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Synthesis of Bioactive Peptides for Pharmaceutical Applications
Published in Peter Grunwald, Pharmaceutical Biocatalysis, 2019
Jaison Jeevanandam, Ashish Kumar Solanki, Shailza Sharma, Prabir Kumar Kulabhusan, Sapna Pahil, Michael K. Danquah
Smaller peptide chains are ligated to form longer peptides through chemical and enzyme-mediated technologies. This peptide fragment linking process is called “fragment condensation.” However, there are limitations associated with this technique, some of which are the racemization and formation of other interfering by-products. Development in the field of peptide ligation leads to a unique method called native chemical ligation (NCL). This method leads to the establishment of a native bond between Cysteine from N-terminal and thioester from C-terminal with two segments of unprotected peptides. After an initial exchange of chemo-selective thiol-thioester, the reaction progresses to form the desired peptide bond by an irreversible intramolecular S,N-acyl shift (Dawson et al., 1994).
In situ forming oxidized salecan/gelatin injectable hydrogels for vancomycin delivery and 3D cell culture
Published in Journal of Biomaterials Science, Polymer Edition, 2020
Zhiping Fan, Ping Cheng, Gaowei Yin, Zhengping Wang, Jun Han
Many crosslinking methods have been developed to prepare biomedical hydrogels in the past decade. Physically crosslinked hydrogels achieve a gel state by changing intermolecular forces such as hydrogen boding [8], hydrophobic interaction [9] and ionic force [10, 11]. What is quite different about the mechanism is that, chemically crosslinked hydrogels represent a hydrogel class that can transfer from sol to gel state by forming new covalent bonds in a polymer network through chemical reactions. There are many mechanisms of reactions, such as redox reactions [12], photo-polymerization [13], click chemistry [14–16], Michael reactions [17], native chemical ligation reactions [3, 4]. Chemical crosslinking improves the properties of the biomaterials steadily, but the introduced crosslinking agent often causes severe cytotoxicity. On the other hand, physically crosslinked hydrogels become unstable under the influence of environmental changes. Therefore, it remains a challenge to prepare natural biopolymer hydrogels with excellent biocompatibility under mild reaction conditions.
DFT study on C-S bond dissociation enthalpies of thiol-derived peptide models
Published in Journal of Sulfur Chemistry, 2020
Huifang Chang, Wenrui Zheng, Danfeng Zhu, Hongyun Xie
Native chemical ligation (NCL) [1–22] and its modified versions provide a highly efficient and powerful means to selectively link unprotected peptide and protein segments to produce proteins [23]. Traditionally, NCL is dependent on the presence of an appropriately placed cysteine (Cys) residues in an N-terminus of peptides to efficaciously cleave the target. Unfortunately, the comparatively low abundance of Cys (1.8%) in naturally occurring proteins led to develop new Cys surrogates that can expand the applicability of NCL. These efforts have recently concentrated on the study of ligation-desulfurization chemistry [24–27] (the reaction shown in Figure 1) that N-terminus of peptides (complexes A) and C-terminal acyl donor (complexes B) can generate thiol-derived peptide models (complexes C), and complexes C generates proteins through reductive desulfurization. In addition, Payne et al. [28] focused on the synthesis of γ-thiol-Glu and incorporate γ-thiol-Glu at the N-terminus of peptides to demonstrate the effective use of these peptides in ligation-desulfurization chemistry. Brik et al. [29] reported an innovative approach to ligation at Xaa-Leu (Xaa is any amino acid) sites by using β-mercaptoleucine combined with desulfurization which was used for the synthesis of HIV-1 Tat protein. To extend the applicability of ligation-desulfurization chemistry, extended research efforts have recently concentrated on the synthesis of β-, γ- and δ-thiol-derived amino acids, including thiol-derived phenylalanine (Phe), [30] valine (Val) [31,32], lysine (Lys) [33–36], threonine (Thr) [37], leucine (Leu) [20], isoleucine (Ile) [6], glutamine (Gln) [18], arginine (Arg) [38], aspartic acid (Asp) [39,40], glutamic acid (Glu) [28], serine(Ser) [41], tyrosine(Tyr) [42], and tryptophan (Trp) [43] (shown in Figure 1), as new Cys surrogates. These new Cys surrogates were incorporated at the N-terminus of peptides (complexes A) as N-terminal Cys surrogates (shown in Figure 1).