The influence of structural changes of theN‐substituent on liquid crystalline behaviour of ester imides

2006 ◽  
Vol 33 (10) ◽  
pp. 1143-1151 ◽  
Author(s):  
Ewa BiaŁecka‐Florjańczyk ◽  
Ewa Majewska ◽  
Dorota Melon‐Ksyta ◽  
Irma Śledzińska ◽  
Jan Przedmojski ◽  
...  
Keyword(s):  
Liquid Crystalline ◽  
Structural Changes

scholarly journals An organic crystalline state in ageing atmospheric aerosol proxies: spatially resolved structural changes in levitated fatty acid particles

2021 ◽  
Author(s):  
Adam Milsom ◽  
Adam M. Squires ◽  
Jacob A. Boswell ◽  
Nicholas J. Terrill ◽  
Andrew D. Ward ◽  
...  
Keyword(s):  
Oleic Acid ◽  
Air Quality ◽  
Liquid Crystalline ◽  
Structural Changes ◽  
Unsaturated Fatty Acids ◽  
Organic Aerosols ◽  
Cloud Formation ◽  
Phase Gradient ◽  
Spatially Resolved ◽  
Surface Active

Abstract. Organic aerosols are key components of the Earth’s atmospheric system. The phase state of organic aerosols is known to be a significant factor in determining aerosol reactivity, water uptake and atmospheric lifetime – with wide implications for cloud formation, climate, air quality and human health. Unsaturated fatty acids contribute to urban cooking emissions and sea spray aerosols. These compounds, exemplified by oleic acid and its sodium salt, are surface active and have been shown to self-assemble into a variety of liquid-crystalline phases upon addition of water. Here we observe a crystalline acid–soap complex in acoustically levitated oleic acid–sodium oleate particles. We developed a synchrotron-based simultaneous Small-Angle & Wide-Angle X-ray Scattering (SAXS/WAXS)/Raman microscopy system to probe physical and chemical changes in the proxy during exposure to humidity and the atmospheric oxidant ozone. We present a spatially resolved structural picture of a levitated particle during humidification, revealing a phase gradient consisting of a disordered liquid crystalline shell and crystalline core. Ozonolysis is significantly slower in the crystalline phase compared with the liquid phase and a significant portion (34 ± 8 %) of unreacted material remains after extensive oxidation. We present experimental evidence of inert surface layer formation during ozonolysis, taking advantage of spatially resolved simultaneous SAXS/WAXS experiments. These observations suggest atmospheric lifetimes of surface-active organic species in aerosols are highly phase dependent, potentially impacting on climate, urban air quality and long-range transport of pollutants such as Polycyclic Aromatic Hydrocarbons (PAHs).

scholarly journals Supramolecularity creates nonstandard protein ligands.

1999 ◽  
Vol 46 (4) ◽  
pp. 841-851 ◽  
Author(s):  
B Piekarska ◽  
J Rybarska ◽  
B Stopa ◽  
G Zemanek ◽  
M Król ◽  
...  
Keyword(s):  
Liquid Crystalline ◽  
Structural Changes ◽  
Structural Instability ◽  
Antigen Binding ◽  
Experimental Science ◽  
Water Solutions ◽  
Protein Ligands ◽  
Native Proteins ◽  
Receptor Sites ◽  
Self Association

Congo red and a group of structurally related dyes long used to stain amyloid proteins are known to associate in water solutions. The self-association of some dyes belonging to this group appears particularly strong. In water solutions their molecules are arranged in ribbon-like micellar forms with liquid crystalline properties. These compounds have recently been found to form complexes with some native proteins in a non-standard way. Gaps formed by the local distribution of beta-sheets in proteins probably represent the receptor sites for these dye ligands. They may result from higher structural instability in unfolding conditions, but also may appear as long range cooperative fluctuations generated by ligand binding. Immunoglobulins G were chosen as model binding proteins to check the mechanism of binding of these dyes. The sites of structural changes generated by antigen binding in antibodies, believed to act as a signal propagated to distant parts of the molecule, were assumed to be suitable sites for the complexation of liquid-crystalline dyes. This assumption was confirmed by proving that antibodies engaged in immune complexation really do bind these dyes; as expected, this binding affects their function by significantly enhancing antigen binding and simultaneously inhibiting C1q attachment. Binding of these supramolecular dyes by some other native proteins including serpins and their natural complexes was also shown. The strict dependence of the ligation properties on strong self-assembling and the particular arrangement of dye molecules indicate that supramolecularity is the feature that creates non-standard protein ligands, with potential uses in medicine and experimental science.

