Cleavage Of Disulfide Bonds Research Articles

Dielectric-barrier discharge (DBD) plasma treatment reduces IgG binding capacity of β-lactoglobulin by inducing structural changes

The present study investigated the effects of dielectric-barrier-discharge (DBD) plasma treatment (12 kHz, 40 kV) at 1, 2, 3, and 4 min on the reduction of the immunoglobulin G (IgG) binding capacity of β-lactoglobulin (β-LG). The IgG binding capacity of β-LG was reduced by 58.21% following a plasma treatment time of 4 min, as confirmed by western-blot and ELISA analyses. The reduction in IgG binding capacity of β-LG was directly related to a stepwise change in its structure. The initial drop in the IgG binding capacity of β-LG was found to be caused by conformational alteration, free sulfhydryl exposure and cross-linkage of molecules induced by oxidation of NH–/NH2– functional groups of peptide bonds and of sensitive amino acid residues (Tyr, Trp) as confirmed by SDS-PAGE, surface hydrophobicity and multi-spectroscopic analyses. Plasma treatment of more than 3 min resulted in cleavage of disulfidebonds and fragmentation of β-LG that was confirmed by LC–MS/MS analysis, which resulted a further decline in the IgG binding capacity of β-LG. Plasma treatment therefore has great potential as a substitute treatment for enzymatic hydrolysis for the production of hypoallergenic milk protein-based products.

Polypseudorotaxanes Derived from Tetraphenylethylene: Preparation and Tandem-Activated Aggregation-Induced Emission.

Tuning the fluorescence of aggregation-induced emission (AIE)-based materials in a reversible way is essential and a requisite for their applications. The multiple host-guest interactions of polypseudorotaxanes (PPRs) could alter the aggregation state of hydrophobic AIE-based polymeric materials and consequently switch the fluorescence. Herein, tetraphenylethylene (TPE) as a typical AIE molecule has been incorporated into the main chains of the guest polyurethane via a step condensation between poly(ethylene glycol) (PEG)-based dicarbonate and TPE-diamine along with the cleavable disulfide bonds. γ-Cyclodextrins (γ-CDs) can selectively recognize the TPE units at the polyurethane chains to afford a PPR. Hydrophilic PEG segments and γ-CD molecules in the PPR could promote the disaggregation of TPE units, suppressing the fluorescence emission of TPE. To restore the aggregated state and fluorescence of TPE units, tris(2-carboxyethyl)phosphine (TCEP) and α-amylase are sequentially introduced to cleave the disulfide bonds and cut α-1,4 glycosidic bonds of γ-CD, reactivating the AIE behavior of PPR tandemly and accomplishing the reversible cycle of tuning the fluorescence of TPE. The present study provides a tandem way to switch the AIE behavior of polymeric materials reversibly.

Enhancing surface performance of wool using reduced ionic liquid

Wool surface modification is essential for its application in the textile industry. In this work, a novel approach using reduced ionic liquid (IL) was applied to modify the surface of wool and enhance surface-related properties of wool for overcoming the unsustainable drawbacks in the present methods. The results from the surface morphology indicated that the wool was gradually dissolved from the outside to the inside of the fiber. The treated wool was characterized using the X-ray photoelectron spectroscopy (XPS), fluorescence microscopy and the Allwörden reaction. Moreover, felting shrinkage, mechanical properties, and dyeing properties of the treated wool were analyzed. Disulfide bonds were cleaved during the process from XPS test. The Allwörden reaction and fluorescence analysis showed damaged scale layer on the wool surface and an intact fiber main body with an acceptable loss of mechanical properties. Compared with the untreated wool, the anti-felting properties and dyeing performance improved due to the cleavage of disulfide bonds and the removal of the lipid layer, indicating that the treatment could modify the wool surface. Overall, the study supports a novel, facile and highly efficient approach for preparing a value-adding natural protein fiber with a potential for large-scale production.

