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1
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Inhibition study of adenosine deaminase by caffeine using spectroscopy and isothermal titration calorimetry.

100%
Saboury A. A., Divsalar A., Ataie G., Amanlou M., Moosavi-Movahedi A. A., Hakimelahi G. H.
Acta Biochimica Polonica
|
2003
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vol. 50
|
issue 3
849-855
EN
Kinetic and thermodynamic studies were made on the effect of caffeine on the activity of adenosine deaminase in 50 mM sodium phosphate buffer, pH 7.5, using UV spectrophotometry and isothermal titration calorimetry (ITC). An uncompetitive inhibition was observed for caffeine. A graphical fitting method was used for determination of binding constant and enthalpy of inhibitor binding by using isothermal titration microcalorimetry data. The dissociation-binding constant is equal to 350 μM by the microcalorimetry method, which agrees well with the value of 342 μM for the inhibition constant that was obtained from the spectroscopy method. Positive dependence of caffeine binding on temperature indicates a hydrophobic interaction.
2
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Thermochemical properties of the Fe-analogue of cryolite, Na3FeF6

100%
Nerád I., Mikšíková E.
Open Chemistry
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2007
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vol. 5
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issue 2
508-515
EN
Relative enthalpies for low-and high-temperature modifications of Na3FeF6 and for the Na3FeF6 melt have been measured by drop calorimetry in the temperature range 723–1318 K. Enthalpy of modification transition at 920 K, δtransH(Na3FeF6, 920 K) = (19 ± 3) kJ mol−1 and enthalpy of fusion at the temperature of fusion 1255 K, δfusH(Na3FeF6, 1255 K) = (89 ± 3) kJ mol−1 have been determined from the experimental data. Following heat capacities were obtained for the crystalline phases and for the melt, respectively: C p(Na3FeF6, cr, α) = (294 ± 14) J (mol K)−1, for 723 = T/K ≤ 920, C p(Na3FeF6, cr, β) = (300 ± 11) J (mol K)−1 for 920 ≤ T/K = 1233 and C p(Na3FeF6, melt) = (275 ± 22) J (mol K)−1 for 1258 ≤ T/K ≤ 1318. The obtained enthalpies indicate that melting of Na3FeF6 proceeds through a continuous series of temperature dependent equilibrium states, likely associated with the production of a solid solution. [...]
3
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Evaluation of Aerobic Capacity and Energy Expenditure in Folk Dancers

100%
Maciejczyk M., Feć A.
Human Movement
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2013
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vol. 14
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issue 1
76-81
EN
Purpose. The aim of the study was to evaluate the aerobic capacity and energy expenditure of folk dancers. Methods. The aerobic capacity (VO2max) of four male and four female folk dancers was measured by an incremental treadmill test and energy expenditure was assessed by the linear relationship between heart rate and oxygen uptake as based on indirect calorimetry. Results. The dancers presented good aerobic capacity (VO2max), with men achieving values of 51.8 ± 7.39 ml ∙ kg-1 and women 43.43 ± 3.81 ml ∙ kg-1. Steady-state heart rate during folk dancing was 167.8 ± 16.68 b ∙ min-1 (85.0% ± 8.68% HRmax) for men and 178.3 ± 5.62 b ∙ min-1 (91.0% ± 3.83% HRmax) for women, with energy expenditure at 14.54 ± 2.09 kcal · min-1 and 10.08 ± 2.03 kcal · min-1, respectively. Conclusions. The exercise intensity performed during folk dancing is close to the threshold of decompensated metabolic acidosis. Folk dancing can be quantified as a difficult (for men) and very difficult (for women) form of physical activity; dancers should be physically well-prepared for the high exercise intensity present in folk dancing.
4
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Structure-function relationship of serine protease-protein inhibitor interaction.

88%
Otlewski J., Jaskólski M., Buczek O., Cierpicki T., Czapińska H., Krowarsch D., Smalas A. O., Stachowiak D., Szpineta A., Dadlez M.
Acta Biochimica Polonica
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2001
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vol. 48
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issue 2
419-428
EN
We report our progress in understanding the structure-function relationship of the interaction between protein inhibitors and several serine proteases. Recently, we have determined high resolution solution structures of two inhibitors Apis mellifera chymotrypsin inhibitor-1 (AMCI-I) and Linum usitatissimum trypsin inhibitor (LUTI) in the free state and an ultra high resolution X-ray structure of BPTI. All three inhibitors, despite totally different scaffolds, contain a solvent exposed loop of similar conformation which is highly complementary to the enzyme active site. Isothermal calorimetry data show that the interaction between wild type BPTI and chymotrypsin is entropy driven and that the enthalpy component opposes complex formation. Our research is focused on extensive mutagenesis of the four positions from the protease binding loop of BPTI: P1, P1', P3, and P4. We mutated these residues to different amino acids and the variants were characterized by determination of the association constants, stability parameters and crystal structures of protease-inhibitor complexes. Accommodation of the P1 residue in the S1 pocket of four proteases: chymotrypsin, trypsin, neutrophil elastase and cathepsin G was probed with 18 P1 variants. High resolution X-ray structures of ten complexes between bovine trypsin and P1 variants of BPTI have been determined and compared with the cognate P1 Lys side chain. Mutations of the wild type Ala16 (P1') to larger side chains always caused a drop of the association constant. According to the crystal structure of the Leu16 BPTI-trypsin complex, introduction of the larger residue at the P1' position leads to steric conflicts in the vicinity of the mutation. Finally, mutations at the P4 site allowed an improvement of the association with several serine proteases involved in blood clotting. Conversely, introduction of Ser, Val, and Phe in place of Gly12 (P4) had invariably a destabilizing effect on the complex with these proteases.
5
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Changes of thermal, mechanical and magnetic properties of an amorphous Fe80Cr5B15 alloy during magnetic and structural phase transitions

75%
Kamasa P., Myśliński P.
Open Physics
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2006
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vol. 4
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issue 2
178-186
EN
Thermal, mechanical and thermomagnetic properties associated with the magnetic and structural transition of an amorphous Fe80Cr5B15 alloy are described. The investigation was carried out in a simultaneous dilatometric and thermomagnetic experiment. An anomaly of the thermal expansion coefficient at the Curie point and a change in mechanical properties just before the onset of crystallization are observed. The results are compared with the thermal behavior obtained by differential scanning calorimetry.
6
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Thermodynamics of specific protein-RNA interactions.

75%
Stolarski R.
Acta Biochimica Polonica
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2003
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vol. 50
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issue 2
297-318
EN
Description of the recognition specificity between proteins and nucleic acids at the level of molecular interactions is one of the most challenging tasks in biophysics. It is key to understanding the course and control of gene expression and to the application of the thus acquired knowledge in chemotherapy. This review presents experimental results of thermodynamic studies and a discussion of the role of thermodynamics in formation and stability of functional protein-RNA complexes, with a special attention to the interactions involving mRNA 5' cap and cap-binding proteins in the initiation of protein biosynthesis in the eukaryotic cell. A theoretical framework for analysis of the thermodynamic parameters of protein-nucleic acid association is also briefly surveyed. Overshadowed by more spectacular achievements in structural studies, the thermodynamic investigations are of equal importance for full comprehension of biopolymers' activity in a quantitative way. In this regard, thermodynamics gives a direct insight into the energetic and entropic characteristics of complex macromolecular systems in their natural environment, aqueous solution, and thus complements the structural view derived from X-ray crystallography and multidimensional NMR. Further development of the thermodynamic approach toward interpretation of recognition and binding specificity in terms of molecular biophysics requires more profound contribution from statistical mechanics.
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