scholarly journals The Influence of Secondary Structure on Electron Transfer in Peptides

2013 ◽  
Vol 66 (8) ◽  
pp. 848 ◽  
Author(s):  
Jingxian Yu ◽  
John R. Horsley ◽  
Andrew D. Abell
Keyword(s):  
Electron Transfer ◽  
Secondary Structure ◽  
Chain Length ◽  
Intramolecular Hydrogen Bonding ◽  
Electrochemical Analysis ◽  
Helical Conformation ◽  
Intramolecular Electron Transfer ◽  
Helical Structures ◽  
Redox Active ◽  
Intramolecular Hydrogen

A series of synthetic peptides containing 0–5 α-aminoisobutyric acid (Aib) residues and a C-terminal redox-active ferrocene was synthesised and their conformations defined by NMR and circular dichroism. Each peptide was separately attached to an electrode for subsequent electrochemical analysis in order to investigate the effect of peptide chain length (distance dependence) and secondary structure on the mechanism of intramolecular electron transfer. While the shorter peptides (0–2 residues) do not adopt a well defined secondary structure, the longer peptides (3–5 residues) adopt a helical conformation, with associated intramolecular hydrogen bonding. The electrochemical results on these peptides clearly revealed a transition in the mechanism of intramolecular electron transfer on transitioning from the ill-defined shorter peptides to the longer helical peptides. The helical structures undergo electron transfer via a hopping mechanism, while the shorter ill-defined structures proceeded via an electron superexchange mechanism. Computational studies on two β-peptides PCB-(β3Val-β3Ala-β3Leu)n–NHC(CH3)2OOtBu (n = 1 and 2; PCB = p-cyanobenzamide) were consistent with these observations, where the n = 2 peptide adopts a helical conformation and the n = 1 peptide an ill-defined structure. These combined studies suggest that the mechanism of electron transfer is defined by the extent of secondary structure, rather than merely chain length as is commonly accepted.

scholarly journals Insight to Microbial Fe(III) Reduction Mediated by Redox-Active Humic Acids with Varied Redox Potentials

2021 ◽  
Vol 18 (13) ◽  
pp. 6807
Author(s):  
Jingtao Duan ◽  
Zhiyuan Xu ◽  
Zhen Yang ◽  
Jie Jiang
Keyword(s):  
Molecular Weight ◽  
Electron Transfer ◽  
Humic Acids ◽  
Weight Fraction ◽  
Electrochemical Analysis ◽  
Microbial Reduction ◽  
Redox Potentials ◽  
Groundwater Environment ◽  
Redox Active ◽  
Different Molecular Weight

Redox-active humic acids (HA) are ubiquitous in terrestrial and aquatic systems and are involved in numerous electron transfer reactions affecting biogeochemical processes and fates of pollutants in soil environments. Redox-active contaminants are trapped in soil micropores (<2 nm) that have limited access to microbes and HA. Therefore, the contaminants whose molecular structure and properties are not damaged accumulate in the soil micropores and become potential pollution sources. Electron transfer capacities (ETC) of HA reflecting redox activities of low molecular weight fraction (LMWF, <2.5) HA can be detected by an electrochemical method, which is related to redox potentials (Eh) in soil and aquatic environments. Nevertheless, electron accepting capacities (EAC) and electron donating capacities (EDC) of these LMWF HA at different Eh are still unknown. EDC and EAC of different molecular weight HA at different Eh were analyzed using electrochemical methods. EAC of LMWF at −0.59 V was 12 times higher than that at −0.49 V, while EAC increased to 2.6 times when the Eh decreased from −0.59 V to −0.69 V. Afterward, LMWF can act as a shuttle to stimulate microbial Fe(III) reduction processes in microbial reduction experiments. Additionally, EAC by electrochemical analysis at a range of −0.49–−0.59 V was comparable to total calculated ETC of different molecular weight fractions of HA by microbial reduction. Therefore, it is indicated that redox-active functional groups that can be reduced at Eh range of −0.49–−0.59 are available to microbial reduction. This finding contributes to a novel perspective in the protection and remediation of the groundwater environment in the biogeochemistry process.

scholarly journals Helix-sense-selective Polymerization of 3,5-bis(hydroxymethyl)phenylacetylene Rigidly Bearing Galvinoxyl Residues and Their Chiroptical Properties

