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71.
72.
Total Synthesis and Functional Evaluation of Fourteen Derivatives of Lysocin E: Importance of Cationic,Hydrophobic, and Aromatic Moieties for Antibacterial Activity
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Takuya Kaji Dr. Motoki Murai Dr. Hiroaki Itoh Dr. Jyunichiro Yasukawa Dr. Hiroshi Hamamoto Prof. Dr. Kazuhisa Sekimizu Prof. Dr. Masayuki Inoue 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(47):16912-16919
Lysocin E ( 1 ) is a structurally complex 37‐membered depsipeptide comprising 12 amino‐acid residues with an N‐methylated amide and an ester linkage. Compound 1 binds to menaquinone (MK) in the bacterial membrane to exert its potent bactericidal activity. To decipher the biologically important functionalities within this unique antibiotic, we performed a comprehensive structure‐activity relationship (SAR) study by systematically changing the side‐chain structures of l ‐Thr‐1, d ‐Arg‐2, N‐Me‐d ‐Phe‐5, d ‐Arg‐7, l ‐Glu‐8, and d ‐Trp‐10. First, we achieved total synthesis of the 14 new side‐chain analogues of 1 by employing a solid‐phase strategy. We then evaluated the MK‐dependent liposomal disruption and antimicrobial activity against Staphylococcus aureus by 1 and its analogues. Correlating data between the liposome and bacteria experiments revealed that membrane lysis was mainly responsible for the antibacterial functions. Altering the cationic guanidine moiety of d ‐Arg‐2/7 to a neutral amide, and the C7‐acyl group of l ‐Thr‐1 to the C2 or C11 counterpart decreased the antimicrobial activities four‐ or eight‐fold. More drastically, chemical mutation of d ‐Trp‐10 to d ‐Ala‐10 totally abolished the bioactivities. These important findings led us to propose the biological roles of the side‐chain functionalities. 相似文献
73.
Yoshihisa Kurasawa Kiminari Yoshida Naoki Yamazaki Kotoji Iwamoto Yoshihiko Hamamoto Eisuke Kaji Kenji Sasaki Yoshito Zamami 《Journal of heterocyclic chemistry》2012,49(6):1323-1331
The 4‐quinolone‐2‐carboxylates 4a,b were converted into the 4‐quinolone‐2‐carbohydrazides 5a,b , hydrazones 6,7,10 , and related compounds 8,9,11 . The 4‐methoxyquinoline‐2‐carboxylate 12 was also transformed into the 4‐methoxyquinoline‐2‐carbohydrazide 13 , which was modified to the hydrazone 14 and related compound 15 . The antimicrobial activities of compounds 6b and 14 are described together with the 4‐oxo and 4‐hydroxy tautomers of compounds 4‐11 in deuteriodimethyl sulfoxide and deuteriotrifluoroacetic acid. 相似文献
74.
Yeon-Su Park Yukihiro Okamoto Noritada Kaji Manabu Tokeshi Yoshinobu Baba 《Journal of nanoparticle research》2011,13(11):5781-5798
We synthesized, in aqueous solution at room temperature, small water-soluble CdSe quantum dots (QDs) with strong photoluminescence
(PL) and then correlated the PL with their adsorption layer structure. For synthesizing the QDs, their initial synthesis condition
was controlled to form small Cd-containing species capable of passivating dangling bonds on the CdSe core surface. Each CdSe
QD (d ~ 2.5 nm) consisted of a CdSe core (d ~ 2.1 nm), a cysteine (cys)-ligand shell, and an adsorption layer composed of Cd–cys complexes (mainly CdL(-H)−, cys ≡ H2L), cys (as L2−), Cd(OH)2, and CdO
x
(x ≥ 1). Our CdSe QDs showed strong blue band-edge PL as well as strong green surface trap PL. Their PL quantum yield (QY) of
~18% was unexpectedly high, considering their extremely small core size and their absence of any wide-bandgap inorganic shell.
We attributed the QY to their adsorption layer species. The small weakly charged Cd–cys complex and the small neutral cadmium
oxides in the adsorption layer could relatively readily diffuse into the unprotected surface sites on the core. These wide-bandgap
species coalesced selectively on the unprotected surface sites with minimal spatial disturbance to the preexisting surface
Cd-ligand coordination, and passivated them effectively. These decreased nonradiative recombination of the excitons significantly
and thus led to the unexpectedly high QYs. 相似文献
75.
If G is a compact connected Lie group and T is a maximal torus, we give a wedge decomposition of ΣG/T by identifying families of idempotents in cohomology. This is used to give new information on the self-maps of G/T. 相似文献
76.
Yoshitsugu Kojima Arimitsu Usuki Masaya Kawasumi Akane Okada Toshio Kurauchi Osami Kamigaito Keisuke Kaji 《Journal of Polymer Science.Polymer Physics》1995,33(7):1039-1045
Nylon 6-clay hybrid (NCH) is a molecular composite of Nylon 6 and uniformly dispersed silicate monolayers of montmorillonite. In this study the preferred orientation of montmorillonite and Nylon-6 crystallites in a thick (3 mm) injection-molded bar of NCH has been investigated using x-ray diffraction and electron micrography (TEM). It is clear that this bar has a triple layer structure consisting of surface, intermediate, and middle layers which have different preferred orientation. In the surface layer both the silicate monolayers and the chain axes of Nylon-6 crystallites are parallel to the bar surface though the latter are randomly oriented within the plane. In the intermediate layer the silicate monolayers remain parallel to the bar surface but the Nylon-6 crystallites rotate by 90° so that the chain axes would be perpendicular to the bar surface or the silicate monolayers. In the middle layer the silicate monolayers are randomly oriented around the flow axis of the NCH bar while remaining parallel to it, and the Nylon crystallites are randomly oriented around the flow axis while keeping their chain axes perpendicular to the silicate monolayers. It may be concluded that such preferred orientation of Nylon 6 crystallites is induced by the clay because the crystallites in the pure Nylon 6 bar have no preferred orientation. ©1995 John Wiley & Sons, Inc. 相似文献
77.
78.
79.
The crystallite sizes of α and β forms of nylon 6 along the chain axis were determined by Wallner's method. First the shifts of the maximum positions of meridional reflections from their ideal reciprocal-lattice positions were calculated for the various crystallite sizes. Second, using these relationships, crystallite sizes were estimated from the observed maximum positions of reflections. The estimated values agree well with those from the integral widths of reflections by the method of Hosemann and Wilke. 相似文献
80.
Kaji Kano Yasuhiko Tanaka Teiichiro Ogawa Masatsugu Shimomura† Toyoki Kunitake† 《Photochemistry and photobiology》1981,34(3):323-329
Abstract— Photoresponsive artificial membranes have been prepared by embedding amphiphatic alkyl-ammonium salts containing azobenzene chromophore in dipalmitoylphosphatidylcholine liposomes. The configurational change due to trans→cis photoisomerization of the azobenzene chromophore provided the perturbation of the membrane structure to result in the increase of the water and bromo-thymol blue permeability of the liposomal membranes. 相似文献