Scission Of Disulfide Bond Research Articles

Coordination effect of biocatalyst dithiothreitol and aramid fiber interlayer for lithium-sulfur batteries

Lithium-sulfur (Li–S) batteries have great development potential in the field of new energy because of their high specific capacity. However, problems such as poor conductivity of sulfur (S) and "shuttle effect" hinder the practical application of Li–S batteries. In this work, dithiothreitol (DTT) was used as a coating to form a 3D crosslinked network structure with aramid paper (AP) interlayer and inhibiting the notorious shuttle effect. DTT assisted scission of disulfide bond (-S–S- bonds) in high-order polysulfides to inhibit the diffusion of polysulfides, and the loose porous AP interlayer can significantly enhance the utilization of active substances. The successful combination of DTT and AP interlayer showed significant synergistic effect, which improved the electrochemical performance of the Li–S batteries, leading to the discharge-specific capacity of 697 mAh/g at 5C.

DNA-BSA interaction, cytotoxicity and molecular docking of mononuclear zinc complexes with reductively cleaved N2S2 Schiff base ligands

The synthesis of three potentially tetradentate, N2S2 Schiff-base-ligands, containing a disulfide bond, LThioSSLThio(L1), LBrSSLBr (L2) and LDiMeOSSLDiMeO (L3) are reported. These ligands undergo reductive disulfide bond scission upon reaction with PPh3 in the presence of Zn2+ ion. [LDiOMeS]−, [LThioS]− and [LBrS]− are the resulting bidentate thiolate-imine anions respectively, which upon reaction with Zn2+ produce three new zinc(II) complexes: [Zn(LThioSN)2] (1), [Zn(LBrSN)2] (2) and [Zn(LDiOMeSN)2] (3). The structures of (L1) and 1–3 complexes were determined by X-ray diffraction. The interaction of 1–3 with CT-DNA have been investigated by absorption, emission, and CD spectroscopic methods and thermal denaturation measurements. The resulting data reveal that 1–3 show effective binding to CT-DNA (Kb = 2.2 × 104 to 1 × 105 L mol−1). The binding mode of DNA with 1–3 has also been investigated by molecular docking. The protein binding ability of 1–3 has been tested by monitoring the tryptophan emission intensity using BSA as a model protein. The quenching mechanism of BSA by the zinc complexes is static (kq = 1.66 to 3.4 × 1013 L mol−1 s−1). It is remarkable that 1–3 exhibit effective cytotoxicity against two human tumour cell lines (HeLa and MCF-7). The potent cytotoxic effects of 2 and 3, with IC50 values of 19.93 and 20.11 respectively, are higher relative to clinically used cisplatin (IC50 = 23.50) against the MCF-7 cell line, indicating that 2 and 3 may have the potential to act as effective metal-based anticancer drugs.

Facile synthesis of Co3O4 nanoparticles from a novel tetranuclear cobalt(III) complex. Application as efficient electrocatalyst for oxygen evolution reaction in alkaline media

A tetranuclear cobalt complex [Co4III(L′)6] was synthesized by the direct reaction of cobalt(II) acetate with a N2S2 Schiff base ligand H2L containing a disulfide bond under aerobic conditions {H2L = 2,2′-bis(2-hydroxynaphthyliminobenzyl)disulfide}. The X-ray crystal structure of [Co4III(L′)6] indicates reductive disulfide bond scission of H2L upon reaction with Co2+ to give [L′]2–. Furthermore, cobalt oxide nanoparticles of about 30 nm size were synthesized by thermal decomposition of [Co4III(L′)6] as a precursor. The Co3O4 nanoparticles were characterized by XRD, FE-SEM, TEM, and FT-IR spectroscopy. The electrocatalytic activity of the resulting oxide was examined in oxygen evolution reaction (OER) by cyclic voltammetry (CV) and linear sweep voltammetry (LSV) in 1.0 mol L−1 KOH. The NPs displays efficient electrocatalytic activity for oxygen evolution reaction with a current density of 10.0 mA cm−2 at 1.65 V, good onset potential of 1.52 V vs. RHE and small Tafel slope of 44 mV dec−1.

