Application of circular dichroism to the study of interactions between small molecular compounds and DNA / 药学学报

Circular dichroism (CD) is an useful technique for monitoring DNA conformation changes resulting from changes in environmental conditions, such as temperature, ionic strength, and pH, and also for the study of the interaction between DNA and ligands (including small molecules and proteins). CD spectroscopy of DNA arises from the asymmetric backbone sugars and by the helical structures often adopted by nucleic acids. By the interpretation of induced circular dichroism (ICD) of ligand signals resulting from the coupling of electric transition moments of the ligand, DNA bases within the asymmetric DNA environment, ligand-DNA interactions, as well as the DNA-binding mode can be assessed. A number of important conclusions have been reported that related to the observed ICD signals resulting from the interactions between intercalators and groove binders with DNA. If short oligonucleotide sequences are used in the study, sequences-specific of binding also can be deduced. CD determination requires smaller amounts of sample, and not limited by the molecular weight or size and can be performed rapidly; though CD is of low resolution, but it's a complement to NMR and X-ray diffraction methods. This review will introduce the characters of the CD spectra of DNA, and its application to the studies of DNA with small molecules; some progress of the studies in our laboratory will also be discussed. CD is expected to be used as a screening method in seeking more DNA-targeted drugs, such as, antineoplastic, antimicrobial and antiviral drugs.

Biological properties of 8-methoxypyrimido[4(1),5(1):4,5]thieno(2,3-b)quinoline-4(3H)-one, a new class of DNA intercalating drugs.

BACKGROUND & OBJECTIVES: The compounds containing novel tetracyclic condensed quinoline ring system is of interest because of its close relationship with anticancer drug ellipticine. 8-Methoxypyrimido[4(1),5(1):4,5]thieno(2,3-b)quinoline-4(3H)-one (MPTQ) was investigated to study its effect on in vitro growth inhibition and clonogenic cell survival assay on three tumour cell lines, human promyelocytic leukemia HL-60, melanoma B16F10 and neuro 2a. A systematic study was carried out to evaluate its antitumour efficacy against B16 murine melanoma. Antiinflammatory and analgesic activities of MPTQ were also studied. METHODS: The cytotoxicity of MPTQ on HL-60, B16F10 and neuro 2a cells was estimated by trypan blue exclusion test. The antitumour activity was evaluated using single dose, multiple/daily injections (days 3-6) or intermittent treatments over two weeks against s.c. implanted B16melanoma, both in terms of increased life span and tumour growth inhibition. Antiinflammatory activity was seen on carrageenan induced hind paw oedema. Counting the number of abdominal constrictions after the injection of acetic acid assessed the analgesic response. RESULTS: MPTQ is cytotoxic to all the cell lines tested and ID50 being in the range of 0.08-1.0 microM. MPTQ was studied for anticancer activity in the clonogenic assay. Drug was applied over a wide dose range by 24 h exposure, yielding clear dose-response effects. In vivo antitumour efficacy against B16 melanoma showed evidence of major antitumour activity for MPTQ. Single and multiple i.p. doses of drug proved high level activity against the s.c. grafted B16melanoma, significantly increasing survival (P<0.001) and inhibiting tumour growth (T/C of 3.0%). A reduction (76.48%) in paw volume was noted in 40 mg/kg dose of which was comparable to antiinflammatory activity of 150 mg/kg i.p. of phenylbutazone. Analgesic activity was found to be of peripheral type as there was reduction of 74 per cent in writhing response by MPTQ in dose of 40 mg/kg in mice. INTERPRETATION & CONCLUSION: The results suggested that the compounds containing pyrimidothienoquinoline system particularly 8-methoxy derivative might be potentially useful antitumour agent. We conclude that the correlation of physicochemical properties of the new series of pyrimidothienoquinolines with their pharmacological properties, might help in trying to understand the mechanism of pyrimidothienoquinolines series.

