Membrane

2022-02-08 links: reference:

Membrane #

• All transmembrane proteins are integral membrane proteins, but not vice versa.

Lipids #

https://www.lipidmaps.org/resources/lipidweb/lipidweb_html/lipids/lipids.html One of these days I need to assemble an ordered list of least to most polar. Lipids are amiphipilic (one end is water-soluble/polar, another is not) allowing them in water to spontaneously form bilayers

• The main constituents are:
  • Glycerol-based
    • Glycosylglycerides
      • (More abundant than phospholipids)
    • Phospholipids
  • Cholesterol
  • Ceramide-based sphingolipids
    • A ceramide is Sphingosine + a fatty acid.
    • Glycolipids
      • Cerebroside (Can use galactose. Called glucocerebroside when with glucose.)
      • Ganglioside
• Membrane Lipid Composition: Effect on Membrane and Organelle Structure, Function and Compartmentalization and Therapeutic Avenues
  • (PM = plasma membrane duh)
  • So ceramide, and any sphingolipid besides Sphingomyelin, really doesn’t make up >1% of membrane composition?
• Membrane lipids: where they are and how they behave
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• Understanding the diversity of membrane lipid composition
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    • Interesting how they make the case of these bendy lipids like DHA allow the formation of endocytotic vesicles.
  • ALPS motifs detect packing defects.
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• Membrane Lipids Direct Proteins and Proteins Direct Lipids (from some guy’s blog - this guy is very high IQ and talks about various topics)

Curvature #

• Lipid asymmetry, hydrophobic insertion, scaffolding, oligomerization, and crowding.
• The Role of Traction in Membrane Curvature Generation (Jun 2017)
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  • Seems to take from a figure in an earlier study of (one of) theirs: Systems biology of cellular membranes: A convergence with biophysics (May 2017)
    • When lipid composition differs between the two layers, curvature is induced. They can have the following 3 shapes (random examples):
      • Cylindrical: Phosphatidylcholine, Phosphatidylserine, Sphingomyelin, Phosphatidulinositol
      • Conical: Phosphatidylethanolamine (including Dilinoleoyl), Cardiolipin, DAG
        • Small polar heads.
      • Inverse conical: Lysolipids, PIP?
        • Bulky, polar head, and only one acyl chain.
      • [Lipid Polymorphisms and Membrane Shape (Frolov 2011)]
        • π(z) = torque.
        • 
          • Nonlamellar = Phase shift. (inverted hexagonal): https://en.wikipedia.org/wiki/Lipid_polymorphism?useskin=vector. HI/II = inverted hexagonal:
        • SC = spontaneous curvature. Cylindrical = 0 SC.
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• Membrane curvature at a glance
  • I must be careful, as its idea of conical/inverse-conical is the opposite of other studies. Is it relative? I must tread carefully.
  • Along with amphipathic helices, C2 domains like Synaptotagmin induce positive curvature: