2‐Hydroxynaphthalene‐1‐carbaldehyde‐ and 2‐(Aminomethyl)pyridine‐Based Schiff Base CuII Complexes for DNA Binding and Cleavage

Three mononuclear Cu^II complexes, [CuCl(naph‐pa)] ( 1 ), [Cu(bipy)(naph‐pa)]Cl ( 2 ), and [Cu(naph‐pa)(phen)]Cl ( 3 ) ((naph‐pa)=Schiff base derived from the condensation of 2‐hydroxynaphthalene‐1‐carbaldehyde and 2‐picolylamine (=2‐(aminomethyl)pyridine), bipy=2,2′‐bypiridine, and phen=1,10‐phenanthroline) were synthesized and characterized. Complex 1 exhibits square‐planar geometry, and 2 and 3 exhibit square pyramidal geometry, where Schiff base and bipy/phen act as NNO and as NN donor ligands, respectively. CT (Calf thymus)‐DNA‐binding studies revealed that the complexes bind through intercalative mode and show good binding propensity (intrinsic binding constant K_b: 0.98×10⁵, 2.22×10⁵, and 2.67×10⁵ M ^?1 for 1 – 3 , resp.). The oxidative and hydrolytic DNA‐cleavage activity of these complexes has been studied by gel electrophoresis: all the complexes displayed chemical nuclease activity in the presence and absence of H₂O₂. From the kinetic experiments, hydrolytic DNA cleavage rate constants were determined as 2.48, 3.32, and 4.10 h^?1 for 1 – 3 , respectively. It amounts to (0.68–1.14)×10⁸‐fold rate enhancement compared to non‐catalyzed DNA cleavage, which is impressive. The complexes display binding and cleavage propensity to DNA in the order of 3 > 2 > 1 .     

Biosynthesis stimulation of nor‐secotriterpene anxiolytics in cell suspension cultures of Galphimia glauca Cav

Galphimia glauca produces compounds denominated galphimines (galphimine‐A, galphimine‐B and galphimine‐E). Due to their important anxiolytic activity, we initiated in vitro cultures of the species with the purpose of developing a biotechnological process for obtaining galphimines. In this work, we stimulated the biosynthesis and excretion of galphimines with two‐phase batch‐type cell suspension cultures of G. glauca. The effect of nutritional variation and the 2,4‐dichlorophenoxy acetic acid added to Murashige & Skoog(MS) culture medium was evaluated. Later, we evaluated the effect of the stimulation with calcium and methyl jasmonate (MeJ). The greatest production of galphimine‐B (3.39 × 10^?5 g/L day^?1) was obtained on day 40 of kinetics, and induced by a treatment containing concentrations of nitrates and phosphate that are double of those normally used in MS medium, without sucrose but with added 2,4‐dichlorophenoxy acetic acid (4 mg/L). Time of galphimine‐B biosynthesis diminished due to the effect of MeJ in combination with calcium, and induced the excretion (100%) of galphimine‐B (6.35 × 10^?5 g/L day^?1) into the culture medium. Thus, the use of calcium and MeJ comprises a viable alternative to stimulate the production and excretion of galphimine‐B and galphimine‐A in batch‐type cultures of G. glauca in modified MS medium. Once optimized, the production of the anxiolytic compounds can be scaled up to the industrial level.     

Differential in vitro inhibition of polyphenoloxidase from a wild edible mushroom Lactarius salmonicolor

The polyphenol oxidase (LsPPO) from a wild edible mushroom Lactarius salmonicolor was purified using a Sepharose 4B-L-tyrosine-p-amino benzoic acid affinity column. At the optimum pH and temperature, the K_M and V_Max values of LsPPO towards catechol, 4-methylcatechol and pyrogallol were determined as 0.025 M & 0.748 EU/mL, 1.809 × 10^{? 3} M & 0.723 EU/mL and 9.465 × 10^{? 3} M & 0.722 EU/mL, respectively.