Molecular aspects on the interaction of sanguinarine with B-form, Z-form and HL-form DNA structures.

The interaction of sanguinarine with right-handed (B-form), left-handed (Z-form) and left-handed (HL-form) structures of poly(dG-dC).poly(dG-dC) has been investigated by measuring the circular dichroism (CD) and UV-absorption spectral analysis. Sanguinarine binds strongly to the B-form DNA and does not bind to Z-form or HL-form, but it converts the Z-form and the HL-form back to the bound right handed form as evidenced from CD spectroscopy. Sanguinarine inhibits the rate of B to Z transition under ionic conditions that otherwise favour the left-handed conformation of the polynucleotides. UV absorption kinetic studies show that the Z-form reverses back to B-form to B-form on binding to sanguinarine. Binding isotherms obtained from spectrophotometric data show that sanguinarine binds strongly to the B-form polymer in a non-cooperative manner, in sharp contrast to the highly cooperative interaction under Z-form and HL-form polynucleotides. These studies reveal that the alternating GC sequence undergoes defined conformational changes and interacts with sanguinarine which may be an important aspect in understanding its extensive biological activities.

Intercalation compounds involving inorganic

Two-dimensional inorganic networks can shown intracrystalline reactivity, i.e., simple ions, large species as Keggin ions, organic species, coordination compounds or organometallics can be incorporated in the interlayer region. The host-guest interaction usually causes changes in their chemical, catalytic, electronic and optical properties. The isolation of materials with interesting properties and making use of soft chemistry routes have given rise the possibility of industrial and technological applications of these compounds. We have been using several synthetic approaches to intercalate porphyrins and phthalocyanines into inorganic materials: smectite clays, layered double hydroxides and layered niobates. The isolated materials have been characterized by elemental and thermal analysis, X-ray diffraction, surface area measurements, scanning electronic microscopy, electronic and resonance Raman spectroscopies and EPR. The degree of layer stacking and the charge density of the matrices as well their acid-base nature were considered in our studies on the interaction between the macrocycles and inorganic hosts.

Interaction of the antitumour alkaloid coralyne with duplex deoxyribonucleic acid structures: spectroscopic and viscometric studies.

The interaction of coralyne, an antitumour alkaloid with natural and synthetic duplex DNAs was investigated under conditions where the drug existed fully as a true monomer for the first time using spectrophotometric, spectrofluorimetric, circular dichroic and viscometric techniques. The absorption spectrum of coralyne monomer showed hypochromic and bathochromic effects on binding to duplex DNAs. This effect was used to determine the binding parameters of coralyne. The binding constants for four natural DNAs and four synthetic polynucleotides obtained from spectrophotometric titration, according to an excluded site model, using McGhee-von Hippel analysis, were all in the range of (0.38-9.8) x 10(5) M-1, and showed a relatively high specificity for the GC rich ML DNA and the alternating GC polynucleotide. The binding of coralyne decreased with increasing ionic strength, indicating that the binding affinity has a strong electrostatic component. Coralyne stabilized all the DNAs against thermal strand separation. The intense steady state fluorescence of coralyne was effectively quenched on binding to DNAs and the quantitative data on the Stern-Volmer quenching constant obtained was sequence dependent, being maximum with the GC rich DNA and alternating GC polymer. Circular dichriosm studies further evidenced for a strong perturbation of the B-conformation of DNAs consequent to coralyne binding with the concomitant development of extrinsic circular dichroic bands for the bound drug molecules suggesting their strong intercalated geometry in duplex DNAs. Further tests of intercalation using viscosity measurements on linear and covalently closed plasmid DNA conclusively proved the strong intercalation of coralyne in duplex DNA. Binding of the closely related natural alkaloid, berberine under these conditions showed considerably lower affinity to duplex DNAs in all experiments. Taken together, these results suggest that coralyne binds strongly to duplex DNAs by a mechanism of intercalation with specificity towards alternating GC duplex structure.

