Thermodynamics Flashcards
[PL]
Protein-ligand complex conc.
[L]
Ligand conc.
[P]
Protein conc.
Dissociation constant
Kd
Association constant
Ka
Kd units
molddm-3
Ka units
Mol-1dm3
Relationship between Kd and Ka
Kd=1/Ka
B
Fractional occupancy = [PL]/([P]+[PL])
Langmuir Isotherm (B as a function of [L])
B = [L]/(Kd+[L])
Linearized Langmuir Isotherm
ln(B/(1-B)) = ln[L] - lnKd
Gradient of a langmuir isotherm
1
Quick dertemination of Kd
On a graph of x = [L] and y = B
- Kd = [L]1/2
Hill Isotherm (B as a function of [L])
B = [L]^n/(Kd + [L]^n)
Linearized Hill isotherm
ln(B/(1-B)) = nln[L] - lnKd
Gradient of Hill Isotherm
n (number of ligands bound to each protien
Wp+l
no. conformations for P + L
Wpl
no. conformations for PL
Kd from Boltzmann distribution
Kd = Wp+l/Wpl e^(-Hd/RT)
Entropy of disdsociation
Sd = RlnWi
Entropy of P + L
Sp+l = RlnWp+l
Entropy of PL
Spl = RlnWpl
Equation linking G and K
G = RTlnK
Favourable chnages for G
K - Large
G - Negative
H - Negtive
S - positive
Equation for G
G = H - TS
Van’t Hoff plot
lnK = H/R 1/T + S/R
Describe a DSC output
- X = T
- Y = delta Cp
- Area under curve = deltaHm
- T at peak = Tm
DeltaSm
DeltaHm/Tm
DeltaGm
0
