1) pH-value of AA-solutions

Check the ph-value of the given solutions of glycine, lysine and glutamic acid with exact pH-paper (0,5-steps)!

Conclusion?


2) Detection of the isoelectric point (IEP)

Required: tyrosine, each 1-molar NaOH- and HCl-solution

Tyrosine is insoluble in water. Prepare a suspension by giving a spatula-tip into a test-tube and adding a few ml of aqua dest. (fill 1/4). Add NaOH-solution dropwise and shake until the solution becomes clear.
Now add HCl-solution dropwise until the newly formed precipitate (ppt) vanishes again.

Observations? - Explanations?


3) Reaction with ninhydrin

Required: dil. glycine-solution, ninhydrin-reagent

Fill 1/3 of a test-tube with glycine-solution and add a few drops of ninhydrin-reagent. Heat carefully.

Observation? - Explanation?


4) Formation of a copper-complex

Required: glycine; solution of copper-II-carbonate; dil. NaOH

Fill a test-tube to 1/4 with aqua dest. and dissolve a small amount of glycine in it. Add a few ml of copper-II-carbonate-solution.

Observation?

Now add dropwise NaOH-solution as in Exp.2 and shake.
Does a ppt. occur?

Explanations?