Abstract: The present invention relates to a molecular structure characterised in that said structure includes at least one amino acid sequence selected from: SEQ. ID NO.: 1, SEQ. ID NO.: 2, SEQ. ID NO.: 3, SEQ. ID NO.: 4, SEQ. ID NO.: 5, SEQ. ID NO.: 6, SEQ. ID NO.: 7, SEQ. ID NO.: 8, SEQ. ID NO.: 9, SEQ. ID NO.: 10, SEQ. ID NO.: 11, SEQ. ID NO.: 12, SEQ. ID NO.: 13, SEQ. ID NO.: 14, SEQ. ID NO.: 15, SEQ. ID NO.: 16, SEQ. ID NO.: 17, SEQ. ID NO.: 18, SEQ. ID NO.: 19, SEQ. ID NO.: 20, SEQ. ID NO.: 21, SEQ. ID NO.: 22, SEQ. ID NO.: 23, SEQ. ID NO.: 24, SEQ. ID NO.: 25, SEQ. ID NO.: 26, SEQ. ID NO.: 27, SEQ. ID NO.: 28, SEQ. ID NO.: 29, SEQ. ID NO.: 30, SEQ. ID NO.: 31, SEQ. ID NO.: 32, SEQ. ID NO.: 33, SEQ. ID NO.: 34, SEQ. ID NO.: 35, SEQ. ID NO.: 36, said amino acid sequence corresponding to an antigen complementarity determining region (CDR) of the variable domain of the heavy chain (CDR-H) or the light chain (CDR-L) of an antibody targeting the human transferrin receptor (TfR).