Chemical Physics Letters (v.462, #1-3)
Editorial Board (IFC).
The effect of entropy on protein hydrogen bonds by Sheh-Yi Sheu; H.L. Selzle; E.W. Schlag; Dah-Yen Yang (1-5).
Hydrogen bonds in a typical protein environment. The effect of solvents on the reactivity.Hydrogen bonds are essential elements in protein structure and dynamics. We show that such bonds are strongly dominated by entropic contributions of the environment that can be at least as important as energetic considerations. These contributions are global in that they are not due to the internal degrees of freedom. The molecular dynamics (MD) is carried out as a computer experiment and agrees very well with the known energies of hydrogen bonds, both in water and in the isolated molecule. The entropy in water as a solvent is found to modulate the hydrogen bond breaking and reformation rate by two orders of magnitude, in a negative direction.
Circular dichroism (CD) spectroscopy of the assembly and disassembly of SNAREs: The proteins involved in membrane fusion in cells by Jeremy D. Cook; Won Jin Cho; Timothy L. Stemmler; Bhanu P. Jena (6-9).
SNAREs and their complexes in buffered suspension exhibit greater degree of secondary structure, then when incorporated in lipid membrane.In this study, we report for the first time that both t-SNAREs and v-SNARE and their complexes in buffered suspension, exhibit defined peaks at CD signals of 208 and 222 nm wavelengths, consistent with a higher degree of helical secondary structure. Surprisingly, when incorporated in lipid membrane, both SNAREs and their complexes exhibit reduced folding. In presence of NSF–ATP, the SNARE complex disassembles, as reflected from the CD signals demonstrating elimination of α-helices within the structure.
Molecular fine structure and transition dipole moment of NO2 using an external cavity quantum cascade laser by Nandini Mukherjee; C. Kumar N. Patel (10-13).
High resolution measurement of saturation dip in NO2.Rotational vibrational fine structure and transition dipole moment of NO2 is measured using Doppler free saturation spectroscopy with an external grating cavity quantum cascade laser (QCL). The QCL wavelength is calibrated using a 310 cm long internally coupled Fabry–Perot interferometer. We obtain a frequency splitting of 139.68 ± 0.06 MHz (0.0047 cm−1) between the spin doublets P 4 ± (17) of 000 → 001 transition of NO2. The resolution of the QCL based saturation spectrometer is limited by the QCL linewidth of ∼ 3.99 MHz (∼ 0.00013 cm−1) deduced from the half width of the Lamb dips. The Lamb dip spectroscopy is utilized to obtain a vibrational dipole moment of ∼0.37 Debye for the P 4 ± (17) transitions.
Femtosecond diffraction with chirped electron pulses by Peter Baum; Ahmed Zewail (14-17).
Thirty-famtosecond time resolution in ultrafast electron diffraction using a chirped electron packet and an energy filter.Here, we report on the possible achievement, in ultrafast electron diffraction and imaging, of temporal resolution of tens of femtoseconds through the use of chirped electron packets in combination with energy filtering. Space–charge forces in multi-electron packets accelerate leading electrons and retard trailing ones, thus inducing correlations of momentum and time. By resolving the diffraction images with an energy analyzer, well-defined temporal slices of the long electron packet can be selected. Numerical simulations show that conventional electron sources are sufficient to reach the 30-fs domain of resolution without electron packet compression. They also reveal the influence of packet shape, electron density and photoemission bandwidth on the achievable time resolution.
Revisiting the nature of the ZnO ground state: Influence of spin–orbit coupling by Salima Boughdiri; Bahoueddine Tangour; Christian Teichteil; Jean-Claude Barthelat; Thierry Leininger (18-22).
The nature of the ZnO ground state is revisited from a relativistic point of view.Relativistic calculations of the low-lying electronic states of the ZnO molecule are performed for the Λ–Σ states, 1Σ+, 1Π, 1Δ, 3Π and 3Σ−, at the CCSD(T) or MRCI level, using scalar relativistic energy-consistent pseudopotentials, and the EPCISO method for spin–orbit CI coupling. The ZnO ground state is assigned to 0+ symmetry and has 1Σ+ character around the equilibrium region. The spectroscopic constants (r e , ω e ) of the 0+ ground state are in good agreement with experimental results. Interpenetration of the vibrational levels of the two lowest 0+ states is also shown.
