Search

Protein misfolding and amyloid formation are implicated in the protein dysfunction, but the underlying mechanism remains to be clarified due to the lack of effective tools for detecting the transient intermediates. Sum frequency generation vibrational spectroscopy (SFG‐VS) has emerged as a powerful tool for identifying the structure and dynamics of proteins at the interfaces. In this review, we summarize recent SFG‐VS studies on the structure and dynamics of membrane‐bound proteins during misfolding processes. This paper first introduces the methods for determining the secondary structure of interfacial proteins: combining chiral and achiral spectra of amide A and amide I bands and combining amide I, amide II, and amide III spectral features. To demonstrate the ability of SFG‐VS in investigating the interfacial protein misfolding and amyloid formation, studies on the interactions between different peptides/proteins (islet amyloid polypeptide, amyloid β, prion protein, fused in sarcoma protein, hen egg‐white lysozyme, fusing fusion peptide, class I hydrophobin SC3 and class II hydrophobin HFBI) and surfaces such as lipid membranes are discussed. These molecular‐level studies revealed that SFG‐VS can provide a unique understanding of the mechanism of interfacial protein misfolding and amyloid formation in real time, in situ and without any exogenous labeling. [ABSTRACT FROM AUTHOR]

The differentiation of enantiomers is of significance in synthetic chemistry and pharmaceutical chemistry. Herein, we report a facile method for chirality sensing of monoalcohols, a challenging target due to the poor reactivity, by combining dynamic covalent chemistry with helical chirality. Four diphenylethene (DPE) derived cyclic hemiaminals were constructed, and the incorporation of a broad range of alcohols and thiols with high efficiency was achieved. The reversibility was further verified by dynamic component exchange. The helical chirality of the DPE motif was induced through chirality transfer by the central chirality of the analytes, resulting in circular dichroism responses. The chirality differentiation of seven chiral secondary alcohols including both alkyl and aryl alcohols was realized, further allowing the quantification of enantiomeric excess with high accuracy. The results described should lay a foundation for future endeavors in chemical sensing, asymmetric synthesis, and chiroptical materials. [ABSTRACT FROM AUTHOR]

Chiral carbon dots (CDs) are a novel luminescent zero‐dimensional carbon‐based nanomaterial with chirality. They not only have the advantages of good biocompatibility, multi‐color‐emission, easy functionalization, but also exhibits highly symmetrical chiral optical characteristics, which broadens their applicability to enantioselectivity of some chiral amino acids like cysteine and lysine, asymmetric catalysis as well as biomedicine in gene expression and antibiosis. In addition, the exploration of the excited state chirality of CDs has developed its excellent circularly polarized luminescence (CPL) properties, opening up a new application scenario like recognition of chiral light sources and anti‐counterfeit printing with information encryption. This review mainly focuses on the mature synthesis approaches of chiral CDs, including chiral ligand method and supramolecular self‐assembly method, then we consider emerging applications of chiral CDs in CPL, biosensing and biological effect. Finally, we concluded with a perspective on the potential challenges and future opportunities of such fascinating chiral CDs. [ABSTRACT FROM AUTHOR]

Spirobifluorenes are an important class of spiro compounds frequently used in the field of organic electronics. However, harnessing spiroconjugation to obtain high‐performance in such structural motifs remains unexplored. We herein propose that peripheral functionalization may serve as a useful tool to control spiroconjugation in an ON/OFF manner on both chemical reactivity and photophysical properties. In particular, the ratio of mono‐ and di‐functionalized spirobifluorenes found experimentally during their synthesis were found to be 3/2, 7/2, and 12/2 for phenyl, nitro‐phenyl and amino‐phenyl analogues, respectively. These remarkable reactivity differences correlate with the spiroconjugation character evaluated theoretically at the CAM‐B3LYP/6‐31G(d,p) level of theory. Additionally, comparison of experimental and predicted optical and chiroptical responses shows that spiroconjugated molecular orbitals have a significant or negligible involvement on the main electronic transitions depending on the peripheral functionality of the spirobifluorene. [ABSTRACT FROM AUTHOR]

"Chirality" governs many fundamental properties in chemistry and biochemistry. While early investigations on stereochemistry are primarily dedicated to static chirality, there is an increasing interest in the field of dynamic chirality (chiral switches). These chiral switches are essential in controlling the directionality in molecular motors. Dynamic chiralities are equally crucial in switchable stereoselectivity, switchable asymmetric catalysis and enantioselective separation. Herein, we limit our discussion to recent advances on stimuli‐induced chiroptical switching of axial, helical, and planar chirality in response to external stimuli. We also discuss a few examples of applications of the switchable chirality. [ABSTRACT FROM AUTHOR]

For the construction of helical foldamers composed of π‐frameworks, the choice of appropriate π‐π stacking units and π‐spacers connecting them is important. The transfer of helicity between the minimal helix structural units is also an essential factor in the construction of homochiral helical foldamers. Tetramers 4 a–4 d, which have four L‐shaped dibenzopyrrolo[1,2‐a]naphthyridine units, were synthesized to investigate the interplay and cooperativity of the helical structures. Tetramer 4 a bridged with a biphenyl unit formed a homochiral bishelical structure with π–π stacking between the L‐shaped units (3.3 Å), consisting only of (P,P)‐ and (M,M)‐enantiomers without the (P,M)‐diastereomer, owing to interplay through the axial chirality of biphenyl unit in the solid state. Similarly, in solution, thermodynamic stabilization of the two helix formations worked cooperatively to favor the bishelical form of 4 a. Furthermore, bishelical foldamer 4 a emitted intense fluorescence (Φ=0.86). [ABSTRACT FROM AUTHOR]