Interactions of cyclic AMP and its dibutyryl analogue with model membrane: X-ray diffraction and Raman spectroscopic study using cubic liquid–crystalline phases of monoolein

Interactions of Cyclic AMP and Its Dibutyryl Analogue with a Lipid Layer in the Aqueous Mixtures of Monoolein Preparation and Dioleoyl Phosphatidylcholine as Probed by X-Ray Diffraction and Raman Spectroscopy

“…However, using the digital difference spectra shown by traces 4 in Figures 3 and 4 (the spectrum of the nucleotide-containing sample minus the spectrum of the reference liquid-crystalline phase, satisfying a criterion of zero intensity of the C=C stretching vibration band at 1655 cm −1 ), we were able to retrieve a number of bands that are attributable to the entrapped cyclic nucleotides. As it has been shown previously [2], the comparison of these difference spectra with the spectra of nucleotides in water (traces 3 in Figures 3 and 4) is particularly useful for detecting the interactions of nucleotides with model lipid membrane.…”

“…As mentioned in the introduction, these nucleotides affect the cubic Pn3m phase of aqueous MO in an analogous fashion [2].…”

“…Excitation, 514.5 nm. Integration time, 4 s. Three scans were co-added for spectra (1) and (2). Four scans were co-added for spectrum (3).…”

“…3 wt.% content) induces the intercubic Pn3m → Ia3d phase transition. Different effects of the MO phase matrix on the Raman shifts of the adenine and phosphate vibrational modes have enabled us to conclude that dbcAMP associates with MO bilayer, whereas the cAMP molecules for the most part remain in the water channels of the cubic phase [2].…”

“…In an attempt to understand the factors which govern differences in the membrane permeability of these two cyclic nucleotides, we have investigated previously [2] the interactions of cAMP and dbcAMP with the lipid bilayer of monoolein (MO; as indicated below, 1-monooleoyl glycerol constitutes the greater part of MO, Figure1) by using small-angle X-ray diffraction (SAXD) and Raman spectroscopy methods. In that study, among several liquid-crystalline phases of aqueous MO [3], the reversed bicontinuous cubic phase of space group type Pn3m had been selected as a bilayer-based model system for some reasons.…”