An Efficient Algorithm for Enumerating Chordless Cycles and Chordless Paths

A chordless cycle (induced cycle) $C$ of a graph is a cycle without any chord, meaning that there is no edge outside the cycle connecting two vertices of the cycle. A chordless path is defined similarly. In this paper, we consider the problems of enumerating chordless cycles/paths of a given graph $G=(V,E),$ and propose algorithms taking $O(|E|)$ time for each chordless cycle/path. In the existing studies, the problems had not been deeply studied in the theoretical computer science area, and no output polynomial time algorithm has been proposed. Our experiments showed that the computation time of our algorithms is constant per chordless cycle/path for non-dense random graphs and real-world graphs. They also show that the number of chordless cycles is much smaller than the number of cycles. We applied the algorithm to prediction of NMR (Nuclear Magnetic Resonance) spectra, and increased the accuracy of the prediction

63/65^{63/65}Cu- and 35/37^{35/37}Cl-NMR Studies of Triplet Localization in the Quantum Spin System NH4_4CuCl3_3

$^{63/65}$Cu- and $^{35/37}$Cl-NMR experiments were performed to investigate triplet localization in the $S=1/2$ dimer compound NH$_4$CuCl$_3$, which shows magnetization plateaus at one-quarter and three-quarters of the saturation magnetization. In $^{63/65}$Cu-NMR experiments, signal from only the singlet Cu site was observed, because that from the triplet Cu site was invisible due to the strong spin fluctuation of onsite 3$d$-spins. We found that the temperature dependence of the shift of $^{63/65}$Cu-NMR spectra at the singlet Cu site deviated from that of macroscopic magnetization below T=6 K. This deviation is interpreted as the triplet localization in this system. From the $^{35/37}$Cl-NMR experiments at the 1/4-plateau phase, we found the two different temperature dependences of Cl-shift, namely the temperature dependence of one deviates below T=6 K from that of the macroscopic magnetization as observed in the $^{63/65}$Cu-NMR experiments, whereas the other corresponds well with that of the macroscopic magnetization in the entire experimental temperature region. We interpreted these dependences as reflecting the transferred hyperfine field at the Cl site located at a singlet site and at a triplet site, respectively. This result also indicates that the triplets are localized at low temperatures. $^{63/65}$Cu-NMR experiments performed at high magnetic fields between the one-quarter and three-quarters magnetization plateaus have revealed that the two differently oriented dimers in the unit cell are equally occupied by triplets, the fact of which limits the theoretical model on the periodic structure of the localized triplets.Comment: 19 pages, 9 figures, submitted to PRB (in press

フェノール・ベンゼン混合ダイマーイオンの振動・電子スペクトルの観測

1999年分子構造総合討論会, 1999年9月27日-30日, 大阪大学(大阪), 1pB6

Donepezil-like multifunctional agents: Design, synthesis, molecular modeling and biological evaluation

Currently available drugs against Alzheimer's disease (AD) are only able to ameliorate the disease symptoms resulting in a moderate improvement in memory and cognitive function without any efficacy in preventing and inhibiting the progression of the pathology. In an effort to obtain disease-modifying anti-Alzheimer's drugs (DMAADs) following the multifactorial nature of AD, we have recently developed multifunctional compounds. We herein describe the design, synthesis, molecular modeling and biological evaluation of a new series of donepezil-related compounds possessing metal chelating properties, and being capable of targeting different enzymatic systems related to AD (cholinesterases, ChEs, and monoamine oxidase A, MAO-A). Among this set of analogues compound 5f showed excellent ChEs inhibition potency and a selective MAO-A inhibition (vs MAO-B) coupled to strong complexing properties for zinc and copper ions, both known to be involved in the progression of AD. Moreover, 5f exhibited moderate antioxidant properties as found by in vitro assessment. This compound represents a novel donepezil–hydroxyquinoline hybrid with DMAAD profile paving the way to the development of a novel class of drugs potentially able to treat AD

Charge Resonance and Charge Transfer Interactions in Naphthalene Homo- and Hetero-Dimers

Charge resonance interaction in naphthalene homo- and hetero-dimer cations is studied by photodissociation spectroscopy of the charge resonance and the local excitation transitions. The resonance interaction in naphthalene dimer cation is slightly weaker than that of a benzene dimer cation because of partial overlapping of the respective aromatic rings. A local excitation band of the benzene cation chromophore is observed in the spectrum of a naphthalene-benzene hetero-dimer cation at nearly the same position as that of the benzene dimer cation. This indicates that in spite of its higher ionization potential the positive charge stays on the benzene molecule in some probability. On the basis of the band position of the charge resonance transition as well as the intensity of the local excitation band, the probability is analyzed to be approximately 9 %. This means 91 % is localized on the naphthalene chromophore in this hetero-dimer.AIP Conference Proceedings 38

S1 excited-state dynamics of OMpCA and its hydrogen-bonded complexes

第30回化学反応討論会, 2014年6月4日-6日, イーグレひめじ(姫路

Conformation of Alkali Metal Ion−Benzo-12-Crown‑4 Complexes Investigated by UV Photodissociation and UV−UV Hole-Burning Spectroscopy

We measure UV photodissociation (UVPD) spectra of benzo-12-crown-4 (B12C4) complexes with alkali metal ions, M+·B12C4 (M = Li, Na, K, Rb, and Cs), in the 36300−37600 cm−1 region. Thanks to the cooling of ions to ∼10 K, all the M+·B12C4 complexes show sharp vibronic bands in this region. For UV−UV hole-burning (HB) spectroscopy, we first check if our experimental system works well by observing UV−UV HB spectra of the K+ complex with benzo-18-crown-6 (B18C6), K+·B18C6. In the UV−UV HB spectra of the K+·B18C6 complex, gain signals are also observed; these are due to vibrationally hot K+·B18C6 complex produced by the UV excitation of cold K+·B18C6 complex. Then we apply UV−UV HB spectroscopy to the M+·B12C4 complexes, and only one conformer is found for each complex except for the Li+ complex, which has two conformers. The vibronic structure around the origin band of the UVPD spectra is quite similar for all the complexes, indicating close resemblance of the complex structure. The most stable structures calculated for the M+·B12C4 (M = Li, Na, K, Rb, and Cs) complexes also have a similar conformation among them, which coincides with the UVPD results. In these conformers the metal ions are too big to be included in the B12C4 cavity, even for the Li+ ion. In solution, it was reported that 12-crown-4 (12C4) shows the preference of Na+ ion among alkali metal ions. From the similarity of the structure for the M+·B12C4 complexes, it is suggested that the solvation of free metal ions, not of the M+·12C4 complexes, may lead to the selectivity of Na+ ion for 12C4 in solution.This work was partly supported by JSPS KAKENHI Grant Number 16H04098