Cleavage Of Disulfide Bonds Research Articles

A Physiologically Responsive Nanocomposite Hydrogel for Treatment of Head and Neck Squamous Cell Carcinoma via Proteolysis-Targeting Chimeras Enhanced Immunotherapy.

Although immunotherapy has revolutionized oncotherapy, only ≈15% of head and neck squamous cell carcinoma (HNSCC) patients benefit from the current therapies. An immunosuppressive tumor microenvironment (TME) and dysregulation of the polycomb ring finger oncogene BMI1 are potential reasons for the failure. Herein, to promote immunotherapeutic efficacy against HNSCC, an injectable nanocomposite hydrogel is developed with a polymer framework (PLGA-PEG-PLGA) that is loaded with both imiquimod encapsulated CaCO3 nanoparticles (RC) and cancer cell membrane (CCM)-coated mesoporous silica nanoparticles containing a peptide-based proteolysis-targeting chimeras (PROTAC) for BMI1 and paclitaxel (PepM@PacC). Upon injection, this nanocomposite hydrogel undergoes in situ gelation, after which it degrades in the TME over time, releasing RC and PepM@PacC nanoparticles to respectively perform immunotherapy and chemotherapy. Specifically, the RC particles selectively manipulate tumor-associated macrophages and dendritic cells to activate a T-cell immune response, while CCM-mediated homologous targeting and endocytosis delivers the PepM@PacC particles into cancer cells, where endogenous glutathione promotes disulfide bond cleavage to release the PROTAC peptide for BMI1 degradation and frees the paclitaxel from the particle pores to elicit apoptosis meanwhile enhance immunotherapy. Thus, the nanocomposite hydrogel, which is designed to exploit multiple known vulnerabilities of HNSCC, succeeds in suppressing both growth and metastasis of HNSCC.

A dandelion-like nanomedicine via hierarchical self-assembly for synergistic chemotherapy and photo-dynamic cancer therapy

The synergistic effect of chemotherapy and photo-dynamic therapy (PDT) is an effective way to improve the efficiency of tumor treatment. However, most synergistic therapeutic drugs have poor water solubility and stability, so it is difficult to achieve high therapeutic effects while avoiding the severe side effects. Herein, a unique dandelion-like nanomedicine (named as cRGDfk-CCPT-mCe6) was successfully synthesized using Ce6-loaded amphiphilic β-cyclodextrins (β-CD) doped lipid-based vesicles as the core (receptacle) and β-CD modified camptothecin (CPT) pro-drug as the flyable dandelion seeds. The β-CD modified CPT pro-drug was introduced into the core vesicles in succession via host-guest interaction between inter-molecular β-CD and CPT, and cRGDfk peptides were further introduced as the outermost layer (stigma) to enhance the internalization into cancer cells. CPT interacted with β-CD through glutathione (GSH)-cleavable disulfide bonds, which led to drug release in glutathione-rich cancer cells, just as spread of dandelion seeds in the wind. GSH consumption further disrupted the intracellular redox homeostasis of cancer cells through combined action of Ce6 with light irradiation and the synergistic anti-tumor effect was thus achieved, resulting in apoptosis of cancer cells. Therefore, the nanomedicine provides a facile and versatile anti-tumor strategy, as well as a persistent anti-cancer effects.

Magnetically Driven Self-Degrading Zinc-Containing Cystine Microrobots for Treatment of Prostate Cancer.

Prostate cancer is the most commonly diagnosed tumor disease in men, and its treatment is still a big challenge in standard oncology therapy. Magnetically actuated microrobots represent the most promising technology in modern nanomedicine, offering the advantage of wireless guidance, effective cell penetration, and non-invasive actuation. Here, new biodegradable magnetically actuated zinc/cystine-based microrobots for in situ treatment of prostate cancer cells are reported. The microrobots are fabricated via metal-ion-mediated self-assembly of the amino acid cystine encapsulating superparamagnetic Fe3 O4 nanoparticles (NPs) during the synthesis, which allows their precise manipulation by a rotating magnetic field. Inside the cells, the typical enzymatic reducing environment favors the disassembly of the aminoacidic chemical structure due to the cleavage of cystine disulfide bonds and disruption of non-covalent interactions with the metal ions, as demonstrated by in vitro experiments with reduced nicotinamide adenine dinucleotide (NADH). In this way, the cystine microrobots served for site-specific delivery of Zn2+ ions responsible for tumor cell killing via a "Trojan horse effect". This work presents a new concept of cell internalization exploiting robotic systems' self-degradation, proposing a step forward in non-invasive cancer therapy.

