<prompt> When is Edmans reagent used?To determine amino acid composition of a peptideTo determine the amino acid sequence of a peptideTo cleave a peptide bond formed by basic amino acidsTo cleave a peptide bond formed by acidic amino acids  <response>: Sequencing is a stepwise process of identifying the specific amino acid at each position in the peptide chain, beginning at the N-terminal end.Phenylisothiocyanate, known as Edman reagent, is used to label the amino terminal residue under mildly alkaline conditions. The resulting phenylthiohydantoin PTH derivative introduces an instability in the N-terminal peptide bond that can be selectively hydrolyzed without cleaving the other peptide bonds. The identity of the amino acid derivative can then be determined. Edman reagent can be applied repeatedly to the shortened peptide obtained in each previous cycle. Ref. Lippincotts, 5th Edition, Pg. 15 