Theoretical study of low-lying electronic states of Mn2 using a newly developed relativistic model core potential by Ma San Mon; Hirotoshi Mori; Eisaku Miyoshi (23-26).
Newly developed spdsMCP basis set sufficiently describes the electronic structures of low-lying states of Mn2 in highly correlated calculations.We investigated the electronic structure of low-lying electronic states of Mn2 using a newly developed relativistic model core potential (spdsMCP). Calculations were performed at complete active space self-consistent field (CASSCF) and second-order multiconfiguration quasidegenerate perturbation theory (MCQDPT2) levels. The MCQDPT2 calculations reveal that the 1Σg+ state is the ground state. Calculated spectroscopic constants are very similar to the results of recent all-electron calculations and experimental values, indicating that the spdsMCP works well for Mn2, which requires a highly correlated calculation. The wave functions of low-lying states are also analyzed at the CASSCF level.
Intense laser-induced decomposition of mass-selected 2-, 3-, and 4-methylaniline cations by Ryuji Itakura; Takatsugu Tanaka; Mikinori Kuwata; Hideaki Suzuki; Kaoru Yamanouchi (27-30).
Decomposition schemes of the 2-, 3-, and 4-methylaniline cations via the five- and seven-membered ring intermediate compounds.Photodecomposition processes of 2-, 3-, and 4-methylaniline cations induced by a moderately intense (∼1011 W/cm2) visible nanosecond laser field and an intense (∼1015 W/cm2) UV femtosecond laser field have been investigated using a tandem mass spectrometer. Highly unsaturated fragment cations such as C 6 H 2 + and C 6 H 3 + are dominantly produced by the nanosecond laser, while less unsaturated smaller fragment cations such as C 3 H 3 + , C 4 H 4 + , and C 5 H 5 + are produced mainly by the femtosecond laser. Ab initio calculations have also been performed to estimate the stable geometrical structures of C 6 H 2 + and C 6 H 3 + and those of possible intermediate ring compounds for discussing the photodecomposition pathways in intense laser fields.
Deep-UV absorption and Rayleigh scattering of carbon dioxide by D. Ityaksov; H. Linnartz; W. Ubachs (31-34).
Deep-UV cavity ring-down spectroscopy and pressure ramps measurements in CO2 at room temperature provide extinction coefficients showing an absorption onset below 202 nm. For longer wavelengths it is found that the optical extinction demonstrates a 1/λ 4 like behavior, as typical for Rayleigh scattering.Cavity ring-down spectroscopy and pressure ramp measurements have been used to determine the extinction coefficients of CO2 in the deep-ultraviolet wavelength region, between 198 and 270 nm. The observed optical extinction confirms that there is a clear absorption onset of CO2 in the deep-UV wavelength region. This onset has been reported previously around 205 nm. The new set of measurements presented here shows that the onset actually starts at higher energy, around 202 nm. For longer wavelengths it is found that the optical extinction demonstrates a 1/λ 4 like behavior, as typical for Rayleigh scattering.
Photoelectron spectroscopic study of iron–benzene cluster anions by Weijun Zheng; Soren N. Eustis; Xiang Li; John M. Nilles; Owen C. Thomas; Kit H. Bowen; Anil K. Kandalam (35-39).
Iron–benzene cluster anions, Fe n Bz m - (n = 1–7, m = 1–4), were studied using mass spectrometry, anion photoelectron spectroscopy and by density functional theory.Iron–benzene cluster anions, Fe n Bz m - (n = 1–7, m = 1–4), were generated via laser vaporization and studied using mass spectrometry, anion photoelectron spectroscopy and in one case by density functional theory. Based on these studies, we propose that Fe 1 Bz 1 - and Fe1Bz1 as well as Fe 2 Bz 1 - and Fe2Bz1 exhibit half-sandwich structures, that Fe 1 Bz 2 - and Fe1Bz2, Fe 2 Bz 2 - and Fe2Bz2, as well as Fe3Bz2 and Fe4Bz2 are sandwich structures, and that Fe 2 Bz 3 - and Fe2Bz3 and larger species form ‘rice-ball’ structures which in each case consist of benzene molecules surrounding an iron cluster core.
