Mixing ratio-dependent energy transfer from DNA-bound 4',6-diamidino-2-phenylindole to [Ru(1,10-phenanthroline)(2)dipyrido[3,2-a:2',3'-c]phenazine](2+)

The binding mode of Delta- and Lambda-[Ru(1,10-phenanthroline)(2)dipyrido[3,2-a:2',3'-c]phenazine](2+) ([Ru(phen)(2)DPPZ](2+)) to DNA in the presence of 4',6-diamidino-2-phenylindole (DAPI) at a low and high [DAPI]/[DNA base] ratio (0.02 and 0.20, respectively) was investigated using electric absorption and circular dichroism spectroscopy. The spectral properties of both the Delta- and Lambda-[Ru(phen)(2)DPPZ](2+) were not altered in the presence of DAPI disregarding the [DAPI]/[DNA] ratio, suggesting that the presence of DAPI in the minor groove of DNA does not affect the binding mode of the [Ru(phen)(2)DPPZ](2+) complex to DNA. The transferring excited energy of DAPI to both Delta- and Lambda-[Ru(phen)(2)DPPZ](2+) occurs through F?rster type resonance when they both spontaneously bound to DNA. At a high [DAPI]/[DNA] ratios, an upward bending curve in the Stern-Volmer plot, and a shortening the DAPI fluorescence decay time with increasing [Ru(phen)(2)DPPZ](2+) concentration were found. These results indicate that the quenching of the DAPI's fluorescence occurs through both the static and dynamic mechanisms. In contrast, the quenching mechanism at a low [DAPI]/[DNA] ratios was found to be purely static. The static quenching constant decreased linearly with respect to the [DAPI]/[DNA] ratio. Decrease in quenching efficiency can be explained by the association constant of [Ru(phen)(2)DPPZ](2+) to DNA while being within a quenchable distance from a DAPI molecule.     

Vibrational circular dichroism and IR absorption of DNA complexes with Cu2+ ions

Vibrational circular dichroism (VCD) spectroscopy and simultaneous IR absorption measurements are applied to study the interaction of natural calf thymus DNA with Cu2+ ions at room temperature in a Cu2+ concentration range of 0-0.4M (a Cu2+/phosphate molar ratio [Cu]/[P] of 0-0.7). In some important instances, VCD provides more detailed insights than previous IR investigations whereas in several others it leads to the same interpretations. The Cu2+ ions bind to phosphate groups at a low metal concentration. Upon increasing the ion concentration, chelates are formed in which Cu2+ binds to the N7 of guanine (G) and a phosphate group. Detectable only by VCD, significant distortion of most guanine-cytosine (GC) base pairs occurs at a [Cu]/[P] ratio of 0.5 with only a minor affect on adenine-thymine (AT) base pairs, which favors a "sandwich" complex in which a Cu2+ ion is inserted between two adjacent guanines in a GpG sequence. The AT base pairs become significantly distorted when the metal concentration is increased to 0.7 [Cu]/[P]. A number of GC base pairs, which are possibly involved in sandwich complexes, remain stacked and paired even at 0.7 [Cu]/[P], preventing complete strand separation. The DNA secondary structure changes considerably from the standard B-form geometry at a [Cu]/[P] ratio of 0.4 and higher. A further transition to some intermediate conformation that is inconsistent with either the A- or Z-form or a completely denatured state is suggested in agreement with other works. In general, VCD proves to be a reliable indicator of the 3-dimensional structure of the DNA-metal ion complexes, which reveals structural details that cannot be deduced from the IR absorption spectra alone.     

Bacterial DNA supercoiling and [ATP]/[ADP]. Changes associated with a transition to anaerobic growth.

Shifting Escherichia coli from aerobic to anaerobic growth caused changes in the ratio of [ATP]/[ADP] and in negative supercoiling of chromosomal and plasmid DNA. Shortly after lowering oxygen tension, both [ATP]/[ADP] and supercoiling transiently decreased. Under conditions of exponential anaerobic growth, both were higher than under aerobic conditions. These correlations may reflect an effect of [ATP]/[ADP] on DNA gyrase, since in vitro [ATP]/[ADP] influences the level of plasmid supercoiling attained when gyrase is either introducing or removing supercoils. When the supercoiling activity of gyrase was perturbed by a mutation in gyrB, a shift to anaerobic conditions resulted in plasmid supercoil relaxation similar to that seen with wild-type. However, the low level of supercoiling in the mutant persisted during a time when supercoiling in wild-type recovered and then exceeded aerobic levels. Thus, changes in oxygen tension can alter DNA supercoiling through an effect on gyrase, and correlations exist between changes in supercoiling and changes in the intracellular ratio of [ATP]/[ADP].     

