Calorimetric Estimates Research Articles

Nucleotide binding-promoted conformational changes release a nonnative polypeptide from the Escherichia coli chaperonin GroEL.

The Escherichia coli chaperonins GroEL and GroES facilitate the refolding of polypeptide chains in an ATP hydrolysis-dependent reaction. The elementary steps in the binding and release of polypeptide substrates to GroEL were investigated in surface plasmon resonance studies to measure the rates of binding and dissociation of a normative variant of subtilisin. The rate constants determined for GroEL association with and dissociation from this variant yielded a micromolar dissociation constant, in agreement with independent calorimetric estimates. The rate of GroEL dissociation from the nonnative chain was increased significantly in the presence of 5'-adenylylimidodiphosphate (AMP-PNP), ADP, and ATP, yielding maximal values between 0.04 and 0.22 s(-1). The sigmoidal dependence of the dissociation rate on the concentration of AMP-PNP and ADP indicated that polypeptide dissociation is limited by a concerted conformational change that occurs after nucleotide binding. The dependence of the rate of release on ATP exhibited two sigmoidal transitions attributable to nucleotide binding to the distal and proximal toroid of a GroEL-polypeptide chain complex. The addition of GroES resulted in a marked increase in the rate of nonnative polypeptide release from GroEL, indicating that the cochaperonin binds more rapidly than the dissociation of polypeptides. These data demonstrate the importance of nucleotide binding-promoted concerted conformational changes for the release of chains from GroEL, which correlate with the sigmoidal hydrolysis of ATP by the chaperonin. The implications of these findings are discussed in terms of a working hypothesis for a single cycle of chaperonin action.

Calorimetric Estimates of Construction Cost and Their use in Ecological Studies

Photosynthetic carbon fixation is the most abundant form of autotrophic energy capture on earth, and thus plant biomass represents the single largest pool of energy available for trophic level transfers. Energy partitioning, allocation and content influence both plant form and function, setting the stage for trophic level transfers. In many ways energy is the most basic unit that can be used to compare organisms, spanning studies of biomolecules, cells, organs, tissues, individuals, populations, communities, ecosystems and global dynamics. It is not surprising that early ecologists devoted much attention to the direct measure of the energy contents of plants. What is more surprising is that so few recent studies have expanded on the early work to incorporate more mechanistic measures of energy requirements. The concept of construction cost, or the total substrate requirement for the biosynthesis of an endproduct, has been attributed to Pasteur (1875, as cited in Penning de Vries, Brunsting & van Laar 1974). In 1987 Williams et al. defined construction cost as a measure of the amount of glucose required to provide carbon skeletons, reductant and adenosine 5'-triphosphate (ATP) for the synthesis of organic compounds, and formulated a set of techniques and equations to estimate the construction cost of plants. These researchers found that the energy required to form plant tissues can easily be estimated from simple measurements of the heat of combustion, ash content and organic nitrogen content. Prior to publication, the method was used in an extensive study of common Spanish plants (Merino 1987), but since publication, the technique has been cited only 25 times in the primary literature and twice in textbooks (Science Citation Index to July 1993). Of these citations, only half actually used the technique. The ecological significance of construction cost has only begun to be studied. Of the 25 papers that have cited Williams et al. (1987), nearly one-third were primarily concerned with modelling (Nobel 1991; Nobel, Lopez & Alm 1991; Raich et al. 1991; Ryan 1991; Webb 1991a,b;

On-Line Estimation of Thermal Balance for Batch Crystallizations: Results and Perspective

This paper describes an on-line recursive policy for the estimation of the differential heat of crystallization during batch evaporative crystallizations. Bench-scale experimental results are reported. The obtained calorimetric estimate is shown to be a powerful tool for advanced control of industrial crystallizers, as for process studies. Several new perspectives are briefly envisaged.

Application of on-line calorimetry to the advanced control of batch crystallizers

For batch crystallizers cooled through vacuum, the advanced tracking of temperature trajectories, which involves severe non-linear and non-stationary features, is somewhat difficult to achieve. A generalized predictive control law has been applied to a bench-scale plant and, for the sake of control robustness and process safety, an adaptive supervisor was designed. A major problem in unseeded batch crystallizers being to detect the nucleation, an estimate of the crystallization heat flow is computed through on-line calorimetry by using a recursive least-squares identification algorithm. So, relevant real-time information is provided which is successfully applied to monitor the setpoint pressure of the evaporative crystallizer. Besides process control, it is shown that calorimetric estimates are of great interest in real-time batch crystallization analysis and diagnosis.

Thermochemical Aspects of Water/n-Octanol Partitioning of Some Local Anaesthetic Agents.

