15N-CIDNP investigations during tryptophan, N-acetyl-L-tryptophan, and melatonin nitration with reactive nitrogen species

Tryptophan and melatonin are nitrated by peroxynitrite; tryptophan residues in proteins are susceptible to attack by reactive nitrogen species. Nitrated tryptophan might therefore be used as a biomarker for the involvement of reactive species derived from nitrogen oxide in a variety of pathophysiological conditions. The radical character of the tryptophan (Trp) and N-acetyl-L-tryptophan (N-AcTrp) nitration with peroxynitrite is shown using (15)N-CIDNP. During the decay of peroxynitrite-(15)N in the presence of Trp at pH 5 in the probe of a (15)N-NMR spectrometer, the (15)N-NMR signals of various nitrated tryptophans ((15)NO(2)-Trp) show emission (E). The effects are built up in radical pairs [Trp( radical), 15NO2 ](F) formed by diffusive encounters of radicals 15NO2 and Trp( radical) generated during decay of peroxynitrite-(15)N in the presence of Trp. Similar (15)N-CIDNP effects are observed during reaction of Trp and/or N-AcTrp using the nitrating systems H(15)NO(3), H(15)NO(4) and H(2)O(2)/15NO2 /HRP, which are also built up in radical pairs [Trp, 15NO2 ](F). During nitration of melatonin (Mel) with peroxynitrite-(15)N and H(15)NO(4), the (15)N-NMR signal of 4-nitromelatonin (4-(15)NO(2)-Mel) shows emission arising from radical pairs [Mel, 15NO2 ](F) which are formed in an analogous manner.     

8-Nitro-2'-deoxyguanosine, a specific marker of oxidation by reactive nitrogen species, is generated by the myeloperoxidase-hydrogen peroxide-nitrite system of activated human phagocytes

Reactive intermediates generated by phagocytes damage DNA and may contribute to the link between chronic inflammation and cancer. Myeloperoxidase, a heme protein secreted by activated phagocytes, is a potential catalyst for such reactions. Recent studies demonstrate that this enzyme uses hydrogen peroxide (H2O2) and nitrite (NO2-) to generate reactive nitrogen species which convert tyrosine to 3-nitrotyrosine. We now report that activated human neutrophils use myeloperoxidase, H2O2, and NO2- to nitrate 2'-deoxyguanosine, one of the nucleosides of DNA. Through HPLC, UV/vis spectroscopy, and mass spectrometry, the two major products of this reaction were identified as 8-nitroguanine and 8-nitro-2'-deoxyguanosine. Nitration required each component of the complete enzymatic system and was inhibited by catalase and heme poisons. However, it was independent of chloride ion and little affected by scavengers of hypochlorous acid, suggesting that the reactive agent is a nitrogen dioxide-like species that results from the one-electron oxidation of NO2- by myeloperoxidase. Alternatively, 2'-deoxyguanosine might be oxidized directly by the enzyme to yield a radical species which subsequently reacts with NO2- or NO2* to generate the observed products. Human neutrophils stimulated with phorbol ester also generated 8-nitroguanine and 8-nitro-2'-deoxyguanosine. The reaction required NO2- and was inhibited by catalase and heme poisons, implicating myeloperoxidase in the cell-mediated pathway. These results indicate that human neutrophils use the myeloperoxidase-H2O2-NO2- system to generate reactive species that can nitrate the C-8 position of 2'-deoxyguanosine. Our observations raise the possibility that reactive nitrogen species generated by myeloperoxidase and other peroxidases contribute to nucleobase oxidation and tissue injury at sites of inflammation.     

