Effect of Oxidation on the Structure of Human Low- and High-Density Lipoproteins

Abstract

This work presents a controlled study of low-density lipoprotein (LDL) and high-density lipoprotein (HDL) structural changes due to in vitro oxidation with copper ions. The changes were studied by small-angle x-ray scattering (SAXS) and dynamic light scattering (DLS) techniques in the case of LDL and by SAXS, DLS, and Z-scan (ZS) techniques in the case of HDL. SAXS data were analyzed with a to our knowledge new deconvolution method. This method provides the electron density profile of the samples directly from the intensity scattering of the monomers. Results show that LDL particles oxidized for 18 h show significant structural changes when compared to nonoxidized particles. Changes were observed in the electrical density profile, in size polydispersity, and in the degree of flexibility of the APO-B protein on the particle. HDL optical results obtained with the ZS technique showed a decrease of the amplitude of the nonlinear optical signal as a function of oxidation time. In contrast to LDL results reported in the literature, the HDL ZS signal does not lead to a complete loss of nonlinear optical signal after 18 h of copper oxidation. Also, the SAXS results did not indicate significant structural changes due to oxidation of HDL particles, and DLS results showed that a small number of oligomers formed in the sample oxidized for 18 h. All experimental results for the HDL samples indicate that this lipoprotein is more resistant to the oxidation process than are LDL particles.

Determination of Internal Density Profiles of Smart Acrylamide-Based Microgels by Small-Angle Neutron Scattering: A Multishell Reverse Monte Carlo Approach

“…As already mentioned in the introduction, a similar form-free algorithm has been proposed 62 , but not applied to spherically symmetric systems, and in particular not to microgels. 61,63 For the sake of comparison, all model predictions have been calculated using the same relative particle polydispersity (see Eq. (1) 39 .…”

“…61 In some cases, the density distributions can be defined by a small set of parameters, like crosssection density profiles in lamellar systems, 62 or radial density profiles in globular systems. 63 The densities are described as a set of Gaussian functions, and the technique is termed Gaussian deconvolution. We have applied a similar approach to monodisperse block copolymer micelles in the past, 64 but to the best of our knowledge this form-free technique has not been generally applied to small-angle scattering of polydisperse microgel particles to retrieve the radial density profile, with the exception of the work by Keidel mentioned above.…”

High hydrostatic pressure specifically affects molecular dynamics and shape of low-density lipoprotein particles

“…The shell consists of a phospholipid monolayer, unesterified cholesterol and the amphipathic apoB100 molecule wrapped around the surface6. It is well known that lipoproteins play a key role in atherosclerosis, which is a dynamic and progressive inflammatory disease that promotes lipid deposition in the arteries78. Moreover, the lipid composition of the LDL core becomes modified in case of certain diseases such as hyperlipidemia , where LDL is enriched with cholesterol or triglycerides89.…”

Calculation of Small-Angle Scattering Patterns

“…These methods, namely, small-angle scattering (SAS) either with neutrons (SANS) or X-rays (SAXS), static light scattering (SAS), etc., can provide useful information about the structure of the investigated system. However, scattering methods give information in the Fourier space (reciprocal space/scattering space) which can difficult its interpretation and modeling [8][9][10].…”