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PubMed1999

Sites of reaction of pilocarpine.

Analysis of the sites of reaction of a biologically important compound, pilocarpine, a molecule with imidazole and butyrolactone rings connected by a methylene bridge, has been accomplished in a quadrupole ion trap with the aim of characterizing its structure/reactivity relationships. Ion-molecule reactions of pilocarpine with chemical ionizing agents, dimethyl ether (DME), 2-methoxyethanol, and trimethyl borate (TMB), along with collision-activated dissociation elucidated the reaction sites of pilocarpine and made possible the comparison of structural features that affect sites of reaction. Based on MS/MS experiments, methylation occurs on the imidazole ring upon reactions with CH3OCH2+ or (CH3OCH2CH2OH)H+ ions but methylation occurs on the lactone ring for reactions with (CH3O)2B+ ions. Bracketing experiments with two model compounds, alpha-methyl-gamma-butyrolactone and N-methyl imidazole, show the imidazole ring to have a greater gas-phase basicity and methyl cation affinity than the lactone ring. The contrast of methylation by TMB ions on the lactone ring is explained by initial addition of the dimethoxyborinium ion, (CH3O)2B+, on the imidazole ring with subsequent collisional activation promoting an intramolecular transfer of a methyl group to the lactone ring with concurrent loss of CH3OBO. Semiempirical molecular orbital calculations are undertaken to further address the favored reaction sites.

Imidazoles↗
PubMed2000

Photoinduced electron transfer between C70 fullerene and 3,3',5,5'-tetramethylbenzidine studied by electron paramagnetic resonance.

Electron paramagnetic resonance (EPR) in situ spectroscopy was applied in the study of photoinduced electron transfer between 3,3',5,5'-tetramethylbenzidine (TMB) and C70 in different solvent systems. The changes found in UV-vis spectra pointed at ground state charge transfer complex formation [C70-TMB] in benzonitrile. Upon selective excitation of C70 using steady-state monochromatic irradiation with a wavelength of 546 nm, two EPR singlets were observed, which were assigned to C70 mono- and di-anion. In the photochemical and cathodic in situ reductions, identical EPR spectra of anion radicals were obtained. C70 mono-anion was investigated also in frozen 1,2-dichlorobenzene solutions within the temperature range from 110 to 210 K, and at 110 K the anisotropic EPR spectrum of C70 mono-anion was simulated assuming an axially symmetric g-matrix with gparallel - gperpendicular = 0.00165.

Benzidines↗
PubMed1996

Stoichiometric and substoichiometric inhibition of tubulin self-assembly by colchicine analogues.

The mechanism of the stoichiometric and substoichiometric inhibitions of tubulin self-assembly by several structural analogues of colchicine (COL) was investigated. The inhibition data were analyzed in terms of a simple model that takes into consideration Kg, the normal microtubule growth constant, equal to Cr-1 (Cr is the critical concentration for microtubule formation), and Kb, the binding constant of the drug to tubulin. In this manner, the value of the microtubule inhibition constant (Ki), which is the binding constant of the tubulin-drug complex to the end of a growing microtubule (which stops the microtubule growth), was determined. The results of the analysis of microtubule inhibition by the various colchicine analogues show that all the inhibitions can be expressed reasonably by this model. The strongest inhibitors found were colchicine (COL), allocolchicine (ALLO), and the biphenyl keto analogue 2,3,4-trimethoxy-4'-acetyl-1,1'-biphenyl (TKB), which had essentially identical values of Ki = (2.1 +/- 0.3) x 10(6) M(-1). MTC, the two-ring analogue of colchicine, was weaker (Ki = 5.6 x 10(5) M(-1). A most striking result was that tropolone methyl ether (TME), which is ring C of COL, and which binds very weakly to tubulin (Kb = 3.5 x 10(2) M(-1)), is a substoichiometric inhibitor. Its Ki value of 8.7 x 10(5) M(-1) makes it identical in strength to MTC, suggesting that ring A makes little or no contribution to the induction of assembly inhibition. The three biphenyls, which bind to tubulin with similar affinity, spanned the spectrum from strong substoichiometric inhibition (TKB) to stoichiometric inhibition for 2,3,4-trimethoxy-4'-carbomethoxy-1,1'-biphenyl (TCB) and an intermediate mode for the methoxy derivative 2,3,4,4'-tetramethoxy-1,1'-biphenyl (TMB). The extent of tubulin bound to drugs at 50% inhibition (r) was ca. 2% for TKB, ALLO, and COL, i.e. one liganded tubulin for every 40-50 molecules of free protein (substoichiometric). This ratio was 1:1.5 for TCB (stoichiometric) and 1:6 for TMB (intermediate). For TME, which is a single ring compound, it was 1:25. The progression of the stoichiometries varied directly with Ki and was totally unrelated to the values of Kb, which indicated the control of the stoichiometry by Ki and the close thermodynamic linkage between r and Ki. Comparison of the inhibitory capabilities of the various drugs identified the need for strong substoichiometric inhibition of a carbonyl group on ring C or C'. Furthermore, this group must be properly oriented by interaction with the protein or by the structural rigidity imparted by ring B, as in ALLO. The simple linked equilibrium model developed in this paper permits the alignment of drugs along a continuum that ranges from stoichiometric to strong substoichiometric modes of microtubule inhibition. Furthermore, it shows that the previously identified two classes are the two ends of a monotonously progressing spectrum described by a single mechanism of action.