Disulfide bond based cascade reduction-responsive Pt(IV) nanoassemblies for improved anti-tumor efficiency and biosafety

The platinum-based drugs prevail in the therapy of malignant tumors treatment. However, their clinical outcomes have been heavily restricted by severe systemic toxicities. To ensure biosafety and efficiency, herein, we constructed a disulfide bond inserted Pt(IV) self-assembled nanoplatform that is selectively activated by rich glutathione (GSH) in tumor site. Disulfide bond was introduced into the conjugates of oxaliplatin (IV) and oleic acid (OA) which conferred cascade reduction-responsiveness to nanoassemblies. Disulfide bond cleavage and reduction of Pt(IV) center occur sequentially as a cascade process. In comparison to oxaliplatin solution, Pt(IV) nanoparticles (NPs) achieved prolonged blood circulation and higher maximum tolerated doses. Furthermore, Oxa(IV)-SS-OA prodrug NPs exhibited potent anti-tumor efficiency against 4T1 cells and low toxicities in other normal tissues, which offers a promising nano-platform for potential clinical application.

Comprehensive Analysis of Tryptic Peptides Arising from Disulfide Linkages in NISTmAb and Their Use for Developing a Mass Spectral Library.

This work presents methods for identifying and then creating a mass spectral library for disulfide-linked peptides originating from the NISTmAb, a reference material of the humanized IgG1k monoclonal antibody (RM 8671). Analyses involved both partially reduced and non-reduced samples under neutral and weakly basic conditions followed by nanoflow liquid chromatography tandem mass spectrometry (LC–MS/MS). Spectra of peptides containing disulfide bonds are identified by both MS1 ion and MS2 fragment ion data in order to completely map all the disulfide linkages in the NISTmAb. This led to the detection of 383 distinct disulfide-linked peptide ions, arising from fully tryptic cleavage, missed cleavage, irregular cleavage, complex Met/Trp oxidation mixtures, and metal adducts. Fragmentation features of disulfide bonds under low-energy collision dissociation were examined. These include (1) peptide bond cleavage leaving disulfide bonds intact; (2) disulfide bond cleavage, often leading to extensive fragmentation; and (3) double cleavage products resulting from breakages of two peptide bonds or both peptide and disulfide bonds. Automated annotation of various complex MS/MS fragments enabled the identification of disulfide-linked peptides with high confidence. Peptides containing each of the nine native disulfide bonds were identified along with 86 additional disulfide linkages arising from disulfide bond shuffling. The presence of shuffled disulfides was nearly completely abrogated by refining digest conditions. A curated spectral library of 702 disulfide-linked peptide spectra was created from this analysis and is publicly available for free download. Since all IgG1 antibodies have the same constant regions, the resulting library can be used as a tool for facile identification of “hard-to-find” disulfide-bonded peptides. Moreover, we show that one may identify such peptides originating from IgG1 proteins in human serum, thereby serving as a means of monitoring the completeness of protein reduction in proteomics studies. Data are available via ProteomeXchange with identifier PXD023358.

Development of a New Hyaluronic Acid Based Redox-Responsive Nanohydrogel for the Encapsulation of Oncolytic Viruses for Cancer Immunotherapy.

Oncolytic viruses (OVs) are emerging as promising and potential anti-cancer therapeutic agents, not only able to kill cancer cells directly by selective intracellular viral replication, but also to promote an immune response against tumor. Unfortunately, the bioavailability under systemic administration of OVs is limited because of undesired inactivation caused by host immune system and neutralizing antibodies in the bloodstream. To address this issue, a novel hyaluronic acid based redox responsive nanohydrogel was developed in this study as delivery system for OVs, with the aim to protect the OVs following systemic administration. The nanohydrogel was formulated by water in oil (W/O) nanoemulsion method and cross-linked by disulfide bonds derived from the thiol groups of synthesized thiolated hyaluronic acid. One DNA OV Ad[I/PPT-E1A] and one RNA OV Rigvir® ECHO-7 were encapsulated into the developed nanohydrogel, respectively, in view of their potential of immunovirotherapy to treat cancers. The nanohydrogels showed particle size of approximately 300–400 nm and negative zeta potential of around −13 mV by dynamic light scattering (DLS). A uniform spherical shape of the nanohydrogel was observed under the scanning electron microscope (SEM) and transmission electron microscope (TEM), especially, the successfully loading of OV into nanohydrogel was revealed by TEM. The crosslinking between the hyaluronic acid chains was confirmed by the appearance of new peak assigned to disulfide bond in Raman spectrum. Furthermore, the redox responsive ability of the nanohydrogel was determined by incubating the nanohydrogel into phosphate buffered saline (PBS) pH 7.4 with 10 μM or 10 mM glutathione at 37 °C which stimulate the normal physiological environment (extracellular) or reductive environment (intracellular or tumoral). The relative turbidity of the sample was real time monitored by DLS which indicated that the nanohydrogel could rapidly degrade within 10 h in the reductive environment due to the cleavage of disulfide bonds, while maintaining the stability in the normal physiological environment after 5 days. Additionally, in vitro cytotoxicity assays demonstrated a good oncolytic activity of OVs-loaded nanohydrogel against the specific cancer cell lines. Overall, the results indicated that the developed nanohydrogel is a delivery system appropriate for viral drugs, due to its hydrophilic and porous nature, and also thanks to its capacity to maintain the stability and activity of encapsulated viruses. Thus, nanohydrogel can be considered as a promising candidate carrier for systemic administration of oncolytic immunovirotherapy.