Unique oxidative mechanisms for the reactive nitrogen oxide species, nitroxyl anion

The nitroxyl anion (NO-) is a highly reactive molecule that may be involved in pathophysiological actions associated with increased formation of reactive nitrogen oxide species. Angeli's salt (Na2N2O3; AS) is a NO- donor that has been shown to exert marked cytotoxicity. However, its decomposition intermediates have not been well characterized. In this study, the chemical reactivity of AS was examined and compared with that of peroxynitrite (ONOO-) and NO/N2O3. Under aerobic conditions, AS and ONOO- exhibited similar and considerably higher affinities for dihydrorhodamine (DHR) than NO/N2O3. Quenching of DHR oxidation by azide and nitrosation of diaminonaphthalene were exclusively observed with NO/N2O3. Additional comparison of ONOO- and AS chemistry demonstrated that ONOO- was a far more potent one-electron oxidant and nitrating agent of hydroxyphenylacetic acid than was AS. However, AS was more effective at hydroxylating benzoic acid than was ONOO-. Taken together, these data indicate that neither NO/N2O3 nor ONOO- is an intermediate of AS decomposition. Evaluation of the stoichiometry of AS decomposition and O2 consumption revealed a 1:1 molar ratio. Indeed, oxidation of DHR mediated by AS proved to be oxygen-dependent. Analysis of the end products of AS decomposition demonstrated formation of NO2- and NO3- in approximately stoichiometric ratios. Several mechanisms are proposed for O2 adduct formation followed by decomposition to NO3- or by oxidation of an HN2O3- molecule to form NO2-. Given that the cytotoxicity of AS is far greater than that of either NO/N2O3 or NO + O2, this study provides important new insights into the implications of the potential endogenous formation of NO- under inflammatory conditions in vivo.     

The [Ru(Hedta)NO](0.1-) system: structure, chemical reactivity and biological assays

The [Ru(II)(Hedta)NO(+)] complex is a diamagnetic species crystallizing in a distorted octahedral geometry, with the Ru-N(O) length 1.756(4) A and the RuNO angle 172.3(4) degrees . The complex contains one protonated carboxylate (pK(a)=2.7+/-0.1). The [Ru(II)(Hedta)NO(+)] complex undergoes a nitrosyl-centered one-electron reduction (chemical or electrochemical), with E(NO+/NO)=-0.31 V vs SCE (I=0.2 M, pH 1), yielding [Ru(II)(Hedta)NO](-), which aquates slowly: k(-NO)=2.1+/-0.4x10(-3) s(-1) (pH 1.0, I=0.2 M, CF(3)COOH/NaCF(3)COO, 25 degrees C). At pHs>12, the predominant species, [Ru(II)(edta)NO](-), reacts according to [Ru(II)(edta)NO](-)+2OH(-)-->[Ru(II)(edta)NO(2)](3-), with K(eq)=1.0+/-0.4 x 10(3) M(-2) (I=1.0 M, NaCl; T=25.0+/-0.1 degrees C). The rate-law is first order in each of the reactants for most reaction conditions, with k(OH(-))=4.35+/-0.02 M(-1)s(-1) (25.0 degrees C), assignable mechanistically to the elementary step comprising the attack of one OH(-) on [Ru(II)(edta)NO](-), with subsequent fast deprotonation of the [Ru(II)(edta)NO(2)H](2-) intermediate. The activation parameters were DeltaH(#)=60+/-1 kJ/mol, DeltaS(#)=-31+/-3 J/Kmol, consistent with a nucleophilic addition process between likely charged ions. In the toxicity up-and-down tests performed with Swiss mice, no death was observed in all the doses administered (3-9.08 x 10(-5) mol/kg). The biodistribution tests performed with Wistar male rats showed metal in the liver, kidney, urine and plasma. Eight hours after the injection no metal was detected in the samples. The vasodilator effect of [Ru(II)(edta)NO](-) was studied in aortic rings without endothelium, and was compared with sodium nitroprusside (SNP). The times of maximal effects of [Ru(II)(edta)NO](-) and SNP were 2 h and 12 min, respectively, suggesting that [Ru(II)(edta)NO](-) releases NO slowly to the medium in comparison with SNP.     

