determination-photoisomerization-quantum-yield-hydrazone

Determination of the Photoisomerization Quantum Yield of a Hydrazone Photoswitch

Photoswitching organic molecules that undergo light-driven structural transformations are key components to construct adaptive molecular systems, and they ...

chung-ang university

Chung-Ang University

We present the formation of a nanobelt by self-assembly of β-benzyl GABA (γ-aminobutyric acid). This simple γ-amino acid building block self-assembled to form a well-defined nanobelt in chloroform. The nanobelt showed distinct optical properties due to π-π interactions. This new-generation self-assembled single amino acid may serve as a template for functional nanomaterials.

Spontaneous Nanobelt Formation by Self-Assembly of β-Benzyl GABA.

The properties of eumelanin-like particles (EMPs) and pheomelanin-like particles (PMPs) in regulating the process of amyloid formation of amyloid-beta 42 (Aβ42) were examined. EMPs and PMPs are effective both in interfering with amyloid aggregation of Aβ42 and in remodeling matured Αβ42 fibers. The results suggest that some (but not all) molecular species consisting of melanin-like particles (MPs) are responsible for their inhibiting property toward amyloid formation, and the influence is likely manifested by long-range interactions. Incubating preformed Aβ42 fibers with catechols or MPs leads to the formation of mesh-like, interconnected Aβ42 fibers encapsulated with melanin-like material. MPs are kinetically more effective than catechol monomers in this process, and a detailed investigation reveals that 4,5-dihydroxyindole, a major intermediate in the formation of melanin-like species, and its derivatives are mainly responsible for remodeling amyloid fibers.

Multifaceted Influences of Melanin-Like Particles on Amyloid-beta Aggregation.

Derivatives of 4-aminomethyl-l-phenylalanine with aromatic oligoamide foldamers as sidechain appendages were successfully charged on tRNA by means of flexizymes. Their subsequent incorporation both at the C-terminus of, and within, peptide sequences by the ribosome, was demonstrated. These results expand the registry of chemical structures tolerated by the ribosome to sidechains significantly larger and more structurally defined than previously demonstrated.

Ribosomal Incorporation of Aromatic Oligoamides as Peptide Sidechain Appendages.

The effect of a small ionic surfactant, cetyltrimethylammonium bromide (CTAB), on the self-assembly of a β-peptide has been systematically studied by using scanning electron microscopy, X-ray diffraction, selected area electron diffraction, and molecular dynamics (MD) simulations. The latter study suggested that the formation of asymmetric microcrystals may be due to the preferential adsorption of CTAB on {011} and (001) crystal faces. This work provides a plausible rationale for the characteristic 3D morphogenesis of foldectures and elucidates the interaction between the surfactant and organic building block molecules.

Self-Assembly of a β-Peptide Foldamer: The Role of the Surfactant in Three-Dimensional Shape Selection.

Matrix-assisted laser desorption/ionization (MALDI) has been considered as one of the most powerful analytical tools for mass spectrometry (MS) analysis of large molecular weight compounds such as proteins, nucleic acids, and synthetic polymers thanks to its high sensitivity, high resolution, and compatibility with high-throughput analysis. Despite these advantages, MALDI cannot be applied to MS analysis of small molecular weight compounds (<500 Da) because of the matrix interference in low mass region. Therefore, numerous efforts have been devoted to solving this issue by using metal, semiconductor, and carbon nanomaterials for MALDI time-of-flight MS (MALDI-TOF-MS) analysis instead of organic matrices. Among those nanomaterials, graphene oxide (GO) is of particular interest considering its unique and highly tunable chemical structures composed of the segregated sp carbon domains surrounded by sp carbon matrix. Chemical modification of GO can precisely tune its physicochemical properties, and it can be readily incorporated with other functional nanomaterials. In this review, the advances of GO derivatives and their nanohybrid structures as alternatives to organic matrices are summarized to demonstrate their potential and practical aspect for MALDI-TOF-MS analysis of small molecules.

