The Aggregation Potential of the 1–15- and 1–16-Fragments of the Amyloid β Peptide and Their Influence on the Aggregation of Aβ40

The aggregation of amyloid β (Aβ) peptide is important in Alzheimer’s disease. Shorter Aβ fragments may reduce Aβ’s cytotoxicity and are used in diagnostics. The aggregation of Aβ16 is controversial; Liu et al. (J. Neurosci. Res. 75:162–171, 2004) and Liao et al. (FEBS Lett. 581:1161–1165, 2007) find that Aβ16 does not aggregate and reduces Aβ’s cytotoxicity, Du et al. (J. Alzheimer’s Dis. 27:401–413, 2011) reports that Aβ16 aggregates and that Aβ16 oligomers are toxic to cells. Here the aggregation potential of two shorter fragments, Aβ15 and Aβ16, and their influence on Aβ40 is measured by electron paramagnetic resonance (EPR) spectroscopy and the ThioT fluorescence assay (ThioT). Continuous-wave, 9 GHz EPR measurements and ThioT results reveal that neither Aβ15 nor Aβ16 aggregate by themselves and that they do not affect Aβ40 aggregation.     

Development of polymethacrylate nanospheres as targeted delivery systems for catechin within the gastrointestinal tract

In this study, pH-sensitive nanospheres were fabricated using a polymethacrylate-based copolymer to encapsulate, protect, and release catechin, and thereby overcome its poor water solubility and low oral bioaccessibility. The polymer used was a polymethacrylic acid-co-ethyl acrylate 1:1 copolymer that dissolves above pH 5.5, and so can be used to retain and protect bioactives within the stomach but releases them in the small intestine. Catechin-loaded nanospheres were fabricated using the solvent displacement method. Physicochemical characterization of the nanospheres indicated that they were relatively small (d = 160 nm) and had a high negative charge (ζ = ? 36 mV), which meant that they had good stability to aggregation under physiological conditions (pH 7.2). Catechin was trapped within the nanospheres at an encapsulation efficiency of about 51% in an amorphous state. A simulated gastrointestinal study showed that catechin was slowly released under gastric conditions (pH 2.5), but rapidly released under small intestine conditions (pH 7.2). The observed improvement in the antioxidant activity and bioaccessibility of catechin after encapsulation was attributed to the fact that it was in an amorphous state and had good water dispersibility. This study provides useful information for the formulation of novel delivery systems to improve the dispersibility, bioaccessibility, and bioactivity of catechin and potentially other active components. These delivery systems could be used to improve the efficacy of bioactive components in foods, supplements, and pharmaceutical products.     

Probing the role of metal cations on the aggregation behavior of amyloid β-peptide at a single molecule level by AFM

With the development of nanotechnology, understanding of intermolecular interactions on a single molecule level by atomic force spectroscopy (AFM) has played an important role in molecular biology and biomedical science. In recent years, some research suggested that the presence of metal cations is an important regulator in the processes of misfolding and aggregation of the amyloid β-protein (Aβ), which may be an important etiological factor of Alzheimer’s disease. However, the knowledge on the principle of interactions between Aβ and metal cations at the single molecule level is still poor understood. In this paper, the amyloid β-protein (Aβ) was fabricated on substrate of mixed thiol-modified gold nanoparticles using self-assembled monolayer method and the adhesion force in the longitudinal direction between metal cations and Aβ42 were investigated by AFM. The role of metal ions on Aβ aggregation is discussed from the perspective of single molecular force. The force results showed that the specific adhesion force F _i and the nonspecific force F ₀ between a single Aβ–Aβ pair in control experiment were calculated as 42 ± 3 and 80 pN, respectively. However, F _i between a single Aβ–Aβ pair in the presence of Cu²⁺, Zn²⁺, Ca²⁺ and Al³⁺ increased dramatically to 84 ± 6, 89 ± 3, 73 ± 5, 95 ± 5 pN successively, which indicated that unbinding between Aβ proteins is accelerated in the presence of metal cations. What is more, the imaging results showed that substoichiometric copper cations accelerate the formation of fibrils within 3 days. The combined atomic force spectroscopy and imaging analysis indicate that metal cations play a role in promoting the aggregating behavior of Aβ42.     

