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Topic: Lipid bilayer

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Lipid

Liposomes

Integral protein

Plasma membrane

Cell membrane

Biological membrane

Phospholipid

Passive transport

Cell (biology)

Vesicle

Endocytosis

Transmembrane receptor

Active transport

Micelle

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	Structure of Fluid Lipid Bilayers
		A molecular understanding of the interaction of peptides and proteins with lipid bilayers requires experimental knowledge of the structure of the membrane bilayer, the transbilayer location of bound peptides, the structures the peptides adopt, and the changes that occur in the bilayer structure as a result of partitioning.
		The 'structure' of a fluid bilayer is consequently defined operationally as the time-averaged spatial distributions of the principal structural (quasi-molecular) groups of the lipid (carbonyls, phosphates, etc.) projected onto an axis normal to the bilayer plane (3), as shown in Figure 1 for the phosphate group of a phosphatidylycholine molecule.
		Disposition of an Amphipathic Alpha-Helix in the Bilayer
	blanco.biomol.uci.edu /Bilayer_Struc.html (1501 words)

	Lipid bilayer - Facts, Information, and Encyclopedia Reference article
		In biology and chemistry, a lipid bilayer is a membrane or zone of a membrane composed of lipid molecules (usually phospholipids).
		The lipid bilayer is a critical component of all biological membranes, including cell membranes, and is a prerequisite for cell-based organisms.
		The bilayer is composed of two opposing layers of lipid molecules arranged so that their hydrocarbon tails face one another to form the oily bilayer core, while their electrically charged or polar heads face the watery or "aqueous" solutions on either side of the membrane.
	www.startsurfing.com /encyclopedia/l/i/p/Lipid_bilayer.html (298 words)

	SparkNotes: Cell Membranes: The Lipid Bilayer
		The lipid bilayer is a universal component of all cell membranes.
		The structure is called a "lipid bilayer" because it is composed of two layers of fat cells organized in two sheets.
		Structurally, the lipid bilayer is asymmetrical: the lipid and protein composition in each of the two layers is different.
	www.sparknotes.com /biology/cellstructure/cellmembranes/section1.html (476 words)

	Dr. Joerg Kleinschmidt - Time-Resolved Distance Determinations by Fluorescence Quenching (TDFQ)
		The distances of these positions from the center of the lipid bilayer are known from X-ray diffraction experiments on some of the phospholipids (table in the middle of the figure).
		Currently, two methods are used to calculate the depth of a fluorophore in a lipid bilayer from a fluorescence quenching profile that is obtained from the relative fluorescence intensities in the presence of each of the different quenchers.
		The equation used for the determination of the distance between the fluorophore and the center of the lipid bilayer is derived from the Perrin equation for fluorescence quenching, assuming hard sphere quenching.
	www.biologie.uni-konstanz.de /folding/TDFQIntroduction.html (1383 words)

	Patent 6,726,925
		The surface active agent is contained in the bilayer membrane in an amount sufficient to increase the percentage of active agent released at the phase transition temperature of the lipid bilayer compared to that which would occur in the absence of the surface active agent.
		The surface active agent is present in the lipid bilayer membrane such that the membrane is stable in the gel-phase, i.e., the presence of the surface active agent does not destabilize the membrane, particularly prior to the melting of the lipid bilayer.
		Additionally, the present liposomal formulation's combination of lipid and compatible lysolipid provides a lipid/lysolipid mixture with a slightly lower gel-to-liquid crystalline transition temperature (of the lipid bilayer) compared to that of pure lipid alone, yet the gel-to-liquid crystalline transition temperature is not broadened by the inclusion of a lysolipid.
	www.pharmcast.com /Patents100/Yr2004/April2004/042704/6726925_Liposomes042704.htm (6597 words)

