scholarly journals Sterol Chemical Structure and Conformation Influence the Thermotropic Phase Behaviour of Dipalmitoylphosphatidylcholine Bilayers

Eureka ◽  
2011 ◽  
Vol 2 (1) ◽  
pp. 11-23
Author(s):  
Matthew G.K. Benesch ◽  
David A. Mannock ◽  
Ronald N. McElhaney
Keyword(s):  
Differential Scanning Calorimetry ◽  
Double Bond ◽  
Chemical Structure ◽  
Ring Structure ◽  
Ring System ◽  
Phase Behaviour ◽  
Biological Molecules ◽  
Scanning Calorimetry ◽  
Bilayer Stability

Studying the nature of interactions between the sterol ring system and neigbouring phospholipid molecules is important for our understanding of the properties of sterols in biological molecules and the role of such interactions in many disease processes. In this project, the thermotropic phase behaviour of binary dipalmitoylphosphatidylcholine (DPPC)/sterol mixtures with different sterol ring configurations (C5,6 double bond, 5α-H and 5β-H orientation and either 3α-OH, 3β-OH, 3-ketone functional groups) was investigated using differential scanning calorimetry (DSC) and was compared to earlier studies of cholesterol/ and epicholesterol/DPPC mixtures. Given the differences in the thermodynamic parameters obtained from these mixtures and their associated changes in bilayer stability and miscibility, it is clear that changing the sterol chemical configuration has a significant effect on bilayer properties. Any sterol molecule whose ring structure deviates from that of cholesterol is unlikely to be fully miscible in mammalian membranes.

Role of Oxygen on Phase Behaviour of Benzylidene Aniline – A Comparative Study

2009 ◽  
Vol 64 (12) ◽  
pp. 844-848 ◽  
Author(s):  
Narayana Ajeetha ◽  
Durga P. Ojha
Keyword(s):  
Differential Scanning Calorimetry ◽  
Room Temperature ◽  
Phase Behaviour ◽  
Temperature Elevation ◽  
Scanning Calorimetry ◽  
Rigid Core ◽  
Schiff’S Base ◽  
Thermal Range ◽  
Clearing Temperature

Four structurally related Schiff’s base compounds are synthesized and their mesogenic properties are characterized by using Thermal Microscopy (TM) and Differential Scanning Calorimetry (DSC). The position of oxygen is varied from either sides of the bridging site, oxygen introduced on both sides and the oxygen is removed from the bridging site for the values of n = 8 and m = 5. The influence of oxygen atom to the extent of increase in thermal range, depression in melting temperature, elevation of clearing temperature is observed for all four compounds, viz. N (p-n-Octyloxy benzylidene) p-n-Pentyl aniline (8O.5), N (p-n-Octyl benzylidene) p-n-Pentyloxy aniline (8.O5), N (p-n-Octyloxy benzylidene) p-n-Pentyloxy aniline (8O.O5), and N (p-n-Octyl benzylidene) p-n- Pentyl aniline (8.5). The shift in the position of oxygen from the aldehyde to the aniline side and the removal of oxygen has a greater effect as they become room temperature liquids, whereas the oxygen on the aldehyde side and the oxygen on both sides of the rigid core moiety effect only the clearing temperatures. The results obtained are discussed in the light of the earlier data available on Schiff’s base nO.m compounds

scholarly journals Brazilian gutta-percha points. Part II: thermal properties

2007 ◽  
Vol 21 (1) ◽  
pp. 29-34 ◽  
Author(s):  
Cláudio Maniglia-Ferreira ◽  
Eduardo Diogo Gurgel-Filho ◽  
João Batista Araújo Silva Jr ◽  
Regina Célia Monteiro de Paula ◽  
Judith Pessoa Andrade Feitosa ◽  
...  
Keyword(s):  
Differential Scanning Calorimetry ◽  
Thermal Properties ◽  
Physical Properties ◽  
Ambient Temperature ◽  
Amorphous Phase ◽  
Thermal Behaviour ◽  
Chemical Structure ◽  
Scanning Calorimetry ◽  
Gutta Percha ◽  
Thermal Manipulation

