Mercapto Function Research Articles

Rapid sequential detection of Hg2+ and biothiols by a probe DNA—MOF hybrid sensory system

A one-dimensional (1D) metal–organic framework (MOF) of [Cu(Cdcbp)(H2O)2·2H2O]n (1, H3CdcbpBr = 3-carboxyl-(3,5-dicarboxybenzyl)-pyridinium bromide) has been synthesized and characterized. MOF 1 features a cationic Cu2+ center, conjugated tricarboxylate ligand bearing positively charged pyridinium and uncoordinated carboxylate groups within its skeleton. These features enable MOF 1 to tightly adsorb thymine rich (T-rich) single-stranded DNA (ss-DNA) probe labeled with carboxyfluorescein (FAM) (denote as P-DNA) through π-stacking, electrostatic interactions and/or hydrogen bonding to give a hybrid complex (denote as P-DNA@1), and quenches its fluorescence via a photo-induced electron transfer (PET) process. The formed P-DNA@1 hybrid can thus function as a sensing platform for the detection of Hg2+, driven by the formation of hairpin-like double-stranded DNA (ds-DNA@Hg2+) with a T-Hg-T coordination motif, and subsequently dissociated into the solution due to its more rigid nature than ss-DNA, leading to the recovery of FAM fluorescence. In the presence of biothiols, including cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), the strong coordination interaction between Hg2+ and the mercapto function serves to sequestrate the Hg2+ from the ds-DNA@Hg2+ duplex. The released ss-DNA, in turn, are re-adsorbed by MOF 1, leading to the formation of the initial P-DNA@1 state with fluorescence quenching. As such, P-DNA@1 detects Hg2+ and biothiols Cys/Hcy/GSH in sequence with detection limits of (2.3 ± 0.8) nM and (29.6 ± 0.1) nM/(19.8 ± 0.5) nM/(10.2 ± 0.1) nM. The sensing process is efficient and selective with instantaneous response time. The detection mechanism was further validated by circular dichroism (CD), and simulation studies using Molecular Operating Environment (MOE) package.

Design, synthesis, and evaluation of the antimycobacterial activity of3-mercapto-1,2,4-triazole–pyrrole hybrids

A series of 3-mercapto-1,2,4-triazole--pyrrole hybrids was designed as antimycobacterial agents by employing 5-(4-(1$H$-pyrrol-1-yl)phenyl)-4$H$-1,2,4-triazole-3-thiol as the scaffold onto which several types of moieties were introduced in the triazole ring at N-4 and N-2 and as substituents of the mercapto function. The aforementioned moieties are an allyl or a phenyl moiety at N-4; an aminomethyl group at N-2; or methyl, substituted benzyl, ethoxycarbonylmethyl, or substituted phenacyl at sulfur. Investigation of the compounds in the resulting library as growth inhibitors of Mycobacterium smegmatis showed that their minimum inhibitory concentration was higher than 64 mg/L.

High-Performance Hg(II) Removal Using Thiol-Functionalized Polypyrrole (PPy/MAA) Composite and Effective Catalytic Activity of Hg(II)-Adsorbed Waste Material

Problems related with highly toxic mercury emissions from industrial effluents are one of the great concerns in the world of environmental science and technology. The primary aim of this present work is the remediation of hazardous pollutant Hg (II) from aqueous medium via a thiol-functionalized (mercaptoacetic acid) conducting polypyrrole (PPy/MAA) composite. The synthesized composite exhibited high Hg(II) adsorption capacity as the incorporated mercapto functionality plays a vital role for the strong binding affinity toward Hg(II) ions. To understand the adsorption properties of the developed polymer composite, a series of batch adsorption experiments were performed by altering the adsorption parameters. A maximum adsorption capacity (qmax) of 1736.8 mg/g at 25 °C was obtained using the Langmuir isotherm. The adsorption data showed better fitting to the pseudo-second-order rate equation for Hg(II) adsorption. A plausible adsorption mechanism is suggested on the basis of XPS results of major elements present in the adsorbent. To apply to catalytic reactions, the use of waste-derived mercury-adsorbed material (termed as PPy-MAA/Hg (II)) is also addressed here for further application of organic transformation. Here, we described the catalytic reaction with phenylacetylene in the presence of 5 mol % PPy-MAA/Hg (II) catalyst at 90 °C for 6 h. This method provides a straightforward formation of acetophenone in 55% yield. Thus, PPy/MAA not only effectively eliminates toxic Hg(II) ions from water but also is successfully applied for the catalytic organic transformation after adsorption.

Facile Functionalization of Polymer Surfaces in Aqueous and Polar Organic Solvents via 3-Mercaptopropylsilatrane.

