The following specific configurations were utilized to produce the selected proteins: ProteinMPNN Settings: ● Model Version: v_48_020 (Standard backbone noise model). ● Sampling Temperature: 0.2. ○ Rationale: A low sampling temperature was explicitly chosen to prioritize high-probability, low-perplexity sequences. In the context of "fixing" a flexible region rather than de novo function generation, low temperature ensures the recovery of the most thermodynamically stable residues compatible with the backbone, minimizing the risk of misfolding. ● Backbone Noise: 0.02 Angstroms. ○ Rationale: Introduces slight coordinate perturbation during inference to ensure the predicted sequence is robust to minor structural fluctuations typical of dynamic proteins. ● Design constraints: ○ fixed_residues: Residues 41-167 (containing L124A, D62Q, Q130L, V167L). ○ designed_residues: Residues 31-44. Structural Fusion Parameters: ● Linker Sequence: Rigid Alpha-helical linker, specifically AEAAAKEAAAKA or similar variations designed to maintain a stiff, rod-like connection. ● Foldon Sequence: GYIPEAPRDGQAYVRKDGEWVLLSTFL. ● Stoichiometry: 1:1:1 fusion (RBD:Linker:Foldon) resulting in a homotrimeric assembly.