Shear-induced liquid-crystalline phase transition behaviour of colloidal solutions of hydroxyapatite nanorod composites

Nanoscale ◽  
2020 ◽  
Vol 12 (21) ◽  
pp. 11468-11479
Author(s):  
Satoshi Kajiyama ◽  
Hiroki Iwase ◽  
Masanari Nakayama ◽  
Rino Ichikawa ◽  
Daisuke Yamaguchi ◽  
...  
Keyword(s):  
Phase Transition ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Liquid Crystalline ◽  
Structural Changes ◽  
Colloidal Solutions ◽  
Rheological Measurements ◽  
Transition Behaviour ◽  
Crystalline Phase Transition

The shear-induced structural changes and phase transition behaviour of colloidal hydroxyapatite-based nanorod composites are examined using in situ small-angle neutron scattering and rheological measurements.

Dielectric Studies of a Series of Liquid Crystalline Pyridine Derivates

1996 ◽  
Vol 51 (9) ◽  
pp. 1019-1026 ◽  
Author(s):  
S. Heinemann ◽  
H. Kresse ◽  
S. Saito ◽  
D. Demus
Keyword(s):  
Frequency Dependence ◽  
Crystalline State ◽  
Liquid Crystalline ◽  
Structural Changes ◽  
Alkoxy Group ◽  
Dielectric Constants ◽  
Dielectric Studies ◽  
Frequency Range ◽  
Liquid Crystalline Phases ◽  
Static Dielectric Constants

Abstract Measurements of the temperature and frequency dependence of dielectric constants have been performed for five homologues in the range 100 Hz -10 MHz. These substances exhibit a negative anisotropy of the dielectric constants and two relaxation regions (rotation of the molecules around the short resp. long axis) in the investigated frequency range. Even in the crystalline state dipolar reorientations are possible which have been interpreted as rotations of the alkoxy group. Changes of the static dielectric constants, relaxation frequencies and transition entropies are discussed as a measure of structural changes passing the several liquid crystalline phases.

scholarly journals Application of spin markers for study of liposome prepared by the modified reverse-phase evaporation method

2008 ◽  
Vol 22 (1) ◽  
pp. 33-41 ◽  
Author(s):  
Danuta Pentak ◽  
Wiesław W. Sułkowski ◽  
Agnieszka Wolińska ◽  
Sławomir Maślanka ◽  
Barbara Bojko ◽  
...  
Keyword(s):  
Spin Label ◽  
Liquid Crystalline ◽  
Structural Changes ◽  
Hyperfine Coupling Constant ◽  
Epr Spectra ◽  
Reverse Phase ◽  
Evaporation Method ◽  
Relative Value ◽  
Environment Temperature ◽  
Gel Phase

The EPR spectroscopy was used to determine the structure and physicochemical properties of liposomes prepared from L-α-phosphatidylcholine dipalmitoyl (DPPC) by the modified reverse-phase evaporation method (mREV). EPR study was carried out in the temperature range from 297 K to 340 K i.e. below and above the phase transition temperatureTCof DPPC. On the basis of EPR spectra of spin marker 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) incorporated into the liposome, the parameterfwas determined. TEMPO dissolves easily in water and in the fluid lamellar smectic liquid-crystaline phase of lipid bilayer but is largely excluded from the solid, gel-phase. Thus TEMPO can be used to observe the change in the partition between aqueous and fluid lipid regions. The change in the relative value offas a function of temperature for DPPC shows that, in the presence of water excess, this phospholipids undergoes a transition from a “gel phase” to a lamellar smectic liquid crystalline phase. On the basis of EPR spectra of spin marker 2-(3carboxypropyl)-4,4-dimethyl-2-tridecyl-3-oxazolidinloxyl (5-DOXYL) incorporated into liposome, the parametera'Nwas determined. The isotropic14N-hyperfine coupling constanta'Nof nitroxide spin label depends on the local environmental polarity. The increase ofa'Nvalue reflects the rise of polarity of spin label environment. Temperature, cholesterol and pH dependent structural changes were also described.

scholarly journals Tocopheryl Succinate-Induced Structural Changes in DPPC Liposomes: DSC and ANS Fluorescence Studies

Molecules ◽  
2020 ◽  
Vol 25 (12) ◽  
pp. 2780
Author(s):  
Grażyna Neunert ◽  
Jolanta Tomaszewska-Gras ◽  
Stanislaw Witkowski ◽  
Krzysztof Polewski
Keyword(s):  
Zeta Potential ◽  
Liquid Crystalline ◽  
Structural Changes ◽  
Aqueous Environment ◽  
Biophysical Parameters ◽  
Scanning Calorimetry ◽  
Selective Toxicity ◽  
Fluorescence Studies ◽  
Tocopheryl Succinate ◽  
And Shifts

