Disulfide Functionality Research Articles

Chaetocin disrupts the SUV39H1-HP1 interaction independent of SUV39H1 methyltransferase activity.

Chemical tools to control the activities and interactions of chromatin components have broad impact on our understanding of cellular and disease processes. It is important to accurately identify their molecular effects to inform clinical efforts and interpretations of scientific studies. Chaetocin is a widely used chemical that decreases H3K9 methylation in cells. It is frequently attributed as a specific inhibitor of the histone methyltransferase activities of SUV39H1/SU(VAR)3-9, although prior observations showed chaetocin likely inhibits methyltransferase activity through covalent mechanisms involving its epipolythiodixopiperazine disulfide 'warhead' functionality. The continued use of chaetocin in scientific studies may derive from the net effect of reduced H3K9 methylation, irrespective of a direct or indirect mechanism. However, there may be other molecular impacts of chaetocin on SUV39H1 besides inhibition of H3K9 methylation levels that could confound the interpretation of past and future experimental studies. Here, we test a new hypothesis that chaetocin may have an additional downstream impact aside from inhibition of methyltransferase activity. Using a combination of truncation mutants, a yeast two-hybrid system, and direct in vitro binding assays, we show that the human SUV39H1 chromodomain (CD) and HP1 chromoshadow domain (CSD) directly interact. Chaetocin inhibits this binding interaction through its disulfide functionality with some specificity by covalently binding with the CD of SUV39H1, whereas the histone H3-HP1 interaction is not inhibited. Given the key role of HP1 dimers in driving a feedback cascade to recruit SUV39H1 and to establish and stabilize constitutive heterochromatin, this additional molecular consequence of chaetocin should be broadly considered.

Instantaneous Degelling Thermoresponsive Hydrogel.

Responsive polymeric hydrogels have found wide application in the clinic as injectable, biocompatible, and biodegradable materials capable of controlled release of therapeutics. In this article, we introduce a thermoresponsive polymer hydrogel bearing covalent disulfide bonds. The cold aqueous polymer solution forms a hydrogel upon heating to physiological temperatures and undergoes slow degradation by hydrolytic cleavage of ester bonds. The disulfide functionality allows for immediate reductive cleavage of the redox-sensitive bond embedded within the polymer structure, affording the option of instantaneous hydrogel collapse. Poly(ethylene glycol)-b-poly(lactic acid)-S-S-poly(lactic acid)-b-poly(ethylene glycol) (PEG-PLA-SS-PLA-PEG) copolymer was synthesized by grafting PEG to PLA-SS-PLA via urethane linkages. The aqueous solution of the resultant copolymer was a free-flowing solution at ambient temperatures and formed a hydrogel above 32 °C. The immediate collapsibility of the hydrogel was displayed via reaction with NaBH4 as a relatively strong reducing agent, yet stability was displayed even in glutathione solution, in which the polymer degraded slowly by hydrolytic degradation. The polymeric hydrogel is capable of either long-term or immediate degradation and thus represents an attractive candidate as a biocompatible material for the controlled release of drugs.

Cover Feature: Rational Design of Programmable Monodisperse Semi‐Synthetic Protein Nanomaterials Containing Engineered Disulfide Functionality (ChemBioChem 20/2021)

Cover Feature: Rational Design of Programmable Monodisperse Semi‐Synthetic Protein Nanomaterials Containing Engineered Disulfide Functionality (ChemBioChem 20/2021)

Rational Design of Programmable Monodisperse Semi-Synthetic Protein Nanomaterials Containing Engineered Disulfide Functionality*.

The reversible nature of disulfide functionality has been exploited to design intelligent materials such as nanocapsules, micelles, vesicles, inorganic nanoparticles, peptide and nucleic acid nanodevices. Herein, we report a new chemical methodology for the construction redox-sensitive protein assemblies using monodisperse facially amphiphilic protein-dendron bioconjugates. The disulfide functionality is strategically placed between the dendron and protein domains. The custom designed bioconjugates self-assembled into nanoscopic objects of a defined size dictated by the nature of dendron domain. The stimuli-responsive behavior of the protein assemblies is demonstrated using a suitable redox trigger.