The water/n-octanol partitioning thermodynamic parameters of some local anaesthesic agents are determined through a calorimetric estimation of the enthalpies of transfer. Partitionings are entropy-driven. Although no single mechanism of transfer can be ascribed, the mechanisms seem identical for each subfamily of the same kind of structure.

Allometry of cooling, supercooling, and freezing in the freeze-tolerant turtle Chrysemys picta

Although several vertebrates are freeze tolerant, little is known of the relationship between body size and the kinetics of cooling and freezing. We compared these responses for six hatchling and eight adult Chrysemys picta from an Ohio population. All turtles initially recovered from freezing, and all adults, but only two hatchlings (which experienced ice contents of approximately 35%), exhibited long-term survival. Rapid thawing may have compromised hatchling survival. Turtle water content was inversely related to body mass, but we found no significant correlation between the extent of supercooling and body size. Prefreezing and postfreezing cooling rates scaled with body mass to the -0.55 and -0.40 power, respectively, but the latter rate was more than two orders of magnitude slower. Theoretical (assuming 20% bound water) and calorimetric estimates of body ice agreed reasonably well. Ice contents were both body mass and time dependent. The absolute rate of ice formation scaled with body mass to the 0.4 power. Body size strongly influences the freezing response of ectotherms and deserves more attention.

Body heat storage in steers (Bos taurus) in fluctuating thermal environments

SUMMARYHeat stored in the body of cattle subjected to a daily 10 CC range of environmental temperature was measured by calorimetry and thermometry. The daily range of bodycore temperature of the animals was of the order of 0·5 °C but mean skin temperature cycled with a range of approximately 6 °C. Calorimetric estimates of changes in mean body temperature showed good agreement with thermometric estimates when core and mean body temperature changes were weighted in the ratio a: (1 – α) where α was found to be 0·85. This result is consistent with the findings of another study where cattle were subjected to abrupt changes in environmental temperature, the combined best estimate of a from the two studies being 0·86 ± 0·014 (s.E.). The 10 °C range of daily environmental fluctuation resulted in a daily variation of approximately 1 °C in mean body temperature, which is equivalent to the amount of heat produced by the animals every 40 min. It is suggested that a weighting factor α = 0·86 could be employed, using thermometry only, to estimate fluctuations in body heat storage which are likely to occur in animals subjected to fluctuating environmental conditions in the field.

Calorimetric estimate of the enthalpy change for the substrate-promoted conformational transition of aspartate transcarbamoylase from Escherichia coli.

Calorimetric estimate of the enthalpy change for the substrate-promoted conformational transition of aspartate transcarbamoylase from Escherichia coli.

Determination of the equilibrium constants of water-methanol deuterium exchange reactions from vapour pressure measurements

The equilibrium constant of the reaction2CH3OH(l) + D2O(l) → 2CH3OD(l) + H2O(l) is obtained from vapour pressure measurements. The value, 1.09k0.02 at 298 K, is in satisfactory agreement with calculated values and with calorimetric estimates. Vapour pressures at 298.14 K are reported for the systems H2O + CH3OH, H2O+CH3OD, D2O + CH3OH and D2O+ CH3OD. Molar excess Gibbs functions are obtained from these vapour pressures.

Vapour Pressure Study of Deuterium Exchange Reactions in Water-Ethanol Systems: Equilibrium Constant Determination

A method is proposed for the determination of the equilibrium constants of liquid-phase deuterium exchange reactions from vapour pressure measurements. It is applied to water-ethanol systems to give the equilibrium constant of the reaction 2C2H5OH(l) + D2(l) → 2C2H5OD(l) + H2O(l) The value obtained, 1.05+0.02 at 298 K, is significantly greater than the 'random' value and is more precise and reasonable than a recent calorimetric estimate. Vapour pressures at 298.14 K are reported for the systems H2O+C2H5OH, H2O+C2H5OD, D2O + C2H5OH and D2O + C2H5OD. Molar excess Gibbs functions are obtained from these vapour pressure measurements.

Dosages colorimétriques des oxydoréductase aldoniques d' Escherichia coli K 12 : Applications

Calorimetric estimations of aldonate oxidoreductases from Escherichia coli K 12 : Applications Altronate (EC 1.1.1.58) and mannonate oxidoreductases (EC 1.1.1.57), two NAD + enzymes involved in the hexuronate pathway of E. coli K 12, respectively catalyze the reversible dehydrogenation of altronate or mannonate into tagaturonate or fructuronate. 1. 1. The optimal conditions for quantitative colorimetric assays of these activities utilizing phenazine methosulfate as an intermediate agent for electron transfer from NADH to p-nitro blue tetrazolium have been determined. In 02 M glycylglycine buffer (pH 9.0) in the presence of gelatin (10 or 20 μg/ml), phenazine methosulfate (33μM) and 3,3′-(3,3′-dimethoxy-4,4′-biphenylene)-bis[2-( p-nitrophenyl)-5-phenyl-2H-tetrazolium] (0.25 or 05. mM), the apparent Michaelis constant for substrates are: K m (NAD + = 88 μM and K m ( altronate) = 90 μM for altronate oxidoreductase; K m (NAD +) = 1 mM and K m (mannonate) = 1.7 mM for mannonate oxidoreductase. 2. 2. Applications for these new methods in various fields such as aldonate estimations, rapid and visual detection of aldonate oxidoreductases and characterization specific mutants in the hexuronate pathway of E. coli are discussed.

