molecular assembly
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2022 ◽  
Vol 23 (2) ◽  
pp. 965
Author(s):  
Mina Han ◽  
Ikue Abe ◽  
Jihun Oh ◽  
Jaehoon Jung ◽  
Young Ji Son ◽  
...  

Fluorescent molecular assembly systems provide an exciting platform for creating stimuli-responsive nano- and microstructured materials with optical, electronic, and sensing functions. To understand the relationship between (i) the plausible molecular structures preferentially adopted depending on the solvent polarity (such as N,N-dimethylformamide [DMF], tetrahydrofuran [THF], and toluene), (ii) the resulting spectroscopic features, and (iii) self-assembled nano-, micro-, and macrostructures, we chose a sterically crowded triangular azo dye (3Bu) composed of a polar molecular core and three peripheral biphenyl wings. The chromophore changed the solution color from yellow to pink-red depending on the solvent polarity. In a yellow DMF solution, a considerable amount of the twisted azo form could be kept stable with the help of favorable intermolecular interactions with the solvent molecules. By varying the concentration of the DMF solution, the morphology of self-assembled structures was transformed from nanoparticles to micrometer-sized one-dimensional (1D) structures such as sticks and fibers. In a pink-red toluene solution, the periphery of the central ring became more planar. The resulting significant amount of the keto-hydrazone tautomer grew into micro- and millimeter-sized 1D structures. Interestingly, when THF-H2O (1:1) mixtures were stored at a low temperature, elongated fibers were stacked sideways and eventually developed into anisotropic two-dimensional (2D) sheets. Notably, subsequent exposure of visible-light-irradiated sphere samples to solvent vapor resulted in reversible fluorescence off↔on switching accompanied by morphological restoration. These findings suggest that rational selection of organic dyes, solvents, and light is important for developing reusable fluorescent materials.


Gels ◽  
2022 ◽  
Vol 8 (1) ◽  
pp. 37
Author(s):  
Artur J. Martins ◽  
Fátima Cerqueira ◽  
António A. Vicente ◽  
Rosiane L. Cunha ◽  
Lorenzo M. Pastrana ◽  
...  

Novel fat mimetic materials, such as oleogels, are advancing the personalization of healthier food products and can be developed from low molecular weight compounds such as γ oryzanol and β-sitosterol. Following molecular assembly, the formation of a tubular system ensues, which seems to be influenced by elements such as the oleogelators’ concentration and ratio, cooling rates, and storage periods. Sterol-based oleogels were formulated under distinct environmental conditions, and a comprehensive study aimed to assess the effects of the mentioned factors on oleogel formation and stability, through visual observation and by using techniques such as small-angle X-ray scattering, X-ray diffraction, confocal Raman spectroscopy, rheology, and polarized microscopy. The long, rod-like conformations, identified by small-angle X-ray scattering, showed that different cooling rates influence oleogels’ texture. Raman spectra showed that the stabilization time is associated with the interfibrillar aggregation, which occurred differently for 8 and 10 wt%, with a proven relationship between ferulic acid and the tubular formation. This report gives fundamental insight into the critical point of gelation, referring to the time scale of the molecular stabilization. Our results verify that understanding the structuring mechanisms of oleogelation is decisive for the processing and manufacturing of novel foods which integrate oleogels in their structure.


2021 ◽  
Author(s):  
Jiawei Zhu ◽  
Wenting Ren ◽  
Fei Guo ◽  
Hankun Wang ◽  
Yan Yu

Abstract The mechanical and physical properties of lignocellulosic materials are closely related to the orientation and interaction of the polymers within cell walls. In this work, Imaging Polarized FTIR, combined with directional chemical removal, was applied to characterize the spatial orientation and interaction of cell wall polymers in bamboo fibers and parenchyma cells from two bamboo species. The results demonstrate the cellulose in bamboo fibers is nearly axially oriented whereas it is almost transversely arranged in parenchyma cells. Xylan and lignin are both preferentially oriented alongside cellulose, but with less orientation degre in the parenchyma cells. After lignin removal, the average orientation of xylan and cellulose is little affected, suggesting a strong interaction between cellulose and xylan. Meanwhile, the alkaline treatment significantly weakens the orientation of lignin in both fibers and parenchyma cells, and more significant for the latter, indicating the easy-degradable nature of lignin in parenchyma cells. And, it seemed the lignin and xylan in fibers were more difficult to be removed as compared to parenchyma cells, supporting the assumption that stronger interaction exists between lignin and xylan in the fibers. In a word, it was believed parenchyma cells are more suitable for biorefinery owing to its less ordered and relatively loose molecular assembly, as compared to fibers.


