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Side chain cross link

Yan Zhao
Sequence-selective recognition of peptides in water has been one of the most important and yet unsolved problems in bioorganic and supramolecular chemistry. The motivation comes from not only the importance of these molecules in biology but also the fundamental challenges involved in the research. Molecular imprinting in doubly cross-linked surfactant micelles offers a unique solution to this problem by creating a "supramolecular code" on the micelle surface that matches the structural features of the peptide chain...
April 25, 2018: Chemistry: a European Journal
Shu-Wei Wu, Xifeng Liu, A Lee Miller, Yu-Shiuan Cheng, Ming-Long Yeh, Lichun Lu
In the present study, we fabricated non-toxic, injectable, and thermo-sensitive NIPAAm-g-chitosan (NC) hydrogels with thiol modification for introduction of disulfide cross-linking strategy. Previously, NIPAAm and chitosan copolymer has been proven to have excellent biocompatibility, biodegradability and rapid phase transition after injection, suitable to serve as cell carriers or implanted scaffolds. However, weak mechanical properties significantly limit their potential for biomedical fields. In order to overcome this issue, we incorporated thiol side chains into chitosan by covalently conjugating N-acetyl-cysteine (NAC) with carbodiimide chemistry to strengthen mechanical properties...
July 15, 2018: Carbohydrate Polymers
Hafiz M N Iqbal, Godfrey Kyazze, Thierry Tron, Tajalli Keshavarz
In the present study, we propose a green route to prepare poly(3-hydroxybutyrate) [(P(3HB)] grafted ethyl cellulose (EC) based green composites with novel characteristics through laccase-assisted grafting. P(3HB) was used as a side chain whereas, EC as a backbone material under ambient processing conditions. A novel laccase obtained from Aspergillus niger through its heterologous expression in Saccharomyces cerevisiae was used as a green catalyst for grafting purposes without the use of additional initiator and/or cross-linking agents...
March 2018: Saudi Journal of Biological Sciences
Juneyoung Lee, Jeong Hoon Ko, Kathryn M Mansfield, Peter C Nauka, Erhan Bat, Heather D Maynard
Effective delivery of therapeutic proteins is important for many biomedical applications. Yet, the stabilization of proteins during delivery and long-term storage remains a significant challenge. Herein, a trehalose-based hydrogel is reported that stabilizes insulin to elevated temperatures prior to glucose-triggered release. The hydrogel is synthesized using a polymer with trehalose side chains and a phenylboronic acid end-functionalized 8-arm poly(ethylene glycol) (PEG). The hydroxyls of the trehalose side chains form boronate ester linkages with the PEG boronic acid cross-linker to yield hydrogels without any further modification of the original trehalose polymer...
April 17, 2018: Macromolecular Bioscience
Osamu Kurita, Kaori Umetani, Yasushi Kokean, Hironori Maruyama, Toru Sago, Hiroyuki Iwamoto
Poly-γ-glutamic acid (PGA) was easily phosphorylated by direct addition of phosphorylating agents into the culture medium of Bacillus subtilis (natto). Tetrapolyphosphate salt was the most incorporated into PGA molecules of all used reagents. Phosphorylation occurred at the α-carboxyl side chains of PGA molecule. The amounts of bound phosphate to PGA were dependent on the amounts of added phosphorylating agent. In low molecular weight regions of less than 100 kDa, a cross-linked peak was observed in the phosphorylated PGAs, whereas their peaks at approximately 1000 kDa shifted to a higher molecular weight due to the bound phosphate...
April 6, 2018: World Journal of Microbiology & Biotechnology
Nicole Welsch, Ashley C Brown, Thomas H Barker, L Andrew Lyon
Excessive bleeding and resulting complications are a major cause of death in both trauma and surgical settings. Recently, there have been a number of investigations into the design of synthetic hemostatic agents with platelet-mimicking activity to effectively treat patients suffering from severe hemorrhage. We developed platelet-like particles from microgels composed of polymers carrying polyethylene glycol (PEG) side-chains and fibrin-targeting single domain variable fragment antibodies (PEG-PLPs). Comparable to natural platelets, PEG-PLPs were found to enhance the fibrin network formation in vitro through strong adhesion to the emerging fibrin clot and physical, non-covalent cross-linking of nascent fibrin fibers...
June 1, 2018: Colloids and Surfaces. B, Biointerfaces
Arnold Groehler, Stefan Kren, Qinglu Li, Maggie Robledo-Villafane, Joshua Schmidt, Mary Garry, Natalia Tretyakova
Myocardial infarction (MI) is a life-threatening condition that can occur when blood flow to the heart is interrupted due to a blockage in one or more of the coronary vessels. Current treatments of MI rapidly restore blood flow to the affected myocardium using thrombolytic agents or angioplasty. Adverse effects including inflammation, tissue necrosis, and ventricular dysfunction are, however, not uncommon following reperfusion therapy. These conditions are thought to be caused by a sudden influx of reactive oxygen species (ROS) to the affected myocardium...