Surface modification of a polymer substrate with a mercapto functionality is crucial in many applications such as flexible circuitry and point-of-care biosensors. We present here a novel bifunctional molecular adhesive, 3-mercaptopropylsilatrane (MPS), as an interface between polymer and metal surfaces. Under ambient conditions, surface modification of polymer surfaces with a mercapto functionality can be achieved with low concentration (0.46 mM) of MPS in aqueous solvent (50% ethanol) in a short time (<30 min). Three popular polymers for optical sensors, polycarbonate, polyethylene terephthalate, and poly(methyl methacrylate), were employed as substrates, and MPS films formed on these substrates were examined and compared with that on a glass substrate. The films were characterized by UV-vis spectroscopy, water contact angle, X-ray photoelectron spectroscopy, and atomic force microscopy. MPS was also used as a bifunctional linker for the construction of a gold nanoparticle (AuNP) sub-monolayer on these polymer surfaces. Under optimized preparation conditions, the absorbance and full width at half-maximum of the plasmon band are comparable to those of a AuNP-modified glass substrate. Hence, MPS may have a potential to be a key component in polymer substrate-based localized surface plasmon resonance sensors. A self-catalytic surface reaction mechanism is also proposed to account for the results. As compared to a glass surface with a high number of silanol groups, the successful formation of an MPS film on polymer surfaces with relatively few reactive sites is probably due to the lateral polymerization of MPS starting from a condensed MPS molecule on a reactive site of a polymer surface.

Composite sorbents based on porous ceramic substrate and hybrid amino- and mercapto-silica materials for Ni(II) and Pb(II) ions removal

Abstract Tubular porous ceramic substrates based on crystalline SiO2 were successfully functionalized with amino and mercapto functions using the one-step sol-gel approach. The samples were analyzed by SEM, FT-IR spectroscopy, low-temperature nitrogen adsorption-desorption to reveal their structure and composition. It was shown, that the functional layers of such materials contain silica nanoparticles with amino and mercapto groups, and their porosity can be varied regarding the nature of the structuring agent. All the amino-functionalized membranes showed 95% retention of Ni(II) ions from aqueous solution for 2 h of filtration in the filtration unit (at room temperature). Whereas, maximum retention by mercapto-functionalized membranes was 30% of Pb(II) ions.

Synthesis of tritium labelled thiorphan, an enkephalinase inhibitor

AbstractTritium labelling of the enkephalinase inhibitor, thiorphan, is complicated by the presence of mercapto functional group. Reactions often used in aromatic tritiation, such as halogination and catalytic halogen/tritium displacement, are adversely affected by the presence of the divalent sulfur moeity. By protecting the SH group with t‐butyl group, the tritiation reaction proceeded smoothly without catalyst poisoning. The mercapto functionality was re‐generated with great ease and efficiency using 2‐nitrobenzenesulfenyl chloride and dithiothreitol (DTT). [3H]‐Thiorphan, thus, obtained had a radiochemical purity of &gt;99% by AN‐HPLC and a specific activity of 18.42 Ci/mmol. [3H]‐Thiorphan showed good stability when stored at 4°C in an aqueous solution containing 10% methanol and 0.2% DTT in the dark. Copyright © 2008 John Wiley &amp; Sons, Ltd.

New Stimuli Responsive Poly(1‐vinylpyrrolidin‐2‐one) Bearing Pendant Activated Disulfide Groups

AbstractSummary: A novel functionalised poly(1‐vinylpyrrolidin‐2‐one) (PVP) derivative, carrying a pre‐determined amount of 2‐(2‐pyridinyldithio)ethylamine moieties as side substituents, P(VP‐co‐VP‐SS‐Py), has been prepared from carboxylated VP copolymers, in turn obtained by copolymerising 1‐vinylpyrrolidin‐2‐one with 3,3‐di‐(ethoxycarbonyl)‐1‐vinylpyrrolidin‐2‐one in the presence of radical initiators. Using reaction solvents acting in the mean time as chain transfer agents could control its molecular weight. P(VP‐co‐VP‐SS‐Py) proved to be extremely reactive towards exchange reactions with molecules containing mercapto functions, including bioactive peptides. The exchange derivative with reduced glutathione, chosen as a model compound, was easily prepared. magnified image

Reaction of 5‐Hydrazono‐1,2,3‐thiadiazoles with Toluene and Xylene in the Presence of PCl5.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Reaction of 5-Hydrazono-1,2,3-thiadiazoles with Toluene and Xylene in the Presence of PCl5

The treatment of 5-hydrazono-1,2,3-thiadiazoles by phosphorus pentachloride in toluene or xylene leads to an anomalous Dimroth rearrangement and the reaction of the mercapto function formed with the methyl group of the solvent to give 5-benzylmercapto-1,2,3-triazole.