The generation of free radicals by nitric oxide synthase

Nitric oxide synthase (NOS) is an example of a family of heme-containing monooxygenases that, under the restricted control of a specific substrate, can generate free radicals. While the generation of nitric oxide (NO*) depends solely on the binding of L-arginine, NOS produces superoxide (O(2)*(-)) and hydrogen peroxide (H(2)O(2)) when the concentration of the substrate is low. Not surprisingly, effort has been put forth to understand the pathway by which NOS generates NO*, O(2)*(-) and H(2)O(2), including the role of substrate binding in determining the pathways by which free radicals are generated. By binding within the distal heme pocket near the sixth coordination position of the NOS heme iron, L-arginine alters the coordination properties of the heme iron that promotes formation of the perferryl complex NOS-[Fe(5+)=O](3+). This reactive iron intermediate has been shown to abstract a hydrogen atom from a carbon alpha to a heteroatom and generate carbon-centered free radicals. The ability of NOS to produce free radicals during enzymic cycling demonstrates that NOS-[Fe(5+)=O](3+) behaves like an analogous iron-oxo complex of cytochrome P-450 during aliphatic hydroxylation. The present review discusses the mechanism(s) by which NOS generates secondary free radicals that may initiate pathological events, along with the cell signaling properties of NO*, O(2)*(-) and H(2)O(2).     

A discussion of the chemistry of oxidative and nitrosative stress in cytotoxicity

Nitric oxide (NO) has been shown to be a key bioregulatory agent in a wide variety of biological processes, yet cytotoxic properties have been reported as well. This dichotomy has raised the question of how this potentially toxic species can be involved in so many fundamental physiological processes. We have investigated the effects of NO on a variety of toxic agents and correlated how its chemistry might pertain to the observed biology. The results generate a scheme termed the chemical biology of NO in which the pertinent reactions can be categorized into direct and indirect effects. The former involves the direct reaction of NO with its biological targets generally at low fluxes of NO. Indirect effects are reactions mediated by reactive nitrogen oxide species, such as those generated from the NO/O2 and NO/O2- reactions, which can lead to cellular damage via nitrosation or oxidation of biological components. This report discusses several examples of cytotoxicity involved with these stresses.     

Structural correlation of catecholase-like activities of oxy-bridged dinuclear copper(II) complexes

Eight oxy-bridged dinuclear copper(II) complexes with catecholase-like sites, [Cu(L1)X]2 (HL1 = 1-diethylaminopropan-2-ol, X=N3- 1, NCO- 2, and NO2- 3), [Cu(L2)X]2 (HL2=N-ethylsalicylaldimine, X=NO3- 4, Cl- 5, N3- 6, NCS- 7), and [Cu(L3)]2(ClO4)2, 8 (HL3=N-(salicylidene)-N'-(2-pyridylaldene)propanediamine) have been prepared and characterized. The single crystal X-ray analysis show that the structures of complexes 6 and 8 are dimeric with two adjacent copper(II) atoms bridged by pairs of micro-oxy atoms from the L2 and L3 ligands. Magnetic susceptibility measurements in the temperature range 4-300 K indicate significant antiferromagnetic coupling for 4, 5 and 7 and ferromagnetic coupling for 6 between the copper(II) atoms. The catecholase activity of complexes for the oxidation of 3,5-di-tert-butylcatechol by O2 was studied and it was found that the complexes with the bond distance of Cu(II)...Cu(II) located at 2.9-3.0 A show higher catecholase activity.     

Chemistry of the diazeniumdiolates. I. Structural and spectral characteristics of the [N(O)NO]- functional group.

