Biomembranes, which are the structural and functional basis of the cells of all living organisms, have been an extremely interesting research object for biology and chemistry scientists for years. The multitude of elements constituting the components of natural lipid membranes, however, is associated with interpretation difficulties regarding the nature of the processes taking place in them. A useful research object that is a model of bilamellar biosystems with a significantly simplified composition and at the same time retaining properties that can be a reference point in relation to natural membranes are lipid membranes in the form of one or several component liposomes. It is precisely such systems built of molecules of dipalmitoyl phosphatidylcholine (DPPC) or dipalmitoyl phosphatidylglycerol (DPPG), and analogous systems with the addition of cholesterol (Chol), that were the subject of research in this work. Near-infrared (NIR) vibrational spectroscopy provides a suitable method for the study of the hydrated samples. In most cases it can be alternatively adopted instead of commonly used mid-infrared (MIR) vibrational spectroscopy. This technique was applied for the first time to identify the spectral changes associated with the conformational changes in the hydrophobic region of model lipid bilayers. Trans/gauche isomerization of CH2 groups of lipid hydrocarbon chains is accompanied by characteristic changes in spectral parameters of both νas,s CH2 bands and their first overtones (2νas,s CH2). The heating of all types of analyzed liposomes results in main phase transition (Tm) accompanied by trans to gauche isomerization of CH2 groups of lipid hydrocarbon chains. The NIR-spectroscopy was able to describe in proper way (similar to MIR results) the character of Tm in studied bilayers.

The reversible interaction of halothane (C2HBrClF3) with negatively charged local areas of molecular targets is defined in a large extent by the proton donor ability of CH group. This interaction leads to the formation of a hydrogen bond of the CH … B type. In the presence of heavy halogen atoms in the CHClBr group, the CX … B halogen bond can act as an alternative or additional target grip option. The results obtained by the cryospectroscopy method for solutions of halothane with large excess of trimethylamine in liquefied krypton suggest the trimer formation, stabilized by hydrogen and halogen bonds between this volatile anesthetic and electron donor targets.

The IR spectra of mixtures of methoxyflurane and dimethyl ether are studied with the help of FTIR cryospectroscopy in liquefied Xe. The region of CH3 and CH stretching vibrations is examined taking into account the Fermi resonance effect. Comparative analysis of the experimental data and results of ab initio calculations show that the Cl2CH group of methoxyflurane is involved in complex formation which is stabilized by H-bond between H atom of this group and O atom of dimethyl ether predominantly.

The IR spectra of sevoflurane thorn dimethyl ether mixtures dissolved in liquid Kr are studied at T similar to 118 -155 K. The characteristic changes observed in numerous IR bands of both moieties suggest the formation of complexes stabilized by non covalent interactions of H-bond type. Estimations based on ab initio calculations including anharmonic effects are in line with the experimental findings. (C) 2020 Elsevier B.V. All rights reserved.

The IR spectra of isoflurane + dimethyl ether mixtures dissolved in liquid Kr are registered at T ~118-160 K. The results obtained at a wide range of relative concentrations suggest the formation of complexes stabilized by non-covalent interactions of H-bond type. Large excess of DME and low temperature favor trimer formation stabilized by interactions between two DME moieties and both CH groups of isoflurane predominantly. Estimations based on ab initio calculation of spectroscopic and thermodynamic parameters confirm the experimental findings.

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. The α-helix to β-sheet transition was triggered only for the uncharged α-helical structures of PLL by the nonpolar anesthetics under study.

The interactions between halothane (2-bromo-2-chloro-1,1,1-trifluoroethane) and acetylene (C2H2) are studied by FTIR spectroscopy. Results obtained in liquid cryosolutions in Kr suggest weak complex formation stabilized by H - bond. The complexation enthalpy (similar to 11 kJ/mol) is evaluated in a series of temperature measurements (T similar to 120-160 K) of integrated intensity of selected bands performed in liquefied Kr. The quantum chemical MP2/6-311++G(2d,2p) calculations predict four different structures of the complex. The most stable and populated (94% at T similar to 120 K) structure corresponds to the H - bond between H atom of halothane and pi-electron of triple bond between C atoms of acetylene. Wave numbers of vibrational bands of the most stable structure are calculated in anharmonic approximation implemented in Gaussian program. (C) 2018 Elsevier B.V. All rights reserved.

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 (Lβ') state to the interdigitated gel (LβI) 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 LβI phase, but TFE is over six times stronger inducer of the interdigitated phase in DPPC membranes than ethanol molecules. Moreover, in the TFE-mixed DPPC membranes, the transition from the Lβ' to LβI phase is accompanied by a formation of the fluid phase, which most probably serves as a boundary phase between the Lβ' and LβI regions. Contrary to the three phase-state model of TFE-mixed DPPC membranes, in ethanol-mixed DPPC membranes only the two phase-state model has been detected.

