Divalent cation shrinks DNA but inhibits its compaction with trivalent cation

Abstract

Our observation reveals the effects of divalent and trivalent cations on the higher-order structure of giant DNA (T4 DNA 166 kbp) by fluorescence microscopy. It was found that divalent cations, Mg(2+) and Ca(2+), inhibit DNA compaction induced by a trivalent cation, spermidine (SPD(3+)).On the other hand, in the absence of SPD(3+), divalent cations cause the shrinkage of DNA.As the control experiment, we have confirmed the minimum effect of monovalent cation, Na(+) on the DNA higher-order structure. We interpret the competition between 2+ and 3+ cations in terms of the change in the translational entropy of the counterions. For the compaction with SPD(3+), we consider the increase in translational entropy due to the ion-exchange of the intrinsic monovalent cations condensing on a highly charged polyelectrolyte, double-stranded DNA, by the 3+ cations. In contrast, the presence of 2+ cation decreases the gain of entropy contribution by the ion-exchange between monovalent and 3+ ions. C 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license

Opposite effect of polyamines on In vitro gene expression: Enhancement at low concentrations but inhibition at high concentrations

“…Our experiments were conducted in a simplified model system to focus on the action of polyamines on DNA. Further studies in the nonspecific but significant effect of polyamines on DNA and other negatively-charged biomolecules by taking into account the influence of cationic species [ 35 , 36 ] such as K + and Mg 2+ would provide useful insight regarding mechanisms of living matters as autonomous self-control system.…”

Nonspecific characteristics of macromolecules create specific effects in living cells

“…In addition, the compaction of long DNAs with polycations like polyamines (spermine and spermidine) and histone can be observed at the level of individual chains as a first-order phase transition, which is believed to be caused by the exchange of counter ions that have accumulated around DNAs (Takahashi et al 1997;Murayama and Yoshikawa 1999). The folding transition occurs essentially in an all-or-none (intermolecular) manner, i.e., each DNA molecule can assume a folded (compacted) or unfolded morphology depending on the polycation concentration (Takahashi et al 1997;Tongu et al 2016). Interestingly, the distance within which the phase transition can propagate along the chain can be modulated by the concentration ratio of polyvalent to mono-/di-valent salts, since a coexisting salt with a lower valency can alter the free energy of the system, or apparently shield electrostatic interaction by competing for binding sites on DNAs with polycations (Yoshikawa 2001).…”

The Mixing Counterion Effect on DNA Compaction and Charge Neutralization at Low Ionic Strength

“…In classical Manning-Oosawa condensation theory, the fraction of counterions condensing on uniformly charged rod depends only on the valence of counterions, but is independent of other factors, such as type of ions, pH and ionic strength in solution [41]. When many types of counterions exist in solution, the electrostatic interaction between DNA and counterions becomes much more complicated than the case of single counterion [42,43,44,45,46,47]. It has been shown that increasing monovalent salt concentration hinders charge inversion by multivalent ions [10,48].…”