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The effects of tricylic antidepressant clomipramine (CLO) on the membrane properties of saturated dimyristoyl phosphatidylcholine and dipalmitoyl phosphatidylcholine as well as on unsaturated egg yolk phosphatidylcholine liposomes were investigated by the electron paramagnetic resonance spin-labeling technique, in combination with the simulation of the spectra, taking into account that the membrane is heterogeneous and composed of the regions with different fluidity characteristics. Different spin labels, monitoring membrane properties in the upper and inner parts of the membrane, were used. In general, two spectral components, having different motional characteristics, were detected in all liposomes investigated. In liposomes with saturated chains, CLO decreased the phase-transition temperature, disordered the membrane, and increased polarity in the upper part of the membrane. However, less impact was observed in liposomes with unsaturated chains. In dipalmitoyl phosphatidylcholine liposomes, it also induced molecular rearrangements near the pretransition temperature. The presence of 30 mol% cholesterol increased the fluidizing effect of CLO and modified the lateral diffusion of nitroxide in the inner part of the membrane. A unique anomalous increase in diffusion of nitroxide, dependent on CLO concentration, was detected in the temperature region where the phosphatidylcholine membrane without cholesterol experiences the phase transitions. Since the changes in the central part of the membrane were even more pronounced than in the upper part of the membrane, it could be concluded that CLO incorporates into the membrane with its hydrophobic ring parallel to the phospholipid chains.

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In this study, the electron paramagnetic resonance (EPR) spin probe technique is applied as a detection method in the differentiation of irradiated and unirradiated wheat seeds. Two wheat cultivars, Kunduru and Bezostaya, were used. Aqueous solutions of 4‐hydroxy‐TEMPO (TANOL) spin probe prepared with a line‐broadening agent, potassium ferricyanide, were used in all experiments. The EPR spectra of the samples were recorded against time. A decrease in the signal intensity and a change in the shape of the intensity‐time curve (rehydration curve) were observed, depending on the applied level of irradiation. The ratio of the lipid and aqueous regions at the high field (mI = ‐1) line changes, depending on the dose of irradiation.

The interaction of antidepressant drug trazodone hydrochloride (TRZ) with dipalmitoyl phosphatidylcholine (DPPC) multilamellar liposomes (MLVs) in the presence and absence of cholesterol (CHO) was investigated as a function of temperature by using Electron Paramagnetic Resonance (EPR) spin labeling, Fourier Transform Infrared (FTIR) Spectroscopy and Differential Scanning Calorimetry (DSC) techniques. These interactions were also examined for dimyristoyl phosphatidylcholine (DMPC) multilamellar liposomes by using Electron Paramagnetic Resonance (EPR) spin labeling technique. In the EPR spin labeling studies, 5- and 16-doxyl stearic acid (5-DS and 16-DS) spin labels were used to monitor the head group and alkyl chain region of phospholipids respectively. The results indicated that TRZ incorporation causes changes in the physical properties of PC liposomes by decreasing the main phase transition temperature, abolishing the pre-transition, broadening the phase transition profile, and disordering the system around the head group region. The interaction of TRZ with unilamellar (LUV) DPPC liposomes was also examined. The most pronounced effect of TRZ on DPPC LUVs was observed as the further decrease of main phase transition temperature in comparison with DPPC MLVs. The mentioned changes in lipid structure and dynamics caused by TRZ may modulate the biophysical activity of membrane associated receptors and in turn the pharmacological action of TRZ.

Residual dipolar splittings in I3C cross-polarization magic-angle spinning spectra arising from coupling to chlorine nuclei are reported for the three chloroacetanilide isomers, using several spectrometers. At medium to high magnetic field doublets are seen for C-CI carbon resonances. Perturbation theory explains the appearance of the spectra qualitatively but is inadequate quantitatively.KEY WORDS Solid-state NMR Carbon-I 3 Magic-angle spinning Residual dipolar splittings Second-order quadrupolar effects Carbon-chlorine interactions

The fast decay of free radicals makes application of traditional electron paramagnetic resonance (EPR) techniques impractical for detection of irradiated wheats when the storage time is longer than 30 days. In this study, therefore, the effects of irradiation on wheat seeds were investigated by using the EPR spin probe technique. The technique is based on the ability of the spin probes to transfer valuable information related to the changes in the structural characteristics of embryo cell membranes caused by irradiation. As a result of irradiation, the enviroment of the spin probe is modified and this modification can be followed from the recorded spectra. The doses studied were 1.0, 2.5, 10.0, and 20.0 kGy. An aqueous solution of 16‐doxyl stearic acid (16‐DSA) was used The embryos were detached using a steel needle and kept in 16‐DSA solution for 2.5 hr and washed with distilled water. The spectra of the samples were recorded. The detection of irradiated wheats by this technique was possible at doses of ≥2.5 kGy. An important advantage of this approach is that it is applicable even after eight months of storage.

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