Dielectric Properties of Phosphatidylcholine Membranes and the Effect of Sugars.

Victoria Vitkova,Georgi Popkirov,Ognyan Petkov,Krassimira Antonova,Vesela Yordanova,Galya Staneva,Angelina Stoyanova-Ivanova

doi:10.3390/membranes11110847

Abstract

Simple carbohydrates are associated with the enhanced risk of cardiovascular disease and adverse changes in lipoproteins in the organism. Conversely, sugars are known to exert a stabilizing effect on biological membranes, and this effect is widely exploited in medicine and industry for cryopreservation of tissues and materials. In view of elucidating molecular mechanisms involved in the interaction of mono- and disaccharides with biomimetic lipid systems, we study the alteration of dielectric properties, the degree of hydration, and the rotational order parameter and dipole potential of lipid bilayers in the presence of sugars. Frequency-dependent deformation of cell-size unilamellar lipid vesicles in alternating electric fields and fast Fourier transform electrochemical impedance spectroscopy are applied to measure the specific capacitance of phosphatidylcholine lipid bilayers in sucrose, glucose and fructose aqueous solutions. Alteration of membrane specific capacitance is reported in sucrose solutions, while preservation of membrane dielectric properties is established in the presence of glucose and fructose. We address the effect of sugars on the hydration and the rotational order parameter for 1-palmitoyl-2-oleoyl-sn-glycero-3- phosphocholine (POPC) and 1-stearoyl-2-oleoyl-sn-glycero-3- phosphocholine (SOPC). An increased degree of lipid packing is reported in sucrose solutions. The obtained results provide evidence that some small carbohydrates are able to change membrane dielectric properties, structure, and order related to membrane homeostasis. The reported data are also relevant to future developments based on the response of lipid bilayers to external physical stimuli such as electric fields and temperature changes.

Highlights

The biological significance of carbohydrate molecules and developments of their biomedical and industrial applications have stimulated intensive research toward gaining knowledge of the alteration of membrane physicochemical properties by the presence of sugars
The values obtained fo brane specific capacitance together with the error calculated from the fit of our mental data for every sugar concentration are summarized in Table 1 and Figure For each sugar concentration, we measure the transition frequency f
Membrane capacitance serves as a single fitting parameter sults show no alteration of the specific capacitance of POPC bilayers in aqueous s of glucose and fructose at concentrations of up to 300 mmol/L and in the prese mmol/L NaCl

Summary

Introduction

The biological significance of carbohydrate molecules and developments of their biomedical and industrial applications have stimulated intensive research toward gaining knowledge of the alteration of membrane physicochemical properties by the presence of sugars. The cryoprotective efficiency of sugars is related to the molecular mechanisms of their interaction with lipid membranes. Simple carbohydrates (mono- and disaccharides) are found to exert a protective role against abnormal temperatures and dehydration in biomembranes and synthetic lipid bilayers [6]. Some disaccharides such as trehalose and sucrose are identified as efficient cryoprotectants counteracting the water deficiency via replacement of water molecules at the membrane surface [1,7,8]. Data acquired for mechanical properties of bilayer lipid stacks [9,10] and free-standing lipid membranes [11,12,13] in the presence of mono- and disaccharides outline a more complex picture on sugar–membrane interactions

Methods

Results

Discussion

Conclusion