Binbo Jiang

Cross-Seeding Interaction between β-Amyloid and Human Islet Amyloid Polypeptide.

Alzheimers disease (AD) and type 2 diabetes (T2D) are two common protein misfolding diseases. Increasing evidence suggests that these two diseases may be correlated with each other via cross-sequence interactions between β-amyloid peptide (Aβ) associated with AD and human islet amyloid polypeptide (hIAPP) associated with T2D. However, little is known about how these two peptides work and how they interact with each other to induce amyloidogenesis. In this work, we study the effect of cross-sequence interactions between Aβ and hIAPP peptides on hybrid amyloid structures, conformational changes, and aggregation kinetics using combined experimental and simulation approaches. Experimental results confirm that Aβ and hIAPP can interact with each other to aggregate into hybrid amyloid fibrils containing β-sheet-rich structures morphologically similar to pure Aβ and hIAPP. The cross-seeding of Aβ and hIAPP leads to the coexistence of both a retarded process at the initial nucleation stage and an accelerated process at the fibrillization stage, in conjunction with a conformational transition from random structures to α-helix to β-sheet. Further molecular dynamics simulations reveal that Aβ and hIAPP oligomers can efficiently cross-seed each other via the association of two highly similar U-shaped β-sheet structures; thus, conformational compatibility between Aβ and hIAPP aggregates appears to play a key role in determining barriers to cross-seeding. The cross-seeding effects in this work may provide new insights into the molecular mechanisms of interactions between AD and T2D.

Design Energy Efficient Water Utilization Systems Allowing Operation Split

Abstract This article deals with the design of energy efficient water utilization systems allowing operation split. Practical features such as operating flexibility and capital cost have made the number of sub operations an important parameter of the problem. By treating the direct and indirect heat transfers separately, target freshwater and energy consumption as well as the operation split conditions are first obtained. Subsequently, a mixed integer non-linear programming (MINLP) model is established for the design of water network and the heat exchanger network (HEN). The proposed systematic approach is limited to a single contaminant. Example from literature is used to illustrate the applicability of the approach.

Catalytic performance of AuIII supported on SiO2 modified activated carbon

Silica was deposited onto activated carbon through TEOS hydrolysis and this composite was used as a support for the Au catalyst in acetylene hydrochlorination. Silica content and the catalyst synthesis process were both optimized. It was found that 1Au/5SiO2/AC showed improved stability, while being as active as 1Au/AC. Thermogravimetric analysis (TGA) quantitatively revealed the synchronism of TEOS hydrolysis and Au deposition, which was believed to be the linchpin in 1Au/5SiO2/AC synthesis. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) demonstrated that amorphous silica dispersed on the carbon surface uniformly as spherical particles. Silica deposition brought down the surface area of the catalyst while leading to better distribution of gold nanoparticles. Higher gold distribution degree guaranteed the catalytic activity of 1Au/5SiO2/AC despite surface area loss. A higher level of resistance to acetylene, excellent surface property stability and less carbonaceous deposition were determined as the origin of the improved stability of 1Au/5SiO2/AC.

Efficient Au 0/C catalyst synthesized by a new method for acetylene hydrochlorination

A new impregnation method, involving a mixture of solvents and a vacuum drying process, was used to prepare a gold catalyst (MIV-1Au/C1) for acetylene hydrochlorination. It was found that MIV-1Au/C1 was twice as active as the catalyst prepared through the traditional method (PI-1Au/C1). The new method is green, mild and simple. Moreover, it appears to be controllable by tuning solvent and temperature. Excellent Au dispersion in MIV-1Au/C1 was revealed by transmission electron microscopy (TEM). In addition, X-ray photoelectron spectroscopy (XPS) profiles proved that Au0 was the only active species of MIV-1Au/C1 at the initial/highest point of testing. Further XPS results showed that Au0 could be oxidized to Au3+ during the reaction along with the deactivation of MIV-1Au/C1. Thus, Au0 appeared to be preferred for the catalytic route. Our findings demonstrate that this new method has potential as a catalyst for acetylene hydrochlorination. Moreover, this study highlighted the importance of Au0 in this field.

