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isothermal titration calorimetry. CHEM 471: Physical Chemistry. Differential scanning calorimeter. CHEM 471: Physical Chemistry. Computer adjusts heater currents to keep sample and reference at same temperature. Temperature ramped at constant rate. Plot dq/dt = I r 2 vs. t.
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isothermal titration calorimetry CHEM 471: Physical Chemistry
Differential scanning calorimeter CHEM 471: Physical Chemistry Computer adjusts heater currents to keep sample and reference at same temperature. Temperature ramped at constant rate. Plot dq/dt = I r2 vs. t
thermodynamics of protein folding Heat proteins, they denature: ΔdS° > 0 Cool proteins, they also denature: : ΔdS° < 0 ... uh oh! Entropy (and enthalpy) of denaturation change with temperature: need second order expansion of the free energy of denaturation ΔfG°= –ΔdG° etc. CHEM 471: Physical Chemistry
differential scanning calorigram Heating rate r = dT/dt dq/dt × 1/r = dq/dT = Cp Integral is ΔdH dq/dt Cp, denatured ΔdCp Cp, folded Td CHEM 471: Physical Chemistry t ∝ T ΔdH/Td = ΔdS ΔdG = ??? ΔdH60C = ΔdHTd + ΔdCp,Td (333 K – Td) ΔdG60C= ΔdGTd – ΔdSTd(333 K – Td) – (ΔdCp,Td/Td)(333 K – Td)2/2 + ...
thermodynamics of protein denaturation CHEM 471: Physical Chemistry T0 = 60° C = 333.15 K
thermodynamics of protein folding CHEM 471: Physical Chemistry
stability curves positive entropy of folding negative entropy of folding CHEM 471: Physical Chemistry All have about the same temperature of maximum stability, between 310° and 320°K Hot denaturation temperature more reliable than cold
