Specificity in DNA interactions: an nmr investigation of the interaction of propidium with oligodeoxyribonucleotides containing normal and G-T base pairs.
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Base Composition↗
Biomedical subjects
W D Wilson
Publications and source records attributed to W D Wilson.
The effect of intercalator structure on binding strength and base-pair specificity in DNA interactions.
The interaction of naphthothiophene, phenanthrene and anthracene ring systems, which have amide and ester side chains with cationic groups (synthesized from the aromatic acid chlorides and appropriate amines and alcohols), with calf thymus DNA has been investigated by using viscometric titrations, spectrophotometric binding experiments and 1H-, 31P- and 17O-NMR methods. The viscosity and NMR experiments suggest that all of these compounds bind to DNA by intercalation. These experiments and spectrophotometric binding studies, however, indicate that there is considerable variation in the interaction of these compounds with DNA. These variations can all be explained by the geometry of the ring systems, the position of protons adjacent to the side chains, and the relative sizes of the amide and ester side chains. With the naphthothiophene ester and amide, for example, the planar amide cannot rotate into the plane of the naphthothiophene ring whereas the smaller planar ester can. With this ring system the ester has a significantly higher binding constant than the amide derivative. Additional binding studies with poly[d(A-T)2] and poly[d(G-C)2] have shown that all of these compounds bind more strongly to the A-T- than the G-C-containing polymer. Since the ester compounds do not have hydrogen bond donating groups proximate to the aromatic ring, these results suggest a model for the A-T specificity of these compounds that involves a solvent-mediated hydrogen bond between the C-2 carbonyl of thymine and the carbonyl group of the intercalators.
Animals↗
Intercalators as probes of DNA conformation: propidium binding to alternating and non-alternating polymers containing guanine.
Propidium iodide is used as a structural probe for alternating and non-alternating DNA polymers containing guanine and the results are compared to experiments with poly[d(A-T)2], poly(dA . dT) and random DNA sequences. Viscometric titrations indicate that propidium binds to all polymers and to DNA by intercalation. The binding constant and binding site size are quite similar for all alternating polymers, non-alternating polymers containing guanine and natural DNA. Poly(dA . dT) is unusual with a lower binding constant and positive cooperativity in its propidium binding isotherms. Poly(dA . dT) and poly(dG . dC) have similar salt effects but quite different temperature effects in propidium binding equilibria. Polymers and natural DNA have similar rate constants in their SDS driven dissociation reactions. The association rate constants are similar for the alternating polymers and poly(dG . dC) but are significantly reduced for poly(dA . dT). These results suggest that natural DNA, the alternating polymers, and non-alternating polymers containing guanine convert to an intercalated conformation with bound propidium in a very similar manner.
Chemical Phenomena↗
Molecular basis for anticancer drug amplification: interaction of phleomycin amplifiers with DNA.
The interaction of two phleomycin amplifiers, N,N-dimethyl-2-[[4'-(thien-2''-yl)pyrimidin-2'-yl]thio]ethylamine (1S, high activity) and N-[2''-(dimethylamino)ethyl]-4-(thien-2'-yl)pyrimidin-2-amine (1N, low activity) with DNA has been evaluated. The visible absorption bands of both compounds shift to longer wavelengths, and both exhibit hypochromicity on titration with DNA. The effects for 1S at low concentration are significantly greater than for 1N. 1S increases the DNA Tm by 2.5 degrees C while 1N causes only a 1.0 degree C increase under the same conditions. Spectrophotometric binding analysis of the interaction of 1S and 1N with calf thymus DNA indicates that 1S binds over 4 times more strongly to this DNA than 1N. Both compounds increase DNA viscosity, cause downfield shifts in DNA 31P NMR spectra, and shift the DNA imino base pair protons upfield, conclusively demonstrating that they bind to DNA by intercalation. Signals for the aromatic protons of 1S and 1N are shifted upfield on addition of DNA as expected for intercalation. The shifts for all aromatic protons are similar on 1S and on 1N, indicating that both the pyrimidine and thiophene are inserted between the DNA base pairs in the complex. NOE experiments demonstrate that the compounds are in the s-cis conformation both free in solution and in the DNA intercalation complex. Semiempirical INDO/S calculations indicate greater polarization of the pi-electron system of 1S than 1N. This greater polarization may account for the stronger interaction of 1S with DNA base pairs than 1N. The interaction of these compounds with DNA is strongly correlated with their biological amplification activity.
Bleomycin↗
Clinicopathologic study of horses surviving pyrrolizidine alkaloid (Senecio vulgaris) toxicosis.
