Volume effects in aqueous solutions of macromolecules containing non‐polar groups

Bøje, Lars; Hvidt, Aase

doi:10.1002/bip.1972.360111114

Cited by 42 publications

(17 citation statements)

References 10 publications

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“…Others, however, have pointed out that the local concentration of side chains in an unfolded polypeptide is sufficiently high that deviations from ideal thermodynamic behavior would be expected to occur (9)(10)(11). In support of this, we note that some of the nonideal behavior may arise from the failure of water to gain access to the entire denatured macromolecular surface.…”

supporting

confidence: 69%

Volume changes of globular protein association

Kahn¹,

Schwanwede²,

Ippolito³

et al. 1980

Biophysical Journal

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Water is generally absent from the interior of globular proteins and from intersubunit interfaces (1). The folding and assembly of proteins is, therefore, often represented as a transfer of matter from an aqueous to a less polar milieu. As Kauzmann observed many years ago (2), the volume changes of transfer of small organic molecules lead to the expectation that denaturation, which exposes previously buried side chains to solvent, would occur with a large decrease in volume. Measurements from several laboratories of pressure-induced denaturation reactions have shown that, while the volume changes are negative, they are unexpectedly small (3-6; for a review, see reference 7). As a result, the applicability of model compound transfer data to macromolecular reactions has been questioned, as has the role of hydrophobic properties in stabilizing protein structure (4, 8).Others, however, have pointed out that the local concentration of side chains in an unfolded polypeptide is sufficiently high that deviations from ideal thermodynamic behavior would be expected to occur (9-11). In support of this, we note that some of the nonideal behavior may arise from the failure of water to gain access to the entire denatured macromolecular surface.That nonideal behavior is, in fact, implicated is suggested by data on globular protein polymerization. Proteins which polymerize under dilute, relatively ideal thermodynamic conditions yield volume changes comparable to or greater than those of denaturation (12-14). Deoxygenated sickle cell hemoglobin solutions, in contrast, are well known to be nonideal, and their polymerization gives no measurable volume change.' It appears, therefore, that the denaturation experiments give a misleading impression of the volumetric properties of aqueous protein solutions.To obtain a better understanding of solvent-protein interactions, we are measuring directly the volume changes of association or dissociation of globular subunits. We use proteins whose three-dimensional structures are known. The absence of significant conformational change upon association or dissociation can be proven as well. The volumetric properties can then be correlated with the detailed nature of the molecular surface that is withdrawn from contact with water. The problems that make the denaturation data difficult to interpret thus do not occur, for the solutions are dilute with respect to the relevant reacting species, which are subunits and not side chains, and the nature of the relevant molecular surface is known.We report here work on the acid-induced dissociation of human methemoglobin (met-Hb) from its normal tetrameric structure to a ,B dimers, as well as measurements on the association of bovine trypsin with bovine pancreatic trypsin inhibitor (PlTI).Volume changes were measured in Carlsberg dilatometers (15, 16) at 20.0 ± 0.001 C. Experiments with trypsin were done in 0.1 M acetate buffer, pH 5.0, to avoid autolysis. For the association of purified ,B trypsin with PTI the uncorrected volume change is + 80 ml/mol. This...

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supporting

confidence: 69%

Volume changes of globular protein association

Kahn¹,

Schwanwede²,

Ippolito³

et al. 1980

Biophysical Journal

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“…A possible explanation for this contradiction might be given if the local concentration of nonpolar groups exposed is quite high in protein systems and the volume change for the rupture of hydrophobic bonds is partly positive (Boje & Hvidt, 1972;Gekko & Noguchi, 1979). In fact, the volume changes for the transfer of water into organic solvents are known to be positive (Masterton & Seiler, 1968), although the transfer of nonpolar groups into water produces negative volume changes (Kauzmann, 1959).…”

Section: ( 5 )mentioning

confidence: 91%

Compactness of thermally and chemically denatured ribonuclease A as revealed by volume and compressibility

Tamura¹,

Gekko²

1995

Biochemistry

118

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The conformational changes of ribonuclease A due to thermal and guanidine hydrochloride denaturation were monitored by means of precise density and sound velocity measurements. It was found that the apparent molar volume decreased but the adiabatic compressibility increased on thermal denaturation under acidic conditions (pHs 1.60, 1.90, and 2.08). On the other hand, guanidine hydrochloride denaturation (pH 2.00) brought about large decreases in the compressibility and apparent molar volume. These results indicate that the conformation of the denatured protein is greatly different between the two types of denaturation: the thermally denatured state corresponds to the structure with enhanced thermal fluctuation having a residual secondary structure and a high local concentration of nonpolar groups exposed, but the guanidine hydrochloride denaturation leads to exposure of a large amount of amino acid residues, resulting in an increase in hydration and a decrease in the internal cavity. The compressibility changes due to both types of denaturation were not correlated to a loss of the secondary structure, as judged by means of circular dichroism. These findings suggest that the compactness and thermal fluctuation of the protein cannot be described by a two-state denaturation model and that there are some molten-globule-like intermediates in the denaturation processes.