Specific fragmentation of [(CH3)2CO]Ar n heteroclusters induced by the Ar L23- and O K-shell excitation by Y. Tamenori; K. Okada; K. Tabayashi; T. Gejo; K. Honma (40-44).
The selective O+ formation has been confirmed at the O 1s → π∗(C＝O) resonance excitation of [(CH3)2CO]Ar n heteroclusters.Ionic fragmentation following the inner-shell photoexcitation of [(CH3)2CO]Ar n heteroclusters was investigated in the Ar L23- and O K-edge regions. A partial ion yield (PIY) measurement revealed that Ar n + and various acetone fragments ( H m + , CH m + , C 2 H m + , C 3 H m + , and CH m CO + ) were produced following the Ar L23-shell excitation. In the O K-edge region, the PIY of O+ exhibited a sharp resonance peak at the O 1s → π∗(C＝O) resonance excitation. The selective O+ formation was interpreted as the suppression of statistical fragmentation, which was dominant in isolated acetone, owing to the dissipation of excess energy into Ar clusters.
Cation–π complexes formed between cyclooctatetraene and alkaline earth metals: Predicted and recorded NMR features by Lingyan He; Jiagao Cheng; Tao Wang; Caimei Li; Zhen Gong; Hong Liu; Bu-Bing Zeng; Hualiang Jiang; Weiliang Zhu (45-48).
The experimentally recorded and theoretically predicted NMR data reveal that the complexes between COT and alkaline earth metal atoms do exist.The complexes formed by cyclooctatetraene (COT) and alkaline earth metals were theoretically studied but without convincible experimental evidence. To validate very strong cation–π interaction in the complexes, the NMR properties are experimentally recorded and theoretically calculated in this study. The good agreement between the recorded 13C NMR data and all the calculated results, including NMR chemical shift, interaction distances and strength, and atomic charge in DMSO at different theoretical levels by PCM method, strongly indicates that the complexes between COT and alkaline earth metal atoms do exist via strong cation–π interaction.
A critical analysis of the structure and vibrational frequencies of F2NO+ and Cl2NO+ from accurate quantum chemical computations by Cristina Puzzarini; Vincenzo Barone (49-52).
State-of-the-art ab initio calculations: accurate equilibrium structure and vibrational spectra of F2NO+ and Cl2NO+.The structures and vibrational spectra of the title compounds have been computed by the coupled cluster approach using a hierarchical series of basis sets. The theoretical and experimental results are in good agreement for F2NO+, whereas this is not the case for Cl2NO+. We therefore suggest an experimental reinvestigation of the salt compound containing Cl2NO+.
Quasiclassical trajectory scattering calculations for the OH + O → H + O2 reaction: Cross sections and rate constants by M. Jorfi; P. Honvault; P. Halvick; S.Y. Lin; H. Guo (53-57).
Comparison of temperature dependence between the theoretical and experiment rate constants for the O + OH reaction.We report quasiclassical trajectory studies of the OH + O → H + O2 reaction using a recently developed ab initio potential energy surface for the ground electronic state of HO2. The J = 0 total reaction probability is in good agreement with the quantum result. Integral cross sections show no energy threshold and decrease as the collision energy increases. Rate constants have been calculated in the (1–500 K) temperature range. They exhibit a negative temperature dependence for temperatures above 50 K, and the thermal rate constant is in quantitative agreement with the most recent experimental data. The reactivity is slightly enhanced by rotational excitation of OH.
Photochemical reaction and diffusion of caged calcium studied by the transient grating by Masato Kondoh; Naoki Baden; Masahide Terazima (58-63).
A photoreaction of caged calcium was investigated by using the time-resolved transient grating method. The q 2-dependent feature of the TG signal was analyzed based on a model that there are two parallel dissociation steps with different rates and Ca2+ is released promptly after the fracture of the caged compound. The diffusion coefficients of the caged compound and Ca2+ are determined.A photoreaction of caged calcium (Ca2+) was investigated by using the time-resolved transient grating (TG) method. The q 2-dependent feature of the TG signal was analyzed based on a model that there are two parallel dissociation steps with different rates and Ca2+ is released promptly after the fracture of the caged compound. The TG signal representing the presence of Ca2+ was appeared by the volume contribution. Although the diffusion coefficients of Cg and the decomposed product are different without Ca2+, only one diffusion component was observed after the dissociation of CgCa2+, indicating that the caged compounds and Ca2+ diffuse together.
