Motion Of Hydrocarbon Chains Research Articles

Self‐Aggregation of Catanionic Surface Active Ionic Liquids in Aqueous Solutions

AbstractThe self‐aggregation behavior of catanionic surface active ionic liquids (SAIL), 1‐alkyl‐3‐methylimidazolium alkyl sulfates, [C4mim][C16SO4] and [C6mim][C14SO4], in aqueous solutions was explored by several techniques. These results were analyzed together with the concerning data of [C8mim][C12SO4] reported previously. The feature of these SAIL is that the total carbon number of the hydrophobic chains is kept constant, while only the length of the two hydrocarbon chains varies. Because of the different intermolecular and intramolecular interactions, the hydrophobic interaction of asymmetrical SAIL is enhanced, which explains the minimal CMC value of [C4mim][C16SO4]. Thermal motion of hydrocarbon chains at the air–water interface leads to higher Amin and lower Γmax values with the increasing asymmetry of two hydrophobic chains. The conductivity measurements reveal that the micellization process is spontaneous and entropy‐driven in the studied temperature range. This work indicates that the symmetry of alkyl chains can influence the aggregation behavior of [Cnmim][CmSO4] in aqueous solutions.

Short Wavelength Collective Dynamics in Phospholipid Bilayers: A Molecular Dynamics Study

Short wavelength density fluctuations of hydrated multilamellar phospholipid bilayers have been studied by molecular dynamics simulations in both the gel and liquid crystalline phases, and the results compared to recent inelastic x-ray scattering data [Phys. Rev. Lett. 86, 740 (2001)]. We confirm the existence of a highly dispersive sound mode, whose frequency and damping depend on the lipid phase, that the scattering arises mainly from in-plane motion of hydrocarbon chains, and we also identify a nondispersive mode attributed to motions of the chain terminal carbons.

Monte Carlo dynamics study ofcisandtransunsaturated hydrocarbon chains

A new Monte Carlo dynamics algorithm for simulating the motions of hydrocarbon chains is presented. The algorithm utilizes the high coordination {2 1 0} lattice for the simultaneous representation of polymethylene and unsaturated chains. While the dynamics of saturated chains may be described as the superposition of local conformational changes, the motion of the planar unsaturated segments can be simulated only through the introduction of cooperative moves. Simulations of the motions in isolated 18-carbon chains show that the introduction of a cis double bond increases the relaxation rates for torsional motions, while the introduction of a trans double bond has the opposite effect. The difference in behaviour appears to arise simply from geometrical constraints.

Reorientational motions of the alkyl chains in C10H21ND3Cl bidimensional crystal

INS experiments were performed at the Institut Laue-Langevin on the bidimensional C 10 H 21 ND 3 Cl crystal to investigate the hydrocarbon chain motions through the various structural phases of the compound. The quasielastic profiles obtained on high and medium resolution spectrometers were refined simultaneously to get a reliable estimate of the elastic incoherent structure factors. In the high temperature phase, there is a gradient of disorder in the -CH 2-units on going from the polar head to the methyl ends in agreement with the “tree-like” structure suggested from previous Raman and infrared investigations.

Monte Carlo dynamics study of motions in c i s-unsaturated hydrocarbon chains

A Monte Carlo dynamics study of the motions of hydrocarbon chains containing cis double bonds is presented. The simulations utilize the high-coordination {2 1 0} lattice for the simultaneous representation of the tetrahedrally bonded carbon atoms and the planar unsaturated segment. Results on single chains undergoing free motion in space and tethered to an impenetrable planar interface are reported. The introduction of a cis double bond into a hydrocarbon chain induces a slowdown in the dynamics. The simulations show this to be a universal result independent of the representation of the chain on the lattice. In contrast, polyunsaturated chains are found to be more mobile than saturated ones.

