The effect of 5-hydroxytryptamine and other indole derivatives on the formation of adenosine 3',5'-cyclic monophosphate in pigeon erythrocytes.

1. The effect of insulin, acetylcholine, histamine, 5-hydroxytryptamine and prostaglandins E1, E2 and F2alpha on basal and adrenalin-stimulated cyclic AMP content in intact pigeon erythrocytes was investigated. 2. None of these compounds influenced basal cyclic AMP contest, and only 5-hydroxytryptamine antagonized the effect of adrenalin. The increase in cyclic AMP with 0.55 micronM adrenalin was inhibited by approx. 60% in the presence of 10 muM 5-hydroxytryptamine. The interaction between adrenalin and 5-hydroxytryptamine was competitive. 3. 5-Hydroxytryptamine did not affect the rate of degradation of cyclic AMP in intact cells, but did inhibit adrenalin-stimulated cyclic AMP formation in permeable or resealed cell "ghosts". 4. The effect of 5-hydroxytryptamine to inhibit cyclic AMP accumulation was not dependent on the presence of Ca2+, in either intact cells or "ghosts". 5. Various indole derivatives and other compounds were tested for their ability to inhibit the effect of adrenalin on cyclic AMP accumulation. Only those derivatives with a free amino group and net positive charge in the side chain were effective. 6. It was concluded that 5-hydroxytryptamine inhibits adrenalin-stimulated adenylate cyclase activity in pigeon erythrocytes, possibly by competing with adrenalin for binding to the beta-adrenergic receptor.     

On the metal-ion coordinating properties of the 5'-monophosphates of 1, N6-ethenoadenosine (epsilon-AMP), adenosine and uridine. Comparison of the macrochelate formation in the complexes of epsilon-AMP, AMP, ADP and ATP

The concentration dependence of the chemical shifts of the protons H-2, H-8, H-10, H-11, and H-1' of 1,N6-ethenoadenosine 5'-monophosphate (epsilon-AMP2-) has been measured. The results are consistent with the isodesmic model of indefinite noncooperative stacking; the association constant, K = 2.5 +/- 0.3 M-1, is within experimental error identical to the value determined earlier for AMP2-,K = 2.1 +/- 0.4 M-1. The conditions for the potentiometric pH titrations, used to determine the acidity constants of H2(epsilon-AMP), H2(AMP), and H(UMP)- and the stability constants of the metal ion (M2+) complexes of the corresponding nucleoside 5'-monophosphates (NMP), were chosen so that the ligands were present in the monomeric form. The stabilities of Mg(epsilon-AMP) and Mg(AMP) are similar; however, the stabilities of the Mn2+, Cu2+ and Zn2+ complexes of epsilon-AMP2- are much larger (in the case of Cu2+ by a factor of 700) than those of AMP2-. This is due to the much larger metal ion affinity of the epsilon-adenosine moiety compared to that of the parent adenosine residue. As the uridine moiety does not participate in complex formation, the stability constants of M(UMP) have been used to evaluate the extent of macrochelation (i.e. the simultaneous coordination of M2+ to the base moiety and the phosphate group) in the epsilon-AMP and AMP complexes: the concentration of the macrochelated isomer is considerably larger for M(epsilon-AMP) than for M(AMP). A comparison with previous results for the complexes with ADP3- and ATP4- indicates the order, M(AMP)cl less than M(ADP)-cl greater than M(ATP)2-cl for the tendency to form macrochelates (cl). Due to the relatively high affinity of the epsilon-adenosine moiety towards Mn2+, Cu2+ and Zn2+, the phosphate-monoprotonated complexes M(H . epsilon-AMP)+ also become important; the corresponding complexes play only a minor role in the M2+/AMP systems. Intramolecular aromatic-ring stacking occurs in the ternary Cu(2,2'-bipyridyl)(NMP) complexes: about 80% of Cu(Bpy)(AMP) and Cu(Bpy)(epsilon-AMP) exist as the stacked isomer in aqueous solution; for the former system it has been shown in a previous X-ray study that the intramolecular ligand-ligand interaction occurs also in the solid state [Aoki, K. (1978) J. Am. Chem. Soc. 100, 7106]. Overall, the results emphasize that great care should be exercised in drawing conclusions based on studies of metal-ion-containing enzymic systems in which the natural adenine nucleotide cofactors have been replaced by the corresponding 1,N6-etheno derivatives.     