This study was undertaken to explore the effect of heating on gutta-percha, analyzing the occurrence of endothermic peaks corresponding to the transformation that occurs in the crystalline structure of the polymer during thermal manipulation. This study also seeked to determine the temperature at which these peaks occur, causing a transformation from the beta- to the alpha-form, and from the alpha- to the amorphous phase. Eight nonstandardized gutta-percha points commercially available in Brazil (Konne, Tanari, Endopoint, Odous, Dentsply 0.04, Dentsply 0.06, Dentsply TP, Dentsply FM) and pure gutta-percha (control) were analysed using differential scanning calorimetry (DSC) and thermogravimetry analysis (TGA). The transition temperatures were determined and analysed. With the exception of Dentsply 0.04 and Dentsply 0.06, the majority of the products showed thermal behaviour typical of beta-gutta-percha, with two endothermic peaks, exhibiting two crystalline transformations upon heating from ambient temperature to 130°. Upon cooling and reheating, few samples presented two endothermic peaks. It was concluded that heating dental gutta-percha to 130°C causes changes to its chemical structure which permanently alter its physical properties.

SAXS Study of Selected Cationic Surfactant Influence on the DSPC-Based Model Phospholipid System

2007 ◽  
Vol 130 ◽  
pp. 257-262
Author(s):  
Maciej Kozak ◽  
Ludwik Domka ◽  
Stefan Jurga
Keyword(s):  
Phase Transition ◽  
Differential Scanning Calorimetry ◽  
Small Angle ◽  
Phase Behaviour ◽  
Lamellar Phase ◽  
Scanning Calorimetry ◽  
X Ray ◽  
X Ray Scattering ◽  
Hydrocarbon Chains ◽  
Main Transition

The phase behaviour of lipid bilayer systems prepared with 1,2-distearoyl-sn-glycero-3- phosphocholine (DSPC) with dodecyldimethyl(benzyloxymethyl)ammonium chloride (BzMDDAC) (at concentrations 0.1, 1 and 5%) has been studied by small angle X-ray scattering and differential scanning calorimetry. The SAXS and DSC results of the hydrated 10% DSPC revealed one typical phase transition corresponding to melting of the hydrocarbon chains at 55 °C. In the system of 10% DSPC - 0.1 % BzMDDAC the main transition was somewhat shifted towards lower temperatures, while at 1% concentration of BzMDDAC in the mixture, the lamellar phase disappeared, as evidenced by SAXS and DSC. The increase in BzMDDAC concentration to 5% in the mixture with 10% DSPC resulted in formation of a new lamellar phase.

Synergistic Antioxidation Properties of Tin Dialkyldithiocarbamate With Dialkyldiphenylalmine

2009 ◽  
Author(s):  
Jian-Qiang Hu ◽  
Ke-Yi Gao ◽  
Da-Wei Liu
Keyword(s):  
Thin Film ◽  
Differential Scanning Calorimetry ◽  
Fourier Transform ◽  
Chemical Structure ◽  
Ftir Analysis ◽  
Synthetic Lubricant ◽  
Scanning Calorimetry ◽  
Oxidation Induction Time ◽  
Pentaerythritol Ester ◽  
Carbonyl Peak

Differential scanning calorimetry (DSC) and thin film micro oxidation test (TMOT) were employed to evaluate the antioxidation properties of tin dialkyldithiocarbamate (SnDDC) with p,p′dioctyldiphenylamine (DODPA) antioxidant in pentaerythritol ester (PE) or polyalphaolefin synthetic lubricant (PAO), and their chemical structure were identified by fourier transform infrared spectroscopy (FTIR) analysis. DSC test shows that incipient oxidation temperature and oxidation induction time of DODPA-containing PE were improved significantly by SnDDC addition, SnDDC shows a good oxidative synergism with DODPA antioxidant. TMOT results indicates that the combination of SnDDC and DODPA in polyalphaolefin can also effectively reduce the weight lost, carbonyl peak square index and diposits of oxidized oils, which confirm that the combination of SnDDC and DODPA exhibit good synergistic antioxidation properties and deposits inhibition.

