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J D Glickson

Publications and source records attributed to J D Glickson.

At least 91 records · Page 5Linked to original sources
PubMed1983

Bleomycin interactions with DNA. Studies on the role of the C-terminal cationic group of bleomycin A2 in association with and degradation of DNA.

The role of the cationic dimethylsulfonium group of bleomycin A2 in the binding of the drug to poly(dA-dT) has been investigated by proton NMR studies on the S-demethylated derivative. In contrast to the parent drug, the demethyl congener shows no intercalation of the aromatic bithiazole group which is adjacent to the former cationic group. However, chemical studies show that the demethyl derivative retains the capability to degrade DNA in the presence of iron(II), albeit at a reduced rate and to a lesser extent than the intact bleomycin A2. Thus, the cationic group is necessary for the intercalation of the bithiazole portion of the drug molecule; however, intercalation is not essential for the degradation of DNA.

Animals↗
PubMed1983

Detection of antineoplastic agent induced cardiotoxicity by 31P NMR of perfused rat hearts.

Development of dose dependent chronic irreversible cardiotoxicity is a key problem encountered in chemotherapy with adriamycin. Here it has been demonstrated that infusion of this agent produced distinct and largely irreversible changes in levels of phosphate metabolites and substantial acidosis that are detected by 31P NMR of the Langendorf perfused heart. Administration of the antioxidant, butylated hydroxytoluene minimizes these spectral changes but does not substantially diminish the antineoplastic activity of adriamycin. Bisantrene (CL 216,942), a noncardiotoxic anthracene with antineoplastic activity, produces only minor perturbations of the 31P spectrum of the perfused rat heart. These studies demonstrate the potential utility of employing 31P NMR to monitor acute or chronic cardiotoxicity in the perfused rat heart and for developing noninvasive in vivo NMR techniques for monitoring cardiotoxicity in experimental animals and humans.

Animals↗
PubMed1983

In vivo 31P NMR study of the metabolism of murine mammary 16/C adenocarcinoma and its response to chemotherapy, x-radiation, and hyperthermia.

(31)P NMR spectroscopy with surface coils has been used to monitor, in vivo, the phosphate metabolism of subcutaneously implanted mammary 16/C adenocarcinoma in C3H/He mice. This model tumor was studied during untreated tumor growth and after treatment with adriamycin, hyperthermia, and x-radiation. The mammary 16/C tumor exhibited a Gompertzian growth pattern. Levels of high-energy phosphate metabolites-phosphocreatine and ATP-decreased with increases in tumor mass. There was a concomitant increase in the level of P(i) and a decrease in the apparent pH of the tumor. These spectral changes appear to reflect changes in tumor vascularization that accompany tumor growth, the tumor becoming progressively more hypoxic. Partial response of this tumor to chemotherapy with adriamycin was reflected in a small but measurable increase in the phosphocreatine resonance, a decrease in P(i), and a return of the intra-tumor pH to neutral. Hyperthermia resulted in progressive conversion of the (31)P NMR spectrum to that of a dead tumor (high levels of P(i), small levels of residual sugar phosphates and pyridine dinucleotides, and acidic pH). X-irradiation (14.0 Gy) led to disappearance of the phosphocreatine peak within 15 min of treatment. Subsequently, this resonance grew back beyond its pretreatment level. As the tumor receded, its spectrum reflected the characteristics of aerobically metabolizing tissue (high levels of phosphocreatine and ATP and low levels of P(i) and sugar phosphates).

Adenocarcinoma↗
PubMed1983

Studies on bleomycin-DNA and bleomycin-iron interactions.

The bleomycins, a group of antitumor antibiotics (Figure 1), cause the degradation of DNA by a process requiring iron(II) and dioxygen (1,2). DNA degradation appears to involve two steps: association of the drug with the nucleic acid and degradation of the DNA. As part of studies directed toward achieving an understanding of how the bleomycins degrade DNA, we have examined various properties of the drug using a variety of chemical and physico-chemical techniques, including NMR and Mössbauer spectroscopy. We have studied both the interaction of the antibiotic with its target (DNA) as well as its association with its metal ion cofactor. This work has been performed on the intact drug and its derivatives as well as on synthetic models of the parent drug. This paper reviews and updates the recent work from this laboratory on the bleomycins.

