Mosaic Of Domains Research Articles

Geoscience Data Integration: Insights into Mapping Lithospheric Architecture

SUMMARY In order to develop a 4D understanding of the architecture of the entire lithosphere, it is necessary to embrace integration of multi-disciplinary, multi-scale data in a GIS environment. An holistic understanding has evolved whereby geologic, geochemical and geophysical signals are consistent with a subcontinental lithospheric mantle (SCLM) dominated by a mosaic of domains of Archean ancestry, variably overprinted by subsequent tectonothermal events. Pristine Archean SCLM is mostly highly depleted (high Mg#), low density, high velocity and highly resistive, and preserves intact Archean crust. There is a first order relationship between changes to these signals and the degree of tectonothermal overprint (by melts, fluids). Continental crust is comprised largely of reconstituted Archean components, variably diluted by juvenile addition, symptomatic of the various overprinting events. These events impart crustal fabrics and patterns dictated by SCLM architecture, influenced by the free surface and crust-mantle decoupling.

Lipid rafts: structure, function and role in HIV, Alzheimer's and prion diseases.

The fluid mosaic model of the plasma membrane has evolved considerably since its original formulation 30 years ago. Membrane lipids do not form a homogeneous phase consisting of glycerophospholipids (GPLs) and cholesterol, but a mosaic of domains with unique biochemical compositions. Among these domains, those containing sphingolipids and cholesterol, referred to as membrane or lipid rafts, have received much attention in the past few years. Lipid rafts have unique physicochemical properties that direct their organisation into liquid-ordered phases floating in a liquid-crystalline ocean of GPLs. These domains are resistant to detergent solubilisation at 4 degrees C and are destabilised by cholesterol- and sphingolipid-depleting agents. Lipid rafts have been morphologically characterised as small membrane patches that are tens of nanometres in diameter. Cellular and/or exogenous proteins that interact with lipid rafts can use them as transport shuttles on the cell surface. Thus, rafts act as molecular sorting machines capable of co-ordinating the spatiotemporal organisation of signal transduction pathways within selected areas ('signalosomes') of the plasma membrane. In addition, rafts serve as a portal of entry for various pathogens and toxins, such as human immunodeficiency virus 1 (HIV-1). In the case of HIV-1, raft microdomains mediate the lateral assemblies and the conformational changes required for fusion of HIV-1 with the host cell. Lipid rafts are also preferential sites of formation for pathological forms of the prion protein (PrPSc) and of the [beta]-amyloid peptide associated with Alzheimer's disease. The possibility of modulating raft homeostasis, using statins and synthetic sphingolipid analogues, offers new approaches for therapeutic interventions in raft-associated diseases.

The lipid organisation of the cell membrane

Lipids and proteins in biological membranes are arranged in a mosaic of domains in the membrane. These domains represent small-scale heterogeneities in composition, shape and fluidity within the plane of the membrane, over the range of hundreds of nanometers to a few micrometers. They arise from the complex interactions of the heterogeneous mixtures of phospholipids, sterols, and proteins that make up all biological membranes.

Structures of Na and Cs layers adsorbed on Pt(111)

The atomic structures of Na and Cs layers adsorbed on the Pt(111) face have been studied at 85 K and room temperature by LEED. At room temperature, Na layers are fully disordered while Cs overlayers exhibit ordered structures. At low temperature, (2×2) and ( 3 × 3 ) R30° phases are observed at Na coverage below 0.33. At higher coverages, the Na layer is formed by a mosaic of domains with incommensurate hexagonal structures which are either aligned or rotated relative to the substrate. The rotation angle of the rotated domains depends on the interatomic spacing in the layer. For Cs layers at low temperature the (2×2) structure is observed but the ( 3 × 3 ) structure is rotationally disordered. For Cs coverage beyond 0.33, a mosaic of domains with incommensurate structures which are either aligned or angularly disordered is formed at 85 K while at room temperature only the aligned structure is observed. The origin of the incommensurate aligned phases observed for both alkali layers is discussed and may be attributed to the influence of steps during the overlayer growth.