OBJECTS AND METHODS: DPSO exhibit a noticeable structure making effect on the water structure and acts as a cryoprotective at low concentrations; on the contrary, at higher concentrations, it acts as a disruptor on the cellular structures and the toxic effects prevail. To explain the observed behaviour and correlate it with the hydrophobic/hydrophilic properties of DPSO, we studied by means of Differential Scanning Calorimetry (DSC) the hydrated multilamellar liposomes of both Dimyristoyl phosphatidylcholine (DMPC) and Dipalmitoyl phosphatidylcholine (DPPC) in the presence of increasing amounts of DPSO. Liposomes were prepared by mixing the appropriate amount of DPSO to both lipids up to a final lipid concentration of about 20 % w/w; DSC (Metler-Toledo TA-STAR 821e calorimeter) scans were performed at a heating rate of 2.0°C/min. RESULTS AND CONCLUSIONS: The behaviour we found in the presence of DPSO suggest the existence of strong hydrophobic interactions involving the n-propyl chains and that their able also to penetrate, at least in a certain extent, into the hydrophobic core of the lipid bilayer. That is confirmed from the disappearance of the pretransition, together with the diminution of the Tm at the lower DPSO presence, more evidenced in the DMPC liposomes than in DPPC. Moreover, also the polar interaction due to the polar S=O group appears to play a role, as is suggested from the Tm increase found at the higher DPSO contents. This behaviour suggest that the bilayer rigidifies in the presence of DPSO, as a consequence of the substitution of water with DPSO molecules interacting with the polar heads, and that occurs is in a greater extent in the presence of DPPC. Even the ?H behaviour, decreasing noticeably at the higher DPSO presence, loading to zero in the DMPC systems confirms the prevalent role of the hydrophobic interactions. Indeed, as ?DPSO = 0,2 the DMPC bilayer is totally solubilized, confirming the destructurizing effect of biomembranes of DPSO. Also the role of the length of the lipidic chains is well evidenced, indeed in the DPPC liposomes the bilayer structure is confirmed at any DPSO concentration, in a similar manner to it has been reported in the presence of DMSO, even at lower ?H; on the contrary in the DMPC liposomes the solubilizing power of DPSO prevail in the systems in which the H2O/DPSO ratio range from 60 to 40 % w/w, concentrations at which the cryoprotective effect of DMSO (and of DESO) reaches its maximum.

Di-n-propylsulfoxide (DPSO) effect on the thermal transitions of liposomes

A Torreggiani
2006

Abstract

OBJECTS AND METHODS: DPSO exhibit a noticeable structure making effect on the water structure and acts as a cryoprotective at low concentrations; on the contrary, at higher concentrations, it acts as a disruptor on the cellular structures and the toxic effects prevail. To explain the observed behaviour and correlate it with the hydrophobic/hydrophilic properties of DPSO, we studied by means of Differential Scanning Calorimetry (DSC) the hydrated multilamellar liposomes of both Dimyristoyl phosphatidylcholine (DMPC) and Dipalmitoyl phosphatidylcholine (DPPC) in the presence of increasing amounts of DPSO. Liposomes were prepared by mixing the appropriate amount of DPSO to both lipids up to a final lipid concentration of about 20 % w/w; DSC (Metler-Toledo TA-STAR 821e calorimeter) scans were performed at a heating rate of 2.0°C/min. RESULTS AND CONCLUSIONS: The behaviour we found in the presence of DPSO suggest the existence of strong hydrophobic interactions involving the n-propyl chains and that their able also to penetrate, at least in a certain extent, into the hydrophobic core of the lipid bilayer. That is confirmed from the disappearance of the pretransition, together with the diminution of the Tm at the lower DPSO presence, more evidenced in the DMPC liposomes than in DPPC. Moreover, also the polar interaction due to the polar S=O group appears to play a role, as is suggested from the Tm increase found at the higher DPSO contents. This behaviour suggest that the bilayer rigidifies in the presence of DPSO, as a consequence of the substitution of water with DPSO molecules interacting with the polar heads, and that occurs is in a greater extent in the presence of DPPC. Even the ?H behaviour, decreasing noticeably at the higher DPSO presence, loading to zero in the DMPC systems confirms the prevalent role of the hydrophobic interactions. Indeed, as ?DPSO = 0,2 the DMPC bilayer is totally solubilized, confirming the destructurizing effect of biomembranes of DPSO. Also the role of the length of the lipidic chains is well evidenced, indeed in the DPPC liposomes the bilayer structure is confirmed at any DPSO concentration, in a similar manner to it has been reported in the presence of DMSO, even at lower ?H; on the contrary in the DMPC liposomes the solubilizing power of DPSO prevail in the systems in which the H2O/DPSO ratio range from 60 to 40 % w/w, concentrations at which the cryoprotective effect of DMSO (and of DESO) reaches its maximum.
2006
Istituto per la Sintesi Organica e la Fotoreattivita' - ISOF
DPSO
hydrated multilamellar liposomes
DSC
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.14243/62610
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