Kj. Stine et al., FLUORESCENCE MICROSCOPY STUDY OF LANGMUIR MONOLAYERS OF RACEMIC AND ENANTIOMERIC N-STEAROYLTYROSINE, Chemistry and physics of lipids, 69(1), 1994, pp. 41-50
Monolayers of N-stearoyltyrosine have been investigated by fluorescenc
e microscopy and surface pressure measurements. The racemic films are
more condensed than the enantiomeric films, indicating heterochiral di
scrimination. The surface pressure at the transition to the condensed
phase on compression decreases monotonically between X(D)= 0 and X(D)
= 0.5 at 33 degrees C. The condensed-phase domains of the monolayer of
the pure L enantiomer appear as anisotropic shapes under a fluorescen
ce microscope. The condensed-phase domains of the racemic monolayer ap
pear more compact at lower temperatures, but their morphology becomes
progressively more anisotropic as the temperature increases. The diffe
rence between the surface pressure isotherm of the enantiomeric L and
the racemic film are smaller and homochiral for the N-stearoyltyrosine
methyl ester on a pH 7 buffered subphase than for the N-stearoyltyros
ine on a pH 2 HCl acidified subphase at 22 degrees C, indicating the i
mportance of hydrogen bonding in accounting for the origin of the chir
al discrimination.