Animals↗
PubMed2006

Atmospheric fate of dichlorvos: photolysis and OH-initiated oxidation studies.

The OH-initiated oxidation of dichlorvos (a widely used insecticide) has been investigated under atmospheric conditions at the large outdoor European photoreactor (EUPHORE) in Valencia, Spain. The rate constant of OH reaction with dichlorvos, k, was measured by using a conventional relative rate technique where 1,3,5-trimethylbenzene (TMB) and cyclohexane were taken as references. With the use of the rate constants of 5.67 x 10(-11) and of 6.97 x 10(-12) cm3 molecule(-1) s(-1) for the reactions OH + TMB and OH + cyclohexane, respectively, the resulting value of the OH reaction rate constant with dichlorvos was derived to be k = (2.6 +/- 0.3) x 10(-11) cm3 molecule(-1) s(-1). The tropospheric lifetime of dichlorvos with respect to reaction with OH radical has been estimated to be around 11 h. The major carbon-containing products observed for the OH reaction with dichlorvos in air under sunlight condition were phosgene and carbon monoxide. The formation of a very stable toxic primary product such as phosgene associated with the relatively short lifetime of dichlorvos may make the use of this pesticide even more toxic for humans when released into the atmosphere.

Atmosphere↗
PubMed2005

New phosphorescent polynuclear Cu(I) compounds based on linear and star-shaped 2-(2'-pyridyl)benzimidazolyl derivatives: syntheses, structures, luminescence, and electroluminescence.

Four dinuclear and trinuclear Cu(I) complexes that contain 2-(2'-pyridyl)benzimidazolyl derivative ligands including 1,4-bis[2-(2'-pyridyl)benzimidazolyl]benzene (1,4-bmb), 1,3-bis[2-(2'-pyridyl)benzimidazolyl]benzene (1,3-bmb), 1,3,5-tris[2-(2'-pyridyl)benzimidazolyl]benzene (tmb), and 4,4'-bis[2-(2'-pyridyl)benzimidazolyl]biphenyl (bmbp) have been synthesized. The formulas of these complexes are [Cu(2)(1,4-bmb)(PPh(3))(4)][BF(4)](2) (1), [Cu(2)(1,3-bmb)(PPh(3))(4)][BF(4)](2) (2), [Cu(3)(tmb)(PPh(3))(6)][BF(4)](3) (3), and [Cu(2)(bmbp)(PPh(3))(4)][BF(4)](2) (4), respectively. The crystal structures of 2-4 have been determined by single-crystal X-ray diffraction analyses. The Cu(I) ions in the complexes have a distorted tetrahedral geometry. For 3, two structural isomers (syn and anti) resulted from two different orientations of the three 2-(2'-pyridyl)benzimidazolyl chelating units were observed in the crystal lattice. Variable-temperature (1)H NMR experiments established the presence of syn and anti isomers for 1-3 in solution which interconvert at ambient temperature. Complexes 1-4 have a weak MLCT absorption band in the 350-450 nm region and display a yellow-orange emission when irradiated by UV light. One unexpected finding is that the yellow-orange emission of complexes 1-4 has a very long decay lifetime (approximately 200 micros) at 77 K. An electroluminescent (EL) device using 4 as the emitter and PVK as the host was fabricated. However, the long decay lifetime of the copper complexes may limit their applications as phosphorescent emitters in EL devices.

