Silver-Polymethylhydrosiloxane Nanocomposite Coating on Anodized Aluminum with Superhydrophobic and Antibacterial Properties

Biofilm formation on both animate and inanimate surfaces serves as an ideal bacterial reservoir for the spread of nosocomial infections. Designing surfaces with both superhydrophobic and antibacterial properties can help reduce initial bacterial attachment and subsequent biofilm formation. In the present study, a two-step approach is deployed to fabricate silver-polymethylhydrosiloxane (Ag-PMHS) nanocomposites, followed by a simple dip-coating deposition on anodized Al. Ag-nanoparticles (Ag-NPs) are synthesized in situ within a PMHS polymeric matrix. Morphological features of Ag-PMHS coating observed by scanning electron microscopy shows heterogeneous micro-nano-structures. The chemical compositions of these coatings were characterized using X-ray diffraction and attenuated total reflection-Fourier transform infrared spectroscopy, which indicate the presence of a low-energy PMHS polymer. The as-synthesized Ag-PMHS nanocomposite demonstrated excellent antibacterial properties against clinically relevant planktonic bacteria with zone of inhibition values of 25.3 ± 0.5, 24.8 ± 0.5, and 23.3 ± 3.6 mm for Pseudomonas aeruginosa (P.A) (Gram -ve), Escherichia coli (E. coli) (Gram -ve), and Staphylococcus aureus (S.A) (Gram +ve), respectively. The Ag-PMHS nanocomposite coating on anodized Al provides an anti-biofouling property with an adhesion reduction of 99.0, 99.5, and 99.3% for Pseudomomas aeruginosa (P.A), E. coli, and S. aureus (S.A), respectively. Interestingly, the coating maintained a stable contact angle of 158° after 90 days of immersion in saline water (3.5 wt % NaCl, pH 7.4). The Ag-PMHS nanocomposite coating on anodized Al described herein demonstrates excellent antibacterial and anti-biofouling properties owing to its inherent superhydrophobic property.

2,6-Diphenylthiazolo[3,2-b][1,2,4]triazoles as telomeric G-quadruplex stabilizers

The design and synthesis of 2,6-diphenylthiazolo[3,2-b][1,2,4]triazoles characterized by a large aromatic building block bearing cationic side chains are reported. These molecules are evaluated as telomeric G-quadruplex stabilizers and for their selectivity towards duplex DNA by competition experiments. Two compounds (14a, 19) were found active with high selectivity for telomeric G-quadruplex over duplex DNA.

EPR study of copper(II) complexes of hydroxysalen derivatives in order to be used in the DNA cleavage

Two series of functionalized hydroxy-salen-copper(II) complexes with various side chain lengths have been synthesized. The first one is characterised by amino side chain protected by the tert-butyloxycarbonyl group (Boc) whereas, the second series is obtained by removal of the Boc-protecting group under acidic conditions and formation instead of it an ammonium salt. EPR studies were carried out on the copper(II) complexes. EPR signals attributed to monomers and dimers of Cu2+ species were evidenced. Determination of the copper(II) environment in each complex was attempted using all the experimental results. Square planar and tetrahedral symmetries were found for the copper(II) monomers. From the fine structure observed for the pair signal, the distance between the Cu2+ ions in the pair has been calculated (3.9-4.3A). From these values, it seems that the formation of pairs is obtained by a face-to-face bimolecular association.

ECG Characterization of paroxysmal atrial fibrillation: parameter extraction and automatic diagnosis algorithm

Paroxysmal atrial fibrillation (PAF) is one of the most common heart arrhythmias. It is very difficult to detect unless an explicit Atrial Fibrillation episode occurs during the exploration. The present paper describes a number of low level parameters extracted from ECG traces where no Atrial Fibrillation process is present. The ability of this parameter set to characterize PAF patients is studied and discussed. Based on these parameters a modular automatic classification algorithm for PAF diagnosis is developed and evaluated.

DNA modification by oxovanadium(IV) complexes of salen derivatives

Oxovanadium(IV) complexes of hydroxysalen derivatives have been prepared and tested as DNA reactive agents. The nuclease activity has been investigated under oxidative or reducing conditions, on the basis of the various oxidation states of vanadium: V(III), V(IV) and V(V). In the absence of an activating agent, none of the compounds tested was able to induce cleavage of DNA, whereas in the presence of mercaptopropionic acid (MPA) or Oxone the four complexes induced DNA modifications. Under both conditions, the para-hydroxy complex was found to be the most active compound. Reaction of these salen complexes with DNA occurs essentially at guanine residues and is more efficient in the presence of Oxone than under reducing conditions. The extent of Oxone-mediated DNA oxidation by the four vanadyl complexes was clearly superior to VOSO(4) and was observed without piperidine treatment. EPR studies provided information on the reactive metal-oxo species involved under each conditions and a mechanism of reaction with DNA is discussed.

