Thiol Molecules Research Articles

Performance comparison of acrylic and thiol-acrylic resins in two-photon polymerization.

Microfabrication by two-photon polymerization is investigated using resins based on thiol-ene chemistry. In particular, resins containing different amounts of a tetrafunctional acrylic monomer and a tetrafunctional thiol molecule are used to create complex microstructures. We observe the enhancement of several characteristics of two-photon polymerization when using thiol-acrylic resins. Specifically, microfabrication is carried out using higher writing velocities and it produces stronger polymeric microstructures. Furthermore, the amount of shrinkage typically observed in the production of three-dimensional microstructures is reduced also. By means of microspectrometry, we confirm that the thiol-acrylate mixture in TPP resins promote monomer conversion inducing a higher degree of cross-linked network formation.

Structural Engineering of Nanoporous Anodic Alumina Photonic Crystals by Sawtooth-like Pulse Anodization.

This study presents a sawtooth-like pulse anodization approach aiming to create a new type of photonic crystal structure based on nanoporous anodic alumina. This nanofabrication approach enables the engineering of the effective medium of nanoporous anodic alumina in a sawtooth-like manner with precision. The manipulation of various anodization parameters such as anodization period, anodization amplitude, number of anodization pulses, ramp ratio and pore widening time allows a precise control and fine-tuning of the optical properties (i.e., characteristic transmission peaks and interferometric colors) exhibited by nanoporous anodic alumina photonic crystals (NAA-PCs). The effect of these anodization parameters on the photonic properties of NAA-PCs is systematically evaluated for the establishment of a fabrication methodology toward NAA-PCs with tunable optical properties. The effective medium of the resulting NAA-PCs is demonstrated to be optimal for the development of optical sensing platforms in combination with reflectometric interference spectroscopy (RIfS). This application is demonstrated by monitoring in real-time the formation of monolayers of thiol molecules (11-mercaptoundecanoic acid) on the surface of gold-coated NAA-PCs. The obtained results reveal that the adsorption mechanism between thiol molecules and gold-coated NAA-PCs follows a Langmuir isotherm model, indicating a monolayer sorption mechanism.

Photoactivatable protein labeling by singlet oxygen mediated reactions

Protein–protein interactions regulate many biological processes. Identification of interacting proteins is thus an important step toward molecular understanding of cell signaling. The aim of this study was to investigate the use of photo-generated singlet oxygen and a small molecule for proximity labeling of interacting proteins in cellular environment. The protein of interest (POI) was fused with a small singlet oxygen photosensitizer (miniSOG), which generates singlet oxygen (1O2) upon irradiation. The locally generated singlet oxygen then activated a biotin-conjugated thiol molecule to form a covalent bond with the proteins nearby. The labeled proteins can then be separated and subsequently identified by mass spectrometry. To demonstrate the applicability of this labeling technology, we fused the miniSOG to Skp2, an F-box protein of the SCF ubiquitin ligase, and expressed the fusion protein in mammalian cells and identified that the surface cysteine of its interacting partner Skp1 was labeled by the biotin–thiol molecule. This photoactivatable protein labeling method may find important applications including identification of weak and transient protein–protein interactions in the native cellular context, as well as spatial and temporal control of protein labeling.

Effects of methyl mercury on the activity and gene expression of mouse Langerhans islets and glucose metabolism

Mercury (Hg) is a well-known heavy metal and causes various toxic effects. It is abundantly present in fish in the form of methyl mercury (MeHg). Also, various other forms of mercury can enter human body either from environment like inhalation or through dental amalgams. The present study was designed to assess MeHg induced toxicity in mouse plasma and pancreatic islets with respect to insulin secretion, oxidative balance, glucose tolerance, gene expression, caspases 3 and 9 activities. MeHg was dissolved in tap water and administered at doses 2.5, 5 and 10 mg/kg/day, for 4 weeks. In mice, MeHg significantly caused increase in plasma insulin as well as C-peptides. Glucose intolerance, insulin resistance and hyperglycemia are main consequences of our study that correlate with the gene expression changes of glucose homeostasis as well. MeHg caused increase lipid peroxidation in a dose-dependent manner in plasma as well as pancreatic islets. In addition, total thiol molecules and ferrous reducing antioxidant power in MeHg treated group was decreased in plasma as well as pancreatic islets. Caspases 3 and 9 activities of pancreatic islets were upregulated in MeHg exposed animals. Reactive oxygen species were extremely high in pancreatic islets of MeHg treated groups. MeHg disrupted gluconeogenesis/glycogenolysis pathways and insulin secretory functions of islets by targeting GDH, GLUT2 and GCK genes of pancreatic islets. In conclusion, the current study revealed that insulin pathways, oxidative balance and glucose metabolism encoded genetic makeup are susceptible to MeHg toxicity and the subsequent oxidative stress and alternations in gene expression could lead toward functional abnormalities in other organs.