Ions of structure X[N(O)NO]-, examples of which have seen increasing use as probes for studying the biology of nitric oxide (NO) over the past decade, have a varied chemical history spanning nearly two centuries. Nevertheless, they have not been widely appreciated for their physicochemical similarities. Here we begin a series of systematic inquiries into the fundamental chemistry of such compounds aimed at identifying both the characteristics that justify considering them as a group and the factors that contribute to observed differences in their physicochemical properties. In the present paper, X-ray structures in which X is SO3- (1), O- (2), Ph (3), and Et2N (5), as well as that of the gem-disubstituted carbon derivative CH2[N(O)NO]2-(2) (4), are compared. All their O-N-N-O systems are essentially planar, with cis oxygens and an N-N linkage exhibiting considerable double-bond character. The ultraviolet spectrum of the isolated chromophore consists of a relatively intense ( approximately 6-10 mM(-1) x cm(-1) per [N(O)NO]- group) absorption at 248-250 nm (for 2 and 5) that is red shifted by through-space Stark interactions (e.g., by approximately 10 nm in 1 and 4) as well as by conjugative interaction with X (lambda(max) = 284 nm for 3). Infrared and Raman spectra for the widely used pharmacological probe 5 were determined, with analysis of vibrational modes being aided by comparison with the spectra of the [15N(O)15NO]- isotopomer and density functional theory calculations at the B3LYP/6-311++G** level. To address confusion that has arisen in the literature resulting from rather widespread use of differing trivial designations for this class of compounds, a unifying nomenclature system is recommended in which compounds containing the [N(O)NO]- moiety are named as diazeniumdiolates. It is hoped that these and other efforts to understand and predict the physicochemical similarities and differences among different members of the diazeniumdiolate class will aid in reaping their full potential in the area of rational drug design.     

Cellular mechanisms underlying nitric oxide-induced vasodilation of descending vasa recta

It has been observed that vasoactivity of explanted descending vasa recta (DVR) is modulated by intrinsic nitric oxide (NO) and superoxide (O(2)(-)) production (Cao C, Edwards A, Sendeski M, Lee-Kwon W, Cui L, Cai CY, Patzak A, Pallone TL. Am J Physiol Renal Physiol 299: F1056-F1064, 2010). To elucidate the cellular mechanisms by which NO, O(2)(-) and hydrogen peroxide (H(2)O(2)) modulate DVR pericyte cytosolic Ca(2+) concentration ([Ca](cyt)) and vasoactivity, we expanded our mathematical model of Ca(2+) signaling in pericytes. We incorporated simulations of the pathways that translate an increase in [Ca](cyt) to the activation of myosin light chain (MLC) kinase and cell contraction, as well as the kinetics of NO and reactive oxygen species formation and their effects on [Ca](cyt) and MLC phosphorylation. The model reproduced experimentally observed trends of DVR vasoactivity that accompany exposure to N(ω)-nitro-L-arginine methyl ester, 8-Br-cGMP, Tempol, and H(2)O(2). Our results suggest that under resting conditions, NO-induced activation of cGMP maintains low levels of [Ca](cyt) and MLC phosphorylation to minimize basal tone. This results from stimulation of Ca(2+) uptake from the cytosol into the SR via SERCA pumps, Ca(2+) efflux into the extracellular space via plasma membrane Ca(2+) pumps, and MLC phosphatase (MLCP) activity. We predict that basal concentrations of O(2)(-) and H(2)O(2) have negligible effects on Ca(2+) signaling and MLC phosphorylation. At concentrations above 1 nM, O(2)(-) is predicted to modulate [Ca(cyt)] and MCLP activity mostly by reducing NO bioavailability. The DVR vasoconstriction that is induced by high concentrations of H(2)O(2) can be explained by H(2)O(2)-mediated downregulation of MLCP and SERCA activity. We conclude that intrinsic generation of NO by the DVR wall may be sufficient to inhibit vasoconstriction by maintaining suppression of MLC phosphorylation.     

