THE EFFECT OF ACIDS ON THE INFRARED SPECTRA OF SCHIFF BASES—II. IMINES CONTAINING THE C=C-C=N AND C=C-C=C-C=N UNITS

Abstract— The Fourier-transform infrared spectra of chloroform-d solutions of conjugated imines CH₃CH=CHCH=NCH(CH₃)₂ and CH₃CH₂CH=CHCH=CHCH=NCH(CH₃)₂ and the related protonated species with HCl, HBr, HI, trichloro, dichloro, monobromo and monochloroacetic acids or propionic acid are presented. The effects of conjugation and protonation are examined. The results show that conjugation slightly increases the basicity of the Schiff bases. HCl, HBr and HI protonate the Schiff bases completely. The carboxylic acids protonate partially depending on their p K _a, values. When the Schiff base contains two (or more) C=C bonds conjugated with C=N, the main C=C stretching band undergoes a strong intensification showing that sizeable dipole moment variations occur along the conjugated chain.     

Novel benzanthrone aminoderivatives for membrane studies

The potential of novel benzanthrone aminoderivatives to trace the changes in physicochemical properties of lipid bilayer has been evaluated. Binding of the dyes to the lipid bilayers composed of zwitterionic phospholipid phosphatidylcholine (PC) and its mixtures with anionic phospholipid cardiolipin (CL) and cholesterol (Chol) was followed by significant quantum yield increase with small blue shift of emission maximum. Analysis of partition coefficients of the dyes under study showed that all aminobenzanthrones possess high lipid-associating ability. The dyes A8 and AM2 proved to be sensitive to the variations in membrane chemical composition responding to the changes in bilayer hydration induced by CL and Chol.     

Location of Novel Benzanthrone Dyes in Model Membranes as Revealed by Resonance Energy Transfer

Förster resonance energy transfer (FRET) between anthrylvinyl-labeled phosphatidylcholine (AV-PC) as a donor and newly synthesized benzanthrones (referred to here as A8, A6, AM12, AM15 and AM18) as acceptors has been examined to gain insight into molecular level details of the interactions between benzanthrone dyes and model lipid membranes composed of zwitterionic lipid phosphatidylcholine and its mixtures with anionic lipids cardiolipin (CL) and phosphatidylglycerol (PG). FRET data were quantitatively analyzed in terms of the model of energy transfer in two-dimensional systems taking into account the distance dependence of orientation factor. Evidence for A8 location in phospholipid headgroup region has been obtained. Inclusion of CL and PG into PC bilayer has been found to induce substantial relocation of A6, AM12, AM15 and AM18 from hydrophobic membrane core to lipid-water interface.