Thiol-reactive Pyrene Dimer Having A Disulfide Linkage as A Ratiometric Fluorescence Probe to Thiol-containing Biomolecules

A disulfide-linked pyrene dimer (1), which was constructed with two pyrene derivatives and a cystine-derived disulfide linker, was synthesized as a thiol-reactive ratiometric fluorescence probe. 1 alone showed strong excimer fluorescence at around 490 nm in an aqueous dimethyl sulfoxide solution. Upon addition of thiol-containing biomolecules such as l-cysteine, l-homocysteine, and glutathione, the excimer fluorescence of 1 decreased, while monomeric fluorescence increased, reflecting reduction-responsive cleavage of disulfide bond of 1 to give the corresponding thiol 2.

Accumulation of Four Electrons on a Terphenyl (Bis)disulfide.

The activation of N2 , CO2 or H2 O to energy-rich products relies on multi-electron transfer reactions, and consequently it seems desirable to understand the basics of light-driven accumulation of multiple redox equivalents. Most of the previously reported molecular acceptors merely allow the storage of up to two electrons. We report on a terphenyl compound including two disulfide bridges, which undergoes four-electron reduction in two separate electrochemical steps, aided by a combination of potential compression and inversion. Under visible-light irradiation using the organic super-electron donor tetrakis(dimethylamino)ethylene, a cascade of light-induced reaction steps is observed, leading to the cleavage of both disulfide bonds. Whereas one of them undergoes extrusion of sulfur to result in a thiophene, the other disulfide is converted to a dithiolate. These insights seem relevant to enhance the current fundamental understanding of photochemical energy storage.

Targeted co-delivery of a photosensitizer and an antisense oligonucleotide based on an activatable hyaluronic acid nanosystem with endogenous oxygen generation for enhanced photodynamic therapy of hypoxic tumors

Photodynamic therapy (PDT) is a promising cancer treatment modality with advantages of minimal invasiveness, repeatable therapy, and mild systemic toxicity. However, the limited bioavailability of photosensitizer (PS), tumor hypoxia, and the presence of antiapoptotic proteins in cancer cells, has hampered the efficiency of PDT. To address these limitations, herein, we developed a hyaluronic acid (HA) based nanosystem (HA-Ce6-Hemin@DNA-Protamine NPs, HCH@DP) loaded with chlorin e6 (Ce6, as PS), hemin (as mimetic catalase) and antisense oligonucleotide (ASO) of B-cell lymphoma 2 (Bcl-2) anti-apoptosis protein via a simple electrostatic self-assembly method for enhanced PDT of hypoxic solid tumors. The HCH@DP can target deliver the PS and ASO to tumor cells via cancer cell overexpressed HA receptors (i.e., CD44 or RHAMM). The Ce6 was released from HA-ss-Ce6 (HSC conjugates) after the reaction of cleavable disulfide bond with glutathione (GSH), which recovered the fluorescence and phototoxicity of Ce6 upon laser irradiation. Meanwhile, the catalase-mimicking hemin (degradation of HA-eda-hemin by hyaluronidase) decomposed the tumor overdressed endogenous H2O2 to oxygen, which relieved tumor hypoxia and further overcome hypoxia-associated resistance of PDT. Furthermore, the inhibition of Bcl-2 expression by Bcl-2 ASO also greatly improved the cellular sensitivity to PDT. Both in vitro and in vivo results showed the tumor cell targeting ability, hypoxia relief and significantly enhanced antitumor PDT efficacy of HCH@DP for hypoxic tumor cells upon laser irradiation. Thus, by improving the target delivery of PS and ASO, relieving tumor hypoxia, and down-regulation of anti-apoptotic proteins, this HCH@DP nanosystem achieved enhanced PDT efficiency against hypoxic tumors. In general, our work provided a promising strategy to increase the utilization of key components (PS and oxygen) of PDT and the cell sensitivity to PDT by targeting co-delivery PS and oligonucleotides to tumor cells via a biocompatible HA based carrier, thereby achieving efficiently PDT treatment of hypoxic solid tumors with potential translation possibility. Statement of significanceThe efficiency of PDT against solid tumor is severely restricted by the limited bioavailability of photosensitizer, tumor hypoxia, and the presence of antiapoptotic proteins in cancer cells. Herein, we have developed an activatable hyaluronic acid (HA) based nanosystem (HA-Ce6-Hemin@DNA-Protamine NPs, HCH@DP) via a simple electrostatic self-assembly method for PDT treatment of hypoxic solid tumors. The HCH@DP enabled to target co-delivery of photosensitizer and antisense oligonucleotide to tumor cells, overcoming tumor hypoxia through in situ oxygen production and improving cellular sensitivity by efficiently reducing anti-apoptosis effect of cancer cells for synergistically enhancing PDT efficiency. This work suggests a promising strategy to develop small molecule drug and oligonucleotides co-delivery nanoplatforms for efficiently PDT treatment of hypoxic solid tumor.