Synthesis of decadeoxyribonucleotides containing N6-methyladenine, N4-methylcytosine, and 5-methylcytosine: recognition and cleavage by restriction endonucleases (nucleosides and nucleotides part 74).

The naturally-occurring modified bases, N6-methyladenine, N4-methylcytosine, and 5-methylcytosine were chemically introduced in place of the adenine or cytosine in the decadeoxyribonucleotides containing recognition sequences of Bgl II, Sau 3AI, Mbo I and Mfl I. The modified oligomers bind to the enzymes but the rates of cleavage by the enzymes are variable.     

Ternary complexes between adenosine 5′-triphosphoric acid, 2, 2′-bipyridyl and the divalent metal ions manganese(II), cobalt(II), copper(II), and zinc(II). Preparation and physicochemical properties

A series of ternary complexes between adenosine 5′-triphosphoric acid (ATP), 2, 2′-bipyridyl, and the transition metal ions manganese(II), cobalt(II), copper(II), and zinc(II) in the ratio 1:1:1 have been prepared. The solid compounds are crystalline and can be formulated as [M(II)-H₂ATP-2, 2′-Bipyridyl]₂·4H₂O (MATPbipy).X-ray powder patterns show them to be all isomorphous. Potentiometric titrations in aqueous solutions are in agreement with the presence of two ionizable protons. Ultraviolet and visible spectra, epr, and magnetic susceptibility measurements suggest that the metal ions have a high-spin distorted octahedral coordination. From infrared spectra it can be deduced that ATP coordinates to the metal only through the oxygen atoms of the phosphate groups.These compounds, which are particularly stable towards hydrolysis, form possible models for ATP transport in biological fluids.     

Anion directed template synthesis of Cu(II) complexes of a N,N,O donor mono-condensed Schiff base ligand: A molecular scaffold forming highly ordered H-bonded rectangular grids

Anion directed, template syntheses of two dinuclear copper(II) complexes of mono-condensed Schiff base ligand Hdipn (4-[(3-aminopentylimino)-methyl]-benzene-1,3-diol) involving 2,4-dihydroxybenzaldehyde and 1,3-diaminopentane were realized in the presence of bridging azide and acetate anions. Both complexes, [Cu₂(dipn)₂(N₃)₂] (1) and [Cu₂(dipn)₂(OAc)₂] (2) have been characterized by X-ray crystallography. The two mononuclear units are joined together by basal-apical, double end-on azido bridges in complex 1 and by basal-apical, double mono-atomic acetate oxygen-bridges in 2. Both complexes form rectangular grid-like supramolecular structures via H-bonds connecting the azide or acetate anion and the p-hydroxy group of 2,4-dihydroxybenzaldehyde. Variable-temperature (300-2 K) magnetic susceptibility measurements reveal that complex 1 has antiferromagnetic coupling (J = −2.10 cm⁻¹) through the azide bridge while 2 has intra-dimer ferromagnetic coupling through the acetate bridge and inter-dimer antiferromagnetic coupling through H-bonds (J = 2.85 cm⁻¹, J′ = −1.08 cm⁻¹).     

Enzymatic repair of 5-formyluracil. II. Mismatch formation between 5-formyluracil and guanine during dna replication and its recognition by two proteins involved in base excision repair (AlkA) and mismatch repair (MutS).

