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PubMed1990

Antimutagenesis in yeast by sodium chloride, potassium chloride, and sodium saccharin.

Aqueous salt solutions containing NaCl, KCl, MgCl2, Na2SO4, CaCl2, NH4Cl, or sodium saccharin are mutagenic in yeast when logarithmic growth of cells is interrupted by exposure to a 0.5-2.0 M salt solution. Stationary-phase cells are not mutated by this treatment. When placed in an enriched medium with the salt, the stationary-phase cells grow after a prolonged lag period. The compounds tested (NaCl, KCl, and sodium saccharin), under conditions in which growth in medium can take place, exhibit an antimutagenic response as measured by the compartmentalization test. The antimutagenic action of salt solutions in yeast is concentration-dependent. Unlike the mutagenic action of these compounds, which approximates an osmolality-dependent response, the antimutagenic action seems to be correlated with toxicity as measured by growth rate reduction at increasing concentrations of the compounds. For example, sodium saccharin and NaCl exhibit almost identical osmolalities; however, 0.3 M sodium saccharin reduces the growth rate much more than does 0.3 M NaCl. At these same molar concentrations, the spontaneous mutation rate for histidine prototrophy is, for the control, 6.2 x 10(-8) mutations/cell/-generation, 3.5 x 10(-8) with 0.3 M NaCl, and 1.7 x 10(-8) with 0.3 M sodium saccharin.

Depression, Chemical↗

PubMed1986

Radiolabelled substrates for angiotensin converting enzyme.

Six [3H]benzoyl-tripeptides were prepared and tested as substrates for angiotensin converting enzyme. Each was prepared first as its [4-iodo]-benzoyl-analog, and an atom of 3H per molecule was introduced by catalytic dehalogenation in 3H2-gas. Kinetic parameters were measured at 37 degrees C using as buffer 0.05 M Hepes, pH 8.0 containing 0.1 M NaCl and 0.6 M Na2SO4. When the substrates were used at concentrations far below their respective Km values, fractional rates of substrate utilization per unit time for constant enzyme concentration were direct function of respective second order rate constants (Kc/Km). Although absolute values of Kc/Km differed for human enzyme as opposed to rabbit enzyme, relative values of Kc/Km were virtually identical. Similarly, relative rates of substrates utilization during passage through lungs of anesthetized rats were similar to relative values of Kc/Km measured in vitro. Thus, there is now a range of ACE substrates usable, in vitro and in vivo, under conditions of first order enzyme kinetics, conditions under which values of V/Km and Ki can be measured directly.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed1993

Deposition of BaSO4 in the tight junctions of amphibian epithelia causes their opening; apical Ca2+ reverses this effect.

Selective deposition of BaSO4 in the tight junctions (TJs) of frog skins led to profound and reversible functional alterations of these structures, as revealed by changes of tissue conductance (G), clamping current (I), and fluxes of extracellular markers (sulfate (JSO4) and sucrose (JSUC)). Experiments were performed with nominally Ca(2+)-free simple salt solutions on the apical side (usually KCl) and Na2SO4-Ringer on the inner side of skins. The deposition of BaSO4 in the TJs was obtained by diffusion and/or migration through the paracellular path of Ba2+ from the apical solution and SO4(2-) from the inner solution. A brief presence (2 to 6 min) of apical Ba2+ (Ba2+ pulse) is followed (i.e., when Ba2+ is removed from the apical fluid) by a large increase of G, I, JSO4 and JSUC, above pre-Ba2+ levels. These attain a steady state within 15 to 30 min (overshoot phase), characterizing a conspicuous increase of the paracellular permeability. During the overshoot phase, a second Ba2+ pulse blocks the paracellular route while apical Ba2+ is present, leading to a new and larger overshoot when the Ba2+ pulse is terminated. Addition of apical Ca2+ triggers the resealing of the TJs, resulting in a full recovery of G, I, JSO4 and JSUC. This Ca(2+)-induced recovery persists when apical Ca2+ is removed. The presence of a normal Ca2+ concentration in the inner bathing Ringer does not induce the recovery process. Tissues remain viable after being submitted to the Ba2+ treatment and the subsequent overshoot. Experiments performed in the urinary bladder of Rana catesbeiana and skins and urinary bladders of Bufo marinus indicate that Ba2+ effect can also be elicited in these tissues. The above results seem to report general properties of the TJs. Incidentally, they warn about the use of Ba2+ as an ion channel blocker in epithelial membranes in association with SO4(2-)-containing solutions on the contralateral side.