Development of Surface Chemical Strategies for Synthesizing Redox-Responsive Diatomite Nanoparticles as a Green Platform for On-Demand Intracellular Release of an Antisense Peptide Nucleic Acid Anticancer Agent.

Redox-responsive silica drug delivery systems are synthesized by aeco-friendly diatomite source to achieve on-demand release of peptide nucleic acid (PNA) in tumor reducing microenvironment, aiming to inhibit the immune checkpoint programmed cell death 1 receptor/programmed cell death receptor ligand 1 (PD-1/PD-L1) in cancer cells. The nanoparticles (NPs) are coated with polyethylene glycol chains as gatekeepers to improve their physicochemical properties and control drug release through the cleavable disulfide bonds (S-S) in a reductive environment. This study describes different chemical conditions to achieve the highest NPs' surface functionalization yield, exploring both multistep and one-pot chemical functionalization strategies. The best formulation is used for covalent PNA conjugation via the S-S bond reaching a loading degree of 306 ± 25µg PNA mg-1 DNPs . These systems are used for in vitro studies to evaluate the kinetic release, biocompatibility, cellular uptake, and activity on different cancer cells expressing high levels of PD-L1. The obtained results prove the safety of the NPs up to 200µg mL-1 and their advantage for controlling and enhancing the PNA intracellular release as well as antitumor activity. Moreover, the downregulation of PD-L1 observed only with MDA-MB-231 cancer cells paves the way for targeted immunotherapy.

Tailored nanoplatforms with detachable ‘meteorolite’ for photothermal-enhanced programmed tumor therapy

The premature drug release, multidrug resistance, and limited tumor penetration ability have vastly weakened the chemotherapy effect. To surmount this dilemma, iRGD modified red-light emitting carbon dots (CDR) were gated on paclitaxel (PTX) loaded hollow mesoporous carbon (HMC) via cleavable disulfide bonds for photothermal-enhanced programmed tumor therapy. The HMC vehicles were designed based on their high photothermal conversion efficiency and tailored mesoporous structure with considerable drug loading capacity. The fluorescent CDR worked as the smart gatekeepers to prevent premature release, photothermal agents to enhance the photothermal effect of HMC, and the fluorescent agent to visualize the delivery process. The modification of iRGD peptide could promote the targeting and penetration capacities of PTX/HMC-CD-iRGD. The tailored nanoplatforms could promptly divide into (1) unlocked PTX/HMC for synergistic thermo-chemotherapy on the surface of tumor cells, and (2) abundant CDR-iRGD as detachable ‘meteorolite’ with enhanced penetration ability to realize photothermal ablation at the deep-seated tumor. PTX/HMC-CD-iRGD showed outstanding synergistic cells killing efficiency of chemotherapy and photothermal therapy at different depths, exhibiting great potential in clinical application.

