TY - JOUR
T1 - Structural Determinants of Miscibility in Surface Films of Galactosylceramide and Phosphatidylcholine
T2 - Effect of Unsaturation in the Galactosylceramide Acyl Chain
AU - Ali, Shaukat
AU - Brockman, Howard L.
AU - Brown, Rhoderick E
PY - 1991/11/1
Y1 - 1991/11/1
N2 - The Langmuir film balance technique has been used to define the surface structure and determine the mixing behavior of galactosylceramide (GalCer) and phosphatidylcholines in surface phases. To determine the effect of unsaturation on surface behavior, chain-pure GalCer species containing either oleoyl (18:1Δ9), eicosenoyl (20:1Δ11), or eicosadienoyl (20:2Δ11, 14) fatty acyl chains were synthesized. Using bovine brain GalCer as a reference, surface pressure versus molecular area (π-A) isotherms of the pure lipids were measured and analyzed by determining their compressibilities and by using an equation of state for lipid monolayers. This information, when coupled with surface potential versus molecular area (ΔV-A) analyses, provides insights into GalCer surface structure in terms of molecular packing and orientation. Lipid mixing behavior was determined by classical approaches which involve analyzing the average molecular area, the average surface dipole moment, and surface pressure as a function of film composition. The results indicate that, in contrast to the complex mixing behavior displayed by bovine brain GalCer and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), chain-pure GalCer species containing either oleoyl, eicosenoyl, or eicosadienoyl fatty acyl chains are miscible with POPC over the entire composition range. Moreover, increasing amounts of GalCer containing eicosenoyl acyl chains systematically elevate dipalmitoyl-phosphatidylcholine’s (DPPC) liquid-expanded-to-liquid-condensed transition pressure. Such behavior is consistent with GalCer being miscible with the liquid-expanded phase of DPPC. Thus, fatty acyl unsaturation is a critical parameter governing the mixing behavior of GalCer with phosphatidylcholine.
AB - The Langmuir film balance technique has been used to define the surface structure and determine the mixing behavior of galactosylceramide (GalCer) and phosphatidylcholines in surface phases. To determine the effect of unsaturation on surface behavior, chain-pure GalCer species containing either oleoyl (18:1Δ9), eicosenoyl (20:1Δ11), or eicosadienoyl (20:2Δ11, 14) fatty acyl chains were synthesized. Using bovine brain GalCer as a reference, surface pressure versus molecular area (π-A) isotherms of the pure lipids were measured and analyzed by determining their compressibilities and by using an equation of state for lipid monolayers. This information, when coupled with surface potential versus molecular area (ΔV-A) analyses, provides insights into GalCer surface structure in terms of molecular packing and orientation. Lipid mixing behavior was determined by classical approaches which involve analyzing the average molecular area, the average surface dipole moment, and surface pressure as a function of film composition. The results indicate that, in contrast to the complex mixing behavior displayed by bovine brain GalCer and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), chain-pure GalCer species containing either oleoyl, eicosenoyl, or eicosadienoyl fatty acyl chains are miscible with POPC over the entire composition range. Moreover, increasing amounts of GalCer containing eicosenoyl acyl chains systematically elevate dipalmitoyl-phosphatidylcholine’s (DPPC) liquid-expanded-to-liquid-condensed transition pressure. Such behavior is consistent with GalCer being miscible with the liquid-expanded phase of DPPC. Thus, fatty acyl unsaturation is a critical parameter governing the mixing behavior of GalCer with phosphatidylcholine.
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U2 - 10.1021/bi00111a002
DO - 10.1021/bi00111a002
M3 - Article
C2 - 1958657
AN - SCOPUS:0026341957
SN - 0006-2960
VL - 30
SP - 11198
EP - 11205
JO - Biochemistry
JF - Biochemistry
IS - 47
ER -