排序方式: 共有117条查询结果,搜索用时 62 毫秒
51.
Nakano K Sada K Kurozumi Y Miyata M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2001,7(1):209-220
The crystal structures of inclusion compounds of cholic acid (CA) with 28 monosubstituted benzenes have been systematically investigated. All of the crystals belong to the monoclinic space group P2(1) and have bilayer structures with one-dimensional molecular channels that can include guest compounds. They are classified into four types of host frameworks that depend on the conformations and stacking modes of the host compound. The host frameworks and the host-guest ratios depend primarily on the molecular volumes of the guest compounds. The packing coefficient of the host cavity (PCcavity), which is the volume ratio of the guest compound to the host cavity, is used to clarify the relationship between the guest volume and isomerization of the host frameworks. The value of PCcavity, for stable inclusion compounds lies in the range of 55-70%. Compounds out of this range induce isomerization of the host frameworks. The packing coefficients of other host-guest compounds, in which the guest components are included in the host cavities through steric dimensions and van der Waals forces, are also in this range. These results indicate that PCcavity is a useful parameter correlation for guest recognition and isomerization of the host frameworks. 相似文献
52.
Vasily V. Bashilov Pavel V. Petrovskii Mara Sada Gianni Zotti 《Journal of organometallic chemistry》2005,690(19):4330-4336
η2-Fullerene (C60 and C70) palladium optically active complexes with the axially chiral enantiomeric ligand of bithienyl series, [(−)tetraMe-BITIOP], have been synthesized and investigated by 31P-{1H} NMR, electronic spectroscopy, CD spectroscopy, cyclic voltammetry and by single crystal X-ray diffraction. 相似文献
53.
Ayabe M Yamashita K Sada K Shinkai S Ikeda A Sakamoto S Yamaguchi K 《The Journal of organic chemistry》2003,68(3):1059-1066
The construction of chirally twisted porphyrin-based molecular capsule 6 and polymeric capsule 8 was investigated by means of scanning electron microscopy (SEM) and (1)H NMR, UV-visible, and CD spectroscopic observations. Molecular capsule 6 and polymeric capsule 8 were constructed by the reaction of chiral cis-Pd(II) complex 4 bearing a (R)-(+)-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (BINAP) ligand with porphyrin 1 bearing four pyridyl groups and porphyrin 2 bearing eight pyridyl groups, respectively. The peak-splitting pattern of the beta-pyrrole protons in the (1)H NMR spectrum and the specific CD spectral pattern bearing an exciton coupling band indicate that both molecular capsule 6 and polymeric capsule 8 are chirally twisted. Moreover, it was found that the CD intensity of the polymeric capsule plotted against [4]/([4] + [3]) shows a sigmoidal curvature, reflecting a unique cooperativity among the ligand groups; that is, the ligand existing in excess over the other dominates the twisting direction. These results consistently demonstrate that "chirality" in these molecular assembly systems is conveniently controlled by the use of chiral ligands. 相似文献
54.
Magnetically Guided Protein Transduction by Hybrid Nanogel Chaperones with Iron Oxide Nanoparticles
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Riku Kawasaki Dr. Yoshihiro Sasaki Dr. Kiyofumi Katagiri Dr. Sada‐atsu Mukai Dr. Shin‐ichi Sawada Prof. Dr. Kazunari Akiyoshi 《Angewandte Chemie (International ed. in English)》2016,55(38):11377-11381
Protein pharmaceuticals show great therapeutic promise, but effective intracellular delivery remains challenging. To address the need for efficient protein transduction systems, we used a magnetic nanogel chaperone (MC): a hybrid of a polysaccharide nanogel, a protein carrier with molecular chaperone‐like properties, and iron oxide nanoparticles, enabling magnetically guided delivery. The MC complexed with model proteins, such as BSA and insulin, and was not cytotoxic. Cargo proteins were delivered to the target HeLa cell cytosol using a magnetic field to promote movement of the protein complex toward the cells. Delivery was confirmed by fluorescence microscopy and flow cytometry. Delivered β‐galactosidase, inactive within the MC complex, became enzymatically active within cells to convert a prodrug. Thus, cargo proteins were released from MC complexes through exchange interactions with cytosolic proteins. The MC is a promising tool for realizing the therapeutic potential of proteins. 相似文献
55.