Leveraging Electron Transfer Dissociation for Site Selective Radical Generation: Applications for Peptide Epimer Analysis.

Traditional electron-transfer dissociation (ETD) experiments operate through a complex combination of hydrogen abundant and hydrogen deficient fragmentation pathways, yielding c and z ions, side-chain losses, and disulfide bond scission. Herein, a novel dissociation pathway is reported, yielding homolytic cleavage of carbon-iodine bonds via electronic excitation. This observation is very similar to photodissociation experiments where homolytic cleavage of carbon-iodine bonds has been utilized previously, but ETD activation can be performed without addition of a laser to the mass spectrometer. Both loss of iodine and loss of hydrogen iodide are observed, with the abundance of the latter product being greatly enhanced for some peptides after additional collisional activation. These observations suggest a novel ETD fragmentation pathway involving temporary storage of the electron in a charge-reduced arginine side chain. Subsequent collisional activation of the peptide radical produced by loss of HI yields spectra dominated by radical-directed dissociation, which can be usefully employed for identification of peptide isomers, including epimers. Graphical Abstract ᅟ.

Reduction-responsive zwitterionic nanogels based on carboxymethyl chitosan for enhancing cellular uptake in drug release

Stimuli-responsive nanoparticles as drug carriers have promising applications in chemotherapy. To increase stability of nanogels in the bloodstream and to enhance intracellular drug uptake, reduction-responsive zwitterionic nanogels were prepared using carboxymethyl chitosan as a material. The preparation included modification of carboxymethyl chitosan and crosslinking by of N,N-Bis(acryloyl) cystamine. The nanogels possessed zwitterions of carboxyl and amino groups, and showed excellent non-fouling behavior against protein adsorption. In the presence of a reduction agent such as glutathione (GSH), the nanogels were dissociated due to scission of disulfide bonds in the crosslinking structure, leading to drug release in tumor cells. The nanogels were non-cytotoxic, biocompatible, biodegradable, and would be potentially used as anticancer drug delivery carriers in controlled release for enhancing cellular drug uptake.

New Zn(II) complexes with N2S2 Schiff base ligands. Experimental and theoretical studies of the role of Zn(II) in disulfide thiolate-exchange

Described are the synthesis and characterization of two, potentially tetradentate, N2S2 Schiff-base ligands, containing a disulfide bond, N,N′-bis(3-phenylprop-2-en-1-ylidene)-2,2′-disulfanediyldianiline (L1) and N,N′-bis(3,3-diphenylprop-2-en-1-ylidene)-2,2′-disulfanediyldianiline (L2), and their reaction with Zn2+. Surprisingly, both L1 and L2 undergo reductive disulfide bond scission upon reaction with Zn2+ in alcoholic media to give, under alcohol oxidation, the respective Zn(NS)2 complexes Zn(L3)2 (1) and Zn(L4)2 (2), where the L3 and L4 are the respective bidentate thiolate-imine anions. The ligands L1 and L2 and the complexes 1 and 2 have been characterized spectroscopically, and the crystal and molecular structures of the two complexes have been determined by single crystal X-ray diffraction. The coordination geometry around Zn(II) centers in both complexes is a distorted tetrahedron. In addition, DFT calculations (B3LYP/LANL2DZ/6-311++G(d,p)) support the structure of 1. Cyclic voltammetric studies demonstrate that Zn(II) shifts the reduction potential of the disulfide ligands L1 and L2 to less negative values thus making them more susceptible to reductive cleavage of the disulfide bond. The results of semi-empirical PM6 calculations offer key insight into the nature of the transition state for this reaction.