Journal Article↗
PubMed2002

A chlorine isotope effect for enzyme-catalyzed chlorination.

Several chlorinated organic compounds (COCs) that have been detected in a wide range of human, animal, and environmental samples may be derived from natural or anthropogenic sources. To determine whether the Cl isotope ratios of these compounds could be used to differentiate sources, we investigated the chlorine isotope effect for enzyme-catalyzed chlorination. Two aromatic substrates, 1,3,5-trimethylbenzene (TMB) and 3,5-dimethylphenol (DMP), were treated with a chloroperoxidase isolated from the fungus Caldariomyces fumago. A kinetic isotope effect (KIE) (in terms of k35/k37) was calculated to be 1.012 for TMB and 1.011 for DMP. A similar reaction, but not catalyzed, with hypochlorite yielded a much smaller KIE. These results indicate that a substantial KIE exists for this process. Furthermore, natural COCs synthesized by this enzymatic pathway may have Cl isotope ratios that will be easily distinguished from anthropogenic COCs.

Chloride Peroxidase↗
PubMed1994

Search for the pharmacophore of bispyridinium-type allosteric modulators of muscarinic receptors.

The bis(dichlorobenzyl) ether of the bispyridinium oxime TMB 4 stabilizes antagonist binding to M2-cholinoceptors which is indicative of an allosteric action. More than 10 derivatives of the lead compound were synthesized to investigate structure-activity relationships. The allosteric potency of the compounds was indicated by the concentrations which retarded the rate of dissociation of [3H]N-methylscopolamine from porcine cardiac cholinoceptors by a factor of 2 (EC50). Compared with TMB 4, the bis(dichlorobenzyl) derivative 4a displayed a more than 200-fold higher potency (EC50 = 4.7 microM). One of the dichlorobenzyl groups could be replaced by a methyl group without loss of activity (EC50 = 4.5 microM). Further shortening of this end of the molecule was accompanied by a moderate decline in potency to a minimum of EC50 = 26 microM. The second quaternary nitrogen was not a prerequisite for an allosteric activity. It is concluded that one half of the lead compound is pivotal for an interaction with the allosteric site of the M2-cholinoceptor, whereas the opposite end of the molecule modulates the allosteric activity.

Allosteric Regulation↗
PubMedDate not supplied

Peracylation of nucleosides with methionine: foundation for a method to detect carcinogen adducts.

We report the chemical foundation for a new method to detect carcinogen-DNA adducts, which we have designated adduct detection by acylation with methionine (ADAM). The method is based on reaction of DNA adducts with a protected methionine derivative, (tert-butoxycarbonyl)-L-methionine N-hydroxysuccinimidyl ester (TMB-NHS). Acylation of 2'-deoxyguanosine (dGuo), used as a prototypical deoxynucleoside, and N-(deoxyguanosin-8-yl)-4-aminobiphenyl (dGuo-8-ABP), the major DNA adduct formed after in vivo exposure to 4-aminobiphenyl, a known human carcinogen, with TBM-NHS was optimized, and products were characterized by 3H radioactivity, UV absorbance, mass spectrometry, and 1H and 13C NMR. Derivatives acylated on hydroxyl (5' or 3') and/or amine (N2) groups were unambiguously determined to be mono-, bis-, and tris-TBM-acylated nucleosides. Under optimal acylation conditions [TBM-NHS (> or = 4 x 10(5) molar equivalents), pyridine (50 microL), THF (50 microL), and diisopropylcarbodiimide (DIC) (1 microL) and incubation for 2 h at 37 degrees C], the efficiency of acylation for picomole or smaller quantities of dGuo-8-ABP exceeded 95%, with the tris-TMB-acylated nucleoside representing the major product (88%). A linear correlation was obtained between the amount of [3H]dGuo-8-ABP introduced into the reaction and the total amount of TBM-acylated products formed. These results support the validity of this strategy for adaptation as an analytical method for the detection of low levels of DNA adducts through the use of (tert-butoxycarbonyl)-L-[35S]-methionine N-hydroxysuccinimidyl ester.

Acylation↗
PubMed2004

Oxidation of benzidine and its derivatives by thyroid peroxidase.