Design, synthesis and glutathione peroxidase-Like properties of ovothiol-Derived diselenides

Eleven imidazole diselenides derived from the naturally occurring family of antioxidants, the ovothiols, were synthetised by cyclisation of selenoamides with trimethylsilyltrifluoromethanesulfonate or refluxing of cyanoamines in a selenium/sodium borohydride mixture. These compounds were assayed for their glutathione peroxidase-like (GSH Px-like) activity and their capacity to be reduced by glutathione. The most active molecules of the series were 4 times more potent in the GSH Px-like test than the widely known reference compound, ebselen. This catalytic activity was mediated by the formation of the antioxidant selenol intermediate upon partial but significant exchange reaction with glutathione.

Potent mammalian cerebroprotection and neuronal cell death inhibition are afforded by a synthetic antioxidant analogue of marine invertebrate cell protectant ovothiols

Implicit strategies for neuroprotection in the adult brain include GABAA receptor activation, N-methyl-d-aspartate receptor and sodium voltage-gated channel inhibition. Ironically, these same targets may be harmful to the immature or developing brain. Protection has been demonstrated for both immature and mature brain with the use of a synthetic ovothiol analogue. The following beneficial effects have been demonstrated in mice: protection against audiogenic seizures, brain structures with clear-cut delineation of ibotenate-challenged white and grey matter lesions along with exceptional early and delayed protections, and potent cerebral cell death inhibition. The compound lacks both GABAergic activity and sodium channel blocker properties, which may help explain the lack of toxicity normally expressed in an immature brain utilizing these agents [J.W. Olney (2002) Neurotoxicology, 93, 1-10]. The oxidized form of the compound is virtually devoid of antioxidant activity. In vivo it exhibits cerebroprotective properties similar to those of reduced compounds endowed with antioxidant properties. This unexpected finding has prompted an extensive in vitro exploration of underlying molecular mechanisms that have led to the identification of several recycling mechanisms consistent with non rate-limiting conversion of oxidized to reduced compound forms. Taken as a whole, this work offers an unique combined in vitro and in vivo support that: (i). antioxidant therapy, here engineered from marine invertebrate egg protectants, may be a valuable strategy in protecting both mammalian adult and developing brain; and (ii). recycling (thiol-disulphide exchange) properties of the oxidized form of an antioxidant compound are as important as the antioxidant potential exhibited by a bioactive reduced antioxidant in certain neuroprotective processes.

A quantitative study of fault tolerance, noise immunity, and generalization ability of MLPs

An analysis of the influence of weight and input perturbations in a multilayer perceptron (MLP) is made in this article. Quantitative measurements of fault tolerance, noise immunity, and generalization ability are provided. From the expressions obtained, it is possible to justify some previously reported conjectures and experimentally obtained results (e.g., the influence of weight magnitudes, the relation between training with noise and the generalization ability, the relation between fault tolerance and the generalization ability). The measurements introduced here are explicitly related to the mean squared error degradation in the presence of perturbations, thus constituting a selection criterion between different alternatives of weight configurations. Moreover, they allow us to predict the degradation of the learning performance of an MLP when its weights or inputs are deviated from their nominal values and thus, the behavior of a physical implementation can be evaluated before the weights are mapped on it according to its accuracy.

Purification of human ceruloplasmin as a by-product of C1-inhibitor

Human ceruloplasmin (Cp) has been purified from cryoprecipitate-poor plasma as a by-product of the C1-inhibitor production chain. Highly purified Cp was obtained by subsequent ion-exchange chromatography on sulfate-Fractogel EMD and TMAE-Fractogel EMD. Treatments for viral safety included application of the solvent-detergent method and two nanofiltration steps using 35- and 15-nm pore size filters at the end of the process. Overall antigen yield was 95 (+/-5) %. Purified human ceruloplasmin was studied by electron spin resonance (ESR) to characterize its different types of copper complexes and to check its antioxidant properties. We distinguished three types of complexes: one type-2 Cu(II) with g// = 2.25 and A// = 180 G and two type-I Cu(II) exhibiting different narrow hyperfine splitting (A// = 72 G and A// = 90 G) with close g// (2.20 and 2.21). Purified Cp has a specific activity of 24.5+/-0.2 mU/mg of proteins. This process provides a method for Cp purification that could be easily integrated into modern plasma fractionation.