Animals↗

PubMed1991

Effects of environmental conditions on mitochondrial-rich cell density and chloride transport in toad skin.

Chloride flux across amphibian skin is usually passive, yet largely conductive; previous reports have suggested that aldosterone influences this pathway. The conductive Cl- pathway and its regulation were examined further, across the abdominal skin of toads (Bufo marinus) adapted to various environments. Short-circuit current (Isc), total conductance (Gt) and Cl- influx (JCl) were measured in conditions such that there was net Cl- movement in absence of Na+ transport. In salt-deprived animals compared to salt-adapted ones, there was a significant increase in JCl (563 vs 200 pmol cm-2 s-1), aldosteronaemia (4.2 vs 1.1 nmol/l), as well as MRC density (1458 vs 851 mm-2). After adaptation to dilute Na2SO4 compared to MgCl2, JCl (631 vs 313 pmol cm-2 s-1) as well as the density of mitochondria-rich cells (MRC) (1306 vs 710 mm-2) practically doubled, while the toads' aldosteronaemia was lower (2.4 vs 10.8 mmol/l). In all groups of toads, JCl was matched by Isc, and there was a close correlation between Gt and JCl (r = 0.96), which confirms the conductive nature of transepithelial Cl- movement. Furthermore, the relationship between JCl and MRC density (r = 0.75) argues in favour of a role played by MRC on Cl- conductance of epithelial such as amphibian skin. As aldosterone injected for 1 week into NaCl-adapted toads did not influence MRC density and as aldosteronaemia was not correlated with Cl- conductance, this hormone does not emerge as the determinant of these parameters.

Aldosterone↗

PubMed1977

Adenosine-5'-phosphosulfate (APS) as sulfate donor for assimilatory sulfate reduction in Rhodospirillum rubrum.

Crude extracts of Rhodospirillum rubrum catalyzed the formation of acid-volatile radioactivity from (35S) sulfate, (35S) adenosine-5'-phosphosulfate, and (35S) 3'-phosphoadenosine-5'-phosphosulfate. An enzyme fraction similar to APS-sulfotransferases from plant sources was purified 228-fold from Rhodospirillum rubrum. It is suggested here that this enzyme is specific for adenosine-5'-phosphosulfate, because the purified enzyme fraction metabolized adenosine-5'-phosphosulfate; 3'-phosphoadenosine-5'-phosphosulfate, however, only at a rate of 1/10 of that with adenosine-5'-phosphosulfate. Further, the reaction with 3'-phosphoadenosine-5'-phosphosulfate was inhibited with 3'-phosphoadenosine-5'-phosphate whereas this nucleotide had no effect on the reaction with adenosine-5'-phosphosulfate. For this activity with adenosine-5'-phosphosulfate the name APS-sulfotransferase is suggested. This APS-sulfotransferase needs thiols for activity; good rates were obtained with either dithioerythritol or reduced glutathione; other thiols like cysteine, 2'-3'-dimercaptopropanol or mercaptoethanol are less effective. The electron donor methylviologen did not catalyze this reaction. The pH-optimum was about 9.0; the apparent Km for adenosine-5'phosphosulfate was determined to be 0.05 mM with this so far purified enzyme fraction. Enzyme activity was increased with K2SO4 and Na2SO4 and was inhibited by 5'-AMP. These properties are similar to assimilatory APS-sulfotransferases from spinach and Chlorella.

Adenine Nucleotides↗

PubMed1985

The extrarenal effects of aldosterone on the distribution of extracellular fluid in conscious adrenalectomized-nephrectomized rats.