Release of NO by a nitrosyl complex upon activation by the mitochondrial reducing power

The reaction of trans-[Ru(NH(3))(4)P(OEt)(3)NO](3+) and mitochondria was investigated through differential pulse polarography and fluorimetry. The nitrosyl complex undergoes one-electron reduction centered on the NO ligand site. The reaction between the mitochondrial reductor and trans-[Ru(NH(3))(4)P(OEt)(3)NO](3+) exhibits a second order specific rate constant calculated as k=2 x 10(1) M(-1) s(-1). The reduced species, trans-[Ru(NH(3))(4)P(OEt)(3)NO](2+), quickly releases NO, yielding trans-[Ru(NH(3))(4)P(OEt)(3)H(2)O](2+). The low toxicities of both trans-[Ru(NH(3))(4)P(OEt)(3)(NO)](2+) and trans-[Ru(NH(3))(4)P(OEt)(3)H(2)O](2+) and its ability to release NO after reductive activation in a biological medium make the nitrosyl compound a useful model of a hypotensive drug.     

Generation of nitric oxide by enzymatic oxidation of N-hydroxy-N-nitrosamines

The nitric oxide (N = O) free radical exhibits potent cytocidal, mutagenic and vasodilatory properties. We have examined the hypothesis that the hydroxynitrosamino functionality (see sequence in text), which occurs naturally in antineoplastic and antihypertensive agents, will directly generate N = O following peroxidatic 1-electron oxidation. Cupferron (see sequence in text) is indeed an excellent (k greater than 10(7) m-1 s-1) substrate for horseradish peroxidase. The products are N = O and nitrosobenzene (phi - N = O) which are generated and consumed as follows. First, cupferron is oxidized by the classical peroxidatic mechanism to form an unstable nitroxide free radical (see sequence in text) which then forms N = O and phi - N = O spontaneously (see sequence in text). The N = O then reacts with phi - N = O to reform cupferron (see sequence in text) or with the enzyme to generate the characteristic peroxidase--N = O chromophore. Simultaneously, in a competitive reaction with O2, the N = O is converted to NO-2 (4N = O + O2 + 2H2O------------4NO-2 + 4H+). The reactivity of hydroxynitrosamino compounds with horseradish peroxidase is in the order cupferron greater than hydroxynitrosaminomethane greater than alanosine. These model reactions, involving direct oxidation of the hydroxynitrosamino moiety, comprise a novel pathway for the biological production of N = O.     

Synthesis and characterization of polypyridineruthenium(II) complexes containing a linear ambidentate ligand, NCO or NCS, and reaction of isocyanato complexes under acidic conditions

Isocyanato and isothiocyanatopolypyridineruthenium complexes, [Ru(NCX)Y(bpy)(py)₂]ⁿ⁺ (bpy=2,2′-bipyridine, PY=pyridine; X=O, Y=NO₂ for n=0, and Y=py for n=1; X=S, Y=NO₂ for n=0, Y=NO for n=2, and Y=py for n=1), were synthesized by the reaction of polypyridineruthenium complexes with potassium cyanate or sodium thiocyanate salt. Isocyanatoruthenium(II) complexes, [Ru(NCO)(NO₂)(bpy)(py)₂] and [Ru(NCO)(bpy)(py)₃]⁺, react under acidic conditions to form the corresponding ammineruthenium complexes, [Ru(NO)(NH₃)(bpy)(py)₂]³⁺. The molecular structures of [Ru(NCO)(bpy)(py)₃]ClO₄, [Ru(NCS)(NO)(bpy)(py)₂](PF₆)₂ and [Ru(NO)(NH₃)(bpy)(py)₂](PF₆)₃ were determined by X-ray crystallography.     