Turbulent states in a reaction-diffusion system with period-doubling bifurcations by E. Purlis; I.M. Irurzun; E.E. Mola (64-68).
Bifurcation diagram of the Hastings–Powell model showing the period-doubling route to chaos.We investigate the spatially extended Hastings–Powell model in one and two dimensions with constant diffusion coefficients and nonflux boundary conditions. Nowave zones, spirals and chaos are found. An absolute instability of the spirals produces a transition to chaos. A constant number of defects, linearly increasing with the bifurcation parameter of the system is found, i.e. there do not exist defect-creation or defect-destruction events. Defects behave as hard disks, with translational degrees of freedom, which result from a cooperative interaction between pairs of defects.
Large optical Kerr effect in bulk GeSe2–In2Se3–CsI chalcohalide glasses by Yinsheng Xu; Qiming Zhang; Wei Wang; Huidan Zeng; Lei Xu; Guorong Chen (69-71).
Time-resolved optical Kerr signal of the chalcohalide glass, the obtained largest n 2 is 6.5 × 10−18 m2/W, more than twice that of As2S3 glass.Third-order nonlinear optical properties of GeSe2–In2Se3–CsI chalcogenide bulk glasses are studied by Standard pico-second (ps) time-resolved optical Kerr effect (OKE) technique. The obtained χ (3) and n 2 at 1064 nm of the glass 72.25GeSe2–23.75In2Se3–5CsI are as large as 10.07 × 10−12 esu and 6.5 × 10−18 m2/W, respectively, more than twice that of As2S3 glass. The relationship between glass compositions and the third-order nonlinear optical responses was analyzed by Raman spectra in terms of structural evolution. It is suggested that the tetrahedral units ([GeSe4] and [InSe4]) play an important role in the ultrafast third-order nonlinear optical responses of these chalcohalide glasses.
C60 as a chemical Faraday cage for three ferromagnetic Fe atoms by Guohua Gao; Hong Seok Kang (72-74).
Based on calculations using density functional theory, we find that C60 can encapsulate a highly magnetic and highly reactive Fe3 cluster.Based on calculations using density functional theory, we show that C60 can act as a chemical Faraday cage in which a highly magnetic metal cluster with a high chemical reactivity can be encapsulated. As an example, we find that C60 can encapsulate a Fe3 cluster, while it is much less likely to encapsulate a Fe2 cluster. Spin multiplicity (=9) of the Fe3@C60 is very high, being comparable to that (=11) of a free Fe3 cluster. Geometrically, the triangular plane of the cluster is perpendicular to a S 6 axis of the fullerene.
Analysis of laser-induced breakdown images measuring the sizes of mixed aquatic nanoparticles by J.W. Kim; J.A. Son; J.I. Yun; E.C. Jung; S.H. Park; J.G. Choi (75-77).
An improvement of accuracy in measuring sizes of aquatic colloidal nanoparticles is presented by utilizing the laser-induced breakdown detection.Sizes of aquatic colloidal nanoparticles are determined by utilizing the laser-induced breakdown detection technique. Specifically, the number of breakdown events is measured as a function of area in laser-induced plasma images, generated from a mixture of two different size nanoparticles in aqueous solution, by minimizing the energy of the incident laser irradiation to generate the plasma. We find that the accuracy of measuring the sizes of nanoparticles in mixtures is greatly improved when selecting the plasma images produced only within one-half of the Rayleigh range of the focused Gaussian beam where the irradiation is most uniformly distributed.
Evidence of magnetic ordering of paramagnetic surface defects on partially hydroxylated MgO nanocrystals by Ibério de P.R. Moreira; Jacek C. Wojdeł; Francesc Illas; Mario Chiesa; Elio Giamello (78-83).
EPR measurements and DFT calculations show evidence of antiferromagnetic ordering of trapped electrons on partially hydroxylated MgO nanocrystals.EPR experiments carried out at various temperatures for partially hydroxylated nanocrystalline MgO exposed to atomic hydrogen reveal that the entrapped electrons arising from spontaneous dissociation of hydrogen atoms exhibit an antiferromagnetic ordering. The measured magnetic data is found to be compatible with a phenomenological model of interacting paramagnetic centres at high temperature, and with a Pauli like behaviour below a certain temperature. This is further corroborated with density functional calculations of the effective magnetic coupling parameter for Heisenberg model between entrapped electrons on suitable embedded cluster models of MgO nanocrystals.
