Ethanol- and trifluoroethanol-induced changes in phase states of DPPC membranes. Prodan emission-excitation fluorescence spectroscopy supported by PARAFAC analysis.

It has been shown that Prodan emission-excitation fluorescence spectroscopy supported by Parallel Factor (PARAFAC) analysis is a fast, simple and sensitive method used in the study of the phase transition from the noninterdigitated gel (L) state to the interdigitated gel (LI) phase, triggered by ethanol and 2,2,2-trifluoroethanol (TFE) molecules in dipalmitoylphosphatidylcholines (DPPC) membranes. The relative contribution of lipid phases with spectral characteristics of each pure phase component has been presented as a function of an increase in alcohol concentration. It has been stated that both alcohol molecules can induce a formation of the LI phase, but TFE is over six times stronger inducer of the interdigitated phase in DPPC membranes than ethanol molecules.

Interaction of anesthetic molecules with α-helix and polyproline II extended helix of long-chain poly-l-lysine.

The effect of halothane, enflurane, sevoflurane, and isoflurane molecules, as volatile anesthetics, on the α-helices and polyproline II extended helices (PPII) of long-chain poly-l-lysine (PLL) were studied using Fourier-transform infrared and vibrational circular dichroism spectroscopy. Uncharged and charged α-helices, as well as charged extended PPII helices, were subjected to anesthetic actions in solvents with different pD values or methanol to water ratios. A crucial factor responsible for hindering the anesthetic-PLL interactions is shown to be the ionization of amino groups of the PLL side chains.

Aggregation of N,N'-diallylurea and N,N'-diallylthiourea in solutions.

Joint studies by IR spectroscopy, dipole moments, average molecular weight measurements and DFT calculations on the self-aggregation of N,N'-diallylureas and N,N'-diallylthioureas in solvents of different polarities were performed. Simultaneous uses of all these methods are required for better understanding the mechanism of aggregation and the effects of different polarity of solvents. In this study also the measurements of IR spectra in polarized light were additionally performed, which gives information on arrangement of aggregates in liquid crystal matrix-built of 4-CN biphenyl derivative.

Anesthetic-dependent changes in the chain-melting phase transition of DPPG liposomes studied using near-infrared spectroscopy supported by PCA.

The effect of inhalation anesthetics (enflurane, isoflurane, sevoflurane or halothane) on the lipid chain-melting phase transition of negatively charged phospholipid membranes was studied using near-infrared (NIR) spectroscopy supported by Principal Component Analysis (PCA). NIR spectra of anesthetics-mixed dipalmitoylphosphatidylglycerol (DPPG) membranes were recorded in a range of the first overtone of the symmetric and antisymmetric stretching vibrations of CH groups of lipid aliphatic chains as a function of increasing temperature. Anesthetic-dependent changes in the trans to gauche conformers ratio of CH groups in the hydrocarbon lipid chains were characterized in detail and compared with the zwitterionic lipid membranes, which were built of dipalmitoylphosphatidylcholine (DPPC) molecules.

Self-aggregation mechanisms of N-alkyl derivatives of urea and thiourea.

The mechanisms of self-aggregation of N-alkyl and N,N'-dialkyl derivatives of urea and thiourea in weakly polar solvents (chloroform and 1,2-dichloroethane) were examined. The C-H···O or C-H···S hydrogen bonds formed with these two acidic solvents compete with the N-H···O or N-H···S hydrogen bonds formed between solute molecules, influencing the self-aggregation of urea derivatives in a particular solvent. The peculiarities of the solvent interactions were discussed and the stronger interaction of chloroform was noted.

Correlation between structure and shape of the polarized infrared absorption spectra of 4-chloro-2'-hydroxy-4'-alkyloxyazobenzenes.

Polarized infrared spectra of liquid crystalline 4-chloro-2'-hydroxy-4'-alkyloxyazobenzenes (CHAB) with C(5), C(6), and C(7) alkyl chains measured at 25 °C were compared, with particular attention being paid to the influence of chain length on formation of ordered boundary layers. The effect of chain elongation is discussed on the basis of calculations of the optimized geometry of dimeric species, which reflects the role of association in ordered phases. The impact of the varying intermolecular interactions on the spectra of C(5), C(6), and C(7) derivatives measured as a function of the polarization angle is analyzed by principal component analysis (PCA).

Structure of aggregates of dialkyl urea derivatives in solutions.

Combined IR spectroscopy, dipole moment, and average molecular weight measurements and DFT calculations on the self-aggregation of N,N'- and N,N-dialkylureas in solvents of different polarities were performed. It was found that, to acquire a better understanding of the mechanisms of associations, the simultaneous use of all of these methods is required. It was found that symmetric dialkyl derivatives of urea associate much more strongly, giving in CCl(4) even a 12-fold mass of monomers, in contrast to asymmetric ones, where the average molecular weight reaches only a 2-fold mass of monomers.

Influence of substituents on the anharmonicity of nus(OH) vibration in phenol derivatives explored by experimental and theoretical approach.

Very good reproducibility of the first five vibrational transitions of phenol in the gas phase by the MP2/ 6-31G potential for O-H bond stretching was found. The vibrational levels were calculated by a program for variational solving of the time-independent Schrödinger equation in one dimension. Relative intensities of particular transitions were determined on the basis of the function of the dipole moment.

Matrix-isolation FT-IR spectroscopic study and theoretical DFT(B3LYP)/6-31++G** calculations of the vibrational and conformational properties of tyrosine.

The complicated conformational isomerism of tyrosine is studied by experimental matrix-isolation FT-IR spectroscopy combined with theoretical DFT(B3LYP)/6-31++G** calculations. Not less than 18 possible conformations of tyrosine have been considered theoretically. The results revealed that the most and the less stable forms of neutral tyrosine have the same conformation of the main part of amino acid (conformation II) but they differ in orientation of the phenyl ring.