SEARCH · PubMed Health

Results for “THIOGLYCOLLIC ACID”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11Linked to original sources

PubMed2005

NO-donors, part X [1] : investigations on the stability of pentaerythrityl tetranitrate (PETN) by HPLC-chemoluminescence-N-detection (CLND) versus UV-detection in HPLC.

HPLC in combination with chemoluminescence-N-detection (CLND) is very useful for the analysis of pentaerythrityl tetranitrate (PETN) and its possible biological and chemical degradation products pentaerythrityl trinitrate (PETriN), pentaerythrityl dinitrate (PEDiN) and pentaerythrityl mononitrate (PEMonoN). Quantification is more convenient and sensitivity of this method is about four times higher compared to UV-detection. The present study demonstrates that PETN is a chemically more stable compound in vitro than expected. No degradation was observed in aqueous buffers (37 degrees C, pH 5.6, 7.4), human plasma, and simulated intestinal or gastric fluid. On the other hand, the addition of increasing amounts of thioles (cysteine, thioglycolic acid) induced an increasing degradation of PETN.

Chromatography, High Pressure Liquid↗

PubMed2004

Light-absorption ratio variation approach to determination of nickel (II) in ng/ml level with 1, 5-di(2-hydroxy-5-sulfophenyl)-3-cyanoformazan.

The light-absorption ratio variation approach (LARVA) has been described and applied to the quantitative detection of ultramicro amounts of Ni by spectrophotometry, which raises notably the detection sensitivity. The complexation between 1, 5-di(2-hydroxy-5-sulfophenyl)-3-cyanoformazan (DSPCF) and Ni(II) at pH 9.11 was investigated and the binary complex was characterized by the spectral correction technique. Results have shown that deltaAr-1 (deltaAr--light-absorption ratio variation) is linear in the range of Ni(II) between 5 and 200 ng/ml. The limit of detection (3sigma) of Ni(II) is only 1.3 ng/ml. The complexation is selective in the presence of fluoride, hexametaphosphate, ethylene diamine tetraacetate and thioglycollic acid. It has been applied to analysis of water quality with satisfactory results.

Environmental Monitoring↗

PubMed2003

Hybridization biosensor using di(2,2'-bipyridine)osmium (III) as electrochemical indicator for detection of polymerase chain reaction product of hepatitis B virus DNA.

A novel hepatitis B virus (HBV) DNA biosensor was developed by immobilizing covalently single-stranded HBV DNA fragments to a gold electrode surface via carboxylate ester to link the 3(')-hydroxy end of the DNA with the carboxyl of the thioglycolic acid (TGA) monolayer. A short-stranded HBV DNA fragment (181bp) of known sequence was obtained and amplified by PCR. The surface hybridization of the immobilized single-stranded HBV DNA fragment with its complementary DNA fragment was evidenced by electrochemical methods using [Os(bpy)(2)Cl(2)](+) as a novel electroactive indicator. The formation of double-stranded HBV DNA on the gold electrode resulted in a great increase in the peak currents of [Os(bpy)(2)Cl(2)](+) in comparison with those obtained at a bare or single-stranded HBV DNA-modified electrode. The mismatching experiment indicated that the surface hybridization was specific. The difference between the responses of [Os(bpy)(2)Cl(2)](+) at single-stranded and double-stranded DNA/TGA gold electrodes suggested that the label-free hybridization biosensor could be conveniently used to monitor DNA hybridization with a high sensitivity. X-ray photoelectron spectrometry technique has been employed to characterize the immobilization of single-stranded HBV DNA on a gold surface.

2,2'-Dipyridyl↗

PubMed1982

Suppression of the argyrophil III reaction by mercapto compounds (a prerequisite for the intensification of certain histochemical reactions by physical developers).

The tissue structure catalyse the interaction of silver ions with reducing molecules dissolved in physical developers, producing metallic silver grains bound at the sites of their formation (argyrophil III reaction). This reaction can be considerably slowed by a treatment with thioglycolic acid or certain other mercapto compounds before development. This observation offers a means for intensifying the end-products of certain histochemical reactions through the use of physical developers, without the microscopic image being interfered with or masked by the "unspecific" staining originating from the argyrophil III reaction.

Brain↗

PubMed2002

Design and in vitro evaluation of a novel bioadhesive vaginal drug delivery system for clotrimazole.

