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Stable and general-purpose chemiluminescent detection system for horseradish peroxidase employing a thiazole compound enhancer and some additives.

A stable and highly sensitive chemiluminescent detection system for horseradish peroxidase (HRP)/luminol/hydrogen peroxide using a newly designed thiazole compound enhancer has been established. Some additives for the chemiluminescent reaction were explored to overcome some defects of the reaction such as rapid decay and high background of light emission. Recrystallization of luminol and the addition of several detergents into the reacting solution were effective to increase specific light emissions. The addition of skim milk into the reacting solution reduced the background. Consequently, skim milk combined with a detergent increased the signal to noise ratio about 20 times compared with the reactions in the absence of both additives. The optimal concentration of enhancer and the addition of egg albumin stabilized the emission. In the new method, 6x 10(-18) mol of HRP was detectable. This would be the most sensitive enhanced chemiluminescent detection system for HRP. Furthermore, we could detect picogram per milliliter (10(-17) mol) concentrations of a trace component in biological materials such as endothelin-1 by employing this reaction.

Endothelins↗

Light-up probes: thiazole orange-conjugated peptide nucleic acid for detection of target nucleic acid in homogeneous solution.

We have constructed light-up probes for nucleic acid detection. The light-up probe is a peptide nucleic acid (PNA) oligonucleotide to which the asymmetric cyanine dye thiazole orange (TO) is tethered. It combines the excellent hybridization properties of PNA and the large fluorescence enhancement of TO upon binding to DNA. When the PNA hybridizes to target DNA, the dye binds and becomes fluorescent. Free probes have low fluorescence, which may increase almost 50-fold upon hybridization to complementary nucleic acid. This makes the light-up probes particularly suitable for homogeneous hybridization assays, where separation of the bound and free probe is not necessary. We find that the fluorescence enhancement upon hybridization varies among different probes, which is mainly due to variations in free probe fluorescence. For eight probes studied the fluorescence quantum yield at 25 degrees C in the unbound state ranged from 0.0015 to 0.08 and seemed to depend mainly on the PNA sequence. The binding of the light-up probes to target DNA is highly sequence specific and a single mismatch in a 10-mer target sequence was readily identified.

Base Pair Mismatch↗

Structure-activity relationship of nitroimidazo (2,1-b) thiazoles in the Salmonella mutagenicity assay.

The mutagenic activity of a series of nitroimidazo (2,1-b) thiazoles was determined in Salmonella typhimurium TA-100 strain by means of the Ames test. A multiple regression analysis showed a highly significant parabolic relationship between mutagenic activity and the Rm values as an expression of the lipophilic character of molecules. The lipophilic character should be important in determining an optimal cell permeation. However when the lipophilic character was expressed by means of the sigma pi values the equation was much less satisfactory. This could be due to the fact that the Rm values of nitroheterocyclic compounds actually represent a measure both of lipophilic and polar character.

Mutagenicity Tests↗

Effects of a new 1,3-thiazole derivative ZSY-39 on force of contraction and cyclic AMP content in canine ventricular muscle.

A newly synthesized 1,3-thiazole derivative ZSY-39 increased the force of contraction in a concentration-dependent manner in association with elevation of tissue cyclic AMP levels in the isolated canine ventricular trabeculae electrically driven at 0.5 Hz at 37 degrees C. ZSY-39 shortened the duration of isometric contractions mainly by abbreviation of the relaxation time. The maximal response to and EC50 of ZSY-39 were 0.7 (isoproterenol = 1.0) and 4.6 x 10(-5) M. Bupranolol (3 x 10(-7) M) did not affect the positive inotropic effect of ZSY-39. The time course of increases in the force of contraction induced by ZSY-39 (10(-4) M) coincided with that of cyclic AMP accumulation. The concentration-response curve for the increase in the force of contraction produced by ZSY-39 was superimposable on that of the elevation of cyclic AMP levels. Carbachol (3 x 10(-6) M) shifted the concentration-response curve for the increase in force by ZSY-39 to the right and downward, and decreased the accumulation of cyclic AMP induced by ZSY-39 (10(-4) M). ZSY-39 (10(-5) M) enhanced significantly the positive inotropic effect of isoproterenol. The relationship between the force of contraction and cyclic AMP levels after the administration of ZSY-39 was not modified by the addition of carbachol or isoproterenol. These findings indicate that cyclic AMP plays an important role in the positive inotropic effect of ZSY-39 on canine ventricular muscle.

