All-electron density functional calculation on insulin with quasi-canonical localized orbitals

An all-electron density functional (DF) calculation on insulin was performed by the Gaussian-based DF program, ProteinDF. Quasi-canonical localized orbitals (QCLOs) were used to improve the initial guess for the self-consistent field (SCF) calculation. All calculations were carried out by parallel computing on eight processors of an Itanium2 cluster (SGI Altix3700) with a theoretical peak performance of 41.6 GFlops. It took 35 h for the whole calculation. Insulin is a protein hormone consisting of two peptide chains linked by three disulfide bonds. The numbers of residues, atoms, electrons, orbitals, and auxiliary functions are 51, 790, 3078, 4439, and 8060, respectively. An all-electron DF calculation on insulin was successfully carried out, starting from connected QCLOs. Regardless of a large molecule with complicated topology, the differences in the total energy and the Mulliken atomic charge between initial and converged wavefunctions were very small. The calculation proceeded smoothly without any trial and error, suggesting that this is a promising method to obtain SCF convergence on large molecules such as proteins.     

Fiber-optic calcium(II) sensor with reversible response

The fiber-optic sensor for calcium ions is based on the fluorescent chelate of chlortetracycline formed in aqueous solution at pH 7.5. The chlortetracycline is immobilized on an anion-exchange membrane, which is attached to the end of a bifurcated fiber optic. The sensor responds to calcium ions in the 0–400 mM range; the error in measurements is ± 10 mM. The response is reversible but other divalent metals interfere.     

Sodium and Manganese Stoichiometry of P2‐Type Na2/3MnO2

To realize a reversible solid‐state Mn^III/IV redox couple in layered oxides, co‐operative Jahn–Teller distortion (CJTD) of six‐coordinate Mn^III (t_2g³–e_g¹) is a key factor in terms of structural and physical properties. We develop a single‐phase synthesis route for two polymorphs, namely distorted and undistorted P2‐type Na_2/3MnO₂ having different Mn stoichiometry, and investigate how the structural and stoichiometric difference influences electrochemical reaction. The distorted Na_2/3MnO₂ delivers 216 mAh g^?1 as a 3 V class positive electrode, reaching 590 Wh (kg oxide)^?1 with excellent cycle stability in a non‐aqueous Na cell and demonstrates better electrochemical behavior compared to undistorted Na_2/3MnO₂. Furthermore, reversible phase transitions correlated with CJTD are found upon (de)sodiation for distorted Na_2/3MnO₂, providing a new insight into utilization of the Mn^III/IV redox couple for positive electrodes of Na‐ion batteries.     

Femtosecond time-resolved electronic sum-frequency generation spectroscopy: a new method to investigate ultrafast dynamics at liquid interfaces

We developed a new surface-selective time-resolved nonlinear spectroscopy, femtosecond time-resolved electronic sum-frequency generation (TR-ESFG) spectroscopy, to investigate ultrafast dynamics of molecules at liquid interfaces. Its advantage over conventional time-resolved second harmonic generation spectroscopy is that it can provide spectral information, which is realized by the multiplex detection of the transient electronic sum-frequency signal using a broadband white light continuum and a multichannel detector. We studied the photochemical dynamics of rhodamine 800 (R800) at the air/water interface with the TR-ESFG spectroscopy, and discussed the ultrafast dynamics of the molecule as thoroughly as we do for the bulk molecules with conventional transient absorption spectroscopy. We found that the relaxation dynamics of photoexcited R800 at the air/water interface exhibited three characteristic time constants of 0.32 ps, 6.4 ps, and 0.85 ns. The 0.32 ps time constant was ascribed to the lifetime of dimeric R800 in the lowest excited singlet (S(1)) state (S(1) dimer) that is directly generated by photoexcitation. The S(1) dimer dissociates to a monomer in the S(1) state (S(1) monomer) and a monomer in the ground state with this time constant. This lifetime of the S(1) dimer was ten times shorter than the corresponding lifetime in a bulk aqueous solution. The 6.4 ps and 0.85 ns components were ascribed to the decay of the S(1) monomer (as well as the recovery of the dimer in the ground state). For the 6.4 ps time constant, there is no corresponding component in the dynamics in bulk water, and it is ascribed to an interface-specific deactivation process. The 0.85 ns time constant was ascribed to the intrinsic lifetime of the S(1) monomer at the air/water interface, which is almost the same as the lifetime in bulk water. The present study clearly shows the feasibility and high potential of the TR-ESFG spectroscopy to investigate ultrafast dynamics at the interface.     

Donors and acceptors based on triangular dehydrobenzo[12]annulenes: formation of a triple-layered rosette structure by a charge-transfer complex

We present here the results of studies of the synthesis and properties of donors and acceptors based on triangular dehydrobenzo[12]annulene ([12]DBA) system as a pi core. These studies were aimed at controlling the supramolecular crystal structure. Toward this end, the tricyano[12]DBA 2 and dodecafluoro[12]DBA ( 3) were synthesized as acceptors (A) and the tris(dialkylamino)[12]DBAs 4a-d as donors (D), and their electronic properties were determined by electronic absorption spectroscopy and electrochemical measurements. The main focus, though, was the formation of supramolecular structures in crystals. These compounds form distinct packing patterns as a result of the different intermolecular interactions. Tricyano[12]DBA 2 forms a two-dimensional (2D) sheet structure via hydrogen-bonding interactions, whereas a tilted-stack structure was found for 3 because of the lack of significant intermolecular interactions. Tris(dibutylamino)[12]DBA 4b exhibits a ladder-type 2D structure, probably because of van der Waals interactions between the butyl groups. The most significant finding is that charge-transfer interactions between donor 4a and acceptor 3 combined with their triangular molecular shapes and lateral CH...F hydrogen bonding result in the formation of a 2D rosette structure consisting of two different trimeric (DAD- and ADA-type) sandwich structures with 1:2 and 2:1 A/D ratios, respectively.     

Interface-specific chi(4) coherent Raman spectroscopy in the frequency domain

We demonstrate interface-specific fourth-order (chi(4)) coherent Raman spectroscopy in the frequency domain for the first time. Because the chi(4) Raman spectroscopy uses only visible (vis) or near-IR light, it is expected to be a potential alternative to the widely utilized IR-vis sum frequency generation spectroscopy that cannot be applied to interfaces buried in thick IR absorbers such as water. We present the vibrational absolute value(chi(4))2 spectrum of rhodamine 800 at the air/water interface in a wide spectral range 100-3600 cm(-1). Comparison of the absolute value(chi(4))2 spectrum with the absolute value(chi(3))2 spectrum leads us to conclude that the present chi(4) spectroscopy successfully probes the interface distinguished clearly from the bulk.     

Removal of residual images in parallel phase-shifting digital holography

Parallel phase-shifting digital holography (PPSDH) is a technique of single-shot phase-shifting digital holography. We found that there are two problems with this technique. (1) Some extraneous noises caused by the intensity unevenness of the reference wave become slightly superimposed on the object image. (2) The conjugate image cannot be completely removed. This is because the object wave causes the phase-shift error by illuminating an image sensor with a large incident angle. To solve these problems, we propose an algorithm for removing residual 0th-order diffraction and conjugate images in PPSDH. In the proposed algorithm, we modified phase-shifting interferometry in order to work through the unevenness of the intensity distribution and applied the Fourier transform technique to PPSDH to remove the residual conjugate image. The effectiveness of the proposed algorithm was experimentally verified.