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At least 19 recordsLinked to original sources
PubMed1979

Thermal stability of fatty acid-serum albumin complexes studied by differential scanning calorimetry.

Differential scanning calorimetry has been used to study the thermal stability of bovine serum albumin as affected by binding of fatty acids (lauric acid and stearic acid) and sodium dodecyl sulfate (SDS). All the ligands stabilized the protein molecules in a similar manner, but to different levels. A maximum increase in denaturation temperature of 30 degrees C was obtained with lauric acid. The thermograms indicate the presence of several ligand-albumin complexes having different heat stabilities. Variations in pH in 0.9% NaCl affected the heat stability of both ligand-poor and ligand-rich albumin, the former being more sensitive to variations in pH within the physiological range. Variations in NaCl concentration affected the thermal stabilities at neutral pH, expecially at low salt concentrations. While ligand-rich albumin was somewhat destabilized by increasing NaCl concentrations, ligand-poor albumin was strongly stabilized. The potential use of differential scanning calorimetry in ligand-albumin research is discussed.

Animals↗
PubMedDate not supplied

Solid state side chain transitions of poly(alpha-amino acids). I. Investigation by differential scanning calorimetry.

The differential scanning calorimetric behavior of a series of alpha-amino acid homopolymers and copolymers was investigated in the range of temperature from -80 to +130 degrees C. The following polymers have been examined: poly(N'-carbobenzoxy-L-lysine), poly(O-carbobenzoxy-L-tyrosine), random copolymers of O-carbobenzoxy-L-tyrosine and N'-carbobenzoxy-L-lysine, poly(Ngamma-carbobenzoxy-L-diaminobutyric acid), and poly(N sigma-carbobenzoxy-L-ornithine). Each sample exhibited a prominent glass-like transition between +30 and +60 degrees C with a specific heat increment deltacp of the order of 0.03-0.11 cal/(g degrees C). Endothermal peaks, developed by annealing, have been also been revealed. It is concluded that in poly(alpha-amino acids) side chain motions are capable of undergoing glass-like transition.

Aminobutyrates↗
PubMed1976

Investigation of phase transitions of lipids and lipid mixtures by sensitivity differential scanning calorimetry.

High sensitivity differential scanning calorimetry is applied to the study of the thermotropic behavior of mixtures of synthetic phospholipids in multilamellar aqueous suspensions. The systems dimyristoylphosphatidylcholine dipalmitoylphosphatidylcholine, and dimyristoylphosphatidylethanolamine-distearoylphosphatidylcholine, although definitely nonideal, exhibit essentially complete miscibility in both gel and liquid crystalline states, while the system dilauroylphosphatidylcholine-distearoylphosphatidylcholine is monotectic with lateral phase separation in the gel state. Comparison of the observed transition curves with theoretical curves calculated from the calorimetrically determined phase diagrams supports a literal interpretation of the phase diagrams.

Calorimetry↗
PubMed1977

Studies of the lipid phase transitions of Escherichia coli by high sensitivity differential scanning calorimetry.

High sensitivity adiabatic differential scanning calorimetry was performed on lipids, membrane vesicles, and whole cells of Escherichia coli enriched in particular unsaturated fatty acids by genetic means. Information concerning the shape of the transition is discussed. Transitions with an asymmetric shape reminiscient of a second order transition were observed. Comparison between the lipid transition observed in whole cells, membrane vesicles, and extracted lipids enriched in elaidate reveal some basic similarities. Studies of synthetic lipids were undertaken in an attempt to interpret the shapes of these transitions as a function of the lipid components of the membrane.

Calorimetry↗
PubMed1978

Differential scanning calorimetry of rat liver mitochondria.

Differential scanning calorimetry was employed for studying rat liver mitochondria and extracted mitochondrial lipids. Endothermic transition in the range 15--40 degrees C was detected for the whole mitochondria and between 10--20 degrees C for the extracted lipids.

Animals↗
PubMed1979

Differential scanning calorimetry of chromaffin granule membranes.

Differential scanning calorimetry thermograms of native chromaffin granule membranes exhibit several peaks in the 15-35 degrees C region. Extraction of cholesterol increases the size of the melting peaks. Addition of Ca2+ ions does not seem to influence the lipid transitions.

Animals↗
PubMed1977

Differential scanning calorimetry of the thermal denaturation of lactate dehydrogenase.

1. Differential scanning calorimetry has been used to study the thermal denaturation of lactate dehydrogenase. At pH 7.0 in 0.1 M potassium phosphate buffer, only one transition was observed. Both the enthalpy of denaturation and the melting temperature are linear function of heating rate. The enthalpy is 430 kcal/mol and the melting temperature 61 degrees C at 0 degrees C/min heating rate. The ratio of the calorimetric heat to the effective enthalpy indicated that the denaturation is highly cooperative. Subunit association does not appear to significantly contribute to the enthalpy of denaturation. 2. Both cofactor and sucrose addition stabilized the protein against thermal denaturation. Pyruvate addition produced no changes. Only a small time-dependent destabilization was observed at low concentrations of urea. Large effects were observed in concentrated NaCl solutions and with sulfhydryl-modified lactate dehydrogenase.

Animals↗
PubMed1991

Computer-controlled differential scanning calorimetry of dental composites.

In this paper, computer-controlled differential scanning calorimetry has been used to evaluate the heat liberated and the temperature rise associated with the light cure of selected dental composites. In addition, the effect of postcure heating and increased ambient temperature of light cure are examined in terms of potential secondary cure. The results indicate significant differences between the mean heats of cure of different composites, primarily reflecting the filler fraction variations of the composites. In addition, increased cure activity appears to result from both postcure heating as well as thermal activation due to higher ambient temperature of light cure. The results are analyzed and attributed to variations in resin phase composition and resin content per unit weight of composite as well as thermally induced enhancement of cure.