Influence of Temperature on the Nanoadhesion of a Methyl-Terminated Thiol Monolayer: A New Insight with High-Rate Dynamic Force Spectroscopy.

Alkanethiols form stable, homogeneous, and well-organized self-assembled monolayers and can be used as lubricants in micro- and nanodevices when sufficiently hydrophobic and resistant to sudden temperature changes. In this paper, we demonstrate a new analysis method which provides a deep physical insight into adhesive interactions and their temperature dependencies at the single molecule level. We have focused on the adhesion between a silicon nitride tip and a 1-decanethiol self-assembled monolayer in the temperature range from 25 to 85 °C. We performed dynamic force spectroscopy measurements and applied theoretical models of adhesive-mechanical interactions and thermally activated unbinding to obtain detailed information on the adhesive interactions. The parameters of the interaction potential describing a single adhesive bond were calculated, and their temperature dependence was discussed. Although the changes of the adhesion force versus temperature are significant and nonmonotonic, the energy of the activation barrier of a single adhesive bond appears temperature independent. We attribute observed changes in the position of the activation barrier to the interplay between the rupture and rebinding of adhesive bonds, as well as to thermal reorganization, in particular the change of the tilt angle of thiol molecules in the self-assembled monolayer.

Tempol effects on diabetic nephropathy in male rats.

Introduction: Diabetic nephropathy (DN) is the most common cause of the chronic kidney disease in the world. Oxidative stress on the other hand has a major and well known role in its pathophysiology. Objectives: The aim of the study is to figure out if tempol, a synthetic antioxidant agent, modifies DN and to determine its relevance to changes of serum oxidative biomarkers. Materials and Methods: Twenty-seven male rats were equally divided in to 4 groups (7 rats for each group). Group I (control or C), group II (diabetic or D), groups III (Tempol) which were given tempol (100 mg/kg/day) by gavages for 28 days and group IV (D&T) which includes diabetic rats that also received same dose of tempol. After treatment, blood samples were isolated. Enzymatic scavengers including catalase (CAT), glutathione peroxidase (GPx) and superoxide dismutase (SOD) activities, lipid peroxidation (LPO), total antioxidant capacity (TAC) and total thiol molecules (TTM) were measured. Blood urea nitrogen (BUN), creatinine (Cr) an albumin/Cr ratio were evaluated as well. Statistical differences were assessed with one-way analysis of variance (ANOVA) by SPSS followed by Tukey t test. Results: Oxidative stress biomarkers modified and Alb/Cr ratio increased in diabetic group (II), however, they were altered to normal in group IV (D&T) compared with diabetic group (D). Conclusion: Tempol can modify oxidative stress biomarkers and presumably nephropathy in diabetic rats.

Maternal Parity and Blood Oxidative Stress in Mother and Neonate

Background: Parturition has been associated with free radicals, itself linked with poor pregnancy outcome. Objectives: This study aimed to investigate the relationship between oxidative stress biomarkers levels of maternal and cord blood samples at the second stage of labor with the maternal parity number. Materials and Methods: In this analytical cross-sectional study, subjects were selected from Fatemieh teaching hospital, Hamadan, Iran, and allocated into the two groups according to their number of parity: the primiparous group (n = 33), and multiparous group (n = 35). Maternal and umbilical cord blood samples were taken from all subjects and then assessed for catalas activity (CAT), total thiol molecules (TTM) and total antioxidant capacity (TAC). Results: Total antioxidant capacity levels were significantly higher in newborns of primiparous women compared to multiparous women (P = 0.006). The CAT levels were significantly lower (P = 0.04) and TAC levels significantly higher (P = 0.03) in maternal plasma of primiparous women compared to those of multiparous women. Conclusions: Increment in the number of parity can lead to decrease antioxidant defense mechanisms in multiparous women and their newborns. So, control of oxidative stress is considered to be beneficial in multiparous women. Keywords: Oxidative Stress, Antioxidants, Parity

9-Fluorenylmethyl (Fm) Disulfides: Biomimetic Precursors for Persulfides.