Targeted Subcellular Protein Delivery Using Cleavable Cyclic Cell-Penetrating Peptide-Conjugates.

Proteins conjugated to cyclic cell-penetrating peptides (cCPPs) haAbstractve been shown to be effectively taken up by living cells. Conjugation of proteins to cCPPs in a cleavable manner leads to localization in the cytosol and immediate bioavailability of the protein after uptake. Here we describe how mCherry, a fluorescent protein, can be targeted to a membrane-bound compartment, the nucleus, and a subcellular structure like the actin cytoskeleton after cCPP-mediated uptake into living cells. Targeting peptides are genetically fused to the mCherry protein sequence and the protein is conjugated to the cCPP via a cleavable disulfide bond. Localization of mCherry in the nucleus or the actin skeleton respectively can be observed by live cell confocal fluorescence microscopy.

Trioxatriangulenium (TOTA+) as a robust carbon-based Lewis acid in frustrated Lewis pair chemistry.

We report the reactivity between the water stable Lewis acidic trioxatriangulenium ion (TOTA+) and a series of Lewis bases such as phosphines and N-heterocyclic carbene (NHC). The nature of the Lewis acid–base interaction was analyzed via variable temperature (VT) NMR spectroscopy, single-crystal X-ray diffraction, UV-visible spectroscopy, and DFT calculations. While small and strongly nucleophilic phosphines, such as PMe3, led to the formation of a Lewis acid–base adduct, frustrated Lewis pairs (FLPs) were observed for sterically hindered bases such as P(tBu)3. The TOTA+–P(tBu)3 FLP was characterized as an encounter complex, and found to promote the heterolytic cleavage of disulfide bonds, formaldehyde fixation, dehydrogenation of 1,4-cyclohexadiene, heterolytic cleavage of the C–Br bonds, and interception of Staudinger reaction intermediates. Moreover, TOTA+ and NHC were found to first undergo single-electron transfer (SET) to form [TOTA]·[NHC]˙+, which was confirmed via electron paramagnetic resonance (EPR) spectroscopy, and subsequently form a [TOTA–NHC]+ adduct or a mixture of products depending the reaction conditions used.

Inline electrochemical reduction of NISTmAb for middle-up subunit liquid chromatography-mass spectrometry analysis.

Disulfide bond reduction within antibody mass spectrometry workflows is typically carried out using chemical reducing agents to produce antibody subunits for middle-down and middle-up analysis. In this contribution we offer an online electrochemical reduction method for the reduction of antibodies coupled with liquid chromatography (LC) and mass spectrometry (MS), reducing the disulfide bonds present in the antibody without the need for chemical reducing agents. An electrochemical cell placed before the analytical column and mass spectrometer facilitated complete reduction of NISTmAb inter- and intrachain disulfide bonds. Reduction and analysis were carried out under optimal solvent conditions using a trapping column and switching valve to facilitate solvent exchange during analysis. The level of reduction was shown to be affected by electrochemical potential, temperature and solvent organic content, but with optimization, complete disulfide bond cleavage was achieved. The use of an inline electrochemical cell offers a simple, rapid, workflow solution for liquid chromatography mass spectrometry analysis of antibody subunits.

