Differential scanning calorimetry (DSC) is a technique used in the biopharmaceutical industry to characterize the thermodynamic properties of large biomolecules.  DSC (Figure 1) utilizes an aluminum sample pan filled with a solvent and biomolecule of interest and an identical reference pan filled only with the solvent.  Each pan is heated separately at a constant rate while maintaining a temperature difference of zero between the sample and reference.Figure 1  Differential scanning calorimeterAs the temperature of both the sample and reference medium increases, the biomolecule in the sample solution experiences a chemical or physical change, causing a temperature difference relative to the reference medium.  To compensate for this temperature difference, the heat flow (heat (q) supplied per unit time (t)) from the instrument heater to the sample pan is increased (or decreased) to return the temperature difference to zero.  The difference between the heat qs needed to raise (or lower) the sample to a specific temperature and the heat qr needed to raise the reference medium to the same temperature is the excess heat, qex𝑞ex.qex=qs−qr𝑞ex=𝑞s-𝑞rEquation 1The excess heat capacity Cp,ex of the sample across a temperature range ΔT can be derived from the excess heat flow, the heating rate, and the mass of the biomolecule sample by Equation 2.(qext)flow=mCp,ex(ΔTt)rate𝑞ex𝑡flow=𝑚𝐶p,exΔ𝑇𝑡rateEquation 2During a DSC experiment investigating the thermodynamics of the reversible and irreversible unfolding of a particular protein, a researcher prepared two buffered sample solutions that each contained 7.5 × 10−3 g of the protein and were purified to remove any nonvolatile solutes.The protein solutions were each analyzed by DSC and heated at a rate of 1.5 °C/minute, resulting in the thermal profiles (thermograms) in Figure 2.Figure 2  Thermograms of sample 1 (pH = 4.7) and sample 2 (pH = 9.4) after a heating cycle.The single peak in each thermogram represents the melting temperature (Tm) of the protein.  For reversible protein folding, ∆G° = 0 when the temperature reaches Tm.The unfolded protein strands were observed to refold at pH < 7, but at a pH > 7, the unfolded protein strands were observed to aggregate without refolding (Reaction 1).folded⇌Kequnfolded−→−−pH > 7aggregationfolded⇌𝐾equnfolded→pH > 7aggregationReaction 1 Question 28Which of the following expressions describes the equilibrium concentrations of folded and unfolded protein at Tm for sample 1?A.[folded][unfolded]>1foldedunfolded>1B.[folded][unfolded]=0foldedunfolded=0C.[unfolded][folded]=1unfolded[folded]=1D.[unfolded][folded]<1

Indirect calorimetry calculates heat that living organisms produce by measuring either their production of carbon dioxide and nitrogen waste (frequently ammonia in aquatic organisms, or urea in terrestrial ones), or from their consumption of oxygen. Lavoisier noted in 1780 that heat production can be predicted from oxygen consumption this way, using multiple regression. The dynamic energy budget theory explains why this procedure is correct. Heat generated by living organisms may also be measured by direct calorimetry, in which the entire organism is placed inside the calorimeter for the measurement.A widely used modern instrument is the differential scanning calorimeter, a device which allows thermal data to be obtained on small amounts of material. It involves heating the sample at a controlled rate and recording the heat flow either into or from the specimen.

An instrument used for measuring body temperatures isa.Microscopesb.Digital thermometerc.Computed Tomography scand.The diabetic blood test