A. Martucci M. De Nuntis A. Ribaudo M. Guglielmi S. Padovani F. Enrichi G. Mattei P. Mazzoldi C. Sada E. Trave G. Battaglin F. Gonella E. Borsella M. Falconieri M. Patrini J. Fick 《Applied Physics A: Materials Science & Processing》2005,80(3):557-563
Ag- and Er-doped glass films have been synthesized with a combined sol–gel and ion-exchange route. The introduction of silver as erbium sensitizer in the film was obtained by ion exchanging Er-doped SiO2–Al2O3–Na2O sol–gel films. The films were subsequently annealed under controlled atmosphere to induce the migration and aggregation of the metal ions. Films showed different Er3+ photoluminescence behaviors depending on silver concentration and aggregation state. The interaction between erbium ions and Ag centers has been investigated and enhancement of the excitation cross section due to the silver sensitizing effect has been demonstrated. The developed synthesis also allowed the realization of erbium-doped channel waveguides by a selective Na–Ag ion-exchange process . PACS 81.20.Fw; 78.55.-m; 42.82.Et 相似文献
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Tsuchiya Y Shiraki T Matsumoto T Sugikawa K Sada K Yamano A Shinkai S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(2):456-465
In Nature, chromophoric groups play various roles, such as oxygen carriers, electron donors, light sensitizers, which are achieved in many cases by control of their aggregation modes in proteins. Host-guest chemistry between cyclodextrins and porphyrins has attracted great interest from supramolecular chemists because of their unique structures and functions that mimic those of proteins with chromophoric prosthetic groups. To mimic Nature's contrivances, the host-guest systems between cyclodextrins and porphyrins have frequently been studied. It is really surprising, however, that to date no detailed structural information of these complexes has been obtained from single-crystal analysis. In 2011, we reported the first successful isolation of a dye inclusion single crystal (DISC) between 2,3,6-trimethyl-β-cyclodextrin (TMβCD) and 5,10,15,20-tetrapyridylporphyrin (TPyP), and analyzed its X-ray crystal structure. The crystal structure revealed not only the real complex mode but also the attractive orientation of TPyP in the DISC. Herein, we present new strategies to prepare DISCs of TMβCD for several porphyrins and provide crystal structures, details of the complex modes, and optical properties. We believe that the present study has various important implications not only for the basic crystal analysis of inclusion complexes but also for potential applications that use these single crystals. 相似文献
59.
Voice onset time (VOT) is a perceptual cue in voicing contrast of stops in the word initial position. The current study aims
to acoustically and perceptually characterize VOT in one of the major South Indian languages — Tulu. Stimuli consisted of
2 pairs of meaningful words with velar [/p/-/b/] and bilabial stops and [/k/-g/] in the initial position. These words were
uttered by 8 normal native speakers of Tulu and recorded using Praat software. Both spectrogram and waveform views were used
to identify the VOT. For perceptual experiment, 4 adult native speakers of Tulu were asked to identify the stimulus from where
voicing was truncated in steps of 5 to 7 ms till lead VOT was 0 and silence was added after the burst in 5 msec steps till
the lag VOT was 50 msec. The reaction time and the accuracy in identification were measured. Results of acoustic measurement
showed no significant mean difference between lead VOTs of two voiced consonants. However, there was a significant difference
between means of lag VOTs of voiceless consonants. Results of Perceptual measurement showed that as lead VOT reduces, probability
of indentification of /g/ responses reduces; whereas changing VOT had little effect on reaction time and identification of
/b/ responses. These results probably indicate that VOT is not necessary to perceive voiceles constants in Tulu but is necessary
in the perception of voiced consonants. Thus VOT is a constant specific cue in Tulu. 相似文献
60.
Kazunori Nakano Shigendo Akita Nungruethai Yoswathananont Kazuki Sada Mikiji Miyata 《Journal of inclusion phenomena and macrocyclic chemistry》2004,48(3-4):181-184
Selective incorporation of two aromatic compounds, benzene and ethylbenzene,into an inclusion crystal of cholic acid was investigated. Addition of an excessamount of 1:1 mixture of benzene and ethylbenzene into saturated solution ofcholic acid in 1-butanol led to a spontaneous formation of an inclusion crystal.The co-crystal contained benzene and ethylbenzene at the constant molar ratioof 8:2 irrespective of the relative concentrations of guest and host in the feedsolution, indicating that the resulting crystal consists of the two guests mixedin a single host framework. The resulting ternary crystal had thermal behaviorsimilar to a binary crystal obtained from benzene. In contrast to the guest/hostratio, the benzene/ethylbenzene ratio in the feed solution affected that in theinclusion crystal. Benzene was basically preferred in the cholic acid crystalover ethylbenzene, but the selectivity reversed at an excess amount of ethylbenzene.This separation behavior can be understood in terms of the structural flexibility ofhost frameworks. 相似文献