It was the purpose of this study to design and evaluate a new bioadhesive vaginal drug delivery system for clotrimazole. Chitosan, a cationic biopolymer derived by deacetylation of chitin, was modified by the introduction of thioglycolic acid (TGA). The modification was achieved by utilising a carbodiimide to link the carboxylic acid moieties of TGA covalently to the primary amino groups of chitosan. The amount of added carbodiimide was thereby varied, resulting in chitosan-TGA conjugates A and B with 160 microM (=micromol) and 280 microM thiol groups per gram polymer, respectively. In order to characterise the new polymers the water uptake, the disintegration behaviour, the bioadhesive properties utilising the rotating cylinder method, as well as the release of clotrimazole from tablets based on these derivatives were studied. The water uptake and cohesive properties of vaginal tablets consisting of these new conjugates could be significantly (p<0.05) improved. By adding clotrimazole the disintegration time of the conjugates was prolonged 1.6-fold for conjugate A and even 100-fold for conjugate B. Furthermore, the adhesion on vaginal mucosal tissue could be significantly improved. The addition of clotrimazole had also an impact on the adhesion time of chitosan-TGA conjugate B, which remained 26-times longer on vaginal mucosa than the corresponding unmodified polymer. The immobilisation of thiol groups guarantees a controlled drug release. Results of this study demonstrate that these new chitosan-TGA conjugates are very promising vehicles for the vaginal application of clotrimazole in treatment of mycotic infections.

Adhesiveness↗

PubMed2002

Bifunctional derivative of p,p'-dichlorochalcone. Part III. Synthesis and study for cytotoxic activity of a new compound, 2-[2,2-bis(4-chlorophenyl)ethyl]-2-(4-chlorophenyl)-thiazolidin-4-one from p,p'-dichlorochalcone.

The synthesis of 2-(2,2-bis(4-chlorophenyl)ethyl]-2-(4-chlorophenyl)-thiazolidin-4-one (3) from p,p'-dichlorochalcone (1) via 1,3,3-tris(4-chlorophenyl)-propan-1-one (2) using thioglycollic acid in the presence of ammonium carbonate is described. Structural assignment, stereochemistry and biological assay are discussed.

Antineoplastic Agents↗

PubMed2002

Synthesis of newer thiadiazolyl and thiazolidinonyl quinazolin-4 3H-ones as potential anticonvulsant agents.

A series of 3-[[5-(alkylbenzylideneamino)-1,3,4-thiadiazol-2-yl]methylamino-2]-methyl-6-monosubstitutedquinazolin-4(3H)-one (4a-4l) have been synthesized via condensation of 3-[(5-amino-1,3,4-thiadiazol-2-yl)methylamino]-2-methyl-6-monosubstitutedquinazolin-4(3H)-one (3a-3b) with various aromatic aldehydes. Cycloaddition of thioglycolic acid with 4a-4l yielded 3-([4-[2-(alkylphenyl)-4-oxo-1,3-thiazolidin-3-yl]-1,3,4-thiadiazol-2-yl]methylamino)-2-methyl-6-monosubstitutedquinazolin-4(3H)-one (5a-5l). The compounds were screened for their anticonvulsant activity and were compared with the standard drugs, phenytoin sodium, lamotrigine and sodium valproate. Out of the 30 compounds the most active compound was 3-([4-[2-(m-methoxy-p-hydroxyphenyl)-4-oxo-1,3-thiazolidin-3-yl]-1,3,4-thiadiazol-2-yl]methylamino)-2-methyl-6-bromo-quinazolin-4(3H)-one (5l).

Animals↗

PubMed2002

Validation of a spectrophotometric method for the determination of iron (III) impurities in dosage forms.

A spectrophotometric method (lambda=535 nm) for the iron (III) impurities determination in iron protein-succinylate complex syrup using thioglycolic acid in basic ambient was proposed and validated. Assay samples were treated with 0.1 N hydrochloric acid and centrifuged to remove the interfering active drug. Linear response (r=0.9999) was observed over the range of 0.005-0.2% of the iron (III) with respect to the complex nominal concentration. The accuracy could be considered very satisfactory (recovery=97-99%). The intra-day precision (RSD) of impurity amongst six independent sample preparations, was 1.4%, and there was no significant difference between intra- and inter-day studies. Intermediate precision indicated that the assay possessed high degrees of ruggedness. The limit of quantitation was 0.005% of impurity with respect to the active drug. The results obtained for iron (III) were compared statistically with those obtained with the standard addition method by means of the Student's t-test and the variance ratio F-test; no significative difference was found.

Drug Contamination↗

PubMed2004

Thiolated chitosans.