Maintenance energy requirement of grazing sheep in relation to herbage availability. I. Calorimetric estimates

Grazing pressure on three pastures was adjusted so that the mean liveweights (W) of three groups of 10 Merino wethers, initially uniform, were kept at nominally 45, 35, and 25 kg. Daily rates of energy expenditure were calculated by measuring the respiratory gaseous exchanges of tracheostomized sheep in each group, and from estimates of CO2 entry rate determined during constant infusion with NaH14CO3. These measurements were made during a period of 3 weeks when the sheep had been at constant W for 9 months, and during a further 3 weeks beginning 30 days after the sheep were shorn. Further measurements were made in two periods of 7 days after animals had been interchanged between groups so that W was increasing in some animals and decreasing in others. Maintenance requirements of all sheep, indicated by the energy expenditures during the periods at constant W, were described by the equation M = 45.1 W + 256, where M is the estimated metabolizable energy requirement in kilocalories per 24 hr. Similar results were obtained during the two periods when W was changing. The requirements were in general 60–70% greater than those for housed sheep of similar W and are discussed in relation to the climatic environment, the condition of the sheep, and the availability of herbage.

A colorimetric estimation of lipopolysaccharides

The lipopolysaccharides of Gram-negative bacteria are not confined to cell walls but may accumulate in culture fluids of cells grown under certain conditions [l-3] . Study of this accumulation has been aided by development of a calorimetric estimation for lipopolysaccharides which is specific, sensitive and technically simple in comparison with methods hitherto used for such studies [2,4-61. The estimation is based on a spectral shift in an acidic solution of a cationic carbocyanine dye. This type of dye, absorbing at 5 10 nm, is known to undergo spectral shifts to longer wavelengths when reacted with polyanions such as proteins, nucleic acids and acidic polysaccharides [7]. Such shifts are the basis for the estimation of acidic polysaccharides [8] . Spectral shifts to shorter wavelengths (about 470 M-I) result from reactions of the dye with solutions containing lipopolysaccharides ]91 * The present communication describes a calorimetric analytical procedure, based on the spectral shift, which was applicable to solutions containing 110 c(g of lipopolysaccharide preparations of various origins and complexity. It could also be used directly to estimate lipopolysaccharide in culture fluids from the lysine auxotroph, E. coli ATCC 12408.

A calorimetric estimate of the efficiency of utilisation of dietary energy by the growing cockerel.

Synopsis The metabolic rates of four growing cockerels, aged between 10 and 18 weeks, were measured using respiration calorimetry. Measurements were made when the birds had been fasted for 48–72 h and when they had been given a cereal‐type diet at maintenance and production levels. The mean fasting heat production (±SE) was 92.3 (±5.0) kcal/kg d or 113.4 (±5.7) kcal/kg3/4 d. The relationship between energy balance (T) and ME intake (X) was calculated to be Y = 0.851X—92.9 indicating that the maintenance ME requirement was 109.1 kcal/kg d and that the net availability of the ME was 85.1 per cent. The efficiency of energy utilisation in relation to plane of nutrition and to the amount of protein and fat deposited is discussed.

Calorimetric measurement of free energy utilization by Nitrosomonas and Nitrobacter.

Calorimetric estimates of the utilization efficiency of the free-energy derived from substrate oxidation by cell suspensions of two nitrifying bacteria, Nitrosomonas and Nitrobacter, provided two ranges of values: 11 to 27% and 15 to 51%, respectively. About 15 to 30% of the utilized free-energy is used for driving endergonic reactions other than CO2 fixation, probably the synthesis of polyphosphates. The molar heat of substrate oxidation does not seem to be influenced by the age of cells harvested during growth or by the length of the incubation period during which cells have been kept in a buffer suspension in a starved condition. The loss of respiratory activity measured either by oxygen uptake or heat evolution in the presence of the specific substrate, nitrite or ammonium, decreases according to kinetics which are influenced by the aerobiosis of the suspension. The viability of the starved cells decreases in a way which is similar to that of the respiratory activity. It seemed impossible to obtain cells which had lost their viability but kept the ability to oxidize their substrate. Two inhibitors of the respiratory chain, quinacrine and cyanide, are without effect on the molar heat of substrate oxidation and consequently on the free-energy utilization efficiency. 2.4 dinitrophenol did decrease the rate of heat evolution during substrate oxidation at concentrations at which the rate of oxygen uptake was not depressed, with the consequences that free-energy efficiency was apparently increased.

