R. Almog et Ca. Mannella, MOLECULAR PACKING OF CORD FACTOR AND ITS INTERACTION WITH PHOSPHATIDYLINOSITOL IN MIXED MONOLAYERS, Biophysical journal, 71(6), 1996, pp. 3311-3319
Cord factor (trehalose 6,6'-dimycolate, CF) is a glycolipid located in
the outer mycobacterial cell wall that is implicated in the pathogene
sis of mycobacteria. Furthermore, CF is a convenient model for studyin
g mycolic acid residues, the major lipid constituents of the mycobacte
rial cell walt that are believed to form a barrier against drug penetr
ation. The surface properties of CF and its interactions with phosphat
idylinositol (Pt) have been investigated using the monolayer technique
. During compression/expansion/recompression cycles, CF monolayers swi
tch from a loosely packed to a more tightly packed structure. The chan
ge in surface properties suggests a molecular rearrangement, perhaps i
nvolving interdigitation of long and short chains of the CF molecules.
In CF-PI monolayers, maximal lateral packing density occurs between 0
.5 and 0.7 mote fraction CF, which is close to the relative compositio
n of mycolic acid residues and shorter-chain lipids in the mycobacteri
al cell wall. Low concentrations of CF increase the order in PI monola
yers, consistent with CF toxicity involving rigidification of cell mem
branes.