Thermal Hysteresis in Ganglioside Micelles Investigated by Differential Scanning Calorimetry and Light-Scattering

Langmuir ◽  
1999 ◽  
Vol 15 (15) ◽  
pp. 4975-4980 ◽  
Author(s):  
Laura Cantú ◽  
Mario Corti ◽  
Elena Del Favero ◽  
Elke Muller ◽  
Antonio Raudino ◽  
...  
Keyword(s):  
Differential Scanning Calorimetry ◽  
Light Scattering ◽  
Thermal Hysteresis ◽  
Scanning Calorimetry

Photophysical properties of microencapsulated phthalocyanines

2010 ◽  
Vol 14 (03) ◽  
pp. 278-283 ◽  
Author(s):  
Virginia E. Diz ◽  
Gabriela A. Gauna ◽  
Cristian A. Strassert ◽  
Josefina Awruch ◽  
Lelia E. Dicelio
Keyword(s):  
Differential Scanning Calorimetry ◽  
Light Scattering ◽  
Quantum Yield ◽  
Fluorescence Quantum Yield ◽  
Photophysical Properties ◽  
Oxygen Production ◽  
Electronic Microscopy ◽  
Scanning Calorimetry ◽  
Singlet Molecular Oxygen ◽  
Photophysical Parameters

Lipophilic substituted zinc(II) phthalocyanines: 2,3,9,10,16,17,23,24-octakis[(N,N-dimethylaminoethylsulfanyl)]phthalocyaninatozinc(II) (S1) and tetrakis(N,N-dibutylaminoethoxy)phthalocyaninatozinc(II) (3) were incorporated into soybean L-α-phosphatidylcholine (SPC) liposomes of 100 nm diameter. Liposomes were characterized by static light scattering (SLS), transmission electronic microscopy (TEM), and differential scanning calorimetry. The fluorescence quantum yield and singlet molecular oxygen production of 3 are Φ F = 0.15 and ΦΔ = 0.24, respectively, whereas the same photophysical parameters for S1 are Φ F = 0.13 and ΦΔ = 0.51. Higher values of Φ F and ΦΔ are obtained in organic solvent for both dyes. Synthesis of compound 3 has also been reported.

Discovery of an antifreeze protein in the leaves of Ammopiptanthus nanus

2010 ◽  
Vol 90 (1) ◽  
pp. 35-40 ◽  
Author(s):  
S. Yu ◽  
L. Yin ◽  
S. Mu
Keyword(s):  
Differential Scanning Calorimetry ◽  
Thermal Hysteresis ◽  
Large Subunit ◽  
Antifreeze Proteins ◽  
Cold Climate ◽  
High Definition ◽  
Scanning Calorimetry ◽  
Bisphosphate Carboxylase ◽  
Thermal Hysteresis Activity ◽  
Ammopiptanthus Nanus

Overwintering plants produce antifreeze proteins (AFPs) that allow plants to survive under freezing or sub-freezing conditions. Ammopiptanthus nanus (M. Pop.) Cheng f. grows in the desert of Xinjiang, P.R. China, and our objective was to determine if its survival was dependent on AFP and to identify the protein. Using anion exchange and gel filtration, the AFP was extracted, isolated and purified from cold-acclimated A. nanus leaves. The thermal hysteresis activity (THA) of the antifreeze proteins was measured by differential scanning calorimetry. The THA of the AFP was 0.46°C when the concentration of the protein was 20 mg mL-1. The molecular weight of a band was about 119.24 kDa in SDS-PAGE gel. We detected (P < 0.05) the ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit by analyzing the 119.24 kDa protein using the Waters SYNAPT™ high definition mass spectrometry (HDMS™) System. Our results indicate that there is an AFP in A. nanus leaves, and that it may play a vital role as a defence against the cold climate, thus increasing the chances for survival of A. nanus in its desert habitat.Key words: Thermal hysteresis activity, differential scanning calorimetry, extraction, purification, cold climate, desert habitat

Phase transitions of liposomes: When light meets heat

2021 ◽  
Author(s):  
C S Velez-Saboyá ◽  
J R Guzmán-Sepúlveda ◽  
Jesus Carlos Ruiz-Suárez
Keyword(s):  
Differential Scanning Calorimetry ◽  
Phase Transitions ◽  
Light Scattering ◽  
Dynamic Light Scattering ◽  
Membrane Thickness ◽  
Scanning Calorimetry ◽  
Contraction Process ◽  
Exothermic Process ◽  
Gel Phase ◽  
Derivatives Of

Abstract Phase transitions of liposomes are normally studied by differential scanning calorimetry (DSC). A suspension of liposomes is subjected to an increase (decrease) of temperature and when heat is absorbed (released), the liposomes transit from a gel (liquid) to a liquid (gel) phase. This endothermic (exothermic) process takes place at a temperature called the melting temperature Tm, which is distinctive of the type of lipids forming the vesicles. The vesicles, though, also modify their size in the transition. Indeed, the thickness of the membranes decreases (increases) because carbon tails misalign (align). Concomitant with the modifications in the membrane thickness, the diameter (D) of the liposomes changes too. Therefore, when they are inspected by light, the scattered signal carries information from such dilatation (contraction) process. We performed careful experiments using dynamic light scattering (DLS) as a function of temperature to detect the size changes of different liposomes. Gaussian fits of the derivatives of the D vs T curves coincide within 1% with thermograms, which hints to the possibility of performing thermodynamic studies of lipid systems employing light.

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