Crystal structure, solid state and solution characterisation of copper(II) coordination compounds of ethyl 5-methyl-4-imidazolecarboxylate (emizco)

The synthesis and characterisation of the following compounds derived from the biological relevant compound ethyl 5-methyl-4-imidazolecarboxylate (emizco) (1): [Cu(emizco)Cl2] (2), [Cu(emizco)2Cl2] (3), [Cu(emizco)2Br2] (4), [Cu(emizco)2(H2O)2](NO3)2 (5) and [Cu(emizco)4](NO3)2 (6), is presented. These compounds were characterised by IR and UV spectroscopic techniques, in addition the crystal structures of compounds 1-5 were determined. For complexes 2-5, emizco is coordinated as a bidentate ligand, through the oxygen atom of the carboxylate moiety and the nitrogen atom of the imidazolic ring. Different geometries are stabilised: compound 2 includes a pentacoordinated square pyramidal metal centre, while 3-5 are derived from octahedral geometry. Halide compounds 3 and 4 show a cis-octahedral arrangement, which is not very common on [CuN2O2X2] systems, while 5 stabilises the trans-octahedral isomer. Compound 6 displays a square planar geometry. Finally, hydrolysis of emizco to its corresponding carboxylic acid (mizco), allowed the preparation of another square planar complex 7, identified as [Cu(mizco)2] 0.5H2O. Solution studies of these compounds indicate that emizco is not substituted from the coordination sphere, remaining as a bidentate ligand. Halides are substituted by water molecules, changing from cis octahedral to the trans-[Cu(emizco)2(H2O)2]2+ isomer.     

A tale of two controversies: defining both the role of peroxidases in nitrotyrosine formation in vivo using eosinophil peroxidase and myeloperoxidase-deficient mice, and the nature of peroxidase-generated reactive nitrogen species

Nitrotyrosine is widely used as a marker of post-translational modification by the nitric oxide ((.)NO, nitrogen monoxide)-derived oxidant peroxynitrite (ONOO(-)). However, since the discovery that myeloperoxidase (MPO) and eosinophil peroxidase (EPO) can generate nitrotyrosine via oxidation of nitrite (NO(2)(-)), several questions have arisen. First, the relative contribution of peroxidases to nitrotyrosine formation in vivo is unknown. Further, although evidence suggests that the one-electron oxidation product, nitrogen dioxide ((*)NO(2)), is the primary species formed, neither a direct demonstration that peroxidases form this gas nor studies designed to test for the possible concomitant formation of the two-electron oxidation product, ONOO(-), have been reported. Using multiple distinct models of acute inflammation with EPO- and MPO-knockout mice, we now demonstrate that leukocyte peroxidases participate in nitrotyrosine formation in vivo. In some models, MPO and EPO played a dominant role, accounting for the majority of nitrotyrosine formed. However, in other leukocyte-rich acute inflammatory models, no contribution for either MPO or EPO to nitrotyrosine formation could be demonstrated. Head-space gas analysis of helium-swept reaction mixtures provides direct evidence that leukocyte peroxidases catalytically generate (*)NO(2) formation using H(2)O(2) and NO(2)(-) as substrates. However, formation of an additional oxidant was suggested since both enzymes promote NO(2)(-)-dependent hydroxylation of targets under acidic conditions, a chemical reactivity shared with ONOO(-) but not (*)NO(2). Collectively, our results demonstrate that: 1) MPO and EPO contribute to tyrosine nitration in vivo; 2) the major reactive nitrogen species formed by leukocyte peroxidase-catalyzed oxidation of NO(2)(-) is the one-electron oxidation product, (*)NO(2); 3) as a minor reaction, peroxidases may also catalyze the two-electron oxidation of NO(2)(-), producing a ONOO(-)-like product. We speculate that the latter reaction generates a labile Fe-ONOO complex, which may be released following protonation under acidic conditions such as might exist at sites of inflammation.     