Synthesis of NiCo2S4 nanospheres/reduced graphene oxide composite as electrode material for supercapacitor

The NiCo₂S₄ nanospheres arrayed on the surface of reduced graphene oxide (rGO) was fabricated via one-step hydrothermal method. The effect of initial feeding mass of Ni(NO₃)₂·6H₂O and Co(NO₃)₂·6H₂O to rGO on the microstructure and electrochemical performance of the as-prepared composites was studied. The results indicated that the specific capacitances of the composites were first increased and then reduced due to the aggregation of NiCo₂S₄ nanospheres. NiCo₂S₄ nanospheres/rGO composites exhibited a remarkable specific capacitance of 1406 F/g and excellent cyclic stability of 82.36% at the current density of 1 A/g, which were better than those of individual NiCo₂S₄ (792 F/g and 64.77%) counterpart. These results showed that the as-prepared NiCo₂S₄ nanospheres/rGO composites were outstanding candidate for electrode material of supercapacitors.     

The use of a combinatorial library method to isolate human tumor cell adhesion peptides

Summary Tumor cell progression is dependent in part on the successful adhesive interactions of the cells with the extracellular matrix. In this study, a new approach is described to isolate linear peptide ligand candidates involved in cellular adhesion. A synthetic combinatorial peptide library based on the one-bead-one-peptide concept was incubated with live human prostate cancer cells for 90 min at 37 °C. The peptide bead coated with a monolayer of cells was then isolated for micro sequencing. The DU145 (DU-H) cells were chosen since they have been previously characterized as containing elevated levels of a laminin receptor for cell adhesion, the ₆₁ integrin on the cell surface. The use of a function-blocking antibody (GoH3) allows for the detection of peptides which are ₆-specific ligand candidates. From two different libraries (linear 9-mer and 11-mer) of a total of 1 500 000 beads, 68 peptide beads containing attached cells were isolated. These positive beads were then retested to determine the ability of the GoH3 antibody to block binding of the cells to the peptide beads. The ₆ integrin candidate peptide beads (five in total) were recovered and two of the beads were microsequenced. These two peptides, RU-1 (LNIVSVNGRHX) and RX-1 (DNRIRLQAKXX), resemble the previously reported active peptide sequences (GD-2 and AG-73) from native laminin. The RU-1, RX-1 and AG-73 peptides were tested for their ability to support cell attachment and to bind the cell surface of DU-H prostate carcinoma cells in suspension using fluorescence-activated cell-sorting (FACS) analysis. Both RU-1 and AG-73 peptides supported cellular attachment within 1 h. In contrast, after 1 h, EHS laminin supported both cellular attachment and spreading. The RX-1 peptide exhibited only weak binding to the DU-H prostate carcinoma cells. FACS analysis indicated that AG-73 peptide attached to tumor cell surfaces over a range of concentrations, whereas the RU-1 peptide showed a homogeneous concentration required for attachment. The described strategy for screening a random peptide library offers three advantages: (i) ligands for conformationally sensitive receptors of adhesion can be isolated using live cells; (ii) specific binding can be selected for using function-blocking antibodies; and (iii) peptides supporting adhesion independent of spreading properties can be distinguished. In principle, specific adhesive peptides without prior knowledge of the sequence could be isolated for any epithelial cell surface receptor for which a function-blocking reagent is available.     

Neuroprotective effects of edaravone-administration on 6-OHDA-treated dopaminergic neurons

Background

A recent human clinical trial of an Alzheimer's disease (AD) vaccine using amyloid beta (Aβ) 1–42 plus QS-21 adjuvant produced some positive results, but was halted due to meningoencephalitis in some participants. The development of a vaccine with mutant Aβ peptides that avoids the use of an adjuvant may result in an effective and safer human vaccine.

