Fine Tuning of Emission Behavior, Self-Assembly, Anion Sensing, and Mitochondria Targeting of Pyridinium-Functionalized Tetraphenylethene by Alkyl Chain Engineering

In this work we present a clean one-step process for modifying headgroups of self-assembled monolayers (SAMs) on gold using photo-enabled click chemistry. A thiolated, cyclopropenone-caged strained alkyne precursor was first functionalized onto a flat gold substrate through self-assembly. Exposure of the cyclopropenone SAM to UV-A light initiated the efficient photochemical decarbonylation of the cyclopropenone moiety, revealing the strained alkyne capable of undergoing the interfacial strain-promoted alkyne-azide cycloaddition (SPAAC). Irradiated SAMs were derivatized with a series of model azides with varied hydrophobicity to demonstrate the generality of this chemical system for the modification and fine-tuning of the surface chemistry on gold substrates. SAMs were characterized at each step with polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS) to confirm successful functionalization and reactivity. Furthermore, to showcase the compatibility of this approach with biochemical applications, cyclopropenone SAMs were irradiated and modified with azide-bearing cell adhesion peptides to promote human fibroblast cell adhesion, then imaged by live cell fluorescence microscopy. Thus, the “photoclick” methodology reported here represents an improved, versatile, catalyst-free protocol that allows for a high degree of control over the modification of material surfaces, with applicability in materials science as well as biochemistry.<br>

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Kinetic Constraints in the Specific Interaction between Phosphorylated Ubiquitin and Proteasomal Shuttle Factors

Biomolecules ◽

10.3390/biom11071008 ◽

2021 ◽

Vol 11 (7) ◽

pp. 1008

Author(s):

Ling-Yun Qin ◽

Zhou Gong ◽

Kan Liu ◽

Xu Dong ◽

Chun Tang

Keyword(s):

Exchange Rate ◽

Self Assembly ◽

Solution Structure ◽

Specific Interaction ◽

Dissociation Rate ◽

Fine Tuning ◽

Binding Mechanism ◽

Kinetics Analysis ◽

Kinetic Constraint ◽

Thermodynamic Basis

Ubiquitin (Ub) specifically interacts with the Ub-associating domain (UBA) in a proteasomal shuttle factor, while the latter is involved in either proteasomal targeting or self-assembly coacervation. PINK1 phosphorylates Ub at S65 and makes Ub alternate between C-terminally relaxed (pUbRL) and retracted conformations (pUbRT). Using NMR spectroscopy, we show that pUbRL but not pUbRT preferentially interacts with the UBA from two proteasomal shuttle factors Ubqln2 and Rad23A. Yet discriminatorily, Ubqln2-UBA binds to pUb more tightly than Rad23A does and selectively enriches pUbRL upon complex formation. Further, we determine the solution structure of the complex between Ubqln2-UBA and pUbRL and uncover the thermodynamic basis for the stronger interaction. NMR kinetics analysis at different timescales further suggests an indued-fit binding mechanism for pUb-UBA interaction. Notably, at a relatively low saturation level, the dissociation rate of the UBA-pUbRL complex is comparable with the exchange rate between pUbRL and pUbRT. Thus, a kinetic constraint would dictate the interaction between Ub and UBA, thus fine-tuning the functional state of the proteasomal shuttle factors.

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Supramolecular Nanofibers from Collagen-Mimetic Peptides Bearing Various Aromatic Groups at N-Termini via Hierarchical Self-Assembly

International Journal of Molecular Sciences ◽

10.3390/ijms22094533 ◽

2021 ◽

Vol 22 (9) ◽

pp. 4533

Author(s):

Tomoyuki Koga ◽

Shinya Kingetsu ◽

Nobuyuki Higashi

Keyword(s):

