The role of the gulose-mannose part of bleomycin in activation of iron-molecular oxygen complexes

A comparison of the complexing properties of metal ions and O2 activation by bleomycin-A2 (BLM-A2) and deglyco-BLM-A2 is presented. Deglyco-BLM-A2 is obtained from the parent derivative by HF cleavage of the sugar moiety followed by h.p.l.c. purification. Complexing of Cu(II) and Fe(III) is studied by using c.d. and e.s.r. spectroscopy. Spin-trapping experiments in the presence of phenyl N-t-butylnitrone indicated lower production of free radicals by deglyco-BLM-A2. Finally, a proposal is made to explain this discrepancy, focusing on the probable role of the gulose-mannose moiety acting as a protecting pocket, comparable with the pocket and picket-fence porphyrins described for haemoproteins.

DNA-binding and DNA-cleaving properties of a synthetic model AGAGLU related to the antitumour drugs AMSA and bleomycin

We have previously described two synthetic models gathering a simplified model of the complexing part of Bleomycin (Blm) and the intercalating moiety of m-AMSA. These molecules, namely AGGA and AGAMGA, do not seem able to cleave DNA as Blm does. The present work is devoted to the study of a new derivative, AGAGLU, which includes in its structure a judiciously chosen connector between the two parts of the molecule. This compound, the chelating and DNA-binding properties of which are described here, has been shown to induce single-strand breakage of duplex DNA in a high level.

Synthesis and conformation of the amino-terminal hexapeptide of histone H2B from gonads of the starfish Asterias rubens

This paper describes the synthesis and the physico-chemical characterization of N-(di-CH3)-L-Pro-L-Pro-L-Lys-L-Pro-L-Ser-Gly-OH by conventional methods of peptide chemistry. This peptide corresponds to the amino-terminal moiety of histone H2B from gonads of the starfish Asterias rubens.

Complexation of copper(II) by a peptide hybrid of bleomycin and amsacrine. Circular dichroism and electron spin resonance studies

A model incorporating the metal chelating moiety of bleomycin and an anilinoacridine ring able to intercalate in DNA has been synthesized. The copper(II) complex of that molecule has been studied using circular dichroism and electron spin resonance by comparison with bleomycin. The introduction of the anilinoacridine ring involves a modification in the geometry of the complex. A distortion of the square-pyramidal form (type II complex) gives rise to a type I complex in which the metallic atom is drawn out of the plane of the four square-planar ligands and displaced slightly towards the fifth ligand.

Grossularine-1 and grossularine-2, alpha carbolines from Dendrodoa grossularia, as possible intercalative agents

Dendrodoine A, grossularines-1 and -2, metabolites isolated from the tunicate Dendrodoa grossularia, have exhibited a cytotoxic activity on L1210 leukemia cells in culture. The inhibition of DNA synthesis induced by grossularines and the plane structure of the alpha-carboline common moiety were in favor of an intercalative process for their mechanism of action. In fact, the results of viscometry, fluorescence quenching and DNA melting experiments clearly indicated the intercalative properties of grossularine-2 explained by its quasi-planar structure and the non-intercalative DNA binding of grossularine-1 explained by the presence of a bulky indole chain at the 2-position of the alpha-carboline ring.

Chelating, DNA-binding and DNA-cleaving properties of a synthetic model for bleomycin

We have previously described a simplified model of the complexing part of bleomycin, namely methyl 2-(2-aminoethyl)-aminomethyl-pyridine-6-carboxyl-histidinate (AMPHIS), and disubstituted bithiazoles structurally related to the 'tripeptide S' moiety of bleomycin. The present work is devoted to the study of a new derivative, [3-[2-[2-(2-aminoethyl)-aminomethyl-pyridine-6-carboxyl-histidyl-3 -aminobutyryl-glycyl]-2',4-bithiazole-4-carboxamido]-propyl]- dimethylsulphonium iodide (AMBI-A2), which includes both AMPHIS and a judiciously chosen synthetic bithiazole. This compound, the synthesis of which is described here, has been shown to mimic the chelating and binding properties of the parent drug bleomycin A2, but to cleave DNA at higher concentration.

Design of two metal-chelating, DNA-binding models: molecular combinations of bleomycin and amsacrine anti-tumour drugs

In the course of studies on bleomycin, we recently showed that the bithiazole ring is a poor intercalator into DNA. Therefore we have designed new models, replacing this heterocyclic moiety by an anilinoacridine ring in order to increase the affinity for DNA. This work presents results obtained for two model compounds showing (i) that the anilinoacridine nucleus leads to a good stabilization of the DNA helix, and (ii) that the presence of a bulky group near the complexing part of bleomycin is essential to the activation of molecular oxygen.

