Conformational studies of BSA using laser light scattering

Harvey, J.D.; Geddes, Robert; Wills, Peter R.

doi:10.1002/bip.1979.360180912

Cited by 27 publications

(12 citation statements)

References 28 publications

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“…3 support an angle-independent value for Dapp(T 0) as reported (18). The values for Dapp(T -> 0) obtained in the present study are compared with recent reports in the literature (20,(24)(25)(26)(27) Table 2). -, OD.…”

supporting

confidence: 69%

Effect of titration charge on the diffusion of bovine serum albumin.

Schmitz¹,

Lü²

1983

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

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Quasi-elastic light scattering studies were performed on purified bovine serum albumin sample under conditions of high and low ionic strength and pH. Two relaxation modes were observed in all cases. The apparent diffusion coefficient obtained in the asymptotic time window (T) limit T-* 0-i.e., Dapp(T --* 0)-was found to be 6.1 X 10-7 cm2/sec under conditions that minimized electrical forces (100 mM KCI at pH 4.5). As the ionic strength was lowered to 0.1 mM KCI (pH 4.5) or the pH was raised to 10 (100 mM KCI), Dapp(T -*0) increased to 7.2-7.5 X 10-7 cm2/sec. Kirkwood and Shumaker first suggested that fluctuations in the net charge of proteins can fully account for the observed permanent dipole of globular proteins (1) and that these fluctuations may lead to substantial attractive interactions between the polyions (2). Oosawa (3) examined a similar fluctuation mechanism for rigid rods and concluded that attractive forces resulted if coupling occurred between counterion distributions along neighboring rods. It is the current beliefthat fluctuations in the small-ion distribution about a polyion are also responsible for the enhancement of the dielectric constant for linear polyelectrolytes at low frequencies of the external field (4-9). It follows, therefore, that the dynamics of polyions would be greatly affected under conditions that promote large amplitude fluctuations in the small-ion distributions. Lin et aL (10) examined the effect of coupled polyion-small-ion dynamics on the apparent diffusion coefficient, with the result Dapp = (I/2)[Dp(l -fl) + Ds (1 + fl)], [1] where DP is the polyion diffusion coefficient, Ds is the small ion diffusion coefficient, and [4] where the first term is the hydrodynamic dissipation term for a Stokes bead of radius ap, and the second term is referred to as the electrolyte dissipation term, which arises from an asymmetric distribution of small ions about the polyion. The parameters in Eq. 4 are: solvent viscosity (ii), electrolyte dissipation charge (Zedc), electron charge (e), small-ion diffusion coefficient (Dj), Debye-Huckel screening parameter (K), and bulk dielectric constant (E). It has been suggested through use of Eq. 4 that "apparent unfolding" of polyelectrolytes as the ionic strength is lowered below 50 mM actually may be overestimated because of the presence of significant electrolyte dissipation effects (12). We have proposed that small-ion fluctuations play a significant role not only in the self-diffusion coefficient of polyions but also in the stabilization of "localized ordered domains" within the polyelectrolyte solution (13-18). The involvement of small ions was suggested to explain quasi-elastic light-scattering (QLS) experiments performed in the presence of a sinusoidal electric field (QLS-SEF). The apparent electrophoretic mobility and apparent diffusion coefficient for mono-and polynucleosomes showed a dispersion curve in the same frequency range as that of the dielectric constant for low molecular weight DNA. The increased amplitude of the slow...

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supporting

confidence: 69%

Effect of titration charge on the diffusion of bovine serum albumin.

Schmitz¹,

Lü²

1983

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

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“…[25][26][27] The results obtained in those studies show a coexistence of serum albumin monomers (with R H,M ≈ 36 Å) and dimmers (with R H,D ≈ 48 Å). 25,27 According to that information, Figure 2b shows that BSA/PEG 2000 -PE complexes do not contain more than one BSA molecule (the maximum R H for the BSA/PEG 2000 -PE complexes is 48.4 Å, very close to R H,D for a pure BSA dimmer). Figure 2c shows the SLS intensity I(90°) measured in the range ∆ 2 ) 0-2.…”

Section: Resultsmentioning

confidence: 94%

Structural Study of BSA/Poly(ethylene glycol) Lipid Conjugate Complexes

et al. 2007

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In this work we report the structural characteristics of bovine serum albumin/poly(ethylene glycol) lipid conjugate (BSA/PEG(2000)-PE) complexes under physiological conditions (37 degrees C and pH 7.4) for particular fractions of BSA to PEG-lipid concentration, c(BSA)/c(PEG)(2000)-PE. Ultraviolet fluorescence spectroscopy (UV) results shown that PEG(2000)-PE is associated to BSA, leading to protein unfolding for fixed c(BSA) = 0.01 wt % and variable c(PEG)(2000)-PE = 0.0015-0.6 wt %. Tryptophan groups on the BSA surface are in contact with the PEG-lipid at c(PEG)(2000)-PE = 0.0015 wt %, while they are exposed to water at c(PEG)(2000)-PE > 0.0015 wt %. Dynamic and static light scattering (DLS and SLS) and small-angle neutron scattering (SANS) point out the existence of individual BSA/PEG-lipid complexes in the system for fixed c(BSA) = 1 wt % and variable c(PEG)(2000)-PE = 0.15-2 wt %. DLS shows that there is only one BSA molecule per protein/PEG-lipid complex, while SLS shows that the PEG-lipid associates to the BSA without promoting aggregation between adjacent protein/polymer-lipid conjugate complexes. SANS was used to show that BSA/PEG(2000)-PE complexes adopt an oblate ellipsoidal shape. Partially unfolded BSA is contained in the core of the oblate ellipsoid, which is surrounded by an external shell containing the PEG(2000)-PE.

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“…where d/dc ϭ kT͑1 ϩ k d ͒ [3] and 1/f m ϭ ͑1/f 0 ͒͑1 ϩ k h ͒ [4] with f 0 ϭ 6R (where is the medium viscosity). Here, concentration is expressed as particle hydrodynamic volume fraction, ϭ (4/3) R 3 .…”

Section: Introductionmentioning

confidence: 99%