Biological activity of complexes derived from pyridine-2-carbaldehyde thiosemicarbazone. Structure of

Biological studies on [Fe(L)2](NO3).0.5H2O (1), [Fe(L)2][PF6] (2), [Co(L)2](NCS) (3), [Ni(HL)2]Cl2.3H2O (4) and Cu(L)(NO3) (5), where HL=C7H8N4S, pyridine-2-carbaldehyde thiosemicarbazone, have been carried out. The crystal structure of compound 3 has been solved. It consists of discrete monomeric cationic entities containing cobalt(III) ions in a distorted octahedral environment. The metal ion is bonded to one sulfur and two nitrogen atoms of each thiosemicarbazone molecule. The thiocyanate molecules act as counterions. The copper(II) and iron(III) complexes react with reduced glutathione and 2-mercaptoethanol. The reaction of compound 1 with the above thiols causes the reduction of the metal ion and bis(thiosemicarbazonato)iron(II) species are obtained. The redox activity, and in particular the reaction with cell thiols, seems to be related to the cytotoxicity of these complexes against Friend erithroleukemia cells and melanoma B16F10 cells.     

Preparation of platinum(IV) complexes with dipeptide and diimine. X-ray crystal structure and 195Pt NMR spectra

We prepared platinum(IV) complexes containing dipeptide and diimine or diamine, the [PtCl(dipeptide-N,N,O)(diimine or diamine)]Cl complex, where -N,N,O means dipeptide coordinated as a tridentate chelate, dipeptide=glycylglycine (NH(2)CH(2)CON(-)CH(2)COO(-), digly, where two protons of dipeptide are detached when the dipeptide coordinates to metal ion as a tridentate chelate), glycyl-L-alanine (NH(2)CH(2)CON(-)CHCH(3)COO(-), gly-L-ala), L-alanylglycine (NH(2)CH CH(3)CON(-)CH(2)COO(-), L-alagly), or L-alanyl-L-alanine (NH(2)CHCH(3)CON(-)CHCH(3)COO(-), dil-ala), and diimine or diamine=bipyridine (bpy), ethylenediamine (en), N-methylethylenediamine (N-Me-en), or N,N'-dimethylethylenediamine (N,N'-diMe-en). In the complexes containing gly-L-ala or dil-ala, two separate peaks of the (195)Pt NMR spectra of the [PtCl(dipeptide-N,N,O)(diimine or diamine)]Cl complexes appeared in, but in the complexes containing digly or L-alagly, one peak which contained two overlapped signals appeared. One of the two complexes containing gly-L-ala and bpy, [PtCl(gly-L-ala-N,N,O)(bpy)]NO(3), crystallized and was analyzed. This complex has the monoclinic space group P2(1)2(1)2(1) with unit cell dimensions of a=9.7906(3)A, b=11.1847(2)A, c=16.6796(2)A, Z=4. The crystal data revealed that this [PtCl(gly-L-ala-N,N,O)(bpy)]NO(3) complex has the near- (Cl, CH(3)) configuration of two possible isomers. Based on elemental analysis, the other complex must have the near- (Cl, CH(3))-[PtCl(gly-L-ala-N,N,O)(bpy)]NO(3) configuration. The (195)Pt NMR chemical shifts of the near- (Cl, CH(3))-[PtCl(gly-L-ala-N,N,O)(bpy)]NO(3) complex and the far- (Cl, CH(3))-[PtCl(gly-L-ala-N,N,O)(bpy)]NO(3) complex are 0 ppm and -19 ppm, respectively (0 ppm for the Na(2)[PtCl(6)] signal). The additive property of the (195)Pt NMR chemical shift is discussed. The (195)Pt NMR chemical shifts of [PtCl(dipeptide-N,N,O)(bpy)]Cl appeared at a higher field when the H attached to the dipeptide carbon atom was replaced with a methyl group. On the other hand, the (195)Pt NMR chemicals shifts of [PtCl(dipeptide-N,N,O)(diamine)] appeared at a lower field when the H attached to the diamine nitrogen atom was replaced with a methyl group, in the order of [PtCl(digly-N,N,O)(en)]Cl, [PtCl(digly-N,N,O)(N-Me-en)]Cl, and [PtCl(digly-N,N,O)(N,N'-diMe-en)]Cl.     