The phase behaviour of lipid X at high water concentration

1990 ◽  
Vol 68 (1) ◽  
pp. 345-351 ◽  
Author(s):  
G. Lipka ◽  
H. Hauser
Keyword(s):  
Differential Scanning Calorimetry ◽  
Hexagonal Phase ◽  
Water Concentration ◽  
Critical Micellar Concentration ◽  
High Water ◽  
Phase Behaviour ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Repeat Distance ◽  
X Ray

The phase behaviour of lipid X at high water concentrations (> 60%) is studied using mainly differential scanning calorimetry (DSC) and X-ray diffraction. The critical micellar concentration (CMC) decreases from 8 × 10−5 M at −2 °C to 4 × 10−5 M at 20 °C. The critical micellar temperature (CMT) is 0 °C and decreases slightly with increasing lipid X concentration. Above the CMC and below the CMT, lipid X forms a lamellar gel phase (Lβ). Above 0 °C and at concentrations ranging from the CMC up to about 0.2 M (20%), lipid X forms small micelles. At even higher concentrations there is a transition to a hexagonal phase, probably hexagonal I. Addition of excess NaCl to lipid X dispersions at concentrations < 0.2 M (20%) has several effects on the phase behaviour of lipid X. (i) The lamellar phase is stabilized up to temperatures of ≈20 °C at [NaCl] ≥ 0.7 M. (ii) NaCl induces a tighter packing of the hydrocarbon chains. (iii) At concentrations > 0.7 M NaCl, the bilayer repeat distance decreases to about 43 Å (1 Å = 0.1 nm).Key words: lipid X, phase behaviour, effects of NaCl, differential scanning calorimetry, X-ray diffraction.

scholarly journals Vibrational Spectroscopic Study of the Cocrystal Products Formed by Cinchona Alkaloids with 5-Nitrobarbituric Acid

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Harry G. Brittain
Keyword(s):  
Differential Scanning Calorimetry ◽  
Molecular Complexes ◽  
Ring System ◽  
Cinchona Alkaloids ◽  
Infrared Absorption Spectroscopy ◽  
Quinoline Ring ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Structural Types ◽  
Chemical Microscopy

X-ray powder diffraction, differential scanning calorimetry, infrared absorption spectroscopy, and Raman spectroscopy have been used to study the phenomenon of cocrystal formation in the molecular complexes formed by 5-nitrobarbituric acid with four cinchona alkaloids. The cocrystal products were found to contain varying degrees of hydration, ranging from no hydration in the nitrobarbiturate-quinidine cocrystal up to a 4.5-hydrate species in the nitrobarbiturate-cinchonine cocrystal. For the nitrobarbiturate cocrystals with cinchonine, cinchonidine, and quinidine, the predominant interaction was with the quinoline ring system of the alkaloid. However, for quinine, the predominant interaction was with the quinuclidine group of the alkaloid. These properties serve to demonstrate the utility of 5-nitrobarbituric acid as a preferred reagent for chemical microscopy, since the differing range of hydrate and structural types would serve to easily differentiate the cinchona alkaloids from each other, even when different compounds contained the same absolute configurations at their dissymmetric centers.

Differential scanning calorimetry and X-ray diffraction studies of a series of synthetic β-D-galactosyl diacylglycerols

1991 ◽  
Vol 69 (12) ◽  
pp. 863-867 ◽  
Author(s):  
D. A. Mannock ◽  
R. N. McElhaney
Keyword(s):  
Phase Transition ◽  
Differential Scanning Calorimetry ◽  
Phase Behaviour ◽  
Lipid Phase ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Phase Transition Temperatures ◽  
Bonding Properties ◽  
Lower Temperature

We have investigated the physical properties of a homologous series of synthetic, saturated 1,2-di-O-acyl-3-O-(β-D-galactopyranosyl)-sn-glycerols using calorimetry and X-ray diffraction. Unannealed aqueous dispersions of these compounds exhibit a lower temperature, moderately energetic, chain-melting (Lβ/Lα phase transition and a higher temperature, weakly energetic, bilayer/nonbilayer phase transition. On annealing below the Lβ/Lα phase transition, the Lβ phase converts to an LC phase, which may undergo a highly energetic LC/Lα or LC/HII phase transition at very high temperatures on reheating. The temperatures of these phase transitions are higher than those seen in the corresponding α- and β-D-glucosyl diacylglycerols. However, the Lβ/Lα and bilayer/nonbilayer phase transition temperatures of the β-D-galactosyl diacylglycerols are lower than those of the corresponding diacyl phosphatidylethanolamines. These observations are discussed in terms of the hydration and hydrogen bonding properties of their respective headgroups.Key words: differential scanning calorimetry, low-angle x-ray diffraction, glycolipids, galactolipids, lipid phase behaviour.

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