Twenty horses of various ages had inadvertently ingested alfalfa hay contaminated with Senecio vulgaris. Among them, 4 died of liver disease. Blood was collected from affected horses at monthly intervals for 7 months and at the 9th and 14th months. The following serum enzymes and chemical items were assayed: aspartate aminotransferase, lactate dehydrogenase, alkaline phosphatase, gamma-glutamyl transferase, sorbitol dehydrogenase, total bilirubin, BUN, glucose, cholesterol, inorganic phosphate, calcium, total protein, and albumin. Amino acid profiles, conjugated bile acids, sulfobromophthalein clearance times, and liver histopathologic changes via serial biopsies were also monitored. Liver histopathologic changes revealed lesions progressively increasing in severity. Aspartate aminotransferase and plasma amino acid ratios indicated chronic liver degeneration (0.05 level of significance). gamma-Glutamyl transferase and lactate dehydrogenase as well as BUN values fluctuated, but returned to within reference values. Horses appeared clinically normal 14 months after intoxication, but were unable to tolerate stress of exercise.
Amino Acids↗
Pharmacokinetics and endometrial tissue concentrations of ticarcillin given to the horse by intravenous and intrauterine routes.
Plasma and endometrial tissue concentrations of ticarcillin were measured in healthy mares. In the first of the 3 separate phases comprising the study, ticarcillin disodium (30 mg/kg) was administered IV. The mean peak concentration in endometrial tissue, 12.9 micrograms/g, was attained at 30 minutes. The plasma half-life of the drug in the 6 mares was 0.83 +/- 0.22 hour. Six grams of the drug was diluted in 250 ml of sodium chloride injection USP (2nd phase) and in 60 ml of sodium chloride injection USP (3rd phase). These dilutions were administered by intrauterine infusion. In phase 2, the mean peak concentrations of the drug in plasma and endometrium were 2.76 micrograms/ml and greater than 150 micrograms/g, respectively, at 60 minutes after it was administered. Endometrial concentrations greater than 150 micrograms of ticarcillin/g persisted through 2 hours after the drug was administered. Mean peak plasma and endometrial concentrations of the drug in phase 3 were 2.78 micrograms/ml and greater than 150 micrograms/g at 45 and 30 minutes after administration was done, respectively. At 1 hour after the drug was administered, endometrial concentrations of ticarcillin were significantly higher (P less than 0.01) after the drug was infused intrauterinely in the 250-ml volume than those after the 60-ml volume was infused. It was concluded that the volume of fluid in which the drug was infused into the uterus markedly influenced the duration of concentrations greater than 20 micrograms/g in endometrial tissue.
Animals↗
Proton NMR investigation of the nucleosome core particle: evidence for regions of altered hydrogen bonding.
Novel 1H nuclear magnetic resonance (NMR) resonances, arising from exchangeable protons and centered at approximately 11.2 and 10.1 parts per million (ppm), have been observed in the low-field spectrum (10-15 ppm) of the chicken erythrocyte core particle [145 +/- 2 base pairs (bp)]. These peaks are located upfield from the normal adenine-thymine (A-T) and guanine-cytosine (G-C) imino peaks characteristic of B-form deoxyribonucleic acid (DNA) and are not observed in free DNA under identical conditions. The appearance of the new peaks is ionic strength dependent and temperature-reversible below 75 degrees C. At 25 degrees C, the upfield peak area represents 5% of the DNA base pairs (7 bp), while between 45 and 55 degrees C, the area increases to 18%, affecting approximately 25 bp. Area increases in the upfield resonances result in a complementary decrease in the A-T and G-C imino peaks found between 12 and 14 ppm. We believe these novel proton signals represent a histone-induced DNA conformational change which involves localized alteration of base pairing in the core particle.
Animals↗
Poly(dA).poly(dT) exists in an unusual conformation under physiological conditions: propidium binding to poly(dA).poly(dT) and poly[d(A-T)].poly[d(A-T)].
