Regulation of β-Sheet Structures within Amyloid-Like β-Sheet Assemblage from Tripeptide Derivatives
摘要:
N-(11-Trimethylammonioundecanoyl)-O,O'-didodecyl tripeptide bromides and N-(11-trimethylammonioundecanyl)-O-dodecyl tripeptide bromides formed a parallel P-sheet structure when they aggregated in water and in CCl4. The parallel beta-sheet was distinguished from the antiparallel counterpart by Fourier transform infrared spectroscopy because the former lacks a weak band at about 1690 cm(-1) that is characteristic for the latter. The FT-IR spectra of the aggregate in CCl4 remained unchanged if the solution was diluted to 0.01 mM, condensed to dryness, or heated to 60 degrees C, and hence, the beta-sheet was easily formed and thermodynamically stable. The parallel beta-sheet was also possible to transform into an antiparallel beta-sheet, for example, by mixing with another tripeptide-containing amphiphile whose tripeptide part had an opposite direction. Transmission electron microscope (TEM) and atomic force microscope (AFM) pictures revealed that the aggregate in CCl4 is a bundle of small filaments whose diameters are 70-80 Angstrom. Developed interpeptide hydrogen bonding should be formed along the long axis of the filament. The, morphological structures and stable peptide arrangements of the present assemblages are similar to those of the amyloid fiber whose accumulation causes fatal diseases.
Self-assembled hybrid supramolecular architectures formed between amphiphilic anions and long alkylated cationic cobalt(II) complexes of type [Co(Cn-terpy)2](C12-Glu)2 (n = 15–20) have been synthesized and characterized by TEM, PXRD and magnetic susceptibility measurements. The hybrids display wire or rolled sheet supramolecular arrangements with odd and even alkyl chain dependence, with the cobalt(II)
两亲性阴离子与长型[Co(C n -terpy)2 ](C 12 -Glu)2(n = 15-20)的长烷基化阳离子钴(II)配合物之间形成的自组装杂化超分子结构已被合成和表征通过TEM,PXRD和磁化率测量。杂种显示出具有奇数和偶数烷基链依赖性的金属丝或轧制薄板超分子排列,其中钴(II)中心表现出逐渐的自旋交叉行为。
Lipid-Packaged Linear Iron(II) Triazole Complexes in Solution: Controlled Spin Conversion via Solvophobic Self-Assembly
reversible spinconversion in toluene, with temperatures significantly higher (by 20-100 K) than the spin crossover temperatures observed in the crystalline states. This is accounted for in terms of increased metal-ligand interactions in organic media, which is caused by solvophobic compaction of charged coordination chains. In atomic force microscopy, developed nanowires are observed for low spin (LS) complexes
Silva, Monica de Lourdes de Araujo; Felicio, Emanoel de Castro Antunes, Bulletin de la Societe Chimique de France, 1997, vol. 134, # 7, p. 645 - 652
作者:Silva, Monica de Lourdes de Araujo、Felicio, Emanoel de Castro Antunes
DOI:——
日期:——
Self-assembly of bilayers from double-chain fluorocarbon amphiphiles in aprotic organic solvents: thermodynamic origin and generalization of the bilayer assembly
We designed new fluorocarbon amphiphiles, 3-7, that undergo spontaneous bilayer formation in organic media. They are comprized of double fluorocarbon chains and a single oleyl chain as solvophobic and solovophilic moieties, respectively. These two molecular modules were linked through the chiral L-glutamate residue. When dispersed in chlorocyclohexane or benzene, these amphiphiles formed stable bilayer assemblies that gave rise to morphologies such as tubes, tapes, rods, and particles as confirmed by electron microscopy. These dispersions showed bilayer/monomer phase transitions as inferred by differential scanning calorimetry. This phase transition was accompanied by changes of the helical pitch of the fluorocarbon conformation and of intermolecular hydrogen bonding among the glutamate moiety. From the surface tension analysis of adsorbed monolayers at the air/liquid interface, we concluded that the bilayer formation in bulk chlorocyclohexane was driven by the enthalpic change. Limited miscibilities between fluorocarbon chains and hydrocarbon solvents produced the main enthalpic driving force of the molecular association, and the hydrogen bonding and van der Waals force of the aromatic moieties served as secondary driving forces. The molar fraction at CMC (critical membrane or micelle concentration), which reflects instability of aggregates, was greater than those of aqueous bilayers (below 10(-7)) but smaller than those of aqueous micelles (above 10(-4)). The chromophoric bilayers 6 (Phe-Ole) and 7 (Azo-Ole) showed large molecular ellipticities of 10(5)-10(6) deg.cm(2).dmol(-1) in their CD spectra, Molecular ordering in the novel bilayers was not inferior to those of conventional aqueous bilayers, although their bilayer stability does not surpass that of aqueous bilayers.
Okahata, Yoshio; Niikura, Ken-ichi; Ijiro, Kuniharu, Journal of the Chemical Society. Perkin transactions I, 1995, # 7, p. 919 - 926