Counterion NMR in polyelectrolyte solutions

Reimarsson, Pétur; Parello, Joseph; Drakenberg, Torbjörn; Gustavsson, Hans; Lindman, Björn

doi:10.1016/0014-5793(79)80583-9

Cited by 35 publications

(5 citation statements)

References 13 publications

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“…4. Only the line widths measured at three-fourths of the peak height have a temperature dependence consistent with that reported by Reimarsson et al (11). The line widths shown in Fig.…”

Section: Resultssupporting

confidence: 90%

²⁵ Mg NMR in DNA solutions: Dominance of site binding effects

Rose

Bleam

Record

et al. 1980

Proc. Natl. Acad. Sci. U.S.A.

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25Mg NMR spectroscopy is applied to a study of magnesium ion interactions with DNA, which is considered as a model for a linear polyelectrolyte. It is demonstrated that the magnesium ion spectrum is complicated by a non-Lorentzian line shape and is dominated by the effects of chemical exchange with macromolecule binding sites. A distinction is made between specific-site interactions in which the magnesium ion loses a water molecule from the first coordination sphere on binding and those interactions, referred to as territorial binding, in which the ion maintains its first coordination sphere complement of solvent. The first type of site-binding interactions are shown to dominate the magnesium ion NMR spectrum, based on a consideration of the magnitudes of the observed 25Mg relaxation rates compared with 3Na relaxation rates, the clear contributions of chemical exchange-limited relaxation, and an ion displacement experiment employing sodium.Magnesium ion is essential for a number of critically important life-sustaining processes (1). Magnesium ion interactions with polyanions are not understood at an atomic level (2, 3); however, two types may be anticipated: specific interactions involving metal-ligand association in the classical sense and nonspecific interactions dominated by purely electrostatic forces (3).An association between oppositely charged particles is expected even in solutions of simple electrolytes (4). The effects may be amplified in the presence of a polyelectrolyte. Regardless of the theoretical approach to the polyelectrolyte case, electrostatic considerations predict that: (i) there will be a gradient in the concentration of counterion extending radially from the surface of the polyelectrolyte, considered to be an infinitely long charged cylinder; (ii) the local concentration of counterion may be high at the polyelectrolyte surface (in excess of 1 M for a highly charged polyion), even when the total concentration of counterion in the solution is low; and (Mi) the outer boundary of the region of high counterion concentration is somewhat arbitrary and depends on ionic strength but is of the order of 10 A from the polyion surface. Ions that are close to the polyelectrolyte are often called bound ions. Manning (5) provided a useful and clear distinction between bound species; he describes those ions that retain a full hydration sphere when associated with the polyion as "territorially bound" and describes those ions that lose one or more first coordination sphere water molecules in the interaction with the polyelectrolyte as "site bound." For divalent ions interacting with a polyelectrolyte like DNA, which has a low surface charge density but a high axial charge density, Manning states (5) that ion association should be almost exclusively territorial in spite of the fact that equilibrium constants for magnesium ions with phosphate moieties are significant, frequently as large as 100 M-1 (6).Experimental distinction between territorially bound and EXPERIMENTAL 25Mg NMR spectra were accumul...

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“…4. Only the line widths measured at three-fourths of the peak height have a temperature dependence consistent with that reported by Reimarsson et al (11). The line widths shown in Fig.…”

Section: Resultssupporting

confidence: 90%

²⁵ Mg NMR in DNA solutions: Dominance of site binding effects

Rose

Bleam

Record

et al. 1980

Proc. Natl. Acad. Sci. U.S.A.

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“…In contrast, Mg 2+ were binding to specific sites, then dehydration and significant rotational immobilization would be anticipated. The observed NMR behavior is quite similar to that found for the binding of Mg 2+ and other multivalent cations to duplex DNA (14,23,(27)(28)(29)(30).…”

Section: Discussionsupporting

confidence: 76%

The Polyelectrolyte Behavior of Actin Filaments: A ²⁵Mg NMR Study

et al. 1999

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Under physiological conditions, filamentous actin (F-actin) is a polyanionic protein filament. Key features of the behavior of F-actin are shared with other well-characterized polyelectrolytes, in particular, duplex DNA. For example, the bundle formation of F-actin by polyvalent cations, including divalent metal ions such as Mg2+, has been proposed to be a natural consequence of the polyelectrolyte nature of actin filaments [Tang and Janmey (1996) J. Biol. Chem. 271, 8556-8563]. This recently proposed model also suggests that weak interactions between F-actin and Mg2+ ions reflect a nonspecific trapping of counterions in the electric field surrounding F-actin due to its polyelectrolyte nature. To test this hypothesis, we have performed 25Mg NMR measurements in F-actin solutions. Based on the NMR data, we estimate that the rotational correlation times of Mg2+ are independent of the overall rotational dynamics of the actin filaments. Moreover, competitive binding experiments demonstrate a facile displacement of F-actin-bound Mg2+ by Co(NH3)63+. At higher Co(NH3)63+ concentrations, a fraction of the magnesium ions are trapped as actin filaments aggregate. ATP also competes effectively with actin filaments for binding to Mg2+. These results support the hypothesis that magnesium ions bind loosely and nonspecifically to actin filaments, and thus show a behavior typical of counterions in polyelectrolyte solutions. The observed features mimic to some extent the well-documented behavior of counterions in DNA solutions.

