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B Bodo

Publications and source records attributed to B Bodo.

At least 37 records · Page 2Linked to original sources
PubMed1999

Redox regulation of tumor cell toxicity by flavones from Lethedon tannaensis.

The purpose of the present work has been to seek a correlation of potential predictive value, demonstrating redox control of cytotoxicity toward human nasopharynx carcinoma (KB) cells by seven 5-hydroxy-7-methoxyflavones, together with two glycoside derivatives, all extracted from Lethedon tannaensis. In this approach, redox control is characterized by a physicochemical parameter expressing quantitatively the relative electron-donating power of the flavones, this parameter being the second order rate constant, kdelta, for quenching of singlet oxygen O2 (1deltag). This rate constant kdelta is usually related to the ability of a given molecule D to donate an electron and, thus, with the reduction potential E of the couple (D*+/D). Our results show that the flavone toxicity is linearly correlated with ease of oxidation: the higher the rate constant of reaction with singlet oxygen, the easier the oxidation, the less positive or more negative the reduction potential ((D*+/D), the higher the cytotoxicity. The results suggest new screening strategies to identify and improve potential antitumor drugs.

Antineoplastic Agents, Phytogenic↗
PubMed1999

Five new flavone 5-O-glycosides from Lethedon tannaensis: lethedosides and lethediosides.

Five new 7-methoxy-flavone 5-O-glycosides were isolated from a cytotoxic MeOH extract of Lethedon tannaensis, and the structures were elucidated by 2D NMR spectral analysis and by chemical methods. Lethedosides A (1), B (2), and C (3) were 5-O-glucosides of 7,3', 4'-tri-O-methylluteolin, 7,3',4',5'-tetra-O-methyltricetin, and 7,3', 4'-tri-O-methytricetin, respectively; lethediosides A (4) and B (5) and a known compound 6 were 5-O-xylosylglucosides of 7,3', 4'-tri-O-methylluteolin, 7,3',4',5'-tetra-O-methyltricetin, and 7, 4'-di-O-methylapigenin, respectively. These flavonoids were either inactive or weakly active against KB tumor cells, in contrast to previously isolated flavones from the same plant.

Antineoplastic Agents, Phytogenic↗
PubMed1998

Ionophoric activity of the antibiotic peptaibol trichorzin PA VI: a 23Na- and 35Cl-NMR study.

Trichorzin PA VI (Ac Aib1 Ser Ala Aib Iva Gln Aib Val Aib Gly10 Leu Aib Pro Leu Aib Aib Gln Pheol18) is one of the seven main peptaibols forming the natural antibiotic 18-residue peptide mixture biosynthesised by a Trichoderma harzianum strain. Trichorzins exhibit antimycoplasmic activity resulting from membrane permeability perturbations. The membrane permeabilisation process by trichorzin PA VI has been examined in egg yolk phosphatidylcholine large unilamellar vesicles (LUV) and under conditions of ionic equilibrium by 23Na- and 35Cl-NMR experiments conducted in the presence of a chemical shift reagent and a relaxation agent, respectively. In such conditions, trichorzin PA VI exchanges both cations and anions across the vesicle bilayers, indicating the absence of ion- and charge-selectivity, in contrast to antibiotic ionophores, such as monensin or nigericin; the Na+ exchange is not influenced by the ionic strength. The kinetics of the Na+ exchange have been found to be third to fourth order with respect to the peptide concentration. The permeabilisation process of liposomes has been shown to be due to the formation of aggregates of three to four helical peptide monomers arranged into a supramolecular complex including presumably lipid molecules and forming a badly-defined pore in the bilayer. The major mechanism by which ions may exchange through the bilayer involves a long-lasting opening of the pores allowing complete exchange of the internal and external media in an 'all or nothing mode'.

Amino Acid Sequence↗
PubMed1998

Membrane permeabilisation and antimycoplasmic activity of the 18-residue peptaibols, trichorzins PA.