Bacterial DNA supercoiling and [ATP]/[ADP] ratio: changes associated with salt shock.

When Escherichia coli K-12 was shifted from a medium lacking salt to one containing 0.5 M NaCl, both the [ATP]/[ADP] ratio and negative supercoiling of plasmid DNA increased within a few minutes. After about 10 min both declined, eventually reaching a level slightly above that observed with cells growing exponentially in the absence of salt. Since in vitro the [ATP]/[ADP] ratio influences the level of supercoiling generated by gyrase (H. Westerhoff, M. O'Dea, A. Maxwell, and M. Gellert, Cell Biophys. 12:157-181, 1988), the physiological response of supercoiling to salt shock is most easily explained by the sensitivity of gyrase to changes in the intracellular [ATP]/[ADP] ratio. This raises the possibility that the [ATP]/[ADP] ratio is an important factor in the control of supercoiling.     

Modulation by citrate of glycolytic oscillations in skeletal muscle extracts.

Oscillatory behavior of glycolysis in cell-free extracts of skeletal muscle involves repeated bursts of phosphofructokinase activity and associated oscillations in the [ATP]/[ADP] ratio. Addition of citrate, a potent physiological inhibitor of phosphofructokinase, decreased the frequency of the oscillations and delayed the first burst of phosphofructokinase activity in a dose-dependent manner. Citrate decreased the trigger point [ATP]/[ADP] ratio at which bursts of phosphofructokinase activity were initiated but had a much smaller effect on the average [ATP]/[ADP] ratio and did not decrease the peak values of the ratio. When oscillations were prevented by addition of fructose-2,6-P2, the decrease in the [ATP]/[ADP] ratio caused by citrate in the steady state system was similar to the decrease in the trigger point [ATP]/[ADP] ratio in the oscillatory system. The decrease in the average [ATP]/[ADP] ratio was greater in the steady state system than in the oscillating system. These results demonstrate advantages of oscillatory behavior of glycolysis in the regulation of carbohydrate utilization and the maintenance of a high [ATP]/[ADP] ratio.     

Spectroscopic investigations of the structure of DNA complexes with Mn2+ in UV and IR regions

Based on the data of UV and IR spectroscopy, electronic and vibrational circular dichroism, the interaction of manganese ions with DNA was investigated. It was shown that the binding of ions to DNA proceeds in three stages depending on the manganese-to-DNA phosphates molar ratio [Mn]/[P]. At the first stage ([Mn]/[P] < or = 1), the interaction of manganese ions with DNA phosphates occurs, causing a partial screening of their negative charge and the stabilization of the double helix. At the second stage (1 < [Mn]/[P] < 6), the ions interact with both the phosphates and the nitrogen bases of DNA. At this stage, it is possible for the manganese ion to coordinate simultaneously to the oxygen atom of the phosphate and the neighbouring base of DNA. At a higher [Mn]/[P] ratio, the destabilization of the double helix begins, and partial breakage of the hydrogen bonds between the nitrogen bases occurs.     

Adenine nucleotides in foetal rat liver cells. Compartmentation and variation with age.

The digitonin method for the separation of cytosolic and mitochondrial fractions was applied to liver cells isolated from foetal rats. The cytosolic [ATP]/[ADP] ratio approximately doubles during the last 4 days of gestation, whereas the mitochondrial ratio remains constant. In the presence of oligomycin and added glucose, the cytosolic [ATP]/[ADP] ratio does not increase with age, but is still considerably higher than the mitochondrial ratio. Without added glucose, and when the glycogen content of foetal liver is still very low (more than 3 days before birth), the cytosolic [ATP]/[ADP] ratio in the presence of oligomycin becomes very low and equal to the mitochondrial ratio. It is concluded that the increasein the cytosolic [ATP]/[ADP] ratio during the last 4 days of gestation is solely due to enhanced mitochondrial activity in this period. Atractyloside and bongkrekic acid do not influence the O2 consumption, nor the [ATP]/[ADP] ratios in either compartment of foetal liver cells. Respiration of isolated foetal mitochondria, however, is strongly inhibited by both compounds. The implications of these findings are discussed.     

