Temperature dependence of the Langmuir monolayer packing of mycolic acids from Mycobacterium tuberculosis.
Phase diagrams of the Langmuir monolayer of dicyclopropyl alpha mycolic acid (alpha-MA), cyclopropyl methoxy mycolic acid (MeO-MA), and cyclopropyl ketomycolic acids (Keto-MA) from Mycobacterium tuberculosis were obtained by thermodynamic analysis of the surface pressure (pi) vs. average molecular area (A) isotherms at temperatures in the range of 10-46 degrees C. The Langmuir monolayers of MAs were shown to exhibit various phases depending on the temperature (T) and the pi values. In the Langmuir monolayer of Keto-MA, the carbonyl group in the meromycolate chain apparently touches the water surface to give the molecule a W-shape in all the temperatures and surface pressures studied. Keto-MA formed a rigid solid condensed film, with four hydrocarbon chains packing together, not observed in the others. In contrast, the monolayer films of alpha-and MeO-MAs having no such highly hydrophilic intra-chain groups in the meromycolate chain were mostly in liquid condensed phase. This novel insight into the packing of mycolic acids opens up new avenues for the study of the role of mycolic acids in the mycobacterial cell envelopes and pathogenic processes.
Villeneuve
Masumi
M
Department of Chemistry, Faculty of Science, Saitama University, 255 Shimo-okubo, Saitama 338-8570, Japan. villeneuve@chem.saitama-u.ac.jp
Kawai
Mizuo
M
Kanashima
Hideki
H
Watanabe
Motoko
M
Minnikin
David E
DE
Nakahara
Hiroo
H
D018625:Microscopy, Atomic Force; D009169:Mycobacterium tuberculosis / Q000737:chemistry*; D009171:Mycolic Acids / Q000737:chemistry*; D013499:Surface Properties; D013696:Temperature
D009171:Mycolic Acids