A new bithiazole derivative with intercalative properties

In the course of studies related to new molecules with intercalative properties, we have been led to design and synthesize a bithiazole derivative, namely the 2-phenyl-6-[2'-(4'-(ethoxy-carbonyl)thiazolyl)]thiazolo[3,2- b][1,2,4]triazole (PETT). Its interaction with calf thymus DNA was studied using thermal denaturation and viscometry. Our results set in evidence that PETT acts as an intercalator, giving delta Tm, elongation and unwinding of DNA comparable to the values obtained for daunorubicin. The discrepancy between the data presented herein and those precedently obtained for bleomycin and bleomycin models provide evidence that these bithiazole derivatives interact differently with DNA.

Molecular interaction between bleomycin and amsacrine in the presence of cupric ions

The antineoplastic activity of m-AMSA [4'-(9-acridinylamino)-methanesulfon-m-anisidide] has been related to its ability to produce oxygenated free radical during its oxidation to a quinonimine form, in the presence of cupric ions. It has been demonstrated here that the rate of the oxidation is greatly increased by the addition of bleomycin (Blm), another antitumor agent, which is able to complex metallic ions. The catalytic role of Blm has been established on the basis of kinetics measurements and the occurrence of an intermediary ternary complex Blm-m-AMSA-Cu(II) has been demonstrated by circular dichroism and polarography experiments.

Is the bithiazole moiety of bleomycin a classical intercalator?

Bleomycin is a widespread anticancerous drug, the biological activity of which having been extensively studied. Its metal ion-chelating portion has been shown to cleave DNA whereas the role of the bithiazole moiety is still questionable. In order to elucidate this problem some 2', 4-disubstituted bithiazoles structurally related to the "tripeptide S" moiety of bleomycin were synthesized and their interaction with DNA was studied using delta Tm, fluorescence, EPR and viscometry techniques. The results of delta Tm and fluorescence quenching determinations were in favour of a binding of the bithiazole part by an intercalation process. Nevertheless, the use of the spin-label probes indicated only a partial intercalation of the ring between the base-pairs. Moreover, viscometry data which clearly exhibited a slight decrease of DNA length in the presence of bithiazole derivative led to the proposal of a binding model involving a partial insertion of a thiazole ring which wedges in between the bases at a bending point of DNA.

Design of a new DNA-polyintercalating drug, a bisacridinyl peptidic analogue of Triostin A

The synthesis of a new bifunctional compound in which two aminoacridine chromophores are linked by the bicyclic depsipeptidic backbone of des-N-tetramethylTriostin A is described. The molecule, bis-[(9-acridinyl)-D-seryl-L-alanyl-L-cysteinyl-L-valine] dilactone disulphide, structurally analogous to the antibiotic anti-tumour drug Triostin A, is shown to possess a high affinity to DNA and to act as a bis-intercalator on the basis of spectroscopic, viscosimetric and thermal-denaturation studies. This model constitutes the first attempt of a synergic association between a peptidic moiety that mimics a naturally occurring drug and aminoacridine, the two parts themselves each exhibiting a high affinity for the DNA target.

Conformation of physalaemin

The conformational and spatial configuration of the biologically active undecapeptide physalaemin was studied using 350-MHz1H NMR. The NMR analyses suggested the existence of a strong hydrogen bond between the amide proton of the Phe7 and a carbonyl group in the N-terminal moiety, most likely the Pro4 one. Other bondings were postulated, involving the side-chain amine of Lys6 and the side-chain amide of Asn5 and respectively the side-chain carboxyl of Asp3 and the terminal amide carbonyl of Met-NH2. Thus unlike its shorter peptidic fragments, physalaemin exhibited a stable molecular structure in solution, giving some insight into the conformation required for interaction at the biological receptor of tachykinins.

Synthesis and circular dichroism studies of two polypeptides H-[Gly-(Pro)3]n-OH and H-[Gly-(Pro)4]n-OH

Recently Gly-(Pro)3 a proline-rich protein (PRP) containing repetitive Gly-(Pro)3 or Gly-(Pro)4 sequences was isolated from human parotid saliva. The synthesis of two polypeptides containing these sequences is described. Their circular dichroism spectra have been recorded and are compared with the circular dichroism spectrum of the natural protein.