NMR investigations of molecular motions inp-n-hexyloxybenzylidene-p′-n-propylaniline

Proton spin-lattice relaxation times,T 1, have been measured in the smectic phases, S G 2 , S G 1 and SA, and in the nematic phase of HxBPA, in the temperature range, 220K<T<360 K. In the S G 1 and S G 2 phases,T 1 has been measured at 15 and 40 MHz. The (S G 1 →S G 2 ) and (S G 2 →S G 1 ) transitions are clearly seen as discontinuities inT 1. The former transition is seen to be due to possible freezing or change of hydrocarbon chain motions of the molecule. Our data in the S G 1 phase have been fitted to a model in which anisotropic rotational diffusion of the end hydrocarbon chains as also that of the rigid part of the molecule are considered. In the nematic phase, at 351 K, the observed behaviour ofT 1, measured in the frequency range, 5 to 40 MHz, agrees well with the theoretical predictions of Uklejaet al and Freed, who take into account long range collective order fluctuations and local reorientations. Using these theories, the correlation time for short range reorientations has been calculated from our results to be 4.3 × 10−10 and 1.1 × 10−9 s respectively.

An electron paramagnetic resonance study of skeletal muscle membrane fluidity in malignant hyperthermia

Skeletal muscle sarcolemma (SL), transverse tubule (TT) and heavy sarcoplasmic reticulum (HSR) membranes were isolated from malignant hyperthermia susceptible (MHS) and normal pigs, and the rotational dynamics of lipid hydrocarbon chain motion was examined by electron paramagnetic resonance (EPR) spectroscopy. The stearic acid spin probe 16-SASL was incorporated into MHS and normal membranes and both the order parameter ( S) and effective correlation time ( τ r) of probe motion were calculated from spectra recorded over the temperature range of 2 to 40°C. At any given temperature, TT membranes exhibited significantly greater values for both the S and τ r of probe motion than did SL, which exhibited significantly greater values than did HSR membranes. The order of decreasing S and τ r values for 16-SASL mobility correlated with the decreasing cholesterol content of these membranes (TT>SL>HSR), however there was no difference in the S or τ r values for a given membrane fraction isolated from both MHS and normal muscle. Arrhenius plots of 16-SASL mobility in SL, TT and HSR were linear from 2 to 40°C, indicating no abrupt thermotropic change in the lipid hydrocarbon phase of any of the membrane types studied. Apparent activation energies ( E a), calculated from the Arrhenius plots, were similar for MHS and normal membranes derived from a given cellular location. However, the E a of probe motion for TT membranes (2.3 ± 0.1 and 2.4 ± 0.1 kcal/mol/degree for MHS and normal, respectively) was significantly less than for SL (3.4 ± 0.4 and 2.9 ± 0.1 kcal/mol/degree for MHS and normal, respectively) which, in turn, was significantly less than the E a for HSR (3.7 ± 0.1 and 3.7 ± 0.1 kcal/mol/degree for MHS and normal, respectively). Since 16-SASL motion was similar in MHS and normal membranes, we conclude that there is no evidence for a generalized membrane defect affecting lipid mobility in these MHS muscle membranes.

Structural studies of lipophorin in insect blood by differential scanning calorimetry and 13C nuclear magnetic relaxation measurements. Location of hydrocarbons.

The possible structure of lipophorin in insect blood (hemolymph) was investigated by differential scanning calorimetry (DSC) and 13C nuclear magnetic relaxation studies. The DSC heating curves of intact lipophorins showed endothermic peaks between -3 and 40 degrees C for lipophorins which contain hydrocarbons, whereas no such peaks were observed for lipophorins which do not contain this lipid. Hydrocarbon fractions isolated from the lipophorins showed endothermic peaks similar to those obtained from intact lipophorin in terms of the transition temperatures, the shapes, and the enthalpy changes. 13C spin lattice relaxation times of the (CH2)n resonance of hydrocarbons of intact lipophorin were measured as a function of temperature and revealed that the motions of hydrocarbon chains changed coincidentally with the onset and offset of phase transition. These data suggest the presence of a hydrocarbon-rich region within the lipophorin particles.

