Temperature thermostability

For maximum accuracy, the manifold and calibrated volumes in a volumetric apparatus should be maintained at constant temperature. Thermostating is not necessary for vacuum micro balances but in helical spring balances the spring should be maintained at constant temperature. Continuous flow apparatus need not be thermostated since the signals are immediately calibrated with known volumes at the same temperature and pressure. However, ambient temperature and pressure must be known to insure accurate calibration. 

Distil through a Vigreux column in a N2 atmosphere maintaining the oil bath temperature thermostated at 135-140°. Check the purity by H NMR [CCI 3. 5 single peak at 13cps from Me4Si. Likely impurities are siloxane hydrolysis products. The azide is thermally stable even at 200° when it decomposes slowly without explosive violence. AH the same it is advisable to carry out the distillation behind a thick... 

Molecular mass Optimum pH pH stability Optimum temperature Thermostability Substrate specificity ... 

The pyrolysis thresholds of this series of compounds show that the thiazole structure is thermostable, decomposition temperatures being generally between 450 and 510°C. Other observations that can be made are ... 

As noted earlier, control of the column s temperature is critical to attaining a good separation in gas chromatography. For this reason the column is located inside a thermostated oven. In an isothermal separation the column is maintained at a constant temperature, the choice of which is dictated by the solutes. Normally, the tern-... 

PGR amplification of a DNA sequence is faciHtated by the use of a heat-stable DNA polymerase, Taq polymerase (TM), derived from the thermostable bacterium Thermus aquaticus. The thermostable polymerase allows the repeated steps of strand separation, primer annealing, and DNA synthesis to be carried out ia a single reactioa mixture where the temperature is cycled automatically. Each cycle coasists of a high temperature step to deaature the template strands, a lower temperature annealing of the primer and template, and a higher temperature synthesis step. AH components of the reaction are present ia the same tube. 

Low Temperature Process. The low temperature process was developed when B. licheniformis and B. stearothermophilus a-amylases became commercially available in the 1970s. These enzymes ate more thermostable, more acidutic, and requite less calcium for stabiUty than the B. subtilis enzyme used in the EHE process. Consequendy, the high temperature EHE heat treatment step was no longer requited to attain efficient Hquefaction. 

Dual-Enzyme Processes. In some cases, especially in symp production in Europe, a Hquefaction process is used that incorporates both a thermostable enzyme and a high temperature heat treatment. This type of process provides better hydrolyzate tilterabiHty than that attained in an acid Hquefaction process (9). Consequendy, dual-enzyme processes were developed that utilized multiple additions of either B. licheniformis or B. stearothermophilus a-amylase and a heat treatment step (see Eig. 1). 

At low temperature, nonionic surfactants are water-soluble but at high temperatures the surfactant s solubUity in water is extremely smaU. At some intermediate temperature, the hydrophile—Hpophile balance (HLB) temperature (24) or the phase inversion temperature (PIT) (22), a third isotropic Hquid phase (25), appears between the oil and the water (Fig. 11). The emulsification is done at this temperature and the emulsifier is selected in the foUowing manner. Equal amounts of the oil and the aqueous phases with aU the components of the formulation pre-added are mixed with 4% of the emulsifiers to be tested in a series of samples. For the case of an o/w emulsion, the samples are left thermostated at 55°C to separate. The emulsifiers giving separation into three layers are then used for emulsification in order to find which one gives the most stable emulsion. 

Effect of Temperature and pH. The temperature dependence of enzymes often follows the rule that a 10°C increase in temperature doubles the activity. However, this is only tme as long as the enzyme is not deactivated by the thermal denaturation characteristic for enzymes and other proteins. The three-dimensional stmcture of an enzyme molecule, which is vital for the activity of the molecule, is governed by many forces and interactions such as hydrogen bonding, hydrophobic interactions, and van der Waals forces. At low temperatures the molecule is constrained by these forces as the temperature increases, the thermal motion of the various regions of the enzyme increases until finally the molecule is no longer able to maintain its stmcture or its activity. Most enzymes have temperature optima between 40 and 60°C. However, thermostable enzymes exist with optima near 100°C. 

Prepare the solutions and measure the pH at one temperature of the kinetic study. Of course, the pH meter and electrodes must be properly calibrated against standard buffers, all solutions being thermostated at the single temperature of measurement. Carry out the rate constant determinations at three or more tempertures do not measure the pH or change the solution composition at the additional temperatures. Determine from an Arrhenius plot of log against l/T. Then calculate Eqh using Eq. (6-37) or (6-39) and the appropriate values of AH and AH as discussed above. 

The filtrate was allowed to stand overnight and the fat skimmed off the top. After cooling to 100°F, the filtrate was transferred to a tank with thermostated water and the temperature set at 95° to 100°F. 24 gallons of pancreatic extract, prepared as described above, was added in 4-gallon increments every 12 hours for 3 days. The batch was brought to a boil and cooled to room temperature. 