Insights into the Redox Chemistry of Organosulfides Towards Stable Molecule Design in Nonaqueous Energy Storage Systems

AbstractNonaqueous redox flow batteries (RFBs) have great potential to achieve high‐energy storage systems. However, they have been limited by low solubility and poor stability of active materials. Here we demonstrate organosulfides as a new‐type model material system to explore the rational design of redox‐active molecules in nonaqueous systems. The tetraethylthiuram disulfide (TETD) molecule shows high solubility in various common organic solvents and achieves a high reversible capacity of ca. 50 Ah L−1 at a high concentration of 1 M. The resonance structures in the reduced product endow the molecule with high electrochemical stability in different organic electrolytes. The underlying mechanism in redox chemistry of organodisulfides involving the cleavage and reformation of disulfide bonds is revealed by material/structural characterizations. This study provides a new perspective of molecule designs for the development of redox‐active materials for high‐performance nonaqueous RFBs.

Insights into the Redox Chemistry of Organosulfides Towards Stable Molecule Design in Nonaqueous Energy Storage Systems

AbstractNonaqueous redox flow batteries (RFBs) have great potential to achieve high‐energy storage systems. However, they have been limited by low solubility and poor stability of active materials. Here we demonstrate organosulfides as a new‐type model material system to explore the rational design of redox‐active molecules in nonaqueous systems. The tetraethylthiuram disulfide (TETD) molecule shows high solubility in various common organic solvents and achieves a high reversible capacity of ca. 50 Ah L−1 at a high concentration of 1 M. The resonance structures in the reduced product endow the molecule with high electrochemical stability in different organic electrolytes. The underlying mechanism in redox chemistry of organodisulfides involving the cleavage and reformation of disulfide bonds is revealed by material/structural characterizations. This study provides a new perspective of molecule designs for the development of redox‐active materials for high‐performance nonaqueous RFBs.

A controlled, highly effective and sustainable approach to the surface performance improvement of wool fibers

As part of the green concept, biorenewable deep eutectic solvent has emerged as an appealing type of ionic liquid and has shown their advance as environmentally benign sustainable alternative to the conventional solvents in the deep utilization of natural polymers, such as cellulose and lignin, which contributes to alleviating the pressure of the reduction of non-renewable resource. However, it has been few studies related to the value increase of another abundant natural polymer-protein material.As a representative, keratin fiber is a renewable biopolymer with excellent biocompatibility and biodegradability, but the poor surface performance results it is difficult to be functional modified, and the application is also limited in the textile industry. In this paper, the dissolution was controlled on the wool fiber surface using an eco-friendly and biorenewable deep eutectic solvent (DES). Surface dissolution is different from those used in previous studies and has been investigated in detail for the first time. The results show that a fast and facile surface dissolution process could be reached by incubating the wool fiber in DES for 10 min and the DES can be reused more than 10 times. Allwörden reaction, SEM and AFM images show that the controlled dissolution on the fiber surface was successfully accomplished. This process was also accompanied by the dissolution of amino acids and cleavage of disulfide bonds, which were ascertained using Raman spectroscopy, XPS and amino acid analysis. The protein macromolecular backbone and secondary structure of the surface-dissolved wool were not lost using FTIR spectroscopy, XRD and NMR spectroscopy. The modified wool by DES method has better surface properties; moreover, the method offers a more cost-effective and sustainable alternative for the modification of protein material.

55 Novel nanofibrous mats for effective delivery of sodium metabisulfite (SMBS) to the intestinal tract of pigs

Abstract Deoxynivalnol (DON) occurs on many commonly used cereal grains. DON levels as low as 0.6 to 2.0 ppm in complete feed cause a reduction in feed intake and growth rate, damage to the intestinal epithelial cells and increased susceptibility to enteric pathogen challenge. Sodium metabisulfite (SMBS) is a sulfite reducing agent commonly added to animal feeds to improve protein digestibility by cleaving disulfide bonds. SMBS can destroy 70%-100% of DON in processed grains or feeds in vitro with 0.45%-0.9% levels at pH around 6.5 but not at acidic conditions. Therefore, little SMBS will remain intact in the small intestine, where an optimal pH environment exists for SMBS to detoxify DON. Thus, the aim of this study is to encapsulate SMBS into nanofiber mats by an electrospinning technology to deliver intact SMBS to the lower gut such as the small intestine to detoxify DON effectively. Electrospinning was implemented to prepare nanofiberous mats from a suspension of particulate SMBS in the solution of a pH sensitive polymer (Eudragit L100-55). The highest loading capacity and loading efficiency of SMBS achieved in the nanofiberous mats were 32.00% and 80.01%, respectively. In vitro release studies showed that 12.23%-19.48% of encapsulated SMBS was released in the simulated gastric fluid (SGF) in 2 h and 66.01%-95.86% of SMBS release was observed in the simulated intestinal fluid (SIF) within 1 h. Additionally, in an in vitro DON detoxification experiment using IPEC-J2 cells, the ability of DON detoxification was reflected by significantly increasing the cell viability of DON and encapsulated SMBS nanofiber group (82.99%) compared with the cell viability of DON group (62.19%) (P < 0.05). For the first time, we demonstrate successful encapsulation of particulate SMBS in a nano-vehicle (electrospun nanofiber), achieve > 50% release of SMBS in SIF, and effective detoxification of DON in an in vitro cell assay.

