Structure and interparticle interactions of bovine serum albumin in solution studied by small-angle neutron scattering

Bendedouch, Dalila; Chen, Sow Hsin

doi:10.1021/j100232a003

Cited by 118 publications

(102 citation statements)

References 2 publications

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“…However, BSA has the same molecular weight as Human Serum Albumin (HSA) and 76% sequence identity [21]. The structure of the latter, available on the Protein Data Bank website (http://www.rcsb.org/pdb/) under the identifier 1AO6, allows us to calculate its radius of gyration as equal to R g = 27Å, in very good agreement with measurements on BSA solutions by small angle scattering [22,23]. In most cases once adsorbed on solid, globular proteins are partly denatured, however they still keep a compact and globular conformation [2].…”

Section: Thickness Of the Protein Layermentioning

confidence: 88%

Slow and remanent electric polarization of adsorbed BSA layer evidenced by neutron reflection

et al. 2012

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Using neutron reflectivity together with an appropriate electrochemical cell, we have studied the effects of transverse electric field on the Bovine Serum Albumin (BSA) monolayer initially adsorbed at the interface of the aqueous solution and a conductive doped-silicon wafer. Depending on the sign of the initial potential, a second layer is adsorbed or not on top of the first whereas a subsequent reversal of potential has no effect. We show that this behaviour reveals the slow and remanent electric polarization of the first BSA layer. Based on the permanent dipolar structure of BSA, we suggest an analogy with dipolar glasses that may account for the slowness and memory of the process. PACS numbers:Protein adsorption on solid surfaces is a fundamental phenomenon that plays a central role in biotechnology; e.g.for biomaterials and biocompatibility improvement [1]. Proteins are polyampholytes (i.e. carry both positive and negative charges) and amphiphiles (i.e. carry both hydrophilic and hydrophobic parts) and these features make the thermodynamics of their interactions with a surface particularly rich and extensively studied [2]. Studies of the dynamics of adsorbed proteins mainly focus on adsorption kinetics that may take place in a few tens of minutes[3] but sometime is much slower, history dependent and displays some irreversible features [4,5]. In these latter cases, the slow dynamics is viewed as inherent to the random addition of new molecules onto the surface and described in terms of the Random Sequential Adsorption (RSA) model[6] that displays slow dynamics typical of glass or jamming transition. The counterpart of this jammed behaviour is the slow relaxation of the in-plane density of the adsorbed layer after an external perturbation or spontaneous fluctuations [7]. Much less studied and also presumably quite different are external perturbations that retain the density constant but should in principle operate on the orientation of adsorbed molecules, although this handling of adsorbed layer has many practical significances, e.g. for immobilized enzymes, immunoassays and biosensors. Due to the electrical charges of proteins, electrical stimuli are the most obvious with respect to this orientation. But studies in this direction are still sparse [8][9][10][11] and only concerned up to now with ellipsometry or electrochemical measurements, which produce ambiguous results due to technical limitations [12].In this paper, we report a neutron reflectivity study on the effects of transverse electric field on a Bovine Serum Albumin (BSA) monolayer initially adsorbed at silicon/water interface. Our results show a slow and remanent polarization of this layer revealed by the formation of a second layer on top of the first. Based on the BSA structure that displays a permanent electric dipole [13], these features suggest an analogy with spin glasses that has not been considered until now. SAMPLES AND EXPERIMENTAL DEVICEBSA (Sigma-Aldrich) was diluted at a concentration of 1 mg/ml in heavy water (99.90 % 2 H, Euriso-top...

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Section: Thickness Of the Protein Layermentioning

confidence: 88%

Slow and remanent electric polarization of adsorbed BSA layer evidenced by neutron reflection

et al. 2012

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“…As observed in a series of small-angle neutron scattering (SANS) measurements of bovine serum albumin (82,83), 1100 water molecules (corresponding to 0.3-0.4 g H 2 O/g albumin) are considered to ''bound'' around a protein molecule, forming a higher density water layer. Given that a complete hydration monolayer around albumin would contain 1070 water molecules (84), the SANS result represents a single hydration shell around albumin and the existence of further hydration layers was not checked for.…”

Section: Hydration Statementioning

confidence: 99%

Hydrogen Bond Network of Water around Protein Investigated with Terahertz and Infrared Spectroscopy

