Electrostatic forces in muscle and cylindrical gel systems

Millman, B. M.; Nickel, B. G.

doi:10.1016/s0006-3495(80)84915-0

Cited by 69 publications

(69 citation statements)

References 17 publications

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“…Fibre width declines slightly between pH 7.5 and 6.0, and more steeply below 6.0. This decrease is consistent with other observations of fibre diameter (Maughan & Godt, 1980) and lattice spacing (Rome, 1968;Matsubara & Elliott, 1972), and implies that myofilament charge is involved in determining myofilament lattice spacing (Millman & Nickel, 1980).…”

Section: Forcesupporting

confidence: 92%

Length and myofilament spacing-dependent changes in calcium sensitivity of skeletal fibres: effects of pH and ionic strength

Martyn

Gordon

1988

J Muscle Res Cell Motil

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The calcium sensitivity of force was measured in glycerinated rabbit psoas fibres at sarcomere lengths (SL) from 2.3 to 3.4 micron. Increased SL caused calcium sensitivity to increase and the slope of force-calcium relations to decrease. We have hypothesized that length-dependent changes in myofilament lattice spacing and the presence of fixed charge on the myofilaments are important in determining calcium sensitivity. Lattice spacing changes were monitored by measuring fibre diameter (D). D was decreased by increasing SL, decreasing bathing solution pH and by osmotic compression with 3% PVP. 3% PVP caused D to decrease by about 15% at all SLs and pH values tested. Force-calcium relations were measured at different SLs and pH values, with and without 3% PVP in the bathing solutions. At all pH values D at SL 2.3 micron with 3% PVP was comparable to the value at 3.4 micron, without PVP. At pH 7.5 and 7.0 calcium sensitivity was about the same at both SL, although the slope of the force-calcium relation was less at longer SL. The similarity of the calcium sensitivity at the same D, but much different SL, indicates that lattice spacing is important in determining calcium sensitivity, while SL and the degree of myofilament overlap are important in determining the slope of force-calcium relations. In order to test for the role of myofilament charge in determining calcium sensitivity, pH and ionic strength were varied. Decreasing pH caused decreased maximum force and calcium sensitivity. In addition, the influence of SL on calcium sensitivity decreased as pH was lowered, with minimal SL dependence at pH 5.5; even though lattice spacing still decreased with increasing SL. When D was decreased with PVP, calcium sensitivity increased at all SLs in pH 7.5 and 7.0 while the same lattice spacing changes at pH 6.0 and 5.5 resulted in greatly reduced shifts in calcium sensitivity. These results indicate that the effect of lattice spacing on calcium sensitivity depends on myofilament charge. At pH 6.0, even though osmotic compression of the lattice has no effect, increasing SL causes about half the shift in calcium sensitivity seen at pH 7.0. Lowering ionic strength from 200 to 110 mM caused an increase in both the magnitude and length dependence of calcium sensitivity at pH 7.0, while at pH 5.5 both decreased.(ABSTRACT TRUNCATED AT 400 WORDS)

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Section: Forcesupporting

confidence: 92%

Length and myofilament spacing-dependent changes in calcium sensitivity of skeletal fibres: effects of pH and ionic strength

Martyn

Gordon

1988

J Muscle Res Cell Motil

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“…X-ray diffraction shows that the condensed DNA is packed into a lattice with well-defined interaxial spacings that decrease with increasing concentration of added polymer (19). The phenomenon is analogous to the immersion of phospholipid bilayers in dextran solutions used by LeNeveu et al (1,2) to measure interbilayer forces and by Millman and Nickel (20) to measure forces between muscle filaments or tobacco mosaic virus particles. Here, as in those systems, under conditions in which PEG is excluded from the DNA lattice, the osmotic pressure of the polymer solution is the osmotic stress compressing the lattice.…”

Section: Methodsmentioning

confidence: 84%

“…Osmotic pressures of PEG 6 and PVP 40 solutions were determined by equilibrium dialysis against PEG 20 A. Zimmerman and Pheiffer (23) and Maniatis et al (19) showed that such DNA samples remain in the B conformation throughout. The diameter of a DNA double helix in this conformation is =20 A.…”

mentioning

confidence: 99%

Measurement of the repulsive force between polyelectrolyte molecules in ionic solution: hydration forces between parallel DNA double helices.