The binding of propidium to poly(dA).poly(dT) [poly(dA.dT)] and to poly[d(A-T)].poly[d(A-T)] [poly[d(A-T)2]] has been compared under a variety of solution conditions by viscometric titrations, binding studies, and kinetic experiments. The binding of propidium to poly[d(A-T)2] is quite similar to its binding to calf thymus deoxyribonucleic acid (DNA). The interaction with poly(dA.dT), however, is quite unusual. The viscosity of a poly(dA.dT) solution first decreases and then increases in a titration with propidium at 18 degrees C. The viscosity of poly[d(A-T)2] shows no decrease in a similar titration. Scatchard plots for the interaction of propidium with poly(dA.dT) show the classical upward curvature for positive cooperativity. The curvature decreases as the temperature is increased in binding experiments. A van't Hoff plot of the observed binding constants yields an apparent positive enthalpy of approximately +6 kcal/mol for the propidium-poly(dA.dT) interaction. Propidium binding to poly[d(A-T)2] shows no evidence for positive cooperativity, and the enthalpy change for the reaction is approximately -9 kcal/mol. Both the magnitude of the dissociation constants and the effects of ionic strength are quite similar for the dissociation of propidium from poly(dA-T)2] and from poly[d(A-T)2], suggesting that the intercalated states are similar for the two complexes. The observed association reactions, under pseudo-first-order conditions, are quite different. Plots of the observed pseudo-first-order association rate constant vs. polymer concentration have much larger slopes for propidium binding to poly[d(A-T)2] than to poly(dA.dT).(ABSTRACT TRUNCATED AT 250 WORDS)
Kinetics↗
Characteristics of the binding of the anticancer agents mitoxantrone and ametantrone and related structures to deoxyribonucleic acids.
The binding constants for interaction of the anticancer agents mitoxantrone and ametantrone and several congeners with calf thymus DNA and the effects of ionic strength changes have been determined spectrophotometrically. The agents show a preference for certain sequences, particularly those with GC base pairs, and the magnitude of the specificity depends on the specific substituents on the anthraquinone ring system. The binding constant for mitoxantrone with calf thymus DNA in 0.1 M Na+, pH 7, is approximately 6 X 10(6) M-1, and the rate constant for the sodium dodecyl sulfate driven dissociation of mitoxantrone from its calf thymus DNA complex under the same solution conditions and 20 degrees C was determined to be 1.3 s-1. The unwinding angle of mitoxantrone determined independently by viscosity measurements and by a novel assay employing calf thymus topoisomerase shows excellent agreement for a value of 17.5 degrees. The viscosity increase of sonicated calf thymus DNA varies considerably with the substituent on the anthraquinone ring system. Binding studies employing T4 and phi w-14 DNAs in which the major groove is occluded and the reverse experiment with anthramycin-treated calf thymus DNA indicate at least part of the mitoxantrone molecule may lie in the minor groove.
Animals↗
Occipitoatlantoaxial malformation in two non-Arabian horses.
Occipitoatlantoaxial malformation was diagnosed in a 19-month-old mare of Appaloosa breeding and in a 3-year-old Quarter Horse gelding. Both horses had abnormal head and neck carriage since birth, but neurologic deficits did not become evident clinically until the horses reached 2 and 3 years of age, respectively. Palpation and manipulation of the base of the skull and cervical area proved to be useful diagnostically. Movement could not be elicited at the atlantooccipital joint but, in comparison with clinically normal horses, the range of dorsoventral motion at the atlantoaxial joint was increased. Alternate subluxation and relocation of this joint generated audible clicking sounds. Radiography revealed symmetric atlantooccipital fusion, with modification of the atlas, atlantoaxial joint, and axis. These findings were confirmed at necropsy.
Abnormalities, Multiple↗
Rubella: immunity and vaccination in schoolgirls.
Of 191 schoolgirls, 128 volunteered to take part in a feasibility study of serotesting before and after rubella vaccination, and all responded to RA 27/3 vaccine. Had the serum samples been taken by a fingerprick method the number of volunteers would probably have increased considerably. A change in policy for rubella vaccination to testing both before and after vaccination would cost no more than the existing policy, would ensure primary response, and would differentiate those women who were protected by the vaccine from those with antibody to wild virus.
Adolescent↗
Mechanism of intercalation: ion effects on the equilibrium and kinetic constants for the interaction of propidium and ethidium with DNA.
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Chemical Phenomena↗
Imino 1H- and 31P-NMR analysis of the interaction of propidium and ethidium with DNA.
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Chemical Phenomena↗
The intercalation of 6-chloro-substituted-9-[[3-(dimethylamino)propyl]amino]acridines with DNA.
A series of 6-chloro-2-substituted-9-[[3-(dimethylamino)propyl]amino]acridines has been prepared. The binding affinities and the unwinding angles for the acridine derivatives, relative to ethidium, were determined from viscometric titrations with ccs-DNA. The binding affinities were the same, within experimental error, ca. 2.0 X 10(-5). Similarly, with the exception of 11, the unwinding angles were close to 17 degrees. For 11 the unwinding angle (12 degrees) was smaller than the other derivatives. The general insensitivity of the apparent binding constants to substituent effects is attributable to a masking effect of the formal charge on the ring. The smaller unwinding angle for 11 is believed to arise from its relative dissymmetry, resulting in a "wedge" effect upon intercalation.