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“…Studies of protein stability by means of various spectroscopic techniques have shown that increasing pressure reduces the partial volume of the molecule through compression and conformational changes. Although matter is always compressible, electrostriction of charged and polar side chains, hydrophobic hydration, hydrogen bonds stabilization and the elimination of packing defects are considered to be the main causes for this volume change [9][10][11][12][13][14][15].The effects of pressure on hemeproteins have been the subject of numerous investigations. Optical absorption [16][17][18][19][20][21], fluorescence [22], FTIR [23-25], Raman [26], and NMR [27-29] spectroscopies, and laser flash photolysis [30-32] have all shown that pressures near 300 MPa leads to subtle local rearrangements of the protein structure and that some intermediate states preceding unfolding probably appear.Therefore, it is important to determine whether the modifications observed at the level of the active site of myoglobin [17,18,20,21,[26][27][28][29] and the reorganization of the secondary structure with an alteration of the electrostatic and hydrogen-bond array [23,24] are related to a change in the tertiary structure of the protein.In order to reply these questions we report here for the first time, the results of small-angle neutron scattering (SANS) experiments performed on myoglobin (Mb) under pressure.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

High‐pressure effects on horse heart metmyoglobin studied by small‐angle neutron scattering

Loupiac

Bonetti

et al. 2002

European Journal of Biochemistry

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Small-angle neutron scattering experiments were performed on horse azidometmyoglobin (MbN 3 ) at pressures up to 300 MPa. Other spectroscopic techniques have shown that a reorganization of the secondary structure and of the active site occur in this pressure range. The present measurements, performed using various concentrations of MbN 3 , show that the compactness of the protein is not altered as the value of its radius of gyration remains constant up to 300 MPa. The value of the second virial coefficient of the protein solution indicates that the interactions between the molecules are always strongly repulsive even if their magnitude decreases with increasing pressure. Taking advantage of the pressureinduced contrast variation, these experiments allow the partial specific volume of MbN 3 to be determined as a function of pressure. Its value decreases by 5.4% between atmospheric pressure and 300 MPa. In this pressure range the isothermal compressibility of hydrated MbN 3 is found to be almost constant. Its value is (1.6 ± 0.1) 10 )4 MPa )1.Keywords: myoglobin; pressure; SANS; partial volume; compressibility.The structure of proteins and their solvent interactions can be modified by temperature, pH or chemicals. The application of hydrostatic pressure to a protein solution also provides a manner to alter these physical properties [1][2][3][4]. Therefore, it is important to determine whether the modifications observed at the level of the active site of myoglobin [17,18,20,21,[26][27][28][29] and the reorganization of the secondary structure with an alteration of the electrostatic and hydrogen-bond array [23,24] are related to a change in the tertiary structure of the protein.In order to reply these questions we report here for the first time, the results of small-angle neutron scattering (SANS) experiments performed on myoglobin (Mb) under pressure. Quite generally, SANS can provide information about the partial volume of proteins, their interactions, their size and their conformation [33]. The scattering measurements were carried out in heavy water ( 2 H 2 O) at varying pressures up to 300 MPa as a function of protein concentration in order to determine the magnitude of the solute interactions and to allow for the elimination of their contribution to the forward scattered intensity and the apparent radius of gyration.Azidometmyoglobin (MbN 3 ) has a high stability. It was chosen for this study in order to avoid a mixture of aquo and hydroxy derivatives in metmyoglobin solutions or a contamination of either oxygen or carbon monoxide saturated myoglobin solutions by oxidized forms which could form under pressure [34].

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Volume effects in aqueous solutions of macromolecules containing non‐polar groups

Cited by 42 publications

References 10 publications

Volume changes of globular protein association

Volume changes of globular protein association

Compactness of thermally and chemically denatured ribonuclease A as revealed by volume and compressibility

High‐pressure effects on horse heart metmyoglobin studied by small‐angle neutron scattering

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