An improved method for chemical bath deposition of ZnS thin films by Fei Long; Wei-Min Wang; Zhan-kui Cui; Li-Zhen Fan; Zheng-guang Zou; Tie-kun Jia (84-87).
The film deposited by original method (a) and by improved method (b).ZnS thin films were prepared by an improved chemical bath deposition method, which the substrates were preheated before being mounted in the reaction solution. X-ray diffraction (XRD) and energy dispersive spectrometer (EDS) reveals that thin film ZnS has a cubic structure and the typical composition ratio of Zn/S is 52:48. Scanning electron microscopy (SEM) characterization shows that the surface of the sample is compact and uniform. The transmission spectrum indicates a good transmission characteristic with an average transmittance of 82.2% in the spectra range from 350 nm to 800 nm and the optical band gap is about 3.76 eV.
Efficient resonance energy transfer from dye to Au@SnO2 core–shell nanoparticles by Krishna Kanta Haldar; Amitava Patra (88-91).
The present study reports the efficient fluorescence resonance energy transfer from Rhodamine 6G dye to Au@SnO2 core–shell nanoparticles.The present study reports the shell thickness dependence fluorescence resonance energy transfer between Rhodamine 6G dye and Au@SnO2 core–shell nanoparticles. There is a pronounced effect on the PL quenching and shortening of the lifetime of the dye in presence of Au@SnO2 core–shell nanoparticles. The calculated energy transfer efficiencies from dye to Au@SnO2 are 64.4% and 78.3% for 1.5 nm and 2.5 nm thickness of shell, respectively. Considering the interactions of single acceptor and multiple donors, the calculated average distances (r n) are 75.8 and 71.5 Å for 1.5 nm and 2.5 nm thick core–shell Au@SnO2 nanoparticles, respectively.
Oxygen-assisted shape control in polyol synthesis of silver nanocrystals by Atsushi Taguchi; Shintaro Fujii; Taro Ichimura; Prabhat Verma; Yasushi Inouye; Satoshi Kawata (92-95).
The shape of silver nanocrystals is conveniently controlled by injection of oxygen gas during the polyol reduction of silver ions.We have found that the shape of silver nanocrystals is conveniently controlled by injection of oxygen gas during the polyol reduction of silver ions. The presence of oxygen effectively promotes the oxidative etching of multiple twined particles. Adjusting the flow rate of the oxygen gas yields uniformly-sized silver nanocubes, right bipyramids, nanowires, and spherical nanoparticles depending on the injection rate of the oxygen gas. Electron diffraction and high resolution TEM observations of the synthesized nanocrystals show our nanocrystals do consist of silver, not of silver oxide. SERS activities of the synthesized nanocrystals were also examined.
One-pot synthesis and magnetic, electrical properties of single-crystalline α-MnS nanobelts by Dekun Ma; Shaoming Huang; Lijie Zhang (96-99).
A facile one-pot solvothermal route for large-scale synthesis of α-MnS single-crystalline nanobelts showing unique magnetic and electrical properties.α-MnS single-crystalline nanobelts were synthesized for the first time on a large scale by solvothermal method in monosurfactant dodecylamine system. The investigation of magnetic properties shows antiferromagnetic transition temperature of as-synthesized α-MnS nanobelts is remarkably lower than that of bulk counterparts (152 K) and higher than that of corresponding nanoparticles (18 K). These single-crystalline α-MnS nanobelts exhibit higher coercivity (4013 Oe) than those of reported MnS nanowires (1020 Oe) and nanoparticles (330 Oe). The study on electrical transport shows that the conductivity of individual α-MnS nanobelt is as high as 3.2 × 105 S/m.
Exciton states of quantum confined ZnO nanorods by Sun Young Kim; Yun Seon Yeon; Seung Min Park; Jeong Hyun Kim; Jae Kyu Song (100-103).