The derivatization of the primary amino groups of chitosan with coupling reagents bearing thiol functions leads to the formation of thiolated chitosans. So far, three types of thiolated chitosans have been generated: chitosan-cysteine conjugates, chitosan-thioglycolic acid conjugates and chitosan-4-thio-butyl-amidine conjugates. Various properties of chitosan are improved by this immobilization of thiol groups. Due to the formation of disulfide bonds with mucus glycoproteins, the mucoadhesiveness is 6--100-fold augmented (I). The permeation of paracellular markers through intestinal mucosa can be enhanced 1.6--3-fold utilizing thiolated instead of unmodified chitosan (II). Moreover, thiolated chitosans display in situ-gelling features, due to the pH-dependent formation of inter- as well as intra-molecular disulfide bonds (III). This latter process provides a strong cohesion and stability of carrier matrices being based on thiolated chitosans (IV). Consequently, thiolated chitosans can guarantee a prolonged controlled release of embedded therapeutic ingredients (V). The potential of thiolated chitosans has meanwhile also been demonstrated in vivo. A significant pharmacological efficacy of 1.3% of orally given salmon calcitonin, for instance, could be achieved utilizing thiolated chitosan as polymeric drug carrier matrix, while no effect was reached using unmodified chitosan. According to these results thiolated chitosans represent a promising new category of polymeric excipients in particular for the non-invasive administration of hydrophilic macromolecules. Further applications such as their use as scaffold materials in tissue engineering or as coating material for stents seem feasible.

Animals↗

PubMed2003

Electrochemical behavior and detection of hepatitis B virus DNA PCR production at gold electrode.

Sequence-known short-stranded hepatitis B virus (HBV) DNA fragment (181 bps) was obtained by PCR method. The strategy for its electrochemical detection was designed by covalently immobilizing single-stranded HBV DNA on gold electrode surface via carboxylate ester as a linkage between 3'-hydroxy end of DNA and carboxyl group of thioglycolic acid (TGA) self-assembled monolayer. The hybridization reaction on surface was evidenced by electrochemical methods using ferrocenium hexafluorophosphate (FcPF6) as an electroactive indicator. The interactions of Fc+ with single-stranded (ss) and double-stranded (ds) HBV DNA immobilized on TGA monolayer were studied. The difference between the responses of Fc+ at ss- and ds-DNA/Au electrodes suggested that this hybridization biosensor could be conveniently used to monitor DNA hybridization with a high sensitivity. AC impedance and XPS techniques have been employed to characterize the immobilization of ss-DNA on the gold surface.

Adsorption↗

PubMed2003

Kinetics of DNA binding with chloroquine phosphate using capacitive sensing method.

The capacitive sensing method has been applied to study the binding of DNA with chloroquine phosphate. DNA was immobilized on a gold electrode surface, self-assembled with thioglycolic acid. The results of a quartz crystal impedance (QCI) study indicate that the reaction of double-strand DNA (dsDNA) with chloroquine includes a fast electrostatic attraction and a slow intercalation of chloroquine into double-strand helix. The real-time experimental data obtained by capacitive sensing also revealed two distinctive kinetics stages during binding of dsDNA with chloroquine, while only one stage exists during reaction of single-strand DNA (ssDNA) with chloroquine. The kinetic parameters were obtained by fitting the real-time experimental data using a two stage reaction model. The rate constants of electrostatic attraction for dsDNA and ssDNA are estimated as 0.014 and 0.018 s(-1), respectively. The rate constant of the second stage of dsDNA is 0.0011 s(-1).

Adsorption↗

PubMed2003

The use of chemically modified and unmodified cassava waste for the removal of Cd, Cu and Zn ions from aqueous solution.

The use of different chemically modified cassava waste biomass for the enhancement of the adsorption of three metal ions Cd, Cu and Zn from aqueous solution is reported in this paper. Treating with different concentrations of thioglycollic acid modified the cassava waste biomass. The sorption rates of the three metals were 0.2303 min(-1) (Cd(2+)), 0.0051 min(-1) (Cu(2+)), 0.0040 min(-1) (Zn(2+)) and 0.109 min(-1) (Cd(2+)), 0.0069 min(-1) (Cu(2+)), 0.0367 min(-1) (Zn(2+)) for 0.5 and 1.00 M chemically modified levels, respectively. The adsorption rates were quite rapid and within 20-30 min of mixing, about 60-80% of these ions were removed from the solutions by the biomass and that chemically modifying the binding groups in the biomass enhanced its adsorption capacity towards the three metals. The results further showed that increased concentration of modifying reagent led to increased incorporation, or availability of more binding groups, in the biomass matrix, resulting in improved adsorptivity of the cassava waste biomass. The binding capacity study showed that the cassava waste, which is a serious environmental nuisance, due to foul odour released during decomposition, has the ability to adsorb trace metals from solutions.