SAXS studies of X-ray induced disulfide bond damage: Engineering high-resolution insight from a low-resolution technique.

A significant problem in biological X-ray crystallography is the radiation chemistry caused by the incident X-ray beam. This produces both global and site-specific damage. Site specific damage can misdirect the biological interpretation of the structural models produced. Cryo-cooling crystals has been successful in mitigating damage but not eliminating it altogether; however, cryo-cooling can be difficult in some cases and has also been shown to limit functionally relevant protein conformations. The doses used for X-ray crystallography are typically in the kilo-gray to mega-gray range. While disulfide bonds are among the most significantly affected species in proteins in the crystalline state at both cryogenic and higher temperatures, there is limited information on their response to low X-ray doses in solution, the details of which might inform biomedical applications of X-rays. In this work we engineered a protein that dimerizes through a susceptible disulfide bond to relate the radiation damage processes seen in cryo-cooled crystals to those closer to physiologic conditions. This approach enables a low-resolution technique, small angle X-ray scattering (SAXS), to detect and monitor a residue specific process. A dose dependent fragmentation of the engineered protein was seen that can be explained by a dimer to monomer transition through disulfide bond cleavage. This supports the crystallographically derived mechanism and demonstrates that results obtained crystallographically can be usefully extrapolated to physiologic conditions. Fragmentation was influenced by pH and the conformation of the dimer, providing information on mechanism and pointing to future routes for investigation and potential mitigation. The novel engineered protein approach to generate a large-scale change through a site-specific interaction represents a promising tool for advancing radiation damage studies under solution conditions.

Extracellular Protein Disulfide Isomerase Cleaves Allosteric Disulfides in Histidine-Rich Glycoprotein to Regulate Thrombus Formation