Antioxidant actions of ovothiol-derived 4-mercaptoimidazoles: glutathione peroxidase activity and protection against peroxynitrite-induced damage

4-Mercaptoimidazoles derived from the naturally occurring antioxidants, ovothiols, were tested for their glutathione peroxidase-like (GSH Px-like) activity and protection against peroxynitrite-induced damage. All the thiol compounds displayed similar significant GSH Px-like activities, which are however weaker than that of the reference compound, ebselen. The inhibitions of the peroxynitrite-dependent oxidation of Evans blue dye and dihydrorhodamine 123 showed that the thiol compounds substituted on position 5 of the imidazole ring were nearly as effective as ebselen while the C-2 substituted ones were less effective. Both assays corroborate the large superiority of mercaptoimidazoles over glutathione as inhibitors of peroxynitrite-dependent oxidation.

Antioxidant properties of di-tert-butylhydroxylated flavonoids

Epidemiological evidence suggests an inverse relationship between dietary intake of flavonoids and cardiovascular risk. The biological activities of flavonoids are related to their antioxidative effects, but they also can be mutagenic, due to the prooxidant activity of the catechol pattern. To prevent these problems, we synthesized new flavonoids where one or two di-tert-butylhydroxyphenyl (DBHP) groups replaced catechol moiety at position 2 of the benzopyrane heterocycle. Two DBHP moieties can also be arranged in an arylidene structure or one DBHP fixed on a chalcone structure. Position 7 on the flavone and arylidene or position 4 on the chalcone was substituted by H, OCH(3), or OH. New structures were compared with quercetin and BHT in an LDL oxidation system induced by Cu(II) ions. Arylidenes and chalcones had the best activities (ED(50) = 0.86 and 0.21) compared with vitamin E, BHT, and quercetin (ED(50) = 10.0, 7. 4, and 2.3 microM). Activity towards stable free radical 1, 1-diphenyl-2-picryl-hydrazyl (DPPH) was measured by log Z and ECR(50) parameters. Synthesized flavones proved to be poor DPPH radical scavengers, the activity increasing with the number of DBHP units. In contrast, arylidenes and chalcones were stronger DPPH radical scavengers (log Z > 3, 0.3 < ECR(50) < 2.12) than BHT (log Z = 0.75, ECR(50) = 12.56) or quercetin (log Z = 2.76, ECR(50) = 0.43). Unlike quercetin, synthesized compounds neither chelated nor reduced copper, proving that these new flavonoids had no prooxidant activity in vitro.

4-Mercaptoimidazoles derived from the naturally occurring antioxidant ovothiols 2. Computational and experimental approach of the radical scavenging mechanism

The radical-scavenging mechanism of fourteen 4-mercaptoimidazoles, derived from the natural family of ovothiols, was studied via a QSAR approach, cyclic voltammetry, ESR and NMR spectroscopy. A significant correlation was found between the DPPH scavenging abilities of test compounds and thermodynamic parameters like overall ease of disulphide formation. The production of a disulphide compound via thiyl radical formation is proposed. Upon DPPH scavenging, hydrogen abstraction from thiols yields transient short-lived thiyl radicals, which were characterised by ESR and rapidly dimerise to form a disulphide compound. Cyclic voltammetry showed that the best DPPH scavengers exhibit low oxidation potentials for their oxidation to disulphides.

4-Mercaptoimidazoles derived from the naturally occurring antioxidant ovothiols 1. Antioxidant properties

4-Mercaptoimidazoles derived from the naturally occurring family of antioxidants, the ovothiols, were assayed for their antioxidant properties. These compounds are powerful HOCl scavengers, more potent than the aliphatic thiol N-acetylcysteine. They react slowly with hydrogen peroxide with second order rate constants of 0.13-0.89 M(-1)s(-1). Scavenging of hydroxyl radical occurs at a diffusion-controlled rate (k=2.0-5.0 x 10(10)M(-1)s(-1)) for the most active compounds, which are also able to inhibit copper-induced LDL peroxidation. The combination of radical scavenging and copper chelating properties may explain the inhibitory effects on LDL peroxidation. Two molecules of mercaptoimidazole can chelate a copper ion and form a square planar complex detected by EPR. Compounds bearing an electron-withdrawing group on position 2 of the imidazole ring are the most potent antioxidant molecules in this series.