Molecular Understanding of Aβ-hIAPP Cross-Seeding Assemblies on Lipid Membranes

Amyloid-β (Aβ) and human islet polypeptide (hIAPP) are the causative agents responsible for Alzheimers disease (AD) and type II diabetes (T2D), respectively. While numerous studies have reported the cross-seeding behavior of Aβ and hIAPP in solution, little effort has been made to examine the cross-seeding of Aβ and hIAPP in the presence of cell membranes, which is more biologically relevant to the pathological link between AD and T2D. In this work, we computationally study the cross-seeding and adsorption behaviors of Aβ and hIAPP on zwitterionic POPC and anionic 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylglycerol (POPG) mixed bilayers using all-atom molecular dynamics (MD) simulations, particularly aiming to the effects of the initial orientation of the Aβ-hIAPP assembly and the lipid composition of cell membranes on mutual structural and interaction changes in both Aβ-hIAPP assembly and lipid bilayers at the atomic level. Aβ-hIAPP cross-seeding assembly always preferred to adopt a specific orientation and interface to associate with both lipid bilayers strongly via the N-terminal strands of Aβ. Such membrane-bound orientation explains experimental observation that hybrid Aβ-hIAPP fibrils on cell membranes showed similar morphologies to pure hIAPP fibrils. Moreover, Aβ-hIAPP assembly, regardless of its initial orientations, interacted more strongly with POPC/POPG bilayer than POPC bilayer, indicating that electrostatic interactions are the major forces governing peptide-lipid interactions. Strong electrostatic interactions were also attributed to the formation of Ca2+ bridges connecting both negatively charged Glu of Aβ and PO4 head groups of lipids, which facilitate the association of Aβ-hIAPP with the POPC/POPG bilayer. It was also found that the strong peptide-lipid binding reduced lipid fluidity. Both facts imply that Aβ-hIAPP assembly may induce cell damage by altering calcium homeostasis and cell membrane phase. This work provides a better fundamental understanding of cross-seeding of Aβ and hIAPP on cell membranes and a potential pathological link between AD and T2D.

Improvement of performance of a Au–Cu/AC catalyst using thiol for acetylene hydrochlorination reaction

In order to overcome problems of Au–Cu bimetallic catalysts for acetylene hydrochlorination reaction such as instability, Au–Cu–SH/AC catalysts were prepared through the introduction of thiol and tested to examine their activity and stability. It was found that performances of Au–Cu–SH/AC catalysts were quite excellent, with significantly higher catalytic activity and better stability than performances of Au/AC and Au–Cu/AC catalysts. The contents of Cu and thiol additives were also optimized and the optimum molar ratio of Au/Cu/SH was 1 : 1 : 10. Catalyst samples were characterized by scanning electron microscopy (SEM), nitrogen adsorption/desorption (BET), X-ray diffraction (XRD), transmission electronic microscopy (TEM), H2 temperature-programmed reduction (H2-TPR), and X-ray photoelectron spectroscopy (XPS). It was demonstrated that the Au–Cu–SH/AC catalysts were Au0-based catalysts, due to thiol reducing Au3+ to Au0 species during the preparation process. Au0 species exhibited better catalytic activity than Au3+ species for acetylene hydrochlorination, according to the comparison with the composition of active species in different samples through XPS. Furthermore, the sulfhydryl of thiol could bond to the surface of gold nanoparticles (Au NPs). It helped in mitigating the oxidation of Au0 by HCl, protecting Au NPs from structure damage, stabilizing Au NPs in a nearly constant particle size and keeping a more active structure in the reaction environment. Thus, improved dispersity of active species and protection of the active structure of the Au NPs resulted in the better catalytic activity and stability of Au–Cu–SH/AC.

Promotional effect of Ti doping on the ketonization of acetic acid over a CeO2 catalyst

A series of Ce1−xTixO2−δ mixed oxide catalysts were synthesized using a homogeneous precipitation method and characterized, and then these catalysts were applied to convert acetic acid to acetone using a gas-phase ketonization reaction. Ti-doped Ce1−xTixO2−δ catalysts (x = 0.1–0.5) exhibited much better ketonization performance than their parent catalysts of CeO2 and TiO2, and such Ti-doping-induced catalysis improvement is attributed to the formation of a Ce–O–Ti structure depending on the Ti content. Among the different Ce1−xTixO2−δ catalysts, the Ce0.7Ti0.3O2−δ catalyst calcinated at 500 °C showed the best catalysis activity and high stability. A combination of techniques (i.e. TEM, FTIR, H2-TPR, NH3/CO2-TPD and XPS) further revealed that the formation of the Ce–O–Ti structure modified the surface acid–base properties and thus enhanced the redox properties. Moreover, the introduction of Ti into CeO2 also increased the number of oxygen vacancies on the catalysts’ surface that favored the ketonization of acid molecules. This work provides valuable insights into the design of highly efficient CeO2-based catalysts for acid removal in the upgrading process of bio-oil.