Polymers ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 1877 ◽  
Author(s):  
Shi ◽  
Wang ◽  
Teraguchi ◽  
Aoki ◽  
Kaneko
Keyword(s):  
Main Chain ◽  
Helical Structure ◽  
Intramolecular Hydrogen Bonding ◽  
Catalyst System ◽  
Static Stability ◽  
Cotton Effect ◽  
Helical Conformation ◽  
Cd Spectra ◽  
Cotton Effects ◽  
Intramolecular Hydrogen

Four kinds of newly synthesized achiral phenylacetylenes bearing a phenylhydrogalvinoxyl residue at 4-position were polymerized by using a chiral rhodium catalyst system, [Rh(nbd)B(C6H5)4] or [Rh(nbd)Cl]2 catalysts in the presence of chiral (R)-(+)- or (S)-(–)-1-phenylethylamine ((R)- or (S)-PEA) cocatalysts. Poly(m-HGDHPA) and poly(m-HGTHPA) in THF showed Cotton signals at the absorption regions of the main chain and hydrogalvinoxyl in the circular dichroism (CD) spectra. It indicated that excess of one-handed helical polyacetylene backbone was induced by helix-sense-selective polymerization (HSSP) under the asymmetric conditions despite the achiral monomer, and the hydrogalvinoxyl moieties were also arranged to form one-handed helical structure. However, there was no Cotton effect for poly(p-HGDHPA) and poly(p-HGTHPA) because the intramolecular hydrogen bonding did not act well to stabilize the helical conformation. The hydrogalvinoxyl units of poly(m-HGDHPA) and poly(m-HGTHPA) were converted to the corresponding galvinoxyl radicals after treatment with PbO2. In the CD spectra of the polyradicals, the Cotton effects decreased depending on their static stability of helical conformation, suggesting that reversal conformation of the polymer chain arose.

Heteroleptic palladium(II) complexes of dipyrrin-1,9-dione supported by intramolecular hydrogen bonding

2020 ◽  
Vol 24 (01n03) ◽  
pp. 112-120 ◽  
Author(s):  
Clayton J. Curtis ◽  
Elisa Tomat
Keyword(s):  
Hydrogen Bonding ◽  
Chemical Characterization ◽  
Intramolecular Hydrogen Bonding ◽  
Palladium Complexes ◽  
Primary Amines ◽  
Redox Active ◽  
Electron Reduction ◽  
Intramolecular Hydrogen ◽  
Planar Geometries

The dipyrrin-1,9-dione framework, which is characteristic of the propentdyopent pigments deriving from heme metabolism, coordinates metal ions as monoanionic bidentate donors. The resulting analogs of dipyrrinato complexes undergo reversible ligand-based reductions, thus showcasing the ability of the dipyrrindione scaffold to act as an electron reservoir. Herein we report the synthesis and characterization of three heteroleptic palladium complexes of the redox-active dipyrrindione ligand. Primary amines were chosen as additional ligands so as to assemble complexes of planar geometries with complementary interligand hydrogen-bonding. Full chemical characterization confirms the hydrogen bonding interactions between the primary amine ligands and the acceptor carbonyl groups on the dipyrrolic ligand. The resulting heteroleptic compounds display reversible one-electron reduction events that are centered on the dipyrrindione ligand as revealed by voltammetry and spectroelectrochemistry data. Within these planar Pd(II) complexes, the propentdyopent motif therefore combines reversible ligand-based redox chemistry with interligand hydrogen bonding in the primary coordination sphere of the metal center.

Actinide Redox-Active Ligand Complexes: Reversible Intramolecular Electron-Transfer in U(dpp-BIAN)2/U(dpp-BIAN)2(THF)

2010 ◽  
Vol 49 (3) ◽  
pp. 924-933 ◽  
Author(s):  
Eric J. Schelter ◽  
Ruilian Wu ◽  
Brian L. Scott ◽  
Joe D. Thompson ◽  
Thibault Cantat ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Intramolecular Electron Transfer ◽  
Redox Active Ligand ◽  
Active Ligand ◽  
Redox Active

Pseudopeptide Foldamers designed for photoinduced intramolecular electron transfer

RSC Advances ◽  
2015 ◽  
Vol 5 (14) ◽  
pp. 10809-10815 ◽  
Author(s):  
Lorenzo Milli ◽  
Enrico Marchi ◽  
Nicola Castellucci ◽  
Maria Teresa Indelli ◽  
Margherita Venturi ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Secondary Structure ◽  
Photoinduced Electron Transfer ◽  
Intramolecular Electron Transfer ◽  
Quenching Efficiency

Hybrid foldamers equipped with a donor and an acceptor unit exhibit unexpected conformations affecting the photoinduced electron transfer ability. The donor quenching efficiency depends both on the nature and on the secondary structure of the linker.

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