In order to examine the extrarenal roles of aldosterone in cardiovascular homeostasis, the present study compared blood pressure, extracellular fluid volume (ECFV) and plasma volume (PV) in the three following groups: 10 nephrectomized (NX) rats, 10 nephrectomized-adrenalectomized (NX-AX) rats, and 10 NX-AX and aldosterone-treated (NX-AX-A) rats. Two-hundred and fifty micrograms of aldosterone, mixed with sesame oil, was given subcutaneously in the NX-AX-A rats. Mean arterial pressure (MAP) was recorded through previously implanted carotid catheters. ECFV and PV were measured using 35S-Na2SO4 and 131I-RISA, respectively, 24 h after the operation. These measurements were performed in an unanesthetized and unrestricted condition. MAP gradually increased in the NX group, while a gradual decrease was observed in the other groups. However, MAP was significantly higher in the NX-AX-A group than in the NX-AX group 6 h after the operation and thereafter. Changes in body weight were comparable in the three groups 24 h after the operation. ECFV and PV were both reduced in the NX-AX and the NX-AX-A groups as compared to the NX group (P less than 0.001 NX-AX vs NX, and P less than 0.05 and P less than 0.025 NX-AX-A vs NX, respectively). Although ECFV was comparable in the NX-AX and the NX-AX-A groups, PV was significantly greater in the NX-AX-A group than in the NX-AX group (P less than 0.05). There was a significant positive correlation between MAP and PV in the rats as a whole (r = 0.68, P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenalectomy↗

PubMed1985

Quinidine blockage of K+ channels in the basolateral membrane of larval bullfrog skin.

The skin of frog larvae (Rana catesbeiana) was used to study the characteristics of basolateral K+ channels with fluctuation analysis. K2SO4 and Na2SO4 Ringer's were used as mucosal and serosal solution, respectively. After addition of Nystatin (138 U/ml) the transepithelial conductance and short-circuit current (Isc) increased considerably. Most of Isc was carried by K+, moving from the mucosal to the serosal side. This current could be depressed by quinidine, added to both compartments or to mucosal side only. Fluctuation analysis showed that quinidine induced a Lorentzian component in the power density spectrum. Assuming pseudo-first order kinetics for the channel occlusion by quinidine the current through the open K+ channel and channel density were calculated: iK = 0.22 pA, M = 7.7 channels/microns2.

Animals↗

PubMed1989

Segmental heterogeneity of basal and aldosterone-induced electrogenic Na transport in human colon.

Recent in vitro studies in human colon have demonstrated marked segmental differences in electrogenic Na transport. In the present study, the Na channel blocker amiloride was used further to characterise basal and aldosterone-induced electrogenic Na transport in isolated human distal and proximal colon. Bathed in NaCl Ringer solution, distal and proximal colon exhibited similar basal electrical properties, but the amiloride-sensitive short-circuit current (Isc) was 200% greater in the distal than in the proximal segment. Bathed in choline-Cl Ringer solution, total Isc decreased by 97% in distal colon and by 88% in proximal colon, indicating that Na dependent transport process(es) account almost entirely for the Isc in both segments. Substituting Na2SO4 for NaCl Ringer solution (i) increased amiloride-sensitive Isc by 56% (p less than 0.01) in distal colon but had no effect on amiloride-sensitive Isc in proximal colon, and (ii) decreased amiloride-insensitive Isc in distal and proximal colon by 52% (p less than 0.05) and 81% (p less than 0.001) respectively. After the addition of nystatin to the apical membrane, the relationship between total Isc and mucosal Na concentration indicated that the activity of the basolateral membrane Na pump was similar in both colonic segments. In a further series of experiments, exposure of distal colon to 1 mumol/l aldosterone for 5 h increased total Isc by 52% (p less than 0.05), which reflected stimulation of its amiloride-sensitive component; in contrast, aldosterone had no effect on proximal colon.(ABSTRACT TRUNCATED AT 250 WORDS)

Aldosterone↗

PubMed1988

Involvement of Na and Cl in ouabain-induced cell swelling in thick ascending limb of rat kidney.

Changes in the volume of isolated segments of rat medullary thick ascending limb (MAL) were studied by a photographic technique, after tubule incubation in isotonic solutions in the absence or presence of ouabain and/or K. When segments were incubated at 30 degrees C in NaCl solution, their volume increased by 75% after removal of external K, and by 170% after removal of external K plus addition of 1 mmol/l ouabain. At steady state, tubular volume was a function of the external K concentration. Resting volume was obtained with external K concentrations higher than 0.1 and 1.0 mmol/l in the absence and presence of ouabain respectively. When MAL samples were incubated in isotonic K-free Na2SO4 or K-free choline Cl solution, their volume per unit of length was similar to that determined in NaCl medium, but there was no swelling after the addition of ouabain. The ouabain-induced swelling was shown to depend on both the Na and Cl concentrations in the incubate (apparent Km of 87 and 80 mmol/l for Na and Cl respectively). Swollen tubules recovered their resting volume when ouabain, Na or Cl was removed from the incubation medium. Recovery of resting volume was also observed after addition of K into the incubation medium. These observations indicate that rat MAL cell volume is the result of coupled passive net fluxes of Na and Cl, which depend on the respective electrochemical gradients for Na or Cl across the cell membranes and the Na-pump activity which continuously extrudes Na.

