Membrane inclusions

Septate desmosome Membranous inclusions Secretory bodies Golgi stack... 

The enzyme can be entrapped into the growing polymer or gel materials or microcapsules (microcncapsu-lation). The retention of enzymes in the reaction vessel can also be achieved by an ultrafiltration membrane. All these immobilization types have in common that the enzymes are not modified and are still acting in their soluble form, so that they should be freely mobile in their cage . An older but good review of these techniques is given by Tramper [72], Frequently used matrices for gel entrapment are polyacrylamide and collagen [41]. The membrane inclusion method is a broadly applicable one. 

As a simple depiction of a hpid bilayer, one can consider it as a film or a slab, which may be curved, compressed or dilated, and sheared. At physiological temperatures most natural hpid membranes are fluid. Therefore, within this slab, the hpid molecules are free to move. Below the hpid phase transition temperature, single-component membranes crystalhze. In this so called gel phase, the relative mohon of hpids and membrane inclusions is principally hindered. The fluidity of the membrane and resistance to shear in the plane of the film are characterized by the shear viscosity, % (or the diffusion coefficient of the hpids). Typical values... 

Effects of Membrane Inclusions and Media on the Response and Stability of Fluid Vesicles in Electric Fields... 

In the previous two sections we discussed the electrodeformation and electroporation of vesicles made of single-component membranes in water. In this section, we consider the effect of salt present in the solutions. The membrane response discussed above was based on data accumulated for vesicles made of phosphatidylcholines (PCs), the most abundant fraction of lipids in mammahan cells. PC membranes are neutral and predominantly located in the outer leaflet of the plasma membrane. The inner leaflet, as well as the bilayer of bacterial membranes, is rich in charged lipids. This raises the question as to whether the presence of such charged lipids would influence the vesicle behavior in electric fields. Cholesterol is also present at a large fraction in mammalian cell membranes. It is extensively involved in the dynamics and stability of raft-hke domains in membranes [120]. In this section, apart from considering the response of vesicles in salt solutions, we describe aspects of the vesicle behavior of fluid-phase vesicles when two types of membrane inclusions are introduced, namely cholesterol and charged lipids. 

As demonstrated above, the edge tension is a sensitive parameter, which effectively characterizes the stability of pores in membranes. Compiling a database for the effect of various types of membrane inclusions will be useful for understanding the lifetime of pores in membranes with more complex compositions, which is important for achieving control over medical applications for drug and gene delivery in cells. 

Section III describes the mechanical influence that a membrane can have on channel stabilization, focusing on simple physical models used to understand the mechanism of membrane-peptide interaction. We describe the elastic interaction between a membrane and an inserted peptide, focusing on GA, and first provide a brief overview of the basics of the elastic theory of membranes, demonstrating the formal equivalence of these issues to a classical problem in mechanical engineering. We then consider different descriptions of the interaction of a membrane with an inclusion and follow with a discussion of lipids influences on channel lifetimes. Finally, we describe a new perspective for describing the membrane-inclusion interaction. It emphasizes the inclusion-induced perturbation of membrane elastic constants at the lipid-peptide interface. 

S. Marcelja, Toward a realistic theory of the interaction of membrane inclusions, Biophys. J., 1999, 76, 593-594. 

The potential applications of bolaamphiphiles include the formation of monolayer vesicles for drug/gene delivery, ultra thin monolayer membranes, inclusion of functionalities into membranes, and disruption of biological membranes [59a]. 

Fournier JB (1999) Microscopic membrane elasticity and interactions among membrane inclusions interplay between the shape, dilation, tilt and tilt-difference modes. Eur Phys JB 11 261-272... 

Dommersnes P, Eoumier JB (1999) N-body study of anisotropic membrane inclusions membrane mediated interactions and ordered aggregation. Eur Phys J E 12 9-12... 

Dommersnes P, Eoumier J (2002) The many-body problem for anisotropic membrane inclusions and the self-assembly of saddle defects into an egg carton . Biophys J 83 2898-2905... 

Weikl TR, Kozlov MM, Helfrich W (1998) Interaction of conical membrane inclusions effect of lateral tension. Phys Rev E 57 6988-6995. doi 10.1103/PhysRevE.57.6988... 

Park J-M, Lubensky TC (1996) Interactions between membrane inclusions on fluctuating membranes. J Phys I France 6(9) 1217—1235... 

Kim KS, Neu JC, Oster GF (1999) Many-body forces between membrane inclusions a new pattern-formation mechanism. Europhys Lett 48(1) 99—105... 

Kim KS, Chou T, Rudnick J (2008) Degoierate ground-state lattices of membrane inclusions. Phys Rev E 78 011401. doi 10.1103/PhysRevE.78.011401... 

Auth T, Gompper G (2009) Budding and vesiculation induced by conical membrane inclusions. Phys Rev E 80 031901. doi 10.1103/PhysRevE.80.031901... 

The prominent organelle in the cytoplasm of Clara cells from both wild-type strain 129 and Clara cell secretory protein -/- 129 mice is the smooth endoplasmic reticulum, which occupies about 20% of the cell cytoplasm (Strife et al. 2002). Despite the similarities in abundance there were two aspects of the smooth endoplasmic reticulum that differed markedly between both genotypes of mice. First, electron-dense material that was abundant within the lumen of smooth endoplasmic reticulum of Clara cells from wild-type mice was not as evident within the lumen of smooth endoplasmic reticulum of Clara cells from Clara cell secretory protein -/-129 mice. Second, Clara cells from Clara cell secretory protein -/- 129 mice were unique in that they possessed large concentric whorls of endoplasmic reticulum located within the apical portion of the cell. Membrane-bound inclusions, which appeared to he surrounded by at least one layer of endoplasmic reticulum, were found at the centre of these whorls and contained material of varying electron density and compaction. Some of these inclusions had the characteristics of mitochondria based on the presence of crista-like membrane inclusion. 

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