	Lipid bilayer at AllExperts
		A lipid bilayer or bilayer lipid membrane is a membrane or zone of a membrane composed of lipid molecules (usually phospholipids).
		The lipid bilayer is a critical component of all biological membranes, including cell membranes, and so is absolutly essential for all life on earth.
		The bilayer is composed of two opposing layers of lipid molecules arranged so that their hydrocarbon tails face one another and form an oily core, while their electrically charged heads face the aqueous solutions on either side of the membrane.
	en.allexperts.com /e/l/li/lipid_bilayer.htm (611 words)

	Membranes (Site not responding. Last check: 2007-10-29)
		Lipid bilayers self form because the hydrophobic ends of their constituent molecules face inward, packed together away from water, while the hydrophilic ends face outward, toward the water solvent (see micelles).
		Lipid bilayers are referred to as semipermeable because, while some substances can readily pass from one side of a lipid bilayers to the other, others do so only with great difficulty, if at all.
		Lipid bilayers tend to be impermeable to such things as proteins and amino acids, nucleic acids, and carbohydrates.
	www.mansfield.ohio-state.edu /~sabedon/biol1050.htm (1908 words)

	Mind the membrane
		Phospholipids, the lipid type that constitutes the majority of the cell membrane, are made up from a phosphate head (circles) that like water and lipid tail (lines) that hate it.
		They discovered that the bilayer behaves more like a fluid than a solid, and they made inroads in examining and characterizing the many kinds of proteins that are embedded in or associated with the membrane - a task that is still challenging today because of the poor solubility of most of these proteins in water.
		The lipid bilayer in rafts is asymmetric, with sphingomyelin and glycosphingolipids (both red) enriched in the 'outer' layer known as the exoplasmic leaflet, and glycerolipids (green) in the 'inner' layer known as the cytoplasmic leaflet.
	www.nature.com /horizon/livingfrontier/background/membrane.html (1761 words)

	The Protein-Tethered Lipid Bilayer: A Novel Mimic of the Biological Membrane - Science - RedOrbit
		The tethered bilayer lipid membrane is generated by substitution of protein-bound detergent molecules with lipids using in-situ dialysis or adsorption.
		However, the absolute thickness increment due to incorporation of lipid as estimated by SPS is not given in Table 1, because the exact degree of substitution of detergent molecules by lipid molecules is hard to assess.
		Assuming a dielectric constant of 30 for CcO (Smith et al., 1993) and 2 for DiPhyPC, the overall capacitance is estimated to be in the range of 2 F cm^sup -2^ for a bilayer thickness of 5 nm and a protein content of 30%.
	www.redorbit.com /news/display?id=104504 (5176 words)

	Phosphatidylethanolamine Enhances Rhodopsin Photoactivation and Transducin Binding in a Solid Supported Lipid Bilayer ...
		This is due to a variety of factors, e.g., variations in the properties of the lipid bilayer and alterations of the prism coating upon use.
		After rhodopsin was incorporated into the lipid bilayer and the PWR spectra stabilized (i.e., an equilibrium condition was reached), the aqueous compartment of the PWR cell was illuminated with yellow light (wavelength >500 nm) from a 150-W tungsten-halogen light source using a fiberoptic light guide (Fostec, Auburn, NY).
		In this view, both lipid and rhodopsin contribute to the PWR changes in the PE bilayer, whereas in the PC case, the smaller PWR spectral shifts are mainly due to the protein conformational change.
	www.redorbit.com /news/display?id=123216 (8590 words)

	Molecular Dynamics Simulations of the Lipid Bilayer Edge Biophysical Journal - Find Articles
		The properties of bilayer edges are important in determining the structure and stability of pores formed in vesicles and biomembranes.
		The treatment of electrostatic effects is shown to have a qualitative impact on the structure and stability of the edge, and significant differences are observed in the dynamics and structure of edges formed by DMPC and palmitoyl-oleoylphosphatidylethanolamine.
		Many physical and biochemical properties of lipid bilayers are important to the bilayer's fundamental role as the basis of biological membranes.
	findarticles.com /p/articles/mi_qa3938/is_200407/ai_n9429113 (660 words)

