IAS Fellows' Seminar - Cubic membranes: Formation and their potential role(s) in nature
Patterns in nature are visible regularities of form found in the natural world. These patterns recur in different contexts and can sometimes be modelled mathematically. Natural patterns include symmetries observed in trees, spirals, meanders, waves, foams, tessellations and stripes. Early Greek philosophers studied pattern with Plato, Pythagoras, and Empedocles attempting to explain the order in nature. Similarly, at the nano-scale level, membrane-bound cell organelles viewed in two and three dimensions (3D) may exhibit a wide range of patterns and symmetries. Cubic membrane represents one of the most fascinating and complex symmetrical membranes in biological systems. It is highly curved 3D periodic structure that corresponds to mathematically well-defined triply periodic minimal surfaces or the corresponding periodic nodal surfaces .
Cubic membrane structures attract great attention because of their unique feature of 3D periodicity in Transmission Electron Micrographs (TEM) and great similarity to the bicontinuous lipidic cubic phases. Cubic membranes have therefore often been compared to self-assembled cubic lipidic phases in aqueous dispersions that are well characterized in vitro, with several applications. Indeed, the efforts toward understanding formation and functional roles of cubic membranes in biological systems have been paralleled by the efforts in investigating cubic phases formation and their behaviour in lipid-water systems.
Dr Almherqi has reported that cubic membrane organization isolated from biological samples interact sufficiently with short segments of DNA . DNA condensed within the convoluted channels of the cubic membrane by an ‘unknown’ passive targeting mechanism. The interaction between DNA and cubic membrane seems to be closely related to the biophysical properties and architecture of cubic membranes, as different types of cubic membranes (e.g., gyroid type of cubic membrane vs double diamond type) interact differently with the host cells. Moreover, the DNA molecules condensed within the convoluted spaces of the CMs, are protected from oxidation by exogenous reactive oxygen species (ROS) probably because of the high levels of unique lipid (plasmalogen PC and DPA lipids) component of cubic membranes . Furthermore, these DNA–cubic membrane complexes are readily internalized within the cytoplasm of cultured mammalian cells . Thus, membrane nanoparticles with cubic structures may play a role in the inter and/or intracellular communication and genetic material transformation.
During the proposed seminar Dr Almsherqi will discuss the artistic, physical and biological aspects of cubic membranes with a special focus on the potential role of these highly organized membranes in nature.
1. Almsherqi ZA, Kohlwein SD, Deng Y. Cubic membranes: a legend beyond the Flatland* of cell membrane organization. J Cell Biol. 2006 Jun 19;173(6):839-44.
2. Almsherqi ZA, Hyde S, Ramachandrana M, Deng Y (2008). Cubic membranes: a structure-based design for DNA uptake. J R Soc Interface 5(26): 1023-9.
3. Deng Y, Almsherqi ZA, Shui GH, Wenk MR, Kohlwein SD (2009). Docosapentaenoic acid (DPA) is a critical determinant of cubic membrane formation in amoeba Chaos mitochondria. FASEB J 23:2866-71.
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