A new measurement of noise immunity and generalization ability for MLPs

This paper shows a quantitative relation between the regularization techniques, the generalization ability, and the sensitivity of the Multilayer Perceptron (MLP) to input noise. Although many studies about these topics have been presented, in most cases only one of the problems is addressed, and only experimentally obtained evidence is provided to illustrate some kind of correlation between generalization, noise immunity and the use of regularization techniques to obtain a set of weights after training that provides the corresponding MLP with generalization ability and noise immunity. Here, a new measurement of noise immunity for a MLP is presented. This measurement, which is termed Mean Squared Sensitivity (MSS), explicitly evaluates the Mean Squared Error (MSE) degradation of a MLP when it is perturbed by input noise, and can be computed from the statistical sensitivities (previously proposed) of the output neurons. The MSS provides an accurate evaluation of the MLP performance loss when its inputs are perturbed by noise and can also be considered a measurement of the smoothness of the error surface with respect to the inputs. Thus, as the MSS can be used to evaluate the noise immunity or the generalization ability, it gives a criterion to select among different weight configurations that present a similar MSE after training.

DNA cleavage by hydroxy-salicylidene-ethylendiamine-iron complexes

Bis(hydroxy)salen.Fe complexes were designed as self-activated chemical nucleases. The presence of a hy-droxyl group on the two salicylidene moieties serve to form a hydroquinone system cooperating with the iron redox system to facilitate spontaneous formation of free radicals. We compared the DNA binding and cleaving properties of the ortho -, meta- and para -(bishydroxy) salen.Fe complexes with that of the corresponding chelate lacking the hydroxyl groups. DNA melting temperature studies indicated that the para complex exhibits the highest affinity for DNA. In addition, this para compound was considerably more potent at cleaving supercoiled plasmid DNA than the regio-isomeric ortho - and meta -hydroxy-salen.Fe complexes, even in the absence of a reducing agent, such as dithiothreitol used to activate the metal complex. The DNA cleaving activity of the para isomer is both time and concentration dependent and the complexed iron atom is absolutely essential for the sequence uniform cleavage of DNA. From a mechanistic point of view, electron spin resonance measurements suggest that DNA contributes positively to the activation of the semi-quinone system and the production of ligand radical species responsible for subsequent strand scission in the absence of a reducing agent. The para -hydroxy-salen.Fe complex has been used for detecting sequence-specific drug-DNA interactions. Specific binding of Hoechst 33258 to AT sequences and chromomycin to GC sequences were shown. The para -bis(hydroxy)salen.Fe derivative complements the tool box of footprinting reagents which can be utilised to produce efficient cleavage of DNA.

Stimulus correlation and adaptive motion detection using spiking neurons

Stimulus correlation and adaptive movement detection, among other tasks can be performed with VLSI general-purpose neurons that have controllable steady and transient responses. This paper presents experimental results of simple neural primitives based on the CMOS neuron approach described in [11]. Stimulus correlation experiments illustrate the well defined behavior of the CMOS approach. This basic primitive is used to implement motion detectors with adaptive capabilities that enable it to work efficiently in a wide velocity range.

Synthesis, DNA binding, topoisomerase II inhibition and cytotoxicity of two guanidine-containing anthracene-9,10-diones

Two anthraquinone derivatives of the anticancer drugs mitoxantrone and ametantrone were examined for their ability to bind to DNA and to modulate the formation of topoisomerase-DNA cleavable complexes in vitro. The guanidinium groups introduced at the termini of the two aminoethylamino side chains of mitoxantrone can reinforce the interaction with DNA as judged from thermal denaturation studies with calf thymus DNA and polynucleotides. Footprinting experiments indicate that the binding to DNA of compound SR107 lacking the 5,8-hydroxyl substituents is essentially nonspecific whereas its congener SR 103 interacts preferentially with GC-rich sequences, particularly those containing 5'-(A/T)CG sites. Compound SR103, which bears two hydroxyl groups on the anthraquinone chromophore, promotes the cleavage of DNA by topoisomerase II and is cytotoxic toward human KB carcinoma cells in vitro. In contrast, the analogue SR107, which lacks OH groups, has no effect on topoisomerase II and is not cytotoxic.

Synthesis, DNA binding, and cleaving properties of an ellipticine-salen.copper conjugate

The synthesis of a DNA-cutting agent that conjugates an ellipticine chromophore and a copper complex of bis(salicylidene)ethylenediamine, referred to as a salen, is reported. The presence of the salen.Cu complex allows cleavage of DNA via oxygen-based radicals, and the ellipticine moiety serves as a DNA anchor. Spectroscopic measurements indicate that the intercalation geometry of the ellipticine chromophore is preserved with the hybrid. The cleavage is much more efficient with the conjugate than with the Schiff base copper complex alone.

