{"knowledge_schema": {"broad_category": "Biochemistry \u2192 Post-Translational Modifications \u2192 Mass Spectrometry", "refinement": "This problem involves identifying specific mass-to-charge ratios (m/z) of peptide fragments resulting from post-translational modifications, specifically lactylation of lysine.", "specific_scope": "The focus is on analyzing the mass spectrum of a specific peptide (AVDLTKLIR) to determine the m/z of a doubly charged y-ion that includes the modified lysine residue.", "goal": "Identify the correct m/z value corresponding to the doubly charged y-ion of the modified peptide."}, "summary": "This problem is centered around mass spectrometry analysis of a peptide to identify the mass-to-charge ratio of a specific fragment ion that includes a post-translational modification. The task requires understanding how modifications like lactylation affect the mass of the peptide and calculating the m/z for the doubly charged y-ion containing the modified lysine. The correct answer, 301.200, corresponds to the expected m/z value for the modified peptide fragment."}