Roles of α-Methyl trans-Cyclopropane Groups in Behavior of Mixed Mycolic Acid Monolayers

Publication date: Available online 8 November 2018Source: Biochimica et Biophysica Acta (BBA) - BiomembranesAuthor(s): Masumi Villeneuve, Hiroki NoguchiAbstractMixed Langmuir films of type 1 alpha- (α-) and keto-mycolic acids (MAs) were investigated to understand the roles of α-methyl trans-cyclopropane containing keto-MA in determining the physical and chemical properties of the monolayers. Surface pressure (π) vs. mean molecular area (A) isotherms were measured at constant mole fractions defined as the ratio of the keto-MA molarity to the total molarity of α-MA and keto-MA (Xketo) at 25 °C and 37 °C. A and the elastic modulus (E) of the mixed monolayer were compared for different Xketo at fixed π values. In keto-MA rich monolayers, A values were much larger than values the combined areas of α-MA and keto-MA, while the E values were close to those of solid keto-MA monolayers. A and E were also plotted against the mole fraction of α-methyl trans-cyclopropane containing keto-MA, which showed that the α-methyl trans-cyclopropane group stabilized the W-form conformation of mycolic acids in monolayers, and rendered them solids. Furthermore, a comparison of the experimental results and the α-methyl trans-cyclopropane content in cell-wall MAs from various strains indicated that the ratio of trans-cyclopropane content was important in determining the nature of the mixed MA layer.Graphical Abstract
Source: Biochimica et Biophysica Acta (BBA) Biomembranes - Category: Biochemistry Source Type: research
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