Salen-anthraquinone conjugates. Synthesis, DNA-binding and cleaving properties, effects on topoisomerases and cytotoxicity

A series of amidoethylamino-anthraquinone derivatives bearing either one or two salen (bis(salicylidene)ethylenediamine) moieties complexed with CuII or NiII have been synthesized, and their DNA-binding and cleaving properties examined. The effects of the mono- and di-substituted anthracenedione-salen conjugates on DNA cleavage mediated by topoisomerases I and II have also been determined, as well as their cytotoxicity toward human KB cells. The anthraquinone-salen. NiII conjugates bind to GC-rich sequences in DNA, but do not cleave the macromolecule. By contrast, the anthraquinone-salen. CuII hybrids do not recognize particular nucleotide sequences but efficiently induce single-strand breaks in DNA after activation. The 5,8-dihydroxy-anthraquinone conjugates are more cytotoxic and more potent toward topoisomerase II than the non-hydroxylated analogues, but they are less cytotoxic than the salen-free anthraquinones. The attachment of a salen. CuII complex to the anthraquinone chromophore can confer DNA cleaving properties in vitro, but this is at the expense of cytotoxic activity. Anthraquinone-salen. CuII complexes may find useful employ as footprinting probes for investigating ligand-DNA interactions.

One-electron oxidation of ergothioneine and analogues investigated by pulse radiolysis: redox reaction involving ergothioneine and vitamin C

Redox reactions of endogenous and exogenous sulphur-containing compounds are involved in protection against oxidative damage arising from the incidence and/or treatment of many diseases, including cancer. We have investigated, via pulse radiolysis, the one-electron oxidation of ergothioneine, a molecule with antioxidant properties which is detected at millimolar concentrations in certain tissues and fluids subject to oxidative stress, including erythrocytes and plasma. The spectrum of the transient species, assigned to the product of one-electron oxidation, observed after reaction of ergothioneine with the oxidizing radicals OH., N3. and CCl3O2. has a maximum absorption at 520 nm and is very similar to that obtained by oxidation of analogous molecules such as 2-mercaptoimidazole, 1-methyl-2-mercaptoimidazole, S-methyl- and S,N-dimethyl-ergothioneine. In the presence of vitamin C, the oxidized form of ergothioneine is repaired by a rapid reduction (k = 6.3 x 10(8) M(-1).s(-1)) producing ascorbyl radicals. This co-operative interaction between ergothionine and ascorbate, similar to that previously observed between vitamin E and ascorbate, may contribute to essential biological redox protection.

DNA recognition by two mitoxantrone analogues: influence of the hydroxyl groups

The clinically useful anticancer drug mitoxantrone intercalates preferentially into 5'-(A/T)CG and 5'-(A/T)CA sites on DNA. The 5,8 hydroxyl substituents on its anthracenedione chromophore are available to interact with the double helix. Footprinting experiments with two anthraquinone derivatives structurally related to mitoxantrone and ametantrone have been undertaken to assess the influence of the hydroxyl groups on the DNA recognition process. The results confirm that they do play a role in the recognition of preferred nucleotide sequences and suggest that the binding of anthraquinones to a 5'-(A/T)CG site is dependent on the presence of the 5,8 hydroxyl substitutes whereas binding to 5'-(A/T)CA sites appears to proceed just as well without them.

Antioxidant properties of hydroxy-flavones

The antioxidant properties of 24 hydroxy-flavones were evaluated. Results show that 2',3',4'-OH substitution on the B ring plays a crucial role in radical scavenger activity in the DPPH assay and in the inhibitory effect on pereoxydation of tissue lipids in the MDA test. The formation of stable radicals for this type of compounds has been studied by ESR. In addition, it has been found that 7-hydroxy-flavones are potent competitive inhibitors of xanthine oxidase. It is proposed that the C-7 OH of flavones may take the place of the C-2 or C-6 OH of xanthine in the active site of the enzyme. A C-4' OH or C-4' OMe substitution on the 7-hydroxy flavones is not favourable to a fit in the active site. The 2',3',4'-trihydroxy-flavones inhibited XO by another process, which remains to be determined. In summary, this study provides evidence that hydroxy-flavones exhibit interesting antioxidant properties expressed either by the capacity to scavenge free radicals (for 2',3',4'-trihydroxy-flavones) or to competitively inhibit xanthine oxidase (for 7-hydroxy-flavones). These compounds may be drug candidates for treating pathologies related to free radical oxidation.

