Heat Capacity of Catalysis Flashcards
(19 cards)
Why is it important to correctly assess the optimum operating conditions for an enzyme?
o Reactions efficient and reliable
o Maximum yields can be achieved
True or false:
Enzymes engineered to be more thermostable are guaranteed to have higher theromoactivity
False
What is the main principle of transition state theory?
Formation of the transition state is reversible, but decay into product is not
What is k‡
The absolute rate constant,
The rate of passage over the potential energy barrier separating the reactants and products.
What kind of graph does the Arrhenius Equation predict?
Linear
Reasons for curvature (6)
- Denaturation
- Change in chemical step
- Quantum mechanical phenomena
- Pre-equilibrium required for formation of the active complex
- Multiple (non) reactive conformation
- difference in vibrational modes
Why might quantum mechanical phenomena lead to curvature of the graph?
Because there is a difference between the vibrations of the products and substrates
What are N-state models?
Different conformations that are differently active existing in equilibrium
That equilibrium may shift with temperatures and cause the average activity to change
True or false:
Each conformation (n-state) has a linear Eyring graph
True
What is Cp?
The amount of heat required to raise the temperature of a system by 1 degree
Cp = kJ mol-1 K-1
What is ∆CP‡ ?
The difference in the distribution or frequency of vibrational modes between the ground and transition state.
Different folded states will have very similar energies, so differences tend to come from _
Vibrational nodes
Transition states are stabilised by additional bonds and are more rigid, this will cause different vibrational energies, which would have an impact on _
Heat capacity
Assumptions of macromolecular rate theory
- Considers curvature prior to the effect of denaturation.
- Assumes the hydration state of the reactant and transition state are the same.
- Assumes one major conformational state of the reactant and transition state complex.
What does the value of ∆CP‡ mean for the graph?
If ∆CP‡ is large, then the graph of the Eyring equation is curved. If ∆CP‡=0 then it would be a straight line.
True or false:
∆CP‡ is pressure dependent
True
Is ∆CP‡ isotopically sensitive?
Yes.
Found increased mass decreased curvature
Pudney’s single molecule research
Whispering gallery and bound a protein to a gold nanorod and used absorption-based techniques to track very subtle changes.
Pudney found that in his experiment there were two conformers, but those also had curved graphs, so both theories were true.
MD simulations
Study measured distribution of vibrational modes from ground state substrate to a transition state substrate.
He used these values to calculate the heat capacity of catalysis, and it was correct.
He could track the contribution of areas of the proteins to catalysis.
