But in the next step, we once again mix this molecule with CF three COOH our trifloroacetic acid, a dilute acid. If we mix it with this, that will remove the TBA group. And then we mix this molecule minus the TBA group with this amino acid and that will form a tripepptide. And we essentially continue that until we form that polypeptide that we actually want to form. So let's suppose we followed that step many, many times and eventually we formed the following polypeptide chain that consists of N number of amino acids. So this is the first amino acid that contains the group R one.