Animals↗

PubMed1982

The effects of chronic papillary necrosis on acid excretion.

Complete papillary necrosis in rats can be induced within 1 month following a single injection of 2-bromoethylamine hydrobromide (BEA) (50 mg, i.v.). Utilizing a combination of clearance and balance techniques the effects of complete absence of the papilla was examined as regards urinary acidification, whole kidney glomerular filtration rate (GFR), single nephron GFR, and morphology. Whole kidney GFR was not different from control, however, the percent filtering juxtamedullary nephrons was markedly diminished (87.2 +/- 2.1 vs. 31.5 +/- 3.6% filtering, control vs. BEA, respectively, P less than 0.001) and significantly reduced in the superficial nephrons (80.6 +/- 3.6 vs. 62.2 +/- 6.1% filtering, control vs. BEA, respectively, P less than 0.05). There was a significant decrease in juxtamedullary single nephron GFR and an increase in the superficial single nephron GFR as assessed by the quantitative Hanssen's technique in the animals with chronic papillary necrosis. Complete papillary necrosis was associated with normal arterial bicarbonate concentration, pH, and plasma electrolyte concentrations. At the same degree of acidemia (induced by NH4Cl administration) minimal urinary pH, ammonium excretion, and titratable acid excretion were not different than seen in age matched controls. The response to Na2SO4 infusion and phosphate infusion was the same in both groups of animals. The urine-blood (U-B)pCO2, and index of urinary acidification, was identical in BEA and control animals. Scanning electron microscopy showed scarring of the juxtamedullary glomeruli one month after BEA. The papilla was sloughed and lying free in the renal pelvis in every experimental animal. These data demonstrate that complete papillary necrosis is not associated with acidosis nor a defect in urinary acidification.

Absorption↗

PubMed1978

The selectivity of the delayed potassium conductance of frog skeletal muscle fibers.

A voltage-clamp technique was used to measure reversal potentials of delayed currents in frog skeletal muscle fibres immersed in solutions containing Li2SO4,Na2SO4,K2so4,Rb2SO4, or Cs2SO4. The selectivity sequence found for the underlying permeability mechanism was K greater than or equal to Rb greater than Cs greater than Na greater than or equal to Li.

Animals↗

PubMed1989

The key role of the mitochondria-rich cell in Na+ and H+ transport across the frog skin epithelium.

We have investigated the possibility that the mitochondria-rich (MR) cells participate in sodium and proton transport, when the frog skin epithelium is bathed on its apical side with solutions of low Na+ concentration, by comparing transport rates with morphological observations (MR cell number and MR cell pit surface area). Frogs were adapted to various salinities or the isolated skins were treated with the following hormones, deoxycorticosterone acetate (DOCA), arginine vasotocin (AVT) and oxytocin in order to modify the transport of sodium and hydrogen ions. Adaptation of the frogs (either 3-4 days or 7-10 days) to distilled water, NaCl (50 mmol/l), KCl (50 mmol/l) or Na2SO4 (25 mmol/l) solutions modified the Na+ transport rate and the morphology of the epithelium. The highest Na+ transport rates were found for the animals adapted to the Na+ free solutions and were correlated with an increase in the total MR cell pit surface area (number of MR cells x individual cell pit-surface area). The KCl adaptated group showed the largest increase in sodium and proton transport and also presented a metabolic acidosis as reflected by plasma acidification (pCO2 increase and HCO3- decrease). Proton secretion and sodium absorption were also found to be stimulated by either serosal DOCA addition (10(-6) M) or during acidification of the epithelium by serosally applied CO2. Na+ transport was enhanced by AVT (10(-6) M) or oxytocin (100 mU/ml) when the skin was bathed on its apical side with a high Na+ containing solution (115 mmol/l), whereas these hormones did not exert any effect on Na+ transport when the apical solution was low in Na+ (0.5 mmol/l).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1986

Regulation of intracellular sodium and pH by the electrogenic H+ pump in frog skin.

We have investigated the role of the electrogenic hydrogen ion pump in the regulation of intracellular sodium ion activity (aiNa) and intracellular pH (pHi) in frog skin epithelial cells using double-barreled ion sensitive microelectrodes. When Rana esculenta skin is mounted in an Ussing chamber and bathed in 1 mM Na2SO4 buffered to pH 7.34 with imidazole on the apical side and in normal Ringer on the serosal side, the apical addition of the carbonic anhydrase inhibitor ethoxzolamide (10(-4)M) blocks net H+ ion excretion and Na absorption, producing a depolarization of 25-30 mV of the apical membrane potential (psi mc). We demonstrate that these changes are accompanied by a fall in aiNa from 6.2 +/- 0.5 mmol/l to 3.4 +/- 0.6 mmol/l and an increase in pHi from 7.20 +/- 0.03 to 7.38 +/- 0.08 (n = 12 skins). Voltage clamping psi mc to its control value in the presence of ethoxzolamide restored aiNa but the pHi remained alkaline. Furthermore, the fall in aiNa produced by ethoxzolamide could be mimicked by voltage clamping psi mc towards the value of the Nernst potential for Na at the apical membrane. These results indicate that the maintenance of the cellular Na+ transport pool is dependent on a favourable electrical driving force and counter-current generated by an electrogenic H+ pump at the apical membrane. Addition of amiloride (10(-5) mol/l) or substitution of external Na+ by Mg2+ or K+ caused a hyperpolarization of psi mc and a fall in aiNa.2+ e

Amiloride↗

PubMed1993

Lysosomal sulfate efflux following glycosaminoglycan degradation: measurements in enzyme-supplemented Maroteaux-Lamy syndrome fibroblasts and isolated lysosomes.

Studies using lysosomal membrane vesicles have suggested that efflux of the sulfate that results from lysosomal glycosaminoglycan degradation is carrier-mediated. In this study, glycosaminoglycan degradation and sulfate efflux were examined using cultured skin fibroblasts and lysosomes deficient in the lysosomal enzyme N-acetylgalactosamine-4-sulfatase. Such fibroblasts store dermatan sulfate lysosomally, which could be labelled biosynthetically with Na2(35)SO4. The addition of recombinant N-acetylgalactosamine-4-sulfatase to the media of 35S labelled fibroblasts degraded up to 82% of the stored dermatan [35S] sulfate over a subsequent 96 h chase and released inorganic [35S] sulfate into the medium. In the presence of 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid (SITS), sulfate was reused to a minor extent in newly synthesized proteoglycan. Isolated granules from recombinant enzyme supplemented fibroblasts degraded stored dermatan [35S]sulfate to sulfate which was rapidly released into the medium at a rate that was reduced by the extra-lysosomal presence of the lysosomal sulfate transport inhibitors SITS, Na2SO4 and Na2MoO4. SITS also inhibited dermatan sulfate turnover, although it had no effect on the action of purified recombinant enzyme in vitro. These data imply that sulfate clearance occurred concomitantly with dermatan sulfate turnover in the lysosome even at high substrate loading, and that lysosome-derived sulfate, while available, is reutilized minimally in synthetic pathways.

Cells, Cultured↗

PubMed1994

Contractions of the filariid Acanthocheilonema viteae induced by potassium chloride.

The effects of K+ on muscle contractility were explored in the filarial nematode Acanthocheilonema viteae (Dipetalonema viteae). The parasite was slit open longitudinally and mounted in a smooth muscle chamber that was filled with aerated (95% N2-5% CO2) physiological solution at 37 degrees C. KCl at concentrations ranging from 20 to 100 mM induced a rapid isotonic contraction of the filarial muscle. The maximal response from KCl was similar to the maximal response to acetylcholine chloride (ACh). When KCl was applied for several minutes, tolerance frequently occurred. Contractions were also induced by K2SO4 but not by NaCl, Na2SO4 or sucrose. Nifedipine was more than 10 times as potent in reducing the KCl-induced contraction as in reducing that caused by ACh. The KCl-induced contraction was abolished in a Ca-free physiological medium containing ethyleneglycol-bis-(beta-aminoethyl ether) N, N, N', N'-tetraacetic acid (EGTA, 10(-4) M). Low [Ca2+]/[Mg2+] solutions blocked the spontaneous activity, the KCl-induced contractions, and the ACh-induced contractions. KCl also induced contractions in denervated muscle strips, supporting the hypothesis that K+ acts directly on the muscle cells. These results indicate that K+ can depolarize the muscle membrane and induce a muscle contraction that is dependent on extracellular calcium ions.

