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Title: STABILIZATION OF MEMBRANES BY OLIGOSACCHARIDES IN THE DRY STATE: STRUCTURAL AND FUNCTIONAL INVESTIGATIONS.

Author
item CACELA, CONSTANCA - MAX PLANK INST.,GERMANY
item Livingston, David
item FUTHER, ELLEN - MAX PLANK INST.,GERMANY
item MEYER, ARND - MAX PLANK INST.,GERMANY
item MINCHA, DIRK - MAX PLANK INST.,GERMANY

Submitted to: Gordon Research Conference Proceedings
Publication Type: Other
Publication Acceptance Date: 6/10/2003
Publication Date: 6/30/2003
Citation: CACELA, C., LIVINGSTON, D.P., FUTHER, E., MEYER, A.G., MINCHA, D.K. STABILIZATION OF MEMBRANES BY OLIGOSACCHARIDES IN THE DRY STATE: STRUCTURAL AND FUNCTIONAL INVESTIGATIONS.. GORDON RESEARCH CONFERENCE PROCEEDINGS. 2003.

Interpretive Summary: Sugars have been implicated as cellular protectants under stress conditions in many organisms from bacteria to higher plants and animals. They have been described as "chemical chaperones" for soluble proteins and as stabilizers of membrane structure and function. While the effects of disaccharides such as sucrose and trehalose have been studied extensively, there is only little known about the effects of oligosaccharides, that are often synthesized by plants specifically under stress conditions such as drought or cold. We have therefore started a systematic investigation into the ability of different structural families of oligosaccharides to protect model lipid vesicles (liposomes) during drying. So far we have investigated malto-oligosaccharides and fructo-oligosaccharides (inulins) [1,2], and raffinose family oligosaccharides [3]. The effects of the different oligosaccharides on liposome stability were assessed by leakage and membrane fusion experiments. The existence of direct interactions between sugars and lipids in the dry state and the influence on lipid phase transitions were studied by Fourier-transform infrared (FTIR) spectroscopy. We found that in all cases the chain length of the oligosaccharides (DP=degree of polymerization) had a strong effect on their protective properties and their ability to interact with membrane lipids. The effect of DP, however, was different between the different structural families of oligosaccharides. Fructans were the only sugars that showed increased interaction with dry membranes with inceasing size. Therefore, fructans may have unique properties, which would make them ideal solutes to stabilize cells under stress conditions. In order to get more insight into fructan-membrane interactions, we have now started to study the effect of fructans isolated from oat leaves, which are structurally much more complex than inulins, in that they contain different branching isomers in every size class. Our results show that oat fructans increase in their ability to stabilize membranes in the dry state with increasing DP up to six monosaccharide units and decrease in effectiveness with higher DP. Careful analysis by FTIR will enable us to determine where different oligosaccharides bind to the lipid molecules (carbonyl, phosphate or choline group) [4] and to relate these length-dependent differences in binding to protective activity and structural characteristics of the different families of oligosaccharides.

Technical Abstract: Sugars have been implicated as cellular protectants under stress conditions in many organisms from bacteria to higher plants and animals. They have been described as "chemical chaperones" for soluble proteins and as stabilizers of membrane structure and function. While the effects of disaccharides such as sucrose and trehalose have been studied extensively, there is only little known about the effects of oligosaccharides, that are often synthesized by plants specifically under stress conditions such as drought or cold. We have therefore started a systematic investigation into the ability of different structural families of oligosaccharides to protect model lipid vesicles (liposomes) during drying. So far we have investigated malto-oligosaccharides and fructo-oligosaccharides (inulins) [1,2], and raffinose family oligosaccharides [3]. The effects of the different oligosaccharides on liposome stability were assessed by leakage and membrane fusion experiments. The existence of direct interactions between sugars and lipids in the dry state and the influence on lipid phase transitions were studied by Fourier-transform infrared (FTIR) spectroscopy. We found that in all cases the chain length of the oligosaccharides (DP=degree of polymerization) had a strong effect on their protective properties and their ability to interact with membrane lipids. The effect of DP, however, was different between the different structural families of oligosaccharides. Fructans were the only sugars that showed increased interaction with dry membranes with inceasing size. Therefore, fructans may have unique properties, which would make them ideal solutes to stabilize cells under stress conditions. In order to get more insight into fructan-membrane interactions, we have now started to study the effect of fructans isolated from oat leaves, which are structurally much more complex than inulins, in that they contain different branching isomers in every size class. Our results show that oat fructans increase in their ability to stabilize membranes in the dry state with increasing DP up to six monosaccharide units and decrease in effectiveness with higher DP. Careful analysis by FTIR will enable us to determine where different oligosaccharides bind to the lipid molecules (carbonyl, phosphate or choline group) [4] and to relate these length-dependent differences in binding to protective activity and structural characteristics of the different families of oligosaccharides.