Changes in segmental motion of the membrane‐composing molecules of dimyristoyl phosphatidyl choline liposomes by incorporation of polypeptides

AbstractThe interaction of glycoprotein and polypeptides with phospholipid liposomes was investigated by means of the fluorescence polarization technique. Poly(L‐glutamic acid) was incorporated into the bilayer of dimyristyol phosphatidyl choline liposomes by sonication. It reduces the segmental motion of the lipids especially in the hydrophobic region close to the hydrophilic surface. On the contrary, poly(L‐leucine), on incorporation into the lipids, strongly suppresses the molecular motion of hydrocarbon chains. Glycoprotein from bovine serum brings about a remarkable decrease in the molecular motion of hydrocarbon chains. In this case the molecular motion of the lipid for liposomes with 20% glycoprotein incorporation is comparable to that of the human erythrocyte ghost. The interaction of polypeptides with liposomes was also observed with an optical microscope by using gaint liposomes (∅︁ ca. 100 μm).

Studies in membrane processes. VIII. A deuterium and sodium nuclear magnetic resonance investigation into the hexadecylpyridinium/hexadecyltrimethylammonium liquid crystalline system

Novel lyotropic mesophases that spontaneously orient in magnetic fields have been prepared using hexadecylpyridinium chloride and hexadecyltrimethylammonium bromide as well as, in limited regions, mixtures of the two detergents. These mesophases of type II provide the opportunity to study the behaviour of oriented water (DOH) at the hydrophobic interface, sodium ions, and the effect on hydrocarbon chain motions of variations in composition of the constituent bilayers formed by the mixed detergent systems. The pyridinium head group is especially accessible to definitive studies using deuterium magnetic resonance spectra of specifically deuteriated ring and adjacent hydrocarbon chain segments. Such investigations reveal the lack of cylindrical symmetry of motion about the extended chain axis near the pyridinium head group.The deuterium resonance of the HOD species shows that both pyridinium and trimethylammonium head groups have a very small orienting effect on the adjacent water, which appears to be indifferent to the choice of these chemical identities. This is understandable in terms of the lack of hydrogen bonding to these moieties. Sodium ions also exhibit small quadrupole splittings in all systems studied here and thus probably play a passive role in the interface chemistry and structure.

Interaction of butylated hydroxytoluene (BHT) with phospholipid bilayer membranes: Effect on 22Na permeability and membrane fluidity

Butylated hydroxytoluene (BHT) is a small lipophilic molecule that is widely used as a food preservative. The interaction of this chemical with phospholipid bilayer membranes was monitored by measuring changes in 22Na transport and hydrocarbon chain motion. Vesicles composed of saturated phospholipids display a marked increase in 22Na permeability in the temperature region of the phase transition temperature of the component phospholipid. BHT greatly reduces this permeability increase. When a series of structural analogues was examined, there was found to be a poor correlation between lipid solubility and the capacity to decrease 22Na transport. However, the presence of a hydroxyl group appeared to be an important structural requirement for the permeability change. In a parallel set of experiments, a spin labelled fatty acid ester was incorporated into similar vesicles and the mobility of the label used as a measure of lipid hydrocarbon chain motion. The phase transition temperature of a phospholipid is associated with a marked increase in fatty acyl chain motion. BHT lowers the temperature at which the lipid chains display significant motional freedom (i.e. melt). Since this change in membrane fluidity cannot account for the capacity of BHT to reduce 22Na permeability some additional perturbation must be occurring. It is proposed that this additional perturbation involves an alteration at the interface.

