The Effects of Cholesterol Oxidation on Erythrocyte Plasma Membranes: A Monolayer Study

This is the final version. Available on open access from MDPI via the DOI in this recordData Availability Statement: All data are available from the corresponding authors.Cholesterol plays a key role in the molecular and mesoscopic organisation of lipid membranes and it is expected that changes in its molecular structure (e.g., through environmental factors such as oxidative stress) may affect adversely membrane properties and function. In this study, we present evidence that oxidation of cholesterol has significant effects on the mechanical properties, molecular and mesoscopic organisation and lipid–sterol interactions in condensed monolayers composed of the main species found in the inner leaflet of the erythrocyte membrane. Using a combination of experimental methods (static area compressibility, surface dilatational rheology, fluorescence microscopy, and surface sensitive X-ray techniques) and atomistic molecular dynamics simulations, we show that oxidation of cholesterol to 7-ketocholesterol leads to stiffening of the monolayer (under both static and dynamic conditions), significant changes in the monolayer microdomain organisation, disruption in the van der Waals, electrostatic and hydrophobic interactions between the sterol and the other lipid species, and the lipid membrane hydration. Surface sensitive X-ray techniques reveal that, whilst the molecular packing mode is not significantly affected by cholesterol oxidation in these condensed phases, there are subtle changes in membrane thickness and a significant decrease in the coherence length in monolayers containing 7-ketocholesterol.Engineering and Physical Sciences Research Council (EPSRC

Space-Varying Iterative Restoration of Diffuse Optical Tomograms Reconstructed by the Photon Average Trajectories Method

The possibility of improving the spatial resolution of diffuse optical tomograms reconstructed by the photon average trajectories (PAT) method is substantiated. The PAT method recently presented by us is based on a concept of an average statistical trajectory for transfer of light energy, the photon average trajectory (PAT). The inverse problem of diffuse optical tomography is reduced to a solution of an integral equation with integration along a conditional PAT. As a result, the conventional algorithms of projection computed tomography can be used for fast reconstruction of diffuse optical images. The shortcoming of the PAT method is that it reconstructs the images blurred due to averaging over spatial distributions of photons which form the signal measured by the receiver. To improve the resolution, we apply a spatially variant blur model based on an interpolation of the spatially invariant point spread functions simulated for the different small subregions of the image domain. Two iterative algorithms for solving a system of linear algebraic equations, the conjugate gradient algorithm for least squares problem and the modified residual norm steepest descent algorithm, are used for deblurring. It is shown that a 27% gain in spatial resolution can be obtained

Powder diffraction and synchrotron radiation.

Powder diffraction is one of the fundamental techniques for the investigation of materials. Its sensitivity to long range order makes it ideal for the identification, quantification and structural characterization of crystalline phases. Powder diffraction experiments performed at synchrotron sources make ample use of the intrinsic characteristics of synchrotron radiation in terms of energy tunability, brilliance, natural divergence, and excellent signal/noise ratio. Synchrotron radiation powder diffraction (SR-PD) enhances and optimizes the traditional applications of laboratory XRPD, such as phase identification, phase quantification, texture analysis, and peak broadening analysis in terms of stress/strain. However, the properties of the synchrotron X-rays also allow a number of experiments not accessible with laboratory sources, especially in terms of time-resolution, the use of non-ambient sample environments, and simultaneous and combined experiments. The mapping of the physical, chemical, and crystallographic properties of the sample in 2D and 3D using smart combinations of diffraction imaging spectroscopy is the natural current evolution of many synchrotron instruments, and one that is bound to have a great impact on many aspects of materials studies