Optimum pH and temperature values of LsPPO for the three substrates above ranged between the pH 4.5–11.0 and 5–50°C. Enzyme activity decreased due to heat denaturation with increasing temperature. Effects of a variety of classical PPO inhibitors were investigated opon the activity of LsPPO using catechol as the substrate. IC₅₀ values for glutathione, p-aminobenzenesulfonamide, L-cysteine, L-tyrosine, oxalic acid, β-mercaptoethanol and syringic acid were determined as 9.1 × 10^{? 4}, 2.3 × 10^{? 4} M, 1.5 × 10^{? 4} M, 3.8 × 10^{? 7} M, 1.2 × 10^{? 4} M, 4.9 × 10^{? 4} M, and 4 × 10^{? 4} M respectively. Thus L-tyrosine was by far the most effective inhibitor. Interestingly, sulfosalicylic acid behaved as an activator of LsPPO in this study.     

Three‐dimensional (3‐D) fluorescence spectroscopy analysis of the fluorescent dissolved organic matter released by the marine toxic dinoflagellate Alexandrium catenella exposed to metal stress by zinc or lead

We investigated the effects of zinc or lead on growth and on exudation of fluorescent dissolved organic matter (FDOM) by the marine toxic dinoflagellate Alexandrium catenella (Whedon & Kofoid) Balech. The species was exposed to increasing free zinc (1.34 × 10^?7 M–3.98 × 10^?6 M) or lead (5.13 × 10^?9 M–1.82 × 10^?7 M) concentra‐tions. Low metal levels ([Zn²⁺] = 1.34 × 10^?7 M; [Pb²⁺] = 5.13 × 10^?9 M) had no effect on cell growth. Toxic effects were observed from higher metal contamination ([Zn²⁺] = 3.98 × 10^?6 M; [Pb²⁺] = 6.54 × 10^?8 M), as a conversion of vegetative cells into cysts. Analysis of the released FDOM by three‐dimensional (3‐D) fluorescence spectroscopy was achieved, using the parallel factor analysis (PARAFAC). The PARAFAC modeling revealed four components associated with two contributions: one related to the biological activity; the other linked to the organic matter decomposition in the culture medium. The C1 component combined a tryptophan peak and characteristics of humic substances, whereas the C2 component was considered as a tryptophan protein fluorophore. The two others C3 and C4 components were associated with marine organic matter production. Relea‐sed fluorescent substances were induced by low ([Zn²⁺]= 1.34 × 10^?7 M; [Pb²⁺] = 5.13 × 10^?9 M) and moderate ([Zn²⁺] = 6.21 × 10^?7 M; [Pb²⁺] = 2.64× 10^?9 M) metal concentrations, suggesting the activation of cellular mechanisms in response to metal stress, to exudate FDOM that could complex metal cations and reduce their toxicity toward A. catenella cells.     

Catalytic resonance scattering spectral determination of ultratrace horseradish peroxidase using rhodamine S

A highly sensitive and selective resonance scattering spectral assay was proposed for the determination of horseradish peroxidase (HRP), based on its catalytic effect on the H₂O₂ oxidation of KI to form I₃^?. The I₃^? combined respectively with rhodamine (Rh) dye such as rhodamine S (RhS), rhodamine 6G (Rh6G), rhodamine B (RhB) and butyl‐rhodamine B (b‐RhB), to form association particles (Rh‐I₃)_n. The four Rh systems all exhibit a stronger resonance scattering (RS) peak at 424 nm. For the RhS, Rh6G, RhB and b‐RhB systems, HRP concentration in the range of 3.2 × 10^?12 to 4.8 × 10^?9, 2 × 10^?11 to 3.2 × 10^?9, 1.6 × 10^?11 to 3.2 × 10^?9 and 1.6 × 10^?11 to 4 × 10^?9 g/mL was linear to its RS intensity at 424 nm, with a detection limit of 2.2 × 10^?12, 2.5 × 10^?12, 4.4 × 10^?12 and 2.6 × 10^?12 g/mL, respectively. This RhS system was most sensitive and stable, and was applied for the determination of HRP in the hepatitis B surface antibody labeling HRP and water samples, with satisfactory results. Copyright © 2009 John Wiley & Sons, Ltd.     