5-Formyluracil (fU), a major methyl oxidation product of thymine, forms correct (fU:A) and incorrect (fU:G) base pairs during DNA replication. In the accompanying paper (Masaoka, A., Terato, H., Kobayashi, M., Honsho, A., Ohyama, Y., and Ide, H. (1999) J. Biol. Chem. 274, 25136-25143), it has been shown that fU correctly paired with A is recognized by AlkA protein (Escherichia coli 3-methyladenine DNA glycosylase II). In the present work, mispairing frequency of fU with G and cellular repair protein that specifically recognized fU:G mispairs were studied using defined oligonucleotide substrates. Mispairing frequency of fU was determined by incorporation of 2'-deoxyribonucleoside 5'-triphosphate of fU opposite template G using DNA polymerase I Klenow fragment deficient in 3'-5' exonuclease. Mispairing frequency of fU was dependent on the nearest neighbor base pair in the primer terminus and 2-12 times higher than that of thymine at pH 7.8 and 2.6-6.7 times higher at pH 9.0 with an exception of the nearest neighbor T(template):A(primer). AlkA catalyzed the excision of fU placed opposite G, as well as A, and the excision efficiencies of fU for fU:G and fU:A pairs were comparable. In addition, MutS protein involved in methyl-directed mismatch repair also recognized fU:G mispairs and bound them with an efficiency comparable to T:G mispairs, but it did not recognize fU:A pairs. Prior complex formation between MutS and a heteroduplex containing an fU:G mispair inhibited the activity of AlkA to fU. These results suggest that fU present in DNA can be restored by two independent repair pathways, i.e. the base excision repair pathway initiated by AlkA and the methyl-directed mismatch repair pathway initiated by MutS. Biological relevance of the present results is discussed in light of DNA replication and repair in cells.     

Pd(II) complexes containing N-alkyl-3-pyridine-5-trifluoromethyl pyrazole ligands: Synthesis, NMR studies and X-ray crystal structures

Palladium [PdCl₂(L)] complexes with N-alkylpyridylpyrazole derived ligands [2-(5-trifluoromethyl-1H-pyrazol-3-yl)pyridine (L¹), 2-(1-ethyl-5-trifluoromethyl-1H-pyrazol-3-yl)pyridine (L²), 2-(1-octyl-5-trifluoromethyl-1H-pyrazol-3-yl)pyridine (L³), and 2-(3-pyridin-2-yl-5-trifluoromethyl-pyrazol-1-yl)ethanol (L⁴) were synthesised. The crystal and molecular structures of [PdCl₂(L)] (L = L², L³, L⁴) were resolved by X-ray diffraction, and consist of monomeric cis-[PdCl₂(L)] molecules. The palladium centre has a typical square-planar geometry, with a slight tetrahedral distortion. The tetra-coordinate metal atom is bonded to one pyridinic nitrogen, one pyrazolic nitrogen and two chlorine ligands in cis disposition. Reaction of L (L², L⁴) with [Pd(CH₃CN)₄](BF₄)₂, in the ratio 1M:2L, gave complexes [Pd(L)]₂(BF₄)₂. Treatment of [PdCl₂(L)] (L = L², L⁴) with NaBF₄ and pyridine (py) and treatment of the same complexes with AgBF₄ and triphenylphosphine (PPh₃) yielded [Pd(L)(py)₂](BF₄)₂ and [Pd(L)(PPh₃)₂](BF₄)₂ complexes, respectively. Finally, reaction of [PdCl₂(L⁴)] with 1 equiv of AgBF₄ yields [PdCl(L⁴)](BF₄).     

Spectroscopic,structural and antibacterial properties of copper(II) complexes with bio-relevant 5-methyl-3-formylpyrazole N(4)-benzyl-N(4)-methylthiosemicarbazone

The coordination behaviour of the title ligand, 5-methyl-3-formylpyrazole N(4)-benzyl-N(4)-methylthiosemicarbazone(HMPz4BM), is reported with solid state isolation of copper(II) complexes, [Cu(HMPz4BM)X₂] (X = Cl, Br, NO₃, ClO₄ and BF₄) which have been spectroscopically and structurally characterised. I.r. data for the free ligand and its Cu(II) complexes indicate that HMPz4BM exhibits a neutral NNS tridentate function via the pyrazolyl nitrogen(tertiary), azomethine nitrogen and thione sulphur. Electronic spectral data are suggestive of a square pyramidal environment for the seemingly pentacoordinated Cu(II) species. E.s.r parameters (RT and LNT) of the reported copper(II) complexes are indicative of a dx_x2–y2 ground state for the reported species. Cyclic voltammograms of Cu(II) complexes show a quasireversible Cu^II/Cu^III couple and also an irreversible Cu^II/Cu^I couple. X-ray crystallography of a representative species, [Cu(HMPz4BM)(NO₃)₂] (C2/c, monoclinic ), has unambiguously documented the conjectural findings from i.r. data that coordinating sites of the title ligand are pyrazolyl (tertiary)nitrogen, azomethine nitrogen and the thione sulphur (NNS); and the oxygen of one of the nitrate ions has occupied the basal plane; the fifth coordination position has been occupied by the oxygen of another nitrate ion in a square pyramidal geometry. The antibacterial properties of the ligand and its copper(II) complexes studied on microorganism, Staphylococcus aureus have pointed out that most of the complexes have higher activities than that of the free ligand.     

