For the first time, natural Aβ fibrils (WT) implicated in Alzheimer's disease, as well as two synthetic mutants forming less toxic amyloid fibrils (L34T) and highly toxic oligomers (oG37C), are chemically characterized at the scale of a single structure using tip-enhanced Raman spectroscopy (TERS). While the proportion of TERS features associated with amino acid residues is similar for the three peptides, a careful examination of amide I and amide III bands allows us to clearly distinguish WT and L34T fibers organized in parallel β-sheets from the small and more toxic oG37C oligomers organized in anti-parallel β-sheets.

Click chemistry is widely used in materials and surface science for its high efficiency, ease of use and high yields. Azide-terminated SAMs have been prepared successfully by using three different deposition methods (postfunctionalization and direct grafting by immersion as well as spin coating). Strikingly, our study shows that the reactivity of the azido group on the surface with the alkyne in solution is not trivial and seems to be closely related to the orientation of the azide. Indeed, more the azide is vertically oriented more it is accessible and reactive. The orientation of azido dipoles at the surface depends strongly on the method used to prepare the monolayer. The post-functionalization method allows to have a homogeneous population of the azide groups on the surface with a better vertical orientation than that obtained using direct grafting by immersion or spin coating processes. Whatever the type of azide-terminated SAMs, the reactivity of the accessible vertical azido groups is complete. This study clearly demonstrates that it is possible to control the amount of reactive azides and, consequently, the amount of molecules immobilized on the surface after the click reaction by choosing the deposition method.

The morphology and secondary structure of peptide fibers formed by aggregation of tubulin-associated unit (Tau) fragments (K18), in the presence of the inner cytoplasmic membrane phosphatidylinositol component (PIP 2 )orheparin sodium (HS) as cofactors,a re determined with nanoscale (< 10 nm) spatial resolution. By means of tip-enhanced Raman spectroscopy( TERS), the inclusion of PIP 2 lipids in fibers is determined based on the observation of specific C=Oe ster vibration modes.Moreover,analysis of amide Iand amide III bands suggests that the parallel b-sheet secondary structure content is lower and the random coil content is higher for fibers grown from the PIP 2 cofactor instead of HS.T hese observations highlight the occurrence of some local structural differences between these fibers.T his study constitutes the first nanoscale structural characterization of Tau/phospholipid aggregates,w hich are implicated in deleterious mechanisms on neural membranes in Alzheimersd isease.

Here we exercise nanoscale control over the assembly of highly anisotropic silica helices using convective flow by using the physical properties occurring during evaporation-induced self-assembly. Organizing and patterning such chiral elongated objects over large surfaces in a controllable and reproducible fashion is challenging, but desirable to optimize the performance of biomimetic structures, nano-sensors (mechanical properties of helices) or optical materials (chiral objects have asymmetric interactions with light as absorption is different for left-and right-handed polarization). The coupling of evaporation forces and physicochemical solution properties induce specific helix alignment and the stick-slip phenomenon produces a periodical deposition of bands with controllable and regular spacing. Helix orientation, packing density and spacing can then be tuned. We observe the effect of polymer additives, silica helix concentration, and substrate withdrawal speed on the quality and the orientation of the helix deposition. Theoretical modeling based on capillary hydrodynamics is developed to describe the relationship between evaporative conditions and pitch distance, the band width of the stick region and the helix orientation.

We have developed a convenient and versatile synthetic methodology to prepare various azidoorganotrialkoxysilanes using the platinum‐catalyzed hydrosilylation of stable olefinic precursors with an azide function as the last step. Hydrosilylation of alkene‐functionalized aliphatic and aromatic azides featuring alkyl, urea, carbamate and pegylated moieties has been successfully achieved while preserving the integrity of the azide function. The spin coating technique has been used successfully to prepare one azide‐terminated monolayer in ambient atmosphere onto an oxide surface. This process has the advantages of being fast, simple, easy to handle and needs less solvent. The ability of the azide‐terminated surface to immobilize molecules via the copper‐catalyzed alkyne‐azide cycloaddition reaction has been demonstrated by Modulation Infrared Reflection‐Adsorption Spectroscopy using a probe molecule bearing a NO2 group.

Fort he first time,n atural Ab 1-42 fibrils (WT) implicated in Alzheimersd isease,a sw ell as two synthetic mutants forming less toxic amyloid fibrils (L34T) and highly toxico ligomers (oG37C), are chemically characterized at the scale of asingle structure using tip-enhanced Raman spectroscopy( TERS). While the proportion of TERS features associated with amino acid residues is similar for the three peptides, acareful examination of amide Iand amide III bands allows us to clearly distinguish WT and L34T fibers organized in parallel b-sheets from the small and more toxic oG37C oligomers organized in anti-parallel b-sheets.

Functionalization of silica surfaces with silane-based self-assembled monolayers (SAMs) is widely used in material sciences to tune surface properties and introduce terminal functional groups enabling subsequent chemical surface reactions and immobilization of (bio)­molecules. Here, we report on the synthesis of four organotrimethoxysilanes with various molecular structures and we compare their grafting by spin coating with the one performed by the conventional solution immersion method. Strikingly, this study clearly demonstrates that the spin coating technique is a versatile, fast, and more convenient alternative process to prepare robust, smooth, and homogeneous SAMs with similar properties and quality as those deposited via immersion. SAMs were characterized by PM-IRRAS, AFM, and wettability measurements. SAMs can undergo several chemical surface modifications, and the reactivity of amine-terminated SAM was confirmed by PM-IRRAS and fluorescence measurements.

Amino-terminated Self-Assembled Monolayers (SAMs) are widely used to functionalize silica surfaces as a primary layer in the field of biosensors. The use of commercial aminosilanes suffers from a lack of...