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Self-Healing Polymers
Published in Asit Baran Samui, Smart Polymers, 2022
The introduction of thiol functionality into a polymer can be done by using an appropriate sulfur-based initiator. However, due to the large transfer constants of thiols, the method cannot be used. The use of protected thiols can solve the problem, as the presence of protective groups maintains a lower transfer constant and the groups can be removed after the polymerization. Also, a sulfur-containing nucleophilic precursor of the thiol (e.g., thiourea) can be reacted with the halogen end groups of the polymers to form thiol end-functionalized polymers.22 The diester, derived from a hydroxyl group containing disulfide and bromo-derivative of carboxylic acid, is used as an initiator in the polymerization of styrene via ATRP, that results in polystyrene with an internal disulfide bond.23 The disulfide bond may undergo reversible reductive cleavage in the presence of dithiothreitol to produce a thiol-ended polymer. This polymer reacts with FeCl3, resulting in the oxidative coupling of the thiol groups so that by the regeneration of an internal disulfide bridge the original polymer is obtained. The self-healing concept is also extended to the epoxy network by incorporating disulfide links.
Biophysical and Biochemical Characterization of Peptide, Protein, and Bioconjugate Products
Published in Sandeep Nema, John D. Ludwig, Parenteral Medications, 2019
Tapan K. Das, James A. Carroll
The tertiary structure of a protein is often highly dependent on the formation of disulfide bonds. Disulfide bonds confer physical stability to the protein as well as ensuring that it maintains its active form [53]. For recombinantly produced proteins, the confirmation of disulfide bonds is a fundamental part of the elucidation of structure, and any variants present due to incorrectly paired disulfides need to be assessed. The number and arrangement of cysteine residues in a protein can lead to significant complexity for the determination of the disulfide connectivity.
Structures
Published in Thomas M. Nordlund, Peter M. Hoffmann, Quantitative Understanding of Biosystems, 2019
Thomas M. Nordlund, Peter M. Hoffmann
Figure 5.25 shows a small but heavily disulfide-bond stabilized protein of another sort, a potassium channel blocking toxin from the venom of scorpions. Toxins of this class typically have a Cys content 10 times that of the average protein—one in eight amino acids may be a Cys. The scorpion toxin is a potent blocker of K(+) channels. The protein structure is stabilized by four pairs of Cys residues that form disulfide bonds. Miniproject 5.10 investigates some implications of the stability of this sort of protein.
A secretory system for extracellular production of spider neurotoxin huwentoxin-I in Escherichia coli
Published in Preparative Biochemistry & Biotechnology, 2022
Changjun Liu, Qing Yan, Ke Yi, Tianhao Hu, Jianjie Wang, Zheyang Zhang, Huimin Li, Yutao Luo, Dongyi Zhang, Er Meng
In order to adapt to the environment, various venomous animals developed special organs, namely venom glands, for the production and injection of venoms to aid in prey capture and fight against predators. The most abundant animal toxins in animal venoms are a series of short bioactive peptides, principally stabilized by single or multiple disulfide bonds. For cysteine-rich peptides, disulfide bonds as an important post-translational modification are crucial for folding and maintaining three-dimensional structures and topological orientation.[37] The cysteine-rich peptides were usually stabilized by different disulfide bonds with different disulfide bridge patterns, such as inhibitory cystine knot (ICK) motif, disulfide-directed hairpin (DDH) motif, Kunitz type motif, and so on.[38].
Fabrication of poly(t-butyl betaine carboxylate)-based nanoparticles and study on their in vivo biosecurity
Published in Journal of Biomaterials Science, Polymer Edition, 2021
Xueyan Hou, Yongli Shi, Mingbo Yang, Shasha Yu, Xue Fan, Jinna Liang, Xiaofei Pan, Xiao Wang
The disulfide bond is redox sensitive, and it can break at the presence of oxidizing or reducing agents (e.g. GSH, oxygen). GSH is a common reductant, and tumor micro-environment has high GSH concentrations (1–10 mM) [34]. Therefore, in tumor cells, the disulfide bond will break with the action of GSH, which results in the disintegration of PCB-tBU-S-S-PDI NPs. It can speculate that this process will promote the encapsulated drug to release quickly. As for the cargo-free NPs, their size distribution will change greatly. As shown in Figure 2D, the PCB-tBU-S-S-PDI NPs suspensions were treated with GSH. With time prolonging, their size distribution changed greatly. This phenomenon was caused by the breakage of -S-S- bonds and the agglomeration of PDI segments. By contrast, without GSH, the size distribution of NPs did not change (as shown in Figure 2(D), insert). The reduction sensitivity of PCB-tBU-S-S-PDI NPs could quickly release antineoplastic drugs in tumor tissues due to the high GSH concentrations of tumor microenvironment. Therefore, the PCB-tBU-S-S-PDI NPs could be used as a candidate vehicle for antineoplastic drug delivery.
Spectroscopic investigation of the interaction between extracellular polymeric substances and tetracycline during sorption onto anaerobic ammonium-oxidising sludge
Published in Environmental Technology, 2021
Jiayi Li, Qingping Du, Huangqiang Peng, Dongyang Wei, Qian Liu, Yunqian Bi, Tao Liu, Junxi Lin, Chunyi Qin
Laser Raman spectra were used to identify the functional groups and chemical bonds of the EPS samples before and after interaction with tetracycline. Figure S2 showed the Raman spectra of EPS, where the Raman bands were assigned as in previous reports [38–42]. The band at 1645 cm−1 was attributed to C = C and C = O stretching vibration of lignin-like substances, whereas that near 1060 cm−1 was associated with C–O, C–C, and C–N stretching vibration. The Raman peak near 785 cm−1 was assigned to the pyrrole ring of the tryptophan side chain. C = O out-of-plane bending vibration of Amide VI appeared at 600 cm−1, whereas chain S–S stretching vibration of proteins and peptides was detected at 480–550 cm−1. The disulfide bond (S–S) is related to the stability of the protein and has a role in stabilising the conformation of the protein. The bands at 306–480 cm−1 were assigned to typical characteristic peaks of carbohydrates. The functional groups indicate the complexity of the EPS composition.