Human thyroid peroxidase (hTPO) catalyzes a one-electron oxidation of benzidine derivatives by hydrogen peroxide through classical Chance mechanism. The complete reduction of peroxidase oxidation products by ascorbic acid with the regeneration of primary aminobiphenyls was observed only in the case of 3,3',5,5'-tetramethylbenzidine (TMB). The kinetic characteristics (k(cat) and K(m)) of benzidine (BD), 3,3'-dimethylbenzidine (o-tolidine), 3,3'-dimethoxybenzidine (o-dianisidine), and TMB oxidation at 25 degrees C in 0.05 M phosphate-citrate buffer, pH 5.5, catalyzed by hTPO and horseradish peroxidase (HPR) were determined. The effective K(m) values for aminobiphenyls oxidation by both peroxidases raise with the increase of number of methyl and methoxy substituents in the benzidine molecule. Efficiency of aminobiphenyls oxidation catalyzed by either hTPO or HRP increases with the number of substituents in 3, 3', 5, and 5' positions of the benzidine molecule, which is in accordance with redox potential values for the substrates studied. The efficiency of HRP in the oxidation of benzidine derivatives expressed as k(cat)/K(m) was about two orders of magnitude higher as compared with hTPO. Straight correlation between the carcinogenicity of aminobiphenyls and genotoxicity of their peroxidation products was shown by the electrophoresis detecting the formation of covalent DNA cross-linking.

Aminobiphenyl Compounds↗
PubMed2001

Prostaglandin F2alpha upregulates interleukin-6 production in human gingival fibroblasts.

Prostaglandin F2alpha (PGF2alpha) is a bioactive lipid mediator which has been suggested to be involved in the pathogenesis of periodontal disease. However, the roles of PGF2alpha in periodontal lesions are poorly understood. In the present study, we investigated the effect of PGF2alpha on interleukin (IL)-6 production in human gingival fibroblasts (HGF). PGF2alpha stimulated IL-6 production in a time- and concentration-dependent fashion. IL-1beta and tumor necrosis factor alpha (TNFalpha), proinflammatory cytokines, induced IL-6 production in a time-dependent manner, and PGF2alpha synergistically enhanced IL-6 production induced by IL-1beta and TNFalpha. IL-6 mRNA was expressed in PGF2alpha-stimulated HGF, and PGF2alpha increased IL-6 mRNA levels induced by IL-1beta and TNFalpha. Fluprostenol, a selective FP receptor agonist, could mimic PGF2alpha-induced IL-6 production. Since FP receptors are coupled to elevation of intracellular calcium and activation of protein kinase C (PKC), the mechanism of IL-6 production by PGF2alpha was investigated using TMB-8, an inhibitor of Ca2+ mobilization from intracellular stores, and calphostin C, an inhibitor of PKC. TMB-8 significantly suppressed PGF2alpha-induced IL-6 production, whereas calphostin C showed a stimulatory effect on PGF2alpha-induced IL-6 production. From these data, we suggest that PGF2alpha upregulates IL-6 production through FP receptors in HGF, that PGF2alpha synergistically enhances IL-6 production in IL-1beta- and TNFalpha-stimulated HGF, and that PGF2alpha-induced IL-6 production may be dependent on intracellular Ca2+ mobilization and be downregulated by PKC activation. PGF2alpha may be involved in the pathogenesis of periodontal disease by enhancing IL-6 levels in periodontal lesions.

Calcium↗
PubMed1994

Interferon-gamma increases cellular calcium ion concentration and inositol 1,4,5-trisphosphate formation in human renal carcinoma cells: relation to ICAM-1 antigen expression.

In the present study, we investigated the effect of interferon-gamma (IFN-gamma) on cellular calcium ion concentration [Ca2+]i and inositol 1,4,5-trisphosphate (Ins 1,4,5-P3) formation in the human renal carcinoma cell line CaKi-1. We also examined the possible role of a Ca(2+)-dependent mechanism during IFN-gamma-induced intercellular adhesion molecule 1 (ICAM-1) antigen expression. IFN-gamma caused a rapid concentration-dependent rise in [Ca2+]i, which was partly inhibited by diltiazem, a calcium channel blocker, TMB-8, an inhibitor of intracellular calcium redistribution, and in calcium-free medium. IFN-gamma caused a fourfold increase in Ins 1,4,5-P3 formation. The induction of ICAM-1 antigen expression was synergistically enhanced by 4-bromocalcium ionophore A23187. Finally, the calcium antagonists diltiazem. TMB-8 and EGTA, as well as two potent inhibitors of Ca(2+)-dependent kinases, calmidazolium (R24571) and W7, had no or only a minor inhibitory effect on IFN-gamma induction. Our data suggest that IFN-gamma increases [Ca2+]i in CaKi-1 cells by stimulating influx of Ca2+ and release of Ca2+ from intracellular stores, probably via Ins 1,4,5-P3 formation. IFN-gamma signal transduction in our model may not be limited to an increase in [Ca2+]i and Ins 1,4,5-P3, since IFN-gamma-induced ICAM-1 antigen expression was abrogated to a minor degree by calcium antagonists and not coupled to Ins 1,4,5-P3 formation.