Introduction The fine-tuning of thrombus formation is influenced by multiple factors among which extracellular protein disulfide isomerase (PDI) released by activated platelets and endothelial cells plays critical roles. However, the precise mechanisms whereby PDI modulates the kinetics of thrombosis remain elusive. Using mechanism-based kinetic trapping strategy, we identified plasma histidine-rich glycoprotein (HRG) as a substrate of extracellular PDI during thrombus formation. HRG exerts both anticoagulant and procoagulant functions. On one hand, HRG inhibits the contact pathway by binding to activated factor XII (fXIIa); on the other hand, HRG attenuates the anticoagulant activity of antithrombin (AT) by competing with AT binding to endothelial heparan sulfate. Both functions are dependent on zinc ions. In this study, we characterized the effects of PDI-mediated disulfide bond cleavage on HRG functions in the context of thrombosis. Methods Recombinant PDI variant with the C-terminal catalytic Cys of the CGHC motif replaced with Ala (PDI-CA) was used to trap its redox substrates in platelet rich plasma (PRP). Dual fluorescent immunoblotting was utilized to detect the stabilized intermediate complex between PDI-CA and HRG. Differential cysteine alkylation and mass spectrometry was performed using purified plasma HRG to identify the disulfide bonds targeted by PDI. ELISA was performed to determine the effects of PDI treatment on HRG binding to heparin, an analog of endothelial heparan sulfate, and fXIIa. Cell-based ELISA, immunofluorescent imaging, and immunohistochemistry were employed to examine in vitro and in vivo binding of HRG and AT on endothelial cells. HRG-mediated inhibition of fXIIa activity was determined using the chromogenic substrate S-2302. The kinetics of HRG accumulation during thrombus formation were examined using high-speed intravital microscopy in the cremasteric arterioles. The effects of HRG on thrombus formation were examined in the laser injury thrombosis model in the presence (wild-type mice) or absence of fXII (f12-/- mice). Results The trapping mutant PDI-CA, but not variants of endoplasmic protein 57 (ERp57), a close member in the PDI family with similar domain structure, formed disulfide-linked complexes with HRG in PRP. Mass spectrometry showed that PDI cleaves three disulfide bonds, C306-C309, C390-C434 and C409-C410, in the histidine-rich region of HRG that is important for its binding to heparan sulfate and fXIIa. Compared to inert-PDI (PDI-AA), where both catalytic Cys were substituted with Ala, wild-type PDI (PDI-CC) increased HRG binding to heparin in a Zn2+-dependent manner. Plasma treated with PDI-CC had increased HRG binding but decreased AT binding to cultured endothelial cells compared to PDI-AA treated control. Further, PDI-CC increased HRG binding to fXIIa and enhanced its inhibitory effect on fXIIa activity. Following laser injury of cremaster arterioles, plasma HRG accumulates rapidly at the injury site preceding the main platelet signal. When mice were treated with Eptifibatide, an integrin αIIbβ3 antagonist that eliminates platelet deposition and Zn2+release, plasma HRG accumulation at the site of vessel injury was reduced, indicating a critical role of Zn2+ for HRG binding in vivo. Intravenous treatment with a PDI inhibitor, isoquercetin, also inhibited HRG accumulation in the growing thrombus. In addition, following FeCl3-induced carotid injury, PDI inhibition by isoquercetin was found to reduce HRG binding but sustain AT binding on the injured artery as determined by immunohistochemistry. Finally, knockdown of plasma HRG with vivo-siRNA in f12-/- mice attenuated thrombus formation compared to scramble siRNA treatment thus suggesting a procoagulant role of HRG independent of fXIIa. Conclusion PDI cleavage of allosteric disulfide bonds in HRG represents a novel regulatory mechanism that fine-tunes the kinetics of thrombus formation. Our results indicate that at the early stage of thrombosis, PDI promotes HRG binding to endothelial cells to suppress the anticoagulant activity of AT and allow the rapid initiation of thrombosis; at the later stage, PDI reduction of HRG enhances its binding to fXIIa leading to inhibition of fXIIa activity to prevent excessive clot formation. Disclosures Bowley: Pfizer: Current Employment.

N-acetylcysteine in clinical practice – properties, use and adverse effects

N-acetylcysteine is a simple chemical compound with antioxidant and mucolytic properties. Currently, it is the primary treatment for acetaminophen poisoning. Prior to the introduction of acetylcysteine, acetaminophen overdose was associated with high mortality due to acute liver failure. Owing to its antioxidant properties, acetylcysteine maintains appropriate levels of glutathione, thereby protecting the liver from damage by toxic metabolites of paracetamol. Acetylcysteine is also used for infections with excess respiratory secretions. The mechanism of action of cysteine derivatives involves cleavage of disulfide bonds between the macromolecules present in the mucus and, consequently, reduction of mucus viscosity. Clinical trials have shown that N-acetylcysteine also plays an important role in relieving cough by eliminating mucus from the airways. Owing to its antioxidant properties, it can also prevent contrast-induced nephropathy. It was shown that prophylactic doses of acetylcysteine administered the day before and at the day of contrast administration are effective in preventing contrastinduced nephropathy in patients with chronic kidney disease. The compound can also modulate pathophysiological processes involved in many mental and neurological disorders. There is also evidence supporting the efficacy of acetylcysteine in mental disorders such as autism, schizophrenia, Alzheimer’s disease, psychoactive substance dependence or bipolar disorder. However, in addition to its therapeutic activity, the drug may also induce adverse effects. Adverse effects of varying severity have been reported since the introduction of acetylcysteine into clinical use.

Effect of glutathione on wheat dough properties and bread quality

Reduced glutathione (GSH), released from lysed yeast cells, is well-known for weakening dough structure. However, its influence on bread texture and staling has not yet been completely elucidated. Herein, this study aims at assessing the effects of GSH on dough properties and bread quality, especially bread staling, using Rheofermentometer analysis, texture profile analysis (TPA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and low-field nuclear magnetic resonance (LF-NMR). The results revealed that GSH substantially decreased the dough height and gas-retention capacity during fermentation. The weakened dough structure was attributed to GSH-induced disulfide bond cleavage in gluten proteins and the depolymerization of glutenin polymers. The addition of 0.005%–0.01% GSH resulted in acceptable bread quality. However, bread supplemented with 0.015%–0.03% of GSH exhibited a coarser and more open crumb microstructure, as well as high level of hardness and low resilience during aging. GSH promoted crumb water loss and drove the water shift from the immobilized to the bound state. The DSC and XRD analyses further confirmed that GSH promoted starch retrogradation and recrystallization. These results suggest that apart from the gluten structure, GSH also altered gluten−starch interactions and water redistribution, ultimately decreasing bread quality and accelerating bread staling.

