Chemoselective ligation techniques: Modern applications of time‐honored chemistry

Abstract

Chemoselective ligation techniques enable the selective modification of proteins and other biomolecules in dilute aqueous solution. Importantly, these reactions occur at or near physiological pH and are compatible with the complex array of functional groups commonly found in biological macromolecules including proteins, nucleotides, and carbohydrates, allowing conjugation reactions to be carried out on unprotected substrates. Recently, a growing number of reactions with established utility in synthetic organic chemistry have been shown to have surprising utility in the context of biological molecules in aqueous media. In this review we highlight several promising reactions that may have widespread applicability in the generation of new materials based on biological macromolecules.

Vinyl Sulfone: A Multi-Purpose Function in Proteomics

“…This classical residue-specific modification chemistry, however, is rarely sufficiently selective to distinguish one residue within a sea of chemical functionality and for this reason more intricate approaches have been developed in recent times to introduce a unique chemical handle in the target protein that is orthogonal to the remainder of the proteome (Hackenberger & Schwarzer, 2008). Direct incorporation of non-canonical amino acids into proteins via the subversion of the biosynthetic machinery is an attractive means of introducing selectively new functionality by either a site-specific or residue-specific manner (Beatty & Tirrell, 2009;de Graaf et al, 2009;Johnson et al, 2010;Liu & Schultz, 2010;Voloshchuk & Montclare, 2010;Young & Schultz, 2010) that in combination with recent and notorious advances in bioorthogonal reactions (nucleophilic addition to carbonyl, 1,3-dipolar cycloaddition reactions, Diels-Alder reactions, olefin cross-metathesis reactions and palladium-catalyzed cross-coupling reactions) has allowed an exquisite level of selectivity in the covalent modification of proteins (Wiltschi & Budisa, 2008;Sletten & Bertozzi, 2009;Lim & Lin, 2010;Tiefenbrunn & Dawson, 2010). In spite that major technical challenges have been overcome, a prodigious amount of lab work and the concurrently optimization of a larger set of parameters is normally required for those advanced and selective methodologies in comparison with conventional organic reaction development.…”

A New Pyridoxal Derivative for Transamination of N‐Terminus of Proteins

“…4-(Dimethoxymethyl)-3-hydroxy-5-(methoxymethyl)-1,2-dimethylpyridinium iodide (7) To a solution of 6 (0.32 g, 1.41 mmol) in 10 mL CH 3 CN, 1 mL CH 3 I was added, and the reaction was stirred at ambient temperature for 5 h. After evaporating the solvent, the resulting product was purified by silica gel column chromatography (DCM∶MeOH＝10∶1, V/V, with 0.2% NEt 3 in MeOH) to give 7 (84 mg, 34.6%) as an orange oil. 1 …”

“…Site-specific protein modifications and the bioconjugates thus formed are useful in the studies of protein expression, improvement of the efficacy of protein drugs, investigations of structure-function relationships, and development of biosensors. 1 To date, a number of powerful strategies have been developed, including genetically encodable, encompassing techniques that are used to produce protein bioconjugates. For example, non-native amino acid incorporation reported by Schultz et al, 2 tetracysteine-based biarsenical labels explored by Tsien and co-workers, 3 and enzyme-based conjugations developed by Ting, Bertozzi and others.…”

Diels–Alder Cycloaddition in Protein Chemistry

“…[16] Its compatibility with biological macromolecules has been explored elegantly in the conjugation of peptides to surfaces for peptide arrays, [17] small molecules [18][19] or peptides [20] to DNA, and carbohydrates to proteins. [21][22] In this Microreview, the most recent examples of the potential application of this cycloaddition on bioconjugation and immobilization of proteins have been reviewed.…”