Calorimetry, Differential Scanning↗
PubMed1991

Thermal denaturation of whole cells and cell components of Escherichia coli examined by differential scanning calorimetry.

Thermograms of whole cells of Escherichia coli obtained by differential scanning calorimetry contained ten main peaks (denoted f, l, m1, m2, m3, n, p, q, r and s) occurring at temperatures of approximately 25, 54, 61, 71, 76, 81, 95, 105, 118 and 124 degrees C, respectively. After cooling to 5 degrees C and reheating, peaks denoted fr, mr and pr were observed at 23, 73 and 94 degrees C, respectively. By examining thermograms of different cell fractions we have identified the following thermal denaturation events. During primary heating there is a broad endotherm (f) beginning below 20 degrees C and extending to just above 40 degrees C that is caused by melting of membrane lipids. Superimposed on this is an exothermic process associated with a change of state of the peptidoglycan. The first irreversible denaturation event occurs just above 47 degrees C, associated with the onset of denaturation of the 30S ribosomal subunit and soluble cytoplasmic proteins. Ribosome melting is a complex process occurring between 47 and 85 degrees C and is characterized by peaks m1, m2 and n. Peak m3 at 75-76 degrees C is of unknown identity but may possibly represent melting of tRNA. Peak p at 95 degrees C results from melting of a portion of the cellular DNA combined with denaturation of a cell wall component. Peak q at 105 degrees C is multicomponent and may be caused by melting of a different region of DNA together with denaturation of another cell wall component. The complex events denoted r and s at 118 and 125 degrees C, respectively, are associated with denaturation of a component of the cell envelope, and possibly also of DNA. Following cooling and reheating there is a broad endotherm with a maximum at 23 degrees C caused by remelting of membrane lipid and a very broad endotherm extending between 40 and 100 degrees C caused by the remelting of ribosomal RNA. Peak pr at 94 degrees C is caused by the melting of reannealed DNA. Additional features not appearing in whole cells were evident in some cell fractions. These observations should allow us to distinguish events that may lead to loss of viability from those that do not.

Bacterial Proteins↗
PubMed1992

Heat killing of bacterial spores analyzed by differential scanning calorimetry.

Thermograms of the exosporium-lacking dormant spores of Bacillus megaterium ATCC 33729, obtained by differential scanning calorimetry, showed three major irreversible endothermic transitions with peaks at 56, 100, and 114 degrees C and a major irreversible exothermic transition with a peak at 119 degrees C. The 114 degrees C transition was identified with coat proteins, and the 56 degrees C transition was identified with heat inactivation. Thermograms of the germinated spores and vegetative cells were much alike, including an endothermic transition attributable to DNA. The ascending part of the main endothermic 100 degrees C transition in the dormant-spore thermograms corresponded to a first-order reaction and was correlated with spore death; i.e., greater than 99.9% of the spores were killed when the transition peak was reached. The maximum death rate of the dormant spores during calorimetry, calculated from separately measured D and z values, occurred at temperatures above the 73 degrees C onset of thermal denaturation and was equivalent to the maximum inactivation rate calculated for the critical target. Most of the spore killing occurred before the release of most of the dipicolinic acid and other intraprotoplast materials. The exothermic 119 degrees C transition was a consequence of the endothermic 100 degrees C transition and probably represented the aggregation of intraprotoplast spore components. Taken together with prior evidence, the results suggest that a crucial protein is the rate-limiting primary target in the heat killing of dormant bacterial spores.

Bacillus megaterium↗
PubMed1977

Differential scanning calorimetry and enzymic activity of rat liver microsomes in the presence and absence of delta1-tetrahydrocannabinol.

The thermal transitions of rat liver microsomes and isolated lipids were investigated by using differential scanning calorimetry. Endothermic transitions at approximately-5 degrees C and between approximately18 degrees and 40 degrees C were detected in the membranes and at approximately-10 degrees C and between approximately 10 degress and 20 degrees C in the extracted lipids. Interaction with delta1-tetrahydrocannabinol of microsomal membranes and of extracted lipids influences the thermotrophic behaviour as revealed by differential scanning calorimetry and eliminates the break in the Arrhenius plot of the enzymic activity of O-demethylase.

Animals↗
PubMed1992

Evaluation of the physical stability of freeze-dried sucrose-containing formulations by differential scanning calorimetry.

Freeze-dried samples of sucrose with buffer salts, amino acids, or dextran have been analyzed with differential scanning calorimetry (DSC) to evaluate the use of DSC thermograms in predicting the physical storage stability. The glass transition temperature, Tg, of the amorphous cake, crystallization, and melting of sucrose are observed with DSC. Tg appeared to be an important characteristic of the physical stability of the amorphous freeze-dried cake. A storage temperature above Tg results in collapse or shrinkage of the cake, which for a sucrose-based formulation, may be accompanied by crystallization of the sucrose. The Tg of the amorphous sucrose is influenced by other components present in the cake. Dextran-40 raised Tg, while the addition of glycine to the formulation lowered Tg. The residual moisture content strongly influences Tg, since water acts as a plasticizer of the system; the higher the moisture content, the lower the Tg and the less physically stable the freeze-dried cake. Crystallization of amorphous sucrose is shown to be inhibited by high molecular weight components or ionic compounds. DSC analysis of freeze-dried cakes proved to be a powerful tool in formulation studies.

Alcohols↗