Characterization of phthiocerol and phthiodiolone dimycocerosate esters of M. tuberculosis by multiple-stage linear ion-trap MS

Area of Science:

• Lipidomics
• Mass Spectrometry
• Mycobacterial Cell Wall Biology

Background:

• Phthiocerol/phthiodiolone dimycocerosates (PDIMs) are crucial virulent lipids in pathogenic mycobacteria cell walls.
• These lipids contribute to the complex high-molecular-mass lipid profile of mycobacteria.
• Understanding PDIM structure is vital for studying mycobacterial pathogenesis.

Purpose of the Study:

• To develop and apply a linear ion-trap MS(n) mass spectrometric approach for detailed structural analysis of PDIMs.
• To elucidate the complex structures of PDIMs in Mycobacterium tuberculosis biofilms.
• To differentiate between phthiocerol and phthiodiolone lipid families and identify mycocerosic acid substituents.

Main Methods:

• Electrospray ionization (ESI) of PDIMs to form [M + Li](+) and [M + NH(4)](+) ions.
• Application of a charge-switch strategy converting mycocerosic acid substituents to N-(4-aminomethylphenyl) pyridinium (AMPP) derivatives after alkaline hydrolysis.
• Analysis of AMPP derivatives as M (+) ions using linear ion-trap MS(n) for structural elucidation.

Main Results:

• Successful desorption of PDIMs as [M + Li](+) and [M + NH(4)](+) ions.
• Characterization of mycocerosic acid substituents as AMPP derivatives.
• Comprehensive structural information obtained, including backbones and methyl side chain locations, enabling differentiation of lipid families.

Conclusions:

• The described MS(n) approach provides a powerful tool for the complete structural identification of complex PDIMs.
• This method facilitates the study of PDIMs in Mycobacterium tuberculosis biofilms.
• The strategy allows for detailed characterization of lipid backbones and diverse mycocerosic acid substituents.