Ceric ammonium nitrate impregnated on silica gel in the removal of the tert-butoxycarbonyl group

The tert-butoxycarbonyl group was efficiently (80-99% yields) removed from an amino, hydroxy, or mercapto functionality in organic compounds by use of 0.20 equiv of Ce(NH4)2(NO3)6 in acetonitrile at reflux. Application of the solid-supported reagent involving the use of 0.20 equiv of Ce(NH4)2(NO3)6 impregnated on silica gel in toluene at reflux gave the deprotected products in 90-99% yields. These reactions likely proceed through an electron transfer process.

Tetraberyllium-η4-oxo-hexa(arylcarboxylates)

Abstract Tetraberyllium-oxo-hexabenzoate and -hexa(mesitylcarboxylate) were prepared from benzoic / mesitylcarboxylic acid and freshly precipitated beryllium hydroxide in a tetrahydrofuran / water two-phase system. The crystal structure of the benzoate was deter­ mined from Be4O(OCOPh)6(C6H6)3 , and that of the mesitylcarboxylate from the phase Be4O(OCOMes)6(CCl4). The two clusters have the μ4-oxo cage structure also detected for the acetate and nitrate complexes, and for the related hexacarbonato hexaanion. The high symmetry of the cluster allows the observation of 9Be and l7O signals in the solution NMR spectra. The terminal atoms of the rigid carboxylate groups may be expected to lie at the vertices of large octahedra enclosing the cluster molecules. The axes of the six aryl groups would thus coincide with the axes of the cartesian coordinates with the μ4 oxygen atom at the origin. This disposition suggests a connectivity suitable for cubic lattices if p-difunctional arene-dicarb-oxylate anions are employed instead of aryl-monocarboxylate anions. However, the new results show that significant deviations of the OBe2O2C-Ar six-membered rings from planarity cause major deviations from octahedral symmetry and therefore no connectivity in cubic symmetry is to be expected. Fragmentation of the Be4O(OCOR)6 clusters upon ionization in a mass spectrometer leads predominantly to cations [Be3O(OCOR)3]+ which can be assigned a planar, highly symmet­rical tricyclic core structure of D3h symmetry. Quantum chemical calculations confirm dis­ crete energy minima for these cations and show that their stability is largely due to the favourable arrangement of alternating charges of neighbouring core atoms. The high polar­ ity of Be-O bonds rules out any significant contributions from aromaticity. The reactions of Be(OH)2 with 4 -HS-C6H4 -COOH and HS(CH2)2COOH give the corresponding cluster com­ pounds Be4O(OCORSH)6, [R = C6H4 , (CH2)2] with six terminal mercapto functions.

Versatile Functionalization of Polylysine: Synthesis, Characterization, and Use of Neoglycoconjugates

Glycopolymers are useful macromolecules with a non-carbohydrate backbone for presenting saccharides in a multivalent form. Here, a new methodology is described which allows easy access to water-soluble, biodegradable glycopolymers with both predeterminable composition and molecular weight distribution. Thus, chloroacetylation of commercially available polylysine hydrobromide 3 gave the reactive homopolymer 4, whose chloroacetamide functions allowed subsequent coupling with thiol-containing components. Water-soluble homopolymers such as 8 and 13 were available by treatment with an excess of hydrophilic thiols. Heteroglycopolymers were obtained via quantitative incorporation of substoichiometric amounts of carbohydrates with a mercapto functionality linked to the reducing end; the remaining chloroacetamide groups were capped with an excess of thioglycerol. A variety of glycopolymers with up to four different components was prepared. The composition and purity of the products were reliably analyzed by 1H NMR. Generally, the quantitative incorporation of substoichiometric components was verified. The polymer backbone was not altered under the applied reaction conditions, as indicated by very similar polydispersities and degrees of polymerization of starting polylysine 3 and functionalized homo- and heteropolymers 8, 13, and 14. Glycopolymer 25, containing sialyl Lewisa and biotin as a functional group for enzyme-linked immuno sorbent assay, was used for developing cell-free selectin ligand binding assays. The inhibition of E-selectin by glycopolymers 16, containing sialyl Lewisx (sLex), was evaluated in a cell adhesion assay under flow conditions using activated human umbilical vein endothelial cells and polymorphonuclear neutrophils. The sLex polymers 16 showed no significant inhibition, whereas conjugates with additional charged groups (carboxylates 18, sulfonates 21) in addition to sLex gave 30−35% reduction of the number of interacting cells at the same concentration of 100 μM sLex.

