Incommensurate lamellar phase from long chain Mannosides: Investigation by X-Ray scattering and Replica Exchange Molecular Dynamics (REMD)

• Main Authors: Nguan, Hockseng, Martinez-Felipe, Alfonso, Hashim, Rauzah, Ishak, Khairul Anwar, Mat Zahid, Noor Idayu, Aripin, Nurul Fadhilah Kamalul
• Format: Article
• Published: Elsevier 2022
• Subjects: QD Chemistry
• Online Access: http://eprints.um.edu.my/42906/

We report the synthesis and phase behaviour of two anhydrous mannosides (alpha ManC(18) and alpha ManC(18:1)) with stearyl and monounsaturated oleyl hydrocarbon chains that can be obtained from vegetable sources. These mannosides have been characterised by differential scanning calorimetry, polarised optical microscopy and small- and wide-angle X-ray scattering. The two compounds exhibited multiple d-spacing bilayer structures. alpha ManC(18:1) gives a distinct incommensurate lamellar that persists until high temperature. On the other hand, alpha ManC(18) forms an incommensurate gel phase only at low temperature but undergoes a transition into the lamellar (L-alpha) liquid crystal phases on heating. The results were confirmed by replica exchange molecular dynamics (REMD). The average hydrocarbon chain/headgroup tilt angles phi /theta , and average chain bending angle psi were calculated for the simulated bilayer systems at similar to 25 degrees C. The multiple averaged headgroup tilt angles theta explain the observed incommensurate bilayer structures with different bilayer thicknesses in these long hydrocarbon chain of mannosides. Moreover, different tilting angles of the headgroup result in different surface areas per lipid. Relating the incommensurate phase properly to molecular parameters is important especially in multi-component membranes, where the interplay of different molecule types is difficult to predict on intuitive grounds. (C) 2022 Elsevier B.V. All rights reserved.