Shiraga

Ogawa

Kondo

2016

Biophysical Journal

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The dynamical and structural properties of water at protein interfaces were characterized on the basis of the broadband complex dielectric constant (0.25 to 400 THz) of albumin aqueous solutions. Our analysis of the dielectric responses between 0.25 and 12 THz first revealed hydration water with retarded reorientational dynamics extending~8.5 Å (corresponding to three to four layers) out from the albumin surface. Second, the number of nonhydrogen-bonded water was decreased in the presence of the albumin solute, indicating protein inhibits the fragmentation of the water hydrogen-bond network. Finally, water molecules at the albumin interface were found to form a distorted hydrogen-bond structure due to topological and energetic disorder of the protein surface. In addition, the intramolecular O-H stretching vibration of water (~100 THz), which is sensitive to hydrogen-bond environment, pointed to a trend that hydration water has a larger population of strongly hydrogen-bonded water molecules compared with that of bulk water. From these experimental results, we concluded that the ''strengthened'' water hydrogen bonds at the protein interface dynamically slow down the reorientational motion of water and form the less-defective hydrogen-bond network by inhibiting the fragmentation of water-water hydrogen bonds. Nevertheless, such a strengthened water hydrogen-bond network is composed of heterogeneous hydrogen-bond distances and angles, and thus characterized as structurally ''distorted.''

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“…Thus, we investigated the possibility of micelle formation, either free or bound to the protein, by using a D 2 O/H 2 O ratio of 40:60, the contrast matching point of BSA (38). Despite the fact that the neutron-scattering length density difference between azoTAB and this solvent mixture is relatively high (particularly from the alkyl spacer groups), no excess scattering over the solvent was detected under visible light for either pure BSA or BSA-azoTAB mixtures up to 20 mM surfactant, indicating that micelles are not formed.…”

Section: Bsa Conformation Changes With Light (Sans)mentioning

confidence: 99%

Photocontrol of Protein Folding: The Interaction of Photosensitive Surfactants with Bovine Serum Albumin

2004

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The photoresponsive interaction of light-sensitive azobenzene surfactants with bovine serum albumin (BSA) at neutral pH has been investigated as a means to control protein folding with light irradiation. The cationic azobenzene surfactant undergoes a reversible photoisomerization upon exposure to the appropriate wavelength of light, with the visible-light (trans) form of the surfactant being more hydrophobic than the UV-light (cis) form. As a consequence, the trans form exhibits enhanced interaction with the protein compared to the cis form of the surfactant, allowing photoreversible control of the protein folding/unfolding phenomena. Small-angle neutron-scattering (SANS) measurements are used to provide detailed information on the protein conformation in solution. A fitting of the protein shape to a lowresolution triaxial ellipsoid model indicates that three discrete forms of the protein exist in solution depending on the surfactant concentration, with lengths of approximately 90, 150, and 250 Å, respectively, consistent with additional dynamic light-scattering measurements. In addition, shape-reconstruction methods are applied to the SANS data to obtain relatively high-resolution conformation information. The results confirm that BSA adopts a heart-shaped structure in solution at low surfactant concentration, similar to the well-known X-ray crystallographic structure. At intermediate surfactant concentrations, protein elongation results as a consequence of the C-terminal portion separating from the rest of the molecule. Further increases in the surfactant concentration eventually lead to a highly elongated protein that nonetheless still exhibits some degree of folding that is consistent with the literature observations of a relatively high helical content in denatured BSA. The results clearly demonstrate that the visible-light form of the surfactant causes a greater degree of protein unfolding than the UV-light form, providing a means to control protein folding with light that, within the resolution of SANS, appears to be completely reversible.Protein folding is a remarkable process that affects nearly every aspect of biological function. The conformation of a protein in solution is generally a function of electrostatic, hydrogen-bonding, van der Waals, and hydrophobic interactions among the amino acid residues that all typically favor a folded conformation, overcoming the entropic penalty associated with this folding of the protein into a compact state. For a given amino acid sequence, the protein will often adopt a unique structure in solution, termed the native state, whereby the charged and polar amino acid groups are exterior and exposed to water, while the nonpolar moieties generally reside in the interior of the folded structure, protected from unfavorable solvent interactions. Protein unfolding can be induced by a variety of external conditions such as changes in pH (ionization of nonpolar residues), temperature (complex interplay between enthalpic and entropic effects), and pressure (a conse...

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Structure and interparticle interactions of bovine serum albumin in solution studied by small-angle neutron scattering

Cited by 118 publications

References 2 publications

Slow and remanent electric polarization of adsorbed BSA layer evidenced by neutron reflection

Slow and remanent electric polarization of adsorbed BSA layer evidenced by neutron reflection

Hydrogen Bond Network of Water around Protein Investigated with Terahertz and Infrared Spectroscopy

Photocontrol of Protein Folding: The Interaction of Photosensitive Surfactants with Bovine Serum Albumin

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