Recent studies show that alpha-tocopheryl succinate (TS) exhibits selective toxicity against cancer cells. In this study, we investigated the effect of TS’s presence on the physico-chemical and structural properties of DPPC liposomes using fluorescence parameters (intensity, lifetime, and position of emission maximum) of 1-anilino-8-naphtalene sulphonate (ANS), differential scanning calorimetry (DSC) and zeta potential methods. Increasing the TS presence in the DPPC gel phase produced ANS fluorescence enhancement with a hypsochromic shift of the maximum. The zeta potential measurements show an increase in the negative surface charge and confirmed that this process is connected with the hydrophobic properties of dye, which becomes located deeper into the interphase region with a progressing membrane disorder. Temperature dependence studies showed that an increase in temperature increases the ANS fluorescence and shifts the ANS maximum emission from 464 to 475 nm indicating a shift from hydrophobic to a more aqueous environment. In the liquid crystalline phase, the quenching of ANS fluorescence occurs due to the increased accessibility of water to the ANS located in the glycerol region. The DSC results revealed that increasing the presence of TS led to the formation of multicomponent DSC traces, indicating the formation of intermediate structures during melting. The present results confirmed that TS embedded into the DPPC membrane led to its disruption due to destabilisation of its structure, which confirmed the measured biophysical parameters of the membrane.

scholarly journals Phase Transitions and Structural Changes in DPPC Liposomes Induced by a 1-Carba-Alpha-Tocopherol Analogue

Molecules ◽  
2021 ◽  
Vol 26 (10) ◽  
pp. 2851
Author(s):  
Grażyna Neunert ◽  
Jolanta Tomaszewska-Gras ◽  
Aneta Baj ◽  
Marlena Gauza-Włodarczyk ◽  
Stanislaw Witkowski ◽  
...  
Keyword(s):  
Phase Transition ◽  
Fluorescent Probes ◽  
Liquid Crystalline ◽  
Structural Changes ◽  
Main Phase ◽  
Alpha Tocopherol ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Simultaneous Formation ◽  
Contour Plots

Steady-state emission spectroscopy of 1-anilino-8- naphthalene sulfonate (ANS) and 1,6-diphenyl-1,3,5-hexatriene (DPH), fluorescence anisotropy, and DSC methods were used to characterize the interactions of the newly synthesized 1-carba-alpha-tocopherol (CT) with a 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) membrane. The DSC results showed significant perturbations in the DPPC structure for CT concentrations as low as 2 mol%. The main phase transition peak was broadened and shifted to lower temperatures in a concentration-dependent manner, and pretransition was abolished. Increasing CT concentrations induced the formation of new phases in the DPPC structure, leading to melting at lower temperatures and, finally, disruption of the ordered DPPC structure. Hydration and structural changes of the DPPC liposomes using ANS and DPH fluorescent probes, which are selectively located at different places in the bilayer, were studied. With the increased concentration of CT molecules in the DPPC liposomes, structural changes with the simultaneous formation of different phases of such mixture were observed. Temperature studies of such mixtures revealed a decrease in the temperature of the main phase transition and fluidization at decreasing temperatures related to increasing hydration in the bilayer. Contour plots obtained from concentration–temperature data with fluorescent probes allowed for identification of different phases, such as gel, ordered liquid, disordered liquid, and liquid crystalline phases. The CT molecule with a modified chromanol ring embedded in the bilayer led to H-bonding interactions, expelling water molecules from the interphase, thus introducing disorder and structural changes to the highly ordered gel phase.

scholarly journals Effect of Liquid Crystalline Host on Structural Changes in Magnetosomes Based Ferronematics

Nanomaterials ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 2643
Author(s):  
Peter Bury ◽  
Marek Veveričík ◽  
František Černobila ◽  
Matúš Molčan ◽  
Katarína Zakuťanská ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electric Fields ◽  
Liquid Crystalline ◽  
Structural Changes ◽  
Light Transmission ◽  
Threshold Field ◽  
Acoustic Anisotropy ◽  
Transmission Measurements ◽  
Anisotropy Measurement

The effect of the liquid crystalline host on structural changes in magnetosomes based on ferronematics is studied using the surface acoustic wave (SAW) technique supported by some capacitance and light transmission measurements. The measurement of the attenuation response of SAW propagating along the interface between LC and the piezoelectric substrate is used to study processes of structural changes under magnetic field. The magnetosome nanoparticles of the same volume concentration were added to three different nematic LCs, 5CB, 6CB, and E7. Unlike to undoped LCs, the different responses of SAW attenuation under the influence of magnetic and electric fields in LCs doped with magnetosomes were observed due to characteristic structural changes. The decrease of the threshold field for doped LCs as compared with pure LCs and slight effects on structural changes were registered. The threshold magnetic fields of LCs and composites were determined from capacitance measurements, and the slight shift to lower values was registered for doped LCs. The shift of nematic-isotropic transition was registered from dependencies of SAW attenuation on temperature. The acoustic anisotropy measurement approved the previous supposition about the role of bulk viscosity in used SAW measurements. In addition, capacitance and light transmition investigations supported SAW results and pointed out conclusions about their magnetic field behavior. Obtained results are discussed and confronted with previous ones and coincide well with those observed using acoustic, optical, or dielectric techniques.

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