This analogue replaces the native tryptophan at position 144 of PLP 139-151 with leucine, and retains the native histidine at 147. It is the single-substitution counterpart to the double-substituted [Leu144, Arg147] analogue offered separately, which makes the pair useful for separating the contribution of each position. Leucine is the conservative choice at this site in a way alanine is not. It keeps a bulky hydrophobic side chain in the pocket while removing the indole ring, so a receptor that needs volume at position 144 may still be engaged while one that requires aromatic stacking is not. Analogues of this epitope that alter position 144 have been shown to change the character of the response rather than only its magnitude, with Th1 and Th2 clones recognising the autoantigenic peptide differently, so the readout of interest is often the cytokine profile rather than proliferation alone. Used alongside LT0627, which adds an arginine substitution at 147 on the same leucine-144 background, this peptide isolates what the second substitution contributes. That comparison matters because the double-substituted analogue is the one described in the literature as a receptor antagonist, and single-substitution behaviour should not be inferred from it. Establish this analogue's activity directly in the responder population under study. | 