Electron Transfer through a Prenucleated Bimetalated Alanine-Based Peptide Helix

Abstract

We have synthesized a 22 residue alanine-based peptide with a tris(bipyridyl)ruthenium(II) amino acid near the middle of the peptide which can act as a photoinducible electron donor. Two histidines spaced i, i + 4 near the C-terminus of the peptide were then cross-linked with a tetraammineruthenium(III) moiety to prenucleate the helix and provide an electron acceptor site. Introduction of the cross-link enhances the average helix content from 67% to 84% at 0 degrees C, as judged by circular dichroism spectroscopy. The temperature dependence of the mean molar residue ellipticity at 222 nm, [THETAV;](222), for the bimetalated peptide was fit to a modified Lifson-Roig helix-coil model to permit extraction of the population of helical conformation at each residue separating the electron donor and acceptor. On average, the residues between the donor and acceptor are 92% helical. Photoinduced electron transfer with a driving force of -1.0 eV and an estimated reorganization energy of 0.82 eV was measured by fluorescence quenching methods in H(2)O and D(2)O, yielding rate constants, k(ET), of 7 +/- 3 x 10(6) s(-)(1) and 5 +/- 1 x 10(6) s(-)(1) at 0 degrees C. Calculation of the electronic coupling matrix element, H(ab), with the Marcus equation yields a value of 0.19 +/- 0.4 cm(-)(1). Analysis in terms of the pathway model for electronic coupling indicates that this magnitude of H(ab) is consistent with the participation of hydrogen bonds in electronic coupling for an isolated alpha-helix.

Metal‐Mediated Functionalization of Natural Peptides and Proteins: Panning for Bioconjugation Gold

“…Reviews not dwell on metalation approaches that use traditional organic bioconjugation reagents covalently tethered to as table metal complex, even though these methods have asignificant and important history. [142][143][144][145][146][147] Additional complementary metalation approaches include unnatural amino acid incorporation [143,[148][149][150][151][152] of am etal-binding residue (e.g.c yclopentadiene [148][149][150] or imidazolium, [152,153] )a nd de novo design of metal-binding proteins.S ince most designed metalloproteins bind free metal salts,n ot functionalized complexes,w e limit coverage to methods that do permit functionalization with useful reagents or molecules.S imilarly,m etal affinity tagging technologies such as nickel/His-tag [154][155][156] or zinc/ tetraaspartate [157][158][159] pairs,although useful for purification and detection applications,a re predominantly outside our scope.…”

Metallvermittelte Funktionalisierung natürlicher Peptide und Proteine: Biokonjugation mit Übergangsmetallen

“…Mechanistische Vorschläge für diesen Prozess gibt es bereits,d och fehlt es zumeist an konkreten Belegen. [142][143][144][145][146][147] Weitere komplementäre Metallierungsansätze basieren auf der Inkorporierung [143,[148][149][150][151][152] einer nichtnatürlichen Aminosäure mit metallbindender Seitenkette (z. Obwohl sie auf eine einzige Gruppe an Funktionalisierungen beschränkt ist, hat sich die Azidgruppe zu einem essenziellen Bestandteil der gängigen Biokonjugationsmethoden entwickelt und die oben beschriebene Te chnik wurde bereits von verschiedenen Arbeitsgruppen ausführlich angewendet.…”

“…[138] Kürzlich wurde außerdem eine reaktionszentrenselektive Version der Azidtransferreaktion an Avidinderivaten durch die Inkorporation eines Biotinzentrums in den Imidazolring erreicht. [141] [142][143][144][145][146][147] Weitere komplementäre Metallierungsansätze basieren auf der Inkorporierung [143,[148][149][150][151][152] einer nichtnatürlichen Aminosäure mit metallbindender Seitenkette (z. B. Cyclopentadien [148][149][150] oder Imidazolium [152,153] )o der auf dem neuartigen Design metallbindender Proteine.D ad ie meisten eigens konzipierten Metalloproteine freie Metallsalze anstelle funktionalisierter Komplexe binden, beschränken wir den Umfang dieses Aufsatzes auf solche Methoden, die die Funktionalisierung mit einem nützlichen Reagenz oder Molekülerlauben.…”

Bioinspired approach toward molecular electrets: synthetic proteome for materials

“…When the structures with opposing dipole direction are not completely symmetrical, the differences in the electronic coupling can prevail over the dipole-induced effect for relatively large −ΔG CT (0) [125]. Since the beginning of the 21 st century, studies of dipole effects on CT have focused on systems comprising polypeptide helices [12,95,99,[126][127][128][129][130][131][132][133][134][135][136][137][138][139][140][141]. Donor-bridge-acceptor (DBA) constructs, where the bridge is a helix, allow for testing dipole-induced charge-transfer rectification, i.e.…”