Antigens↗
PubMed2026

Integrating germline and tumor sequencing to improve hereditary cancer diagnosis and care.

A subset of cancers arises due to inherited germline pathogenic variants in specific genes, known as hereditary cancers. These genes typically include tumor suppressors, DNA repair and replication fidelity genes, and occasionally oncogenes. In most hereditary cancer syndromes, Knudson's two-hit hypothesis applies, where a second somatic event inactivates the remaining allele of a tumor suppressor or DNA repair gene, leading to tumorigenesis. Advancements in genome-wide sequencing have significantly enhanced our understanding of the mutational processes involved in hereditary cancers. In particular, the assessment of microsatellite instability (MSI), tumor mutational burden (TMB), and mutational signatures has emerged as a powerful tool for the identification of hereditary tumors. Tumors with high or ultra-high TMB often reflect underlying DNA repair deficiencies, while specific mutational signatures can pinpoint the defective pathway. These tumor mutational features are especially informative in syndromes involving mismatch repair (MMR), homologous recombination (HR), base excision repair (BER), nucleotide excision repair (NER), and polymerase proofreading. Moreover, tumor sequencing aids in the interpretation of germline variants, identifies somatic mosaicism, and helps differentiate hereditary from sporadic cancers. Additionally, tumor molecular features associated with DNA repair deficiencies offer insights into personalized therapies, such as the use of PARP inhibitors for BRCA1/2-deficient tumors and immune checkpoint inhibitors for MMR- and polymerase proofreading-deficient cancers. Tumor profiling also uncovers actionable mutations in oncogenes like RET and VHL, which can be targeted with specific therapies. This review explores the integration of tumor molecular features with germline genetic data to refine diagnosis, risk assessment, and therapeutic strategies in hereditary cancer.

Humans↗
PubMed2002

The phospholipase C-IP3 pathway is involved in muscarinic antinociception.

The cellular events involved in muscarinic analgesia were investigated in the mouse hot-plate test. Intracerebroventricular (i.c.v.) pretreatment with antisense oligonucleotides (aODNs) against the alpha subunit of G(q) and G(11) proteins prevented the analgesia induced by physostigmine and oxotremorine. Furthermore, administration of the phospholipase C (PLC) inhibitor U-73122, as well as the injection of an aODN complementary to the sequence of PLCbeta(1), antagonized the increase of the pain threshold induced by both cholinomimetic drugs. In mice undergoing treatment with LiCl, which impairs phosphatidylinositol synthesis, or treatment with heparin, an IP(3) receptor antagonist, the antinociception induced by physostigmine and oxotremorine was dose-dependently antagonized. I.c.v. pretreatment with TMB-8, a blocker of Ca(2+) release from intracellular stores, prevented the increase of pain threshold induced by the investigated cholinomimetic drugs. Coadministration of Ca(2+) restored the muscarinic analgesia in LiCl, heparin, and TMB-8-preatreated mice. On the other hand, i.c.v. pretreatment with the selective protein kinase C (PKC) inhibitor calphostin C, resulted in a dose-dependent enhancement of physostigmine- and oxotremorine-induced antinociception. The administration of PKC activators, such as PMA and PDBu, dose dependently prevented the cholinomimetic drug-induced increase of pain threshold. Neither aODNs nor pharmacological treatments employed produced any behavioral impairment of mice as revealed by the rota-rod and hole-board tests. These results indicate a role for the PLC-IP(3) pathway in central muscarinic analgesia in mice. Furthermore, activation of PKC by cholinomimetic drugs may represent a pathway of negative modulation of muscarinic antinociception.

