N-fused porphyrin with pyridinium side-arms: a new class of aromatic ligand with DNA-binding ability

N-fused porphyrin (NFP) is a porphyrin analogue with an 18π tetrapyrrolic macrocycle, in which a unique tripentacyclic ring is embedded. While the optical properties of NFP of absorbing and emitting near-infrared (NIR) light around 1000 nm are promising for its application to NIR technology, its unique structure is also attractive as a platform to construct a novel class of DNA-binding ligands. Herein, we have synthesized a water-soluble derivative of NFP (pPyNFP) possessing four cationic pyridinium substituents and examined its acid/base behaviors and interactions with various forms of DNAs in aqueous solution. pPyNFP interacts with ssDNA and dsDNA electrostatically. pPyNFP also interacts with a G-quadruplex DNA derived from the human telomeric sequence and causes a characteristic spectral change of the G-quadruplex DNA, which suggests that pPyNFP modulates the Na(+)-induced (2 + 2) antiparallel G-quadruplex to the all-parallel structure.     

Laser spectroscopic and theoretical studies of encapsulation complexes of calix[4]arene

The complexes between the host calix[4]arene (C4A) and various guest molecules such as NH(3), N(2), CH(4), and C(2)H(2) have been investigated via experimental and theoretical methods. The S(1)-S(0) electronic spectra of these guest-host complexes are observed by mass-selected resonant two-photon ionization (R2PI) and laser-induced fluorescence (LIF) spectroscopy. The IR spectra of the complexes formed in molecular beams are obtained by IR-UV double resonance (IR-UV DR) and IR photodissociation (IRPD) spectroscopy. The supramolecular structures of the complexes are investigated by electronic structure methods (density functional and second order perturbation theory). The current results for the various molecular guests are put in perspective with the previously reported ones for the C4A-rare gas (Rg) (Phys. Chem. Chem. Phys. 2007, 126, 141101) and C4A-H(2)O complexes (J. Phys. Chem. A, 2010, 114, 2967). The electronic spectra of the complexes of C4A with N(2), CH(4), and C(2)H(2) exhibit red-shifts of similar magnitudes with the ones observed for the C4A-Rg complexes, whereas the complexes of C4A with H(2)O and NH(3) show much larger red-shifts. Most of the IR-UV DR spectra of the complexes, except for C4A-C(2)H(2), show a broad hydrogen-bonded OH stretching band with a peak at ~3160 cm(-1). The analysis of the experimental results, in agreement with the ones resulting from the electronic structure calculations, suggest that C4A preferentially forms endo-complexes (guests inside the host calizarene cavity) with all the guest species reported in this study. We discuss the similarities and differences of the structures, binding energies, and the nature of the interaction between the C4A host and the various guest species.     

Development of High-Pressure ESR System Using Micro-coil

We have developed the high-pressure electron spin resonance (ESR) system using a micro-coil in the frequency region up to around 2 GHz and potentially 10 GHz. The hybrid-type piston-cylinder pressure cell whose maximum pressure reaches 4 GPa was used. In this study, we obtained ESR spectra at 2.3 GPa successfully, which can never be obtained by the single-layer piston-cylinder pressure cell. The minimum detectable spin number was estimated to be the order of 10¹² spins/G. Moreover, it is shown that the sensitivity can be improved by two orders of magnitude using the field modulation technique. This high-pressure ESR technique is a promising one to achieve the sensitivity and the high pressure simultaneously.     

Heat capacity of CeIrSi3 under pressure

We measured the heat capacity of CeIrSi₃ (100 mK<T<6 K) under high pressure up to P=1.38 GPa. The measurements have been used a quasiadiabatic method utilizing a CuBe piston-cylinder pressure cell in a dilution refrigerator. At 0 GPa, a sharp anomaly which indicates the antiferromagnetically transition is observed at T_N=5 K. T_N decreases monotonically with increasing pressure up to P=1.38 GPa. The magnetic entropy is released below T_N only 19% of R ln 2 at 0 GPa. And the magnetic entropy decreases with increasing pressure up to 1.38 GPa, 64% compared to that at 0 GPa.     

Domain wall dynamics and interlayer interactions in magnetic trilayer systems studied by XMCD-PEEM

We have used time-resolved x-ray magnetic circular dichroism combined with photoemission electron microscopy (XMCD-PEEM) to investigate the layer-resolved microscopic magnetization reversal in FeNi/X/Co (with X=Cu, Al₂O₃) trilayer systems. These measurements were performed in pump-probe mode, synchronizing magnetic pulses with synchrotron x-ray pulses. The good magnetic contrast observed for most samples reveals that in many cases the magnetization reversal is reproducible. We have used the measurements to obtain domain wall propagation speeds as a function of applied magnetic field, and to investigate the influence of domain wall interactions on the magnetic switching.     

中国古建筑结构力学研究进展

中国古代建筑是中国古代文化的宝贵遗产. 力学的多样性也反映在古建筑 结构力学研究. 西安交通大学从1982年开始, 对以西安明代箭楼、城楼和宁波宋代保国寺 等国家重点保护文物为代表的木结构建筑, 以唐代大雁塔、小雁塔等国家重点保护文物为代 表的古代高层建筑, 和以国家重点保护文物西安古城墙为代表的砖-土结构以及钟楼、鼓楼 等中国城市的代表性古建筑的结构力学特性进行了一系列研究. 得到关于古建筑结构(如斗 拱、结构非线性、榫卯节点的接触力学特性、地宫、古代夯土、古塔基础、古城墙等)力学 特性的新认识. 本文对此进行小结, 同时也介绍近年来的其它学者的一些研究.