May 20, 2018: Free Radical Biology & Medicine
Mohsen Ramezanpour, Jaeyong Lee, Svetla G Taneva, D Peter Tieleman, Rosemary B Cornell
The activity of CTP:phosphocholine cytidylyltransferase (CCT), a key enzyme in phosphatidylcholine synthesis, is regulated by reversible interactions of a lipid-inducible amphipathic helix (domain M) with membrane phospholipids. When dissociated from membranes, a portion of the M domain functions as an auto-inhibitory (AI) element to suppress catalysis. The AI helix from each subunit binds to a pair of α helices (αE) that extend from the base of the catalytic dimer to create a four-helix bundle. The bound AI helices make intimate contact with loop L2, housing a key catalytic residue, Lys122 The impacts of the AI helix on active-site dynamics and positioning of Lys122 are unknown...
May 4, 2018: Journal of Biological Chemistry
Marta Ruiz-Santaquiteria, Sonia de Castro, Miguel A Toro, Héctor de Lucio, Kilian Jesús Gutiérrez, Pedro A Sánchez-Murcia, María Ángeles Jiménez, Federico Gago, Antonio Jiménez-Ruiz, María-José Camarasa, Sonsoles Velázquez
Trypanothione reductase (TryR) is a well-established target in the search for novel antitrypanosomal and antileishmanial agents. We have previously identified linear and lactam-bridged 13-residue peptides derived from an α-helical region making up part of the dimeric interface of Leishmania infantum TryR (Li-TryR) which prevent trypanothione reduction by disrupting enzyme dimerization. We now show that i,i + 4 side-chain cross-linking with an all-hydrocarbon staple stabilizes the helical structure of these peptides and significantly improves their resistance to protease cleavage relative to previous linear and cyclic lactam analogues...
April 10, 2018: European Journal of Medicinal Chemistry
Victor L Davidson
A protein-derived cofactor is a catalytic or redox-active site in a protein that is formed by post-translational modification of one or more amino acid residues. These post-translational modifications are irreversible and endow the modified amino acid residues with new functional properties. This Perspective focuses on the following advances in this area that have occurred during recent years. The biosynthesis of the tryptophan tryptophylquinone cofactor is catalyzed by a diheme enzyme, MauG. A bis-FeIV redox state of the hemes performs three two-electron oxidations of specific Trp residues via long-range electron transfer...
March 6, 2018: Biochemistry
Chunyu Ru, Zhenhua Li, Chengji Zhao, Yuting Duan, Zhuang Zhuang, Fanzhe Bu, Hui Na
Novel side-chain-type sulfonated poly(arylene ether ketone) (SNF-PAEK) containing naphthalene and fluorine moieties on the main chain was prepared in this work, and a new amino-sulfo-bifunctionalized metal-organic framework (MNS, short for MIL-101-NH2 -SO3 H) was synthesized via a hydrothermal technology and postmodification. Then, MNS was incorporated into a SNF-PAEK matrix as an inorganic nanofiller to prepare a series of organic-inorganic hybrid membranes (MNS@SNF-PAEK-XX). The mechanical property, methanol resistance, electrochemistry, and other properties of MNS@SNF-PAEK-XX hybrid membranes were characterized in detail...
March 7, 2018: ACS Applied Materials & Interfaces
Ying-Wu Lin
Heme proteins are crucial for biological systems by performing diverse functions. Nature has evolved diverse approaches to fine-tune the structure and function of heme proteins, of which post-translational modification (PTM) is a primary method. As reviewed herein, a multitude of PTMs have been discovered for heme proteins in the last several decades, including heme-protein cross-links with heme side chains (Cys-heme, Tyr-heme and Asp/Glu-heme, etc) or porphyrin ring (Lys-heme and Tyr-heme, etc), heme modifications (sulfheme and nitriheme, etc), amino acids cross-links between two or among multiple residues (Cys-Cys, Tyr-His, Tyr-Cys, Met-Tyr-Trp, etc), and amino acids modifications by oxidation, nitration, phosphorylation and glycation, etc...
March 1, 2018: Archives of Biochemistry and Biophysics
C Zhang, J T Jones, H S Chand, M G Wathelet, C M Evans, B Dickey, J Xiang, Y A Mebratu, Y Tesfaigzi
IFN-γ is known as a pro-inflammatory cytokine, but can also block inflammation in certain chronic diseases although the underlying mechanisms are poorly understood. We found that IFN-γ rapidly induced Noxa expression and that extent of inflammation by repeated house dust mite exposure was enhanced in noxa-/- compared with noxa+/+ mice. Noxa expression blocked transforming necrosis factor alpha (TNF-α)-induced nuclear translocation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and the production of pro-inflammatory cytokines...
