degrees C followed by extraction with KCN gives [W(3)Te(7)(CN)(6)](2-). Crystal structures of double salts Cs(3.5)K{[W(3)Te(7)(CN)(6)]Br}Br(1.5).4.5H(2)O (1), Cs(2)K(4){[W(3)Te(7)(CN)(6)](2)Cl}Cl.5H(2)O (2), and (Ph(4)P)(3){[W(3)Te(7)(CN)(6)]Br}.H(2)O (3) reveal short Te(2)...X (X = Cl, Br) contacts. Reaction of polymeric Mo(3)Se(7)Br(4) with KNCSe melt gives [Mo(3)Se(7)(CN)(6)](2-). Reactions of polymeric Mo(3)S(7)Br(4) and Mo(3)Te(7)I(4) with KNCSe melt (200-220 degrees C) all give as final product [Mo(3)Se(7)(CN)(6)](2)(-) via intermediate formation of [Mo(3)S(4)Se(3)(CN)(6)](2-)/[Mo(3)SSe(6)(CN)(6)](2-) and of [Mo(3)Te(4)Se(3)(CN)(6)](2-), respectively, as was shown by ESI-MS. (NH(4))(1.5)K(3){[Mo(3)Se(7)(CN)(6)]I}I(1.5).4.5H(2)O (4) was isolated and structurally characterized. Reactions of W(3)Q(7)Br(4) (Q = S, Se) with KNCSe lead to [W(3)Q(4)(CN)(9)](5-). Heating W(3)Te(7)Br(4) in KCNSe melt gives a complicated mixture of W(3)Q(7) and W(3)Q(4) derivatives, as was shown by ESI-MS, from which E(3)[W(3)(mu(3)-Te)(mu-TeSe)(3)(CN)(6)]Br.6H(2)O (5) and K(5)[W(3)(mu(3)-Te)(mu-Se)(3)(CN)(9)] (6) were isolated. X-ray analysis of 5 reveals the presence of a new TeSe(2-) ligand. The complexes were characterized by IR, Raman, electronic, and (77)Se and (125)Te NMR spectra and by ESI mass spectrometry.     

Evaluation of blue and green absorbing proteorhodopsins as holographic materials

Transient holographic diffraction is observed for the green (GPR) and blue (BPR) absorbing proteorhodopsins (BAC31A8 and HOT75M1, respectively), as well as the GPR E108Q and BPR E110Q variants. In contrast to bacteriorhodopsin, where the metastable bR-M pair is responsible for generating diffraction, the pR and red-shifted N-like states fulfill that role in both the green and blue wild-type proteorhodopsins. The GPR E108Q and BPR E110Q variants, however, behave more similarly to their bacteriorhodopsin analogue, D96N, with diffraction arising from the PR M-state (strongly enhanced in both GPR E108Q and BPR E110Q). Of the four proteins evaluated, wild type (WT) GPR and GPR E108Q produce the highest diffraction efficiencies, etamax, at approximately 1% for a 1.7 OD sample. GPR E108Q, however, requires 1-2 orders of magnitude less laser intensity to generate eta equivalent to WT GPR and BR D96N under similar conditions (as compared to literature values). WT BPR requires lower actinic powers than GPR but diffracts only about 30% as well. BPR E110Q performs the most poorly of the four, with etamax < 0.05% for a 1.4 OD film. The Kramers-Kronig transformation and Koglenik's coupled wave theory were used to predict the dispersion spectra and diffraction efficiency for the long M-state variants. To a first approximation, the gratings formed by all samples decay upon discontinuing the 520 nm actinic beams with a time constant characteristic of the appropriate intermediate: the N-like state for WT GPR and BPR and the M-state for GPR 108Q and BPR E110Q.     

Remetalation processes upon the formation of magnetically active heterometallic sulfide-bridged clusters

The processes of formation of antiferromagnetic heterometallic trinuclear clusters Cp₂Cr₂(-SCMe₃)₂(₃-S)₂ML _n (ML _n = Re(CO)(NO), W(NO)₂, W(NO)Cl, and W(NO)(SCMe₃)) from the antiferromagnetic binuclear chromium(iii) complex Cp₂Cr₂(-SCMe₃)₂(-S) (1) and nitrosyl-containing halide derivatives of Re^I and W⁰ were considered. It is shown that adducts of1 with ML _m (ML _m = Re(NO)(CO)₂Cl₂, W(NO)₂C1₂·1, and W₂(NO)₂(CO)₄I₂) are formed at the first stage. Then they loose the CpCrHal₂ moiety and transform into the reactive remetalation products, CpCr((-SCMe₃)₂(-S)ML _x (M = Re and W). The latter complexes join the electron-deficient CpCrS moiety to generate triangular clusters. The magnetic behavior of antiferromagnetic adducts and triangular clusters is discussed, and the existence of correlations between the energy of spin-spin exchange (–2J(Cr-Cr)) and Cr-Cr and Cr-S(sulfide) bond lengths is mentioned.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2337–2348, December, 1995.     