Understanding nucleosomal histone and DNA interactions: a biophysical study

Histones are associated with DNA to form nucleosome essential for chromatin structure and major nuclear processes like gene regulation and expression. Histones consist of H1, H2A, H2B and H3, H4 type proteins. In the present study, combined histones from calf thymus were complexed with ct DNA and their binding affinities were measured fluorimetrically. All the five histones were resolved on SDS page and their binding with DNA was visualized. The values of biding affinities varied with pH and salt concentration. Highest affinity (4.0?×?10⁵ M^?1) was recorded at pH 6.5 in 50 mM phosphate buffer and 1.5?×?10⁴ M^?1 in 2 M NaCl at pH 7.0. The CD spectra support the highest binding affinity with maximum conformational changes at pH 7.0. The time-resolved fluorescence data recorded two life times for histone tyrosine residues at 300 nm emission in phosphate buffer pH 6.5. These life times did not show much change upon binding with DNA in buffer as well as in 2 M NaCl. The isothermal calorimetric studies yielded thermodynamic parameters ΔG, ΔH and ΔS as ?1.6?×?10⁵ cal/mol, ?1.13?×?10³ cal/mol and ?3.80 cal/mol/deg, respectively, evidencing a spontaneous exothermic reaction. The dominant binding forces in building the nucleosome are electrostatic interactions.     

Effect of ortho-dihydroxyphenols on growth and protein pattern of callus cultures from Prunus avium

Excised shoot discs from Prunus avium L. were cultivated on a modified Murashige and Skoog medium for 4 weeks under long day conditions. The basal medium was supplemented with IAA and benzylaminopurine. Further addition of 5.7 × 10^?5 resp, 11.4 × 10^?5M catechin and 4.25 × 10^?5 resp. 8.5 × 10^?5M chlorogenic acid resulted in a highly significant promotion of callus proliferation. Proteins and enzymes were separated by isoelectric focusing. The supply of both polyphenols resulted in a higher number and intensity of protein bands including esterases as compared to controls.     

Zinc as a co-factor for an enzyme involved in exsheathment of Haemonchus contortus

The activity of concentrated exsheathing fluid of Haemonchus contortus against isolated sheaths was not inhibited by ethylenediamine tetra-acetic acid (EDTA), 10^?2 M, even when the concentrations of Mg and Mn were < 4 × 10^?4 M and < 0·9 × 10^?6 M respectively. Purified or diluted solutions of exsheathing fluid, even in the presence of Mg²⁺, 10^?3 M, were inhibited. Leucine aminopeptidase (LAP) in exsheathing fluid was active even at concentrations of Mg < 1·3 × 10^?5M. Concentrated solutions were partially inhibited by EDTA, 10^?2 M, at low concentrations of Mg; inhibition was increased in diluted and purified preparations.1,10-phenanthroline (Ophen) strongly inhibited exsheathing activity (Zn < 1 × 10^?6 M). When Zn²⁺, 10^?3 M was added, the inhibition was abolished. The hydrolysis of l-leucinamide was greatly increased in the presence of Ophen, 10^?4 M; this effect was abolished by adding Zn²⁺, 10^?3 M.It is suggested that exsheathing fluid from at least some ‘strains’ of H. contortus contains a Zn metallo-enzyme, probably LAP, which is involved in the process of exsheathment.     

