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1.
The accumulation and deposition of β-amyloid (Aβ) plaques in the brain is considered a potential pathogenic mechanism underlying Alzheimer's disease (AD). Chiral l/d -FexCuySe nanoparticles (NPs) were fabricated that interfer with the self-assembly of Aβ42 monomers and trigger the Aβ42 fibrils in dense structures to become looser monomers under 808 nm near-infrared (NIR) illumination. d -FexCuySe NPs have a much higher affinity for Aβ42 fibrils than l -FexCuySe NPs and chiral Cu2−xSe NPs. The chiral FexCuySe NPs also generate more reactive oxygen species (ROS) than chiral Cu2−xSe NPs under NIR-light irradiation. In living MN9D cells, d -NPs attenuate the adhesion of Aβ42 to membranes and neuron loss after NIR treatment within 10 min without the photothermal effect. In-vivo experiments showed that d -FexCuySe NPs provide an efficient protection against neuronal damage induced by the deposition of Aβ42 and alleviate symptoms in a mouse model of AD, leading to the recovery of cognitive competence.  相似文献   

2.
In the present study, chiral CuxCoyS nanoparticles (NPs) were developed to selectively induce apoptosis of senescent cells using both an alternating magnetic field (AMF) and near infrared (NIR) photon illumination. The chiral effects on living cells were investigated, and d ‐CuxCoyS NPs showed about 2.5 times higher of internalized ability than l ‐NPs. By modifying beta 2 macroglobulin (MG), senescent cells were effectively eliminated by d ‐CuxCoyS NPs without damaging the activities of normal cells under AMF and photon illumination. Compared to the individual application of NIR illumination and AMF, their synergistic effect induced the production of caspase‐3 with a much shorter treatment time and higher efficiency due to the more serious photon‐induced cellular redox and mechanical damage of cellular skeleton. Moreover, the developed strategy was successfully used to remove senescent cells in vivo. This study developed a controllable way of regulating cell activities using chiral NPs, which will provide a valuable way for treating diseases and promoting health.  相似文献   

3.
A series of five l ‐di‐p‐toluoyl‐tartaric acid (l ‐DTTA) lanthanide coordination polymers, namely {[Ln4K4 L6(H2O)x]?yH2O}n, [Ln=Dy ( 1 ), x=24, y=12; Ln=Ho ( 2 ), x=23, y=12; Ln=Er ( 3 ), x=24, y=12; Ln=Yb ( 4 ), x=24, y=11; Ln=Lu ( 5 ), x=24, y=12] have been isolated by simple reactions of H2L (H2L= L ‐DTTA) with LnCl3?6 H2O at ambient temperature. X‐ray crystallographic analysis reveals that complexes 1 – 5 feature two‐dimensional (2D) network structures in which the Ln3+ ions are bridged by carboxylate groups of ligands in two unique coordinated modes. Luminescent spectra demonstrate that complex 1 realizes single‐component white‐light emission, while complexes 2 – 4 exhibit a characteristic near‐infrared (NIR) luminescence in the solid state at room temperature.  相似文献   

4.
Superconducting [(Li1?xFex)OH](Fe1?yLiy)Se (x≈0.2, y≈0.08) was synthesized by hydrothermal methods and characterized by single‐crystal and powder X‐ray diffraction. The structure contains alternating layers of anti‐PbO type (Fe1?yLiy)Se and (Li1?xFex)OH. Electrical resistivity and magnetic susceptibility measurements reveal superconductivity at 43 K. An anomaly in the diamagnetic shielding indicates ferromagnetic ordering near 10 K while superconductivity is retained. The ferromagnetism is from the iron atoms in the (Li1?xFex)OH layer. Isothermal magnetization measurements confirm the superposition of ferromagnetic and superconducting hysteresis. The internal ferromagnetic field is larger than the lower, but smaller than the upper critical field of the superconductor. The formation of a spontaneous vortex phase where both orders coexist is supported by 57Fe‐Mössbauer spectra, 7Li‐NMR spectra, and μSR experiments.  相似文献   