Interaction of dibucaine and propranolol with phospholipid bilayer membranes—Effect of alterations in fatty acyl composition

Sodium 22 efflux was measured, at various temperatures both in the presence and absence of dibucaine or propranolol, in multilamellar liposomes composed of different phosphatidylcholines and dicetylphosphate. Such vesicles display a marked increase in sodium permeability in the temperature region of the phase transition of the component phospholipid. Both local anesthetics lower the temperature of onset of this permeability increase, the extent of the reduction being dependent upon the anesthetic concentration. The liposomes used in these experiments possess a negative charge due to the presence of dicetylphosphate. When exposed to dibucaine, these vesicles develop a significant positive surface potential at the same temperature at which this anesthetic increases 22Na efflux. In a parallel series of experiments, a spin-labeled fatty acid ester was incorporated into similar liposomes and the mobility of the label used as a measure of lipid hydrocarbon chain motion. The phase transition of a phospholipid is associated with a marked increase in fatty acyl chain motion. Both anesthetics lower the temperature at which the lipid chains display significant motional freedom. These observations indicate that dibucaine and propranolol interact with liposomes so as to bring about the phase transition (i.e. melt the hydrocarbon chains) of the membrane lipids at a temperature below that at which this event normally occurs.

Proton magnetic resonance studies of lipid bilayer membranes Experimental determination of inter- and intramolecular nuclear relaxation rates in sonicated phosphatidylcholine bilayer vesicles

We have determined the relative magnitudes of the intra- and intermolecular contributions to the nuclear magnetic relaxation rates of the methylene protons of the hydrocarbon chains in phosphatidylcholine bilayer vesicles over a range of temperatures and at two NMR frequencies (100 and 220 MHz). These measurements have been made by the isotopic dilution method using deuterated phosphatidylcholines containing fully deuterated hydrocarbon chains. The results showed that both the methylene linewidths and the spin-lattice relaxation rates are dominated by intramolecular dipolar interactions. Both the intra- and intermolecular contributions to the spin-lattice relaxation rate were found to decrease with increasing temperature and to exhibit a frequency dependence, the rates being higher at the lower NMR frequency in both cases. These observations indicate that both intra- and intermolecular dipolar interactions are modulated by anisotropic motions. In the case of the intermolecular dipolar fields, it is proposed that they are modulated both by the rapid rotational isomerization of the hydrocarbon chains as well as by lateral diffusion of the lipid molecules. That the hydrocarbon chain motion must be fairly effective in effecting efficient spin-lattice relaxation is evident from the negligible intramolecular interchain contribution to the relaxation found in the present work.

Effect of Various Sterols on the 22Na Permeability and Fluidity of Phospholipid Bilayer Membranes

Sodium-22 efflux was measured in multilamellar liposomes composed of egg lecithin, dicetylphosphate, and various sterols. In a parallel series of experiments a spin labelled fatty acid ester was incorporated into similar vesicles and the molecular motion of the spin label monitored by electron spin resonance spectroscopy. Spin lable mobility was used as a measure of phospholipid hydrocarbon chain motion. There was a poor correlation between the effects of these sterols on sodium permeability and their effects on the motion of the lipid chains. It is postulated that sterols alter sodium transport not only through a reduction in the motional freedom of membrane lipids, but also through changes in the partitioning of sodium between membrane and aqueous phases.

Membrane processes. VII. Hydrocarbon chain motions and the effect of changing counterions

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMembrane processes. VII. Hydrocarbon chain motions and the effect of changing counterionsL. W. Reeves and A. S. TraceyCite this: J. Am. Chem. Soc. 1975, 97, 20, 5729–5735Publication Date (Print):October 1, 1975Publication History Published online1 May 2002Published inissue 1 October 1975https://doi.org/10.1021/ja00853a016RIGHTS & PERMISSIONSArticle Views58Altmetric-Citations32LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (792 KB) Get e-Alerts Get e-Alerts

Raman and resonance-Raman scattering by erythrocyte ghosts

1. 1. We present the laser-Raman spectra of human erythrocyte ghosts, isolated by standard condition and compare these with the spectra of lecithin liposomes and fat-free serum albumin. 2. 2. The hydrocarbon stretching modes of membrane lipids are temperature sensitive and may serve as an index of hydrocarbon chain motion. 3. 3. The Amide I and Amide III bands of ghosts in H 2O and 2H 2O, indicate a mixture of α-helical and unordered conformation, but do not allow a quantitative estimate of secondary structure. 4. 4. Strong, scattering bands at 1530 and 1165 cm −1 are attributable to conjugated double bond systems, probably of membrane-associated carotenoids. Their high intensity is due to resonance enhancement.