The development of a functional disulfide, FmSSPy-A (Fm = 9-fluorenylmethyl; Py = pyridinyl), is reported. It can effectively convert small molecule and protein thiols (−SH) to form −S-SFm adducts under mild conditions. This method allows for a H2S-free and biomimetic protocol to generate highly reactive persulfides (in their anionic forms). The high nucleophilicity of persulfides toward a number of thiol-blocking reagents is also demonstrated. The method holds promise for further understanding the chemical biology of persulfides and S-sulfhydration.

Nanostructuring of Molecular Assembly Using Electrochemical Reductive Desorption of Locally Stabilized Thiol Monolayers

Nanostructuring of molecular monolayers is indispensable for integration of multiple functionality within a monolayer. Here, a fabrication method of two-component molecular assembly with nanoscale structures is demonstrated by a combination of reductive desorption of thiol molecules from a Au(111) substrate with local stabilization of the molecular layers using adsorption of Au nanoparticles. The average sizes of the obtained nanoscale molecular features were controlled by changing the size of nanoparticles. A unique functionality of size-controlled nanostructures was presented using redox responses of ferrocene-terminated molecules as a collective response of ferrocene moieties in each nanostructured assembly.

Induction of humoral immune response against Pseudomonas aeruginosa flagellin(1-161) using gold nanoparticles as an adjuvant

Flagellin of Pseudomonas aeruginosa is an important vaccine candidate. N-terminal domains are highly conserved in both type a and type b flagellins. The efficacy of gold nanoparticles (AuNPs) conjugated to N-terminal domains of P. aeruginosa flagellin (flagellin(1-161)), as an immunogen in mice, has been assessed. The nanoparticles were conjugated to the recombinant protein through direct interaction of thiol molecules of the cysteines with AuNPs and formation of AuS bond. Flagellin(1-161), AuNP-flagellin(1-161), and flagellin(1-161) emulsified in Freund's adjuvant (FA: complete/incomplete Freund's adjuvant formulation) were administered subcutaneously to BALB/c mice. Mice given AuNP-flagellin(1-161) elicited high titers of anti-flagellin(1-161) antibodies compared with non-immune group and/or mice which received flagellin(1-161) without adjuvant. In whole cell ELISA, these antibodies effectively recognized the native flagellin on the bacteria. Opsonophagocytosis assay demonstrated the functional activity and specificity of anti-flagellin(1-161) antibodies raised by AuNP-flagellin(1-161) against homologous strain. All of the results were comparable with those obtained by use of FA. Taken together, this is the first report of conjugation of AuNPs to flagellin and evaluating its immune response against P. aeruginosa.

Unique feature of chain reactions of thiols with quinone imines: thiols as reactants and simultaneously catalysts at the rate-determining step of chain propagation

The isomerization of radical adducts, formed due to the addition of thiyl radicals to the cyclohexadiene ring of quinone imine, to phenoxyl and aromatic aminyl radicals is considered by quantum chemical methods (DFT/PBE and CCSD). Isomerization via the intramolecular transfer of the highly mobile H atom of the C—H bond to the O or N atoms from the position of PhS• radical addition to the cyclohexadiene ring of quinone imine cannot virtually occur because of the high activation energy comparable or even exceeding the C—H bond dissociation energy. An alternative bimolecular mechanism involving the thiol molecule, which is inserted into the transition state thus extending it to be favorable for the reaction to occur, was proposed. After the reaction, the thiol is regenerated, i.e., acts as both the reactant and catalyst of the chain reaction of quinone imine with thiol. The reasons for the high rate of the H atom transfer via this mechanism are considered.

Protective Effect of Selenium-Based Medicines on Toxicity of Three Common Organophosphorus Compounds in Human Erythrocytes In Vitro.

Organophosphorus (OP) compounds are used to control pests, however they can reach the food chain and enter the human body causing serious health problems by means of acetylcholinesterase (AChE) inhibition and oxidative stress (OS). Among the OPs, chlorpyrifos (CHP), malathion (MAL), and diazinon (DIA) are commonly used for commercial extermination purposes, in addition to veterinary practices, domestic, agricul- ture and public health applications. Two new recently registered medicines that contain selenium and other antioxidants, IMOD and angipars (ANG), have shown beneficial ef- fects for OS related disorders. This study examines the effect of selenium-based medi- cines on toxicity of three common OP compounds in erythrocytes. In the present experimental study, we determined the ef- ficacy of IMOD and ANG on OS induced by three mentioned OP pesticides in human erythrocytes in vitro. After dose-response studies, AChE, lipid peroxidation (LPO), total antioxidant power (TAP) and total thiol molecules (TTM) were measured in eryth- rocytes after exposure to OPs alone and in combined treatment with IMOD or ANG. AChE activity, TAP and TTM reduced in erythrocytes exposed to CHP, MAL and DIA while they were restored in the presence of ANG and IMOD. ANG and IMOD reduced the OPs-induced elevation of LPO. The present study shows the positive effects of IMOD and ANG in re- duction of OS and restoration of AChE inhibition induced by CHP, MAL and DIA in erythrocytes in vitro.