The influence of cholesterol on the structure of the model lipid bilayers treated with inhalation anesthetics (enflurane, isoflurane, sevoflurane and halothane) was investigated employing near-infrared (NIR) spectroscopy combined with the Principal Component Analysis (PCA). The conformational changes occurring in the hydrophobic area of the lipid bilayers were analyzed using the first overtones of symmetric (2νs) and antisymmetric (2νas) stretching vibrations of the CH2 groups of lipid aliphatic chains. The temperature values of chain-melting phase transition (Tm) of anesthetic-mixed dipalmitoylphosphatidylcholine (DPPC)/cholesterol and dipalmitoylphosphatidylglycerol (DPPG)/cholesterol membranes, which were obtained from the PCA analysis, were compared with cholesterol-free DPPC and DPPG bilayers mixed with inhalation anesthetics.

The IR spectrum of isoflurane dissolved in liquid Kr, and Xe, and Raman spectrum of pure liquid are registered and analyzed. Fundamental bands are assigned using "anharm" option of ab initio calculations. Estimations based on calculated thermodynamic and spectroscopic parameters confirm experimentally found temperature effect of noticeable redistribution of intensity of selected pair of bands ascribed to the most populated two rotamers. Concentrations of two rotamers become comparable at T similar to 295 K. (C) 2016 Elsevier B.V. All rights reserved.

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. It was demonstrated that in such conditions two forms of dimers the linear and cyclic ones are in equilibrium with different arrangements according the axis of CN group. (C) 2017 Published by Elsevier B.V.

The IR spectra of mixtures of desflurane and dimethyl ether are studied with the help of FTIR cryospectroscopy in liquefied Kr at T~118–158K. Comparative analysis of the experimental data and results of ab initio calculations show that either of the two C-H groups of desflurane is involved in heterodimer formation of comparable strengths. The blue frequency shift is found for stretching vibrations of those C-H donors which directly participate in H–bond formation. Additionally the complexes are stabilized by weaker contacts between hydrogen atoms of dimethyl ether and fluorine atoms of desflurane.

IR absorption spectra of solutions of halothane (C 2 HBrClF 3 ) and acetone ((CD 3 ) 2 CO) mixtures in liquefied noble gases (krypton and xenon) have been recorded and analyzed. Bands due to weak hydrogenbonded complexes are identified. The complex-formation enthalpy is estimated in a series of temperature experiments on the change in the total intensity of the bands due to monomers and complexes. Second-order bands are found, which are assigned to the first overtone of stretching vibration CH of halothane and the Raman band related to simultaneous excitation of stretching vibration CH of halothane and stretching vibration CO of acetone. The results of ab initio calculation performed within the МР2/6-311++G(d, p) approximation are used to analyze the spectroscopic data.

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 CH2 groups of lipid aliphatic chains as a function of increasing temperature. Anesthetic-dependent changes in the trans to gauche conformers ratio of CH2 groups in the hydrocarbon lipid chains were characterized in detail and compared with the zwitterionic lipid membranes, which were built of dipalmitoylphosphatidylcholine (DPPC) molecules.

Near-infrared (NIR) spectroscopy was applied for the first time to study the chain-melting phase transition of a lipid bilayer wall of dipalmitoylphosphatidylcholine (DPPC) liposomes in the presence of different inhalation anesthetics (enflurene, halothane, isoflurane, and sevoflurane). A good agreement with the literature data referred to anesthetic/DPPC membranes studied by many other techniques showed that NIR could be applied to the studies of lipid membranes as an alternative to commonly used mean-infrared (MIR) method. Relations between the temperature of the lipid phase transition of doped DPPC liposomes and the anesthetic concentration were estimated. The potency of disturbance of the lipid phase transition was compared between studied anesthetics.

FTIR spectra of the gas phase Cl3CD + TMA mixture have been studied at room temperature in similar to 800-4000 cm(-1) frequency domain. The formation of the H-bonded Cl3CD center dot center dot center dot TMA complex has been detected. Spectroscopic parameters of the band ascribed to the complex were evaluated. MP2 frozen core ab initio calculations have been carried out with the Pople-type 6-311++G(d,p) basis set. The equilibrium geometries and harmonic vibrational frequencies of the complex were obtained using CP-corrected gradient techniques. The "freq = anharm" option has been tested for Cl3CD monomer and Cl3CD center dot center dot center dot TMA complex to examine possible anharmonic effects on the vibrations localized on the proton donor. The effects of Darling-Dennison and Fermi resonances on the frequency of the stretching vibration of the CH proton donor were analyzed. (C) 2013 Elsevier B.V. All rights reserved.

The vibrational spectra of desflurane are studied with the help of FTIR cryospectroscopy in liquefied Kr at T∼120–160K and Raman spectroscopy of pure liquid. Particular IR bands reveal qualitative temperature changes of conformational origin. Only two of the six stable conformers found in MP2/6-311++G(d,p) calculations contribute to the spectra. The calculated vibrational spectra reflect the basic features of experimental spectra. IR spectra of two component cryosolutions suggest weak complex formation between desflurane and methyl fluoride stabilized by ‘blue shifting’ H bonds.

MCR-ALS analysis produces concentration profiles of pure phase states present in heated DPPC liposomes.