Structures of Aqueous Dispersions of Phosphatidylserine

Abstract Dilute (g10% w/v) unsonicated phosphatidylserine dispersions in H2O contain spherical particles of a wide size distribution (0.1 to 15 µm). The majority have diameters between 0.1 to 2 µm and lack the multilamellar arrangement of bilayers typical of unsonicated lecithin dispersions. Sonication produces small thermodynamically unstable vesicles surrounded by a single closed bilayer with an average vesicle diameter of 160 A (range 125 to 250 A). The vesicles are more homogeneous with respect to size and their curvature is significantly greater than that of vesicles prepared from lecithins of similar chain length. While phosphatidylserine forms inverted micelles in organic solvent, no micelles were detected in sonicated, aqueous dispersions. Increasing the ionic strength leads to an increase in particle size and to the formation of multilamellar structures both with sonicated and unsonicated dispersions and eventually flocculation of a metal-phosphatidylserine complex occurs. Unsonicated phosphatidylserine dispersions give no high resolution spectrum. Proton nuclear magnetic resonance measurements on sonicated dispersions in 2H2O show that the molecular motion in the polar group of the molecule is sufficient for all protons, including those of the glycerol group, to contribute to the high resolution spectrum. Increasing the ionic strength leads to a closer packing of the polar groups and of the hydrocarbon chain CH2 groups close to the glycerol group without significantly affecting the correlation times of motion of most of the protons along the hydrocarbon chains. However, the anisotropy of the hydrocarbon chain motion and thus the degree of order within the bilayer increases significantly.

The molecular reorganization of lipid bilayers by osmium tetroxide: A spin-label study of orientation and restricted y-axis anisotropic motion in model membrane systems

Phospholipid dispersions spontaneously form oriented lamellar multilayers when dried onto glass slides. These oriented multilayers form useful model systems for studying the molecular dynamics of lipid bilayers. In order to examine the effects of osmium tetroxide on the orientation and motion of hydrocarbon chains in lipid bilayers, lecithin multilayers containing the spin label 3-doxyl-5α-cholestane (the 4′,4′-dimethyloxazolidine- N-oxyl derivative of 5α-cholestan-3-one) were prepared and examined by electron spin resonance spectroscopy. In egg lecithin multilayers at room temperature and 81% relative humidity the osmium tetroxide causes nearly complete loss of orientation and severe reduction of molecular motion. In contrast, the high degree of order in l-α-dipalmitoyl lecithin multilayers is not affected by exposure to osmium tetroxide vapors. Experiments are also reported on macroscopically disordered lecithin preparations, and the data support the conclusions drawn from the ordered lecithin multilayers that rotational mobility of the probe is severely reduced by fixation of the lipid chains. A simple mathematical model has been developed to account for the amplitude of the high-frequency (τ < 10 −8 sec) restricted y-axis anisotropic motion occurring in the bilayer plane. Since the y-axis is roughly parallel to the molecular axis of the rigid steroid spin label, this model enables quantitative comparisons of various degrees of restricted motion about the molecular axis.

On the nature of hydrocarbon chain motions in lipid liquid crystals

Consideration of the thermodynamic parameters of the crystal to liquid crystal transition for lecithins and of the fusion of molecules containing hydrocarbon chains allows a quantitative estimate of the configurational freedom of hydrocarbon chains in the liquid crystalline states at the transition temperature. For lipids in general, it appears that the chain mobility is intermediate between that of β (or β′) crystals and an n-alkane melt. The freedom of hydrocarbon chain motions is, however, greater in fully hydrated liquid crystalline systems than in anhydrous systems. These conclusions are pertinent to the much discussed question of hydrocarbon chain fluidity in thermotropic mesophases and certain biological systems.