Direct chemiluminescence determination of penicillin G potassium and a chemometrical optimization approach

A highly selective and simple chemiluminescence (CL) method for determination of penicillin G potassium (PGK) was developed. In the proposed method, CL was elicited from PGK upon its oxidation with H₂O₂. The light emission was enhanced in the presence of N‐cetyl‐N,N,N‐trimethylammonium bromide (CTMAB). An experimental design, central composite design (CCD), was used to realize the optimized variables, including pH, surfactant (CTMAB) and H₂O₂ concentrations. Under optimum condition, the calibration graph was linear in the range 3.3 × 10^?3–3.3 × 10^?1 mmol/L, with a detection limit of 8.8 × 10^?4 mmol/L for PGK. The precision was calculated by analysing samples containing 1.6 × 10^?1 mmol/L PGK (n = 5) and the relative standard deviation (RSD) was 1.40%. The utility of this method was demonstrated by determining PGK in pharmaceutical formulations for injection. The proposed method was validated by a reference method. Copyright © 2011 John Wiley & Sons, Ltd.     

Induction of deflagellation by various local anesthetics in Chlamydomonas reinhardtii Dangeard (Chlamydomonadales,Chlorophyceae)

Dibucaine, a local anesthetic, is known to induce flagellar excision in Chlamydomonas reinhardtii. Herein, we investigate whether other local anesthetics have similar effects. Tetracaine, bupivacaine, procaine, and lidocaine also caused flagellar excision, although their potencies were lower than that of dibucaine. Bupivacaine, procaine, and lidocaine induced a morphological change in flagella from a rod‐like shape to a disk‐like shape before flagellar excision. Except for lidocaine, these local anesthetics caused cell‐wall shedding in addition to flagellar excision. The anesthetics in order of their median effective concentration (1‐h EC₅₀) for flagellar excision are as follows: dibucaine (1.37 × 10^?5 M) < tetracaine (3.16 × 10^?5 M) < bupivacaine (4.25 × 10^?4 M) < procaine (2.02 × 10^?3 M) < lidocaine (3.61 × 10^?3 M). In all cases, Ca²⁺ depletion from the solution inhibited flagellar excision. However, Ca²⁺‐channel blockers, IP3 receptor antagonists, and inhibitors of phospholipase C did not prevent excision. We suggest that the local anesthetics induce flagellar excision by increasing the fluidity of the flagellar/cell membrane, thereby allowing extracellular Ca²⁺ to flow into the cell and cause flagellar excision.     

The Effect of Environmental Conditions on the Expression of Disease in Cultured Tissues of Brassica napus ssp. oldfera Infected with Leptosphaeria maculans

As a basis for devising an in vitro screening programme, culture conditions were optimized so that tissue cultures from two resistant cultivars of Brassica napus ssp. oleifera (Mikado, Bienvenu) and two susceptible cultivars (Lesira, Ceres) could be differentiated using a disease scoring scheme, when inoculated with Leptosphaeria maculans. Tissues inoculated included thin cell layer explants from soil-grown plants and in vitro-grown shoot cultures and callus tissue formed on such explants. The period of incubation and the incubation temperature were of importance in the development of differential disease reactions. Increasing temperature generally resulted in an increase in infection and too great an incubation period resulted in total overgrowth of the tissue. Increasing concentrations (1 × 10^?6 M-1 ×10^?4 M) of the auxins 1-naphthylacetic acid (NAA), 2,4-dichlorophenoxyacetic acid (2,4-D) and mdole-3-acetic acid (IAA) in the culture medium, resulted in a decrease in disease score of the thin cell layer (TCL) explants from soil-grown plants. The cytokinins examined 6-benzyl-aminopurine (BAP) and 6-4-hydroxy-3-methyl-2-enylaminopurine (zeatin), reduced the extent of infection of the TCL explants when used in combination with the auxin NAA. Medium containing NAA at a concentration of 1 × 10^?6 M in combination with BAP at a concentration of 1× 10^?6 or 1 × 10^?4 M allowed differentiation of the disease reactions of the resistant and susceptible cultivars, when the explants were incubated for 10 days at 20 °C after inoculation. Similar conditions of incubation and the addition of NAA (1 × 10^?6 M) combined with BAP (1 × 10^?6 M) to the medium also allowed the differentiation of the disease reactions on TCL explants from stems of in vitro shoot cultures of the cultivars Mikado and Lesira. Increasing concentrations of the auxin NAA and the cytokinin BAP resulted in a reduction in the mean disease score of the callus tissue produced on TCL explants from soil-grown plants, and NAA (1 × 10^?5 M) combined with BAP (1 × 10^?6 or 1 × 10^?5 M) allowed differentiation of resistance and susceptibility in callus tissues when incubated for 5 days at 20 °C. 2,4-D did not allow differentiation of the cultivars. This was in contrast to the inoculation of callus tissue attached to TCL explants of in vitro shoot cultures, where combinations of 2,4-D and BAP at concentrations of 1 × 10^?6 M allowed differentiation of the resistant and susceptible cultivars. These findings provide a basis for designing selection protocols of value in both traditional as well as in vitro breeding programmes to select lines of oilseed rape with resistance/novel resistance to L. maculans.     