	Biochemicals amino acids hormone enzyme supplements
		Lipids are fatty acid esters, a class of relatively water-insoluble organic molecules, which are the "basic" components of biological membranes.
		The lipids are a large and diverse group of naturally occuring organic compounds that are related by their solubility in nonpolar organic solvents (e.g.
		Lipids consist of a polar or hydrophilic (attracted to water) head and one to three nonpolar or hydrophobic (repelled by water) tails.
	www.greatvistachemicals.com /biochemicals (2778 words)

	BB 350 Oregon State University (Site not responding. Last check: 2007-10-29)
		Highlights Lipids II Cellular membranes are sensitive to temperature.
		We categorize membrane proteins as integral (firmly embedded in both portions of a lipid bilayer), peripheral (embedded in only one portion of the lipid bilayer), or associated (not embedded in the lipid bilayer at all, but found close to it.
		Carbohydrates (sugar compounds) have links to components in a lipid bilayer in an orientation-specific direction - all carbohydrates are located on the portion of the lipid bilayer that is on the outside of the cell.
	oregonstate.edu /instruction/bb350/highlightslipids2.html (809 words)

	Lipid
		The polar heads all turn outward to form H-bonds with the water molecules, while the hydrophobic lipid tails are hidden in the inside.
		This Phospholipid bilayer structure forms the membrane that surrounds each of your cells and plays an important role in regulating cellular function.
		Lipid Hormones - Testosterone is responsible for sexual maturation at all stages of male development throughout life.
	bioweb.wku.edu /courses/BIOL115/Wyatt/Biochem/Lipid/Lipid3.htm (850 words)

	chap1
		The formation of a lipid bilayer in water is a self-assembling, 'downhill' process involving rearrangements of water and lipid molecules such that the overall free energy change for the reaction is at a optimum.
		According to this hypothesis, the self-assembled lipid bilayer, the fundamental moiety of biomembranes, is in a dynamic and liquid-crystalline state.
		Since their inception in the early 1960s, such lipid bilayer systems, either in the form of a planar BLM or of a vesicular liposome, have been used extensively as models of biomembranes (Chapter 4).
	www.msu.edu /user/ottova/chap1.html (1858 words)

	BC Online: 1B - Lipids in Water
		The lipid, during this process, is embedded in the micelle forming a detergent-lipid mixed micelle.
		A small molecule (such as monomer detergent, free lipid, or small aqueous solute) in the mobile phase (aqueous buffered solution) may enter the pores in the bead, while a larger macromolecule or aggregate (such as a large protein, a micelle, or a liposome) may not, due to size restriction.
		Characterization of lipid bilayer phases by confocal microscopy and fluorescence correlation spectroscopy PNAS, 96, pg 8461 (1999)
	employees.csbsju.edu /hjakubowski/classes/ch331/lipidstruct/ollipidwater.html (2539 words)

	Cell Membranes (Site not responding. Last check: 2007-10-29)
		The lipids in the plasma membrane are chiefly phospholipids like phosphatidyl ethanolamine and cholesterol.
		Phospholipids are amphiphilic with the hydrocarbon tail of the molecule being hydrophobic; its polar head hydrophilic.
		Furthermore, those that project into the aqueous surroundings of the cell are usually glycoproteins, with many hydrophilic sugar residues attached to the part of the polypeptide exposed at the surface of the cell.
	users.rcn.com /jkimball.ma.ultranet/BiologyPages/C/CellMembranes.html (446 words)

	Molecular Dynamics Simulations of the Lipid Bilayer Edge Biophysical Journal - Find Articles
		The properties of bilayer edges are important in determining the structure and stability of pores formed in vesicles and biomembranes.
		The treatment of electrostatic effects is shown to have a qualitative impact on the structure and stability of the edge, and significant differences are observed in the dynamics and structure of edges formed by DMPC and palmitoyl-oleoylphosphatidylethanolamine.
		Many physical and biochemical properties of lipid bilayers are important to the bilayer's fundamental role as the basis of biological membranes.
	www.findarticles.com /p/articles/mi_qa3938/is_200407/ai_n9429113 (660 words)