Altered topoisomerase activities may be involved in the regulation of DNA supercoiling in aerobic-anaerobic transitions inEscherichia coli

This study uncovers a new mechanism of regulation of DNA supercoiling operativein vivo upon an aerobic-anaerobic transition inEscherichia coli. Exponentially growing aerobic batch cultures were subjected to a shift to anaerobic conditions. The ratio [ATP]/[ADP] remained essentially constant at 8.5 in the aerobic culture and after a transition to anaerobiosis while DNA supercoiling increased noticeably upon anaerobiosis. This result indicated that the mechanism of regulation of DNA supercoiling by the [ATP]/[ADP] ratio was not operative. The increase in DNA supercoiling was followed by a large decrease in the DNA-relaxing activity of topoisomerase I while gyrase activity remained relatively constant. This decrease in the activity of topoisomerase I is likely to be responsible for the increase in DNA supercoiling.Abbreviations TPE Tris-phosphate-EDTA buffer - TBE Tris-borate-EDTA buffer     

The light switch effect upon the association of [Ru(1,10-phenanthroline)2dipyrido[3,2-a:2',3'-c]phenazine]2+ with single stranded poly(dA) and poly(dT)

Large enhancement in the luminescence intensity of the Delta- and Lambda-Ru(phenanthroline)(2)dipyrido[3,2-a:2',3'-c]phenazine](2+) ([Ru(phen)(2)DPPZ](2+)) complexes upon their association with single stranded poly(dA) and poly(dT) is reported in this work. As the mixing ratio ([[Ru(phen)(2)DPPZ](2+)]/[DNA base]) increases, the luminescence intensity increase in a sigmoidal manner, indicating that the enhancement involves some cooperativity. At a high mixing ratio, the luminescence properties are affected by the nature of the DNA bases and not by the absolute configuration of the [Ru(phen)(2)DPPZ](2+) complex, indicating that the single stranded poly(dA) and poly(dT) do not recognize the configuration of the metal complex. In the case of the Lambda-[Ru(phen)(2)DPPZ](2+)-poly(dT) complex, the manner of the enhancement is somewhat different from the other Ru(II) complex-polynucelotide combinations: the luminescence intensity reached a maximum at an intermediate mixing ratio of 0.32, and gradually decreased as the mixing ratio increased. In contrast to other complexes at high mixing ratios, an upward bending curve was found in the Stern-Volmer plot, which indicates that the micro-environment of the Lambda-[Ru(phen)(2)DPPZ](2+) is heterogeneous. In the Delta-[Ru(phen)(2)DPPZ](2+)-poly(dT) complex case, formation of this highly luminescent species at an intermediate mixing ratio is far less effective.     

The stability of DNA-porphyrin complexes in the presence of Mn(II) ions

The complex formation of porphyrins with DNA leads to changes of stability of DNA. In the present study we investigated binding properties and the thermodynamic parameters of a water-soluble, cationic planar Cu(II)-containing meso-tetrakis(4-N-butyl-pyridiniumyl)porphyrin [CuTButPyP4] and nonplanar Co(II)-containing meso-tetrakis(4-N-butyl-pyridiniumyl)porphyrin [CoButPyP4] with calf thymus DNA in the presence of divalent manganese ions. For displaying the changes of thermodynamic parameters (T_m and ΔT) the melting curves of DNA-porphyrin complexes in the presence of Mn²⁺ ions have been obtained. The enthalpy (ΔH) of helix-coil transition has been also evaluated. It was shown that the binding of ions to DNA proceeds in two stages depending on the manganese/DNA phosphates molar ratio [Mn]/[P]. At the first stage (0.001 < [Mn]/[P] < 1), the interaction of manganese ions with DNA phosphates occurs, causing an additional screening of their negative charge and the stabilization of the double helix. As a result, the best conditions for intercalation of CuTButPyP4 or of peripheral rings of CoButPyP4 occur. The significant increase of T_m, but less changes of ΔT were observed. At the second stage (1 < [Mn]/[P] < 4), the ions interact with both the phosphates and the nitrogen bases of DNA. At this stage, it is possible for the manganese ion to coordinate simultaneously to the oxygen atom of the phosphate and the neighboring base of DNA. At a higher [Mn]/[P] ratio, the destabilization of the double helix begins, and partial breakage of the hydrogen bonds between the nitrogen bases occurs. Respectively the destabilization of DNA in the presence of both porphyrins takes place.     