Analgesics↗
PubMedDate not supplied

Cytoplasmic signalling pathways in alveolar macrophages involved in the production of nitric oxide after stimulation with excretory/secretory antigens of Toxocara canis.

We studied the cytoplasmic signalling pathways involved in the generation of nitric oxide (NO) after stimulation with adult excretory/secretory antigens (ESA) of Toxocara canis. The pathways of phospholipase A2 (PLA2) and phospholipase C (PLC) were considered as potentially involved in the synthesis of nitric oxide. We used inhibitors of these pathways at different levels. Several concentrations of lithium chloride, verapamil, TMB-8 and staurosporine were used to inhibit the PLC pathway. Inhibition of the PLA2 pathway was attempted with mepacrine, diethylcarbamazine or meloxicam. Lithium chloride, verapamil and TMB-8 reduced the production of NO induced by ESA in a concentration-dependent manner. Regarding the PLA2 pathway, a range of concentrations of mepacrine greatly reduced the production of NO induced by ESA. Meloxicam inhibition was always higher than 50%. Diethylcarbamazine showed a dose-dependent effect on the production of NO induced by the ESA. Our results suggest that both the PLC and the PLA2 pathways play an essential role in activating the production of macrophage NO triggered by the ESA of T. canis. This could indicate that NO production in our experimental conditions is due to both an increase of intracellular calcium and to the participation of the arachidonic acid cascade. The implications of these activations on the host-parasite relationship are discussed and compared with LPS-stimulated macrophages.

Animals↗
PubMed1999

Involvement of inositol 1,4,5-trisphosphate-regulated stores of intracellular calcium in calcium dysregulation and neuron cell death caused by HIV-1 protein tat.

HIV-1 infection commonly leads to neuronal cell death and a debilitating syndrome known as AIDS-related dementia complex. The HIV-1 protein Tat is neurotoxic, and because cell survival is affected by the intracellular calcium concentration ([Ca2+]i), we determined mechanisms by which Tat increased [Ca2+]i and the involvement of these mechanisms in Tat-induced neurotoxicity. Tat increased [Ca2+]i dose-dependently in cultured human fetal neurons and astrocytes. In neurons, but not astrocytes, we observed biphasic increases of [Ca2+]i. Initial transient increases were larger in astrocytes than in neurons and in both cell types were significantly attenuated by antagonists of inositol 1,4,5-trisphosphate (IP3)-mediated intracellular calcium release [8-(diethylamino)octyl-3,4,5-trimethoxybenzoate HCI (TMB-8) and xestospongin], an inhibitor of receptor-Gi protein coupling (pertussis toxin), and a phospholipase C inhibitor (neomycin). Tat significantly increased levels of IP3 threefold. Secondary increases of neuronal [Ca2+]i in neurons were delayed and progressive as a result of excessive calcium influx and were inhibited by the glutamate receptor antagonists ketamine, MK-801, (+/-)-2-amino-5-phosphonopentanoic acid, and 6,7-dinitroquinoxaline-2,3-dione. Secondary increases of [Ca2+]i did not occur when initial increases of [Ca2+]i were prevented with TMB-8, xestospongin, pertussis toxin, or neomycin, and these inhibitors as well as thapsigargin inhibited Tat-induced neurotoxicity. These results suggest that Tat, via pertussis toxin-sensitive phospholipase C activity, induces calcium release from IP3-sensitive intracellular stores, which leads to glutamate receptor-mediated calcium influx, dysregulation of [Ca2+]i, and Tat-induced neurotoxicity.

2-Amino-5-phosphonovalerate↗
PubMed2001

Theoretical mechanistic basis of the toxic effects and efficacy of dideoxycytidine in HIV:AIDS.

Based on the structure of dideoxycytidine (ddc), the toxic effects of nitroso, areneimine, epoxide, hydroxyl free radical (*OH) and calcium chelating propensity respectively were evaluated using theoretical mechanistic biochemistry techniques. The 4-NH(2)group of the pyrimidine ddc structure was positive (+) for nitroso, (+) for areneimine, (+) for *OH; (+) for epoxide and negative (-) for calcium chelating propensity TMB toxic effects. The *OH was used to evaluate the TMB efficacy of ddc based on the structure of HIV. The *OH was found to be capable of damaging each of the following of the HIV structure: (1) the outer lipid membrane; (2) the glycoproteins of the envelope; (3) the viral RNA; (4) the p18 and p24 proteins in the core of the virus and (5) the reverse transcriptase replicating enzyme. The *OH is, therefore, exhibiting the characteristics of a 'bullet exterminator' for HIV:AIDS by attacking from the outwards inwards. Combination therapy of Artesunate (At) + AZT + ddc > At + AZT > AZT + ddc = At + ddc in the efficacy of HIV:AIDS was postulated.