Adsorption↗

PubMed1981

Ornithine decarboxylase from calf liver. Purification and properties.

Ornithine decarboxylase (ODC) was purified 25000-fold from calf liver to apparent homogeneity by methods developed to circumvent the lability of the enzyme. Appropriate ratios of sample protein applied to column size and/or gradient size were derived for each purification procedure (ion-exchange, gel filtration ahd hydroxylapatite chromatography, electrophoresis, and thiol affinity chromatography) to maintain enzymatic activity. The enzyme was labile to dilution at all steps of the purification; the inclusion of poly(ethylene glycol) or additional protein decreased but did not eliminate the activity loss. The purified enzyme had a Stokes radius of 3.14 and a molecular weight of 54000. The Km for ornithine was 0.12 mM, and pyridoxal phosphate was 2.0 microM; the pH optimum for the decarboxylation reaction was 7.0. Analysis by sievorptive ion-exchange chromatography indicated the presence of three ionic forms. In the presence of Tris-barbital buffer containing thioglycolic acid, the ODC preparation assumed an apparent molecular weight of 100000 and a Stokes radius of 4.5 and retained full catalytic activity.

Animals↗

PubMed2005

Oxidation of thioglycolate by [Os(phen)3]3+: an unusual example of redox-mediated aromatic substitution.

The aqueous oxidation of thioglycolic acid (TGA) by [Os(phen)(3)](3+) (phen = 1,10-phenanthroline) is catalyzed by traces of ubiquitous Cu(2+) and inhibited by the product [Os(phen)(3)](2+). In the presence of dipicolinic acid (dipic), which thoroughly masks trace Cu(2+) catalysis, and spin trap PBN, the kinetics under anaerobic conditions have been studied in the pH range 1.82-7.32. The rate law is -d[Os(phen)(3)(3+)]/dt = k[TGA](tot)[Os(phen)(3)(3+)], with k = 2{(k(b)K(a1) + k(c)K(a1)K(i))[H(+)] + k(d)K(a1)K(a2)}/{[H(+)](2) + K(a1)[H(+)] + K(a1)K(a2)}; K(a1) and K(a2) are the successive acid dissociation constants of TGA, and K(i) is the tautomerization constant of two TGA monoanions. k(b) + k(c)K(i) = (5.9 +/- 0.3) x 10(3) M(-)(1) s(-)(1), k(d) = (1.6 +/- 0.1) x 10(9) M(-)(1) s(-)(1) at mu = 0.1 M (NaCF(3)SO(3)) and 25 degrees C. The major products in the absence of spin traps are dithiodiglycolic acid, [Os(phen)(3)](2+), and [Os(phen)(2)(phen-tga)](2+), where phen-tga is phenanthroline with a TGA substituent. A mechanism is proposed in which neutral TGA is unreactive, the (minor) thiolate form of the TGA monoanion undergoes one-electron oxidation by [Os(phen)(3)](3+) (k(c)), and the dianion of TGA likewise undergoes one-electron oxidation by [Os(phen)(3)](3+) (k(d)). The Marcus cross relationship provides a good account for the magnitude of k(d) in this and related reactions of TGA. [Os(phen)(2)(phen-tga)](2+) is suggested to arise from a post-rate-limiting step involving attack of the TGA(*) radical on [Os(phen)(3)](3+).

Journal Article↗

PubMed2006

CNT-CdTe versatile donor-acceptor nanohybrids.

Single wall carbon nanotubes (SWNT) and multiwall carbon nanotubes (MWNT) were linked to thioglycolic acid (TGA)-capped CdTe nanoparticles (NP) through electrostatic interactions producing photoactive superstructures. The novel nanohybrids were characterized both in the ground and excited states with specific accent on electron-transfer chemistry. In fact, both assays provide kinetic and spectroscopic evidence that support a partial transfer of charge density, with rapid formation of microsecond-lived radical ion pair states. Since nanotubes provide a quick transportation route of charge carriers to the electrode, we took this remarkable finding further and constructed photoelectrochemical cells. Photocurrents were generated through the implementation of CdTe and SWNT or MWNT, which serve as excited-state electron donor components and electron acceptors, respectively.

Journal Article↗

PubMed2006

Manipulation of aqueous growth of CdTe nanocrystals to fabricate colloidally stable one-dimensional nanostructures.