Synthesis,characterization and antitumor activity of platinum(II) complexes with diethyl and monoethyl 2-quinolylmethylphosphonates

A series of new platinum(II) complexes with diethyl (2-dqmp) and monoethyl (2-Hmqmp) 2-quinolylmethylphosphonates have been prepared and studied. Both organophosphorus ligands by reaction with [PtX(4)](2-) (X=Cl, Br) form either the molecular or ionic complexes depending on the acidity of the reaction solution. Dihalide adducts, trans-[PtL(2)X(2)] (L=2-dqmp, 2-Hmqmp), with N-bonded ligand through the quinoline nitrogen were obtained in the neutral medium, while under acidic conditions at pH<3 were isolated the ion-pair salt complexes, [LH](2)[PtX(4)], containing the protonated quinoline ligand as cation and tetrahaloplatinate complex as anion. In addition, 2-Hmqmp at pH approximately 3.5 forms quinolinium hexahalodiplatinum salt complexes, [2-H(2)mqmp](2)[Pt(2)X(6)], while the chelate complex, [Pt(2-mqmp)(2)].2H(2)O, with N,O-bonded ligand through the quinoline nitrogen and the deprotonated phosphonic acid oxygen was obtained at pH>6. The new complexes were characterized on the basis of elemental and thermogravimetric analyses, conductometric measurements, and by infrared and (1)H NMR spectral studies. As a preliminary assessment of their biological activity, complexes were evaluated for their in vitro cytostatic activity in an epidermoid human carcinoma (KB) and murine leukemia (L1210) cell lines. The results obtained were compared with those obtained for the corresponding Pd(II) complexes.     

Novel principles in the microbial conversion of nitrogen compounds

Some aspects of inorganic nitrogen conversion by microorganisms like N2O emission and hydroxylamine metabolism studied by Beijerinck and Kluyver, founders of the Delft School of Microbiology, are still actual today. In the Kluyver Laboratory for Biotechnology, microbial conversion of nitrogen compounds is still a central research theme. In recent years a range of new microbial processes and process technological applications have been studied. This paper gives a review of these developments including, aerobic denitrification, anaerobic ammonium oxidation, heterotrophic nitrification, and formation of intermediates (NO2-, NO, N2O), as well as the way these processes are controlled at the genetic and enzyme level.     

Antioxidation and DNA-Binding Properties of Binuclear Lanthanide(III) Complexes with a Schiff Base Ligand Derived from 8-Hydroxyquinoline-7-carboxaldehyde and Benzoylhydrazine

8-Hydroxyquinoline-7-carboxaldehyde (8-HQ-7-CA), Schiff-base ligand 8-hydroxyquinoline-7-carboxaldehyde benzoylhydrazone, and binuclear complexes [LnL(NO(3) )(H(2) O)(2) ](2) were prepared from the ligand and equivalent molar amounts of Ln(NO(3) )?6 H(2) O (Ln=La(3+) , Nd(3+) , Sm(3+) , Eu(3+) , Gd(3+) , Dy(3+) , Ho(3+) , Er(3+) , Yb(3+) , resp.). Ligand acts as dibasic tetradentates, binding to Ln(III) through the phenolate O-atom, N-atom of quinolinato unit, and C?N and ?O?C?N? groups of the benzoylhydrazine side chain. Dimerization of this monomeric unit occurs through the phenolate O-atoms leading to a central four-membered (LnO)(2) ring. Ligand and all of the Ln(III) complexes can strongly bind to CT-DNA through intercalation with the binding constants at 10(5) -10(6) M(-1) . Moreover, ligand and all of the Ln(III) complexes have strong abilities of scavenging effects for hydroxyl (HO(.) ) radicals. Both the antioxidation and DNA-binding properties of Ln(III) complexes are much better than that of ligand.