Reduction responsive BODIPY decorated mesoporous silica nanoscale platforms for photodynamic therapy

In this work, we decorated the surface hydroxyl of mesoporous silica nanoparticles (MSNs-OH) by using iodine BODIPY containing disulfide bond and carboxyl group (I2BDP–SS–COOH) for photodynamic therapy. To improve the water solubility, the MSNs were further PEGylated by PEG–SS–COOH to prepare MSNs-I2BDP-PEG. The particle size and stability of MSNs-I2BDP-PEG were characterized by the transmission electron microscopy (TEM) and dynamic light scattering (DLS). The confocal laser imaging and cells cytotoxicity experiments indicated that MSNs-I2BDP-PEG could be endocytosed well, and the intracellular higher concentrations of glutathione in tumor cells could stimulate the cleavage of disulfide bonds to release BODIPY for photodynamic therapy. This work highlights the great potential of post-modificating silica nanoparticles as multifunctional materials in biomedical fields.

Redox/NIR dual-responsive PEG-betulinic acid/pluronic-cypate prodrug micelles for chemophotothermal therapy

Betulinic acid (BA) is a new class of anticancer drug, but its relatively short half-life and poor water solubility limit its therapeutic effect and clinical application. Herein, to tackle the dilemma, BA prodrugs were prepared by conjugating BA onto the polyethylene glycol (PEG) polymer via cleavable disulfide bonds. The prodrugs exhibited high water solubility (270-fold of free BA) and a relatively high drug-loading efficiency of 14.2 %. To further endow the BA prodrugs with a photothermal therapeutic effect, the near-infrared (NIR) agent Cypate was grafted on the Pluronic triblock copolymer. The different PEG polymers and different Pluronic polymers were chosen to obtain the optimal drug loading efficiency and the photothermal generation effect. The P-SS-BA/F68-Cy prodrug micelles integrate the redox-responsive BA prodrugs and the NIR-responsive amphiphilic triblock polymer into one single nanocomposite. The release of BA was less than 20 % in pH 7.4 PBS in the absence of glutathione (GSH), whereas the release of BA was obviously accelerated in pH 5.0 PBS with 10 mM GSH. In addition, the release of BA was further accelerated under the NIR irradiation. The P-SS-BA/F68-Cy micelles showed an excellent photothermal heating effect under NIR irradiation. The prepared P-SS-BA/F68-Cy micelles showed the synergistic thermochemotherapeutic effect on tumors both in vitro and in vivo. Therefore, the present study shows the great potential of dual-triggered drug delivery and thermochemotherapy for combination therapy.

Comments on some chemical properties of diphenyl disulfide and its derivatives: II.Correlating the studies of reductive cleavage of disulfide bonds with the studies of anti‐human immunodeficiency virus activity with lowest unoccupied molecular orbital properties

AbstractThe higher anti‐human immunodeficiency virus activity of a symmetrical 2,2′‐disubstitued derivative of diphenyl disulfide (DPDS) has been explained by the lower energy of the lowest unoccupied molecular orbital (LUMO), resulted from a better hydrogen bond stabilization of the σ*SS bond orbital (BO). This conclusion entails the participation of σ*SS BO in constructing the LUMO. The higher content of σ*SS BO, compared to π*CC BOs of phenyl groups, in LUMO of DPDS has been found through analysis of the LUMO of DPDS expanded in the BO space. The high content of σ*SS BO (%σ*SS) in the LUMO of DPDS has laid the foundation for the formation of σ‐type radical anion intermediate in the stepwise reductive cleavage of disulfide bond in the symmetrical 4,4′‐disubstitued DPDS derivatives. For the nine 4,4′‐disubstituted DPDS‐derivatives under reductive cleavage studies, the increasing %σ*SS in the LUMOs is parallel to the increasing value of inner reorganization energy.