Benzoselenazolinone derivatives designed to be glutathione peroxidase mimetics feature inhibition of cyclooxygenase/5-lipoxygenase pathways and anti-inflammatory activity

Two series of compounds, substituted benzoselenazolinones and their opened analogs, diselenides, were prepared. The diselenides were designed according to the available SAR about glutathione peroxidase mimics and were expected to have activity. An initial series of tests was performed in order to assess the glutathione peroxidase and antioxidant activity of the diselenides compared to their cyclized analogs. The diselenides were shown to be very potent (up to 3 times the activity of ebselen), whereas the benzoselenazolinones were inactive, thus confirming our hypothesis. A second series of tests was done to determine the anti-inflammatory potency of the two series. Both were found to be potent on cyclooxygenase and 5-lipoxygenase pathways (up to 95% inhibition at 10(-5) M). Some compounds were selective, and the variations in the activity allowed us to draft some structure-activity relationships. The most interesting compound of each series, 6-benzoylbenzoselenazolinone and bis[(2-amino-5-benzoyl)phenyl] diselenide, was tested in vivo on the rat foot edema induced with different phlogistic agents and was shown to have some anti-inflammatory properties.

Synthesis and antitumor properties of an anthraquinone bisubstituted by the copper chelating peptide Gly-Gly-L-His

A new molecule 4 [(GGH-DAE)2DHQ] associating the 1,4,5,8-tetrahydroxyanthraquinone ring (DHQ) of the antitumor drug mitoxantrone (2), two diaminoethylene chains (DAE), and the metal-chelating peptide Gly-Gly-His (GGH) has been synthesized. Such a molecule presents characteristics able to induce antitumor activity: compound 4 intercalates into DNA as measured by delta Tm, fluorescence quenching, and viscometry; ESR studies demonstrate that several types of Cu complexes are formed depending on pH; and the production of free radicals, as evidenced by spin-trapping, is enhanced by 4. In vitro, in leukemia cells L1210 and mammary cells MCF7, 4 is slightly less cytostatic than mitoxantrone, but substantially less toxic. In vivo, in leukemia P388 on mice, a T/C value of 230 is obtained at 25 mg/kg, higher than the one of mitoxantrone, which is toxic at the same dose.

Synthesis of a biospecific adsorbent for the purification of the three human retinoic acid receptors by affinity chromatography

The total synthesis of an affinity gel suitable for the purification of retinoic acid receptors (hRARs) is reported. A chalcone derived from a potent retinobenzoic acid (Ch55) was chosen as the ligand and fixed to an immobilized matrix by coupling with the N-hydroxysuccinimide ester of agarose (Affi-Gel 10, Bio-Rad Laboratories). Efficiencies of purification of the different human RARs were tested, using recombinant receptors produced with the baculovirus expression system.

Scavenger and antioxidant properties of ten synthetic flavones

To study the effect of the hydroxyl groups on biological activities of flavones, we synthesized 10 polyhydroxyflavones with varied substitution patterns. The abilities of the 10 compounds to act as radical scavengers were investigated using chemiluminescence in two biological models: the xanthine/xanthine oxidase system and the oxidative burst of rat alveolar macrophages. Stable radical formation was observed by electron spin resonance (ESR) spectroscopy. We found that the presence of the pyrogallol moiety in the B component of flavones gave rise to radical scavenger activity and that C-6 substituted hydroxyl group may also provide the basis for biological activity. Furthermore, compounds with a hydroxyl at C-7 position appeared to be xanthine oxidase inhibitors. One particular compound exhibited radical scavenger activity and xanthine oxidase inhibition. This type of compound should prove to be useful in the treatment of ischemia, for which both properties were required.

Redox chemistry of complexes of nickel(II) with some biologically important peptides in the presence of reduced oxygen species: an ESR study

The reactions between some Ni(II) oligopeptides (Gly-His-Lys, (Gly)4, Asp-Ala-His-Lys, Gly-Gly-His, beta Ala-His, and serum albumin) and reduced oxygen species have been characterized by spin-trapping experiments using DMPO and Me2SO. Most of the peptides possessed superoxide dismutase- and catalase-like activities leading to the formation of either oxene [NiO]2+ or, in the case of beta Ala-His, hydroxyl radicals. Both these species may affect DNA integrity through distinct mechanisms.

