User:Nadiezda Fernandez-Oropeza/Notebook/Notebook/2010/10/04

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Definitions and Concepts (Kinesin related)

  • Important concepts related to Kinesin and the Gliding motility assay.

Osmotic stress

“Osmotic stress is a sudden change in the solute concentration around a cell, causing a rapid change in the movement of water across its cell membrane.” [1]

“Osmotic stress occurs when the concentration of molecules in solution outside of the cell is different than that inside the cell. When this happens, water flows either into or out of the cell by osmosis, thereby altering the intracellular environment. Hyperosmotic stress causes water to diffuse out of the cell, resulting in cell shrinkage, which can lead to DNA and protein damage, cell cycle arrest, and ultimately cell death. Cells compensate or adapt to osmotic stress by activating an osmotic stress response pathway that is controlled by a gene called nuclear factor of activated T cells 5 (NFAT5)/tonicity enhancer binding protein (TonEBP). This NFAT5/TonEBP protein is the only known mammalian transcription factor that is activated by hyperosmotic stress.” [2]

  • “Osmolytes are organic compounds affecting osmosis. They are soluble in the solution within a cell, or in the surrounding fluid. They play a role in maintaining cell volume and fluid balance. For example, when a cell swells due to external osmotic pressure, membrane channels open and allow efflux of osmolytes which carry water with them, restoring normal cell volume.” [3]

Surface passivation

“Passivation is the process of making a material "passive", usually by the deposition of a layer of oxide on its surface.” [4]

“To passivate is to reduce the chemical reactivity of a surface by applying a coating.” [5]

  • Casein is a protein that is found in milk and used independently in many foods as a binding agent. Technically, it is part of a group called phosphoproteins, collections of proteins bound to something containing phosphoric acid. Casein is a salt, meaning it has no net ionic charge, of the element calcium. It has a number of interesting properties that make it useful in foods and cooking.”

“Denaturing occurs when a protein loses its inherent structure, due to high heat or acid for example, at which point it no longer acts in the ordinary manner. Casein, because of its structure, is not susceptible to denaturing.” [6]

Steve Koch 22:22, 4 October 2010 (EDT): This is interesting about casein not denaturing with moderate heat. Andy mentioned this in his paper as casein not having a defined structure and thus not being denaturable. I still find it hard to believe, though...so keep your eyes open for any other information you come across about this.
  • Integrins are receptors that mediate attachment between a cell and the tissues surrounding it, which may be other cells or the extracellular matrix (ECM). They also play a role in cell signaling and thereby define cellular shape, mobility, and regulate the cell cycle.” [7]
  • Chemical suspension: An example of a suspension would be sand in water. The suspended particles are visible under a microscope and will settle over time if left undisturbed. This distinguishes a suspension from a colloid, in which the suspended particles are smaller and do not settle. Colloids and suspensions are different from solutions, in which the dissolved substance (solute) does not exist as a solid, and solvent and solute are homogeneously mixed.” [8]
  • Chelator is a substance that binds particular ions, removing them from solution.



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