Animals↗

PubMed1988

Salt-induced enhancement of measles virus yields in cultured cells.

Supplementation of culture medium with MgSO4 or Na2SO4 in millimolar concentrations caused an enhanced measles virus (MV) yield from cultured quail embryo cells. MgSO4 at 25-50 mM concentrations exhibited the most pronounced and consistent stimulatory effect. MV infectivity increases ranged from 2- to 200-fold; the effect was highly reproducible for stationary monolayer, roller or microcarrier-grown cell culture types. MgSO4 also improved MV plaque development and caused MV plaque size enlargement on Vero cell monolayers. At mM concentrations MgSO4 was not operative as a MV thermostabilizing agent; rather, salt-induced enhancement of MV yields appeared to be due to intracellular events, e.g., augmented viral protein synthesis.

Animals↗

PubMed1987

Soluble minerals in chemical evolution. II. Characterization of the adsorption of 5'-AMP and 5'-CMP on a variety of soluble mineral salts.

The adsorption of 5'-AMP and 5'-CMP was studied in saturated solutions of several soluble mineral salts (NaCl, Na2SO4, MgCl2 X 6H2O, MgSO4 X 7H2O, CaCl2 X 2H2O, CaSO4 X 2H2O, SrCl2 X 6H2O, SrSO4, and ZnSO4 X 7H2O) as a function of pH, ionic strength, and surface area of the solid salt. The adsorption shows a pH dependence; this can be correlated with the charge on the nucleotide molecule which is determined by the state of protonation of the N-1 nitrogen of 5'-AMP or N-3 nitrogen of 5'-CMP and the phosphate oxygens. The adsorption which results from the binding between the nucleotide molecule and the salt surface is proposed as being due to electrostatic forces. It was concluded that the adsorption was reversible in nature. The adsorption shows a strong dependence upon ionic strength and decreases with increasing ionic strength. Surface area is shown to be an important factor in evaluating and comparing the magnitude of adsorption of nucleotides onto various mineral salts. The implications of the results of the study are discussed in terms of the importance of soluble mineral salts as adsorption sites in the characterization of the adsorption reactions of an adsorbed template in biogeochemical cycles.

Adenosine Monophosphate↗

PubMed1986

The adsorption and reaction of adenine nucleotides on montmorillonite.

The binding of AMP to Zn(2+)-montmorillonite was investigated in the presence of buffers and salts. Good's buffers, piperazine-N,N'-bis(2-ethanesulfonate) [PIPES] and morpholine-N-2-ethanesulfonate [MES], perturbed the exchangeable cations to a lesser extent (only 9% of Zn2+ displaced by 0.2 M buffer) than was observed with imidazole and lutidine buffers or NaCl and KCl salts (up to 80% of Zn2+ displaced). AMP adsorption isotherms measured in the presence of 0.2 M PIPES, MES, or Na2SO4 exhibited normal Langmuir-type behavior. The adsorption coefficient, KL, is 3-fold greater in the presence of HEPES or PIPES than it is in the absence of buffers. Basal spacings measured by X-ray diffraction for Zn(2+)-montmorillonite are 13 and 15 angstroms in the presence of PIPES, while a value of 12.8 angstroms was determined in the absence of PIPES. These data are interpreted in a model in which the adsorption of AMP is mediated by a Zn2+ complex of PIPES in different orientations in the interlamellar region of the montmorillonite. The type of exchangeable cation does not affect the ability of the lattice-bound Fe3+ in the montmorillonite to oxidize diaminomaleonitrile (DAMN). Exchangeable Cu2+ oxidizes DAMN, but exchangeable Fe3+ is nearly ineffective as an oxidant. The addition of DISN to 3'-AMP bound to Zn(2+)-montmorillonite in the presence of 0.2 M PIPES resulted in a higher yield of 2',3'-cAMP than is observed with a comparable concentration of Zn2+, a result which inplicates surface catalysis by the montmorillonite.

Adenine Nucleotides↗