The membrane permeabilisation properties of six linear natural 18-residue peptaibols, termed trichorzins PA, have been assessed on liposomes and on mollicutes (trivial name, mycoplasmas), a class of parasitic bacteria characterized by a small genome, the lack of a cell wall, a minute cell size, and the incorporation in their plasma membrane of exogenously supplied cholesterol. The trichorzins PA used in this study (PA II, PA IV-VI, PA VIII, and PA IX) differ between them by amino acid or amino alcohol substitutions at positions 4, 7, and 18, and form slightly amphipathic alpha-helices. They proved bactericidal for mollicutes belonging to the genera Acholeplasma, Mycoplasma, and Spiroplasma, with minimal inhibitory concentrations (3.12</=MICs</=50 microM) generally 2 to 4 fold higher than those of alamethicin F50, a related 20-residue peptide (1.56</=MICs</=12.5 microM). Spiroplasma cells were apparently not protected by the presence of spiralin on their surface. The activities of the six trichorzins PA were not influenced by their sequence variations and no synergistic effect was observed. Consistent with the marginal effect of cholesterol on the incorporation of the trichorzins PA into liposome bilayers, the antibiotic activity was independent of the amount of cholesterol in the membranes of the different mollicutes. The trichorzins PA and alamethicin inhibited the motility of Spiroplasma melliferum, the helical cells being deformed and split into coccoid forms. Membrane potential measurements in Acholeplasma laidlawii and S. melliferum showed that trichorzin PA V and alamethicin F50 very efficiently depolarized the plasma membrane of mollicutes. This was consistent with fluorescence and 23Na NMR measurements on liposomes that revealed the permeabilisation of the lipid bilayer and the nonselective ionophoric activity of the trichorzins PA. These data suggest that the bactericidal activity exhibited by the trichorzins PA on mollicutes is due to the permeabilisation of the plasma membrane.

Alamethicin↗
PubMed1998

Conrauinones A and B, Two New Isoflavones from Stem Bark of Millettia conraui1

Two new isoflavones, named conrauinones A (1) and B (2), have been isolated from the stem bark of Millettia conraui, in addition to known 5-methoxydurmillone. The structures of the new compounds were determined by spectroscopic analysis including 2D NMR techniques as 5,6,2'-trimethoxy-4',5'-(methylenedioxy)-2",2"-dimethylpyrano[5",6":7,8]isoflavone (1) and 6-methoxy-3',4'-(methylenedioxy)-7-O-[(E)-3",7"-dimethyl-7"-ol-2",5"-octadienyl]isoflavone (2).

Journal Article↗
PubMed1998

Alamethicin-like behaviour of new 18-residue peptaibols, trichorzins PA. Role of the C-terminal amino-alcohol in the ion channel forming activity.

The influences of peptide length, absence of a Glx (Gln/Glu) residue and the C-terminal amino alcohol on liposome permeabilization and ion-channel characteristics in planar lipid bilayers were examined with two 18-residue peptaibols, PA V and PA IX. As compared to the 20-residue alamethicin, both peptides belonging to the newly isolated trichorzin family, lack a proline in the N-terminal part and one of the two Gln/Glu residues in the C-terminal part of the sequence. The two analogues studied here differ among themselves in their C-terminal amino alcohol (tryptophanol for PA V and phenylalaninol for PA IX). These alpha-helical peptaibols modify to a similar extent the permeability of liposomes, as measured by leakage of a previously entrapped fluorescent probe. Monitoring tryptophanol fluorescence, a greater embedment of the peptide PA V is observed in cholesterol-free bilayers. Macroscopic conductance studies for PA V and PA IX display alamethicin-like current-voltage curves, with a similar voltage dependence, but a smaller mean number of monomers per conducting aggregate is estimated for the tryptophanol analogue, PA V. Single-channel recordings indicate faster current fluctuations for PA IX, while amplitude histograms show lower conductance levels for PA V. Apart from underlining the role of the mismatch between helix length and bilayer hydrophobic thickness, these results stress that the C-terminal tryptophanol favours a stabilization of the conducting aggregates.

