Evaluation of electronic matrix elements of long-range electron transfer in proteins by the recursive residue generation method

An efficient method for calculating electronic matrix elements for electron-transfer reactions in biological systems is proposed. We use the tight-binding model to describe the motion of one-electron in an array representing the system: donor (D), acceptor (A), and all other atoms that compose the protein. The matrix elements |T_DA|;² is evaluated at the estimated electron energy. The essential part of the method lies in the evaluation of the off-diagonal Green function 〈I|G|F〉 between the site I neighboring with the donor and the site F with the acceptor. The recursive residue generation method is used to evaluate 〈I|G|F|〉. As an application, these matrix elements in metal-labeled myoglobin are calculated and the results are compared with those evaluated with the renormalized-perturbation-expansion approach. © 1994 John Wiley & Sons, Inc.     

Electronic and infrared spectroscopy of [benzene-(methanol)(n)](+) (n = 1-6)

The microsolvation structure of the [benzene-(methanol)(n)](+) (n = 1-6) clusters was analyzed by electronic and infrared spectroscopy. For the n = 1 and 2 clusters, further spectroscopic investigation was carried out by Ar atom attachment, which has been know as a useful technique for discriminating isomers of the clusters. The coexistence of multiple isomers was confirmed for the n = 1 and 2 clusters, and remarkably, preferential production of the specific isomers occurred in the Ar attachment. The most stable isomer of the n = 1 cluster was suggested to be of the "on-ring" structure where the nonbonding electrons of the methanol moiety directly interact with the pi orbital of the benzene cation moiety. This is a sharp contrast to [benzene-(H(2)O)(1)](+), exhibiting the "side" structure, where the water moiety is bound to the C-H sites of the benzene cation moiety. The structure of the n = 2 cluster was discussed with the help of density functional theory calculations. Spectral signatures of the intracluster proton-transfer reaction were found for n > or = 5. The intracluster electron-transfer reaction leading to the (methanol)(m)()(+) fragment was also seen upon vibrational and electronic excitation of n > or = 4.     

Local action functionals for randomly perturbed dynamical systems on long time intervals ∗

We prove exponential decays of probabilities of randomly perturbed dynamical systems in a d–dimensional Euclidean space R^d on time intervals which go to [0,∞] as the random fluctuation disappears. We also consider the exit problems when unperturbed dynamical systems are attracted to the inside of the domain under consideration     

In situ observation of UF5 nanoparticle growth in a low-pressure mixed-flow reactor

5 nanoparticles equipped with an in situ size-monitoring system, a LPDMA (low-pressure differential mobility analyzer), was developed to experimentally investigate the nanoparticle growth mechanism. The concentration of photoproduced UF₅ molecules was controlled by changing three factors: (I) the concentration of the feed UF₆ gas, (II) the laser pulse energy of the irradiation, and (III) the repetition rate of the laser pulses. The dependence of the volumetric average diameter of the photoproduced particles on the UF₅ nascent concentration in all three cases was found to be very similar. The result strongly suggests that the reactor functions as a mixed-flow reactor under a complete mixing condition. The particle size measured by the LPDMA was found to be in the range of 6 to 11 nm, and it was approximately proportional to the power 0.3 of the initial concentration of photoproduced UF₅ molecules. Received: 11 May 1998/Accepted: 15 September 1998     

Growth of epitaxial TmFeCuO4 thin films by pulsed laser deposition

Epitaxial thin films of TmFeCuO₄ with a two-dimensional triangular lattice structure were successfully grown on yttria-stabilized-zirconia substrates by pulsed laser deposition and ex situ annealing in air. The films as-deposited below 500 °C showed no TmFeCuO₄ phase and the subsequent annealing resulted in the decomposition of film components. On the other hand, as-grown films deposited at 800 °C showed an amorphous nature. Thermal annealing converted the amorphous films into highly (0 0 1)-oriented epitaxial films. The results of scanning electron microscopic analysis suggest that the crystal growth process during thermal annealing is dominated by the regrowth of non-uniformly shaped islands to the distinct uniform islands of hexagonal base.     

Infrared and electronic spectroscopy of a model system for the nucleophilic substitution intermediate in the gas phase: the C-N valence bond formation in the benzene-ammonia cluster cation

Infrared and electronic spectroscopy was applied to the benzene-ammonia cluster cation in the gas phase, and the observed spectra revealed the formation of a new C-N valence bond between the benzene and ammonia moieties, which has been predicted by the quantum chemical calculations (Tachikawa, H. Phys. Chem. Chem.Phys. 2002, 4, 6018). This cluster cation is regarded as a model for the cyclohexadienyl type intermediate in nucleophilic substitution reactions.     

Magnitude and directionality of the interaction energy of the aliphatic CH/pi interaction: significant difference from hydrogen bond

The CCSD(T) level interaction energies of CH/pi complexes at the basis set limit were estimated. The estimated interaction energies of the benzene complexes with CH(4), CH(3)CH(3), CH(2)CH(2), CHCH, CH(3)NH(2), CH(3)OH, CH(3)OCH(3), CH(3)F, CH(3)Cl, CH(3)ClNH(2), CH(3)ClOH, CH(2)Cl(2), CH(2)FCl, CH(2)F(2), CHCl(3), and CH(3)F(3) are -1.45, -1.82, -2.06, -2.83, -1.94, -1.98, -2.06, -2.31, -2.99, -3.57, -3.71, -4.54, -3.88, -3.22, -5.64, and -4.18 kcal/mol, respectively. Dispersion is the major source of attraction, even if substituents are attached to the carbon atom of the C-H bond. The dispersion interaction between benzene and chlorine atoms, which is not the CH/pi interaction, is the cause of the very large interaction energy of the CHCl(3) complex. Activated CH/pi interaction (acetylene and substituted methanes with two or three electron-withdrawing groups) is not very weak. The nature of the activated CH/pi interaction may be similar to the hydrogen bond. On the other hand, the nature of other typical (nonactivated) CH/pi interactions is completely different from that of the hydrogen bond. The typical CH/pi interaction is significantly weaker than the hydrogen bond. Dispersion interaction is mainly responsible for the attraction in the CH/pi interaction, whereas electrostatic interaction is the major source of attraction in the hydrogen bond. The orientation dependence of the interaction energy of the typical CH/pi interaction energy is very small, whereas the hydrogen bond has strong directionality. The weak directionality suggests that the hydrogen atom of the interacting C-H bond is not essential for the attraction and that the typical CH/pi interaction does not play critical roles in determining the molecular orientation in molecular assemblies.     

Duality theorem for the stochastic optimal control problem

We prove a duality theorem for the stochastic optimal control problem with a convex cost function and show that the minimizer satisfies a class of forward–backward stochastic differential equations. As an application, we give an approach, from the duality theorem, to h$h$-path processes for diffusion processes.