Growth kinetics of top and bottom cultures of Saccharomyces spp. in a chemostat using sugarbeet molasses

Growth kinetics were evaluated for three yeast strains of the genus Saccharomyces. Two topfloating strains, SF 115 and SF 116 and one flocculant yeast SF 104 were analyzed in pure and mixed cultures in 1-liter continuous fermentation experiments in a chemostat. Growth was monitored for 72 h at 30°C in a medium containing sugarbeet molasses and 1.0 g/liter each of NH₄H₂PO₄ and urea. SF 115 and SF 116 were found to have lower μ_max values of 0.290 and 0.296 h^?1, respectively, than SF 104, which had a μ_max of 0.364 h^?1. The two top-floating yeasts (SF 115 and SF 116) demonstrated greater affinity for the substrate and utilized substrates at a greater rate. They have K₈ values of 4.03 × 10^?3 M and 3.798 × 10^?3 M, respectively, compared to 9.06 × 10^?3 M for SF 104. A mixed culture of SF 116 and SF and SF 104 was found to have a μ_max of 0.426 h^?1 with a K_s of 6.924 × 10^?3 M. SF 115 grown in mixed culture with SF 104 exhibited a μ_max of 0.473 h^?1 with a K_s of 7.975 × 10^?3 M. In both cases, the SF 104 was the dominant microbe in mixed culture systems.     

Inhibition of the neutrophil oxidative response to a chemotactic peptide by inhibitors of arachidonic acid oxygenation

N-formylmethionylphenylalanine stimulates a short burst of antimycin A-insensitive O₂ uptake, O₂^? production and hexosemonophosphate shunt oxidation of glucose by guinea pig peritoneal neutrophils. The stimulated oxidative metabolism, as well as release of lysosomal enzymes ± cytochalasin B, are inhibited by 5,8,11,14-eicosatetraynoic acid (ID₅₀ 1.5 × 10^?5 M). High concentrations of indomethacin inhibit the peptide-stimulated oxidations (ID₅₀ 1.6 × 10^?4 M) while acetylsalicylic acid (2.5 × 10^?3 M) does not. Digitonin-stimulated oxidative metabolism and enzyme release are not inhibited by 5,8,11,14-eicosatetraynoic acid or indomethacin at concentrations that depress effects of the N-formylated peptide.     

Partial beta-adrenergic receptor blockade in experimental bronchial asthma

The dose-response curves of Terbutaline on isolated tracheae of actively sensitized guinea pigs was significantly (p < 0,001) shifted to the right in comparison with control tracheae (ED 50 11,8 × 10^?8 M resp. 5.2 × 10^?8 M). Furthermore, these isolated, sensitized organs dilated significantly (p < 0.0005) slower than did controls (0.186 ± 0.072 resp. 0.350 ± 0.121 cm H₂O/sec), whereas the dilation velocity after addition of theophylline did not differ. Finally, the stimulation with Fenoterol led to significantly (p < 0.0005) lower amounts of cAMP in sensitized than in control tracheae (24.3 ± 5.3 resp. 33.2 ± 7.5 pmole/mg prot.). The Km₁ and Km₂ of cAMP-phosphodiesterases of tracheal homogenates did not differ in both groups. These results indicate, that sensitization led to a partial blockade of the β-adrenergic-receptor-adenylatecyclase-system.     