Animals↗

Influence of urea-equivalent groups in position 5 of 2-amino, 2-(1-aminoethylidenamino) and 2-guanidino thiazole derivatives on H2-receptor antagonist activity in gastric fistula cat.

A series of thiazole derivatives, in which a side-chain with different urea-equivalent groups was introduced in position 5 of the heterocycle, have been tested as inhibitors of dimaprit-induced gastric acid and pepsin secretion in the gastric fistula cat. By comparing the in vivo and the previously reported in vitro activity of these compounds, we can note a very close parallelism not only in the quality of their action but also in the estimates of pA2 values. These data support an interdependence between the molecular substructures and the affinity for the H2-receptor.

Animals↗

The transport of a hepatoprotective agent, isopropryl 2-(1-3-dithiethane-2-ylidene)-2[N-(4-methyl-thiazole-2-yl) carbamoyl] acetate (YH439), across Caco-2 cell monolayers.

Isopropryl 2-(1-3-dithiethane-2-ylidene)-2[N-(4-methyl-thiazole-2-yl) carbamoyl] acetate (YH439) is currently under phase II clinical trials by the Yuhan Research Center for use as a hepatoprotective agent. Unfortunately, the oral bioavailbility of YH439, which is sparingly soluble in water (i.e., 0.3 microg/ml or 0.91 microM at room temperature), reportedly, is negligible regardless of the dose administered to rats in the 10-300 mg/kg range. The bioavailability of the compound increased up to 24%, when administered in the form of a micellar solution (700 microg/ml or 2.1 mM for YH439) at a dose of 10 mg/kg, suggesting that its limited solubility is associated with its negligible bioavailability. In order to obtain additional information concerning the bioavailability of YH439, the mechanism(s) involved in gastrointestinal (GI) absorption were investigated in the present study. For this purpose, the transport of YH430 across a Caco-2 cell monolayer was measured in a Transwell. A permeability of 4.07 x 10(-5) cm/s was obtained for the absorptive (i.e., apical to basolateral direction) transport of 0.42 pM YH439, implicating that the in vivo GI absorption is nearly complete. The absorptive transport exhibited a slight concentration-dependency with an intrinsic clearance (CLi) of 0.38 microLL/cm2/sec, which accounted for 28.1% of the total intrinsic clearance (i.e., CLi plus the intrinsic clearance for the linear component) of the transport. Thus, saturation of the absorption process appears to be a minor factor in limiting the bioavailability of the compound. The apparent permeability of YH439 from the basolateral to the apical direction (i.e., efflux, 6.67 x 10(-5) cm/s) was comparable to that for absorptive transport, but, interestingly, a more distinct concentration-dependency was observed for this transport. However, the efflux does not appear to influence the bioavailability of the compound, as evidenced by the sufficiently high permeability in the absorption direction. Rather, a reportedly extensive first-pass hepatic metabolism appears to be a principal factor in limiting the bioavailability. In this respect, reducing the first-pass metabolism by some means would lead to a higher bioavailability of the compound. Thus, elevation of the absorption rate of YH439 becomes a necessity. From a practical point of view, increasing the concentration of YH439 in the GI fluid appears to be a feasible way to increase the absorption rate, because the compound is primarily absorbed via a linear mechanism. In summary, the solubilization of YH439, as previously demonstrated for a micellar solution of the compound, appears to be a practical way to increase the oral bioavailability of YH439.

Biological Availability↗

Synthesis of heterocyclic quinones containing bridgehead nitrogen atom from 2-aminonaphtho[2,3-d]thiazole-4,9-dione.

Imidazonaphthothiazole derivatives 3-6 were prepared by treatment of 2-aminonaphtho[2,3-d]-thiazole-4,9-dione(1) with phenacyl bromide, chloroacetic acid, diethyl oxalate and 2,3-dichloroquinoxaline respectively. The reaction of 1 with ethyl acrylate, ethyl acetoacetate and diethyl malonate gave the corresponding naphthothiazolopyrimidine derivatives 8-11.