Results

All peptides tested showed high antibody responses, were long-lasting, and demonstrated good memory response. Epitope mapping indicated that peptide mutation did not lead to epitope switching. Mutant peptides induced different inflammation responses as evidenced by cytokine profiles. Ig isotyping indicated that adjuvant-free vaccination with peptides drove an adequate Th2 response. All anti-sera from vaccinated mice cross-reacted with human Aβ in APP/PS1 transgenic mouse brain tissue.

Conclusion

Our study demonstrated that an adjuvant-free vaccine with different Aβ peptides can be an effective and safe vaccination approach against AD. This study represents the first report of adjuvant-free vaccines utilizing Aβ peptides carrying diverse mutations in the T-cell epitope. These largely positive results provide encouragement for the future of the development of human vaccinations for AD.     

Formation of Sn@C Yolk–Shell Nanospheres and Core–Sheath Nanowires for Highly Reversible Lithium Storage

As one promising anode material with high theoretical capacity, metallic tin has attracted much research interest in the field of lithium‐ion batteries. Here, two types of tin/carbon (Sn@C) core–shell nanostructures with inner buffering voids are fabricated from SnO₂ hollow nanospheres via a facile chemical vapor deposition (CVD) method. The crystallinity and surface topography of SnO₂ hollow nanospheres are found to affect the morphology of resultant Sn@C materials. Sn@C yolk–shell nanospheres and core–sheath nanowires are obtained from the as‐prepared SnO₂ and high‐temperature annealed SnO₂ nanospheres, respectively. The unique Sn@C nanostructures can mitigate the agglomeration/pulverization of Sn nanoparticles and electrical disconnection from the current collector caused by the large volume change during the lithium alloying/dealloying process. Both Sn@C yolk–shell and core–sheath nanostructures show stable cycling performance up to 500 cycles with specific capacities of ca. 430 and 520 mA h g^?1, respectively.     

Identification of peptide sequences that bind the Thomsen-Friedenreich cancer-associated glycoantigen from bacteriophage peptide display libraries

Summary The goal of this study was to determine if polypeptides that bind specifically to the carcinoma-associated Thomsen-Friedenreich (T) antigen could be isolated from a random peptide bacteriophage display library. T antigen is a carbohydrate antigen that is exposed and immunoreactive on the surfaces of most primary carcinomas and their metastases, while it is masked on normal cells. Tumor-specific surface carbohydrates are often used as markers of cell differentiation and play a role in cell aggregation, which is an important step in the metastatic process. Therefore, peptides that bind and mask T antigen may yield useful carbohydrate-specific probes and provide insight into carbohydrate-mediated tumor-cell aggregation. A 15-amino acid random peptide bacteriophage display library was screened for polypeptides that exhibited high specificity to two glycoproteins which display T antigen on their surfaces. The results suggest that synthetic peptides identified from the bacteriophage display library have high affinities (K_d 1 M) and specificities for proteins and human tumor cells which present T antigen. Thus, random bacteriophage peptide display libraries may be a rich source of sequences that bind to carbohydrate antigen structures.     

阿尔茨海默氏症致病蛋白－Aβ(12-28) 肽段的NMR研究

Aβ肽的多聚化和纤维化在阿尔茨海默氏症(Alzheimer's diseas)的发生中起关键作用, 其中以Aβ_(1-42) 的致病作用为最强,因此阻断其聚集成为阿尔茨海默氏症一种潜在的治疗方式. 作者在研究中发现某些化合物可以结合于Aβ_(12-28) 肽段. 该文采用¹H-¹H COSY、TOCSY、ROESY和¹⁵N-HSQC多种核磁分析方法, 对此肽段的¹H和¹⁵N NMR谱信号进行了归属和详细分析,为进一步研究其与小分子抑制剂的相互作用提供了基础.     