Rau¹,

Lee²,

Parsegian³

1984

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

402

448

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We have measured the repulsive force between B-form double helices in parallel packed arrays of polymer-condensed DNA in the presence of 0.005-1.0 M ionic solu-tions. Molecular repulsion is consistently exponential with a 2.5-3.5 A decay distance, when the separation between DNA surfaces is 5-15 A. Only weakly dependent on ionic strength and independent of molecular size, this intermolecular repulsion does not obey the predictions of electrostatic double-layer theory. Rather, it strongly resembles the "hydration force" first recognized and quantified between phospholipid bilayers. Only beyond 15 A separation between molecules is there evidence of electrostatic double-layer forces. The quantitative failure of electrostatic double-layer theory seen here must gravely affect accepted analyses of other polyelectrolyte systems. Because the packing of condensed DNA resembles the spacings of DNA in many bacteriophages, our results permit estimation of the "DNA pressure" in phage heads.In 1976, LeNeveu et al. (1) reported that electrically neutral phospholipid bilayer membranes in pure water exerted a mutual repulsion that decayed exponentially with separation and was detectable to separations between parallel membrane surfaces of "30 A. This repulsion was termed a "hydration force" (2) to represent the idea that it is due to the work of removing water from the vicinity of the membrane surface. Further measurements (3-9) on a variety of charged or neutral membranes revealed the existence of hydration forces in pure water or in ionic solutions. For separations of less than 20-30 A between charged membranes, these forces completely overshadow electrostatic repulsion. A qualitatively similar story has emerged from the forces measured between mica sheets in ionic solution, which show an "additional" exponentially decaying component unexpected from electrostatic double layer theory (10-13). Marcelja and coworkers (14-17) have proposed a simple but elegant theory that shows how an exponential force can arise from the spatially varying perturbation of water near a polarizing surface.We now report that similar hydration forces occur between DNA polyelectrolyte molecules. We have measured the force per unit length vs. interaxial separation of parallel DNA double helices under various ionic conditions. The strong repulsive force is detectable when the interaxial distance is about 35 A, at which point the shortest distance between DNA surfaces is ""15 A. This force between molecules grows exponentially with a 2.5-3.5 A characteristic distance as the molecules are brought together. Contrary to expectation from double-layer theory, this repulsion is insensitive to ionic strength and is of a different magnitude than predicted from electrostatic theory.We argue that hydration forces are a major factor in the interaction of particles undergoing molecular assembly. In particular, the packing of DNA in cells and in viruses must be accomplished in a way that circumvents or overcomes the effects of hydration.More generally, the domi...

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“…Theories that relate macro molecular interactions to the underlying composition have been formulated [1,2] and tested for different macromolecular as semblies including muscle [3], virus [4], lipid bilayer [5] and biological membranes [6,7], In applying this theory to the myelin sheath, we found that the protein composition and disposition are significant determinants of the electrostatic effects between membrane surfaces and the equilibrium separation be tween them [8,9]. While there is general con sensus that myelin basic protein (MBP) is localized to the cytoplasmic side of the mem branes in central nervous system (CNS) and peripheral nervous system myelins, the orientation of the major integral membrane protein of CNS myelin, proteolipid protein (PLP), has not yet been determined.…”

Section: Introductionmentioning

confidence: 99%

Orientation of Proteolipid Protein in Myelin: Comparison of Models with X-Ray Diffraction Measurements

Inouye

Kirschner²

1989

Dev Neurosci

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Three models have been proposed for the arrangement of proteolipid protein (PLP) in the myelin membrane. We have tested these models by determining to what extent each is consistent with the membrane-membrane interactions and electron density profile of central nervous system myelin obtained from X-ray diffraction. Equilibrium periods and membrane separations were calculated from the proposed organization of lipids and proteins in the membrane, and compared with values obtained experimentally as a function of pH and ionic strength. The orientation of the proteins was also used to calculate electron density levels in the cytoplasmic and extracellular spaces. We found that the Stoffel and Hudson models for PLP were more consistent than the Laursen model with the range of pH over which the intermembrane separation at the extracellular apposition is a minimum. The Hudson model also fits better the swollen periods observed at alkaline pH. The Hudson PLP model has many more residues in the extracellular side of the membrane than does either of the other models, resulting in higher electron density in the extracellular space compared to the cytoplasmic space. Such an asymmetric distribution of electron density is offset by the electron density of myelin basic protein which is localized in the cytoplasmic space. The resulting similar levels of electron density at the two appositions are like those in profiles calculated from the X-ray data.

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Electrostatic forces in muscle and cylindrical gel systems

Cited by 69 publications

References 17 publications

Length and myofilament spacing-dependent changes in calcium sensitivity of skeletal fibres: effects of pH and ionic strength

Length and myofilament spacing-dependent changes in calcium sensitivity of skeletal fibres: effects of pH and ionic strength

Measurement of the repulsive force between polyelectrolyte molecules in ionic solution: hydration forces between parallel DNA double helices.

Orientation of Proteolipid Protein in Myelin: Comparison of Models with X-Ray Diffraction Measurements

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