Antifungal Agents↗

Exploring 3D-QSAR of thiazole and thiadiazole derivatives as potent and selective human adenosine A3 receptor antagonists+.

Binding affinity data [Bioorg Med Chem (2004) 12:613-623] of thiazole and thiadiazole derivatives (n = 30) for the human adenosine A3 receptor subtype have been subjected to 3D-QSAR (Quantitative structure-activity relationships) analyses by molecular shape analysis (MSA) and molecular field analysis (MFA) techniques using Cerius2 Version 4.8. In the case of the MSA, the major steps were (1) generation of conformers and energy minimization; (2) hypothesizing an active conformer (global minimum of the most active compound); (3) selecting a candidate shape-reference compound (based on the active conformation); (4) performing pairwise molecular superimposition using the maximum common subgroup (MCSG) method; (5) measuring molecular shape commonality using MSA descriptors; (6) determining other molecular features by calculating spatial, electronic and conformational parameters; (7) selection of conformers; (8) generation of QSAR equations by genetic function algorithm (GFA) or stepwise regression. The best 3D-QSAR equation (MSA) obtained from GFA technique shows 70.0% predicted variance (leave-one-out) and 77.7% explained variance. This equation shows the importance of Jurs descriptors (atomic charge weighted positive surface area, relative negative charge and relative positive charge surface area), partial moment of inertia, energy of the most stable conformer and the ratio of common overlap steric volume to volume of individual molecules. In the case of stepwise regression, the best relation showed 46.1% predicted variance and 72.3% explained variance. In the case of MFA, the major steps were (1) generating conformers and energy minimization; (2) matching atoms using a maximum common substructure (MCS) search and aligning molecules using the default options; (3) setting MFA preferences (rectangular grid with 2 A step size, charges by the Gasteiger algorithm, H+ and CH3 as probes); (4) creating the field; (5) analysis by the Genetic partial least squares (G/PLS) method. The equation obtained was of excellent statistical quality: 96.1% explained variance and 71.6% predicted variance. Statistically reliable 3D-QSAR models obtained from this study suggest that these techniques could be useful to design potent A3 receptor antagonists.

Adenosine A3 Receptor Antagonists↗

Fluorescence resonance energy transfer and complex formation between thiazole orange and various dye-DNA conjugates: implications in signaling nucleic acid hybridization.

Fluorescence resonance energy transfer (FRET) was investigated between the intercalating dye thiazole orange (TO), and the dyes Cyanine 3 (Cy3), Cyanine 5 (Cy5), Carboxytetramethyl Rhodamine (TAMRA), Iowa Black FQ (IabFQ), and Iowa Black RQ (IabRQ), which were covalently immobilized at the end of dsDNA oligonucleotides. In addition to determining that TO was an effective energy donor, FRET efficiency data obtained from fluorescence lifetime measurements indicated that TO intercalated near the middle of the 19mer oligonucleotide sequence that was used in this study. Discrepancies in FRET efficiencies obtained from intensity and lifetime measurements led to the investigation of non-fluorescent complex formation between TAMRA and modified TO. The hydrophobicity of TO was modified by the addition of either an alkyl or polyethylene glycol (PEG) side-chain to study effects of dimer and aggregate formation. It was found that at stoichiometric excesses of modified TO, fluorescence quenching of TAMRA was observed, and that this could be correlated to the hydrophobicity of a TO-chain species. The TAMRA:TO-chain association constant for the TO-alkyl system was 0.043+/-0.002 M(-1), while that obtained for the TO-PEG was 0.037+/-0.002 M(-1). From the perspective of method development for the transduction of hybridization events, we present and evaluate a variety of schemes based on energy transfer between TO and an acceptor dye, and discuss the implications of complex formation in such schemes.

Biosensing Techniques↗

PAF binding sites. Characterization by [3H]52770 RP, a pyrrolo[1,2-c]thiazole derivative, in rabbit platelets.