Rational assembly of RGD/MoS2/Doxorubicin nanodrug for targeted drug delivery, GSH-stimulus release and chemo-photothermal synergistic antitumor activity.

Herein, we present the facile design and construction of a nanodrug system integrating targeted drug delivery and synergistic chemo-photothermal antitumor activity. MoS2 nanosheets were synthesized and modified by ανβ3 integrin binding peptide (Arg-Gly-Asp, RGD) using lipoic acid functionalized polyethylene glycol (LA-PEG-COOH), forming a well dispersed and targeted delivery nanocarrier. Further, covalent coupling of antitumor drug, thiolated doxorubicin (DOX) via disulfide linkage resulted in a novel nanodrug, RGD/MoS2/DOX. The prepared nanocarrier showed favorable stability, biocompatibility and photothermal conversion efficiency. Fluorescence imaging revealed that Hela cells could endocytose far more nanodrug than H9c2 normal myocardial cells due to the targeted delivery characteristic. Particularly, GSH-induced disulfide bond cleavage facilitated the effective release of DOX from the nanodrug in the tumor microenvironment. The survival rate of Hela cells incubated with the nanodrug for 48h was 22.2±1.2%, which dramatically reduced to 8.9±1.4% in combination with 808nm NIR irradiation, demonstrating powerful photothermal induced tumor-killing efficacy. In contrast, the survival rates of H9c2 cells treated by the nanodrug and free DOX were 68.5±2.6% and 6.7±2.6%, respectively, an indication of the notably alleviated cardiotoxicity of the designed nanodrug. The cell apoptosis experiment further verified the synergistic chemo-photothermal effect, thus paving a way toward design of high-efficiency and low-toxicity antitumor nanodrug.

Structure-biological activity relationships of myeloperoxidase to effect on platelet activation

Myeloperoxidase (MPO), an oxidant-producing enzyme of neutrophils, has been shown to prime platelet activity promoting immunothrombosis. Native MPO is a homodimer, consisting of two identical protomers (monomer) connected by a single disulfide bond. But in inflammatory foci, MPO can be found both in the form of a monomer and in the form of a dimer. Beside MPO can also be in complexes with other molecules and be modified by oxidants, which ultimately affect its physicochemical properties and functions. Here we compared the effects of various forms of MPO as well as MPO in complex with ceruloplasmin (CP), a physiological inhibitor of MPO, on the platelet activity. Monomeric MPO (hemi-MPO) was obtained by treating the dimeric MPO by reductive alkylation. MPO was modified with HOCl in a molar ratio of 1:100 (MPO-HOCl). Using surface-enhanced Raman scattering (SERS) spectroscopy we showed that peaks at about 510 and 526 cm−1 corresponded to disulfide bond was recognizable in the SERS-spectra of dimeric MPO, absent in the spectrum of hemi-MPO and less intense in the spectra of MPO-HOCl, which indicates the partial decomposition of dimeric MPO with a disulfide bond cleavage under the HOCl modification. It was shown hemi-MPO to a lesser extent than dimeric MPO bound to platelets and enhanced their agonist-induced aggregation and platelet-neutrophil aggregate formation. MPO modified by HOCl and MPO in complex with CP did not bind to platelets and have no effect on platelet activity. Thus, the modification of MPO by HOCl, its presence in monomeric form as well as in complex with CP reduces MPO effect on platelet function and consequently decreases the risk of thrombosis in inflammatory foci.