What is calorimeter? What is the use of this instrument

When two samples of matter that are initially at different temperatures are placed in thermal contact, the samples undergo heat transfer until reaching thermal equilibrium at some new, final temperature.  Transferred heat (q) can be measured based on the initial and final temperatures (Tinitial and Tfinal) of a sample that is placed into a known volume of water inside the insulated chamber of a calorimeter.Figure 1  Analysis of a heated sample using a calorimeterAccording to the first law of thermodynamics, the transferred heat energy is conserved, and the heat lost from the sample (indicated by a negative sign) must be equal to the sum of the heat gained by the water and the calorimeter, as expressed by Equation 1.−qsample = qwater + qcalorimeterEquation 1In a perfectly efficient system, qcalorimeter = 0, and all the heat released from the sample is retained by the water.  In real systems, some heat is absorbed by the calorimeter itself.  Based on the amount of heat transferred from the sample and the change in temperature, the heat capacity (C) of the entire sample can be determined.  Expressing the heat capacity per unit mass yields the specific heat capacity (Cp) of the substance comprising the sample.Table 1  Measured specific heat capacities of several selected substancesSample Specific heatcapacity (J/g·°C)Lead 0.129Tungsten 0.132Silver 0.235Strontium 0.315Zinc 0.388Cobalt 0.421Titanium 0.525Wood 2.00Paraffin wax 2.5Water 4.184Experiment 1A sample of water (10.0 mL at 75 °C) was stirred into a calorimeter containing 100.0 mL of water initially at 21 °C.  At thermal equilibrium, the system was found to have a temperature of 25 °C.Experiment 2The water in the calorimeter from Experiment 1 was discarded and replaced with 100.0 mL of fresh water at 25 °C.  An unidentified 100.0 g sample of one of the metals from Table 1 was heated to an initial temperature of 80 °C and then placed into the water.  At thermal equilibrium, the system was found to have a temperature of 30 °C. Question 58Based on the results of the calorimetry experiments, a lab technician concludes that the specific heat capacity of the unidentified metal sample is 0.42 J/g·°C.  Is this conclusion correct?A.Yes; qwater ≈ qmetal in Experiment 2 because Experiment 1 shows that the heat lost from the water and absorbed by the calorimeter is negligible (qcalorimeter ≈ 0).B.Yes; qwater < qmetal in Experiment 2 because Experiment 1 shows that the sample absorbs a small amount of heat from the calorimeter (qcalorimeter < 0).C.No; qwater < qmetal in Experiment 2 because Experiment 1 shows that a significant amount of heat from a sample is lost from the water and absorbed by the calorimeter (qcalorimeter > 0).D.No; qwater > qmetal in Experiment 2 because Experiment 1 shows that the calorimeter adds a small amount of heat to the water (qcalorimeter < 0).

When two samples of matter that are initially at different temperatures are placed in thermal contact, the samples undergo heat transfer until reaching thermal equilibrium at some new, final temperature.  Transferred heat (q) can be measured based on the initial and final temperatures (Tinitial and Tfinal) of a sample that is placed into a known volume of water inside the insulated chamber of a calorimeter.Figure 1  Analysis of a heated sample using a calorimeterAccording to the first law of thermodynamics, the transferred heat energy is conserved, and the heat lost from the sample (indicated by a negative sign) must be equal to the sum of the heat gained by the water and the calorimeter, as expressed by Equation 1.−qsample = qwater + qcalorimeterEquation 1In a perfectly efficient system, qcalorimeter = 0, and all the heat released from the sample is retained by the water.  In real systems, some heat is absorbed by the calorimeter itself.  Based on the amount of heat transferred from the sample and the change in temperature, the heat capacity (C) of the entire sample can be determined.  Expressing the heat capacity per unit mass yields the specific heat capacity (Cp) of the substance comprising the sample.Table 1  Measured specific heat capacities of several selected substancesSample Specific heatcapacity (J/g·°C)Lead 0.129Tungsten 0.132Silver 0.235Strontium 0.315Zinc 0.388Cobalt 0.421Titanium 0.525Wood 2.00Paraffin wax 2.5Water 4.184Experiment 1A sample of water (10.0 mL at 75 °C) was stirred into a calorimeter containing 100.0 mL of water initially at 21 °C.  At thermal equilibrium, the system was found to have a temperature of 25 °C.Experiment 2The water in the calorimeter from Experiment 1 was discarded and replaced with 100.0 mL of fresh water at 25 °C.  An unidentified 100.0 g sample of one of the metals from Table 1 was heated to an initial temperature of 80 °C and then placed into the water.  At thermal equilibrium, the system was found to have a temperature of 30 °C. Question 59According to the results from Experiments 1 and 2, the unidentified metal sample is:A.Sr, because qcalorimeter > 0 and qmetal = qwater − qcalorimeterB.Co, because qcalorimeter ≈ 0 and qwater ≈ qmetalC.Ti, because qcalorimeter > 0 and qwater < qmetalD.unknown and its composition cannot be determined without more information.