52770 RP, the N-(3-chlorophenyl)-3-(3-pyridinyl)-1H,3H-pyrrolo[1,2-c]thiazole -7-carboxamide, displaces in a potent, specific and competitive manner [3H]PAF from its binding sites on rabbit platelets. Since 52770 RP is not structurally related to PAF and has low liposolubility with respect to PAF, it was selected as a potential radioligand for PAF receptor sites. [3H]52770 RP displayed high-affinity, specificity, as well as saturable and displaceable binding to a single class of recognition sites in intact platelets and crude platelet membranes. In these preparations, the values of binding parameters were, respectively, 8.5 and 7.6 nM for Kd, 0.2 pmol/5 X 10(7) platelets and 3.66 pmol/mg protein for Bmax and 0.96 and 0.91 for nH. Inasmuch as the (+)-52770 RP was 300-fold more potent than the (-)-isomer at displacing [3H]52770 RP in intact platelets, the studied binding site manifested stereospecific discrimination. A variety of pharmacological agents including pro- and anti-aggregant compounds did not exhibit affinity for [3H]52770 RP binding sites. In contrast, PAF, some of its active analogues and several recognized PAF antagonists (BN 52021, brotizolam, L-652,731, triazolam), displaced the [3H]52770 RP binding. Studies carried out using [3H]PAF demonstrated that 52770 RP was approximately 4- and 200-fold more potent than L-652,731 and BN 52021 respectively, as a PAF-receptor antagonist. In washed rabbit platelets, the rank order of potency (Ki) for several analogues of 52770 RP, to displace [3H]PAF from its binding sites, was highly correlated (r = 0.96) to their ability to antagonize [3H]52770 RP binding. In functional studies, 52770 RP antagonized not only the PAF-induced aggregation in washed rabbit platelets but also the hypotension evoked by PAF in the anesthetized rat. In this respect, it was 26 and 2 times more potent than L-652,731, respectively. In conclusion, [3H]52770 RP might represent a novel interesting tool for furthering our understanding of the role of PAF binding sites in pathophysiological processes.

Animals↗

Synthesis of thiazole-4-carboxamide-adenine difluoromethylenediphosphonates substituted with fluorine at C-2' of the adenosine.

Synthesis of an analogue 3 of thiazole-4-carboxamide adenine-dinucleotide (TAD) in which the beta-oxygen atom of the pyrophosphate bridge is replaced by a difluoromethylene group has been achieved. Likewise, 2'-deoxy-2'-fluoroadenosine containing analogues of TAD (4) and its difluoromethylenediphosphonate congener (5) have been synthesized. Adenosine 5'-difluoromethylenediphosphonate (8) was prepared from 5'-O-tosyladenosine (6) and tris(tetra-n-butylammonium)difluoromethylenediphosphonate (7) by a modified procedure of Poulter's. Compound 8 was converted into the 2',3'-cyclic carbonate 9 by treatment with triethyl orthoformate. Treatment of 9 with 2',3'-O-isopropylidenetiazofurin (10) in pyridine in the presence of DCC gave a mixture of dinucleotide 11 and the isopropylidene-protected diadenosine tetraphosphonate 12. After deprotection of 11, the desired beta-difluoromethylene TAD (3) was separated by HPLC as the minor product. The diadenosine tetraphosphonate 12, an analogue of Ap4A, was obtained as the major component. Alternatively, 2',3'-O-isopropylidenetiazofurin (10) was tosylated, and the product 13 was further converted into the corresponding difluoromethylenediphosphonate 14 by coupling with 7. DCC-catalyzed coupling of 14 with 2'-deoxy-2'-fluoroadenosine (15) followed by deisopropylidenation afforded the analogue 5. Again the corresponding tetraphosphonate analogue of tiazofurin 17 was the predominant product. Dinucleotide 4 was obtained by coupling of the carbonyldiimidazole-activated tiazofurin 5'-monophosphate with 2'-deoxy-2'-fluoroadenosine 5'-monophosphate. 2'-Deoxy-2'-fluoroadenosine (15) was prepared efficiently from the known N6-benzoyl-3'-O-tetrahydropyranyladenosine (18), which was converted into 3'-O-tetrahydropyranyl-2'-O-triflyl-5'-O-trityladenosine (20) by tritylation and triflation. Treatment of 20 with sodium acetate in hexamethylphosphoric triamide, followed by deacetylation afforded 9-(3-O-tetrahydropyranyl-5-O-trityl-beta-D- arabinofuranosyl)-N6-benzoyladenine (22), which was then treated with DAST. After deprotection of the product, 15 was obtained in good yield.