Alamethicin↗
PubMed1998

Three-dimensional structure of the ion-channel forming peptide trichorzianin TA VII bound to sodium dodecyl sulfate micelles.

Trichorzianin TA VII, Ac0 U1 A2 A3 U4 J5 Q6 U7 U8 U9 S10 L11 U12 P13 V14 U15 I16 Q17 Q18 Fol19, is a nonadecapeptide member of the peptaibol antibiotics biosynthesized by Trichoderma soil fungi, which is characterized by a high proportion of the alpha, alpha-dialkylated amino acids, alpha-aminoisobutyric acid (Aib, U) and isovaline (Iva, J), an acetylated N-terminus and a C-terminal phenylalaninol (Pheol, Fol). The main interest in such peptides stems from their ability to interact with phospholipid bilayers and form voltage-dependent transmembrane channels in planar lipid bilayers. In order to provide insights into the lipid-peptide interaction promoting the voltage gating, the conformational study of TA VII in the presence of perdeuterated sodium dodecyl sulfate (SDS-d25) micelles has been carried out. 1H sequential assignment have been performed with the use of two-dimensional homo- and -heteronuclear nmr techniques including double quantum filtered correlated spectroscopy, homonuclear Hartmann-Hahn, nuclear Overhauser effect spectroscopy, 1H-13C heteronuclear single quantum correlation, and heteronuclear multiple bond correlation. Conformational parameters, such as 3JNHC alpha H coupling constants, temperature coefficients of amide protons (delta gamma/delta TNH) and quantitative nuclear Overhauser enhancement data, lead to detailed structural information. Ninety-eight three-dimensional structures consistent with the nmr data were generated from 231 interproton distances six phi dihedral angle restraints, using restrained molecular dynamics and energy minimization calculations. The average rms deviation between the 98 refined structures and the energy-minimized average structure is 0.59 A for the backbone atoms. The structure of trichorzianin TA VII associated with SDS micelles, as determined by these methods, is characterized by two right-handed helical segments involving residues 1-8 and 11-19, linked by a beta-turn that leads to an angle about 90 degrees-100 degrees between the two helix axes; residues 18 and 19 at the end of the C-terminal helix exhibit multiple conformations.

Amino Acid Sequence↗
PubMed1998

Conformation and membrane activity of an analogue of the peptaibol antibiotic trichogin GA IV with a lipophilic amino acid at the N-terminus.

We have synthesized by solution-phase methods two analogues of the 11-residue lipopeptaibol antibiotic trichogin GA IV in which the N-terminal n-octanoyl group is replaced either by an N-acetylated 2-amino-2-methyl-L-undecanoic acid or by an N-acetylated alpha-aminoisobutyric acid. CD, FTIR absorption. and NMR analyses unequivocally show that the main structural features of trichogin GA IV are preserved in these analogues. Since only the peptide containing the lipophilic chain exhibits membrane-modifying properties, these results strongly support the view that moving the long acyl moiety from the Nalpha-blocking group to the side chain of the N-terminal extra-residue does not affect the conformational properties or the membrane activity of trichogin GA IV.

Amino Acid Sequence↗
PubMed1998

Solution conformational analysis of amphiphilic helical, synthetic analogs of the lipopeptaibol trichogin GA IV.

The step-by-step synthesis by solution methods of the [Ser2,5,6,9, Leu-OMe11] analog of trichogin GA IV is described. The four Ser residues have been incorporated into the sequence as replacements of the naturally occurring Gly residues to increase the amphiphilicity of the 3D-structure of the lipopeptaibol. A detailed solution conformational analysis has been performed on this undecapeptide and its prototypical [Leu-OMe11] trichogin GA IV analog using FTIR absorption and CD spectroscopies, and two-dimensional NMR under a variety of experimental conditions, including a membrane-mimetic environment. Both peptides adopt a mixed 3(10)/alpha-helical structure, which in the micellar system was found to be less flexible for the Ser-containing analog. For both analogs permeability measurements revealed membrane-modifying properties comparable to those of the natural lipopeptaibol.