Binding Sites↗
PubMed1982

Models of bleomycin interactions with poly(deoxyadenylylthymidylic acid). Fluorescence and proton nuclear magnetic resonance studies of cationic thiazole amides related to bleomycin A2.

The interaction of eight 2-substituted thiazole-4-carboxamides, structurally related to cationic terminus of bleomycin A2, with poly(deoxyadenylylthymidylic acid) [poly(dA-dT)] has been studied by using proton nuclear magnetic resonance and fluorescence spectroscopy. These analogues have been used as probes of the complex formed between the parent drug molecule and poly(dA-dT). Aliphatic substituents on the 2' position of 2,4'-bithiazole derivatives restrict the ability of the aromatic ring system to intercalate in the double-helical form of the polynucleotide. Absence or partial removal of the 2' substituent enhances intercalation of the bithiazole system. The cationic side chain does not appear to be involved in the stabilization of any of these complexes, although it may be necessary for their formation. A 2,4':2',4"-terthiazole derivative shows a substantial degree of intercalation which is accompanied by extensive immobilization of the cationic side chain. This suggests that insertion of the aromatic system into the nucleic acid causes the cationic side chain to be pulled in also. Monothiazole analogues do not appear to bind, indicating that at least two thiazole rings are necessary for binding or that proper spacing between the two side chains on either side of the thiazole system is important for binding. The relation of the interactions of these analogues to the biochemical and biological properties of the parent bleomycins is discussed as is the possible use of these data in the design of synthetic bleomycin derivatives having varying affinities and specificities for DNA.

Bleomycin↗
PubMed1981

Synthesis and DNA binding of [3-[2'-(2-acetamidoethyl)-2,4'-bithiazole-4-carboxamido]propyl[dimethylsulfonium chloride, a fragment of bleomycin A2.

[3-[2'-(2-Acetamidoethyl)-2,4'-bithiazole-4-carboxamido]propyl]dimethylsulfonium chloride (1), the acetyl derivative of the cationic terminal dipeptide of bleomycin A2, has been synthesized and its binding to DNA and poly(dA-dT) has been studied by proton NMR and fluorescence spectroscopy. The spectral perturbations which occur upon binding of the compound to either nucleic acid indicate that that portion of bleomycin which binds to the nucleic acid can, for the most part, be mimicked by the fragment. The data are discussed in terms of the structure of the drug and the drug-nucleic acid complex.

Binding Sites↗
PubMed1981

Solution conformation of gramicidin S: An intramolecular nuclear Overhauser effect study.

The solution conformation of gramicidin S in deuterated dimethyl sulfoxide was investigated by using the intramolecular nuclear Overhauser effect experiment. Experimental Overhauser enhancements were compared with predicted values for each of the nine most-stable conformations (M1-M9) calculated by Dygert et al. on the basis of energy-minimization procedures [Dygert, M., Gō, N. & Scheraga, H. A. (1975) Macromolecules 8, 750-761]. By using statistical hypothesis testing, the three lowest-energy conformations (M1, M2, and M3) were shown to give the best fit with the experimental data. All other conformations (M4-M9) were found to be inconsistent with the experimental data.

Journal Article↗
PubMed1981

Proton NMR studies of the Zn(II)--bleomycin-A2--poly(dA-dT) ternary complex.

Proton NMR spectra demonstrate the formation of a ternary complex, Zn(II)--bleomycin-A2--poly(dA-dT), which serves as an analog of the putative active complex, Fe(II)--bleomycin-A2--DNA. Specific sites of metal--drug and drug--nucleic acid interaction have been delineated on the basis of chemical shift perturbations. On the basis of this criterion there appear to be three distinct regions of the drug: (i) the NH2 terminus up to and including the disaccharide and hydroxyhistidine residues, whose resonances are perturbed only by metal interactions; (ii) the COOH-terminal dipeptide, whose resonances are displaced only by nucleic acid interactions; and (iii) the methylvaleric acid-threonine dipeptide, which links these domains and whose resonances are sensitive to both types of interactions. The spectral perturbations in the first and second domains are very similar to changes observed in the corresponding binary complexes--i.e., Zn(II)--bleomycin-A2 and bleomycin-A2--poly(dA-dT), respectively.

Bleomycin↗
PubMed1981

H N.M.R. study of the conformation of [Glu4] oxytocin and its lanthanide complexes in aqueous solution.