Adenine Nucleotides↗

Potential antitumor agents. XX (1). 6-Anilinoimidazo[2,1-b]thiazoles.

The synthesis of 6-anilinoimidazo[2,1-b]thiazoles, related to the well-known antitumor agent amsacrine, is reported. The cytotoxic activity of the new compounds was evaluated on HeLa cells. Compound 3a, the most closely related to amsacrine, was significantly active.

Antineoplastic Agents↗

Suppression of murine collagen-induced arthritis by treatment with a novel thiazole derivative, SM-8849.

The antiarthritic activity of a novel thiazole derivative, SM-8849, was compared with that of indomethacin and D-penicillamine, in mice with collagen-induced arthritis. SM-8849 reduced the incidence and severity of disease in collagen-immunized mice, as assessed by clinical observation. This efficacy was also confirmed by radiographic and histologic studies. Indomethacin produced an apparent reduction of the clinical score, but had only a marginal effect on bone destruction. D-penicillamine did not produce any improvement. Unlike indomethacin and D-penicillamine, SM-8849 reduced the serum levels of anti-type II collagen antibodies. Flow cytometric analysis of spleen cells from arthritic mice revealed an increase in T cells expressing activation antigens (class II antigens) in comparison with normal mice. Treatment with SM-8849, but not indomethacin or D-penicillamine, prevented the increase in Ia-bearing T cells. The results suggest that an effect of SM-8849 on immunocompetent cells may be responsible for the antiarthritic activity of the compound, and this would distinguish its action from that of traditional antirheumatic drugs.

Animals↗

Mutagenicity of urine of various species fed N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide or 2-amino-4-(5-nitro-2-furyl)thiazole.

Rats, mice and hamsters, which are susceptible to the bladder carcinogenesis by N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide (FANFT), and guinea pigs, which are not, were fed a diet containing 0.188% FANFT or 0.188% 2-amino-4-(5-nitro-2-furyl)thiazole (ANFT) for 1 week and their urine was then examined for mutagenicity for S. typhimurium TA100. The mutagenicities of the urine of these species fed FANFT were approximately equal. Similarly, that of the urine of these species fed ANFT were also approximately equal. However, the urine from FANFT-fed animals was approximately 10 times as mutagenic as that from ANFT-fed animals. ANFT was detected only in the urine of rats, mice or hamsters fed FANFT. A positive correlation between the susceptibility toward bladder carcinogenesis by FANFT and urinary ANFT excretion was demonstrated, although the correlation between this susceptibility and urine mutagenicity was lacking.

Animals↗

Protective effects of D-penicillamine and a thiazole derivative, SM-8849, on pristane-induced arthritis in mice.

To evaluate the antiarthritic properties of a novel thiazole derivative, the drugs SM-8849, D-penicillamine and indomethacin were administered to pristane-injected DBA/1 mice. The mice were treated daily with the agents for 32 weeks, starting from the day of the pristane injection. Treatment with SM-8849 (50 mg/kg) resulted in an amelioration of arthritic disease, as assessed by clinical, radiographic, and histologic examinations. Similar results were obtained in mice treated with 50 mg/kg D-penicillamine, although this disease modifying antirheumatic drug was slightly less effective than the same dose of SM-8849. In contrast, indomethacin at the maximum tolerated dose of 2 mg/kg did not alter the course of the disease. SM-8849 and D-penicillamine were also shown to reduce serum levels of rheumatoid factors and the acute-phase reactant, serum amyloid P component. Indomethacin failed to affect either parameter. Flow cytometric analysis revealed an elevation in the T-cell population that expressed CD44, a marker of murine memory T-cells, in spleens from pristane-injected mice. SM-8849, but not D-penicillamine, prevented the increase in this cell population. These results led us to conclude that pristine-induced arthritis was a useful model for the evaluation of antirheumatic agents, in that using this model, we were able to distinguish disease modifying antirheumatic drugs from nonsteroidal anti-inflammatory drugs. Our findings also indicate that SM-8849 shows antiarthritic activity, with a unique mechanism of action, differing from that of D-penicillamine.

