Ionic liquids as reaction media for oxidative folding and native chemical ligation of cysteine-containing peptides

Oxidation of Cysteinate Anions Immobilized in the Interlamellar Space of CaAl-Layered Double Hydroxide

L-Cysteinate-intercalated CaAl-layered double hydroxide (LDH) was prepared by the co-precipitation method producing highly crystalline hydrocalumite phase with a well-pillared interlayer gallery. The obtained materials were characterized by X-ray diffractometry, IR as well as Raman spectroscopies. By performing interlamellar oxidation reactions with peracetic acid as oxidant, oxidation of cysteinate to cystinate in aqueous and cysteinate sulfenic acid in acetonic suspensions occurred. The oxidations could be performed under mild conditions, at room temperature, under neutral pH and in air. It has been shown that the transformation pathways are due to the presence of the layered structure, that is, the confined space of the LDH behaved as molecular reactor.

Native Chemical Ligation of Highly Hydrophobic Peptides in Ionic Liquid-Containing Media

The chemical synthesis of a highly hydrophobic membrane-associated peptide by native chemical ligation (NCL) in an ionic liquid (IL) [C₂mim][OAc]/buffer mixture was achieved by employing peptide concentrations up to 11 mM. NCL was studied at different pH and water content and compared to several “gold-standard” ligation protocols. The optimized reaction protocol for the NCL in IL required the addition of 40% water and pH adjustment to 7.0–7.5, resulting in ligation yields of up to 80–95% within 1 to 4 h. This new ligation protocol is generally applicable and outperforms current “gold-standard” NCL methods.

Challenges and Perspectives in Chemical Synthesis of Highly Hydrophobic Peptides

Solid phase peptide synthesis (SPPS) provides the possibility to chemically synthesize peptides and proteins. Applying the method on hydrophilic structures is usually without major drawbacks but faces extreme complications when it comes to "difficult sequences." These includes the vitally important, ubiquitously present and structurally demanding membrane proteins and their functional parts, such as ion channels, G-protein receptors, and other pore-forming structures. Standard synthetic and ligation protocols are not enough for a successful synthesis of these challenging sequences. In this review we highlight, summarize and evaluate the possibilities for synthetic production of "difficult sequences" by SPPS, native chemical ligation (NCL) and follow-up protocols.

Recent advances in green reagents for molecularly imprinted polymers

Molecularly imprinted polymers (MIPs) are tailor-made materials with special binding sites.

Rapana thomasiana hemocyanin modified with ionic liquids with enhanced anti breast cancer activity

This is the first study on the surface modification of a hemocyanin from marine snail Rapana thomasiana (RtH) with series of imidazolium-based amino acid ionic liquids [emim][AA]. We monitored the induced by [emim][AA] conformational changes in RtH molecule and evaluated the effect of these ionic liquids (ILs) on the protein thermal stability. The cytotoxicity of all obtained RtH-[emim][AA] complexes was assessed toward breast cancer cells (MCF-7) and murine fibroblasts (3T3). As a whole, even small amounts of the tested ILs altered the secondary structure of RtH. The thermal denaturation of RtH in presence of [emim][AA] displayed multi-component transitions, which were shifted toward lower temperatures in comparison to those estimated for the native RtH. The profiles of the RtH-IL calorimetric curves show a clear dependence on the structure of the added salts. In addition, all RtH-[emim][AA] complexes exhibited an enhanced antiprofilerative activity of toward MCF-7 cells in comparison to that of the native RtH. The best results are observed for RtH-[emim][Leu], RtH-[emim][Trp] or RtH-[emim][Ile], which applied in concentration of 700 μg/mL inhibited the MCF-7 cell viability (for 24h) by 66, 63 and 53%, respectively. In addition, these IL-RtH complexes were less cytotoxic to 3T3 cells, i.e. they exhibited some cell specificity.

Modification of Rapana thomasiana hemocyanin with choline amino acid salts significantly enhances its antiproliferative activity against MCF-7 human breast cancer cells

This is the first study on the interactions of ionic liquids with large metalloproteins, in particular hemocyanins (Hcs).