Dual‐Responsive Self‐Healable Carboxylated Acrylonitrile Butadiene Rubber Based on Dynamic Diels–Alder “Click Chemistry” and Disulfide Metathesis Reaction

AbstractIntroduction of the self‐healing property in the commercially available elastomers promotes the development of high‐end elastomeric products with an extended lifespan. Herein, a smart functionalized carboxylated nitrile rubber (XNBR) is prepared based on dynamic phototriggered disulfide metathesis and thermoreversible Diels–Alder (DA) “click chemistry.” In this case, the XNBR is functionalized with furfuryl amine (FA) followed by crosslinking with a dual functional crosslinker having a maleimide as well as a disulfide functionality for participating in the DA reaction and to induce the UV‐triggered disulfide metathesis reaction, respectively. The self‐healing properties are studied by thermal, mechanical, and microscopy analyses. The crosslinked materials present an impressive self‐healing efficiency of ≈88% and a tensile strength of ≈10 MPa without affecting its oil‐resistance property whereas pristine XNBR and furfuryl‐functionalized XNBR (FXNBR) show tensile strengths only 0.4 and 0.6 MPa, respectively. Furthermore, the crosslinked rubber is demonstrated to be recyclable, without much loss of its mechanical properties. In a nutshell, the use of this smart dual pathway of self‐healing can pave a new direction in sustainable development in NBR elastomers.

Polyethylene glycol-modified cystamine for fluorescent sensing

Tedious polymeric modifications, laborious syntheses, low water solubility, high cytotoxicity and low quantum yields are still the major concerns related to fluorescent materials used for biosensing applications. Here we report one-pot facile synthesis of polyethylene glycol (PEG)-modified cystamine-based multifunctional fluorescent dyes named as CPEG-168, CPEG-1000 and CPEG-2000, which can be used for biosensing and detection of both cations and anions in pure aqueous medium. Rapid response toward thiols could be achieved due to the presence of disulfide functionality and reversible redox property between thiol and disulfide. A cyclic structure is formed by (NH–H) intramolecular hydrogen bonding to produce electron dense region for strong fluorescence emission. The presence of –NH group made them sensitive toward Cu2+ ions, while excellent sensitivity toward pH and F− ions was provided by intramolecular hydrogen bonding between –NH groups. The increase in chain length of PEGs enhanced the fluorescence emission intensities due to the formation of more rigid structure, and hence, the desired quantum yields can be tuned by changing the chain length of PEG. The aforementioned properties along with high brightness in aqueous solution, at biological pH and temperature range, make these fluorescent dyes potential candidates for biosensing applications and detection of cations and anions.

Importance of crosslinking and disulfide bridge reduction for the mechanical properties of rigid wheat gluten bioplastics compression molded with thiol and/or disulfide functionalized additives

ABSTRACTThiol (SH) containing additives improve the mechanical properties of rigid, glassy gluten materials. However, the underlying molecular mechanism is still unclear. In particular, the importance of the preceding gluten‐additive mixing conditions remains to be investigated. Here, different additives containing either only SH, only disulfide or both SH and disulfide functionalities were synthesized and their impact on the gluten network using different mixing conditions prior to subsequent molding were assessed. All SH containing additives decreased the gluten molecular weight (MW) during mixing to a degree depending on the conditions. Additives with only disulfide functionality did not significantly affect protein size during mixing irrespective of the conditions used. Only when mixing induced sufficient MW reduction did the strength and failure strain of rigid gluten materials increase. This shows that factors other than the degree of cross‐linking affect the strength of rigid gluten materials. These results support our hypothesis that altered molecular conformations and improved molecular entanglements contribute to material strength. The extent to which such conformational changes occur may depend on the additive and the way of mixing. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41160.