The coordination of copper(II) to 1-hydroxy-4-(glycyl-histidyl-lysine)-anthraquinone; a synthetic model of anthraquinone anti-cancer drugs

Results are reported of a pH-metric and spectroscopic (CD and ESR) study of the complexes formed between the pseudo-peptide 1-hydroxy-4-(Gly-His-Lys)-anthraquinone (Q-GHK) since, when complexed to copper ions, Q-GHK has been shown to be very effective in promoting the formation of free radicals and inducing DNA cleavage. Q-GHK forms very stable complexes with copper, the major species being bonded to three nitrogen donors in the coordination plane: an imidazole-N of the His residue and the peptide nitrogens of the Gly and His residues. This species is probably stabilized through bonding of the fourth planar coordination site of Cu(II) to the 9-anthraquinone oxygen. At high Q-GHK:copper ratios a second Q-GHK molecule is coordinated through its imidazole-N donor.

Electron microscopic observations of the effects of anthraquinone derivatives on plasmid DNA

Electron microscopy was used to analyse the precipitation of DNA observed when mixed with two tripeptide derivatives of mitoxantrone, with or without a 5,8-dihydroxy group (DHQ-GHK and Q-GHK, respectively) on the anthraquinonic ring. This precipitation was compared to that obtained with the basic drugs, mitoxantrone (DHAQ) and ametantrone (AQ). The effects of these compounds on the supercoiling of form I and the lengthening of form II of pBR322 DNA molecules, respectively, were evaluated. A strong lengthening of the DNA molecules was observed for ametantrone (max: 57%), but only 32% for Q-GHK, both at r (drug/base pari) = 250. With the dihydroxy derivative DHQ-GHK, it was not possible to show more than a 10% increase in length because DNA molecules were not measurable at r greater than 100. Only Q-GHK relaxed supercoiled molecules at the low r values of 10. Complex phenomena of condensation-precipitation were observed with these two tripeptide derivatives. In addition to a strong lengthening of form II DNA molecules, AQ induced specifically the formation of toruses, and DHAQ that of large organized DNA condensation. The variety of the aggregations is described and discussed with regard to the antitumor properties of these derivatives, and the literature concerning the various descriptions of DNA aggregation.

Generation of free radicals by simple prenylated hydroquinone derivatives, natural antitumor agents from the marine urochordate Aplidium californicum

The redox properties of simple prenylated hydroquinone derivatives with cytotoxic properties have been studied by absorption and ESR spectroscopies. Both methods evidenced an autoxidation process in which the hydroquinones give rise to a semiquinone radical. Molecular oxygen is the electron acceptor, as demonstrated by spin trapping. No secondary radicals were found in the ESR spectra, either in the presence of hydroxyl anion (alkaline medium) or in the presence of glutathione. Nevertheless, a redox cycle can be initiated by glutathione, giving rise to substantial free-radical production. Thus, although not fully elucidated, the antitumor properties of the three hydroquinones described here can be correlated with their redox properties and their reactivity with thiol-containing peptides such as glutathione.

Antioxidant properties of natural hydroquinones from the marine colonial tunicate Aplidium californicum

Antioxidant prenylated hydroquinones and non active chromene or chroman extracted from the marine colonial tunicate Aplidium californicum have been studied in order to throw some light on their biological activity. It has been found that the active compounds inhibit superoxide anion production in rat alveolar macrophages and in the xanthine/xanthine oxidase system. The antioxidant activity may be ascribed rather to a direct reaction of the superoxide anion with the hydroquinones than to an enzymatic inhibition or a membrane signal transfer. A physiological activity close to that of alpha tocopherol can be considered.

Free radical production and DNA cleavage by copper chelating peptide-anthraquinones

Two pseudopeptides incorporating a peptide metal-chelating moiety (Gly-His-Lys) and a polyhydroxy anthraquinone ring related to the nuclei of anti-tumor drugs such as mitoxantrone and ametantrone, have been synthesized. The goal was to conjugate the redox effects of a quinone ring with the iron-chelating properties of the peptide in order to generate free radical species capable of damaging DNA. Indeed quinone-containing drugs undergo, in vivo, one-electron reduction to the corresponding semiquinone radicals which, in the presence of molecular oxygen, produce a superoxide anion radical, hydrogen peroxide and ultimately, in the presence of metal, hydroxyl radical (Fenton reaction). Hydroxyl radicals (OH.) are short-lived and extremely reactive with their bioenvironment. The interaction of both drugs with DNA has been studied by fluorescence quenching and DNA melting experiments. Spectroscopic and e.s.r. studies demonstrated that several types of Cu-complex are formed depending on the copper-drug ratio. The production of free radicals, as evidenced by spin-trapping, is optimum with a Cu/drug ratio of 0.1; in this case the metal ion is chelated by the peptide moiety. This latter complex is able to induce DNA breakage at a high level. Thus, it appears that the proposed concept works but that care must be taken in the choice of the relative concentration of copper.

