- Factors influencing the activity of nanozymes in the cleavage of an RNA model substrate
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A series of 2-nm gold nanoparticles passivated with different thiols all featuring at least one triazacyclonanone-Zn(II) complex and different flanking units (a second Zn(II) complex, a triethyleneoxymethyl derivative or a guanidinium of arginine of a peptide) were prepared and studied for their efficiency in the cleavage of the RNA-model substrate 2-hydroxypropyl-p-nitrophenyl phosphate. The source of catalysis for each of them was elucidated from the kinetic analysis (Michaelis–Menten profiles, pH dependence and kinetic isotope effect). The data indicated that two different mechanisms were operative: One involving two Zn(II) complexes and the other one involving a single Zn(II) complex and a flanking guanidinium cation. The mechanism based on a dinuclear catalytic site appeared more efficient than the one based on the cooperativity between a metal complex and a guanidinium.
- Czescik, Joanna,Zamolo, Susanna,Darbre, Tamis,Mancin, Fabrizio,Scrimin, Paolo
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supporting information
(2019/08/08)
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- Photochemical heterolysis of 3,5-Bis(dimethylamino)benzyl alcohols and esters: Generation of a benzyl cation with a low-energy triplet state
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An earlier computational study (CASPT2/pVDZ) by Winter et al. predicts the 3,5-bis(dimethylamino)benzyl cation to have nearly degenerate singlet and triplet states. Through product studies it is demonstrated that photolysis of 3,5-bis(dimethylamino)benzyl alcohol and its corresponding acetate and phenylacetate esters in alcoholic solvents produces a solvent incorporated adduct, 3,5-bis(dimethylamino)benzyl ethers, and 3,5-bis(dimethylamino)toluene.
- Perrotta, Raffaele R.,Winter, Arthur H.,Falvey, Daniel E.
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supporting information; experimental part
p. 212 - 215
(2011/03/20)
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- Molecular design and synthesis of artificial ion channels based on cyclic peptides containing unnatural amino acids
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A series of novel cyclic peptides composed of 3 to 5 dipeptide units with alternating natural-unnatural amino acid units, have been designed and synthesized, employing 5-(N-alkanoylamino)-3-aminobenzoic acid with a long alkanoyl chain as the unnatural amino acid. All cyclic peptides with systematically varying pore size, shape, and lipophilicity are found to form ion channels with a conductance of ca. 9 pS in aqueous KCl (500 mM) upon examination by the voltage clamp method. These peptide channels are cation selective with the permeability ratio PCl-/PK+ of around 0.17. The ion channels formed by the neutral, cationic, and anionic cyclic peptides containing L-alanine, L-lysine, and L-aspartate, respectively, show the monovalent cation selectivity with the permeability ratio PNa+/PK+ of ca. 0.39. On the basis of structural information provided by voltage-dependent blockade of the single channel current of all the tested peptides by Ca2+, we inferred that each channel is formed from a dimer of the peptide with its peptide ring constructing the channel entrance and its alkanoyl chains lining across the membrane to build up the channel pore. The experimental results are consistent with an idea that the rate of ion conduction is determined by the nature of the hydrophobic alkanoyl chain region, which is common to all the channels.
- Ishida,Qi,Sokabe,Donowaki,Inoue
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p. 2978 - 2989
(2007/10/03)
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- β-alanine-based dendritic β-peptides: Dendrimers possessing unusually strong binding ability towards protic solvents and their self-assembly into nanoscale aggregates through hydrogen-bond interactions
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A series of poly(β-alanine) dendrimers 1-4 with Boc-carbamate as the surface functionality, β-alanine as the dendritic branch, 3,5-diaminobenzoic acid as the branching agent, and 1,2-diaminoethane as the interior core has been synthesized by a solution-phase peptide-coupling method. The structural identities and purities of the products have been fully characterized by spectroscopic and chromatographic methods. 1H NMR studies on the dendrimers indicated that the Boc-carbamate surface groups exist as a mixture of syn and anti rotamers in solution, and that the dendrimers adopt an open structure in polar solvents; this allows the free interaction of the interior core functionality with solvent molecules. Due to the cooperative effect of a large number of carbamate and amide groups, the dendrimers exhibit an unusually strong binding ability towards protic solvents and behave as H-bond sponges. As a result, the H/D exchange rates of the N - H protons are significantly enhanced in such dendritic structures, as compared to those of nondendritic carbamates and amides. These dendritic peptide dendrimers also exhibit a strong tendency to form nanoscopic aggregates in nonpolar or polar aprotic solvents through intermolecular H-bond interactions.
- Mong, Tony K.-K.,Niu, Aizhen,Chow, Hak-Fun,Wu, Chi,Li, Ang,Chen, Rui
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p. 686 - 699
(2007/10/03)
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