Anti-HIV Agents↗
PubMed2005

Electronic structure of 1,3,5-triaminobenzene trication and related triradicals: doublet versus quartet ground state.

Quantum chemical calculations have been carried out to determine the electronic ground state of the parent 1,3,5-triaminobenzene trication triradical (TAB3+,C6H9N3 3+) containing a six-membered benzene ring coupled with three exocyclic amino NH(*+)2 groups, each containing an unpaired electron, as the simplest model for high-spin polyarylamine polycations. Related triradicals, including the 1,3,5-trimethylenebenzene (TMB, C9H9) and its nitrogen derivatives such as the monocation C8H9N+, the dication C7H9N2 2+, and the neutral C8H8N, C7H7N2, and C6H6N3 systems containing NH groups, have also been considered. Results obtained using the CASSCF [multiconfigurational complete active space (SCF--self-consistent field)] method, with active spaces ranging from (9e/9o) to (15e/12o), followed by second-order perturbation theory [CASPT2 and MS-CASPT2 (MS--multistate)] with polarized 6-311G(d,p) and natural orbital (ANO-L) basis sets reveal the following: (i) both TAB3+ and TMB (D3h) have a quartet 4A"1 ground state with doublet-quartet 2B1-4A"1 energy gaps of 8.0+/-2.0 and 12.4+/-2.0 kcal/mol, respectively; (ii) in the neutral N series, the quartet state remains the electronic ground state, irrespective of the number of N atoms, but each with slightly reduced gap, 11 kcal/mol for C8H8N (4A"), 10 kcal/mol for C7H7N2 (4A2), and 9 kcal/mol for C6H6N3 (4A2); and (iii) the ground state of monoamino cation and diamino dication is a low-spin doublet state (2B1 for C8H9N+ and 2A2 for C7H9N2 2+) and lying well below the corresponding quartet state by 10 and 12 kcal/mol, respectively. In the monocationic and dicationic amino systems, a slight preference is found for the low-spin state, apparently violating Hund's rule. This effect is due to the splitting of the orbital energies and the presence of the positive charge whose delocalization strongly modifies the electronic distribution and some structural features. In the latter cations, the positive charge basically pushes unpaired electrons onto the ring forming a kind of distonic radical cations and thus gives a preference for a low-spin state.

Journal Article↗
PubMed1996

Identification of an essential signaling cascade for mitogen-activated protein kinase activation by angiotensin II in cultured rat vascular smooth muscle cells. Possible requirement of Gq-mediated p21ras activation coupled to a Ca2+/calmodulin-sensitive tyrosine kinase.

In cultured rat vascular smooth muscle cells, angiotensin II (Ang II) induced a rapid increase in mitogen-activated protein kinase (MAPK) activity through the Ang II type 1 receptor, which was insensitive to pertussis toxin but was abolished by the phospholipase C inhibitor, U73122. The Ang II-induced MAPK activation was not affected by the protein kinase C inhibitor, GF109203X, and was only partially impaired by pretreatment with a phorbol ester, whereas both treatments completely prevented MAPK activation by the phorbol ester. Intracellular Ca2+ chelation by TMB-8, but not extracellular Ca2+ chelation or inhibition of Ca2+ influx, abolished Ang II-induced MAPK activation. The calmodulin inhibitor, calmidazolium, and the tyrosine kinase inhibitor, genistein, completely blocked MAPK activation by Ang II as well as by the Ca2+ ionophore A23187. Ang II caused a rapid increase in the binding of GTP to p21(ras), and this was inhibited by genistein, TMB-8, and calmidazolium but not by pertussis toxin or GF109203X. These data suggest that Ang II-induced MAPK activation through the Ang II type 1 receptor could be mediated by p21(ras)activation through a currently unidentified tyrosine kinase that lies downstream of Gq-coupled Ca2+/calmodulin signals.

Adenosine Triphosphate↗