5.
The design and synthesis of β‐peptides from new C‐linked carbo‐β‐amino acids (β‐Caa) presented here, provides an opportunity to understand the impact of carbohydrate side chains on the formation and stability of helical structures. The β‐amino acids, Boc‐(S)‐β‐Caa(g)‐OMe 1 and Boc‐(R)‐β‐Caa(g)‐OMe 2 , having a D ‐galactopyranoside side chain were prepared from D ‐galactose. Similarly, the homo C‐linked carbo‐β‐amino acids (β‐hCaa); Boc‐(S)‐β‐hCaa(x)‐OMe 3 and Boc‐(R)‐β‐hCaa(x)‐OMe 4 , were prepared from D ‐glucose. The peptides derived from the above monomers were investigated by NMR, CD, and MD studies. The β‐peptides, especially the shorter ones obtained from the epimeric (at the amine stereocenter Cβ) 1 and 2 by the concept of alternating chirality, showed a much smaller propensity to form 10/12‐helices. This substantial destabilization of the helix could be attributed to the bulkier D ‐galactopyranoside side chain. Our efforts to prepare peptides with alternating 3 and 4 were unsuccessful. However, the β‐peptides derived from alternating geometrically heterochiral (at Cβ) 4 and Boc‐(R)‐β‐Caa(x)‐OMe 5 (D ‐xylose side chain) display robust right‐handed 10/12‐helices, while the mixed peptides with alternating 4 and Boc‐β‐hGly‐OMe 6 (β‐homoglycine), resulted in left‐handed β‐helices. These observations show a distinct influence of the side chains on helix formation as well as their stability.  相似文献   

6.
The title compound, [Cu2(C9H10NO3)2(NO3)2(C10H8N2)(H2O)2]n, contains CuII atoms and l ‐tyrosinate (l ‐tyr) and 4,4′‐bipyridine (4,4′‐bipy) ligands in a 2:2:1 ratio. Each Cu atom is coordinated by one amino N atom and two carboxylate O atoms from two l ‐tyr ligands, one N atom from a 4,4′‐bipy ligand, a monodentate nitrate ion and a water molecule in an elongated octahedral geometry. Adjacent Cu atoms are bridged by the bidentate carboxylate groups into a chain. These chains are further linked by the bridging 4,4′‐bipy ligands, forming an undulated chiral two‐dimensional sheet. O—H...O and N—H...O hydrogen bonds connect the sheets in the [100] direction. This study offers useful information for the engineering of chiral coordination polymers with amino acids and 4,4′‐bipy ligands by considering the ratios of the metal ion and organic components.  相似文献   

7.
Polyol Metal Complexes.471) Crystalline D ‐Mannose‐Copper Complexes from Fehling Solutions Blue, unstable crystals of K3[Cu5(β‐D ‐Manp)4H—13] · α‐D ‐Manp · 16.5 H2O ( 1 ), which contain a pentanuclear cupric complex of the reducing sugar D ‐mannose in its β‐pyranose form (β‐D ‐Manp), have been obtained from ice‐cold aqueous alkaline solutions. The homoleptic pentacuprate contains bridging mannopyranose ligands, which are charged 4— and 2.5—. Addition of ethylenediamine (en) to such Fehling solutions yields N, N′‐Bis(β‐D ‐mannopyranosyl)‐ethylenediamine (L) as a condensation product of the diamine and mannopyranose. Crystals of [(en)2Cu7(β‐D ‐Manp1, 2, 3, 4H—4)2(L2, 3, 4H—3)2] · 26.6 H2O ( 2 ) could be isolated. The heptanuclear cupric complex is a structural derivative of the homoleptic mannose complex.  相似文献   

8.
A method for the region‐selective deposition of nanoparticles (NPs) by the Huisgen 1,3‐dipolar cycloaddition is presented. The approach enables defined stacking of various oxide NPs in any order with control over layer thickness. Thereby the reaction is performed between a substrate, functionalized with a self‐assembled monolayer of an azide‐bearing phosphonic acid (PA) and aluminum oxide (AlOx) NPs functionalized with an alkyne bearing PA. The layer of alkyne functionalized AlOx NPs is then used as substrate for the deposition of azide‐functionalized indium tin oxide (ITO) NPs to provide a binary stack. This progression is then conducted with alkyne‐functionalized CeO2 NPs, yielding a ternary stack of NPs with three different NP cores. The stacks are characterized by AFM and SEM, defining the region‐selectivity of the deposition technique. Finally, these assemblies have been tested in devices as a dielectric to form a capacitor resulting in a dramatic increase in the measured capacitance.  相似文献   