Graphene Oxide Derivatives and Their Nanohybrid Structures for Laser Desorption/Ionization Time-of-Flight Mass Spectrometry Analysis of Small Molecules.

Fruitful Foldamers: Guest Editors Ivan Huc, Sunbum Kwon, and Hee-Seung Lee discuss the development of the field and introduce this Special Collection on the Synthesis, Properties, and Applications of Foldamers. This collection features top-quality multidisciplinary research and review articles that cover design, self-assembly, guest recognition, catalytic activity, and optical and biological properties of foldamers.

Synthetic Foldamers: Rational Design of Advanced Structures with Diverse Applications.

Metal-coordinated frameworks derived from small peptidic ligands have received much attention thanks to peptides' vast structural and functional diversity. Various peptides with partial conformational preferences have been used to build metal-peptide frameworks, however, the use of conformationally constrained β-peptide foldamers has not been explored yet. Herein we report the first metal-coordination-mediated assembly of β-peptide foldamers with 12-helical folding propensity. The coordination of Ag to the terminal pyridyl moieties afforded a set of metal-peptide frameworks with unique entangled topologies. Interestingly, formation of the network structures was accompanied by notable conformational distortions of the foldamer ligands. As the first demonstration of new metal-peptide frameworks built from modular β-peptide foldamers, we anticipate that this work will be an important benchmark for further structural evolution and mechanistic investigation.

Conformational Adaptation of β-Peptide Foldamers for the Formation of Metal-Peptide Frameworks.

Molecules that undergo light-driven structural transformations constitute the core components in photoswitchable molecular systems and materials. Among various families of photoswitches, photochromic hydrazones have recently emerged as a novel class of photoswitches with superb properties, such as high photochemical conversion, spectral tunability, thermal stability, and fatigue resistance. Hydrazone photoswitches have been adopted in various adaptive materials at different length scales, however, their utilization for modulating biomolecules still has not been explored. Herein we present new hydrazone switches that can photomodulate the structures of short peptides. Systematic investigation on a set of hydrazone derivatives revealed that installation of the amide group does not significantly alter the photoswitching behaviors. Importantly, a hydrazone switch comprising an upper phenyl ring and a lower quinolinyl ring was effective for structural control of peptides. We anticipate that this work, as a new milestone in the research of hydrazone switches, will open a new avenue for structural and functional control of biomolecules.

Hydrazone Photoswitches for Structural Modulation of Short Peptides.

In advanced galvanic replacement, variable factors such as the combination of two elements where actual redox reaction and post-synthetic structural transformation take place. Research on manufacturing distinctive nanostructures has mainly focused on the shape of the sacrificial nanotemplate, the presence or absence of additives, and the reaction temperature. Here, we have attempted to confirm the dependency on the solvent, which was considered to simply serve as a medium for a homogeneous chemical reaction to proceed by aiding the dispersion of the nanotemplate and reactants. Thus, we obtained mushroom-like Au nanoplates (mAuNPs) by comprehensive galvanic replacement reaction between solvents, additives, and adsorbents. The mAuNPs with a porous Au nanoplate head and a hollow nanotube tail structure were formed  an optimization process in a 50 v/v% solvent comprising water and ethylene glycol. As a result of confirming the galvanic replacement in co-solvent conditions, in which various types of water miscible solvents were introduced, it was revealed that the most critical factors for regulating the surface polymeric environment of the nanoplate were the relative polarity index of the co-solvent and the hydrogen bonding type. These depend on the molecular structure of the solvent. The manufactured mAuNPs exhibited excellent absorbance in the near-infrared region, and efficient photothermal (PT) conversion-mediated heat dissipation under local laser irradiation. These results confirm the viability of the gene-thermo dual-modal combinatorial cancer therapy based on the surface loading of oligonucleotides and peptides, and the PT therapeutic approach  and .

Sunbum Kwon

Department of Chemistry

chung-ang university

Determination of the Photoisomerization Quantum Yield of a Hydrazone Photoswitch