LLecture 2

Question 1

what is isothermal microcalorimetry and how does it work ?

Answer 1

real-time monitoring and dynamic analysis of chemical, physical and biological processes.
Measures net rate of heat flow over time (system T stays stable)

Question 2

applications of isothermal calorimetry

Answer 2

Metabolism, binding affinity, protein stability, polymer curing, explosive science, cement industry

Question 3

What is representative of the quality of a calorimeter ?

Answer 3

it is the T stability over time (more than the microWatt range)

Question 4

one advantage of chip calorimeters, and one disadvantage

Answer 4

• very fast real time measurements
• low volume = low sensitivity

Question 5

what are the assumptions when we use heatflow as a proxy ? and heat ?

Answer 5

1) only valid in early exponential growth, and heat production rate per cell remains constant and all cells are metabolically active

2) amount of heat generatd should be constant, all cell produced remain in the medium and can be accounted for

Question 6

4 things to test with abiotic reactions

Answer 6

• shelf life
• interactions (between two ingredients f.ex)
• cement curing
• decay (radioactive markers)

Question 7

what is isothermal titration ? what is it mostly used for ?

Answer 7

determine thermodynamic parameters of interactions in solution. Study the binding of small molecules to larger macromolecules (metal to enzyme, drug to protein, …)

Question 8

how does DSC work ? is it possible to go below zero?

Answer 8

measures the difference in the amount of heat required to increase the T of a sample and an inert reference as a function of T

We can also go below zero degrees

Question 9

what are the uses of DSC ?

Answer 9

• protein stability and denaturation (unfolding)
• polymers : melting, glass transition, crystallization, …
• purity
• free vs bound water

Question 10

what is thermogravimetric analysis ? (TGA)

Answer 10

measure the mass of a sample as the T changes -> info on phase transition, absorption, adsorption, desorption, …

Question 11

what kind of instrument is used for TGA ?

Answer 11

a thermobalance, sample attached to platinum wire

Question 12

what is EGA ?

Answer 12

evolved gas analysis -> uses gas from a heated sample that undergoes decomposition or desorption -> this gas is analized (MS, IR, GC, …)