Network structures and thermal properties of polyurethane films prepared from liquefied wood

Polyurethane (PU) films were prepared by solution-casting after co-polymerization of liquefied woods (LWs) and polymeric methylene diphenylene diisocyanate (PMDI). The resulting PU films had various [NCO]/[OH] ratios ranging from 0.6 to 1.4 and contained 5.0-16.8% dissolved woody components at the [NCO]/[OH] ratio of 1.0. The crosslink densities of the films with [NCO]/[OH] ratios of 0.6-1.4 increased remarkably with increasing [NCO]/[OH] ratio. Similarly, there were large increases in glass transition temperatures (Tg). These characteristics could be attributed to effective incorporation of PMDI into the LW. The crosslink densities and Tg of the PU films prepared at the [NCO]/[OH] ratio of 1.0 increased because the amounts of dissolved woody components in the films increased. It is concluded that the dissolved woody components acted as crosslinking points in PU network formations. The thermal degradation of the PU films at an [NCO]/[OH] ratio of more than 0.8 or with more than 10.6% dissolved wood started above 262 degrees C under an N2 atmosphere. The thermostability was lost at low crosslink density or with large amount of co-polymerized glycerol structures in the PU networks.     

Cobalt-bleomycin-deoxyribonucleic acid system. Evidence of deoxyribonucleic acid bound superoxo and mu-peroxo cobalt-bleomycin complexes

Co(II) interacts with bleomycin in aqueous solution, in the presence of air, to give a short-lived mononuclear superoxo Co(III) complex (I). Then, two molecules of complex I react together, with the loss of oxygen, to yield the dinuclear mu-peroxo Co(III) complex (II); the dimerization follows a second-order rate law with k2 = 200 +/- 50 M-1 s-1 at 25 degrees C. The rate of dimerization is lowered by a factor of 2000 when DNA is present at a molar ratio of [nucleotide]/[Co] higher than 16. These results and studies of circular dichroism and electron paramagnetic resonance spectra of complexes strongly suggest the binding of the superoxo complex to DNA (I') as well as that of the mu-peroxo complex (II'); the binding of 1 molecule of complex II for every 2.9 base pairs in DNA has been determined with an apparent equilibrium constant of 8.4 x 10(4) M-1.     

ATP-phosphocreatine metabolism catalyzed by creatine kinase. Comparison of saturation transfer (NMR) and isotope labeling technics

Unidirectional fluxes from ATP to phosphocreatine (PCr) catalyzed by MM-isoenzyme of creatine kinase (CK) were measured by using 31P-NMR saturation transfer technique and by means of radioactively labeled [gamma-32P]ATP. At 30-37 degrees C and pH 7.4 in a wide range of [PCr]/[creatine] ([PCr]/[Cr]) ratios (0.2 to 3.0) both of these methods gave similar results, thus showing that magnetization (saturation) transfer allows to determine fluxes close to real ones under "physiological" conditions. However, at [PCr]/[Cr] ratio higher than 5 ([ADP] less than 30 microM) or at decreased temperatures (7-15 degrees C, [PCr]/[Cr] approximately 1) fluxes determined by saturation transfer substantially exceeded those measured with the radioactive label. These data imply that under "physiological" conditions phosphoryl group transfer is actually rate-determining step of the CK reaction. On the contrary, at high [PCr]/[Cr] values or at low temperature the control step could be shifted from the phosphoryl group transfer or distributed among other steps of the reaction.     

Properties of the transfer ribonucleic acid methylase activity in vitro of hamster tumours induced by adenovirus-12. Base analysis

1. The ratio [ATP]/[ADP][P(i)], as measured by direct determination of the three components in rat liver, was found in various nutritional states to have approximately the same value as the ratio [ATP]/[ADP][P(i)] calculated from the concentrations of lactate, pyruvate, glyceraldehyde phosphate and 3-phosphoglycerate on the assumption that lactate dehydrogenase, glyceraldehyde phosphate dehydrogenase and 3-phosphoglycerate kinase are at near-equilibrium in the liver. This implies that the redox state of the NAD couple in the cytoplasm is linked to, and partially controlled by, the phosphorylation state of the adenine nucleotides. 2. The combined equilibrium constant of the glyceraldehyde 3-phosphate dehydrogenase and 3-phosphoglycerate kinase reactions at 38 degrees C and I0.25, was found to be 5.9x10(-6). 3. The fall of the [NAD(+)]/[NADH] ratio in starvation and other situations is taken to be the consequence of a primary fall of the [ATP]/[ADP][HPO(4) (2-)] ratio.     

