text: Amino acids are shown in the one-letter abbreviation.
  Hydrophobic amino acids (hydropathy index with positive value)
  and Tryptophan (W) found at a given position in more than 50% of
  analysed IG and TR sequences are shown in blue.
  All Proline (P) are shown in yellow.
  Missing positions in IMGT Colliers de Perles based on 3D
  structures may be due to incomplete experimental data.
  Arrows indicate the direction of the beta sheets and their
  different designations in 3D structures. This information has to be
  used carefully if not supported by experimental data.
  The positions 26, 39 and 104 are shown in squares by homology with the corresponding positions in the V-REGIONs.
  Positions 45 and 77 which delimit the characteristic "CD" strand of the C-DOMAINs, and position 118 which corresponds structurally to J-PHE or J-TRP of the J-REGION, are also shown in squares.
  Hatched circles or squares correspond to missing positions according to the IMGT unique numbering for C-DOMAINs
  (Lefranc et al. 2005 PMID: 15572068
  In green, position of amino acid changes involved in allotype polymorphism.
  Strands of the beta-pleated sheet localized at the interface between domains are shown in bold.
  The hinge six amino acids which belongs to the same exon as the CH2 domain are not shown.