Hydrogel nanoparticles covered by neuroligin-2-derived peptide-protected <Emphasis Type="Italic">β</Emphasis> cells under oxidative stress and increase their proliferation

Protein complexes that mediate secretion and adhesion are located on the plasma membrane of pancreatic β cells. Neuroligins and their binding partners, the neurexins, are among these complexes. β cell maturation and physiologically regulated insulin secretion, as a response to high levels of blood glucose, are dependent on their three-dimensional (3D) arrangement. Both insulin secretion and the proliferation rates of β cells dramatically increase when β cells are co-cultured with clusters of a member of the neuroligin family: NL-2. A membranal protein, such as NL-2, has very limited drugability owing to its low biostability and bioavailability. Thus, based on in silico modeling, a short NL-2 peptide (HSA-28), which was able to mimic NL-2-positive effects on β cells, was designed, as we described in previous publication. However, the peptide was active only as a cluster, created by the covering the maghemite (γ-Fe₂O₃)-based nanoparticles (NPs) with limited biocompatibility. In this brief communication, we will show that conjugation of HSA-28 to biocompatible hydrogel NPs exhibits an impressive protective effect on INS-1E β cells under oxidative stress and induces their proliferation rate via augmentation of PDX1 nuclear translocation. The diameter of coated by the peptide NPs was 206?±?63 nm (DLS) and 114?±?27 nm (cryo-TEM). This significant change in size can be explained by the very hydrophilic character of the proteinoid NPs, inducing adsorption of many water molecules on their surface, which are accounted only by the DLS. The ability of biocompatible hydrogel NPs to prevent apoptosis and increase β cell mass might be used for developing novel β cell protective therapies.

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Graphical abstract Effect of covered by bioactive peptide NPs on PDX1 nuclei translocation.

     

Synthesis and Characterization of 2,2-Biimidazole Complexes of Oxocations of Molybdenum (VI,V) and Uranium(VI)

Abstract

2,2′-Biimidazole complexes of MoO₂ ⁺², MoO₂ ⁺ and UO₂ ⁺² have been prepared and characterized by elemental analysis, conductance; and ¹H NMR, IR and electronic spectra. Two types of complexes have been identified. Those obtained from slightly acidic solutions have the formulae MoO₂ (H₂bim)Cl₂.2H₂O 1, UO₂(H₂bim) (Ac)₂ 2 and UO₂(H₂bim)Cl₂.2H₂O 3; whereas those from alkaline solutions have the formulae Mo₂O₄(Hbim)₂.2H₂O 4, and MO₂(Hbim)₂ (M = Mo(VI) 5, U(VI) 6). The infrared spectra of these complexes show characteristic biimidazole frequencies in the 3200–2500, 1550–1000 and 750 cm^?1 regions as well as metal oxygen double bonds in the 900 cm^?1 region. The stoichiometries of the acetate complex has been confirmed from ¹H NMR signal ratios of bimidazole to acetate protons at 7.3 and 2.3 ppm, respectively. The electronic spectrum of molybdenum(V) complex showed d-d transition band at ?13,500 cm^?1 in accord with that reported for copper (d⁹) imidazole complexes; as well as peaks due to charge transfer bands at 30,000–26,000 cm^?1 Peaks assignable to BIM → U(VI) were located at ?26,600 cm^?1. The most probable structures of these complexes have been suggested.     

Fine Structure of Beta Decay Strength Function and Anisotropy of Isovector Nuclear Dencity Component Oscillations in Deformed Nuclei

The experimental measurement data on the fine structure of beta-decay strength function S_β(E) in spherical, transitional, and deformed nuclei are analyzed. Modern high-resolution nuclear spectroscopy methods made it possible to identify the splitting of peaks in S_β(E) for deformed nuclei. By analogy with splitting of the peak of E1 giant dipole resonance (GDR) in deformed nuclei, the peaks in S_β(E) are split into two components from the axial nuclear deformation. In this report, the fine structure of S_β(E) is discussed. Splitting of the peaks connected with the oscillations of neutrons against protons (E1GDR), of proton holes against neutrons (peaks in S_β(E) of β⁺/EC-decay), and of protons against neutron holes (peaks in S_β(E) of β^–-decay) is discussed.     