The self-crosslinking smart hyaluronic acid hydrogels as injectable three-dimensional scaffolds for cells culture

Although the disulfide bond crosslinked hyaluronic acid hydrogels have been reported by many research groups, the major researches were focused on effectively forming hydrogels. However, few researchers paid attention to the potential significance of controlling the hydrogel formation and degradation, improving biocompatibility, reducing the toxicity of exogenous and providing convenience to the clinical operations later on. In this research, the novel controllable self-crosslinking smart hydrogels with in-situ gelation property was prepared by a single component, the thiolated hyaluronic acid derivative (HA-SH), and applied as a three-dimensional scaffold to mimic native extracellular matrix (ECM) for the culture of fibroblasts cells (L929) and chondrocytes. A series of HA-SH hydrogels were prepared depending on different degrees of thiol substitution (ranging from 10 to 60%) and molecule weights of HA (0.1, 0.3 and 1.0MDa). The gelation time, swelling property and smart degradation behavior of HA-SH hydrogel were evaluated. The results showed that the gelation and degradation time of hydrogels could be controlled by adjusting the component of HA-SH polymers. The storage modulus of HA-SH hydrogels obtained by dynamic modulus analysis (DMA) could be up to 44.6kPa. In addition, HA-SH hydrogels were investigated as a three-dimensional scaffold for the culture of fibroblasts cells (L929) and chondrocytes cells in vitro and as an injectable hydrogel for delivering chondrocytes cells in vivo. These results illustrated that HA-SH hydrogels with controllable gelation process, intelligent degradation behavior, excellent biocompatibility and convenient operational characteristics supplied potential clinical application capacity for tissue engineering and regenerative medicine.

Electron transfer across the germanium-polyelectrolyte-gold nanoparticle interface: convenient detection and applications in sensing.

Germanium-polyelectrolyte-gold nanoparticle composites were prepared and characterized using FTIR-ATR spectroscopy and scanning electron microscopy. The germanium (Ge) element served as an internal reflection element and the buildup of the layered system was followed in situ. A positively charged polyelectrolyte, poly (allylamine hydrochloride) (PAH) adsorbs spontaneously on negatively charged Ge. Citrate-stabilized gold nanoparticles can then be adsorbed onto the PAH layer. Upon illumination of the device with visible light a prominent absorption over the entire mid infrared region is observed which is due to intervalence band transitions in Ge. The strong infrared signals are evidence for holes in the valence band of the Ge semiconductor, which arise due to electron transfer to the gold nanoparticles (GNPs). The electron transfer, as evidenced by the holes in Ge, is affected by the nature of the gap between the Ge semiconductor and the GNPs. Increasing the gap by adsorbing polyelectrolyte multilayers hinders the electron transfer. Also, heating and vacuum have a pronounced effect. The device is proposed as a sensor, where the sensing event is transduced into an optical signal in the infrared region, as demonstrated for a thiol molecule. The thiol has a large affinity for gold, and therefore affects the germanium-gold nanoparticle gap. This reduces the electron transfer, and therefore the absorption in the infrared region upon illumination with visible light. Removal of the thiol from the solution leads to the recovery of the signal.

Investigating the stability of gold nanorods modified with thiol molecules for biosensing

Studying the stability of centrifugated gold nanorods unmodified/modified with thiols.

Heat-enhanced symmetry breaking in dynamic gold nanorod oligomers: the importance of interface control.

We reported a surprisingly strong plasmonic circular dichroism (PCD) response in side-by-side (SS) oligomers of gold nanorods (GNRs) just by a simple heat treatment. The maximal anisotropic (g) factor achieved was up to 0.065, one of the largest reported for plasmon-enhanced chiral nanostructures based on a bottom-up strategy. The introduction of chiral thiolated molecules is suggested to guide the symmetry breaking of GNR assemblies and heat treatment provides the necessary energy to assist this process, and thus produces a huge PCD. Furthermore, we first demonstrated the critical role of the non-chiral component (surfactant layer) on the gold nanorod surface in mediating symmetry breaking. Our findings highlight the importance of interface control in the formation of chiral configuration for a plasmonic nanoparticle system. It offers new possibilities for fabricating nanostructures with strong chiroptical activity by the rational design of interface layers.