Heat stability The Oplophorus luminescence system is more thermostable than several other known bioluminescence systems the most stable system presently known is that of Periphylla (Section 4.5). The luminescence of the Oplophorus system is optimum at about 40°C in reference to light intensity (Fig. 3.3.3 Shimomura et al., 1978). The quantum yield of coelenterazine is nearly constant from 0°C to 20°C, decreasing slightly while the temperature is increased up to 50°C (Fig. 3.3.3) at temperatures above 50°C, the inactivation of luciferase becomes too rapid to obtain reliable data of quantum yield. In contrast, in the bioluminescence systems of Cypridina, Latia, Chaetopterus, luminous bacteria and aequorin, the relative quantum yields decrease steeply when the temperature is raised, and become almost zero at a temperature near 40-50°C (Shimomura et al., 1978). 

The long term tests in the SASOL plant as well as in the Schwechat plant were run with outlet temperatures of 450°C, but both plants were also operated with higher loads that caused reactor outlet temperatures of 470°C or even higher. In comparison with the test run at 450°C, only a slight increase in deactivation rate was detectable which demonstrates the thermostability of the catalyst. From the aspect of thermostability, outlet temperatures of 450°-470°C are acceptable. Further considerations including the possibility of overload operation, the SNG specification to be achieved in final methanation, end-of-run conditions, and cost of reactor material will affect the selection of optimum outlet temperature. 

Since a first-order rate constant does not depend on [A]o, one need not know either the initial concentration or the exact instant at which the reaction began. This characteristic should not be used to rationalize experimentation on impure materials. These features do allow, however, a procedure in which measurements of slower reactions are not taken until the sample has reached temperature equilibrium with the thermostating bath. The first sample is simply designated as t = 0. Likewise, for rapidly decaying reaction transients, knowing the true zero time is immaterial. 

The electrophilic carbene carbon atom of Fischer carbene complexes is usually stabilised through 7i-donation of an alkoxy or amino substituent. This type of electronic stabilisation renders carbene complexes thermostable nevertheless, they have to be stored and handled under inert gas in order to avoid oxidative decomposition. In a typical benzannulation protocol, the carbene complex is reacted with a 10% excess of the alkyne at a temperature between 45 and 60 °C in an ethereal solvent. On the other hand, the non-stabilised and highly electrophilic diphenylcarbene pentacarbonylchromium complex needs to be stored and handled at temperatures below -20 °C, which allows one to carry out benzannulation reactions at room temperature [34]. Recently, the first syntheses of tricyclic carbene complexes derived from diazo precursors have been performed and applied to benzannulation [35a,b]. The reaction of the non-planar dibenzocycloheptenylidene complex 28 with 1-hexyne afforded the Cr(CO)3-coordinated tetracyclic benzannulation product 29 in a completely regio- and diastereoselective way [35c] (Scheme 18). 

Kinetic measurements were performed on a Hitachi 150-20 UV/VIS spectrophotometer. Dehydrobrominations were studied in DMF solution using cyclohexyl amine (CHA) as the base. Applied CHA concentrations were 2, 2.5, 3, 3.5, 4 and 5 10 3 mole.dm-3, initial concentration of 1 was 5 10 5 mole.dm-3 in every case (pseudo-first-order conditions). Ionic strength was adjusted to lO l mole.dm 3 with potassium nitrate. Kinetic curves / D(t) / were recorded at fix wavelength, X = 290 ran and the temperature was maintained at 30, 35.5, 40°C. Stock solutions were made daily for la and freshly for every measurement of Ih. The reaction was started by injection of solution of 1 to the thermostated solution of CHA. 

In this conception (149), any value of T denotes the exact temperature at which it was intended to carry out kinetic measurements experimental errors in thermostating appear in errors of log k. The approach is fully correct from the statistical point of view (203) and much simpler than to consider errors in T, too. 

Saguy, L, Thermostability of red beet pigments (betanine and vnlgaxanthine-I) infln-ence of pH and temperature, J. Food ScL, 44, 1554, 1979. 

It is known that NHase used in industry has a lower optimum temperature," therefore many reports have been concerned with screening for thermostable NHase. Miyanaga et al. has succeeded to analyze the X-ray structure of such a thermostable NHase from Pseudomonas thermophila. Bacillus sp. BR449 producing NHase with optimum temperature of 55°C has been isolated. Similarly, Bacillus sp. RAPc8 has a growth optimum at 65°C. Takashima et al. has isolated Bacillus smithii strain SC-J05-1, with optimum temperature at 40°C, and whose NHase has an optimum temperature and pH of 50°C and 10, respectively. Its crystal structure has also been elucidated. Bacillus pallidus strain Dac521 has... 

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