No abstract

The influence of Au nanoparticles (Au NPs) on the aggregation of amyloid-β-(25-35) peptides (Aβ25-35) is investigated by atomic force microscopy and Thioflavin T fluorescence measurements. It is found that, without Au NPs, the Aβ25-35 peptides aggregate gradually from monomers and oligomers to long fibrils with the incubation time. In contrast, short protofibrils are formed quickly after Au NPs are added to the Aβ25-35 solution, which can be further aggregated to form short fibril bundles or even bundle conjunctions. To reveal the origin of Au NPs on the aggregation of Aβ25-35, electrostatic force microscopy and scanning Kelvin microscopy are employed to investigate the electrical properties of the Aβ25-35 fibrils with and without Au NPs. Due to the significant difference of the electrical properties between the Aβ25-35 fibrils and Au NPs, the locations of Au NPs inside the Aβ25-35 fibril bundles can be revealed and hence a possible influence mechanism of Au NPs on the aggregation of Aβ25-35 is suggested.

A facile solution impregnation method to access a novel type of shape-stabilized PCM employing metal–organic frameworks as the matrix.

The aggregation processes of amyloid-β-(16-22) peptides (Aβ16-22) are investigated by atomic force microscopy (AFM). It is found that Aβ16-22 peptides quickly aggregate from monomers to oligomers and flakelike structures and finally to fibrils. In particular, unusual morphology change is observed in an early stage of aggregation; that is, the originally formed flakelike structures would disappear in the following aggregation processes. To determine the evolution of the flakelike structures, in situ AFM imaging is carried out in liquid to reveal the real-time morphology change of Aβ16-22. The results provide clear evidence that the flakelike structures are in an unstable intermediate state, which would be dissolved into oligomers or short protofibrils for reorganization. Further fluorescence and attenuated total reflectance Fourier transform infrared (ATR-FTIR) experiments on thioflavin T(ThT) suggest that those flakelike structures contain β-sheet components.

Thylakoids are complex sub-organellar membrane systems whose role in photosynthesis makes them critical to life. Thylakoids require the coordinated expression of both nuclear- and plastid-encoded proteins to allow rapid response to changing environmental conditions. Transport of cytoplasmically synthesized proteins to thylakoids or the thylakoid lumen is complex; the process involves transport across up to three membrane systems with routing through three aqueous compartments. Protein transport in thylakoids is accomplished by conserved ancestral prokaryotic plasma membrane translocases containing novel adaptations for the sub-organellar location. This review focuses on the evolutionarily conserved chloroplast twin arginine transport (cpTat) pathway. An overview is provided of known aspects of the cpTat components, energy requirements, and mechanisms with a focus on recent discoveries. Some of the most exciting new studies have been in determining the structural architecture of the membrane complex involved in forming the point of passage for the precursor and binding features of the translocase components. The cpTat system is of particular interest because it transports folded protein domains using only the proton motive force for energy. The implications for mechanism of translocation by recent studies focusing on interactions between membrane Tat components and with the translocating precursor will be discussed.