Effects of ciprofibrate and 2-[5-(4-chlorophenyl)pentyl]oxirane-2-carboxylate (POCA) on the distribution of carnitine and CoA and their acyl-esters and on enzyme activities in rats. Relation between hepatic carnitine concentration and carnitine acetyltransferase activity.

The effects of feeding the peroxisome proliferators ciprofibrate (a hypolipidaemic analogue of clofibrate) or POCA (2-[5-(4-chlorophenyl)pentyl]oxirane-2-carboxylate) (an inhibitor of CPT I) to rats for 5 days on the distribution of carnitine and acylcarnitine esters between liver, plasma and muscle and on hepatic CoA concentrations (free and acylated) and activities of carnitine acetyltransferase and acyl-CoA hydrolases were determined. Ciprofibrate and POCA increased hepatic [total CoA] by 2 and 2.5 times respectively, and [total carnitine] by 4.4 and 1.9 times respectively, but decreased plasma [carnitine] by 36-46%. POCA had no effect on either urinary excretion of acylcarnitine esters or [acylcarnitine] in skeletal muscle. By contrast, ciprofibrate decreased [acylcarnitine] and [total carnitine] in muscle. In liver, ciprofibrate increased the [carnitine]/[CoA] ratio and caused a larger increase in [acylcarnitine] (7-fold) than in [carnitine] (4-fold), thereby increasing the [short-chain acylcarnitine]/[carnitine] ratio. POCA did not affect the [carnitine]/[CoA] and the [short-chain acylcarnitine]/[carnitine] ratios, but it decreased the [long-chain acylcarnitine]/[carnitine] ratio. Ciprofibrate and POCA increased the activities of acyl-CoA hydrolases, and carnitine acetyltransferase activity was increased 28-fold and 6-fold by ciprofibrate and POCA respectively. In cultures of hepatocytes, ciprofibrate caused similar changes in enzyme activity to those observed in vivo, although [carnitine] decreased with time. The results suggest that: (1) the reactions catalysed by the short-chain carnitine acyltransferases, but not by the carnitine palmitoyltransferases, are near equilibrium in liver both before and after modification of metabolism by administration of ciprofibrate or POCA; (2) the increase in hepatic [carnitine] after ciprofibrate or POCA feeding can be explained by redistribution of carnitine between tissues; (3) the activity of carnitine acetyltransferase and [total carnitine] in liver are closely related.     

Importance of coulombic end effects on cation accumulation near oligoelectrolyte B-DNA: a demonstration using 23Na NMR.

The local cation concentration at the surface of oligomeric or polymeric B-DNA is expected, on the basis of MC simulations (Olmsted, M. C., C. F. Anderson, and M. T. Record, Jr. 1989. Proc. Natl. Acad. Sci. USA. 86:7766-7770), to decrease sharply as either end of the molecule is approached. In this paper we report 23Na NMR measurements indicating the importance of this "coulombic" end effect on the average extent of association of Na+ with oligomeric duplex DNA. In solutions containing either 20-bp synthetic DNA or 160-bp mononucleosomal calf thymus DNA at phosphate monomer concentrations [P] of 4-10 mM, measurements were made over the range of ratios 1 < or = [Na]/[LP] < or = 20, corresponding to Na+ concentrations of 4-200 nM. The longitudinal 23Na NMR relaxation rates measured in these NaDNA solutions, Robs, are interpreted as population-weighted averages of contributions from "bound" (RB) and "free" (RF) 23Na relaxation rates. The observed enhancements of Robs indicate that RB significantly exceeds RF, which is approximately equal to the 23Na relaxation rate in an aqueous solution containing only NaCl. Under salt-fre-tconditions ([Na]/[P] = 1), where the enhancement in Robs is maximal, we find that Robs--RF in the solution containing 160-bp DNA is approximately 1.8 times that observed for the 20-bp DNA. For the 160-bp oligomer (which theoretical calculations predict to be effectively polyion-like), we find that a plot of Robs v. [P]/[Na] is linear, as observed previously for sonicated (approximately 700 bp) DNA samples. For the 20-bp oligonucleotide this plot exhibits a marked departure from linearity that can be fitted to a quadratic function of [P]/[Na]. Monte Carlo simulations based on a simplified model are capable of reproducing the qualitative trends in the 23Na NMR measurements analyzed here. In particular, the dependences of Robs--RF on DNA charge magnitude of Z(320 vs. 38 phosphates) and (for the 20-bp oligomer) on [Na]/[P] are well correlated with the calculated average surface concentration of Na+. Thus, effects of sodium concentration on RB appear to be of secondary importance. We conclude that 23Na NMR relaxation measurements are a sensitive probe of the effects of oligomer charge on the extent of ion accumulation near B-DNA oligonucleotides, as a function of [Na] and [P].     