Pathways of Chlorophenol Formation in Oxidative Biodegradation of BHC

Hexose 1-phosphate uridylyltransferase (EC 2.7.7.12) was present constitutively in Bifidobacterium bifidum. The enzyme was purified to a homogeneous state from B. bifidum grown on a glucose medium and characterized. The molecular weight of the enzyme is about 110,000.The pH optimum of the enzyme was 7.5. The enzyme was very labile on the acidic side below pH 4.5. Thymidine diphosphate glucose could serve as a substrate with about 60% efficiency of UDP-glucose. The Km values for UDP-gtucose, galactose 1-phosphate (Gal-l-P), UDP-galactose and glucose 1-phosphate (Glc-1-P) were estimated to be 2.3×10^?5M, 5.0 × 10^?4M, 3.1 × 10^?5 M and 1.4 × 10^?4M, respectively. From these results the physiological roles of the enzyme were considered in relation to galactose metabolism in B. bifidum.     

IgE-mediated 14C-serotonin release from rat mast cells modulated by morphine and endorphins

The formaldehyde method was used to examine the interaction of PGE₁ with morphine, β-endorphin and Met-enkephalin on rat mast cells by their effects on IgE-mediated ¹⁴C-serotonin release. PGE₁ (2×10^?8?2×10^?5 M) caused a dose-related inhibition of the mediator release 1 min after an antigen challenge, and morphine (3×10^?7?3×10^?5 M) reversed this PGE₁ effect dose-dependently and stereospecifically; naloxone (2×10^?4 M) antagonized this action of morphine. β-Endorphin (3×10^?7?10^?5 M) and Met-enkephalin (3×10^?6?10^?4 M) mimicked this morphine action dose-dependently and were antagonized by naloxone (2×10^?4 M). These results suggest that morphine and endorphins modulate immunological mediator release from rat mast cells through opioid receptors.     

Revealing binding interaction between seven drugs and immobilized β2‐adrenoceptor by high‐performance affinity chromatography using frontal analysis

The development of new approaches to study the affinity between ligands and G‐protein‐coupled receptors proves to be of growing interest for pharmacologists, chemists, and biologists. The aim of this work was to determine the binding of seven drugs to β₂‐adrenoceptors by frontal analysis using immobilized receptor stationary phase. The dissociation constants (K_d) were determined to be (3.16 ± 0.09) × 10^?4 M for salbutamol, (4.29 ± 0.12) × 10^?4 M for terbutaline, (6.19 ± 0.16) × 10^?4 M for methoxyphenamine, (2.11 ± 0.07) × 10^?4 M for tulobuterol, (1.82 ± 0.11) × 10^?4 M for fenoterol, (9.75 ± 0.24) × 10^?6 M formoterol, and (9.84 ± 0.26) × 10^?5 M for clenbuterol. These results showed a good correlation with the data determined by radioligand binding assay. Further investigations revealed that the dissociation constant mainly attributed to the number of hydrogen bonds in the structures of ligands. This study indicates that affinity chromatography using immobilized receptor stationary phase can be used for the direct determination of drug‐receptor binding interactions and has the potential to become a reliable alternative for quantitative studies of ligand–receptor interactions. Copyright © 2013 John Wiley & Sons, Ltd.     

