TY - JOUR
T1 - Fourier transform infrared spectroscopy and differential scanning calorimetry studies of fatty acid homogeneous ceramide 2
AU - Chen, Hui Chen
AU - Mendelsohn, Richard
AU - Rerek, Mark E.
AU - Moore, David J.
N1 - Funding Information:
This work was supported in part by a Public Health Service grant (GM 29864) to RM. We thank Dr. Jenifer Thewalt, Simon Fraser University, for providing the first synthetic ceramide 2 samples.
PY - 2000/9/29
Y1 - 2000/9/29
N2 - Ceramides provide a major component of the barrier function of skin. An understanding of barrier organization requires a detailed characterization of ceramide phase behavior and molecular interactions. Toward this end, Fourier transform infrared (FTIR) and differential scanning calorimetry (DSC) studies of ceramide 2 analogues (non-hydroxylated fatty acid N-acyl sphingosines) of specific chain lengths (C14, C16, C18, C20) are presented. In addition, the molecular interactions of the individual chains in each molecule are elucidated through thermotropic FTIR studies of derivatives possessing perdeuterated fatty acid chains. DSC data showed a much smaller chain length variation (for the C16, C18, C20 derivatives) in the main order-disorder transition temperature (approx. 93 ± 1°C) than is observed in the corresponding series of phosphatidylcholines, consistent with minimal ceramide hydration. The temperature dependence of the methylene stretching and scissoring modes revealed a solid-solid phase transition at 20-25°C below the main order-disorder transition accompanied by chain packing alterations from orthorhombic → hexagonal subcells. The chain packing transition was accompanied by enhanced penetration of water into the polar region. This was deduced from the temperature dependence of the amide I and II modes, which provide direct evidence for H → D exchange. The CD2 scissoring mode splitting of the deuterated fatty acid constituent of the C16, C18, C20 chains revealed preferential segregation of microdomains (3-5 chains) of this species within the orthorhombic phase. In contrast, the sphingosine base chains appeared to be sufficiently separated so as to inhibit interchain vibrational coupling between them. FTIR spectroscopy provides a convenient means for characterizing domain formation, chain packing, and hydration sites of these phases, which are highly ordered under physiological conditions. (C) 2000 Elsevier Science B.V.
AB - Ceramides provide a major component of the barrier function of skin. An understanding of barrier organization requires a detailed characterization of ceramide phase behavior and molecular interactions. Toward this end, Fourier transform infrared (FTIR) and differential scanning calorimetry (DSC) studies of ceramide 2 analogues (non-hydroxylated fatty acid N-acyl sphingosines) of specific chain lengths (C14, C16, C18, C20) are presented. In addition, the molecular interactions of the individual chains in each molecule are elucidated through thermotropic FTIR studies of derivatives possessing perdeuterated fatty acid chains. DSC data showed a much smaller chain length variation (for the C16, C18, C20 derivatives) in the main order-disorder transition temperature (approx. 93 ± 1°C) than is observed in the corresponding series of phosphatidylcholines, consistent with minimal ceramide hydration. The temperature dependence of the methylene stretching and scissoring modes revealed a solid-solid phase transition at 20-25°C below the main order-disorder transition accompanied by chain packing alterations from orthorhombic → hexagonal subcells. The chain packing transition was accompanied by enhanced penetration of water into the polar region. This was deduced from the temperature dependence of the amide I and II modes, which provide direct evidence for H → D exchange. The CD2 scissoring mode splitting of the deuterated fatty acid constituent of the C16, C18, C20 chains revealed preferential segregation of microdomains (3-5 chains) of this species within the orthorhombic phase. In contrast, the sphingosine base chains appeared to be sufficiently separated so as to inhibit interchain vibrational coupling between them. FTIR spectroscopy provides a convenient means for characterizing domain formation, chain packing, and hydration sites of these phases, which are highly ordered under physiological conditions. (C) 2000 Elsevier Science B.V.
KW - Conformational order
KW - Lipid barrier
KW - Skin
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U2 - 10.1016/S0005-2736(00)00271-6
DO - 10.1016/S0005-2736(00)00271-6
M3 - Article
C2 - 11018673
AN - SCOPUS:0034730567
VL - 1468
SP - 293
EP - 303
JO - Biochimica et Biophysica Acta - Biomembranes
JF - Biochimica et Biophysica Acta - Biomembranes
SN - 0005-2736
IS - 1-2
ER -