1H NMR investigation of the interaction of berberine and sanguinarine with DNA.

Interaction of the alkaloids, berberine and sanguinarine with calf thymus DNA has been studied by 1H NMR. All proton resonances of the two compounds have been assigned using 2D-COSY, NOESY and ROESY spectra. Berberine has been found to partially intercalate into DNA, while sanguinarine shows normal intercalation and also binds more firmly to DNA. The NMR experiments indicate that sanguinarine is more potent than berberine in its activity.

Epidemic dropsy in Trans Yamuma areas of Delhi and U.P.

Thirty patients of epidemic dropsy from seven families scattered in different areas of East Delhi and UP were studied. The age group of the affected individuals varied from 2 years to 55 years. Argemone oil contamination was found in mustard oil used for cooking. Sanguinarine was detected in all suspected oil samples. Pitting edema of legs was the most consistent feature present in all cases. Other prominent features like local erythema and tenderness were present in 80% and 70% cases, respectively. In contrast to earlier epidemics, two striking features were presence of persistent tachycardia without any pyrexia in all the cases and absence of any ocular problems. There was one death due to congestive heart failure and partial recovery in all others in a 2 months follow up.

Mode of action of intercalators: a theoretical study.

Mode of action of some intercalators has been theoretically investigated on the basis of quantum mechanical perturbation method. Energies of H-bond interaction between drug chromophore and base pairs have been calculated in all possible orientations. The stacking energy has also been calculated with the base pairs. The effect of these interactions on specific recognition has also been discussed. On the basis of these studies, a model for the interaction of these drugs has been proposed. This explains the relative activities of acridine intercalators and satisfies the experimental observations.

Further simplification of the general analysis of the intercalative drug-DNA interaction.

The application of McGhee and von Hippel's general equation [J. Mol. Biol., 86 (1974), 469-489, Eq. (15)] to the analysis of the interaction of intercalative drugs with DNA has been further simplified. The value of n can now be determined mathematically, using a simple function, and without any approximation. It is also established that the summation of squared deviation of (( (nu/c), nu)) points would be minimum for and only for the true set of (K,n,omega) of the interaction system. The method incorporating the simplification has been applied to determine the binding parameters of adriamycin-DNA interaction according to the above general equation.

Ametantrone acetate: anthracenedione diacetate, NSC-287513

El acetato de ametantrona es el compuesto padre de una serie de antracenodionas actualmente sometidois a pruebas clínicas en los Estados Unidos. Se sintetizaron estos compuestos en un intento de eliminar la toxicidad cardíaca asociada con antibióticos antraciclínicos sin sacrificar la actividad clínica. El acetato dea meyantrona parece funcionar como un agente intercalador. En sistemas de tumores murinos, la droga produce curas en leucemias P388 y L1210, melanoma B16 y carcinoma de colon 26. En perros, los objetivos principales de la toxicidad fueron la médula ósea, el tejido linfoide, la vía gastrointestinal y los testículos. La droga no es activa por vía orla. El acetato de ametantrona muestra una curva dósis/repuesta de inclinación relativamente alta. La administración intravenosa rápida en ratones produce convulsiones instantáneas y muerte. Aunque menos frecuente y menos severa que la toxicidad producida por antraciclinas, pudo demostrarse toxicidad cardíaca en ratones, ratas, conejos y perros. El acetato de ametantrona es un compuesto de un azul intenso que imparte color azul a la orina, la materia fecal, la piel y a los órganos internos. El período de vida media plasmático de la droga es aproximadamente dos horas. Se han comenzado tres estudios clínicos Fase 1: dos utilizan un régimen de una sola dósis y uno un régimen de 5 días. Hasta la fecha se han notado muy pocas respuestas. La toxicidades más importantes han sido leucopenia, decoloración azul de la piel, alopecia e hipotensión ortostática. La dósis inicial recomendada para estudios fase 2 de una sola dósis en pacientes de alto riesgo es 140 mg/m2