Aminoacridines↗
Cefadroxil in the horse: pharmacokinetics and in vitro antibacterial activity.
Sodium cefadroxil was administered as a single intravenous dose (25 mg/kg) to six healthy adult mares. Plasma samples were collected over a 24-h period and cefadroxil concentrations were measured by microbiological assay. The pharmacokinetic behavior of the drug was appropriately described in terms of a one-compartment open model. Values for the major pharmacokinetic terms were: extrapolated initial plasma concentration = 59.2 +/- 15.0 micrograms/ml; half-life = 46 +/- 20 min; apparent volume of distribution = 462 +/- 191 ml/kg; and body clearance = 7.0 +/- 0.6 ml/min.kg. In a subsequent study, a suspension of cefadroxil monohydrate was administered intragastrically (25 mg/kg) to the same six horses. Plasma concentrations of the drug peaked at 1-2 h but, in general, absorption was both poor and inconsistent. The data were unsuitable for determination of cefadroxil bioavailability from this oral dosage form. Ninety-nine isolates of eleven bacterial species obtained from clinically ill horses were tested for susceptibility to cefadroxil. All strains of Streptococcus equi, Streptococcus zooepidemicus, coagulase-positive staphylococci, Corynebacterium pseudotuberculosis and five out of six strains of Actinobacillus suis were highly susceptible to the drug (MIC less than 4 micrograms/ml). Escherichia coli, Klebsiella pneumoniae and Salmonella sp. showed intermediate susceptibility (MIC 4-16 micrograms/ml), while all isolates of Corynebacterium (Rhodococcus) equi, Enterobacter cloacae and Pseudomonas aeruginosa proved to be highly resistant to cefadroxil (MIC greater than 128 micrograms/ml).
Animals↗
Susceptibility of equine bacterial isolates to antimicrobial agents.
In vitro antimicrobic susceptibility patterns of commonly isolated aerobic gram-positive and gram-negative bacterial pathogens of equine origin were determined, using the agar-plate dilution method. All organisms were recent clinical isolates and included Corynebacterium (Rhodococcus) equi, Corynebacterium pseudotuberculosis, (coagulase positive) Staphylococcus sp, Streptococcus equi, Streptococcus zooepidemicus, Actinobacillus sp, Enterobacter cloacae, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Salmonella. In vitro susceptibility levels were outlined for 14 antimicrobics as follows: amikacin less than or equal to 4.0 micrograms/ml, ampicillin less than or equal to 1.0 microgram/ml, amoxicillin less than or equal to 1.0 microgram/ml, cefadroxil less than or equal to 8.0 micrograms/ml, chloramphenicol less than or equal to 8.0 micrograms/ml, erythromycin less than or equal to 1.0 microgram/ml, gentamicin less than or equal to 2.0 micrograms/ml, kanamycin less than or equal to 4.0 micrograms/ml, penicillin less than or equal to 1.0 microgram/ml, tetracycline less than or equal to 1.0 microgram/ml, sulfadimethoxine less than or equal to 10.0 micrograms/ml, ormetoprim/sulfadimethoxine less than or equal to 0.5/9.5 micrograms/ml, sulfadiazine less than or equal to 10.0 micrograms/ml, and trimethoprim/sulfadiazine less than or equal to 0.5/9.5 micrograms/ml.
Aerobiosis↗
Antibiotic treatment of Moraxella bovis infection in cattle.
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Animals↗
Evidence for similar structural changes on binding of platinum anti-tumor agents to DNA and nucleosomes.
The influence of Pt(II) compounds on the 31P NMR spectra of natural DNA, synthetic polynucleotides, and nucleosomes was investigated. With Pt complexes which are anti-tumor agents, a new peak or shoulder centered at approximately 1.2 ppm downfield from the untreated DNA signal was observed. When Pt compounds known not to be anti-tumor agents were studied, no such new signal was observed. The most reasonable explanation for the downfield resonance is that it is a consequence of a structural change induced in the DNA by the anti-tumor agent. Since the effect of the Pt compounds on nucleosomes was similar, the same structural change is probably occurring in DNA in solution and in nucleosomes. A nonalternating dG . dC polymer, but not alternating G . C or any A . T polymers, exhibited a similar spectral change and this finding suggests that the structural change in the DNA arises primarily from reaction of Pt anti-tumor agents with adjacent G residues.
Animals↗