Biotin-X-NHS is an amino-reactive biotinylation reagent with a long spacer arm. The 6-aminocaproic acid spacer arm provides distance between the biotin and the target ligand which helps alleviate steric hindrance. Biotin-X-NHS is used to biotinylate antibodies, proteins, peptides, or amino acids by reacting with primary amines as found in the N-terminus and Lysine side chains. The Biotin-X-NHS molecule is cell membrane permeable and can be used to label intracellular proteins. Optimal reaction conditions are at a pH of 7-9. Avoid amine-containing buffers, which may compete in the acylation reaction. - Chemical. CAS: 72040-63-2. Formula: C20H30N4O6S. MW: 454.54. Biotin-X-NHS is an amino-reactive biotinylation reagent with a long spacer arm. The 6-aminocaproic acid spacer arm provides distance between the biotin and the target ligand which helps alleviate steric hindrance. Biotin-X-NHS is used to biotinylate antibodies, proteins, peptides, or amino acids by reacting with primary amines as found in the N-terminus and Lysine side chains. The Biotin-X-NHS molecule is cell membrane permeable and can be used to label intracellular proteins. Optimal reaction conditions are at a pH of 7-9. Avoid amine-containing buffers, which may compete in the acylation reaction.