Effect of active acidic compounds on storage stability of coker naphtha

Coker naphtha was separated into ten distillation fractions equal in volume via Engler distillation. It was found that the mercaptan sulphur compounds were mainly concentrated in the lighter fractions, whereas the basic nitrogen compounds were concentrated in the heavier fractions. The gum content increased gradually with increasing the boiling point of each fraction after storage for 21 days under ambient conditions (25°C, 101 kPa). The active organic acidic compounds in coker naphtha extracted with aqueous solution of 20 mass % NaOH represented 0.26 mass %. The GCMS analysis of the active organic acidic compounds showed the amounts of small molecule thiols, thiophenols (including benzyl mercaptan) and phenolic compounds to be 2.6 %, 4.4 % and 90.0 %, respectively. After removal of the active acidic compounds by caustic scrubbing, the increase in the rate of gum formation was much slower than that of the blank coker naphtha after 27 days of storage under ambient conditions, indicating that the effect of these acidic compounds on the gum formation is more significant than with basic nitrogen compounds. It is demonstrated that the storage stability of coker naphtha was decreased in the presence of large amounts of phenolic compounds, which may accelerate the acid-catalysed polymerisation of olefins.

Protective role of green tea on malathion-induced testicular oxidative damage in rats

Abstract Objective To examine effects of total green tea extract, a potent free radical scavenger on testicular tissue oxidative status. Methods 32 male albino rats of Wistar strain were divided into four groups, every group restricted 8 animals: (i) control rats; (ii) green tea-treated control rats; (iii) malathion rats; (iv) malathion-treated green tea rats. Animals received malathion 150 mg/kg and green tea 30 mg/kg for 24 h intraperitoneally. At the end of the treatment period, rat testis tissues were quickly removed and analyzed. Diameter of seminiferous tubules and germinal cell thickness, spermatogonia sertoli cells, primary spermatocytes, spermatids and leydig cell were evaluated. Also, oxidative stress evaluation was conducted based on total antioxidant capacity (TAC), lipid peroxidation (LPO) and total thiol molecules (TTM) in homogenate testis tissues. Results The results showed that total green tea extract improve oxidative damages against malathion group. Light photomicrograph of seminiferous tubules in malathion-treated group showed noticeable reduced height of germinal epithelium and disorganization of the tubules. An increased intestinal tissue was also observed. Primary spermatocytes were located distance from basal lamina indicating it induced damages to the intestinal tissue. While seminiferous tubules in malathion exposed and green tea extract-treated were normal. Conclusion This study demonstrated the effectiveness of TGTE on oxidative stress and testicular tissue damage induced in malathion in infertility disorders.

Controlled Doping of Vacancy-Containing Few-Layer MoS2 via Highly Stable Thiol-Based Molecular Chemisorption.

MoS2 is considered a promising two-dimensional active channel material for future nanoelectronics. However, the development of a facile, reliable, and controllable doping methodology is still critical for extending the applicability of MoS2. Here, we report surface charge transfer doping via thiol-based binding chemistry for modulating the electrical properties of vacancy-containing MoS2 (v-MoS2). Although vacancies present in 2D materials are generally regarded as undesirable components, we show that the electrical properties of MoS2 can be systematically engineered by exploiting the tight binding between the thiol group and sulfur vacancies and by choosing different functional groups. For example, we demonstrate that NH2-containing thiol molecules with lone electron pairs can serve as an n-dopant and achieve a substantial increase of electron density (Δn = 3.7 × 10(12) cm(-2)). On the other hand, fluorine-rich molecules can provide a p-doping effect (Δn = -7.0 × 10(11) cm(-2)) due to its high electronegativity. Moreover, the n- and p-doping effects were systematically evaluated by photoluminescence (PL), X-ray photoelectron spectroscopy (XPS), and electrical measurement results. The excellent binding stability of thiol molecules and recovery properties by thermal annealing will enable broader applicability of ultrathin MoS2 to various devices.

Byproduct-induced in-situ formation of gold colloidal superparticles

Current work presents a simple and efficient method for the preparation of gold superparticles. The self-assembly of gold nanoparticles into colloidal superparticles was realized in-situ during the preparation of nanoparticles when a type of thiol molecules were used as ligands. Further investigation reveals that t-butylamine hydrochloride, an ionic byproduct generated during the redox reaction of precursors, plays a key role in the formation of gold superparticles. The polarity of monolayers made from these ligands on the nanoparticle surface allows the interaction of nanoparticles and the ionic byproduct, which is indispensable for the superparticle formation.