Amphiphile supramolecular assemblies result from the cooperative effects of multiple weak interactions between a large number of subcomponents. As a result, prediction of and control over the morphologies of such assemblies remains difficult to achieve. Here, we described the fine-tuning of the shape, size, and morphology transitions of twisted and helical membranes formed by non-chiral dicationic n-2-n gemini amphiphiles complexed with chiral tartrate anions. We have reported that such systems express the chirality of the tartrate components at a supramolecular level and that the mechanism of the chiral induction by counterions involves specific anion cation recognition and the induction of conformationally labile chirality in the cations. Here, we demonstrate that the morphologies and dimensions of twisted and helical ribbons, as well as tubules, can be controlled and that interconversion between these structures can be induced upon modifying temperature, upon introducing small amounts of additives, or slightly modifying molecular structure. Specifically, electron microscopy, IR spectroscopy, and small-angle X-ray scattering show that (i) varying the hydrophobic chain length or adding gemini having bromide counterions (1%) or the opposite enantiomer (10%) leads to an increase of the diameter of membrane tubules from 33 to 48.5 nm; (ii) further addition (1.5%) of gemini bromide or a slight increase in temperature induces a transition from tubules to twisted ribbons; (iii) the twist pitch of the ribbons can be continuously tuned by varying enantiomeric excess; and (iv) it was also observed that the morphologies of these ribbons much evolve with time. Such unprecedented observations over easy tuning of the chiral supramolecular structures are clearly related to the original feature that the induction of chirality is solely due the counterions, which are much more mobile than the amphiphiles.

Diverse chiral nanometric ribbons and tubules formed by self-assembly of organic amphiphilic molecules could be transcribed to inorganic nanostructures using a novel sol−gel transcription protocol with tetraethoxysilane (TEOS) in the absence of catalyst or cosolvent. By controlling parameters such as temperature or the concentration of the different reactants, we could finely tune the morphology of the inorganic nanostructures formed from organic templates. This fine-tuning has also been achieved upon controlling the kinetics of both organic assembly formation and inorganic polycondensation. The results presented herein show that the dynamic and versatile nature of the organic gels considerably enhances the tunability of inorganic materials with rich polymorphisms.

The quantification of collagen fibril size is a major issue for the investigation of pathological disorders associated with structural defects of the extracellular matrix. Second-harmonic generation microscopy is a powerful technique to characterize the macromolecular organization of collagen in unstained biological tissues. Nevertheless, due to the complex coherent building of this nonlinear optical signal, it has never been used to measure fibril diameter so far. Here we report absolute measurements of second-harmonic signals from isolated fibrils down to 30 nm diameter, via implementation of correlative second-harmonicelectron microscopy. Moreover, using analytical and numerical calculations, we demonstrate that the high sensitivity of this technique originates from the parallel alignment of collagen triple helices within fibrils and the subsequent constructive interferences of second-harmonic radiations. Finally, we use these absolute measurements as a calibration for ex vivo quantification of fibril diameter in the Descemet's membrane of a diabetic rat cornea.

Abstract. This paper presents a generalization of the Roddier & Roddier Phase Mask coronagraph for polychromatic observations. It is shown that using a dual-zone phase mask, combined with complex apodization, both phase and size chromatism can be compensated simultaneously to produce high extinction of a point source over large bandwidths, for example the entire K band with a residual integrated starlight of 3.2 × 10 −4 and a star intensity level of 10 −6 at an angular separation of 3λ/D. Other advantages of the proposed technique include the compatibility with centrally obscured telescopes, absence of blind axes and no symmetrization of the images.

