How to:
1.Ammonium sulphate precipitation
2. solvent ppt of a protein
3 use of a dialysis in removing salt from a protein preparation.
Bullet points or references will be fine.

Hello -

A very good, overall review page which covers all three steps:
http://staff.science.nus.edu.sg/~dbsyhh/BL3102%20L2%20salt%20pptn%20and%20dialysis_files/frame.htm

1) Ammonium sulfate protein precipitation is a commonly used technique
for purifying proteins.  Protein precipitate at specific
concentrations of ammonium sulphate relative to their net charge
density.

In brief, the procedure goes as follows:  
1) obtain protein solution of interest
2) add ammonium sulphate (either as dry powder or as a saturated
solution) to acheive desired percentage of ammonium sulphate
(percentage of saturated) to a chilled, stirring solution
3) allow to stir for 15-30 minutes
4) collect precipitated protein by centrifugation

As often used, ammonium sulphate precipitation is used as a step in
the purification of a protein.  To see how this helps, consider a
target protein which precipitates at 50% saturated ammonium sulfate. 
Other proteins could be removed from the solution by the following:

1) take protein solution and add ammonium sulphate to a concentration
of 40%
2) chill, stir for 30 minutes
3) centrifuge, and discard pellet (this discards protein which
precipitated at a lower concentration)
4) add ammonium sulphate to a concentration of 50%
5) chill, sitr for 30 minutes
6) centrifuge and keep the pellet (the pellet has your protein, all
higher precipitating proteins are discarded with the supernatant)
7) resuspend pellet into buffer of choice
8) dialyze sample to remove ammonium sulphate (see last question).


A usual method of ammonium sulphate precipitation complete with
recipes and techniques:
http://research.biology.arizona.edu/mosquito/willott/proj/labpro/Prot/Proppt/Ammon.html


A general short reference on the practice of precipitating proteins:
http://www.sbu.ac.uk/biology/enztech/concentration.html

A lab manual discussing both ammonium sulfate precipitation and the
dialysis step:
http://www.bio.mtu.edu/campbell/bl482/lectures/lec5/482lec5.pdf


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2) Solvent ppt - Done almost exactly as an ammonium sulphate ppt -
solvent is added to a protein solution to a designated concentration,
the solution is stirred, chilled, centrifuged and pellets are
collected.  Commonly used solvents include the simple alcohols:
methanol, ethanol, isopropanol and other common solvents like acetone.
 The principle of these precipitations is that organic solvents
denature a protein exposing more hydrophobic (non-polar, not soluble
in water) areas of the protein which reduces it's solubility.  Enzymes
do not commonly survive these procedures (unlike above).

A simple description of the method:
http://www.glue.umd.edu/~nsw/ench485/lab6b.htm#Procedures

A method using acetone precipitation (note, you would need to
determine the amount of acetone, or other solvent, necessary for your
protein of interest):
http://www.mimg.ucla.edu/faculty/black/protein_elution.htm

Ethanol, acetone and TCA precipitation methods:
http://www.brcf.med.umich.edu/METHODS.NSF/0/4b35713f1bf88dcf85256497005965a8?OpenDocument


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3) Dialysis to remove salts - the principle of dialysis is that
semi-permeable membranes exist with certain sized holes in them which
allow small molecules to pass across the membrane.  With solutions on
either side, water and other small molecules freely diffuse between
both sides.  The size of the pores can be varies so as to retain large
molecules on one side of the membrane (such as a protein).  What this
allows for is simple dilution of a salt out of a protein solution
without diluting the protein solution itself.  To carry this out, the
protein solution is placed within a dialysis membrane (usually a small
tube, looks like a sausage) and the membrane is immersed in a large
quantity of the buffer into which you would like the protein to be in.
 As the small salt molecules can cross the membrane, they will
distribute throughout the entire volume of the two solutions (one in
the tube, one outside) while the protein, because it cannot fit
through the pores, is stuck inside the membrane.  Therefore, the salt
concentration is diluted by the total volume.  So, if you place a 1mL
protein sample (with 50% ammonium sulfate) in a membrane and immerse
it in 1L of buffer you wind up with 1mL of protein sample at 1/1000th
of the ammonium sulfate concentration.  This is commonly done 2-3
times to completely remove salts or other small molecules.

A good explanation of the procedure:
http://www.bio.mtu.edu/campbell/bl4820/lectures/lec5/482w52.htm

Explanation with formulas (near the bottom of the document):
http://wine1.sb.fsu.edu/bch5425/lect30/lect30.htm


Please let me know if you want more information or explanation by
requesting a clarification - I will be happy to refine the information
to more particularly suit the answer you want.

synarchy


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