Self-phase modulation signatures of neuronal activity

We use phase-sensitive detection of spectral hole refilling to demonstrate strong novel intrinsic nonlinear signatures of neuronal activation in hippocampal brain slices. The ability to gain access to this fundamentally new intrinsic contrast with modest power levels suggests a new approach to in vivo neural imaging. We expect that we can extrapolate our method to high spatial and temporal resolution in deep tissue while retaining the noninvasive character.     

C-H activation on a diphosphine and hydrido-bridged diiridium complex: generation and detection of an active IrII-IrII species [(Cp*Ir)2(micro-dmpm)(micro-H)]+

Reaction of [Cp*Ir(micro-H)](2) (5) (Cp* = eta(5)-C(5)Me(5)) with bis(dimethylphosphino)methane (dmpm) gives a new neutral diiridium complex [(Cp*Ir)(2)(micro-dmpm)(micro-H)(2)] (3). Treatment of 3 with methyl triflate at -30 degrees C results in the formation of [(Cp*Ir)(H)(micro-dmpm)(micro-H)(Me)(IrCp*)][OTf] (6). Warming a solution of above 0 degrees C brings about predominant generation of 32e(-) Ir(II)-Ir(II) species [(Cp*Ir)(micro-dmpm)(micro-H)(IrCp*)][OTf] (7). Further heating of the solution of 7 up to 30 degrees C for 14 h leads to quantitative formation of a new complex [(Cp*Ir)(H)(micro-Me(2)PCH(2)PMeCH(2))(micro-H)(IrCp*)][OTf] (8), which is formed by intramolecular oxidative addition of the methyl C-H bond of the dmpm ligand. Intermolecular C-H bond activation reactions with 7 are also examined. Reactions of 7 with aromatic molecules (benzene, toluene, furan, and pyridine) at room temperature result in the smooth sp(2) C-H activation to give [(Cp*Ir)(H)(micro-dmpm)(micro-H)(Ar)(IrCp*)][OTf] (Ar = Ph (9); Ar = m-Tol (10a) or p-Tol (10b); Ar = 2-Fur (11)) and [(Cp*Ir)(H)(micro-dmpm)(micro-C(5)H(4)N)(H)(IrCp*)][OTf] (12), respectively. Complex also reacts with cyclopentene at 0 degrees C to give [(Cp*Ir)(H)(micro-dmpm)(micro-H)(1-cyclopentenyl)(IrCp*)][OTf] (13). Structures of 3, 8 and 12 have been confirmed by X-ray analysis.     

Synthesis and estimation of gelation ability of C3-symmetry tris-urea compounds

C₃-Symmetry tris-urea low molecular weight gelator (LMWG) (1), which shows chemical stimuli responsible for a sol-gel phase transition, was divided into five regions. Based on the division, 22 derivatives were synthesized. The gelation ability of these derivatives was tested in nine organic solvents with a wide range of values for relative static permittivity (?_r=47.2-1.89). Some derivatives showed a better performance as LMWGs than the original tris-urea LMWG (1). For example, the critical gelation concentration (CGC) in acetone was improved from 1.5 wt % to 0.5 wt % by changing the core substituent (18). Highly versatile LMWG for a variety of solvents was obtained by changing the linker moiety (23). Structural information to design tris-urea LMWGs is important to create rationally a functional supramolecular gel.     

Theoretical study on second hyperpolarizabilities of singlet diradical square planar nickel complexes involving o-semiquinonato type ligands

Hybrid density functional theory method is applied for investigating the diradical character dependence of the second hyperpolarizability (gamma) of square planar nickel complexes involving several types of bidentate ligands [o-C6H4XY, where X = Y = O, NH, S, Se, and PH as well as (X, Y) = (NH, NH2) and (S, NH2)]. It is found that, as a function of the donor atoms, the diradical character of these complexes varies from 0.0 to 0.884 and is associated with substantial variations of gamma ranging from 14 x 10(3) to 819 x 10(3) au. In particular, the largest gamma values are associated with intermediate diradical characters in good agreement with the structure-property relationship obtained for pure hydrocarbon systems. Increasing the electronegativity of the X and Y donor groups of the ligands leads to larger diradical characters as a result of the enhancement of the double bond nature of the C=X(Y) bonds, which further stabilizes the diradicals on both-end benzene rings. This demonstrates that the electronegativities of the donor atoms of the ligands become a tuning parameter of the diradical character and then of the gamma values of these complexes.     