Exploring the electrochemiluminescent behavior of procaterol hydrochloride in the presence of Ru(bpy)32+ and its analytical application in pharmaceutical preparation

Based on the strong enhancement effect of procaterol hydrochloride on the electrochemiluminescence (ECL) of Ru(bpy)₃²⁺ (bpy = 2,2′‐bipyridine) in an alkaline H₃PO₄–NaOH buffer solution on a bare Pt electrode, a simple, rapid and sensitive method was developed for the determination of procaterol hydrochloride. The optimum conditions for the enhanced ECL have been developed in detail in this work. Under optimum conditions, the logarithmic ECL enhancement vs. the logarithmic concentration of procaterol hydrochloride is linear over a wide concentration range of 2.0 × 10^?7 to 2.0 × 10^?4 M (r =  0.9976), with a limit of detection of 1.1 × 10^?8 M (S/N =  3), and a relative standard deviation of 2.1% (n =  7, c =  5.0 × 10^?6 M). The proposed method was applied to the determination of this drug in tablets with recoveries of 89.7%–98.5%. In addition, a possible mechanism for the enhanced ECL of Ru(bpy)₃²⁺, which is caused by ProH, has also been proposed.     

Enzymatic synthesis of new aromatic and aliphatic esters of flavonoids using Candida antarctica lipase as biocatalyst

Enzymatic acylation of rutin and esculin with aromatic, aliphatic and aryl-aliphatic acids using Candida antarctica lipase in tert amyl alcohol as solvent was investigated under low water content. Whatever the acyl donor used, the conversion yields and initial rates for esculin were higher than for rutin. For a given flavonoid, the performance of these reactions depended on the acyl donor structures. For aliphatic acids, conversion yields and initial rates of both flavonoids were respectively in the ranges of 68–90% and of 9.5×10^?2–72×10^?2 mmol l^?1 h^?1. For aromatic acids, the reaction occurred only with the aryl subgroup (cinnamic, hydrocinnamic, 3,4-dihydroxyhydrocinnamic and 4-hydroxyphenyl acetic acids) and was drastically influenced by the presence of side chain and substitution patterns of the aromatic ring. Except for hydrocinnamic acid (75%, 23.4×10^?2 mmol l^?1 h^?1), with these acids the conversion yields and initial rates were lower and in the range of 10–45% and of 0.7×10^?2 to 12.1×10^?2 mmol l^?1 h^?1. Unsaturation of the side chain of the hydrocinnamic acid decreased the esculin conversion rate from 75 to 13% and initial rate from 23.4 to 1.76×10^?2 mmol l^?1 h^?1. The presence of hydroxyl or nitro-groups on the aromatic ring of the aryl aliphatic acid also reduced conversion yields and initial rates. Even without a spacer, the non-phenolic ring acid (quinic acid) was reactive and lead to conversion yields of about 20 and 23% respectively for rutin and esculin.     

Synthesis,characterization, DNA interaction,and cytotoxicity of novel Pd(II) and Pt(II) complexes

Four complexes [Pd(L)(bipy)Cl]·4H₂O (1), [Pd(L)(phen)Cl]·4H₂O (2), [Pt(L)(bipy)Cl]·4H₂O (3), and [Pt(L)(phen)Cl]·4H₂O (4), where L = quinolinic acid, bipy = 2,2’-bipyridyl, and phen = 1,10-phenanthroline, have been synthesized and characterized using IR, ¹H NMR, elemental analysis, and single-crystal X-ray diffractometry. The binding of the complexes to FS-DNA was investigated by electronic absorption titration and fluorescence spectroscopy. The results indicate that the complexes bind to FS-DNA in an intercalative mode and the intrinsic binding constants K of the title complexes with FS-DNA are about 3.5?×?10⁴ M^?1, 3.9?×?10⁴ M^?1, 6.1?×?10⁴ M^?1, and 1.4?×?10⁵ M^?1, respectively. Also, the four complexes bind to DNA with different binding affinities, in descending order: complex 4, complex 3, complex 2, complex 1. Gel electrophoresis assay demonstrated the ability of the Pt(II) complexes to cleave pBR322 plasmid DNA.