Abstract
7,7,8,8-Tetracyanoquinodimethane (TCNQ) was incorporated in fully hydrated liposomes of the following pyrene-containing as well as non-labelled phospholipids: 1-palmitoyl-2-[10-(pyren-1-yl)decanoyl]- sn-glycero-3-phosphatidylcholine (PPDPC), 1-palmitoyl-2-[10-(pyren-1-yl)decanoyl]- sn-glycero-3-phosphatidyl- rac′-glycerol ( rac′-PPDPG), 1-palmitoyl-2-[10 (pyren-1-yl)decanoyl]- sn-glycero-3-phosphatidyl- sn-3′-glycerol (3′-PPDPG), 1-[10-(pyren-1-yl)decanoyl]-2-palmitoyl- sn-glycero- 3-phosphatidyl- sn-3′-glycerol (3′-PDPPG), 1-[10-pyren-1-yl)decanoyl]-2-palmitoyl- sn-glycero-3-phosphatidyl- sn-1′-glycerol (1′-PDPPG), 1,2-dipalmitoyl- sn-glycero-3-phosphatidylcholine (DPPC) and 1,2-dipalmitoyl- sn-glycero-3-phosphatidyl- rac′- glycerol ( rac′-DPPG). Lyophilized charge-transfer (CT) complexes of TCNQ with phospholipids were examined by Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS). Due to the spectral changes observed in the vibrational bands originating from the CH 2 and C= O streching vibrations, and the bands associated with the polar headgroup of the phospholipids it is evident that TCNQ has only a minor perturbing effect on the hydrocarbon chains. However, the molecular interaction between TCNQ and phospholipids is seen in the polar headgroup region. The donated electrons are most likely located on the oxygens of the phosphate group in the polar head. As judged from the present infrared data interactions of TCNQ with phosphatidylcholines (PC) and phosphatidylglycerols (PG) differ. For PG the complex formation produces a second strong C= O stretching band at approx. 1710 cm −1 in addition to the band at approx. 1735 cm −1 indicating a specific molecular interactions in the interfacial region.
Published Version
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