Synthesis of optically active 3,4,5,6-tetrahydro-2H-1,4-thiazin-3-ones and their benzo analogues by ring transformation of glycidic esters

Chiral cis and trans glycidic esters 9 substituted by alkyl or ethoxycarbonyl react with cysteamine or o-aminothiophenol 10 by stereoselective ring transformation to non-aromatic optically active 2-(α-hydroxyalkyl)-1,4-thiazin-3-ones 12. The attack of the mercapto function at the α-position of the glycidate occurs predominantly by inversion of configuration. As compared with known reactions of aryl-substituted glycidates with o-aminothiophenol or cysteamine preferentially giving thiazepinones, a remarkable effect of the substituent in the glycidate on the regiochemistry was found.

Surprisingly Facile Addition of Thiols to the Double Bonds of Bicyclopropylidene and Other Methylenecyclopropanes

The addition of thiols 8a–h onto the double bonds of bicyclopropylidene (1) and methylenespiropentane (2) proceeds quantitatively in benzene at 20 to 75 °C in the absence of catalysts or radical initiators to give products 9, 10 with complete retention of both three-membered rings. Methylenespiropentane (2) yields exclusively the anti-Markovnikov adduct 10. The unsubstituted methylene-cyclopropane (3) gives 9% of the ring-opened compound 12 in addition to the anti-Markovnikov adduct 11. The addition of thiols to n-heptylbicyclopropylidene (13), methylenecyclopropylacetic acid (15), and the amino acids 17, 19 containing bicyclopropylidene or methylenespiropentane fragments, does not proceed stereoselectively, though in all cases the mercapto function adds to the double bond with retention of the cyclopropane ring to give interesting new amino acids containing bicyclopropyl and spiropentyl fragments, respectively. The probable mechanism of this thiol addition is discussed in the light of a test with the cyclizing intramolecular addition of 2-(2-methylenecyclopropyl)ethanethiol 27.

Regio- and stereospecific synthesis of ( O-tips)-protected 2-hydroxyalkylmercaptans from epoxides and triisopropylsilanethiol

The regiospecific ring-opening of both mono- and disubstituted epoxides with triisopropylsilanethiol/DBU has been developed to provide 2-triisopropylsilyloxyalkylthiols ( 1) in high yields. Non-racemic 1 is easily prepared from optically active epoxides. Moreover, the further elaboration of 1, through the exposed mercapto functionality, provides controlled access to unsymmetrical mono-protected bis-(2-hydroxyalkyl) sulfides and functionalized thioesters.

Formation of gold particles at a functional LB film/gold interface leading to Coulomb blockade phenomena

A few monolayer Langmuir-Blodgett (LB) films of a polymer that contains mercapto functions in the hydrophilic head group region were deposited on microstructured gold electrodes. Upon evaporation of a gold top contact, junctions without ohmic behaviour were obtained. In some cases the current-voltage ( I–V) characteristics displayed a step-like behaviour that is interpreted as the Coulomb blockade effect. To determine the nature and origin of the charged islands, cross-sectional specimens with a top gold electrode were prepared for transmission electron microscopy (TEM) investigations. The TEM images revealed the formation of small gold particles with diameters ranging from 2 to 6 nm located close to the top contact. These particles together with the surrounding polymeric matrix are expected to constitute a double-barrier tunnel structure and to be responsible for the observed single-electron tunnelling phenomena.

