Self‐Assembling Pathway of HiApp Fibrils within Lipid Bilayers

Abstract

The performance of bottom‐contact thin‐film transistor (TFT) structures lags behind that of top‐contact structures owing to the far greater contact resistance. The major sources of the contact resistance in bottom‐contact TFTs are believed to reflect a combination of non‐optimal semiconductor growth morphology on the metallic contact surface and the limited available charge injection area versus top‐contact geometries. As a part of an effort to understand the sources of high charge injection barriers in n‐channel TFTs, the influence of thiol metal contact treatment on the molecular‐level structures of such interfaces is investigated using hexamethyldisilazane (HMDS)‐treated SiO2 gate dielectrics. The focus is on the self‐assembled monolayer (SAM) contact surface treatment methods for bottom‐contact TFTs based on two archetypical n‐type semiconductors, α,ω‐diperfluorohexylquarterthiophene (DFH‐4T) and N,N′bis(n‐octyl)‐dicyanoperylene‐3,4:9,10‐bis(dicarboximide) (PDI‐8CN2). TFT performance can be greatly enhanced, to the level of the top contact device performance in terms of mobility, on/off ratio, and contact resistance. To analyze the molecular‐level film structural changes arising from the contact surface treatment, surface morphologies are characterized by atomic force microscopy (AFM) and scanning tunneling microscopy (STM). The high‐resolution STM images show that the growth orientation of the semiconductor molecules at the gold/SAM/semiconductor interface preserves the molecular long axis orientation along the substrate normal. As a result, the film microstructure is well‐organized for charge transport in the interfacial region.

α-Helical Structures Drive Early Stages of Self-Assembly of Amyloidogenic Amyloid Polypeptide Aggregate Formation in Membranes

“…Aggregate growth occurred through the formation of edge-fused pentameric clusters. This finding is in agreement with AFM experiments (both circular and pentameric aggregates have been observed) that have also indicated the possibility of a similar growth mechanism2845. Growth of hIAPP and rIAPP aggregates is shown in Fig.…”

Resveratrol interferes with the aggregation of membrane-bound human-IAPP: A molecular dynamics study

“…Next, hIAPP binds to negatively charged membranes, in agreement with experimental measurements [27], preferentially through the hydrophilic side chains 21 and 22, while resveratrol in contact with negatively charged membranes irreversibly forms hydrogen bond with the oxygen of the phosphates. A strikingly behavior is found when hIAPP contemporarily interacts with negatively charged lipid membranes and resveratrol.…”

Phosphatidylethanolamine Enhances Amyloid Fiber-Dependent Membrane Fragmentation

“…S6 and S7). 12, 14 In fact, the second phase occurs well after the ThT assay seems to indicate that fiber formation is essentially complete. However, the time difference between the two curves may stem from the differing sensitivities of each method.…”

“…5 Although the molecular mechanisms underlying the cytotoxicity of IAPP have not been fully elucidated, substantial evidence suggests that at least part of the toxicity of aggregates of IAPP and other amyloidogenic proteins is due to the disruption of the plasma and possibly organelle membranes during aggregation. 6–8 The exact mechanism of membrane disruption is not yet fully understood, although several studies have proposed either the formation of transmembrane oligomeric pores, 9–12 non-specific ion permeation caused by binding of oligomers to the membrane surface, 9 or a detergent-like membrane dissolution caused by the growth of amyloid fibrils on the membrane surface. 13–15 …”