SOD1 gains pro-oxidant activity upon aberrant oligomerization: change in enzymatic activity by intramolecular disulfide bond cleavage

Copper-zinc superoxide dismutase (SOD1) has been proposed as one of the causative proteins of amyotrophic lateral sclerosis (ALS). The accumulation of non-native conformers, oligomers, and aggregates of SOD1 in motor neurons is considered responsible for this disease. However, it remains unclear which specific feature of these species induces the onset of ALS. In this study, we showed that disulfide-linked oligomers of denatured SOD1 exhibit pro-oxidant activity. Substituting all the cysteine residues in the free thiol state with serine resulted in the loss of both the propensity to oligomerize and the increase in pro-oxidant activity after denaturation. In contrast, these cysteine mutants oligomerized and acquired the pro-oxidant activity after denaturation in the presence of a reductant that cleaves the intramolecular disulfide bond. These results indicate that one of the toxicities of SOD1 oligomers is the pro-oxidant activity induced by scrambling of the disulfide bonds. Small oligomers such as dimers and trimers exhibit stronger pro-oxidant activity than large oligomers and aggregates, consistent with the trend of the cytotoxicity of oligomers and aggregates reported in previous studies. We propose that the cleavage of the intramolecular disulfide bond accompanied by the oligomerization reduces the substrate specificity of SOD1, leading to the non-native enzymatic activity.

Investigation of Product Ions Generated by 193 nm Ultraviolet Photodissociation of Peptides and Proteins Containing Disulfide Bonds.

Disulfide bridges are unique post-translational modifications (PTM) that contribute to protein architecture and modulate function. This PTM, however, challenges top-down mass spectrometry by cyclizing stretches of the protein sequence. In order to produce and release detectable product ions that contribute to the assignment of proteoforms, regions of a protein encapsulated by disulfide bonds require two fragmentation events: cleavage of the protein backbone and cleavage of the disulfide bond. Traditional collisional activation methods do not cleave disulfide bonds efficiently, often leading to low sequence coverage of proteins that incorporate this feature. To address this challenge, we have evaluated the fragmentation pathways enabled by 193 nm ultraviolet photodissociation (UVPD) and UVPD coupled to electron transfer dissociation for the characterization of protein structures incorporating disulfide bonds. Cleavage of disulfide bonds by either approach results in S-S and C-S dissociation products that result from a combination of homolytic cleavage and hydrogen-transfer processes. Characterization of these product ions elevates interpretation of complex top-down spectra of proteins that incorporate disulfide bonds.

A dual-responsive hyaluronic acid nanocomposite hydrogel drug delivery system for overcoming multiple drug resistance

Chemotherapy is restricted by efficient drug outflow due to the multiple drug resistance (MDR) in heterogenous nature of tumor. Herein, we present a dual-responsive hyaluronic acid (HA) nanocomposite hydrogel that can not only response to the tumor microenvironment but also enhance chemotherapy. This HA hydrogel consists of a core-shell SiO2 (GOD@SiO2-Arg) and mesoporous silica nanoparticles (MSNs) with doxorubicin (DOX) as the cargo (DOX@MSN). It could rapidly release the GOD@SiO2-Arg nanoparticles at the low pH tumor-specific environment due to the cleavage of imine bond. GOD@SiO2-Arg activated by over-expressed glutathione (GSH) in tumor cells releases GOD due to the cleavage of disulfide bonds, which could oxidize glucose to produce hydrogen peroxide (H2O2) for in situ NO generation via reaction between Arg and H2O2. The validity of this study might provide a method to modulate the tumor microenvironment for enhancing chemotherapy.

An efficient ultrasonic-assisted bleaching strategy customized for yak hair triggered by melanin-targeted Fenton reaction

