Stereoselective synthesis of vinylgermanes and their facile transformation into vinyl halides

Whereas iododegermylation of (Z)-1-triethylgermyl-1-dodecene gives (Z)-1-iodo-1-dodecene, bromodegermylation proves to give (E)-1-bromo-1-dodecene. Two general procedures for the preparation of vinylgermanes are also described.     

Designer variable repeat length polypeptides as scaffolds for surface immobilization of quantum dots

We demonstrate the use of a series of engineered, variable-length de novo polypeptides to discretely immobilize luminescent semiconductor nanocrystals or quantum dots (QDs) onto functional surfaces. The polypeptides express N-terminal dicysteine and C-terminal hexahistidine residues that flank a variable number (1, 3, 5, 7, 14, 21, 28, or 35) of core beta-strand repeats, with tyrosine, glutamic acid, histidine, and lysine residues located at the turns. Polypeptides have molecular weights ranging from 4 to 83 kDa and retain a rigid structure based on the antiparallel beta-sheet motif. We first use a series of dye-labeled polypeptides to test and characterize their self-assembly onto hydrophilic CdSe-ZnS QDs using fluorescence resonance energy transfer (FRET). Results indicate that peptides maintain their beta-sheet conformation after self-assembly onto the QD surfaces, regardless of their length. We then immobilize biotinylated derivatives of these polypeptides on a NeutrAvidin-functionalized substrate and use them to capture QDs via specific interactions between the peptides' polyhistidine residues and the nanocrystal surface. We found that each of the polypeptides was able to efficiently capture QDs, with a clear correlation between the density of the surface-tethered peptide and the capacity for nanocrystal capture. The versatility of this capture strategy is highlighted by the creation of a variety of one- and two-dimensional polypeptide-QD structures as well as a self-assembled surface-immobilized FRET-based nutrient sensor.     

Molecular dynamics simulations of large integral membrane proteins with an implicit membrane model

The heterogeneous dielectric generalized Born (HDGB) methodology is an the extension of the GBMV model for the simulation of integral membrane proteins with an implicit membrane environment. Three large integral membrane proteins, the bacteriorhodopsin monomer and trimer and the BtuCD protein, were simulated with the HDGB model in order to evaluate how well thermodynamic and dynamic properties are reproduced. Effects of the truncation of electrostatic interactions were examined. For all proteins, the HDGB model was able to generate stable trajectories that remained close to the starting experimental structures, in excellent agreement with explicit membrane simulations. Dynamic properties evaluated through a comparison of B-factors are also in good agreement with experiment and explicit membrane simulations. However, overall flexibility was slightly underestimated with the HDGB model unless a very large electrostatic cutoff is employed. Results with the HDGB model are further compared with equivalent simulations in implicit aqueous solvent, demonstrating that the membrane environment leads to more realistic simulations.     

Existence of densities of solutions of stochastic differential equations by Malliavin calculus

I considered if solutions of stochastic differential equations have their density or not when the coefficients are not Lipschitz continuous. However, when stochastic differential equations whose coefficients are not Lipschitz continuous, the solutions would not belong to Sobolev space in general. So, I prepared the class Vh which is larger than Sobolev space, and considered the relation between absolute continuity of random variables and the class Vh. The relation is associated to a theorem of N. Bouleau and F. Hirsch. Moreover, I got a sufficient condition for a solution of stochastic differential equation to belong to the class Vh, and showed that solutions of stochastic differential equations have their densities in a special case by using the class Vh.     

Raman Scattering Intensities of the NO2 Symmetric Stretching Vibration Band of Some Aromatic Nitrocompounds

Raman scattering intensities of the NO₂ symmetric stretching vibration band were measured for some aromatic nitrocompounds. It was shown that in the case of ortho alkyl-substituted nitrobenzenes, the intensities decrease in an orderly fashion with the increase of the degrees of twisting of NO₂ group from the plane of benzene ring. From this result, it was assumed that the factor determining the intensities in question is the conjugation effect between NO₂ group and benzene ring. Then, the intensities for some para substituted nitrobenzenes were examined, and the influence of substituents was discussed in terms of the conjugation effect. It was shown that when the electron donating character of substituents becomes stronger, the intensities intensity change among the compounds. The more experimental data and the detailed theoretical analysis of them are necessary not only for the elucidation of spectroscopic aspects of the intensity in question, but also for establishing the criterion for the application of it to the group type analysis and the microanalysis. Therefore, further experimental and theoretical examinations are required and now proceeding in our laboratory.     

Raman Scattering Intensities of the NO2 Symmetric Stretching Vibration Band of Some Aromatic Nitrocompounds (II)

The Raman scattering intensities of the NO₂ symmetric stretching vibration band were investigated experimentally for some para and meta substituted nitrobenzenes. The excitation profiles obtained with the six excitation wavelengths from 457.9 to 514.5 nm were presented. The results were examined in terms of the Albrecht-Hutley's theory, and the electronic states involved in the preresonance Raman intensity enhancement were suggested.     