Anti-Bacterial Agents↗
PubMed1998

Directed biosynthesis of peptaibol antibiotics in two Trichoderma strains. I. Fermentation and isolation.

Peptaibols are linear alpha-aminoisobutyric acid-containing peptide antibiotics originating from soil fungi mainly of the genus Trichoderma and biosynthesized in complex mixtures of closely related analogues by a polyenzymatic pathway. Addition of amino acids such as alpha-aminoisobutyric acid (Aib), glutamic acid or arginine, to the fermentation medium of two Trichoderma strains, T. harzianum and T. longibrachiatum, has been shown to result in the simplification of the natural peptaibol mixtures, leading in each case to the almost exclusive biosynthesis of a single peptide. Surprisingly, the obtained peptides are Aib-enriched, whether the added amino acid is Aib, Glu or Arg. By adding Aib to the fermentation medium of T. harzianum, two new Aib-rich peptaibols were isolated. Moreover, adding glutamic acid to the culture medium of T. longibrachiatum, which produces both neutral and acidic 20-residue peptaibols with either glutamine or glutamic acid at position 18, increases the production of the acidic peptides. However, arginine which is a positively charged amino acid generally absent from peptaibol sequences, is not incorporated in trichorzins when added to the fermentation medium of T. harzianum.

Amino Acids↗
PubMed1998

Directed biosynthesis of peptaibol antibiotics in two Trichoderma strains. II. Structure elucidation.

Alpha-aminoisobutyric acid-directed biosynthesis in two Trichoderma strains has been shown to lead to the simplification of the natural peptaibol microheterogeneous mixtures and to the production of new analogues. Hence, two new peptides originating from T. harzianum, trichorzin PA(U) 4 and harzianin PCU 4, were isolated by HPLC. Their sequences were determined by positive liquid secondary-ion mass spectrometry (LSI MS). Trichorzin PA(U) 4 and harzianin PC(U) 4 are 18- and 14-residue peptaibols, respectively, both containing a high proportion of alpha-aminoisobutyric acid (Aib). LSI MS performed with lithium cationized peptides, allowed to assign the relative position of leucine/isoleucine isomeric residues, even without the use of tandem mass spectrometry.

Amino Acids↗
PubMed1997

Interaction of the 14-residue peptaibols, harzianins HC, with lipid bilayers: permeability modifications and conductance properties.

Harzianins HC are a series of 14-residue peptaibols containing three Aib-Pro motives separated by sequences of two usual amino acids (Aib-Pro-Xaa-Xaa)n. They are organized in a subtype of the 3(10)-helix, which results in an approximate length of about 27-30 A for the helical rods, allowing them to span a bilayer. Permeabilization of small unilamellar vesicles composed of zwitterionic lipids (egg phosphatidylcholine/cholesterol 7/3 and 8/2) by harzianins HC was observed as well as voltage-gated macroscopic conductance and single-channel formation in planar lipid bilayers (DOPE/POPC 7/3) The permeabilization process was shown to increase with increasing the helix global hydrophobicity. The ion channel-for ming properties appeared rather favoured by an increase in the peptide amphipathicity. The set of conductance levels increasing in geometrical progression, reflecting the sequential uptake and release of monomers which is characteristic of the barrel-stave model for ion-channels described for alamethicin was not observed. The passage of ions through the bilayer would rather be the result of a set of aggregates with fixed numbers of monomers formed in the bilayer. The permeability process and the voltage-gated properties could thus result from different mechanisms showing that harzianins HC can permeabilize membranes via bilayer destabilization or channels, depending on the membrane system, composition and application of voltage.

Amino Acid Sequence↗
PubMed1996

Mucronine J a 14-membered cyclopeptide alkaloid from Zizyphus mucronata.

