PubMed · 4389435
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R Jannasch. 1967. [Ganglionic-blocking agents. 9].. https://pubmed.ncbi.nlm.nih.gov/4389435/
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Interactions of divalent polyamines with double-helical DNA in aqueous solution are investigated by monitoring the decrease in 23Na NMR relaxation rates as NaDNA is titrated with H3N(+)-(CH2)m-+NH3, where m = 3, 4, 5, or 6. Analogous measurements are made for the same homologous series of methylated polyamines (methonium ions). The dependence of the 23Na relaxation rates on the amount of added divalent cation (M2+) is analyzed quantitatively in terms of a two-state model. The sodium ions are assumed to be in rapid exchange between a "bound" state, where they are close enough to DNA so that it affects their relaxation rate, and a "free" state in bulk solution, where their relaxation rate is the same as in solutions containing no DNA. The distribution of Na+ and M2+ between these states is described quantitatively in terms of an ion-exchange parameter: DM = (pMB)(1-pNaB)n/(pNaB)n(1-pMB), where pNaB and pMB are the fractions of Na+ and M2+ that are close enough to DNA to be considered bound (by the NMR criterion), and n is the number of sodium ions displaced from DNA by the binding of one M2+ ion. For each of the polyamines and methonium ions investigated here, equations derived from this two-state model yield acceptable fittings of the titration curves if roNa, the number of sodium ions bound per DNA phosphate when no competing cations are present, is assigned a value between 0.6 and 1.00. Within this range, changing the value assigned to roNa does change the best-fitted values of DM determined for these polyamines (DH) and for the methonium ions (DMe) but does not alter the following conclusions about the trends in these parameters. (1) For polyamines and methonium ions of the same m, DH exceeds DMe by factors that are significantly larger for m = 3 and 4 than for m = 5 and 6. (2) DH for m = 3 and 4 is larger than DH for m = 5 and 6. (3) DMe for m = 3 and 4 is smaller than DMe for m = 5 and 6.
A novel spectroscopic method is described for following the kinetics of resealing of hemolysed erythrocyte ghosts. The procedure is based on the broadening of the EPR spectrum of nitroxyl radicals by paramagnetic ions. The method is used to study the effect of Ca2+, Mg2+ and dimethonium ion on the kinetics of resealing.
Calcium and other alkaline earth cations change the electrostatic potential adjacent to negatively charged bilayer membranes both by accumulating in the aqueous diffuse double layer adjacent to the membrane and by adsorbing to the phospholipids. The effects of these cations on the electrostatic potential are described adequately by the Gouy-Chapman-Stern theory. We report the results of experiments with ethane-bis-trimethylammonium, a cation that has been termed "dimethonium" or "ethamethonium" in analogy with hexamethonium (hexane-1,6-bis-trimethylammonium) and decamethonium (decane-1,10-bis-trimethylammonium). We examined the effect of dimethonium on the zeta potential of multilamellar vesicles formed from the negative lipid phosphatidylserine (PS) and from 5:1 phosphatidylcholine/phosphatidylserine mixtures in solutions containing 0.1, 0.01 and 0.001 M sodium, cesium, or tetramethylammonium chloride. We also examined the effect of dimethonium on the conductance of planar PS bilayer membranes and the 31P NMR signal from sonicated PS vesicles formed in 0.1 M NaCl. We found no evidence that dimethonium adsorbs specifically to bilayer membranes. All the results, except for those obtained with vesicles of low charge density formed in a solution with a high salt concentration, are consistent with the predictions of the Gouy-Chapman theory. We conclude that dimethonium, which does not have the pharmacological effects of hexamethonium and decamethonium, is a useful divalent cation for physiologists interested in investigating electrostatic potentials adjacent to biological membranes.