9.
A novel amphiphilic copolymer was synthesized from poly (ethylene glycol) methyl ether methacrylate (PEGMA950), methyl methacrylate (MMA) and acryloyl‐β‐cyclodextrin (acryloyl‐β‐CD) using the composites of (NH4)2S2O8/NaHSO3 as the oxidation–reduction initiators. The successful fabrication of poly(PEGMA‐co‐MMA‐co‐acryloyl‐β‐CD) copolymers was confirmed by Fourier transform infrared spectrometer (FTIR), 1H‐nuclear magnetic resonance (1H NMR) spectra. The amphiphilic copolymer could self‐assemble into nanoparticles (NPs), and their morphology and particle size distribution were characterized with transmission electron microscopy (TEM), atomic force microscope (AFM) and dynamic light scattering (DLS) methods. Ibuprofen (IBU) was encapsulated in the novel NPs, and the release profiles of IBU were investigated. FTIR and 1H NMR spectra illustrated that the poly(PEGMA‐co‐MMA‐co‐acryloyl‐β‐CD) copolymers were synthesized without any residual monomers and initiators. TEM and AFM photographs suggested that the obtained NPs were spherical, and the DLS results indicated that the diameter of blank NPs was 157.3 ± 32.7 nm. The IBU release profile showed that the IBU‐loaded NPs had certain pH responsibility. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

10.
Convergent syntheses of the 9‐(3‐X‐2,3‐dideoxy‐2‐fluoro‐β‐D ‐ribofuranosyl)adenines 5 (X=N3) and 7 (X=NH2), as well as of their respective α‐anomers 6 and 8 , are described, using methyl 2‐azido‐5‐O‐benzoyl‐2,3‐dideoxy‐2‐fluoro‐β‐D ‐ribofuranoside ( 4 ) as glycosylating agent. Methyl 5‐O‐benzoyl‐2,3‐dideoxy‐2,3‐difluoro‐β‐D ‐ribofuranoside ( 12 ) was prepared starting from two precursors, and coupled with silylated N6‐benzoyladenine to afford, after deprotection, 2′,3′‐dideoxy‐2′,3′‐difluoroadenosine ( 13 ). Condensation of 1‐O‐acetyl‐3,5‐di‐O‐benzoyl‐2‐deoxy‐2‐fluoro‐β‐D ‐ribofuranose ( 14 ) with silylated N2‐palmitoylguanine gave, after chromatographic separation and deacylation, the N7β‐anomer 17 as the main product, along with 2′‐deoxy‐2′‐fluoroguanosine ( 15 ) and its N9α‐anomer 16 in a ratio of ca. 42 : 24 : 10. An in‐depth conformational analysis of a number of 2,3‐dideoxy‐2‐fluoro‐3‐X‐D ‐ribofuranosides (X=F, N3, NH2, H) as well as of purine and pyrimidine 2‐deoxy‐2‐fluoro‐D ‐ribofuranosyl nucleosides was performed using the PSEUROT (version 6.3) software in combination with NMR studies.  相似文献   

11.
The reaction of racemic α‐keto β‐lactams 5a – 5c with the commercially available chiral compound trans‐4‐hydroxy‐L ‐proline ( 6 ) in the presence of a catalytic amount of Bi(NO3)3?5 H2O in EtOH gave a diastereoisomer mixture of β‐lactams with a pyrrole ring at C(3) ( 7 to 12 ). This is the first enantioselective synthesis of optically active β‐lactams (=azetidin‐2‐ones) that possess a pyrrolyl residue at C(3), in a single step.  相似文献   

12.
Oriented circular dichroism (OCD) is explored and successfully applied to investigate chiral surface‐anchored metal–organic frameworks (SURMOFs) based on camphoric acid (D‐ and Lcam) with the composition [Cu2(Dcam)2x(Lcam)2?2x(dabco)]n (dabco=1,4‐diazabicyclo‐[2.2.2]‐octane). The three‐dimensional chiral SURMOFs with high‐quality orientation were grown on quartz glass plates by using a layer‐by‐layer liquid‐phase epitaxy method. The growth orientation, as determined by X‐ray diffraction (XRD), could be switched between the [001] and [110] direction by using either OH‐ or COOH‐terminated substrates. These SURMOFs were characterized by using OCD, which confirmed the ratio as well as the orientation of the enantiomeric linker molecules. Theoretical computations demonstrate that the OCD band intensities of the enantiopure [Cu2(Dcam)2(dabco)]n grown in different orientations are a direct result of the anisotropic nature of the chiral SURMOFs. Finally, the enantiopure [Cu2(Dcam)2(dabco)]n and [Cu2(Lcam)2(dabco)]n SURMOFs were loaded with the two chiral forms of ethyl lactate [(+)‐ethyl‐D ‐lactate and (?)‐ethyl‐L ‐lactate)]. An enantioselective enrichment of >60 % was observed by OCD when the chiral host scaffold was loaded from the racemic mixture.  相似文献   