From the CH2Cl2 extract of the root bark of Z. mucronata (Rhamnaceae), a new cyclopeptide alkaloid, named mucronine J, was isolated together with previously known alkaloids abyssenine A and mucronine D. The structure of mucronine J was elucided by mass spectrometry and 1D and 2D NMR. A solution conformation is proposed on the basis of NOE experiments in combination with MM2 calculations.

Africa, Central↗
PubMed1996

DNA topoisomerase I inhibitors: cytotoxic flavones from Lethedon tannaensis.

From ethyl acetate and methanolic extracts of Lethedon tannaensis leaves, which were cytotoxic against murine leukemia (P-388) and human nasopharynx carcinoma (KB) cells, one new and six known 5-hydroxy-7-methoxyflavones variously substituted on the B ring were isolated and their structures determined by spectral analysis. Compounds active against KB cells were velutin (4) (IC50 4.8 microM), 7,3',5'-tri-O-methyltricetin (2) (IC50 22.2 microM), genkwanin (6) (IC50 30.6 microM), and the novel compound, 7,3',4'-tri-O-methyltricetin, named lethedocin (1) (IC50 47.6 microM). These flavones required the presence of hydroxyl groups at C-5 and C-4' and methoxyl groups at C-7 and C-3' for inhibition of calf thymus DNA topoisomerase I activity.

Animals↗
PubMed1996

Cell wall synthesis is a major target of mycoparasitic antagonism by Trichoderma harzianum.

We have investigated the molecular basis for the reported synergism between peptaibols and cell wall hydrolytic enzymes in the antagonism of phytopathogenic fungi by Trichoderma harzianum. beta-Glucan synthase activity on isolated plasma membranes of Botrytis cinerea was inhibited in vitro by the peptaibols trichorzianin TA and TB, and this inhibition was reversed by the addition of phosphatidylcholine. beta-Glucan synthesis in vivo, assayed by the incorporation of [2-(3)H]glucose into cell wall material, was inhibited by the presence of peptaibols, and this inhibition was synergistic with exogenously added T. harzianum beta-1,3-glucanase. This synergism is therefore explained by an inhibition of the membrane-bound beta-1,3-glucan synthase of the host by the peptaibols, which inhibit the resynthesis of cell wall beta-glucans, sustain the disruptive action of beta-glucanases, and all together enhance the fungicidal activity. Therefore, we have identified cell wall turnover as a major target of mycoparasitic antagonism.

Amino Acid Sequence↗
PubMed1995

Sequencing of hydrophobic peptides as lithiated adducts using liquid secondary-ion mass spectrometry without tandem mass spectrometry.

Lithium cationized hydrophobic peptides in the molecular weight range 1900-2650 Da have been studied by liquid secondary-ion mass spectrometry. The mass spectra exhibit characteristic lithiated sequence ions. N-terminal [a(n)+Li-H]+ and [dn+Li-H]+ ions together with limited C-terminal [ypro+Li+H]+ ions lead to an easy sequencing of the peptides studied, without the need for tandem mass spectrometry.

Amino Acid Sequence↗
PubMed1995

Trichorzins HA and MA, antibiotic peptides from Trichoderma harzianum. I. Fermentation, isolation and biological properties.

Trichorzins HA and MA, original 18-residue peptides, were isolated from two strains of the widespread soil fungus Trichoderma harzianum which have been shown to exhibit antibiotic activity against phytopathogenic fungi. These linear peptides belonging to the peptaibol class are biosynthesized as a complex of closely related analogues. Nine major pure peptides, six trichorzins HA and three trichorzins MA, were isolated by reversed-phase HPLC. The isolated peptides exhibited antibacterial activity against S. aureus and increased the membrane permeability of egg phosphatidylcholine/cholesterol (7/3) liposomes, as measured by monitoring leakage kinetics of a fluorescent probe. Structure-activity relationships were deduced from the antibiotic and membrane-modifying properties.

Amino Acid Sequence↗