The exciton states remain relatively stable at a high carrier density due to a smaller exciton size and an enhanced exciton binding energy in the quantum confined nanorods.Photoluminescence (PL) of zinc oxide (ZnO) nanorods with an average thickness of 5 nm and a length of 30 nm is blue-shifted compared to the bulk due to quantum confinement effects. The exciton states remain relatively stable at a high carrier density due to a smaller exciton size and an enhanced exciton binding energy in the quantum confined nanorods, whereas the electron-hole plasma states are formed in the bulk at the similar carrier density. A linear dependence of the PL intensity on the excitation intensity also corroborates the assumption that the stable exciton states are responsible for the undisturbed emission at a high carrier density.
Formation and coalescence of linear chains in growth of nanostructured sp–sp2 amorphous carbon films by Tian-Bao Ma; Yuan-Zhong Hu; Hui Wang (104-108).
Formation and coalescence of linear chains in growth of nanostructured sp–sp2 amorphous carbon films by atom-by-atom deposition.Formation and coalescence of linear chains are studied in low-energy atom-by-atom deposition of nanostructured sp–sp2 amorphous carbon films. At the energy of 1 eV, the adsorption of incident atoms on the top of the surface atoms and on the top of existing chain-tips prevails, which explains the initial nucleation and the elongation of sp linear chain structures. During the whole growth process, the film experiences a transition from a sp-dominated linear chain structure to a sp2-dominated network structure. This transition happens when linear chains get instable beyond the critical length limit, and coalesce into the three-dimensional network structure.
Optical study of porphyrin-doped carbon nanotubes by G.A.M. Sáfar; H.B. Ribeiro; L.M. Malard; F.O. Plentz; C. Fantini; A.P. Santos; G. de Freitas-Silva; Y.M. Idemori (109-111).
Porphyrin-doped carbon nanotubes in NaDDBS aqueous solution were obtained from NaDDBS/carbon nanotube aqueous dispersions.Porphyrin-doped carbon nanotubes in sodium dodecylbenzenesulfonate (NaDDBS) aqueous solution were obtained from NaDDBS/carbon nanotube aqueous dispersions. Several phonon-assisted absorption and recombination processes seem to occur, including one-phonon and two-phonon processes, and remain present even upon porphyrin doping. Power-law scaling of exciton binding energies and environmental dielectric screening effects are used to infer the doping from photoluminescence maps. The dielectric constant of the 5,10,15,20-tetrakis(4-trimethylammonium phenyl) porphyrin (H2TTMAPP) in NaDDBS aqueous solution seems to be higher than the one of NaDDBS/aqueous solution apparently because the counterions have opposite net charges.
Free-energy change of inserting halothane into different depths of a hydrated DMPC bilayer by P.-L. Chau; K.-M. Tu; K.K. Liang; S.L. Chan; Nobuyuki Matubayasi (112-115).
Free-energy change of insertion of halothane into different depths of DMPC membranes at different pressuresUsing the method of energy representation, we have calculated the free-energy change of inserting a halothane molecule into different depths of a hydrated dimyristoylphosphatidylcholine (DMPC) bilayer at pressures of 10 5 Pa to 4 × 10 7 Pa . Our results show that the free-energy change is more negative within the membrane than in bulk water. The halothane distribution is diffuse, and the preferred location is near the headgroup. The pressure effect is found to be minimal within the pressure range examined, which corresponds to previous biological experimental conditions.
Carbon- and nitrogen-centered radicals produced from l-lysine by radiation-induced oxidation: A pulse radiolysis study by Takeo Ito; Shota Morimoto; Shin-ichi Fujita; Kazuo Kobayashi; Seiichi Tagawa; Sei-ichi Nishimoto (116-120).
Reaction of l-lysine with • OH generates C-centered radicals as major intermediates, whereas oxidation by SO 4 - • yields the ε-N-centered radical.Radical species generated from the reactions of a basic amino acid, l-lysine (Lys), with hydroxyl radicals ( • OH) and sulfate radical anion ( SO 4 - • ) have been detected by the method of pulse radiolysis. On the basis of electron transfer reactivities toward tetranitromethane (TNM), it was demonstrated that reducing carbon-centered radicals are generated as a result of hydrogen abstraction from CH2 of Lys with a G-value of 1.9 × 10−7 mol J−1. On the other hand, direct oxidation of l-Lys by SO 4 - • formed a transient species with different spectroscopic properties, most likely, the ε-N-centered Lys radical.