Dipole-quadrupole and dipole-octopole polarizability of OsO4 from depolarized collision-induced light scattering experiments, ab initio and density functional theory calculations

The dipole-quadrupole and dipole-octopole polarizability of osmium tetroxide (OsO(4)) has been determined from collision-induced light-scattering experiments. Our final estimates for these properties are |A|=(84+/-5)e(2)a(3)(0)E(-1)(h) and |E|=(214+/-25)e(2)a(4)(0)E(-1)(h). We have also analyzed previous experimental data of the relative permittivity and refractivity of OsO(4) to propose the electronic part of the static dipole polarizability of alpha=51.0e(2)a(2)(0)E(-1)(h). To support our findings we have performed high-level ab initio and density functional theory calculations to obtain theoretical static estimates alpha=(50.2+/-1.6)e(2)a(2)(0)E(-1)(h), A=(84+/-10)e(2)a(3)(0)E(-1)(h), and E=(-252+/-32)e(2)a(4)(0)E(-1)(h), in essential agreement with the proposed experimental values.     

Tungsten monocarbide, WC: pure rotational spectrum and 13C hyperfine interaction

The J = 1→2 pure rotational transitions in the X(3)Δ(1)(ν = 0) state of (186)W(12)C and (184)W(12)C were recorded using a pump/probe microwave optical double resonance (PPMODR) technique and analyzed to give fine structure parameters. The field-free [17.6]2←X(3)Δ(1) (1, 0) bands of the W(13)C isotopologues were recorded using laser induced fluorescence and analyzed to produce the (13)C(I = 1/2) magnetic hyperfine parameter. Bonding in the [17.6]2(ν = 1) and X(3)Δ(1)(ν = 0) states is discussed and a comparison of the experimentally determined properties of the X(3)Δ(1)(ν = 0) state with those predicted as a prelude to the electron electric dipole moment (eEDM) measurements [J. Lee, E. R. Meyer, R. Paudel, J. L. Bohn, and A. E. Leanhardt, J. Mod. Opt. 56, 2005 (2009)] is given.     

Low-lying electronic states of M(3)O(9)(-) and M(3)O(9)(2-) (M = Mo, W)

Multiple low-lying electronic states of M(3)O(9)(-) and M(3)O(9)(2-) (M = Mo, W) arise from the occupation of the near-degenerate low-lying virtual orbitals in the neutral clusters. We used density functional theory (DFT) and coupled cluster theory (CCSD(T)) with correlation consistent basis sets to study the structures and energetics of the electronic states of these anions. The adiabatic and vertical electron detachment energies (ADEs and VDEs) of the anionic clusters were calculated with 27 exchange-correlation functionals including one local spin density approximation functional, 13 generalized gradient approximation (GGA) functionals, and 13 hybrid GGA functionals, as well as the CCSD(T) method. For M(3)O(9)(-), CCSD(T) and nearly all of the DFT exchange-correlation functionals studied predict the (2)A(1) state arising from the Jahn-Teller distortion due to singly occupying the degenerate e' orbital to be lower in energy than the (2)A(1)' state arising from singly occupying the nondegenerate a(1)' orbital. For W(3)O(9)(-), the (2)A(1) state was predicted to have essentially the same energy as the (2)A(1)' state at the CCSD(T) level with core-valence correlation corrections included and to be higher in energy or essentially isoenergetic with most DFT methods. The calculated VDEs from the CCSD(T) method are in reasonable agreement with the experimental values for both electronic states if estimates for the corrections due to basis set incompleteness are included. For M(3)O(9)(2-), the singlet state arising from doubly occupying the nondegenerate a(1)' orbital was predicted to be the most stable state for both M = Mo and W. However, whereas M(3)O(9)(2-) was predicted to be less stable than M(3)O(9)(-), W(3)O(9)(2-) was predicted to be more stable than W(3)O(9)(-).