13.
A microwave‐assisted glycosylation method was developed for efficient synthesis of oligosaccharides. Di‐functional AB monomers, 2,3,4‐tri‐O‐acetyl‐α‐d ‐galactopyranosyl bromide ( 3a ) and 2,3,4‐tri‐O‐acetyl‐α‐d ‐glucopyranosyl bromide ( 3b ) were designed and synthesized as weakly reactive monomers to avoid unwanted glycosylation or degradation during preparation and storage. The glycosylations of these monomers gave low conversions and low molecular weight oligosaccharides at rt, reflux, and under low microwave energy irradiation. However, the glycosylation became very effective when high microwave energy was applied, giving 100% conversion and producing oligosaccharides with Mn = 4.76 kDa for 3a and Mn = 4.05 kDa for 3b. The acetylated oligosaccharides were further subjected to deprotection for structural analysis, which indicated the oligosaccharides contain predominantly linear β‐(1,6)‐glycosyl linkages. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3693–3699  相似文献   

14.
Three pairs of enantiopure chiral triangular Ln3 clusters, [Ln3LRRRRRR/SSSSSS3‐OH)2(H2O)2(SCN)4]?xCH3OH?yH2O ( R ‐Dy3 , Ln=Dy, x=6, y=0; S ‐Dy3 , Ln=Dy, x=6, y=1; R ‐Ho3 , Ln=Ho, x=6, y=1; S ‐Ho3 , Ln=Ho, x=6, y=1; R ‐Er3 , Ln=Er, x=6, y=0; S ‐Er3 , Ln=Er, x=6, y=1), have been successfully synthesized by a rational enantioselective synthetic strategy. The core of triangular Ln3 is bound in the central N6O3 of the macrocyclic ligand, and the coordination spheres of Ln ions are completed by four SCN? anions and two H2O molecules in axial positions of the macrocycle. The circular dichroism (CD) and vibrational circular dichroism (VCD) spectra of the enantiomers demonstrate that the chirality is successfully transferred from the ligands to the resulting Ln3 clusters. Ac susceptibility measurements reveal that single‐molecule magnet behavior occurs for both enantiopure clusters of R ‐Dy3 and S ‐Dy3 . This work is one of the few examples of the successful design of a pair of triangular Dy3 clusters showing simultaneously slow magnetic relaxation and optical activity, and this might open up new opportunities to develop novel multifunctional materials.  相似文献   

15.
In this study, structural and mechanical properties of a series of models of Aβ42 (one‐ and two‐fold) and Aβ40 (two‐ and three‐fold) fibrils have been computed by using all‐atom molecular dynamics simulations. Based on calculations of the twist angle (θ) and periodicity (v=360d/θ), oligomers formed by 20, 11, and 13 monomers were found to be the smallest realistic models of three‐fold Aβ40, one‐fold Aβ42, and two‐fold Aβ42 fibrils, respectively. Our results predict that the Aβ40 fibrils initially exist in two staggered conformations [STAG(+2) and STAG(+1)] and then undergo a [STAG(+2)→STAG(+1)] transformation in a size‐dependent manner. The length of the loop region consisting of the residues 23–29 shrinks with the elongation of both Aβ40 and Aβ42 fibrils. A comparison of the computed potential energy suggests that a two‐fold Aβ40 aggregate is more stable than its three‐fold counterpart, and that Aβ42 oligomers can exist only in one‐fold conformation for aggregates of more than 11 monomers in length. The computed Young′s modulus and yield strengths of 50 GPa and 0.95 GPa, respectively, show that these aggregates possess excellent material properties.  相似文献   

16.
Aggregated β‐amyloid (Aβ) is widely considered as a key factor in triggering progressive loss of neuronal function in Alzheimer's disease (AD), so targeting and inhibiting Aβ aggregation has been broadly recognized as an efficient therapeutic strategy for curing AD. Herein, we designed and prepared an organic platinum‐substituted polyoxometalate, (Me4N)3[PW11O40(SiC3H6NH2)2PtCl2] (abbreviated as PtII‐PW11) for inhibiting Aβ42 aggregation. The mechanism of inhibition on Aβ42 aggregation by PtII‐PW11 was attributed to the multiple interactions of PtII‐PW11 with Aβ42 including coordination interaction of Pt2+ in PtII‐PW11 with amino group in Aβ42, electrostatic attraction, hydrogen bonding and van der Waals force. In cell‐based assay, PtII‐PW11 displayed remarkable neuroprotective effect for Aβ42 aggregation‐induced cytotoxicity, leading to increase of cell viability from 49 % to 67 % at a dosage of 8 μm . More importantly, the PtII‐PW11 greatly reduced Aβ deposition and rescued memory loss in APP/PS1 transgenic AD model mice without noticeable cytotoxicity, demonstrating its potential as drugs for AD treatment.  相似文献   

