Which of the following tests is a specific test for proteins?

The isoelectric point of alanine is $pH = 6$. At which $pH$ will the maximum concentration of the zwitterion of alanine be present?

In the following compound,the favourable site/s for protonation is/are:
(Image description: Adenine structure with labels $a$ on the exocyclic $-NH_2$ group,$b$ on the pyrimidine ring nitrogen,$c$ on the other pyrimidine ring nitrogen,$d$ on the imidazole ring nitrogen,and $e$ on the imidazole ring $-NH-$ group.)

Identify the neutral amino acid from the following list represented by three-letter symbols.

How many subunits are present in hemoglobin?

How many of the given compounds will give a positive Biuret test?
Glycine,Glycylalanine,Tripeptide,Biuret.