Molecular inclusion phenomena have been widely studied because of their applications in many disciplines, as exemplified by catalysis, [1] separation, [2] sensors, [3] pharmaceutics, [4] and electronics. [5] In line with the lock-and-key metaphor, [6] molecular recognition of guest molecules has been studied on the basis of preformed host compounds. [7,8] In contrast, the surprising ability of the immune system to produce antibodies in response to antigens inspired chemists to develop guestinduced assembly of receptors from multiple fragments. [9,10] In spite of the potential advantage of this molding approach, there remain limitations in the design of molecular fragments that constitute libraries, in the intermolecular interactions to connect them, and in the type and size of template molecules.A simpler approach is to employ adaptive self-assembly of subunits that are capable of forming molecular networks by flexibly following the shape of guest molecules. One of the adaptive molecular assemblies ubiquitous in nature is hydration shells, whereby amorphous hydrogen-bonding networks of water are formed around dissolved molecules by flexibly covering their surfaces. By replacing these hydrogen-bonded water shells with molecular networks, adaptive supramolecular shells could be obtained. We recently reported that coordination nanoparticles (CNPs) were spontaneously formed in water from a wide variety of nucleotides and lanthanide ions.[11] Nucleotides are key molecules of life that play central roles in metabolism and show rich structural diversity. They are composed of nucleobases, ribose or 2'-deoxyribose linkers, and phosphate groups, whose structures are regarded as bidentate ligands. Lanthanide ions meanwhile exhibit large coordination numbers and high coordination flexibility. The combination of these components is suitable for making amorphous coordination networks that are selfassembled to accommodate the size and shape of guest materials. Interestingly, a variety of water-soluble functional materials such as fluorescent dyes, inorganic nanocrystals, and biopolymers are readily co-assembled in these coordination networks, revealing the feature of adaptive self-assembly. [11b] Despite these interesting phenomena, however, very little is known about the basic properties of coordination networks, including their effect on the properties of confined guest molecules. As the networks are formed from nucleotides and lanthanide ions in aqueous media, it is expected to influence the degree of hydration, thermal mobility, and conformational freedom of water-soluble guest molecules. Herein, we describe unique interfacial properties of polymeric coordination shells self-assembled from nucleotides and lanthanide ions. These chiral coordination networks were found to exert conformational restraints on guest molecules and display surprising barrier properties against molecular oxygen (Figure 1).The encapsulation of guest molecules in nucleotidelanthanide nanoparticles was performed by mixing aqueous lanthanide chloride...

Bio-hybrid networks are designed based on the self-assembly of surface-engineered collagen-silica nanoparticles. Collagen triple helices can be confined on the surface of sulfonate-modified silica particles in a controlled manner. This gives rise to hybrid building blocks with well-defined diameters and surface potentials. Taking advantage of the self-assembling properties of collagen, collagen-silica networks are further built-up in solution. The structural and specific recognition properties of the collagen fibrils are well-preserved within the hybrid assembly. A combination of calorimetry, dynamic light scattering, zetametry and microscopy studies indicates that network formation occurs via a surface-mediated mechanism where pre-organization of the protein chains on the particle surface favors the fibrillogenesis process. These results enlighten the importance of the nano-bio interface on the formation and properties of self-assembled bionanocomposites.

Second-harmonic generation (SHG) microscopy is currently the preferred technique for visualizing collagen in intact tissues, but the usual implementations struggle to reveal collagen fibrils oriented out of the imaging plane. Recently, an advanced SHG modality, circular dichroism SHG (CD-SHG), has been proposed to specifically highlight out-of-plane fibrils. In this study, we present a theoretical analysis of CD-SHG signals that goes beyond the electric dipolar approximation to account for collagen chirality. We demonstrate that magnetic dipolar contributions are necessary to analyze CD-SHG images of human cornea sections and other collagen-rich samples. We show that the sign of CD-SHG signals does not reveal whether collagen fibrils point upwards or downwards as tentatively proposed previously. CD-SHG instead probes the polarity distribution of out-of-plane fibril assemblies at submicrometer scale, namely homogeneous polarity versus a mix of antiparallel fibrils. This makes CD-SHG a powerful tool for characterizing collagen organization in tissues, specifically the degree of disorder, which is affected during pathological remodeling. CD-SHG may thus serve to discriminate healthy and diseased collagen-rich tissues.

Bionanocomposites based on the association between biological polymers and inorganic colloids are an emerging class of materials, with main applications in biotechnology and biomedicine. They combine the chemical diversity, hierarchical structure, and biocompatibility of natural biomacromolecules with the robustness and functionality of mineral phases. In particular, biopolymer hydrogels can act as templates and/or host matrices for nanoparticles to design bionanocomposites with tailored optical, conductive, magnetic, mechanical, and bioactive properties. This review presents the key concepts on which such materials are currently designed, in terms of chemistry and physics. Specific examples are provided to illustrate the importance of the bio‐organic/inorganic interface on the final properties of the composite structures. It is finally suggested that bionanocomposites have a major role to play for the development of green materials and bio‐responsive devices. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012