Solution nonideality related to solute molecular characteristics of amino acids

Keener, C; Fullerton, Gary D.; Cameron, Ivan L.; Xiong, Jinhu

doi:10.1016/s0006-3495(95)80187-6

Cited by 42 publications

(6 citation statements)

References 39 publications

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“…The large and positive heat capacity change is normally attributed to the extra heat needed to "melt" the ordered water structure near hydrophobic groups exposed to water. As a second example, departures from ideality in the observed freezing-point depression of aqueous solutions of amino acids support the picture that there are significant structural changes within the hydration shell of amino acid side chains (5). Once again, the observed effect (in this case, nonideality) is a linear function of the exposed surface area.…”

mentioning

confidence: 52%

Direct evidence for modified solvent structure within the hydration shell of a hydrophobic amino acid.

Pertsemlidis

Saxena

Soper

et al. 1996

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

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Neutron scattering experiments are used to determine scattering profiles for aqueous solutions of hydrophobic and hydrophilic amino acid analogs. Solutions of hydrophobic solutes show a shift in the main diffraction peak to smaller angle as compared with pure water, whereas solutions of hydrophilic solutes do not. The same difference for solutions of hydrophobic and hydrophilic side chains is also predicted by molecular dynamics simulations. The neutron scattering curves of aqueous solutions of hydrophobic amino acids at room temperature are qualitatively similar to differences between the liquid molecular structure functions measured for ambient and supercooled water. The nonpolar solute-induced expansion of water structure reported here is also complementary to recent neutron experiments where compression of aqueous solvent structure has been observed at high salt concentration.Interest in the structural organization of the solvent within the hydration shell of amino acid side chains arises partly from questions related to the thermodynamic and structural explanations of the hydrophobic interaction between nonpolar side chains. Much thermodynamic evidence is conventionally interpreted as indicating a differently organized structure of the water that is in contact with a nonpolar solute as compared with the pure liquid (1, 2). As one example, there is a significant increase in heat capacity when proteins are unfolded or when hydrophobic compounds are dissolved in water, and this change in heat capacity is a linear function of the area of the hydrophobic surfaces (3, 4). The large and positive heat capacity change is normally attributed to the extra heat needed to "melt" the ordered water structure near hydrophobic groups exposed to water. As a second example, departures from ideality in the observed freezing-point depression of aqueous solutions of amino acids support the picture that there are significant structural changes within the hydration shell of amino acid side chains (5). Once again, the observed effect (in this case, nonideality) is a linear function of the exposed surface area.The relationship between water structure and the hydrophobic effect has also been the subject of a number of theoretical studies (6, 7) and computer simulations (8-13) on a number of model side chain solutes. Structural analyses of the simulation data indicate that water retains its hydrogenbonded network by "straddling" the surface of the nonpolar group with three of its four tetrahedral hydrogen bonds, with the fourth bond pointing away from the hydrophobic surface. Neutron scattering experiments have provided confirmation of this view, where water molecules are observed to lie roughly tangential to the surface of the nonpolar solute (14, 15). Further experimental evidence for a hydrogen-bonded hydration shell around hydrophobic groups is found in the x-ray crystal structures of clathrate compounds (16). In these solid, crystalline hydrates, water molecules are organized completely into hydrogen-bonded polygons that ...

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mentioning

confidence: 52%

Direct evidence for modified solvent structure within the hydration shell of a hydrophobic amino acid.

Pertsemlidis

Saxena

Soper

et al. 1996

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

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“…This was believed to be due to the structural perturbations of water molecules adjacent to aspartic acid in the CS of aspartic acid. 40 Obviously, the liquid structure of the CS of aspartic acid remained intact and different from the one of the RCS of aspartic acid after a 10 min incubation at 25 °C. However, this was not the case at all for the alanine system.…”

Section: Resultsmentioning

confidence: 92%

The Origin of Life and the Crystallization of Aspartic Acid in Water

Lee

Lin

2010

Crystal Growth & Design

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The unusual molecular complexation of the enantiomers of aspartic acid in water was discovered and proven by a solubility test, solution freezing point, crystallization kinetics, and the incubation time change. The transformation of a "conglomerate solution" (CS) to a "racemic compound solution" (RCS) was dependent on both temperature and time. The CS was the solution phase which produced conglomerate crystals, and the RCS was the solution phase which gave a racemic compound. Fourier transformed infrared spectroscopy and powder X-ray diffraction were used to characterize aspartic acid solids crystallized from those complex solution phases and to distinguish conglomerate crystals from a racemic compound. We found that it took more than 36 h at 25 °C and 5 h at 45 °C just to complete the solution phase transformation of the CS of aspartic acid to the RCS of aspartic acid. However, the presence of an equimolar of succinic acid could hinder the solution phase transformation of the CS of aspartic acid to the RCS of aspartic acid for up to at least 8 h at 60 °C. This leeway of hours had provided an opportunity for the thermodynamically stable racemic aspartic acid to convert into the metastable conglomerate in water first by either a rapid acid-base reaction or the addition of an antisolvent with the temperature drop, without being concerned by its back conversion later to a racemic compound thermodynamically for quite some time. As a result, enantioseparation of aspartic acid by preferential crystallization in a large scale would have been very common and easy to occur on the primitive earth.

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“…During active shortening, cross-bridge interactions translate the thin filaments towards the M-line, decreasing elastic energy storage in PEVK, but also rotate the thin filaments, increasing energy storage. Owing to the dependence of cross-bridge force, duty factor and step size on shortening velocity [64,65], PEVK would increasingly unwind from the thin filaments as the cross-bridge force declines with shortening velocity. In fact, without such unwinding, the amplitude of muscle shortening will be limited unrealistically by the bound PEVK.…”

Section: Titin Winding During Active Shorteningmentioning

confidence: 99%

Is titin a ‘winding filament’? A new twist on muscle contraction

et al. 2011

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Recent studies have demonstrated a role for the elastic protein titin in active muscle, but the mechanisms by which titin plays this role remain to be elucidated. In active muscle, Ca 2þ -binding has been shown to increase titin stiffness, but the observed increase is too small to explain the increased stiffness of parallel elastic elements upon muscle activation. We propose a 'winding filament' mechanism for titin's role in active muscle. First, we hypothesize that Ca 2þ -dependent binding of titin's N2A region to thin filaments increases titin stiffness by preventing low-force straightening of proximal immunoglobulin domains that occurs during passive stretch. This mechanism explains the difference in length dependence of force between skeletal myofibrils and cardiac myocytes. Second, we hypothesize that cross-bridges serve not only as motors that pull thin filaments towards the M-line, but also as rotors that wind titin on the thin filaments, storing elastic potential energy in PEVK during force development and active stretch. Energy stored during force development can be recovered during active shortening. The winding filament hypothesis accounts for force enhancement during stretch and force depression during shortening, and provides testable predictions that will encourage new directions for research on mechanisms of muscle contraction.

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Solution nonideality related to solute molecular characteristics of amino acids

Cited by 42 publications

References 39 publications

Direct evidence for modified solvent structure within the hydration shell of a hydrophobic amino acid.

Direct evidence for modified solvent structure within the hydration shell of a hydrophobic amino acid.

The Origin of Life and the Crystallization of Aspartic Acid in Water

Is titin a ‘winding filament’? A new twist on muscle contraction

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