Efficient Preparation of Novel Phenolic Surfactants for Self-Assembled Monolayers

Novel molecules have been synthesized that combine the phenolic nature of tannins and self-assembling properties of surfactants. These single-chain (C12) surfactants with potential biocompatibility have been synthesized with an ω-thiol or disulfide functionality, both commonly used anchors in self-assembly onto gold surfaces, using a modular route. Protecting groups for the phenol and thiol moieties played a key role for overcoming the challenges often associated with the purification of surfactants. The tasks of unmasking the thiol moiety and simultaneously deprotecting the acetyl protecting groups of the phenols were accomplished using sodium thiomethoxide. This modular route can be extended to synthesize other surfactants with the potential ability to form robust layers with biocompatible properties. [Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]

A Reversible Molecular Switch Based on the Biphenyl Structure

DFT calculations were performed on a biphenyl-based molecule bonded to gold nanoleads in order to evaluate its potential as a reversible molecular switch. The torsion angle (φ) between the aromatic rings may be controlled by means of reducing a disulfide functionality that bridges the two rings, giving rise to a “closed” species (disulfide bridge oxidized, φ ∼ 28°) and an “opened” species (disulfide bridge reduced, φ ∼ 65°). The mechanical properties of the nanojunction formed by this molecular species sandwiched between gold cluster pyramids mimicking metallic electrodes were determined. The thermodynamics of the reduction reaction was studied on the disulfide bridge as well as on the potentially competing anchoring sulfur atoms. A highly favorable product ratio toward the disulfide bridge reduction was found. Conductance values were calculated by means of non-equilibrium Green functions techniques. Interestingly, a significant difference between the closed (high conductance) and opened (low conductance)...

Fluorescein aldehyde with disulfide functionality as a fluorescence turn-on probe for cysteine and homocysteine in HEPES buffer

We developed a fluorescein aldehyde probe with disulfide functionality for the fluorescence detection of biologically important thiols. The probe displayed highly selective responses to cysteine (Cys) and homocysteine (Hcy) over glutathione (GSH) due to the rapid ring formation reaction of Cys and Hcy with the aldehyde group of the probe and the concomitant cleavage of the disulfide group followed by subsequent intramolecular cyclization. The fluorescent probe also exhibited a highly sensitive fluorescence turn-on response to Hcy with a detection limit of 2.4 μM Hcy in HEPES buffer.

Hyperbranched Polyethylenes Encapsulating Self-Supported Palladium(II) Species as Efficient and Recyclable Catalysts for Heck Reaction

We demonstrate in this paper a unique self-supporting strategy for the synthesis of hyperbranched polyethylenes (HBPEs) encapsulating Pd(II) species as efficient and recyclable catalysts for Heck reaction. This strategy combines remarkably the synthesis of HBPE polymer support and the immobilization of Pd(II) species in situ in one pot. It is achieved by chain walking copolymerization of ethylene with an acrylate comonomer (2) containing a disulfide functionality with a cationic Pd(II)–diimine catalyst (1). The copolymerization renders successfully HBPEs containing pendant disulfide groups at a controllable content, while with no poisoning effect from the disulfide functionality. Meanwhile, the Pd(II) catalyst in situ immobilizes itself onto the polymers by coordinative binding with the pendant disulfide groups, giving rise to the homogeneous self-supported Pd(II) catalysts. The resulting Pd-containing HBPEs having a low content of 2 (ca. < 1 mol %) have been found to be efficient and recyclable catalysts...

Surface modification of amorphous substrates by disulfide derivatives: A photo-assisted route to direct functionalization of chalcogenide glasses

A novel route for chalcogenide glass surface modification is disclosed. The formation of an organic monolayer from disulfide derivatives is studied on two different glasses of formula GexAsySez by water contact angle measurement, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy in attenuated total reflection mode (FTIR-ATR). The potential anchoring group is the disulfide functionality. Since thioctic acid derivatives absorb around 335nm, an irradiation step is included, in order to favor S–S disruption. Three types of disulfide compounds are grafted onto small glass breaks for contact angle and XPS analyses. The results show effective changes of surface state. According to contact angle measurement, the deposited organic layer functionalized by a small polyethylene glycol chain leads to a more hydrophilic surface, long alkyl chain or a perfluorinated carbon chain leads to a more hydrophobic surface. XPS shows the presence at the surface of an organic layer with sulfur and ethylene oxide chains, or augmentation of organic carbons or fluorine and CF bonds. The photo-assisted grafting of the disulfides onto an ATR prism made of chalcogenide glass shows that this surface modification process does not affect infrared transparency, despite UV treatment, and accurate structural analysis can be performed.

