Alignment of 25 amino acid sequences known to contain binding sites for quinine-dependent antibodies using the Clustal W algorithm.^29,30  GPIIIa residues 50, 62, and 66,¹²  GPIX residues 110 and 115,²⁸  and GPIb alpha residues 283 to 293²⁷  are known to be critical for binding of selected groups of quinine-dependent antibodies to the respective glycoproteins. Amino acids shaded darkly are identical; those shaded lightly are chemically similar. There is no significant homology between GPIIIa 45 to 69 and GPIX 99 to 123 (alignment score, −26). However, the alignment score between GPIIIa 45 to 69 and GPIb alpha 276 to 300 is 47, approximately 30% of the maximum score possible (2 sequences identical).