Retraction: Unraveling Solvent-Mediated Reaction Pathways Leading to Regiospecific Mechanochemical Cleavage of Disulfide Bonds in Peptides

Stressing disulfide bonds! Nucleophilic thiol-disulfide exchange reactions within the I27 domain of titin were previously investigated with force clamp AFM. Here, all possible pathways associated with disulfide bond scission at constant tensile force are revealed in terms of end-to-end distances by using force clamp molecular dynamics. The simulations, together with experimental data unravel the competition between mechanochemical bond activation and solvent-mediated regiospecificity exhibited during SS bond cleavage due to the nucleophilic substitution mechanism within a stretched peptide.

EFFECT OF OXIDATION STRESS ON THE MECHANICAL PROPERTY OF HUMAN HAIR

Ultraviolet (UV) irradiation causes changes in mechanical property and surface property of human hair. These changes of hair fiber can be more significant especially in bleached hair, and affects tactile sensation during combing or handling. In this study, changes in bending properties of bleached and UV-irradiated hair were evaluated. Bending stiffness of bleached hair was larger than that of untreated hair, and was increased further by UV-irradiation. By FT-IR measurement, it was found that bleaching and UV-irradiation caused oxidative scission of disulfide bonds in keratin, and that α-helix structure increased relatively. Based on these results, the mechanism of change in bending property and microscopic structure caused by oxidation stress was discussed. It was considered that deterioration in the mechanical property and chemical structure induced by UV irradiation was promoted with the bleached hair, because of ROS formation by residual hydrogen peroxide and decrease in the defensive function against oxidative stress.

Use of Sonication to Probe Wheat Gluten Structure

ABSTRACTVariation in power and time of sonication of gluten and glutenin suspensions was used to gain information about the mechanism of molecular breakdown. At low power, an increase in sulfhydryl (SH) content of solubilized gluten could be ascribed to additional glutenin brought into the solution. Higher power sonication of gluten suspensions, at constant protein concentration and with increasing times, progressively shifted the molecular weight distribution (measured by size exclusion HPLC) to lower molecular weights. It was accompanied by a parallel decrease in SH content. This suggested that the freed cysteine residues formed by scission of disulfide (SS) bonds, caused by sonication, reacted to form new intramolecular SS bonds with free cysteines on the same molecular fragments. Circular dichroism measurements appeared to support this conclusion. High‐power ultrasound produced SE‐HPLC profiles with diffuse peaks corresponding to HMW‐GS and LMW‐GS. SDS‐PAGE patterns of protein fractions obtained in different elution ranges of SEHPLC confirmed that individual subunits had been produced by sonication. A fraction of the polymeric protein eluting at the void volume of SE‐HPLC appeared to be resistant to breakdown by sonication.

Regional distribution of endothelin receptor in porcine cardiovascular tissues

To clarify effecting sites of endothelin (ET) in a circulation system, we have identified specific receptors for porcine ET(ET-1) and investigated the distribution in the porcine cardiovascular tissues. Scatchard analysis of 125I-porcine ET binding indicated the presence of a single class of high-affinity binding sites. The binding was highly specific for ET-1, because (1) none of the other various peptides or Ca 2+-channel antagonists affected the binding, (2) the scission of disulfide bonds, the digestion of the C-terminal 6-amino acid residues, or nitrophenylsulfenylization of the C-terminal Trp 21 of ET-1 markedly reduced the binding ability and, (3) ET-1 showed the highest affinity for the vascular receptor among three ET isopeptides. Cardiac atria possessed the highest density (2.7 pmol/mg protein) of ET receptors of all the tissues examined, including thoracic aorta, cardiac atria and cardiac ventriculi, basilar, renal, coronary and pulmonary branch arteries, coronary, renal and jugular veins, and small vessels of pia mater encephali. Small vessels, renal and coronary arteries also showed relatively high density (0.8–1.4 pmol/mg protein). Various veins examined also showed considerable density (0.45–0.74 pmol/mg protein). The apparent K d of cardiac ET receptors (0.76 nM) was significantly greater than that of the receptors of the other tissue (0.06–0.14 nM). The extensive distribution and the local enrichment of ET receptor in a cardiovascular system strongly suggests that ET is one of the essential endogenous substances to control the tone of the vasculature.