Ultrafast fluorescence dynamics of FMN-binding protein from Desulfovibrio vulgaris (Miyazaki F) and its site-directed mutated proteins by Haik Chosrowjan; Seiji Taniguchi; Noboru Mataga; Fumio Tanaka; Daisuke Todoroki; Masaya Kitamura (121-124).
Fluorescence dynamics of FMN binding protein drastically change in W32Y and W32A mutants due to quencher’s ionization potentials and averaged donor–acceptor distances.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.
Quantification of cross polarization with relaxation compensated reciprocity relation in NMR by Jie Shu; Qun Chen; Shanmin Zhang (125-128).
Computer simulated reciprocity relation between the dynamics of cross polarization (CP) and cross depolarization (CDP) for a powder sample under fast magic angle spinning (MAS = 40 kHz). The symmetrical pattern between CP(t) and CDP(t) manifests the quantification of cross polarization under fast MAS. In the simulation, the dipolar coupling constant for a 1H–13C spin pair is d = 25.37 kHz and the RF spin-locking fields f 1 I and f 1 S are 140 and 100 kHz, respectively.The reciprocity relation in solid state NMR has been extended to include the effects of spin-lattice relaxation in the rotating frame. This method was successfully applied to the experiments of Hartmann–Hahn cross polarization, making the originally non-quantified NMR spectra quantitative. In addition, it provides detailed dynamics of cross polarization that is often obscured by spin-lattice relaxation in the rotating frame and by some other effects.
H–L curve: A novel 2D graphical representation for DNA sequences by Guohua Huang; Bo Liao; Yongfan Li; Zanbo Liu (129-132).
A 2D graphical representation of DNA sequences without degeneracy is presented, which allows a visual inspection of sequences.By assigning to four kinds of basic nucleotide A, T, G and C, respectively, four different two-component vectors, in which the first elements are constant (equal to 1) and the second elements are different from each other, we presented a 2D graphical representation of DNA primary sequences, which is mathematically proven to be not any circuit and associated with DNA sequences in a one-to-one manner and whose advantage is that it helps in identifying major difference among similar DNA sequences. Making use of the presented graphical representation, we analyzed DNA mutations between sequences.
Local structural properties of (NiF6)4− clusters in perovskite fluorides RbMF3 (M = Cd2+, Ca2+, Mg2+) series: EPR and optical spectra study in tetragonal and trigonal ligand field by Hui-Fang Li; Xiao-Yu Kuang; Huai-Qian Wang (133-137).
Local structural studies of (NiF6)4− clusters in perovskite fluorides RbMF3 (M = Cd2+, Ca2+, Mg2+) series based on the EPR and optical spectra in tetragonal and trigonal ligand field.By analyzing EPR and optical spectra, the local lattice structures of (NiF6)4− clusters in perovskite fluorides RbMF3 (M = Cd2+, Ca2+, Mg2+) series in tetragonal and trigonal ligand field are studied. A compression distortion relative to the regular octahedron for the RbCdF3:Ni2+ and RbCaF3:Ni2+ systems is determined. Furthermore, on the basis of the complete energy matrices we found that ZFS parameter D dependence on spin–orbit coupling coefficient ζ is not a strictly quadratic relation as shown by the fourth-order perturbation formula. Finally, the curves of g ∥ versus k and g ⊥ versus k for these three systems are plotted which satisfy an approximately linear relation.
Bonding trends in M＝CH2 systems: Simple orbital interpretation and evidence for double bonds by Luiz Guilherme M. de Macedo; Pekka Pyykkö (138-143).
B3LYP calculations at relativistic pseudopotential or full-Dirac level are reported for 44 species of type M＝CH2 between Z = 19 and Z = 111 to obtain material for double-bond covalent radii.M＝CH2 systems, where M is a metal from 4th up to 7th period, are studied at DFT level using B3LYP functional and small-core quasirelativistic pseudopotential or fully relativistic four-component methodology. We obtained structural data for 44 elements, M, and our results can be used to infer double-bond lengths for these elements. Our results also suggest that the bonding of these M＝CH2 systems can be understood by a simple pictorial approach, even when spin–orbit effects are present.