scholarly journals Enthalpies of Combustion and Formation of Histidine Stereoisomers

2018 ◽  
Vol 2018 ◽  
pp. 1-6
Author(s):  
A. Neacsu ◽  
D. Gheorghe ◽  
I. Contineanu ◽  
A. M. Sofronia ◽  
F. Teodorescu ◽  
...  
Keyword(s):  
Differential Scanning Calorimetry ◽  
Crystalline State ◽  
Enthalpies Of Formation ◽  
Racemic Mixture ◽  
Group Additivity ◽  
Scanning Calorimetry ◽  
Combustion Energy ◽  
Temperature Range ◽  
Decomposition Reactions ◽  
The Stability

The combustion energy of histidine enantiomers (L and D) and of their racemic mixture was measured experimentally. The following values for the enthalpies of formation corresponding to the crystalline state were derived (L = −451.7, D = −448.7, DL = −451.5 kJ·mol−1), and information concerning their stability was obtained by correlating the values of the above thermochemical quantity with the structure of the molecules by using the group additivity scheme. The samples were characterized using a simultaneous thermogravimetry (TG) coupled with differential scanning calorimetry (DSC) techniques in the temperature range between ambient and beyond melting-decomposition, and the corresponding parameters were calculated. The high values of the decomposition temperatures highlight the stability of the compounds. The decomposition reactions are discussed in terms of DSC and TG data, obtained by us and other researchers.

Specific heats of polymer powders by differential scanning calorimetry

1982 ◽  
Vol 60 (14) ◽  
pp. 1853-1856 ◽  
Author(s):  
Eva I. Vargha-Butler ◽  
A. Wilhelm Neumann ◽  
Hassan A. Hamza
Keyword(s):  
Differential Scanning Calorimetry ◽  
Specific Heat ◽  
Scanning Calorimetry ◽  
Temperature Range ◽  
Specific Heats ◽  
Powdered Form ◽  
Polymer Powders

The specific heats of five polymers were determined by differential scanning calorimetry (DSC) in the temperature range of 300 to 360 K. The measurements were performed with polymers in the form of films, powders, and granules to clarify whether or not DSC specific heat values are dependent on the diminution of the sample. It was found that the specific heats for the bulk and powdered form of the polymer samples are indistinguishable within the error limits, justifying the determination of specific heats of powders by means of DSC.

Dynamic Globularization of α-Phase in Ti6Al4V Alloy during Hot Compression

2014 ◽  
Vol 783-786 ◽  
pp. 584-590 ◽  
Author(s):  
Kalenda Mutombo ◽  
C. Siyasiya ◽  
W.E. Stumpf
Keyword(s):  
Differential Scanning Calorimetry ◽  
Transition Temperature ◽  
Strain Rate ◽  
Alpha Phase ◽  
Ti6al4v Alloy ◽  
Thermodynamic Calculations ◽  
Scanning Calorimetry ◽  
Temperature Range ◽  
Α Phase ◽  
Dsc Thermograms

Ti6Al4V samples were isothermally compressed using a Gleeble(TM) 1500D thermo-mechanical simulator. Differential scanning calorimetry (DSC), microstructural analyses, and thermodynamic calculations were used to investigate the sequence of transformation of β into α or vice-versa and the presence of different phases in the compressed Ti6Al4V sample. Globular alpha phase was revealed in the isothermally compressed sample in addition to martensitic and lamellar α/β structures. The transition temperature range of β into α-phase was determined using the DSC thermograms and thermodynamic calculated diagrams. The fraction of α-phase globulized increased as the strain rate decreased from 0.01s-1 to 10-3s-1, and the spheroidization of the α-phase is only possible in a specific range of deformation temperatures.

Thermotoga neapolitana Homotetrameric Xylose Isomerase Is Expressed as a Catalytically Active and Thermostable Dimer in Escherichia coli

1998 ◽  
Vol 64 (7) ◽  
pp. 2357-2360 ◽  
Author(s):  
J. Michael Hess ◽  
Vladimir Tchernajenko ◽  
Claire Vieille ◽  
J. Gregory Zeikus ◽  
Robert M. Kelly
Keyword(s):  
Escherichia Coli ◽  
Differential Scanning Calorimetry ◽  
Gel Filtration ◽  
Xylose Isomerase ◽  
Thermotoga Neapolitana ◽  
Thermal Transitions ◽  
Scanning Calorimetry ◽  
Catalytically Active ◽  
The Stability ◽  
Tetrameric Form

ABSTRACT The xylA gene from Thermotoga neapolitana5068 was expressed in Escherichia coli. Gel filtration chromatography showed that the recombinant enzyme was both a homodimer and a homotetramer, with the dimer being the more abundant form. The purified native enzyme, however, has been shown to be exclusively tetrameric. The two enzyme forms had comparable stabilities when they were thermoinactivated at 95°C. Differential scanning calorimetry revealed thermal transitions at 99 and 109.5°C for both forms, with an additional shoulder at 91°C for the tetramer. These results suggest that the association of the subunits into the tetrameric form may have little impact on the stability and biocatalytic properties of the enzyme.

Studies on the stability of creatine kinase isozymes

2003 ◽  
Vol 81 (1) ◽  
pp. 9-16 ◽  
Author(s):  
Zhi Guo ◽  
Zheng Wang ◽  
Xicheng Wang
Keyword(s):  
Differential Scanning Calorimetry ◽  
Creatine Kinase ◽  
Freeze Drying ◽  
Biological Significance ◽  
Subunit Interactions ◽  
Scanning Calorimetry ◽  
Gradient Gel Electrophoresis ◽  
The Stability ◽  
Creatine Kinase Isozymes ◽  
Monomer Form

Research on the stabilizing properties of creatine kinase isozymes CK-BB, CK-MB, and CK-MM showed that minor alteration of their sequence and structure influenced their stability significantly. An analysis of the stability of the isozymes in storage after freeze drying indicates that creatine kinase isozymes are all in monomer form because of the loss of subunit interactions. Freeze-drying leads to the oxidization of CK-BB and rearrangement of CK-MB. There are also differences in the unfolding of the isozymes in urea. CK-BB and CK-MB are unfolded in lower urea concentrations than CK-MM. Differences in the thermal unfolding were also examined by differential scanning calorimetry. This paper discusses the potential biological significance of these results.Key words: creatine kinase isozymes, fluorescence, circular dichroism, differential scanning calorimetry, urea gradient gel electrophoresis.

scholarly journals 670. Probing the Stability of rAAV Capsids and Genomic Constructs Using Differential Scanning Calorimetry in Concert With Mobile Phase Modifiers

2015 ◽  
Vol 23 ◽  
pp. S267
Author(s):  
James D. Maratt ◽  
Samantha F. Povlich ◽  
Christopher J. Morrison ◽  
Gwendolyn M. Wilmes ◽  
Samuel C. Wadsworth ◽  
...  
Keyword(s):  
Differential Scanning Calorimetry ◽  
Mobile Phase ◽  
Scanning Calorimetry ◽  
Mobile Phase Modifiers ◽  
The Stability
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