Mass Spectrometric (FAB) Study of Aspartic Acid Side Reactions in Peptide Synthesis

Abstract

We have been interested in the synthesis of branched peptides, by grafting an amine, eg histamine, to the carboxylic group of aspartic acid side chain of Boc-β Ala-Trp-Met-Asp-Phe-NH₂ also called Pentagastrin (or α-PG). Depending on the coupling conditions used, the main product obtained might be either the wanted derivative or a side-product identified a6 amino-succinyl-pentagastrin (or ASC-PG). Acid or base treatment of this product cleaved the amino-succinyl ring and yielded either α-PG or/and (β-Aspartyl)⁴-PC or β-PG. Amino-succinylation being a general problem in peptide synthesis of aspartyl residue containing peptides, synthesis of α-PG, β-PG, Asc-PG and their corresponding C-terminal dipeptide amides were performed to be analyzed by mass spectroscopy.

FAB mass spectra (PI in glycerol) of the free peptides, as well as of their N-Boc derivatives have been recorded and compared to the mono, di, tri and tetra peptide derivatives. The pseudo-molecular ions of Boc-peptides are usually not observed. However, the intense M+1-Boc (? 100 u) ions are present.

Several sequence ions have been identified and compared to the simulation of their spectra according to six fragmentation routes.

The identification of α, β or succinimide structures from FAB spectra has been proposed.     

Fission barriers and other characteristics of nuclei from the uranium region

Fission barriers in nuclei belonging to the uranium region and their other characteristics are calculated on the basis of the FaNDF⁰ energy density functional. In particular, the neutron-separation energies S _n and S _2n, the proton-separation energies S _p, and the beta-transition energiesQ _β are calculated for uranium, neptunium, and plutonium isotopes. In addition, the deformation energies and parameters of these nuclei are presented along with their radii. A comparison with the predictions of the Skyrme–Hartree–Fock method implemented with several versions of the Skyrme energy density functionals is performed. The role of the octupole deformation β ₃ is studied for the ²³⁸U nucleus. It is shown that this deformation does not have any significant effect on the first-barrier height B ⁽¹⁾ _f or ground-state properties. At the same time, the second-barrier height B(2) f decreases by a factor of about two upon taking into account β ₃. A phase transition at A ~ 260 is found for the three isotopic chains being considered: this point is a bifurcation point at which B ⁽¹⁾ _f (A) forks into two curves. Of these, the curve B ⁽²⁾ _f (A) splits from it, prolonging the former curve for B ⁽¹⁾ _f (A) almost continuously, whereas the curve for B ⁽¹⁾ _f (A) itself goes down sharply.     

Electrical bistability and charge-transport mechanisms in cuprous sulfide nanosphere-poly(<Emphasis Type="Italic">N</Emphasis>-vinylcarbazole) composite films

In this study, electrically bistable devices were fabricated by incorporating cuprous sulfide (Cu₂S) nanospheres with mean size less than 10 nm into a poly(N-vinylcarbazole) (PVK) matrix. A remarkable electrical bistability was clearly observed in the current–voltage curves of the devices due to an electric-field-induced charge transfer between the dodecanethiol-capped Cu₂S nanospheres and PVK. The maximum ON/OFF current ratio reached up to value as large as 10⁴, which was dependent on the mass ratios of Cu₂S nanospheres to PVK, the amplitude of the scanning voltages, and the film thickness. The charge-transport mechanisms of the electrically bistable devices were described on the basis of the experimental results using different theoretical models of organic electronics.