Interaction between S-organic compounds and iron surfaces

Detaching of organic polymer coatings as a consequence of a corrosive attack of the substrate material means as serious problem for corrosion protection [1]. Because of the coating thickness and the complex nature of practical corrosion protection systems, direct studies of the phase boundary metal/coating are impossible up to now. Therefore, the mechanism of deadhesion is largely unknown, The aim of this work now is to produce a strong chemical bond between the metal surface to be protected and selected organic monomers (concept of chemically modified metal surfaces [2]). This bond should be stable against aggressive media like strong acid or basic electrolytes. The thickness of the adsorbed organic film is only that of several molecular layers. Therefore, the binding conditions at the phase boundary can be investigated with electron spectroscopic (AES, XPS) and electrochemical (cyclovoltammetry, rotating ringdisk-electrode) methods. Up to now these studies are restricted to the interaction of n-decanethiol (n-DMc) with polycrystalline iron surfaces of different conditions. At room temperature n-DMc is a water like liquid. A first preparation technique means to drop the organic liquid without any further solvent onto the air formed oxide on top of the iron surface covered by a contamination layer. Within a second method the organic liquid is used as a second phase on top of an aqueous acid electrolyte (1 tool/1 HC10,). The sample is removed from the electrolyte at conditions that stabilize metallic iron and is passed through the n-DMc layer. At the phase boundary organic liquid/electrolyte the thiol molecules are oriented in such a manner that the polar (SH)-groups look into the electrolyte. By this a coupling of the sulphur to the metallic substrate occurs when the iron substrate passes the phase boundary. The same procedure is also performed under anodic conditions, so that a surface oxide is stabilized. The results of the surface analytical studies can be summarized as follows: For the oxide free surface the intensity ratios of the Auger peaks of carbon (CKLL) and of sulphur (SLMM) in the freshly prepared state and during Ar+-ion sputtering prove that the preferred orientation of the organic molecules at the phase boundary organic liquid/electrolyte is transferred to the chemisorbed molecules. The thiol binds to the metallic iron surface by the mercapto group (-SH). The aliphatic chains are oriented more or less perpendicular with respect to the surface. For preoxidized and contaminated iron surfaces the dropping technique results in a statistical arrangement within the thiol film. By modifying the iron substrate under anodic conditions only traces of n-DMc could be adsorbed on the oxidized surface and no further investigations were performed for these samples. The sensitivity of adsorbed thiol against oxidation depends on the orientation of the organic molecules and the chemical state of the iron surface. High resolution XP-spectra of the S-2p-niveau are discussed and interpreted in comparison to results reported by Holm [3] and to own reference measurements. At oxide free surfaces the main signal results from the chemical interaction between metallic iron and the mercapto function, the binding energy for the S-2p-electrons being comparable to values obtained for FeS and segregated sulphur atoms by Panzner et al. [4]. On the preoxidized surface only oxidation products of the thiol could be detected as for example sulfonate ions (R-SO~) and species exhibiting an electron density at the sulphur atom similar to organic disulfides (R-S-S-R). Additionally performed electrochemical investigations lead to the following conclusions: The n-DMc film bound to the metal under cathodic potential control is extremly stable in an Ar-purged borate buffer (pH 8.5) at potentials between -1 .1 VSHE and +0.0 VsnE. In the corresponding cyclovoltammograms no signals of the clean iron could be observed. The application of more anodic potentials leads to the formation of one monolayer Fe3+-ions without any damage of the n-DNc layer. An oxidative desorption of the thiol molecules occurs only then, if the sample is polarized to -1 .1 VSnE in an O2-purged borate buffer for several minutes.

Decreased vascular responsiveness produced by angiotensin-converting enzyme inhibitors in the rat isolated kidney.

The effects of three angiotensin converting enzyme (ACE) inhibitors - captopril, MK-421 diacid, and teprotide - on renal vascular responses to graded (50, 100, 200 ng) injections of norepinephrine (NE) were examined in rat isolated perfused kidneys, having a mean basal perfusion pressure of 78 +/- 10 mm Hg. The minimum dose of captopril (0.05 microgram/ml, low dose) that abolished the vasoconstrictor responses to 100 and 200 ng angiotensin I did not affect NE-induced renal vasoconstriction, whereas a dose 100 times greater (high-dose captopril, 5 micrograms/ml) reduced the vasoconstrictor action of NE. MK-421 diacid also at high dose (1 microgram/ml), caused similar reduction in renal vasoconstrictor responses to NE. In contrast, a high dose of teprotide (50 micrograms/ml) did not affect renal vascular responsiveness to NE. The threshold dose of NE that released prostaglandins, measured by bioassay, was 50 ng. Indomethacin (1 microgram/ml) prevented NE-induced release of prostaglandins but did not affect the ability of captopril to attenuate NE-induced vasoconstriction. We conclude that captopril and MK-421 diacid decreases vascular reactivity in the rat isolated kidney by a mechanism independent of ACE inhibition and unrelated to a prostaglandin-dependent vascular mechanism. Moreover, the presence of mercapto function in the ACE inhibitor is not essential since captopril, which has a sulfhydryl group, and MK-421 diacid, which lacks this group, have similar effects on renal vascular responsiveness.

Chemical modification of enzymes I. Two-step cross-linking of bovine pancreatic ribonuclease

A new procedure for the statistical cross-linking of enzymes is described. In the first step the enzyme polythiolated with N-acetylhomocysteine thiolactone, whilst in the second step the mercapto functions are intramolecularly cross-linked with different bifunctional reagents or by oxidation. With bovine pancreatic ribonuclease A, eight mercapto groups were introduced. After cross-linking with bis-iodoacetamides of different length, RNase with an optimum relative activity (c-CMP) of 144% was obtained. In addition, the pH optimum was shifted upwards by 0.8 pH units.