The influence of local anesthetics on the gel-liquid crystal phase transition in model dipalmitoylphosphatidylcholine membranes

The influence of local anesthetics (LA): tetracaine, lidocaine, cocaine, dibucaine and heptacaine derivatives on the gel to liquid crystalline phase transition temperature (Tc) of model dipalmitoylphosphatidylcholine (DPPC) membranes was studied using electron spin resonance (ESR) and polarization microscopy methods. The decrease of Tc in the presence of anesthetics (delta Tc) was found to be dependent on the [DPPC]/[H2O] molar ratio at constant [LA]/[DPPC] molar ratio. Hence, the parameter alpha = delta Tc/[( LA]/[DPPC]) in dependence on [H2O]/[DPPC] was extrapolated to zero concentration of water and compared with biological efficiency.     

Competition between extramitochondrial and intramitochondrial ATP-consuming processes.

The relationship between intra- and extramitochondrial ATP utilization was investigated in liver mitochondria isolated from normally fed, starved and high-protein fed rats. ATP export was provoked by adding a hexokinase-glucose-trap and intramitochondrial ATP consumption by adding ammonia, bicarbonate and ornithine in order to stimulate citrulline synthesis. Both processes compete for ATP produced via oxidative phosphorylation; the rate of citrulline formation declines as the extramitochondrial [ATP]/[ADP] ratio decreases. It is concluded that ATP for adenine nucleotide translocation and that for carbamoyl phosphate synthesis are delivered from a common intramitochondrial pool of adenine nucleotides. In mitochondria from rats with a high-protein diet, citrulline synthesis greatly stimulates the rate of oxidative phosphorylation (about two thirds of state 3 respiration). Under these conditions the intramitochondrial [ATP]/[ADP] ratio is significantly reduced. The intramitochondrial [ATP]/[ADP] ratio is not in thermodynamic equilibrium with the extramitochondrial one.     

Klebsiella pneumoniae nitrogenase. Inhibition of hydrogen evolution by ethylene and the reduction of ethylene to ethane.

Ethylene (C2H4) inhibited H2 evolution by the Mo-containing nitrogenase of Klebsiella pneumoniae. The extent of inhibition depended on the electron flux determined by the ratio of Fe protein (Kp2) to MoFe protein (Kp1) with KiC2H4 = 409 kPa ([Kp2]/[Kp1] = 22:1) and KC2H4i = 88 kPa ([Kp1]/[Kp2] = 21:1) at 23 degrees C at pH 7.4. At [Kp2]/[Kp1] = 1:1, inhibition was minimal with C2H4 (101 kPa). Extrapolation of data obtained when C2H4 was varied from 60 to 290 kPa indicates that at infinite pressure of C2H4 total inhibition of H2 evolution should occur. C2H4 inhibited concomitant S2O4(2-) oxidation to the same extent that it inhibited H2 evolution. Although other inhibitors of total electron flux such as CN- and CH3NC uncouple MgATP hydrolysis from electron transfer, C2H4 did not affect the ATP/2e ratio. Inhibition of H2 evolution by C2H4 was not relieved by CO. C2H4 was reduced to C2H6 at [Kp2]/[Kp1] ratios greater than or equal to 5:1 in a reaction that accounted for no more than 1% of the total electron flux. These data are discussed in terms of the chemistry of alkyne and alkene reduction on transition-metal centres.     

Synthesis and analysis of nucleosides bearing pyrrolepolyamide binding to DNA

An efficient synthesis of adenosine bearing pyrrolepolyamide 1 was achieved by coupling of 3 with 2. The CD spectra obtained at several [ligand ]/[duplex] ratios allowed verification of the formation complex of the DNA duplex [d(CGCAAATTGGC)/d(GCCAATTTGCG)] with 1.