the scatchard plot.pptx

The sectchard plot to measurement equilibrium of constant scatchard plot

1. Core Paper   - Analytical Chemistry (PCH 1804) Unit 3 : Application of spectrophotometry Topic : measurement equilibrium of constant   The Scatchard plot Presented by – Ramoliya Avinash Class – M.Sc. Sem 1 Roll No – 23-PCH-022

2. The Scatchard Plot The Scatchard equation (used to plot the Scatchard plot) is an equation used in molecular biology for calculating the equilibrium constant of a ligand with a protein or antigen with an antibody. Consider a species P which reacts with a species X to from a complex PX                                          P + X           PX

3. If we ignore the activity co-efficient , the equilibrium constant for the above reaction, can be given as,                                                                            ……[1] The Scatchard Plot

4. Consider a series of solutions in which increments of X are added to a constant amount of P . Letting P  be the total concentration of P (in the form p and PX), we can write                                          P   = [P] + [PX] The Scatchard Plot

5.                                   [P]   = P   [PX]              …..[2] Combination of equation (1) and (2) would       ……...[3] KP K [PX] …..[4] The Scatchard Plot _

6. The graph of [PX]/[X] versus [PX] has a slope of – K and is known as the Scatchard plot. [PX]/[X] slope = -K [PX] The Scatchard Plot

7. widely used in biochemistry to measure equilibrium constants Scatchard plot for binding of antigen (X) to antibody (P). The antibody binds the explosive trinitrotoluene ( TNT). From the slope , the binding constant for the reaction is P + X = PX The Scatchard Plot

8. For the graph, [PX] can be measured by measuring absorbance, if we known [PX] we can find [X] with the mass Balance: Suppose that P and PX each have some absorbance at wavelength but X has no absorbance at this wavelength. For simplicity, let all measurements be made in a cell of path length 1.00 cm so that we can omit when writing Beer’s law. The Scatchard Plot

9. The absorbance at some wavelength is the sum of absorbance of PX and P: A = A PX + A P Substituting value of [P] we can write, Here, A is the initial absorbance before any X is added.

10. …..[5] Substituting [PX] from Equation [5] into Equation [4] gives Scatchard Equation

11. The Scatchard Plot