Plasma membrane perturbations of KB3 cells induced by the bleomycin-iron complex

The effect of the anticancer drug bleomycin on acyl chain order of KB cell membranes was examined by electron paramagnetic resonance and fluorescence polarization spectroscopies using respectively, the 5-doxyl stearic acid spin probe and the 1,6-diphenyl-1,3,5-hexatriene and the 1-[4-(trimethylammonio)phenyl]-6-phenyl-1,3,5-hexatriene fluorescent probes. Measurements of the order parameter, S, by the two techniques showed a perturbation of the plasma membrane fluidity with bleomycin-iron, while no effect was observed with bleomycin or iron alone. A kinetic study of the location of the 1,6-diphenyl-1,3,5-hexatriene fluorescent probe into the cell was followed by fluorescence microscopy. Lipid peroxidation measurements were also performed using isolated unsaturated lipids, intact cells, or isolated plasma membranes whose purity was checked by electronic microscopy. These membrane perturbation effects not observed with bleomycin-iron in the presence of a hydroxyl radical scavenger, dimethyl thiourea, or a chelating agent, desferrioxamine, were correlated with the ability of the complex to generate highly reactive oxygen species.

Synthesis, biological activity and DNA interaction of anilinoacridine and bithiazole peptide derivatives related to the anti-tumor drugs m-AMSA and bleomycin

The synthesis of two depsipeptides including a peptide metal-chelating moiety (Gly-His-Lys) and a moiety with DNA affinity, namely either glycyl-anilino-9-aminoacridine 1 or 2'-(2-aminoethyl)-4-methoxycarbonyl-2",4'-bithiazole 2, has been carried out. The goal was to introduce separately on the same molecule the two factors contributing to the biological activity of many anti-tumor drugs. The interaction of both drugs with DNA has been studied and the acridine ring of 1 was found to intercalate in the double helix. The production of free radicals has been evidenced by spin-trapping for 1 although both compounds were revealed to be good copper-chelating agents. In vitro cytostatic activity and inhibition of [3H]-thymidine incorporation were obtained for 1 while 2 exhibited no activity in both tests. In view of these results, it can be pointed out that the anti-tumor properties of such drugs rely (1) on their ability to reach and to bind DNA and (2) on redox mechanisms involving interactions between the drugs, metals and molecular oxygen. The latter phenomenon leads to the formation of active radical species, able to degrade the DNA.

2,3-bis(2-pyridyl)-5,8-quinoxalinediones with metal chelating properties: synthesis and biological evaluation

The synthesis of 2,3-bis(2-pyridyl)-5,8-quinoxalinediones has been carried out in order to provide new antitumor drugs related to streptonigrin. Some derivatives have been found to possess significant cytotoxic properties and their mechanism of action has been studied. They were found to induce single-strand cleavage of covalently closed circular DNA (ccc-DNA). This biological activity requires an apparent in situ reduction (NADH activation) of the quinone to a hydroquinone or semiquinone radical, is facilitated by the presence of Cu(II), and involves activation of molecular oxygen to highly reactive radical species. Thus, although less active than the parent drugs, these molecules provide an attractive rationale for the observed cytotoxic and antitumor potency, as well as the cell-free single strand DNA cleavage efficacy of that family of drugs.

Effect of combination of m-AMSA and doxorubicin on their redox properties and on DNA cleavage

In vitro studies with the drug combination m-AMSA and doxorubicin were carried out in order to point out whether they can form a redox-system. Indeed, while doxorubicin is known to be bioactivated by NADPH cytochrome P-450 reductase, m-AMSA is readily and reversibly oxidized either chemically or microsomally, to give a quinone diimine with electrophile properties. This redox chemistry has been shown to play a major role in the antineoplastic properties of both drugs. The oxidation of m-AMSA was followed by absorption spectroscopy and the reduction of doxorubicin was observed by circular dichroism. It has been found that both drugs may form a redox-couple and that their association enhances their ability to cut DNA in the absence of cupric ions. Indeed, doxorubicin catalyses the oxidation of m-AMSA in sodium borate buffer (pH 9.25) and conversely the chemical reduction of doxorubicin by m-AMSA induces single and double strand breaks in pBR 322 DNA. This chemical activation may be of importance in vivo, and perhaps the combination of both drugs may lead to a therapeutic advantage.

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.