Copper‐Catalyzed Activation of Disulfides as a Key Step in the Synthesis of Benzothiazole Moieties

AbstractA convenient synthesis of substituted benzothiazoles has been accomplished by way of a copper catalyzed reaction of aromatic disulfide amines and aldehydes. The process, which involves copper catalyzed activation of disulfide functionality, proceeds in a tandem fashion via C–H bond activation, followed by aerobic oxidation of a resulting dihydrobenzothiazole intermediate. The scope and limitations of the reaction are demonstrated on a variety of substrates.

Redox Responsive Behavior of Thiol/Disulfide-Functionalized Star Polymers Synthesized via Atom Transfer Radical Polymerization

A poly(n-butyl acrylate)-based star polymer, polyEGDA-(polyBA)n, was synthesized by atom transfer radical polymerization using a modified core-first method. Further polymerization of a disulfide (SS) cross-linking agent bis(2-methacryloyloxyethyl) disulfide from the arm end produced a SS cross-linked star polymer. The disulfide functionality could be cleaved via reducing reactions, generating individual stars containing SH groups at the chain ends. The transformation between SS cross-linked star and SH-star was reversible via repetitive reduction and oxidation. Dynamic light scattering measurements showed that the average diameter of the cleaved star polymer was around 20 nm. The dynamic mechanical properties of these star copolymers were characterized through examination of the temperature dependencies of their shear moduli. The results showed that SS-functionalized star polymers respond to reduction−oxidation conditions, indicating that the disulfide bonds do cleave and re-form. These stimuli responsive star polymers have potential utility as intelligent polymeric materials such as self-healing materials.

The application of negative ion electrospray mass spectrometry for the sequencing of underivatized disulfide-containing proteins: insulin and lysozyme

Negative ion electrospray mass spectra of the peptides produced by tryptic and chymotrypsin digests of bovine insulin, and from the tryptic digest of lysozyme identify at least 80% of the sequences of these proteins. In particular, negative ion mass spectrometry identifies and positions disulfide moieties, and is the method of choice for identifying this post-translational modification in these two proteins. Intramolecular disulfide functionality is identified by the fragmentation [(M - H)(-)- H(2)S(2)](-) in a digest peptide, and CID of that fragment anion provides amino acid sequencing information. Digest peptides containing an intermolecular disulfide structure undergo facile and diagnostic cleavages. Each cleavage produces a peptide fragment from which CID MS/MS data provide sequencing information.

RAFT Polymer End-Group Modification and Chain Coupling/Conjugation Via Disulfide Bonds

End-group modification of polymers prepared by reversible addition–fragmentation chain transfer (RAFT) polymerization was accomplished by the conversion of trithiocarbonate or dithioester end-groups into a pyridyl disulfide (PDS) functionality. Several different polymers, such as poly(methyl methacrylate), polystyrene, poly(oligoethylene glycol-acrylate), poly(hydroxypropylacrylamide), and poly(N-isopropylacrylamide) were prepared by RAFT polymerization, and subjected to aminolysis in the presence of 2,2′-dithiodipyridine to yield thiol-terminated polymers with yields in the range 65–90% dependent on the polymer structure. Furthermore, this PDS end-group was utilized to generate higher-order architectures, such as diblock copolymers with high yields and selectively. In addition, the PDS end-groups were used for the bioconjugation of different biomolecules, such as oligonucleotides, carbohydrates, and peptides. The successful modification of well-defined polymers was confirmed by a combination of UV-vis, NMR spectroscopy, and gel permeation chromatography.