Promoting processing efficiency and taking advantage of agricultural by-products are two promising ways to achieve sustainable textile industry. This study presents a customized efficient ultrasonic-assisted bleaching strategy for yak hair – a widely existing but underexploited secondary dark shade fibre from yak. A melanin-targeted Fenton oxidation process is established which involves three phases, i.e., (I) incorporation of Fe2+ ions with melanin, (II) catalytic oxidative bleaching using hydrogen peroxide (H2O2), and (III) reductive cleansing. The bleaching efficacy, dyeing performance and tensile property of yak hair treated with and without ultrasound were explored and compared. Further, the ultrasonic bleaching mechanism in terms of the catalytic effect of Fe2+ ions, the promotion of H2O2 decomposition, removal of melanin granule from yak hair, were demonstrated. Finally, the main effects and interactions of parameters in phase II, and optimal condition were obtained through mathematical modelling based on a central composite design (CCD). Results reveal that ultrasonic bleaching dramatically enhances the whiteness index (WI) of yak hair from 11 to 45 which is 44.6% higher than those bleached without ultrasound, and also promotes the uptake of acid dyes. There is only 15% tensile strength loss and 14% elongation increment of yak hair after ultrasonic bleaching, rising from a slight damage of cuticle layer and cleavage of disulfide bonds, respectively. In the study of bleaching mechanism, Fe2+ ion is confirmed to improve the H2O2 decomposition rate by 20.9% which further runs up to 35.9% after introducing ultrasound. Ultrasound increases the concentration of hydroxyl radicals (HO) by 94% which are the main oxidative species participating in bleaching confirmed by HO scavenging experiment. The porous structure was observed on the cross section of yak hair stemming from the removal of melanin granules contributed by the cleaning action of ultrasound. A theoretical highest WI of 52.4 can be achieved under an optimal condition based on the CCD study. In general, the proposed melanin-targeted bleaching strategy for yak hair that integrates ultrasonic technology and Fenton reaction, is beneficial to the development of sustainable textile industry from material and processing perspectives.

Novel octanuclear copper(I) clusters [Cu8{(N)-(μ4-S)}4(μ3-I)2I2(PPh3)2] produced via reductive S-S bond cleavage of disulfide Schiff base ligands and their use as efficient heterogeneous catalysts in CuAAC click reaction

Thiol/disulfide interconversion, catalyzed by metal ions and enzymes, is a fundamental transformation and plays important roles in biological systems. The thiolates, produced in these reactions, are particularly versatile sulfur-containing ligands that can bind to metals or group of metals via a variety of modes and this versatility can lead to the formation of polymeric chains and metal clusters with high nuclearity. Herein, we report the facile one pot synthesis of novel octanuclear copper(I) complexes, [Cu8{(N)-(μ4-S)}4(μ3-I)2I2(PPh3)2] (1–5), by the reaction of copper(I) iodide and disulfide Schiff base molecules (R-CHN˗Ph˗S˗S˗Ph-NCH-R, RMePh = 4-MePh (SB1), RMeOPh = 4-MeOPh (SB2), RMeSPh = 4-MeSPh (SB3), RBrPh = 4-BrPh (SB4), and RFur = 2-furan (SB5)) in the presence of PPh3 in dichloromethane-acetonitrile or chloroform-acetonitrile solution under ambient conditions. Single-crystal X-ray structure analyses of these clusters confirm the presence of Cu8S4I4 core stabilized by the chelating Schiff base thiolate fragment R-CHN˗Ph˗Sˉ produced by the reductive cleavage of disulfide bond, Iˉ, and PPh3. DFT calculations have been performed to describe a speculative mechanism of cluster formation. The octanuclear clusters [Cu8{(N)-(μ4-S)}4(μ3-I)2I2(PPh3)2] (1–5) have been exploited as efficient heterogeneous catalysts for the green synthesis of 1,2,3-triazoles from NaN3, alkyl halides, and alkyne derivatives (CuAAC reaction) under mild conditions.

Construction of disulfide containing redox-responsive polymeric nanomedicine.

Disulfide bonds (S-S) are widely found in chemistry, biology, and materials science. Polymer nanomaterials containing disulfide bonds with a variety of excellent properties have great potential as drug and gene delivery carriers. The disulfide bond can exist stably in extracellular environment, but upon entering cancer cells, it will undergo a sulfhydryl-disulfide bond exchange reaction with glutathione (GSH) in the cytoplasm, causing the disulfide bond cleavage. Therefore, polymeric nanomaterials containing disulfide bonds are promising in cancer treatment due to the elevated GSH concentration inside cancer cells. This review highlights various synthetic approaches to prepare disulfide containing redox-responsive polymeric nanomedicine, including synthesis of disulfide bonds containing polymers, construction of polymeric nanoparticle with shell or core crosslinked disulfide bonds, preparation of polymer-drug conjugates via disulfide linkers, and disulfide linked responsive payloads.

