Abstract
The phase-transition temperatures of ester-linked dipalmitoylphosphatidylcholine (DPPC) and ether-linked dihexadecylphosphatidylcholine (DHPC) bilayer membranes were measured as a function of the concentration of local anesthetics, dibucaine (DC·HCl), tetracaine (TC·HCl), bupivacaine (BC·HCl), lidocaine (LC·HCl) and procaine hydrochlorides (PC·HCl). The temperature of the main transition for both lipid bilayers was depressed by all the anesthetics added in a dose-dependent manner; the order of the depression of transition temperature was DC·HCl>TC·HCl>BC·HCl>LC·HCl>PC·HCl. The pretransition temperature of DPPC bilayer membrane from the lamellar gel ( L β ′) to the ripple gel ( P β ′) phase was depressed by the addition of local anesthetics, while the DHPC bilayer membrane undergoes the pretransition from the interdigitated gel ( L β I) to the P β ′ phase and the elevation of pretransition temperature was observed by the addition of local anesthetics. The presence of local anesthetics stabilize the L β I phase of lipid bilayer membranes. When the more hydrophobic anesthetics such as DC·HCl and TC·HCl were added sufficiently to the bilayer membrane system, the interdigitation of bilayers was induced in the DPPC membrane system and the P β ′ phase disappeared in the DHPC membrane system. From the colligative thermodynamic framework, three kinds of differential partition coefficients corresponding to three phase-transitions, K( L α )– K( P β ′), K( P β ′)– K( L β ′) and K( P β ′)– K( L β I), where K( L α ), K( P β ′), K( L β ′) and K( L β I) refer to the partition coefficients of an anesthetic into the L α , P β ′, L β ′ and L β I phases of lipid bilayer membranes, were evaluated from the depression (or elevation) of the phase-transition temperature. The transfer free energy of anesthetics from the aqueous phase to the L α phase of bilayers, Δ G tr ∘=− RTln K( L α ), was well correlated to the local anesthetic potencies.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.