Adjuvants, Immunologic↗

Vitamin B1 thiazole derivative reduces transmembrane current through ionic channels formed by toxins from black widow spider venom and sea anemone in planar phospholipid membranes.

The vitamin B1 (thiamine) structural analogue 3-decyloxycarbonylmethyl-4-methyl-5-(beta-hydroxyethyl) thiazole chloride (DMHT) (0.1 mM) reversibly reduced transmembrane currents in CaCl2 and KCl solutions via ionic channels produced by latrotoxins (alpha-latrotoxin (alpha-LT) and alpha-latroinsectotoxin (alpha-LIT)) from black widow spider venom and sea anemone toxin (RTX) in the bilayer lipid membranes (BLMs). Introduction of DMHT from the cis-side of BLM bathed in 10 mM CaCl2 inhibited transmembrane current by 31.6+/-3% and by 61.8+/-3% from the trans-side of BLM for alpha-LT channels. Application of DMHT in the solution of 10 mM CaCl2 to the cis-side of BLM decreased the current through the alpha-LIT and RTX channels by 52+/-4% and 50+/-5%, respectively. Addition of Cd2+ (1 mM) to the cis- or trans-side of the membrane after the DMHT-induced depression of Ca2+-current across the alpha-LT channels caused its further decrease by 85+/-5% that coincides favorably with the intensity of Cd2+ blocking in control experiments without DMHT. These data suggest that DMHT inhibiting is not specific for latrotoxin channels only and DMHT may exert its action on alpha-LT channels without considerable influence on the ionogenic groups of Ca2+-selective site inside the channel cavity. The binding kinetics of DMHT with the alpha-LT channel shows no cooperativity and allows to expect that the DMHT binding site of the toxin is formed by one ionogenic group as the slopes of inhibition rate determined in log-log coordinates are 1.25 on the trans-side and 0.68 on the cis-side. Similar pK of binding (5.4 on the trans-side and 5.7 on the cis-side) also suggest that DMHT may interact with the same high affinity site of alpha-LT channel on either side of the BLM. The comparative analysis of effective radii measured for alpha-LT, alpha-LIT and RTX channels on the cis-side (0.9 nm, 0.53 nm and 0.55 nm, correspondingly) and for alpha-LT channel on the trans-side (0.28+/-0.18 nm) with the intensity of DMHT inhibitory action obtained on these channels allowed to conclude that the potency of DMHT inhibition increased on toxin pores of smaller lumen.

Animals↗

Exploring QSAR of thiazole and thiadiazole derivatives as potent and selective human adenosine A3 receptor antagonists using FA and GFA techniques.

Binding affinity data of thiazole and thiadiazole derivatives (n=30) for human adenosine A3 receptor subtype have been subjected to Quantitative Structure-Activity Relationship (QSAR) analysis using quantum chemical and hydrophobicity parameters. Wang-Ford charges of the common atoms of the compounds [calculated from molecular electrostatic potential surface of energy minimized geometry using Austin Model 1 (AM1) technique] were used as independent variables apart from partition coefficient (logP) and suitable dummy parameters. The variables for the multiple regression analyses were selected based on principal component factor analysis (FA), and generated equations were statistically validated using leave-one-out technique. The best equation thus obtained explained and predicted 74.4% and 68.9% respectively of the variance of the binding affinity. The results suggested importance of Wang-Ford charges of atoms C2, C5 and C7. Furthermore, the A3 binding affinity increases with decrease of lipophilicity of the compounds and in the presence of methyl or ethyl substituent at R position. Again, the binding affinity decreases in the presence of tert-butyloxy group at R position. When factor scores were used as predictor variables in principal component regression analysis, the resulted model showed 87.0% predicted variance and 89.5% explained variance. The data set was also modeled using genetic function approximation (GFA) technique. The best two equations derived from GFA show better predicted variance values (0.753 and 0.739) than that found in case of the best equation derived from FA. However, considerable intercorrelation was found between two predictor variables in case of GFA derived equations. GFA derived equations show importance of Wang-Ford charges of different atoms of the thiazole/thiadiazole nucleus and phenyl ring (S9, X8 and C2, the effects of the first two being predominant) along with similar impact of lipophilicity and R group on the binding affinity as found in case of the FA derived relation.

Adenosine A3 Receptor Antagonists↗