The present article is devoted to systematically exploring the influence of various experimental variables, including the precursor concentration, the ligand nature, the counterion type, the Cd-to-Te molar ratio, pH, and temperature, on the aqueous growth of CdTe nanocrystals. The growth may be divided into two stages: the early fast growth stage and the later slow growth stage. The later stage is found to be dominated by Ostwald ripening (OR), being strongly dependent on all experimental conditions. In contrast, the early stage is dominated by adding monomers to nanocrystals, which may be dramatically accelerated by lowering precursor concentrations and using ligands with a molecular structure similar to that of thioglycolic acid (TGA). This fast growth stage is similar to that observed during organometallic growth of nanocrystals in hot organic media. On the basis of this finding, one-dimensional wurtzite CdTe nanostructures can be directly prepared in aqueous media by storing rather dilute precursor solution (2.4 mM with reference to ligand) in the presence of TGA at lower temperature (from room temperature to 80 degrees C). A low growth temperature is used to suppress OR during crystal growth. In addition, the simultaneous presence of both TGA-like ligand and 1-thioglycerol or 2-mercaptoethylamine leads to formation of colloidally stable 1D CdTe nanostructures with controlled aspect ratios.

Journal Article↗

PubMed2002

Hydrogen peroxide is required for poly(phenolic) domain formation during wound-induced suberization.

The requirement for hydrogen peroxide (H(2)O(2)) during suberization was demonstrated in wound-induced potato tubers by monitoring the extent of phenolic polymerization after the inhibition of H(2)O(2) production using diphenyleneiodonium (DPI). In DPI-treated tissues the extent of phenolic polymerization in suberized tissues, measured using DFRC (Derivatization Followed by Reductive Cleavage) and thioglycolic acid analyses, was greatly reduced relative to untreated controls. Concomitantly, a large quantity of new soluble phenolics accumulated in the DPI-treated tissue some of which were not present in the controls. We suggest that the inhibition of H(2)O(2) production prevented these phenolics from being oxidized by cell wall peroxidases. As a result, these phenolics were left unpolymerized and accumulated in the tissue. Several of the soluble phenolics were identified as hydroxycinnamic acid derivatives. From the data presented, it was concluded that H(2)O(2) is required for the polymerization step in the formation of the poly(phenolic) domain of suberized potato tubers.

Chromatography, High Pressure Liquid↗

PubMed1992

A new, general synthetic route to multidentate N,S ligands for use in technetium-99m radiopharmaceuticals. Preparation of diamido disulfur, diamino dithiol, and tripodal N3S3 prototypes. Comparative biodistributions of [99mTcvO-DADS]- analogues which contain 5,5,5- and 5,7,5-membered chelate ring systems.

A new, versatile synthetic route to a variety of tetradentate N2S2 and hexadentate N3S3 ligands for use in technetium-99m radiopharmaceuticals has been developed. The key reaction employs 1-(ethoxycarbonyl)-2-ethoxy-1,2-dihydroquinoline (EEDQ) for coupling an appropriate di- or triamine with S-protected thioglycolic acid. Selected DADS (diamido disulfur) and DADT (diamino dithiol) and analogues derived from ethanediamine-1,2 and butanediamine-1,4, as well as a tripodal N3S3 analogue, were synthesized in high yield. The labeling of DADS analogue ligands derived from butanediamine-1,4 (DADS-bn) with 99mTc results in a single radiochemical product, or the expected number of stereoisomeric products. FAB MS analysis, using 99Tc, indicates that DADS-bn ligands form a tetradentate 5,7,5-membered ring chelate system with the monooxo Tc(V) core: [TcO-DAD-bn]-. In rat biodistribution studies the DADS-en and DADS-bn complexes show very similar biological activity. Phenyl substituents on the 7-membered ring give rise to a 99mTc complex of increased lipophilicity, increased liver uptake, and minimal hepatobillary clearance. Thus, new classes of DADS ligand analogues which contain a 5,7,5-membered chelate ring system are readily synthesized and labeled with 99mTc to form stable complexes. The presence of the 7-membered chelate ring allows for facile introduction of pendant groups into the ligand system, and thus for a ready route to control the biodistribution of the resulting 99mTc radiopharmaceutical. The 99mTc labeling of the DADT analogues derived from butanediamine-1,4 provided to be erratic, despite the use of a variety of labeling techniques; the larger ring system of DADT-bn apparently does not favor the monooxo Tc(V) core and appears to generate a mixture of mono- and dioxo Tc(V) cores.

Amides↗