17.
A novel method for the asymmetric synthesis of α,β‐diamino acids by using the 2,3,4,6‐tetra‐O‐pivaloyl‐β‐D ‐glucopyranosyl group (Piv4Glc) as chiral auxiliary was developed (Table and Scheme). The reaction was promoted by CuBr?Me2S as Lewis acid, and high yields and good diastereoselectivities were achieved.  相似文献   

18.
A porous perovskite BaCoxFeyZr0.9?x?yPd0.1O3?δ (BCFZ‐Pd) coating was deposited onto the outer surface of a BaCoxFeyZr1?x?yO3?δ (BCFZ) perovskite hollow‐fiber membrane. The surface morphology of the modified BCFZ fiber was characterized by scanning electron microscopy (SEM), indicating the formation of a BCFZ‐Pd porous layer on the outer surface of a dense BCFZ hollow‐fiber membrane. The oxygen permeation flux of the BCFZ membrane with a BCFZ‐Pd porous layer increased 3.5 times more than that of the blank BCFZ membrane when feeding reactive CH4 onto the permeation side of the membrane. The blank BCFZ membrane and surface‐modified BCFZ membrane were used as reactors to shift the equilibrium of thermal water dissociation for hydrogen production because they allow the selective removal of the produced oxygen from the water dissociation system. It was found that the hydrogen production rate increased from 0.7 to 2.1 mL H2 min?1 cm?2 at 950 °C after depositing a BCFZ‐Pd porous layer onto the BCFZ membrane.  相似文献   

19.
The 1,3,4,6‐tetra‐O‐acetyl‐2‐azido‐2‐deoxy‐β‐D ‐mannopyranose ( 4 ) or the mixture of 1,3,6‐tri‐O‐acetyl‐2‐azido‐2‐deoxy‐4‐O‐(2,3,4,6‐tetra‐O‐acetyl‐β‐D ‐galactopyranosyl)‐β‐D ‐mannopyranose ( 10 ) and the corresponding α‐D ‐glucopyranose‐type glycosyl donor 9 / 10 reacted at room temperature with protected nucleosides 12 – 15 in CH2Cl2 solution in the presence of BF3?OEt2 as promoter to give 5′‐O‐(2‐azido‐2‐deoxy‐α‐D ‐glycosyl)nucleosides in reasonable yields (Schemes 2 and 3). Only the 5′‐O‐(α‐D ‐mannopyranosyl)nucleosides were obtained. Compounds 21, 28, 30 , and 31 showed growth inhibition of HeLa cells and hepatoma Bel‐7402 cells at a concentration of 10 μM in vitro.  相似文献   

20.
A wealth of epidemiological evidence indicates a strong link between type 2 diabetes (T2D) and Alzheimer's disease (AD). The fiber deposition with cross‐β‐sheet structure formed by self‐aggregation and misfolding of amyloidogenic peptides is a common hallmark of both diseases. For the patients with T2D, the fibrils are mainly found in the islets of Langerhans that results from the accumulation of human islet amyloid polypeptide (hIAPP). The major component of aggregates located in the brain of AD patients is amyloid‐β (Aβ). Many biophysical and physiological properties are shared by hIAPP and Aβ, and both peptides show similar cytotoxic mechanisms. Therefore, it is meaningful to investigate the possible cross‐interactions of hIAPP and Aβ in both diseases. In this article, the segment 25–35 of Aβ was selected because Aβ25–35 was a core region in the process of amyloid formation and showed similar aggregation tendency and toxicity with full‐length Aβ. The electrospray ionization‐ion mobility‐mass spectrometry analysis and thioflavin T fluorescence kinetic analysis combined with transmission electron microscopy were used to explore the effects of the coexistence of Aβ25–35 and hIAPP on the self‐aggregation of both peptides and whether there was co‐assembly in fibrillation. The results indicated that the aggregation of hIAPP and Aβ25–35 had two nucleation stages in the binary mixtures. hIAPP and Aβ25–35 had a high binding affinity and a series of hetero‐oligomers formed in the mixtures of hIAPP and Aβ25–35 in the early stage. The cross‐reaction between hIAPP monomers and Aβ25–35 monomers as well as a little of oligomers during primary nucleation stage could accelerate the aggregation of Aβ25–35. However, owing to the obvious difference in aggregation ability between hIAPP and Aβ25–35, this cross‐interaction had no significant impact on the self‐assembly of hIAPP. Our study may offer a better understanding for exploring the molecular mechanism of the association between AD and T2D observed in clinical and epidemiological studies and developing therapeutic strategies against amyloid diseases.  相似文献   

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