User:Andy Maloney/Notebook/Lab Notebook of Andy Maloney/2010/01/20/Casein constituents

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So typically it is rather difficult to get whole casein to go into solution. I'm finding that each component of casein will go into solution rather easily. I'm doing the typically thing of 0.5 mg/mL of each constituent in PEM. I filter it through a 0.2 µm syringe filter and aliquot it into 2 mL aliquots and store at 4˚C.


I already know that kappa-casein will go into solution under constant stirring. Right now, I am using this kappa casein.


Alpha casein goes into PEM pretty easily as well. So far, all it takes is stirring.


Surprisingly, beta casein goes into PEM in under 5 minutes with constant stirring.

Heated whole casein

Since whole casein is so difficult to get into solution, I heat my solution to increase the whole casein's solubility. This works just fine and I can support motility with heat treated whole casein.

Steve Koch 03:16, 25 January 2010 (EST) Besides your results, I don't remember ever seeing anyone heating their casein for either kinesin or single-molecule DNA work. Have you? I'd say half of the reports don't say what kind of casein or how they get it into solution anyway, though.

Naming convention

Since I have so many different types of caseins, I am setting up a naming convention.

  • [math]\displaystyle{ \alpha }[/math]-PEM is PEM with 0.5 mg/mL [math]\displaystyle{ \alpha }[/math]-casein in it.
  • [math]\displaystyle{ \beta }[/math]-PEM is PEM with 0.5 mg/mL [math]\displaystyle{ \beta }[/math]-casein in it.
  • [math]\displaystyle{ \kappa }[/math]-PEM is PEM with 0.5 mg/mL [math]\displaystyle{ \kappa }[/math]-casein in it.
  • W-PEM is PEM with 0.5 mg/mL whole casein in it.
  • S-PEM is PEM with 0.5 mg/mL sialic acid in it.


The experiment will determine three things:

  • Can the different components of casein support motility?
  • Determine any speed differences of microtubules using the different components of casein as a passivator.
  • Does sialic acid work as a passivator?

Sialic acid

I want to have about the same number of sialic acid molecules as I would on kappa casein. This turns out to be around 2 µM sialic acid in solution. This is way to small of an amount to weigh out so I'm just going to make a solution of 10 mM sialic acid in PEM and dilute it from this stock.