Self Assembly ◽

Triple Helix ◽

Wavelength Conversion ◽

Nile Red ◽

Tem Analysis ◽

Mimetic Peptides ◽

Collagen Mimetic Peptides ◽

Potential Applications ◽

Hydrophobic Molecule ◽

Emission Behavior

Self-assembly of artificial peptides has been widely studied for constructing nanostructured materials, with numerous potential applications in the nanobiotechnology field. Herein, we report the synthesis and hierarchical self-assembly of collagen-mimetic peptides (CMPs) bearing various aromatic groups at the N-termini, including 2-naphthyl, 1-naphtyl, anthracenyl, and pyrenyl groups, into nanofibers. The CMPs (R-(GPO)n: n > 4) formed a triple helix structure in water at 4 °C, as confirmed via CD analyses, and their conformations were more stable with increasing hydrophobicity of the terminal aromatic group and peptide chain length. The resulting pre-organized triple helical CMPs showed diverse self-assembly into highly ordered nanofibers, reflecting their slight differences in hydrophobic/hydrophilic balance and configuration of aromatic templates. TEM analysis demonstrated that 2Np-CMPn (n = 6 and 7) and Py-CMP6 provided well-developed natural collagen-like nanofibers and An-CMPn (n = 5–7) self-assembled into rod-like micelle fibers. On the other hand, 2Np-CMP5 and 1Np-CMP6 were unable to form nanofibers under the same conditions. Furthermore, the Py-CMP6 nanofiber was found to encapsulate a guest hydrophobic molecule, Nile red, and exhibited unique emission behavior based on the specific nanostructure. In addition to the ability of CMPs to bind small molecules, their controlled self-assembly enables their versatile utilization in drug delivery and wavelength-conversion nanomaterials.

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Aggregation Behaviours of Surface-Active Ionic Liquids 1-Alkyl-3-methylimidazolium Bis(2-ethylhexyl)sulfosuccinate

Australian Journal of Chemistry ◽

10.1071/ch16122 ◽

2016 ◽

Vol 69 (11) ◽

pp. 1254 ◽

Cited By ~ 5

Author(s):

Jiequn Wu ◽

Tianxiang Yin ◽

Shaoxiong Shi ◽

Weiguo Shen

Keyword(s):

Ionic Liquids ◽

Self Assembly ◽

Alkyl Chain ◽

Systematic Investigation ◽

Bulk Solution ◽

Free Energies ◽

Imidazolium Cation ◽

Structure Transition ◽

Surface Active ◽

Counter Ion Binding

The systematic investigation of the aggregation behaviours of newly synthesised surface-active ionic liquids 1-alkyl-3-methylimidazolium bis(2-ethylhexyl)sulfosuccinate ([Cnmim][AOT], n = 2, 3, 5, 6, 7) by various techniques is reported. The critical aggregation concentrations (CACs) and the standard Gibbs free energies of aggregation () were determined from measurements on conductivity, fluorescence, and surface tension, which suggested a stronger self-assembly ability in the bulk solution for [Cnmim][AOT] surfactants with longer alkyl chain cations. An interesting structure transition driven by the penetration of the imidazolium cation into the aggregate when n > 4 was found by analysis of the variations of the values of CAC, , the degree of counter ion binding (β), and the micropolarity (I1/I3) immediately after the CAC with changing alkyl chain length of the imidazolium cation, which was further confirmed by 1H NMR measurements.

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Effects of Alkyl Chain Length and Hydrogen Bonds on the Cooperative Self-Assembly of 2-Thienyl-Type Diarylethenes at a Liquid/Highly Oriented Pyrolytic Graphite (HOPG) Interface

Chemistry - A European Journal ◽

10.1002/chem.201500707 ◽

2015 ◽

Vol 21 (39) ◽

pp. 13569-13576 ◽

Cited By ~ 20

Author(s):

Soichi Yokoyama ◽

Takashi Hirose ◽

Kenji Matsuda

Keyword(s):

Hydrogen Bonds ◽

Chain Length ◽

Self Assembly ◽

Alkyl Chain ◽

Pyrolytic Graphite ◽

Alkyl Chain Length ◽

Highly Oriented Pyrolytic Graphite

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Hydroxylated phosphines as ligands for chalcogenide clusters: self assembly, transformations and stabilization

Pure and Applied Chemistry ◽

10.1515/pac-2017-0105 ◽

2017 ◽

Vol 89 (3) ◽

pp. 379-392 ◽

Cited By ~ 2

Author(s):

Maxim N. Sokolov ◽

Alexander V. Anyushin ◽

Rita Hernandez-Molina ◽

Rosa Llusar ◽

Manuel G. Basallote

Keyword(s):

Transition Metal ◽

Metal Complexes ◽

Transition Metal Complexes ◽

Self Assembly ◽

Structure Elucidation ◽

Alkyl Chain ◽

Chalcogenide Clusters ◽

Recent Advances

AbstractThis contribution is a documentation of recent advances in the chemistry of chalcogenide polynuclear transition metal complexes coordinated with mono- and di-phosphines functionalized with hydroxo groups. A survey of complexes containing tris(hydroxymethyl)phosphine (THP) is presented. The influence of the alkyl chain in bidentate phosphines, bearing the P–(CH2)x–OH arms, is also analyzed. Finally, isolation and structure elucidation of the complexes with HP(OH)2, P(OH)3, As(OH)3, PhP(OH)2, stabilized by coordination to Ni(0) and Pd(0) centers embedded into chalcogenide clusters, is discussed.

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