Michler’s Ketone: A Novel Negative-Ion Matrix for Enhancing Amino Acid Detection and MALDI Tissue Imaging

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Abstract
Amino acids are essential protein components and key bioactive molecules governing metabolism and signal transduction, playing vital roles in plant growth, physiological homeostasis, immunity, and stress adaptation. Negative-ion matrices for amino acid detection in matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) remain underdeveloped, largely due to low ionization efficiency and strong background interference. To address this limitation, we developed a novel negative-ion MALDI matrix, Michler’s ketone (MK), for efficient amino acid detection and imaging. MK exhibits several superior properties as a powerful MALDI matrix, including strong UV–vis absorption at 355 nm, excellent vacuum stability, low matrix-related ion interference, and high detection efficiency for amino acids. Using MK, all 20 proteinogenic amino acids were successfully detected in the mixed standard, whereas conventional matrices, namely, 2-mercaptobenzothiazole (2-MBT) and α-cyano-4-hydroxycinnamic acid (CHCA), detected only 10 and 8 amino acids, respectively. Furthermore, MK enabled high-resolution MALDI-MSI of amino acids in Actinidia arguta tissues, allowing clear visualization of tissue-specific spatial distribution patterns. Overall, MK represents a high-performance negative-ion MALDI matrix that significantly enhances amino acid detection and imaging.
Funding Information
  • Key Research and Development Program of Zhejiang Province (2025C01135)
  • Fundamental Research Funds for the Central Universities (XJJSKYQD202609)
  • Huayi Technology Innovation Center for Study Resources (HTIC P01 RR2017001A)
  • National Sciences Foundation of China (31770384)
  • National Sciences Foundation of China (32570485)

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