Author(s):  
Yeshua Sempere ◽  
Martin Morgenstern ◽  
Thorsten Bach ◽  
Manuel Plaza

AbstractIn recent years, photochemical reactions have emerged as powerful transformations which significantly expand the repertoire of organic synthesis. However, a certain lack of selectivity can hamper their application and limit their scope. In this context, a major research effort continues to focus on an improved control over stereo- and chemoselectivity that can be achieved in molecular assemblies between photosubstrates and an appropriate host molecule. In this tutorial review, some recent, representative examples of photochemical reactions have been collected whose unique outcome is dictated by the formation of a molecular assembly driven by non-covalent weak interactions. Graphical Abstract


Author(s):  
Samapika Mallik ◽  
K. Swamynathan ◽  
Sandeep Kumar ◽  
Alpana Nayak

Author(s):  
Jia-Rui Wu ◽  
Zhi Cai ◽  
Gengxin Wu ◽  
Dihua Dai ◽  
Yu-Qing Liu ◽  
...  

2021 ◽  
Vol 10 ◽  
Author(s):  
Wei Dai ◽  
Seth A Darst ◽  
Christine M Dunham ◽  
Robert Landick ◽  
Gregory Petsco ◽  
...  

Although much is known about the machinery that executes fundamental processes of gene expression in cells, much also remains to be learned about how that machinery works. A recent paper by O’Reilly et al. reports a major step forward in the direct visualization of central dogma processes at submolecular resolution inside bacterial cells frozen in a native state. The essential methodologies involved are cross-linking mass spectrometry (CLMS) and cryo-electron tomography (cryo-ET). In-cell CLMS provides in vivo protein interaction maps. Cryo-ET allows visualization of macromolecular complexes in their native environment. These methods have been integrated by O’Reilly et al. to describe a dynamic assembly in situ between a transcribing RNA polymerase (RNAP) and a translating ribosome – a complex known as the expressome – in the model bacterium Mycoplasma pneumoniae 1 . With the application of improved data processing and classification capabilities, this approach has allowed unprecedented insights into the architecture of this molecular assembly line, confirming the existence of a physical link between RNAP and the ribosome and identifying the transcription factor NusA as the linking molecule, as well as making it possible to see the structural effects of drugs that inhibit either transcription or translation. The work provides a glimpse into the future of integrative structural cell biology and can serve as a roadmap for the study of other molecular machineries in their native context.


2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Craig P. Yu ◽  
Naoya Kojima ◽  
Shohei Kumagai ◽  
Tadanori Kurosawa ◽  
Hiroyuki Ishii ◽  
...  

AbstractBenzo[de]isoquinolino[1,8-gh]quinolinetetracarboxylic diimide (BQQDI) is an n-type organic semiconductor that has shown unique multi-fold intermolecular hydrogen-bonding interactions, leading to aggregated structures with excellent charge transports and electron mobility properties. However, the strong intermolecular anchoring of BQQDI presents challenges for fine-tuning the molecular assembly and improving the semiconducting properties. Herein, we report the design and synthesis of two BQQDI derivatives with phenyl- and cyclohexyl substituents (Ph–BQQDI and Cy6–BQQDI), where the two organic semiconductors show distinct molecular assemblies and degrees of intermolecular orbital overlaps. In addition, the difference in their packing motifs leads to strikingly different band structures that give rise to contrasting charge-transport capabilities. More specifically, Cy6–BQQDI bearing bulky substituents exhibits isotropic intermolecular orbital overlaps resulting in equal averaged transfer integrals in both π-π stacking directions, even when dynamic disorders are taken into account; whereas Ph–BQQDI exhibits anisotropic averaged transfer integrals in these directions. As a result, Cy6–BQQDI shows excellent device performances in both single-crystalline and polycrystalline thin-film organic field-effect transistors up to 2.3 and 1.0 cm2 V−1 s−1, respectively.


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