Intramolecular cross-linking of proteins by formation of lysinoalanine or lanthionine. Modification of disulfides in ovomucoids.

The disulfide bonds of ovomucoids were cleaved and new sulfur‐containing cross‐links were introduced by two separate chemical modification methods: (1) alkali treatment, and (2) cyanolysis. Alkali and cyanolytic treatments were used to cleave disulfide bonds and to introduce new synthetic nonreducible cross‐links consisting of residues of lysinoalanine (N‐(dl‐2‐amino‐2‐carboxyethyl)‐l‐lysine) and lanthionine (bis(2‐amino‐2‐carboxyethyl)sulfide). The two ovomucoids studied were turkey and penguin ovomucoids, which are “double‐headed” inhibitors of proteolytic enzymes with one inhibitory site for bovine trypsin and another for bovine α‐chymotrypsin or subtilisin. Trypsin does not compete with either α‐chymotrypsin or subtilisin, but the latter compete with one another, apparently for the same inhibitory site. The stability of inhibitory activities as a function of disulfide bond scission and the formation of new nondisulfide cross‐links was studied. In both methods of disulfide modification of turkey ovomucoid, inhibitory activity against trypsin was more stable with respect to the extent of modification than was inhibitory activity against chymotrypsin or subtilisin. With penguin ovomucoid, inhibitory activity against subtilisin was always more stable than activity against trypsin or chymotrypsin with both methods. With both ovomucoids it was thus possible to produce single‐headed inhibitors from the double‐headed inhibitors. The formation of the nonreducible cross‐links of lanthionine from cystines, and of lysinoalanines from cystines and lysines, with retention of a biochemical activity, suggests that such a procedure may have at least limited use as a cross‐linking method.

Time-crosslink density reduction investigated by photochemical scission

Abstract The applicability of a time-crosslink density reduction principle to the terminal region creep behavior of plasticized polyurethane samples was investigated. Such reduction is similar to the well known time-temperature reduction principle, except that variation in a crosslink density, rather than temperature, is responsible for differences observed in material response. The sets of experiments which were analyzed were each carried out on single samples changes in crosslink density were caused by the photo-induced scission of disulfide bonds incorporated in the network. In this way, a high degree of experimental precision was realized. Our results indicate that time-crosslink density reduction is appropriate for this system, but the time scale shift observed here is much less sensitive to changes in crosslink density than previously reported for other systems. Changes in network topology which are not accurately reflected in the crosslink density may be responsible for this difference. Furthermore...

