Laval F, Lanéelle M A, Déon C, Monsarrat B, Daffé M
Institut de Pharmacologie et Biologie Structurale du Centre National de la Recherche Scientifique et Université Paul Sabatier, UMR 5089, Toulouse, France.
Anal Chem. 2001 Sep 15;73(18):4537-44. doi: 10.1021/ac0105181.
Mycolic acids, major and specific long-chain fatty (C70-C90) acid components of the mycobacterial cell envelope, were analyzed for the first time using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry operating in a reflectron mode. The various types of purified mycolates from representative mycobacterial species were analyzed using 2,5-DHB as matrix, because less than 10 pmol of mycolates was sufficient to obtain well-resolved mass spectra composed exclusively of pseudomolecular [M + Na]+ ions consistent with the structures deduced from the chemical analytical techniques applied to these molecules. Examination of the MALDI mass spectra demonstrated that the chain lengths of the various mycolates correlated with the growth rate of mycobacterial strains. Although slow growers, such as Mycobacterium tuberculosis and Mycobacterium ulcerans, produced a series of odd carbon numbers (C74-C82) of alpha-mycolic acids, rapid growers synthesized both odd and even carbon numbers. In addition, the main chain of oxygenated mycolic acids from slow growers were four to six carbon atoms longer than the corresponding alpha-mycolic acids, whereas rapid growers elaborated oxygenated homologues possessing the same chain lengths as their alpha-mycolic acids. Furthermore, a comparative analysis of the crude fatty acid mixtures from a wild-type strain of M. tuberculosis and its isogenic mutant effected in the synthesis of oxygenated mycolates by MALDI mass spectrometry revealed structural differences between the alpha-mycolates from the two strains. Thus, this technique appeared to be a rapid and highly sensitive technique for the analysis of mycolic acids, not only by providing accurate molecular masses and new structural information, but also by both reducing sample consumption and saving time.
分枝菌酸是分枝杆菌细胞壁的主要且特定的长链脂肪酸（C70 - C90）成分，首次使用在反射模式下运行的基质辅助激光解吸/电离飞行时间（MALDI - TOF）质谱进行分析。使用2,5 - 二羟基苯甲酸（2,5 - DHB）作为基质，对来自代表性分枝杆菌物种的各种纯化分枝菌酸进行分析，因为少于10皮摩尔的分枝菌酸就足以获得分辨率良好的质谱图，该质谱图仅由与应用于这些分子的化学分析技术推导的结构一致的假分子[M + Na]+离子组成。对MALDI质谱的检查表明，各种分枝菌酸的链长与分枝杆菌菌株的生长速率相关。虽然生长缓慢的菌株，如结核分枝杆菌和溃疡分枝杆菌，产生一系列奇数碳数（C74 - C82）的α - 分枝菌酸，但生长迅速的菌株则合成奇数和偶数碳数的分枝菌酸。此外，生长缓慢的菌株中含氧分枝菌酸的主链比相应的α - 分枝菌酸长四至六个碳原子，而生长迅速的菌株则产生与其α - 分枝菌酸链长相同的含氧同系物。此外，通过MALDI质谱对结核分枝杆菌野生型菌株及其在含氧分枝菌酸合成中发生突变的同基因突变体的粗脂肪酸混合物进行比较分析，揭示了这两种菌株的α - 分枝菌酸之间的结构差异。因此，该技术似乎是一种快速且高度灵敏的分枝菌酸分析技术，不仅能提供准确的分子量和新的结构信息，还能减少样品消耗并节省时间。
