Structural analyses and triacylglycerol polymorphs with FT-IR techniques. 2. β′1-form of 1,2-dipalmitoyl-3-myristoyl-sn-glycerol

Junko Yano, Fumitoshi Kaneko, Masamichi Kobayashi, Dharma R. Kodali, Donald M. Small, Kiyotaka Sato

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Abstract

On the basis of the assignments of the methylene wagging bands described in the preceding paper (Part 1), FT-IR studies have been applied to the β′1-form of 1,2-dipalmitoyl-3-myristoyl-sn-glycrerol (PPM). PPM has the most stable form of β′-type, in contrast to ordinary triacylglycerols, which have the most stable form of β-type. The degrees of inclination of the acyl chains with respect to the lamellar interface were determined by two FT-IR techniques of attenuated total reflection and oblique transmission. The acyl chains were packed in orthorhombic perpendicular (O) subcell as revealed in the absorption spectra of polymethylene scissoring and rocking modes. As for the acyl chain conformation, it was found that a palmitoyl chain and a myristoyl chain extend to form an all-trans conformation, while the second palmitoyl chain takes a bent conformation in the neighborhood of the ester bond. The acyl chain axis tilts against both the as- and the bs-axis of the O subcell, yet the degree of inclination against the bs-axis is slightly larger than that against the as-axis. The as-axis is inclined unidirectionally, while the bs-axis is alternately inclined along the successive layer.

Original languageEnglish (US)
Pages (from-to)8120-8128
Number of pages9
JournalJournal of Physical Chemistry B
Volume101
Issue number41
DOIs
StatePublished - Oct 9 1997

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