Ziram Causes Dopaminergic Cell Damage by Inhibiting E1 Ligase of the Proteasome

The etiology of Parkinson disease (PD) is unclear but may involve environmental toxins such as pesticides leading to dysfunction of the ubiquitin proteasome system (UPS). Here, we measured the relative toxicity of ziram (a UPS inhibitor) and analogs to dopaminergic neurons and examined the mechanism of cell death. UPS (26 S) activity was measured in cell lines after exposure to ziram and related compounds. Dimethyl- and diethyldithiocarbamates including ziram were potent UPS inhibitors. Primary ventral mesencephalic cultures were exposed to ziram, and cell toxicity was assessed by staining for tyrosine hydroxylase (TH) and NeuN antigen. Ziram caused a preferential damage to TH+ neurons and elevated alpha-synuclein levels but did not increase aggregate formation. Mechanistically, ziram altered UPS function through interfering with the targeting of substrates by inhibiting ubiquitin E1 ligase. Sodium dimethyldithiocarbamate administered to mice for 2 weeks resulted in persistent motor deficits and a mild reduction in striatal TH staining but no nigral cell loss. These results demonstrate that ziram causes selective dopaminergic cell damage in vitro by inhibiting an important degradative pathway implicated in the etiology of PD. Chronic exposure to widely used dithiocarbamate fungicides may contribute to the development of PD, and elucidation of its mechanism would identify a new potential therapeutic target.

Stability and utility of pyridyl disulfide functionality in RAFT and conventional radical polymerizations

AbstractTwo RAFT agents, suitable for inducing living radical polymerization in water, have been synthesized. Both RAFT agents were shown to be effective over the temperature range 25–70 °C. One RAFT agent was functionalized with a pyridyl disulfide group. RAFT efficacy was demonstrated for the polymerizations of N‐isopropyl acrylamide (NIPAAM) and poly(ethylene oxide)‐acrylate (PEG‐A) in both water and acetonitrile. The kinetic data indicates that the pyridyl disulfide functionality is largely benign in free radical polymerizations, remaining intact for subsequent reaction with thiol groups. This result was confirmed by studying conventional radical polymerizations in the presence of hydroxyethyl pyridyl disulfide. The utility of the pyridyl disulfide functionality at the terminus of the polymers was demonstrated by synthesizing polymer‐BSA conjugates. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7207–7224, 2008

Electrochemical switching of the flavoprotein dodecin at gold surfaces modified by flavin-DNA hybrid linkers

Dodecin from Halobacterium salinarum is a dodecameric, hollow-spherical protein, which unspecifically adopts flavin molecules. Reduction of flavin dodecin holocomplexes induces dissociation into apododecin and free flavin. Unspecific binding and dissociation upon reduction were used as key properties to construct an electrochemically switchable surface, which was able to bind and release dodecin apoprotein depending on the applied potential. A flavin modified electrode surface (electrode-DNA-flavin) was generated by direct adsorption of double stranded DNA (ds-DNA) equipped with flavin and disulfide modifications at opposite ends. While the disulfide functionality enabled anchoring the ds-DNA at the gold surface, the flavin exposed at the surface served as the redox-active dodecin docking site. The structures of protein and flavin-DNA hybrid ligands were optimized and characterized by x-ray structural analysis of the holocomplexes. By surface plasmon resonance (SPR) spectroscopy, the adsorption of flavin modified DNA as well as the binding and the electrochemically induced release of dodecin apoprotein could be shown. When the surface immobilization protocol was changed from direct immobilization of the modified ds-DNA to a protocol, which included the hybridization of flavin and thiol modified DNA at the surface, the resulting monolayer was electrochemically inactive. A possible explanation for the strong influence of the surface immobilization protocol on addressing dodecin by the applied potential is that electron transfer is rather mediated by defects in the monolayer than modified ds-DNA.

Determination of Disulfide Functionality in Underivatised Peptides Using Negative Ion Mass Spectrometry: An Aid to Structure Determination

Determination of Disulfide Functionality in Underivatised Peptides Using Negative Ion Mass Spectrometry: An Aid to Structure Determination