Chemical Reactions of the Copper Intrauterine Device

This study investigated the reactions of metallic copper with various biologic substrates to account for the loss of metallic copper in the IUD. Purified copper foil of .005 cm thickness was cut into strips and placed in solutions of the substrates then incubated at 37 degrees C. Loss of metallic copper was determined by measuring the cupricion concentration in the solutions with the diethyl ammonium salt of diethyldithiocarbamic acid. This compound forms a yellow chelate with cupricion which has an absorption maximum at 446 nm. The optical density of samples was compared with various mixtures of copper sulphate a chelating agent on a Cary 15 spectrophotometer at 446 nm. Human uterine secretion which had been aspirated at the midpoint of the menstrual cycle and similar material with saline solution added were studied. The uterine secretion with saline showed greater cupric ion concentration than when only saline was used with a similar size strip of copper or when an alkaline buffer was added to the saline. Secretion incubated with saline but without the copper showed a coherent and mucoid mass. 18 hour incubation of copper with midcycle mucus to which no saline had been added showed lyses of the mucoid material and the cupric ion concentration increased. Experiments with postovulatory cervical mucus gave similar results. Copper-inhibited cervical mucus brought into contact with washed sperm resulted in complete inactivation of the sperm within 2 hours. The sperm showed increased motility just prior to their demise. Such inactivation did not occur when no copper had been added to the incubated mucus. When bovine serum albumin solution was incubated with copper foil the amount of cupric ions formed was proportional to the surface area of the copper strip to the time of incubation and to serum albumin concentrations. The presence of oxygen was also found to be important. Oxidized and reduced glutathione were incubated with copper strips. The oxidized formed cupric ions while the reduced showed only a slight reaction indicating that the disulfide bond is a critical group in the dissolution process by biologic materials presumably acting as an oxidizing agent. Precipitation of modified albumin by cupric ions shown to be reversed at high albumin concentrations. Copper-incubated albumin samples showed less SH content than untreated albumin apparently because the copper ions catalyse the air oxidation of the SH groups present or formed by reduction with copper metal. The formation of SH groups in cystine can be demonstrated. When cystine is incubated with metallic copper in the presence of p-dichloroindophenol there is a fading of the blue color of the dye at the surface of the copper strip indicating formation of reducing groups. For disulfide substrates the metal reduces the S-S linkage. When alkaline phosphatase and carbonic anhydrase were incubated with copper inhibition of enzyme activity ensued after 1 hour. The amount of copper dissolved by uterine secretions from a 200 mm copper surface amounts to 60 mcg a day. The effectiveness of the copper IUD may arise in 2 general ways: 1) the scission of disulfide bonds resulting in a modification of S-S containing proteins and mucus causing precipitation of albumins which may change the internal wall in such a way as to prevent implantation.

Cleavage of the disulfide bonds of cystine and oxidized glutathione by phosphorothioate

The scission of disulfide bonds in low molecular weight model compounds such as cystine and oxidized glutathione is presented. The experimental results obtained suggest that the reaction between phosphorothioate and cystine proceeds according to the equation RSSR + ( O 3 PS) ⇄ ( RS) + ( RSSPO 3). It was shown that this reaction is reversible in the pH range 4.5 to 9.5. The reaction is also pH dependent, and has a maximum rate at pH 8.0. Equilibrium constants have been calculated from the results obtained from the reaction with N-ethylmaleimide and found to be 2.2 × 10 −1 liter/mole at pH 8.0, and 9 × 10 −2 liter/mole at pH 6.8. Pertinent data concerning the reaction of phosphorothioate with several sulfhydryl reagents are included.

Kinetics and Temperature Dependence of the Chemical Stress Relaxation of Wool Fibers

The stress relaxation process of keratin fibers may be divided into two stages, the first rapid stage involving hydrogen bond breakdown and the second slower stage being connected with disulfide bond scission. The temperature dependence of the second disulfide-controlled stage of stress relaxation of wool fibers from extensions of 20 and 40% was investigated at pH 7.0, both in the presence and absence of the sulfhydryl- blocking agent N-ethylmalimide (NEMI). By plotting the relaxation modulus Er as a function of temperature, a transition at 70°C was observed for untreated wool fibers. An increase in the SH content by partial reduction of the wool cystine decreases this transition temperature, as was expected from previous evidence of the SH dependence of the transition temperature under stress obtained from stress-strain curves [20]. By normalizing the stress at any time with a stress value in the presence of the SH-group blocking agent, it was possible to eliminate the first stage of stress relaxation without losing any component of the second stage. The viscoelastic behavior of the second stage was found to approximate that of a single Maxwellian element. The controlling mechanism in 'this stage appears to be a disulfide interchange catalyzed by free. SH groups, with an activation energy of approximately 23 kcal mole, which is independent of the strain level.

Immunochemical studies on disulfide bonding in the photochemical apparatus of Rhodospirillum rubrum

An immunochemical study has been made of chromatophores of Rhodospirillum rubrum and of fragments obtained from these cell particles by sonic irradiation and chemical treatment. Serologically univalent material is released from chromatophores by chemical scission of disulfide bonds. The data indicate that chromatophore antigens are inserted into the structure as a repeating matrix of antigenic sites spaced with the determinant groups placed between each pair of disulfides. Evidence for the reversibility of antigen scission and information about the nature of the chromatophore subunits are presented.