Catalysis of chemical reactions is crucial for both chemical industry and research. However, scientists are not the first ones to use catalysts in their laboratory. In fact, they are also essential for nature which designs plenty of biocatalysts, playing a pivotal role in living systems. For a long time, it was thought that only enzymes had this property. However, since the beginning of the 1980s, it is known that ribonucleic acids (also termed RNA) can acquire this ability, making them compulsory for key reactions (e.g., for the translation of messenger RNA in the ribosome). Based on that, chemists designed several synthetic DNA catalysts (termed DNAzymes) for a large variety of reactions and applications. Among the DNA structures used, G-quadruplexes are guanine-rich noncanonical DNA structures (i.e., differing from duplex DNA) composed of native G-quartets and particularly interesting for their ability to catalyze reactions of peroxidation. This peroxidase-mimicking system found plenty of applications detailed in this chapter. Moreover, optimizations of experimental conditions are also discussed and highlight the versatility and easy-to-use characteristics of G-quadruplexes DNA. Also, synthetic G-quartets, mainly TASQ (for template-assembled synthetic G-quartets), developed by chemists showed their ability to mimic G-quadruplexes, thanks to the presence of a G-quartet. Thus, synthetic G-quartets proved their capability to catalyze peroxidase-mimicking reactions, and these new exciting nature-mimicking catalytic systems are presented in detail in this chapter.
Part of the book: Advanced Catalytic Materials
Among all the materials used in industry, gels play an increasingly important role. These so-called soft-matter materials are defined by their ability to fix a large amount of solvent, either organic (organogels) or aqueous (hydrogels). The large majority of hydrogels are made of natural or synthetic polymers, or natural proteins. However, a new kind of hydrogel has appeared: the peptide-based hydrogels, developed from short amino acids sequences (<20 amino acids). Due to their exceptional qualities in term of biocompatibility, biodegradability, and atom economy, these peptide-based hydrogels open new horizons in term of applications. They are mainly considered in the biomedical domain as injectable hydrogels, or as an extracellular culture matrix to support cell culture. While important, the possibilities of peptide design can exponentially grow using modified and non-natural amino acids instead of the “only” twenty natural ones. Thus, chemical modifications virtually offer infinite opportunities both to improve applications window and to fine-tune properties of the resulting hydrogels. In this context, this chapter proposes to review peptide and amino acid modifications reported to impact the resulting hydrogel.
Part of the book: Amino Acid