	Forces from Lipids
		The ordering the lipids at the membrane-water interface generates a large tension in each monolayer at the level of the phospholipid’s neck (2).
		In a molecular dynamics simulation forces from the lipid are directed as indicated by the yellow arrows.
		The concept of mechanosensitive channels being gated by forces inherent in the lipid bilayer is in variant with the intuition that such channels in eukaryotes are pulled by cytoskeletons or extracellular “strings”.
	www.molbio.wisc.edu /kung/Forces_from_Lipids.htm (832 words)

	Realistic physical images of lipid bilayer memrbanes
		Top: This classical cartoon of a lipid bilayer membrane captures the essential physical features of the bilayer as a symmetric bimolecular film composed of lipids that have a polar head group (the ball) attached to two long hydrophobic chains (the tails).
		The polar moieties of the lipid headgroup are shown in color and the acyl chain carbons are shown in fl.
		Structure of a fluid dioleoylphosphatidylcholine bilayer determined by joint refinement of x-ray and neutron diffraction data.
	www.tulane.edu /~biochem/faculty/facfigs/bilayer.htm (300 words)

	Potassium
		Intrinsic membrane proteins must have co-evolved with the lipid component of the membrane to give optimal function, within the constraints imposed by the role of lipids in the general physiology of the cell and by the requirements of the biosynthetic machinery for translation and insertion of proteins into membranes.
		Activities of a number of membrane proteins are sensitive to the thickness of the lipid bilayer, with the optimal thickness usually corresponding to that of a bilayer of dioleoylphosphatidylcholine (di(C18:1)PC) (Caffrey and Feigenson, 1981; Lee, 1998).
		One mechanism to reduce the effect of fluctuating bilayer thickness on the function of a membrane protein could be to reduce bilayer fluctuations in the vicinity of the protein.
	www.chemicalindustryinfo.com /articles/category/potassium (6590 words)

	Membrane Structure and Function
		The lipids are amphipathic in that they have hydrophilic polar heads pointing out and the hydrophobic portion forming the core.
		that are oriented in the same regions in the lipid bilayer.
		This fracture plane is inbetween the leaflets of the lipid bilayer, as shown by this cartoon.
	cellbio.utmb.edu /cellbio/membrane_intro.htm (1761 words)

	Lipid bilayer (Site not responding. Last check: 2007-10-29)
		The lipid bilayer is the foundation of all biological membranes, and is a prerequisite of cell-based life.
		Other self-organizing structures that lipids assume, depending on their concentration and type, include micelles, monolayers and vesicles.
		Cholesterol molecules in the bilayer assist in regulating fluidity.
	lipid-bilayer.iqnaut.net (227 words)

	Tarek's lipids page
		This is in contrast to the anesthetic case where the presence of the molecule led to a large perturbation of the electrostatic potential across to the membrane interface.
		Similarly, the analysis of the structural and dynamical properties of the lipid core are unchanged in presence of the non-immobilizer while there is a substantial increase in the microscopic viscosity for the system containing the anesthetic.
		Significant changes in the electric properties of the lipid bilayer result from the structural changes, which include a shift and broadening of the choline headgroup dipole (P-N) orientation distribution.
	www.ncnr.nist.gov /staff/tarek/lipids_dyn.html (1613 words)

	Membrane Structure and Function
		The lipids are amphipathic in that they have hydrophilic polar heads pointing out and the hydrophobic portion forming the core.
		that are oriented in the same regions in the lipid bilayer.
		This fracture plane is inbetween the leaflets of the lipid bilayer, as shown by this cartoon.
	anatomy.utmb.edu /cellbio/membrane_intro.htm (1761 words)

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