After a formal explanation of Mayer's enthalpy balance method as applied to biological reaction rates, the history of its
application is traced from Rubner's dog to accounting for the energy of muscle contraction. The introduction of microcalorimetry
allowed the method generally to be used for cells in vitro and now particular emphasis can be paid to the growth of cells
for the production of therapeutically-important heterologous proteins. In these systems, enthalpy balance studies contribute
to defining catabolic processes, designing media, understanding the mechanisms of growth and controlling cultures using heat
flux as an on-line sensor of metabolic activity.
Authors:Y. Pan, X. Guan, Z. Feng, Y. Wu, and X. Li
A new method was proposed for determining the most probable mechanism function of a solid phase reaction. According to Coats-Redfern's
integral equation Eβ→0 was calculated by extrapolating β to zero using a series of TG curves with different heating rates. Similarly, Eα→0 was calculated according to Ozawa's equation. The most probable mechanism function of the solid phase dehydration of manganese(II)
oxalate dihydrate was confirmed to be G(α)=(1-α)1/2 by comparing Eα→0 with Eβ→0.
Microcalorimeters to monitor the heat dissipation of bench-scale animal cell cultures on line and in real time require a continuous
circuit between the vessel measuring heat flow rate and the bioreactor. The modifications to the transmission lines and calorimetric
heat exchanger were to: (i) reverse the usual upward direction of the cell suspension in the flow vessel to downwards; (ii)
install an in situ washing/cleaning facility; (iii) use low diffusivity PEEK material; and (iv) maintain thermal equilibration
by water-jacketing the transmission tubing. Chemical calibration showed that there was more than a 20% difference between
the physical volume and the effective thermal volume. An appropriate thermodynamic system was defined in order to permit enthalpy
Authors:A. Kidane, Y. Guan, P. Evans, M. Kaderbhai, and R. Kemp
It is claimed, though not without dispute, that genetically engineered mammalian cells grow more slowly than their progenitor
cells because the recombinant gene system causes a metabolic burden. This was found to be the case for CHO cells transfected
with expression vectors forcytochrome b5. The slower growth was associated with lower metabolic activity measured by heat flux and mitochondrial activity (rhodamine
123 fluorescence). The calorimetric-respirometric ratio was similar for all cell types, implying that the greater fluxes of
glucose and glutamine in the recombinant cells was channelled to biosynthesis. This demand probably restricted the supply
of pyruvate to the mitochondria in these cells.
Authors:H. X. Ma, B. Yan, Y. H. Ren, Y. Hu, Y. L. Guan, F. Q. Zhao, J. R. Song, and R. Z. Hu
3,3-Dinitroazetidinium (DNAZ) salt of perchloric acid (DNAZ·HClO4) was prepared, it was characterized by the elemental analysis, IR, NMR, and a X-ray diffractometer. The thermal behavior and decomposition reaction kinetics of DNAZ·HClO4 were investigated under a non-isothermal condition by DSC and TG/DTG techniques. The results show that the thermal decomposition process of DNAZ·HClO4 has two mass loss stages. The kinetic model function in differential form, the value of apparent activation energy (Ea) and pre-exponential factor (A) of the exothermic decomposition reaction of DNAZ·HClO4 are f(α) = (1 − α)−1/2, 156.47 kJ mol−1, and 1015.12 s−1, respectively. The critical temperature of thermal explosion is 188.5 °C. The values of ΔS≠, ΔH≠, and ΔG≠of this reaction are 42.26 J mol−1 K−1, 154.44 kJ mol−1, and 135.42 kJ mol−1, respectively. The specific heat capacity of DNAZ·HClO4 was determined with a continuous Cp mode of microcalorimeter. Using the relationship between Cp and T and the thermal decomposition parameters, the time of the thermal decomposition from initiation to thermal explosion (adiabatic time-to-explosion) was evaluated as 14.2 s.