- Of Thiols and Disulfides: Methods for Chemoselective Formation of Asymmetric Disulfides in Synthetic Peptides and Polymers
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In protein or peptide chemistry, thiols are frequently chosen as a chemical entity for chemoselective modification reactions. Although it is a well-established methodology to address cysteines and homocysteines in aqueous media to form S?C bonds, possibilities for the chemoselective formation of asymmetric disulfides have been less approached. Focusing on bioreversibility in conjugation chemistry, the formation of disulfide bonds is highly desirable for the attachment of thiol-containing bioactive agents to proteins or in cross-linking reactions, because disulfide bonds can combine stability in blood with degradability inside cells. In this Concept article, recent approaches in the field of activating groups for thiol moieties incorporated in peptide and polymer materials are highlighted. Advantageous combinations of stability during synthesis of the material with high reactivity towards thiols are explored focusing on simplification and prevention of side reactions as well as additional deprotection and activation steps prior to disulfide formation. Moreover, applications of this chemistry are highlighted and future perspectives are envisioned.
- Sch?fer, Olga,Barz, Matthias
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p. 12131 - 12142
(2018/08/01)
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- Rethinking Cysteine Protective Groups: S-Alkylsulfonyl-l-Cysteines for Chemoselective Disulfide Formation
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The ability to reversibly cross-link proteins and peptides grants the amino acid cysteine its unique role in nature as well as in peptide chemistry. We report a novel class of S-alkylsulfonyl-l-cysteines and N-carboxy anhydrides (NCA) thereof for peptide synthesis. The S-alkylsulfonyl group is stable against amines and thus enables its use under Fmoc chemistry conditions and the controlled polymerization of the corresponding NCAs yielding well-defined homo- as well as block co-polymers. Yet, thiols react immediately with the S-alkylsulfonyl group forming asymmetric disulfides. Therefore, we introduce the first reactive cysteine derivative for efficient and chemoselective disulfide formation in synthetic polypeptides, thus bypassing additional protective group cleavage steps.
- Sch?fer, Olga,Huesmann, David,Muhl, Christian,Barz, Matthias
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supporting information
p. 18085 - 18091
(2016/12/16)
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- Conversion of S-phenylsulfonylcysteine residues to mixed disulfides at pH 4.0: Utility in protein thiol blocking and in protein-S-nitrosothiol detection
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A three step protocol for protein S-nitrosothiol conversion to fluorescent mixed disulfides with purified proteins, referred to as the thiosulfonate switch, is explored which involves: (1) thiol blocking at pH 4.0 using S-phenylsulfonylcysteine (SPSC); (2) trapping of protein S-nitrosothiols as their S-phenylsulfonylcysteines employing sodium benzenesulfinate; and (3) tagging the protein thiosulfonate with a fluorescent rhodamine based probe bearing a reactive thiol (Rhod-SH), which forms a mixed disulfide between the probe and the formerly S-nitrosated cysteine residue. S-Nitrosated bovine serum albumin and the S-nitrosated C-terminally truncated form of AdhR-SH (alcohol dehydrogenase regulator) designated as AdhR-SNO were selectively labelled by the thiosulfonate switch both individually and in protein mixtures containing free thiols. This protocol features the facile reaction of thiols with S-phenylsulfonylcysteines forming mixed disulfides at mild acidic pH (pH = 4.0) in both the initial blocking step as well as in the conversion of protein-S-sulfonylcysteines to form stable fluorescent disulfides. Labelling was monitored by TOF-MS and gel electrophoresis. Proteolysis and peptide analysis of the resulting digest identified the cysteine residues containing mixed disulfides bearing the fluorescent probe, Rhod-SH.
- Reeves,Joshi,Campanello,Hilmer,Chetia,Vance,Reinschmidt,Miller,Giedroc,Dratz,Singel,Grieco
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p. 7942 - 7956
(2015/02/18)
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- Keactions of cysteine sulfenyl thiocyanate with thiols to give unsymmetrical disulfides
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Cysteine sulfenyl thiocyanate (CSSCN) reacts with thiols at pH 0 to cleanly yield disulfides. 2-Mercaptoethanol (2-MESH), 3-mercaptopropionic acid (3-MPASH), penicillamine (PENSH), and glutathione (GSH) react with CSSCN to give the corresponding mixed disulfides: 2-MESSC, 3-MPASSC, PENSSC, and GSSC. These compounds are stable at pH 0 and have been characterized by 1H and 13C NMR spectroscopy.
- Alguindigue Nimmo, Susan L.,Lemma, Kelemu,Ashby, Michael T.
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p. 467 - 471
(2008/02/08)
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