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“…These studies indicate that Mg2+ probably binds specific sites on ribosomal subunits (Grunberg-Manago, 1979). Mg2+ had been shown to bind DNA territorially (Reimarsson et al, 1979), and these data had been the basis for predictions concerning the electrostatic theory. However, Rose et al (1980) have now shown that a significant percentage of Mg2+ actually binds specific sites on DNA.…”

Section: Discussionmentioning

confidence: 98%

Influence of various cations on the equilibriums between wheat germ ribosomes and their subunits

Sperrazza¹,

Moore²,

Spremulli³

1981

Biochemistry

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The influence of alkaline earth metal ions, alkali metal ions, ammonium ions, and polyamines upon the equilibria between high-salt-washed wheat germ ribosomes and their subunits was investigated by light scattering. The Mgz+-dependent, reversible association of ribosomal subunits was studied with buffers containing 100 mM concentrations of the chloride salts of various monovalent cations. These studies indicate that K+ and Na+ are most effective in dissociating the ribosomes into subunits, followed by Rb+ and then NH4+. The dissociation curves determined with buffers containing K+, Na', Rb', and NH4+ ions exhibit [Mg"] 1/2 values of 1.4, 1.4, 1.2, and 0.7 mM, respectively. The divalent cations, in general, strongly promote subunit association but differ in their abilities to do so. Ca2+ associates the ribosomal subunits more effectively than Sr2+, which is more effective than Mgz+. In the presence of 100 mM KCl and 0.15 mM MgClz, Ca2+-, Sr2+-, and Mgz+-dependent association curvesx e subunits of both eucaryotic and procaryotic ribosomes are capable of reversible association and dissociation. The types and concentrations of various cations present play a major role in determining the position of the equilibrium between the intact ribosome and its subunits. Kinetic, thermodynamic, and ion-specificity studies have been performed with Escherichia coli ribosomes in an effort to explain the roles of MgZ+, K+, and polyamines in the association of the subunits. Conflicting mechanisms have been proposed as a result of these studies. One model suggests that Mgz+ binds to specific sites on the subunits and thereby promotes subunit association (Petermann, 1964;Goldberg, 1966). This model is supported by the data of Zitomer & Flab (1972), who found that MgZ+, Ca2+, and polyamines promote ribosomal subunit association while K+ promotes subunit dissociation. Ca2+, however, was less effective than Mg2+ in promoting subunit association, suggesting that the ions were acting at specific sites. In contrast, the electrostatic model suggests that Mg2+ neutralizes the charged groups on the ribosomal subunits. This reduction in the electrostatic repulsion between the subunits would allow association. The studies of Walters & Van Os (1970, 1971) on yeast ribosomes and Wishnia & Boussert (1977) on E . coli ribosomes support the electrostatic model. Calculations by these groups also showed that the reduction of the electrostatic repulsion by Mg2+ theoretically is sufficient to promote subunit association. Nieuwenhuysen et al. (1980), using Artemia salina ribosomes, have shown that the molar volume changes produced by ribosomal subunit association are similar to those observed with E. coli type A ribosomes. Furthermore, they have suggested that this large volume change is consistent with two From the exhibit [M2+lIl2 values of 0.9, 1.1, and 1.4 mM, respectively. The abilities of the polyamines to associate ribosomal subunits in buffers containing 100 mM KCl and 0.20 mM MgClz were investigated. Both spermine ( [~p m ]~/~ = 0.09 mM) and sp...

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Counterion NMR in polyelectrolyte solutions

Cited by 35 publications

References 13 publications

²⁵ Mg NMR in DNA solutions: Dominance of site binding effects

²⁵ Mg NMR in DNA solutions: Dominance of site binding effects

The Polyelectrolyte Behavior of Actin Filaments: A ²⁵Mg NMR Study

Influence of various cations on the equilibriums between wheat germ ribosomes and their subunits

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Counterion NMR in polyelectrolyte solutions

Cited by 35 publications

References 13 publications

25 Mg NMR in DNA solutions: Dominance of site binding effects

25 Mg NMR in DNA solutions: Dominance of site binding effects

The Polyelectrolyte Behavior of Actin Filaments: A 25Mg NMR Study

Influence of various cations on the equilibriums between wheat germ ribosomes and their subunits

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²⁵ Mg NMR in DNA solutions: Dominance of site binding effects

²⁵ Mg NMR in DNA solutions: Dominance of site binding effects

The Polyelectrolyte Behavior of Actin Filaments: A ²⁵Mg NMR Study