Seed-Induced Heterogeneous Cross-Seeding Self-Assembly of Human and Rat Islet Polypeptides

Amyloid peptides can misfold and aggregate into amyloid oligomers and fibrils containing conformationally similar β-sheet structures, which are linked to the pathological hallmark of many neurodegenerative diseases. These β-sheet-rich amyloid aggregates provide common structural motifs to accelerate amyloid formation by acting as seeds. However, little is known about how one amyloid peptide aggregation will affect another one (namely, cross-seeding). In this work, we studied the cross-seeding possibility and efficiency between rat islet amyloid polypeptide (rIAPP) and human islet amyloid polypeptide (hIAPP) solution with preformed aggregates at different aggregation phases, using a combination of different biophysical techniques. hIAPP is a well-known peptide hormone that forms amyloid fibrils and induces cytotoxicity to β-cells in type 2 diabetes, whereas rIAPP is a nonaggregating and nontoxic peptide. Experimental results showed that all different preformed hIAPP aggregates can cross-seed rIAPP to promote the final fibril formation but exhibit different cross-seeding efficiencies. Evidently, hIAPP seeds preformed at a growth phase show the strongest cross-seeding potential to rIAPP, which accelerates the conformational transition from random structures to β-sheet and the aggregation process at the fibrillization stage. Homoseeding of hIAPP is more efficient in initiating and promoting aggregation than cross-seeding of hIAPP and rIAPP. Moreover, the cross-seeding of rIAPP with hIAPP at the lag phase also reduced cell viability, probably because of the formation of more toxic hybrid oligomers at the prolonged lag phase. The cross-seeding effects in this work may add new insights into the mechanistic understanding of the aggregation and coaggregation of amyloid peptides linked to different neurodegenerative diseases.

Exploring the effects of phenolic compounds on bis(imino)pyridine iron-catalyzed ethylene oligomerization

In order to reduce the simultaneous production of insoluble polymers during the bis(imino)pyridine (BIP) iron-catalyzed ethylene oligomerization, a series of phenolic compounds were introduced as modifiers. It was found that the polymer share in the total products would be largely reduced with the increasing dosage of the phenols and the enlargement of para-substituent size from methyl to tert-butyl. Further 1H NMR studies showed that the phenols could provide methylaluminoxane (MAO) profound structural modifications, giving rise to larger MAO aggregates and decoration of phenoxy groups on its surface. This would thus facilitate the active ion pair separation, leading the phenols to become effective polymer-retarding modifiers. Starting from the reaction between 4-tert-butylphenol, AlMe3 and water, a novel phenoxy-aluminoxane could be prepared. Its combination with AlMe3 enabled the catalyst activation, and gave us a further verification about the important role of phenoxy groups on the MAO surface. Furthermore, the introduction of electron-withdrawing groups would improve the reactivity of the –OH group, promoting the interaction between the phenols and MAO. A series of para-halogen substituted phenols were thus developed. With the relatively large size of the bromo group and the highest reactivity of the –OH group, 4-bromophenol was proved to be the most efficient polymer-retarding modifier among the studied phenols in this work. An almost polymer-free ethylene oligomerization could be achieved by this strategy without altering the mono ortho-methyl substituted BIP ligand.

A STUDY OF ULTRASONIC RADIATION DISSIPATION IN POWDER PROCESSING SYSTEM

A model of ultrasonic radiation damping is presented to describe the dissipation of ultrasonic vibration energy in a solid processing system on the basis of vibration damping theory. Four kinds of polyethylene particles, with diameters varying from 0.15 to 0.85 mm and bulk densities varying from 499.6 to 252.5 kg·m−3, are put in a Plexiglas storage bin inserted with a Plexiglas bar, as powder material. Ultrasonic energies absorbed by these kinds of particles were detected by receivers at different levels. The results show that when distance between receiver and source of ultrasonic vibration is lengthened, the AE energy absorption increases, and it also increases when the bulk density of powder material is increased. It is also found that the ultrasonic vibration energy dissipates much more along the inserted bar than along the wall of a storage bin, because the inserted bar has greater radiation area. The results of experiments are accurately predicted by the radiation damping model presented in this article with a fairly good accuracy. Furthermore, a method of level gauging is developed to meet the requirements of different applications, such as online measurement of the particle material, to replace other level gauging methods.