Reversible Protein Capture and Release by Redox-Responsive Hydrogel in Microfluidics.

Stimuli-responsive hydrogels have a wide range of potential applications in microfluidics, which has drawn great attention. Double cross-linked hydrogels are very well suited for this application as they offer both stability and the required responsive behavior. Here, we report the integration of poly(N-isopropylacrylamide) (PNiPAAm) hydrogel with a permanent cross-linker (N,N′-methylenebisacrylamide, BIS) and a redox responsive reversible cross-linker (N,N′-bis(acryloyl)cystamine, BAC) into a microfluidic device through photopolymerization. Cleavage and re-formation of disulfide bonds introduced by BAC changed the cross-linking densities of the hydrogel dots, making them swell or shrink. Rheological measurements allowed for selecting hydrogels that withstand long-term shear forces present in microfluidic devices under continuous flow. Once implemented, the thiol-disulfide exchange allowed the hydrogel dots to successfully capture and release the protein bovine serum albumin (BSA). BSA was labeled with rhodamine B and functionalized with 2-(2-pyridyldithio)-ethylamine (PDA) to introduce disulfide bonds. The reversible capture and release of the protein reached an efficiency of 83.6% in release rate and could be repeated over 3 cycles within the microfluidic device. These results demonstrate that our redox-responsive hydrogel dots enable the dynamic capture and release of various different functionalized (macro)molecules (e.g., proteins and drugs) and have a great potential to be integrated into a lab-on-a-chip device for detection and/or delivery.

Second-Order Derivation Fourier Transform Infrared Spectral Analysis of Regenerated Wool Keratin Structural Changes

Keratin is a natural biopolymer with excellent biocompatibility and biodegradability properties. It is widely used in biomaterial construction. The secondary structure of keratin is essential in its applications. This structure is associated with its regeneration. In this study, the structure of regenerated keratin from wool was analyzed using the amide I, II, and III bands from second-order derivation Fourier transform infrared spectroscopy. The results showed that the regenerated wool keratin retained its molecular backbone with the cleavage of disulfide bonds. The amide I and II bands indicated that the content ratio of α-helix to non-α-helix structure was less in the regenerated keratin than that of raw wool. The amide III band confirmed the contents of α-helix/β-sheet/β-turn/random coil for raw wool (35%/31%/22%/13%) and regenerated keratin (26%/35%/23%/15%).

Cysteine-based protein folding modulators for trapping intermediates and misfolded forms.

Folding is a key process to form functional conformations of proteins. Folding via on-pathway intermediates leads to the formation of native structures, while folding through off-pathways affords non-native and disease-causing forms. Trapping folding intermediates and misfolded forms is important for investigating folding mechanisms and disease-related biological properties of the misfolded proteins. We developed cysteine-containing dipeptides conjugated with amino acids possessing mono- and diamino-groups. In oxidative protein folding involving disulfide-bond formation, the addition of cysteine and oxidized glutathione readily promoted the folding to afford native forms. In contrast, despite the acceleration of disulfide-bond formation, non-native isomers formed in significantly increased yields upon the addition of the dipeptides. This study provides a molecular design of cysteine-based protein-folding modulators that afford proteins adopting non-native conformations through intermolecular disulfide-bond formation. Because of the intrinsic reversibility of the disulfide bonds upon redox reactions, the disulfide bond-based approach demonstrated here is expected to lead to the development of reversible methodologies for trapping transient and misfolded forms by intermolecular disulfide bond formation and restarting the folding processes of the trapped forms by subsequent cleavage of the intermolecular disulfide bonds.

Modulating defibrillation by tryptophan-mediated photo cleavage of disulfide bonds

Dibenzyloxycarbonyl-l-cystine forms amyloid-like fibers and a hydrogel; however, on UV irradiation, Trp-mediated disulfide bond cleavage occurs, leading to defibrillation and a gel to sol transition.