Extending spin-symmetry projected coupled-cluster to large model spaces using an iterative null-space projection technique

Recently, we introduced an orbital-invariant approximate coupled-cluster (CC) method in the spin-projection manifold. The multi-determinantal property of spin-projection means that the parametrization in the spin-extended CC (ECC) ansatz is nonorthogonal and overcomplete. Therefore, the linear dependencies must be removed by an orthogonalization procedure to obtain meaningful solutions. Multi-reference methods often achieve this by diagonalizing a metric of the equation system, but this is not feasible with ECC because of the enormous size of the metric, a consequence of the incomplete active space of the spin-projected Hartree–Fock reference. As a result, the applicability of ECC has been limited to small benchmark systems, for which the ansatz was shown to be superior to the configuration interaction and linearized approximations. In this article, we provide a solution to this problem that completely avoids the metric diagonalization by iteratively projecting out its null-space from the working equations. As the additional computational cost required for this iterative projection is only marginal, it greatly expands the application range of ECC. We demonstrate the potential of approximate ECC by studying the complete basis set limit of F₂ and transition metal complexes such as NiO, Mn₂, and [Cu₂O₂]²⁺ , which have all been hindered by the prohibitively large metric size. We also identify the potential inadequacy of the molecular orbitals given by spin-projected Hartree–Fock in some cases, and propose possible solutions. © 2018 Wiley Periodicals, Inc.     

Electronic state on the surface in the strongly correlated electron systems

In order to clarify the tunneling spectroscopy in high-T_c cuprates, we study electronic state of the surface in the strongly correlated electron systems. First, we obtain Green's function of strongly correlated normal bulk system using the fluctuation exchange (FLEX) approximation. Next, we insert infinite potential into the bulk system and obtain Green's function of surface. We find that the density of states (DOS) in strongly correlated bulk systems are different from that on the surface, and the difference decreases as the magnitude of Coulomb interaction (U) increases.     

A comparative study of the radical-scavenging activity of the phenolcarboxylic acids caffeic acid, p-coumaric acid, chlorogenic acid and ferulic acid, with or without 2-mercaptoethanol, a thiol, using the induction period method

Phenolcarboxylic acid antioxidants do not act in vivo as radical-scavengers in isolation, but rather together with GSH (glutathione), a coantioxidant, they constitute an intricate antioxidant network. Caffeic acid, p-coumaric acid, ferulic acid and chlorogenic acid with or without 2-mercaptoethanol (ME), as a substitute for GSH, was investigated by the induction period (IP) method for polymerization of methyl methacrylate (MMA) initiated by thermal decomposition of 2,2'-azobisisobutyronitrile (AIBN, a source of alkyl radicals, R(.)) and benzoyl peroxide (BPO, a source of peroxy radicals, PhCOO(.)) using differential scanning calorimetry (DSC). Upon PhCOO(. )radical scavenging, the stoichiometric factors (n, number of free radical trapped by one mole of antioxidant) for caffeic acid, ferulic acid, p-coumaric acid and chlorogenic acid were 2.4, 1.8, 1.7 and 0.9, whereas upon R(.) radical scavenging, the corresponding values were 1.3, 1.2, 1.0 and 0.8, respectively. Antioxidants with n values close to 2 suggest the stepwise formation of semiquinone radicals and quinones. By contrast, those with n values close to 1 suggest the formation of dimers after single-electron oxidation, possibly due to recombination of corresponding aryloxy radicals. The ratio of the rate constant of inhibition to that of propagation (k(inh)/k(p)) declined in the order chlorogenic acid > p-coumaric acid > ferulic acid > caffeic acid. The ratio of the observed IP for the phenolcarboxylic acid/2-mercapto-ethanol (ME) mixture (1:1 molar ratio) (A) to the calculated IP (the simple sum of phenol acid antioxidant and ME) (B) was investigated. Upon R(.) scavenging, the caffeic acid or p-coumaric acid/ME mixture was A/B > 1, particularly the former was 1.2, suggesting a synergic effect. By contrast, upon PhCOO(.) scavenging, the corresponding mixture was A/B < 1, particularly the latter was 0.7, suggesting an antagonistic effect. Upon both radicals scavenging, the A/B for the ferulic acid or chlorogenic acid/ME mixture was approximately 1. The reported beneficial antioxidant, anti-inflammatory and anticancer effects of caffeic acid and p-coumaric acid may be related to their prooxidant-antioxidant balance in the presence of GSH.     

Explicitly correlated coupled cluster F12 theory with single and double excitations

Full explicitly correlated F12 coupled cluster theory with single and double excitations and with Slater-type geminal as a correlation factor is introduced and implemented within the standard approximation. The variant "C" that does not require integrals over the commutator between the kinetic operator and the correlation factor has been used. All the necessary integrals are analytically calculated. With variant C also, first results are reported for the correlation factor being the interelectronic distance coordinate, i.e., for original R12 method. Calculations have been performed for a set of eight molecules including CH(2)((1)A(1)), CH(4), NH(3), H(2)O, HF, CO, N(2), and F(2), as well as for the constituting atoms. Atomization energies are reported too.