At 400 MHz the 1H chemical shifts, peptide NH-C alpha H coupling constants (JN alpha) and peptide hydrogen exchange rates of [Glu4] oxytocin in aqueous solution closely resemble those previously reported for oxytocin under comparable conditions, indicating that both the parent hormone and its analogue have similar conformations in this solvent. The hydrogen exchange data suggest a dynamic equilibrium between conformation(s) in which the peptide NH's of Asn5 and Cys6 are internally hydrogen bonded and conformation(s) in which these hydrogens are bonded to the solvent. [Glu4] oxytocin forms 1:1 complexes with lanthanide metal ions. The diamagnetic La3+ complex exhibits values of JN alpha very similar to those of the metal free hormone analogue, suggesting that coordination of the metal is accompanied by minimal perturbation of the peptide backbone. Specific average proton-metal distances estimated from Gd3+ induced paramagnetic relaxation effects indicate that the metal is probably coordinated to the Glu4 carboxyl group and the sidechain carbonyl of Asn5. Limiting shifts induced by binding of paramagnetic Yb3+ are also reported.

Hydrogen Bonding↗
PubMed1980

Carbon-13 N.M.R. study of bleomycin-A2 protonation.

The acid-base titration of bleomycin-A2 in D2O solution at 35 +/- 5 degrees has been monitored by 13C n.m.r. spectroscopy at 67.89 MHz. The following pKDa values were obtained: 3.68 +/- 0.05 (secondary amine), 5.29 +/- 0.03 (imidazole), and 8.23 +/- 0.19 (primary amine), where KDa is the dissociation constant in D2O solution. The equilibrium isotope effects (pKDa--pKa in H2O) are: 0.70 +/- 0.06 (secondary amine), 0.28 +/- 0.04 (imidazole), and 0.85 +/- 0.19 (primary amine). Titration of the imidazole group of Bleo-A2 occurs at Npi, i.e. only Ntau is protonated in basic solution. Significant protonation shifts are almost completely limited to carbons of the N-terminal tetrapeptide, suggesting that the C-terminal tripeptide extends into the solvent and interacts to a minimal extent with the rest of the molecule. Long range protonation shifts associated with titration of the imidazole and secondary amine groups indicate that protonation of one or both of these sites is probably accompanied by significant conformational changes. The observed protonation shifts generally fail to correlate with Zn(II) complexation shifts reported by Dabrowiak et al. (1973, Biochemistry 17., 4090) indicating that ligation sites cannot unambiguously be determined from these complexation shifts. The complexation shifts previously attributed to coordination of the imidazole and carbamoyl groups probably result from conformational changes.

Amines↗
PubMed1979

Amide hydrogen exchange rates of peptides in H2O solution by 1H nuclear magnetic resonance transfer of solvent saturation method. Conformations of oxytocin and lysine vasopressin in aqueous solution.

The NH exchange rates in aqueous media of oxytocin and 8-lysine vasopressin (LVP) have been measured by using transfer of solvent saturation method. The data are consistent with a "highly motile" dynamic equilibrium between folded and highly solvated conformations. The highly-motility limit applies to the exchange of NH hydrogens of oxytocin and LVP. Folded structures are more prevalent in oxytocin than in LVP. Partial shielding is indicated for peptide hydrogens of Asn5 and perhaps also Cys6 of oxytocin and for Cys6 of LVP. It is tentatively proposed that the folded conformation of oxytocin in aqueous media may contain a parallel beta-structure in the tocinamide ring consisting of two hydrogen bonds: one between the Tyr2 C = O and Asn5 peptide NH as originally proposed for the preferred conformation of oxytocin in dimethyl sulfoxide (D. W. Urry and R. Walter), and the second between he Cys1 C = O and the Cys6 NH. In LVP the hydrogen bond between the Tyr2 C = O and Asn5 peptide NH appears to be absent. The acylic tripeptide sequences (-Pro-X-Gly-NH2) of both hormones appear to be predominantly solvated. The second-order rate constants for acid catalyzed exchange of the primary amide hydrogens of Gln4, Asn5, and Gly9 of oxytocin are consistently greater for the trans NH than for the corresponding cis NH. This observation can be rationalized in terms of mechanisms involving protonation of either the amide oxygen, or the amide nitrogen, but with limited rotation about the C - N bond.

Lypressin↗