Structure of guanylyl-3',5'-cytidine monophosphate. II. Description of the molecular and crystal structure of the calcium derivative in space group P2(1).

The structural features of calcium guanosine-3′,5′-cytidine monophosphate (GpC) have been elucidated by X-ray diffraction analysis. The molecule was crystallized in space group P2₁ with cell constants of a = 21.224 Å, b = 34.207 Å, c = 9.327 Å, and β = 90.527°, Z = 8. The hydration of the crystal is 21% by weight with 72 water molecules in the unit cell. The four GpC molecules in the asymmetric unit occur as two Watson-Crick hydrogen-bonded dimers related by a pseudo-C face centering. Each dimer consists of two independent GpC molecules whose bases are hydrogen bonded to each other in the traditional Watson-Crick fashion. Each dimer possesses a pseudo twofold axis broken by a calcium ion and associated solvent. The four molecules are conformationally similar to helical RNA, but are not identical to it or to each other. Instead, values of conformational angles reflect the intrinsic flexibility of the molecule within the range of basic helical conformations. All eight bases are anti, sugars are all C3′-endo, and the C4′-C5′ bond rotations are gauche-gauche. The R factor is 12.6% for 2918 observed reflections at 1.2-Å resolution.     

Minor-groove-modified oligonucleotides: synthesis of decadeoxynucleotides containing hypoxanthine, N2-methylguanine and 3-deazaadenine, and their interactions with restriction endonucleases Bgl II, Sau, 3AI, and Mbo I (Nucleosides and Nucleotides Part 75).

Decadeoxynucleotides containing hypoxanthine, N2-methylguanine, 3-deazaadenine in the recognition sequences of restriction endonucleases Bgl II, Sau 3AI, and Mbo I were synthesized. These decanucleotides modified in the base moieties facing in to the minor groove were strongly resistant to hydrolysis by Bgl II and partially resistant to that of Sau 3AI and Mbo I. The decadeoxynucleotide containing 3-deazaadenine in place of adenine was bound to Bgl II strongly, whereas the nucleotides containing hypoxanthine and N2-methylguanine were bound less tightly.     

Ternary complexes metal [Co(II), Ni(II), Cu(II) and Zn(II)]--ortho-iodohippurate (I-hip)--acyclovir. X-ray characterization of isostructural [(Co, Ni or Zn)(I-hip)(2)(ACV)(H(2)O)(3)] with stacking as a recognition factor

Four ternary metal--ortho-iodohippurate (I-hip)--acyclovir (ACV) complexes, [M(I-hip)(2)(ACV)(H(2)O)(3)] where M is Co(II) (1), Ni(II) (2), Cu (3) and Zn(II) have been obtained by reaction between the corresponding binary complexes M(II)(I-hip)(2)xnH(2)O and ACV. Three ternary complexes (M=Co, Ni and Zn) and the corresponding Zn(II)--ortho-iodohippurate binary derivative have been structurally characterized by X-ray diffraction: The studies show these three ternary complexes are isostructural and present, in solid state, an interesting stacking between the nucleobase and the aryl ring of the hippurate moiety, which probably promotes the formation of ternary complexes. Moreover, the two different ligands interact between them by means of ancillary hydrogen bonds with water molecules coordinated to the metal ion. It must be mentioned that these two recognition factors, hydrogen bonds plus stacking, could explain the reason for the isostructurality of these ternary derivatives with so different three metal ions, with diverses trends in coordination numbers and geometries. In solid state, there are two enantiomeric molecules that are related by an inversion center as the crystal-building unit (as a translational motif) for the ternary complexes.