溶融池温度に関するChristensen, Chipmanの論文について(カロリメータによる測定結果についての批判)

It is pointed out that the calorimetric estimation of the welding pool temperature described in Christensen and Chipman's report concerning slag-metal interaction in the pool is based on the misuse of the result of Wells's paper which treats the two dimensional heat flow in welding. Wells's paper shows that M=q/c pvdTf approaches 2 when vd/2α takes large values. Using this fact, they calculated the temperature considering q/2 is the heat content of the nugget when the nugget is in molten state, q being measured calorimetrically. It is clear, however, that the above mentioned Wells's result does not mean that q/2 is the heat content of the molten pool.

AN APPARATUS FOR CONTINUOUS DIRECT AND INDIRECT CALORIMETRIC ESTIMATIONS OF NEWBORNS AND PREMATURES UNDER DIFFERENT ENVIRONMENTAL CONDITIONS.

AN APPARATUS FOR CONTINUOUS DIRECT AND INDIRECT CALORIMETRIC ESTIMATIONS OF NEWBORNS AND PREMATURES UNDER DIFFERENT ENVIRONMENTAL CONDITIONS.

THE COLORIMETRIC DETERMINATION OF HEXOSES WITH CARBAZOLE

The optimum conditions for the calorimetric estimation of hexoses by reaction with carbazole in hot sulfuric acid solution have been determined and a convenient procedure, giving results with a precision of 2 to 5 per cent in the range of 50 to 150 γ of glucose, is described. The colors obtained with glucose, galactose, fructose, and mannose are not sufficiently distinctive to allow their ready differentiation and identification by spectral measurements. The significance of the ultraviolet spectra of heated and unheated sulfuric acid solutions of hexoses to the problem of estimation and identification of hexoses is discussed.

Combination of Wool Protein with Acid and Base: The Effect of Tem perature on the Titration Curve

A description has previously been given of the relation bctwcen the amounts of hydrochloric acid and of potassium Hydroxide bound by wool and the concentration of these substances in solution. These measurements were made at 0° C in order to avoid com plications due to decomposition. However, when wool is exposed to acid or base in the course of carbonizing, acid-dyeing, milling, and scouring much more elevated temperatures prevail. It is therefore desirable to determine the temperature dependence of the relations previously described. It is also desirable to compare the relative magnitudes of the effect of temperature on the amounts of acid and on the amounts of base combined, in order to establish the correctness of assumptions as to the mechanism of combination previously made in explaining the results obtained at 0' C.With the purpose of providing this information, measurements of the amounts of hydrochloric acid and potassium hydroxide bound by wool as a function of acidity and salt concentration, at 0°, 25° and 50° C, are now reported. In order to eliminate effects due to decomposition of the wool in alkaline solutions, a study was also made of the effect of temperature on the rate of decomposition of the wool. The results obtained support the assumption previously made that the carboxyl groups and amino groups of wool in the uncombined state are completely ionized. This conclusion follows from the observation that changes in the amounts of acid bound brought about by changes in temperature are small, which indi cates that combination with acid is equivalent to back-titration of the carboxyl groups, but changes in the amounts of base bound at at given hydrogen ion concentration are large, which indicates that combination with base is equivalent to back-titration of amino groups. Similar results obtained on analogous compounds, render it probable that the direction of the temperature effect on the curve of acid combination reverses at a temperature near 40° C. Thus curves at temperatures used in dyeing are probably not far different from the curves at 0° C, which have been studied in most detail.The heats of dissociation calculated from the magnitudes of the changes with temperature in the curves of combination for the two kinds of groups, are in good agreement with values for these groups in comparable compounds, and in soluble proteins. The value obtained in the acid range is also in good agreement with the results of calorimetric measurements on the combination of acid by wool.It is shown that approximately equal parts of the total heat changes in the acid range are associated with the dissociation of hy drogen ions and of chloride ions from the fibre. An appreciable part of the total heat effect is ascribed to a heat of transfer of the ions between the two phases of the heterogeneous titration system. Neither titrimetric nor calorimetric estimations of the heats of dissociation provides evidence for or against the existence of salt linkages in wool.

III. The thermal method of measuring losses in sheet dielectrics at radio frequencies and high electrical stresses

Summary The measurement of dielectric losses by the calorimetric estimation of the heat produced in a specimen of dielectric when it is subjected to an alternating stress is discussed theoretically The factors affecting the accuracy of the method are examined; the method is obviously best suited for conditions under which appreciable heat is developed, i. e., when there is a high voltage stress of high frequency.