Bioinspired superoxide-dismutase mimics: The effects of functionalization with cationic polyarginine peptides

Abstract

Continuing a bio-mimetic approach, we have prepared peptide conjugates of a superoxide dismutase (SOD) mimic [MnL](+) (where HL=N-(2-hydroxybenzyl)-N,N'-bis[2-(N-methylimidazolyl)methyl]ethane-1,2-diamine), namely [MnL'-Arg(n-1)](n+) (where n=2, 4, 7 and 10) and [MnL'-Gly1](+). [MnL'-Arg(n-1)](n+) contained cationic residue(s) that emulate the electrostatic channel of the enzyme. Physicochemical methods showed that functionalization at the secondary amine of HL did not impair coordination to Mn(II) with association constants (Kassoc) between 1.6 and 3.3×10(6)M(-1). The Mn(III)/Mn(II) redox potential of the conjugates was between 0.27 and 0.30V vs SCE, slightly higher than [MnL](+) under the same conditions, but remain at a value that facilitates O2(-) dismutation. The catalytic rate constant (kcat) of the dismutation for the series was studied using a direct stopped-flow method, which showed that for compounds with the same overall charge, the alkylation of the secondary amine of [MnL](+) (kcat=5.0±0.1×10(6)M(-1)s(-1)) led to a lower value (i.e. for [MnL'Gly](+), kcat=4.2±0.1×10(6)M(-1)s(-1)). However, under the same conditions, kcat values between 5.0±0.4×10(6)M(-1)s(-1) and 6.6±0.1×10(6)M(-1)s(-1) were determined for [MnL'-Arg(n-1)](n+) conjugates, indicating that the cationic residue(s) compensated for the loss in activity. Analysis of the effect of ionic strength on the kcat strongly suggested that not all the charges were involved, but only the closest ones electrostatically influenced the SOD active metal centre.

Anti-inflammatory activity of superoxide dismutase mimics functionalized with cell-penetrating peptides

“…Data were best fitted to a 1:1 L/M model. As previously reported, the dissociation constants (K d ) of [Mn-enPI 2 ] + (Mn1), and [Mn-enPI 2 -R9] 10+ (Mn1-R9) found by this method are comparable with values of 6.5 x 10 -7 M and 6.3 x 10 -7 M, respectively, 22 and are similar to that measured for Mn1 by UV-visible spectroscopy (7.7 x 10 -7 M). 36 ), leading to similar free energies of binding for the ligands.…”

“…The peptides were obtained using standard solid phase synthesis, and conjugated to enPI 2 before cleavage from the resin and purification by preparative reversed-phase HPLC ( Figure 1). As previously described, 12,22 the complexation was performed in situ by mixing the ligand and metal ion in a one to one ratio in HEPES buffer (0.1 M, pH 7.4) (see figure S1 for UV-visible titration).…”

“…20 We have functionalized one complex in this series, Mn1 (see Figure 1), 21 with polyarginine peptides and described the effect of positive charges on the catalytic rate constant. 22 Following on, the manganese (II) SOD mimics Mn1 ( Figure 1) was studied in cells and in vivo. 12,23 Its ability to limit ROS flow in cells was demonstrated in activated macrophages.…”

A Cell-Penetrant Manganese Superoxide Dismutase (MnSOD) Mimic Is Able To Complement MnSOD and Exerts an Antiinflammatory Effect on Cellular and Animal Models of Inflammatory Bowel Diseases

“…The diminution of the current intensity of the return peak corresponds to the formation of an hydroxo-Mn complex in solution due to the increase in pH over time. 98 Quantification and identification in cell-lysates Electron paramagnetic resonance (EPR) can be used to quantify Mn 2+ , which shows six-sharp lines in its hexaaqua form. However, in conventional X-band EPR, the EPR spectrum of Mn1 is broad because of the geometry of the Mn II coordination sphere being distorted from the regular octahedron.…”

A Metallo Pro‐Drug to Target CuII in the Context of Alzheimer's Disease

“…Affinity of Mn II for LH has been evaluated by direct titration monitored by UV/Vis ( Figure S5) leading to an apparent affinity constant of 1.3 10 6 m À1 (pH 7.1, 100 mm HEPES) in line with previousm easurement by calorimetry. [17] Affinity of Cu II forL H has been determined by competition with ligands of known affinity (EPR, Figure S6) and an apparent value in the range of 10 16 m À1 was obtained. The affinity of Cu II for Ab at the same pH (i.e.,p H7.1)i s1 0 9 m À1 .…”