Computation of the reduction free energy of coenzyme in aqueous solution by the QM/MM-ER method

In a recent development we proposed a quantum chemical approach to compute free energy change for chemical reactions in condensed phases by combining the QM/MM method with the theory of energy representation (QM/MM-ER). We extend in this Letter the novel approach to compute reduction free energy of isoalloxazine ring of FAD (flavin adenine dinucleotide) immersed in water within the framework of the QM/MM-ER method. The characteristic feature of our approach is that the excess electron to be attached on the FAD is identified as a solute. The reduction free energy has been obtained as −80.1 kcal/mol in the aqueous solution.     

Heparin bioconjugate with a thermoresponsive cationic branched polymer: a novel aqueous antithrombogenic coating material

With a view to reducing the thrombogenic potential of artificial blood-contact devices and natural tissues, we developed a novel aqueous antithrombogenic coating material, comprising a heparin bioconjugate that incorporated a thermoresponsive cationic polymer as a surfactant. The polymer was prepared by the sequential steps of initiator-transfer agent-terminator (iniferter)-based living radical photopolymerization of N-[3-(dimethylamino)propyl]acrylamide, followed by the polymerization of N-isopropylacrylamide from tetra(N,N-diethyldithiocarbamylmethyl)benzene as a multifunctional iniferter. The polymer obtained possessed four branched chains, each consisting of a cationic PDMAPAAm block (Mn: ca. 3000 g.mol(-1)) forming an inner domain for heparin binding and a thermoresponsive PNIPAM block (Mn: ca. 6000 g.mol(-1)) forming an outer domain for surface fixation; bioconjugation of the polymer with heparin occurred immediately upon simple mixing in an aqueous medium. Because the lower critical solution temperature of the heparin bioconjugate was approximately 35 degrees C, it could be coated from an aqueous solution at room temperature. The excellent adsorptivity and high durability of the coating below 37 degrees C was demonstrated on several generally used polymers by wettability measurement and surface chemical compositional analysis, and on collagen sheets and rat skin tissue by heparin staining. Blood coagulation was significantly prevented on the heparin bioconjugate-coated surfaces. The thermoresponsive bioconjugate developed therefore appeared to satisfy the initial requirements for a biocompatible aqueous coating material.     

Nd2Fe14B/α-Fe双泪永磁合金快淬带的织构与形貌

利用X射线衍射仪和扫描探针显微镜研究了NeFeB系双相永磁合金快淬带的织构与形貌.结果表明,合金快淬带自由面存在择优取向.与三元NdFeB合金相比,复合添加Dy和Ga具有增加合金快淬带织构和细化组织形貌的作用. 关键词：     

Mass spectrometric strategy for the characterization of lipooligosaccharides from Neisseria gonorrhoeae 302 using FTICR

The lipooligosaccharides (LOS) of Neisseria gonorrhoeae 302 were profiled using Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). Using techniques developed in this laboratory, the topology and some of the linkages of the LOS were determined. Mass spectrometric analysis in the negative ion mode yielded a glycoform of the composition: Hex3 Hep2 Hxn1 PEA1 KDO2 DPLA. The composition was confirmed through exact mass measurements, which showed only a 2 ppm error between the exact mass and theoretical mass. Although the core structure has been postulated previously, the positioning of the three hexose moieties were in question for this particular strain of N. gonorrhoeae. Topology assignment was performed through collision-induced dissociation analysis of the O-deacylated glycoform in the negative ion mode followed by submission to the saccharide topology analysis tool (STAT) computer program, which confirmed the topology assignment. It was found that the three hexoses were added to the Hep[I] of the conserved core of N. gonorrhoeae in a linear fashion, while Hep[II] remains unbranched. Linkage position analysis was performed through application of a mild acid hydrolysis technique followed by collision-induced dissociation of the sodiated precursor ions, yielding a 1 --> 4 linkage between the terminating and penultimate hexoses.     

Neutron electric dipole moment measurement with a buffer gas comagnetometer

A neutron EDM measurement with a comagnetometer is discussed. For magnetometry, polarized xenon atoms are injected into a cylindrical cell where a cylindrically symmetric magnetic field and an electric field are applied for the EDM measurement. The geometric phase effect (GPE), which originates from particle motion in a magnetic field gradient, is analyzed in terms of the Dyson series. The motion of the xenon atom is largely suppressed because of a small mean free path. The field gradient is controlled by means of NMR measurements, where the false effect of Earth?s rotation is removed. As a result, the GPE is reduced below 10⁻²⁸e cm${10}^{-28}e\text{cm}$.