January 24, 2018: Mucosal Immunology
Yanli Niu, Tiantian Guo, Xiaoyan Yuan, Yunhui Zhao, Lixia Ren
Silver nanoparticles (AgNPs) show long-lasting and broad-spectrum antibacterial activity. Herein, PEGylated AgNPs were prepared in situ by complexing AgNO3 with the random copolymer of poly(ethylene glycol) methyl ether methacrylate (PEGMA) and polyacrylic acid via electrostatic interaction followed by in situ reduction. AgNP hybrid supramolecular hydrogels were thus prepared through host-guest inclusion between PEGMA side chains and α-cyclodextrins in aqueous solution. The hydrogels were physically cross-linked by both pseudopolyrotaxane crystallization and AgNPs, which showed temperature responsiveness and self-healing properties...
February 14, 2018: Soft Matter
Fiona J Flett, Emilija Ruksenaite, Lee A Armstrong, Shipra Bharati, Roberta Carloni, Elizabeth R Morris, C Logan Mackay, Heidrun Interthal, Julia M Richardson
Tyrosyl-DNA phosphodiesterase (Tdp1) is a DNA 3'-end processing enzyme that repairs topoisomerase 1B-induced DNA damage. We use a new tool combining site-specific DNA-protein cross-linking with mass spectrometry to identify Tdp1 interactions with DNA. A conserved phenylalanine (F259) of Tdp1, required for efficient DNA processing in biochemical assays, cross-links to defined positions in DNA substrates. Crystal structures of Tdp1-DNA complexes capture the DNA repair machinery after 3'-end cleavage; these reveal how Tdp1 coordinates the 3'-phosphorylated product of nucleosidase activity and accommodates duplex DNA...
January 2, 2018: Nature Communications
Kin-Ya Tomizaki, Ryuuichi Nanbu, Makoto Kasuga, Takahito Imai
Gold nanocrystals hold promise for use as catalysts and in photonic/plasmonic devices, electronics, sensing/imaging systems, drug delivery systems, and photothermal therapies due to their unique physical, chemical, and biocompatible properties. Various organic templates have been used to control of the size, shape, structure, surface modification and topology of gold nanocrystals. The synthesis of gold nanorods currently requires a cytotoxic surfactant to control morphology. To control the shape of gold nanocrystals, we previously demonstrated the de novo design and synthesis of a b-sheet-forming nonapeptide (RU006: Ac-AIAKAXKIA-NH2, X = L-2-naphthylalanine, Nal)...
December 13, 2017: Protein and Peptide Letters
Nozomi Itagaki, Yukari Oda, Toyoaki Hirata, Hung Kim Nguyen, Daisuke Kawaguchi, Hisao Matsuno, Keiji Tanaka
Poly(vinyl ether), with short oxyethylene side chains which possess a simple and relatively polar structure, should be a unique candidate for a bioinert material thanks to its solubility in water. On the basis of living cationic copolymerization and subsequent ultraviolet light irradiation, thin films of poly(2-methoxyethyl vinyl ether) with different cross-linking densities were prepared on solid substrates. The films were thickened in water, and the extent was dependent on the cross-linking density. Although the surface chemistry and aggregation states were almost identical to one another, the stiffness, or the softness, of the outermost region in the film was strongly dependent on the cross-linking density...
December 19, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Meghan A Smith, Kyle M Lancaster
The enzymes hydroxylamine oxidoreductase and cytochrome (cyt) P460 contain related unconventional "heme P460" cofactors. These cofactors are unusual in their inclusion of nonstandard cross-links between amino acid side chains and the heme macrocycle. Mutagenesis studies performed on the Nitrosomonas europaea cyt P460 that remove its lysine-heme cross-link show that the cross-link is key to defining the spectroscopic properties and kinetic competence of the enzyme. However, exactly how this cross-link confers these features remains unclear...
January 23, 2018: Biochemistry
Angel J Moreno, Petra Bacova, Federica Lo Verso, Arantxa Arbe, Juan Colmenero, José A Pomposo
Polymeric single-chain nanoparticles (SCNPs) are soft nano-objects synthesized by purely intramolecular cross-linking of single polymer chains. By means of computer simulations, we investigate the conformational properties of SCNPs as a function of the bending stiffness of their linear polymer precursors. We investigate a broad range of characteristic ratios from the fully flexible case to those typical of bulky synthetic polymers. Increasing stiffness hinders bonding of groups separated by short contour distances and increases looping over longer distances, leading to more compact nanoparticles with a structure of highly interconnected loops...
January 24, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Prashant K Singh, Naseer Iqbal, Harsh V Sirohi, Hridoy R Bairagya, Punit Kaur, Sujata Sharma, Tej P Singh
The mammalian heme peroxidases including lactoperoxidase (LPO), myeloperoxidase (MPO), eosinophil peroxidase (EPO) and thyroid peroxidase (TPO) contain a covalently linked heme moiety. Initially, it was believed that the heme group was fully cross-linked to protein molecule through at least two ester linkages involving conserved glutamate and aspartate residues with 1-methyl and 5-methyl groups of pyrrole rings A and C respectively. In MPO, an additional sulfonium ion linkage was present between 2-vinyl group of pyrrole ring A of the heme moiety and a methionine residue of the protein...
March 2018: Progress in Biophysics and Molecular Biology
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