Dynamics of Apolipoprotein B-100 in Interaction with Detergent Probed by Incoherent Neutron Scattering

Abstract

Apolipoprotein B-100 (apo B-100) is the protein moiety of both low-and verylow-density lipoproteins, whose role is crucial to cholesterol and triglyceride transport. Aiming at the molecular dynamics' details of apo B-100, scarcely studied, we performed elastic and quasi-elastic incoherent neutron scattering (EINS, QENS) experiments combining different instruments and time scales. Similar to classical membrane proteins, the solubilization results in remaining detergent, here Nonidet P-40 (NP40). Therefore, we propose a framework for QENS studies of protein−detergent complexes, with the introduction of a combined model, including the experimental apo B-100/NP40 ratio. Relying on the simultaneous analysis of all QENS amplitudes, this approach is sensitive enough to separate both contributions. Its application identified two points: (i) apo B-100 slow dynamics and (ii) the acceleration of NP40 dynamics in the presence of apo B-100. Direct translation of the exposed methodology now makes the investigation of more membrane proteins by neutron spectroscopy achievable.

Notes on Fitting and Analysis Frameworks for QENS Spectra of (Soft) Colloid Suspensions

“…Since the signal is typically dominated by incoherent scattering, the q-dependence mainly influences the different dynamic features. While this approach includes the separation of the (apparent) global diffusion from internal diffusive processes [8], the same procedure can be applied to separate the scattering signal of the crowders from the one of the protein of interest [23], the contributions of monomers and crystals [30], the contributions of two different proteins [31], or to distinguish the scattering signal of proteins from the one coming from the detergent used for purification [32].…”

Sub-Nanosecond Dynamics of Pathologically Relevant Bio-Macromolecules Observed by Incoherent Neutron Scattering

“…In relation to this study on LDL, the characterization of apo B-100 has recently been conducted using QENS [ 75 ]. Since apo B-100 is an amphiphilic protein, the use of detergents called Nonidet P-40 (NP40) was necessary to solubilize the protein.…”

Short-Time Transport Properties of Bidisperse Suspensions of Immunoglobulins and Serum Albumins Consistent with a Colloid Physics Picture

“…Up to now, the separation of different diffusive contributions was possible either due to partial deuteration of the samples investigated 39 or to the use of advanced modeling in hydrated powders. 41 Here, we test the predicted bulk behavior of an aqueous solution of two distinct tracer proteins, namely, bovine serum albumin (BSA) and bovine polyclonal gamma-globulin (Ig). We separate the apparent center-of-mass diffusion coefficients measured simultaneously for both proteins from the internal diffusive processes and the solvent contributions.…”

“…Hence, a dedicated study of a model polydisperse system with tunable tracer composition is necessary, which in its simplest case would be a bidisperse system with a tunable total volume fraction and relative composition. Up to now, the separation of different diffusive contributions was possible either due to partial deuteration of the samples investigated or to the use of advanced modeling in hydrated powders . Here, we test the predicted bulk behavior of an aqueous solution of two distinct tracer proteins, namely, bovine serum albumin (BSA) and bovine polyclonal gamma-globulin (Ig).…”