2/8/12 HOW TO: Calculate Km and Vmax with Excel1/3 src.sfasu.edu/avk/BTC560/HOW TO.htm HOW TO: Calculate Km and Vmax with Excel Summary This step by step article explains how to calculate Km and Vmax using Microsoft Excel. Solver add-in is available as a part of optional component in Excel. With Solver, you can find an optimal value for a formula in one cell — called the target cell — on a worksheet. Solver works with a group of cells that are related, either directly or indirectly, to the formula in the target cell. Solver adjusts the values in the changing cells you specify — called the adjustable cells — to produce the result you specify from the target cell formula. Your target formula of course will be the Michaelis-Menten formula. You will use it to calculate the “calculated rates”. You will need the values of Km and Vmax which will be your adjustable cells and since we dont know the values we will use random numbers. The target cell will be the sum of the square differences between experimental and calculated rates. When the target cell will be minimized it will minimize the difference between the experimental and the calculate rate and adjust the values of Km and Vmax thus fitting the calculated rates curve to your experimental data. Requirement Excel 2000 or 20002 Solver – to add the Solver to your Tools click on the Tools menu select Add-ins and then selecting Solver from the Add-ins window. The Solver becomes available in the Tools menu. Substrate concentration Experimental Rates or Velocities calculated for every substrate concentration used Calculating velocity with preset Km and Vmax Select cell A1 and type Km= and press enter. Type Vmax= and then select cell B1. The B1 will contain the value for Km as mentioned above we will use a random number so type 1 and press enter. Type 1 again and this will be your Vmax. If you fill your data similar to the next picture then you can follow the step by step instructions. To calculate the Calculated velocity select the C5 and type “=” then select the value of Vmax (cell B2), type *, select the corresponding substrate (cell A5), type /, open parenthesis, select the value of Km (B1), add the substrate concentration and close the parenthesis. To keep the position of the Km and Vmax values constant add the $ sign before the column and the row number so instead of B2 you will have $B$2. Hit enter. Select the calculated cell and move the mouse pointer to the right bottom corner, when the pointer turns into a cross push the mouse left button and pull it down to calculate the rates for the rest of the substrate concentrations. 2/8/12 HOW TO: Calculate Km and Vmax with Excel 2/3 src.sfasu.edu/avk/BTC560/HOW TO.htm Plotting eperimental and calculated data on one plot T iaie he daa i bh eie e Seec he dae c A C ad cedig deedig h a bae cceai hae ad hi he b ba ,eec cha e caeed ad cic e. F he e f he cha iad e fiih he if ih eae he eie a d . Oce he i ead dbe cic he daa eie ha ced cacaed eci (he cic he daa eie he cedig c ad ae highighed) ad chage he ae fa e ad ie fa c. Y hd iia he be. Calculating difference Cacae he diffeece beee he eaed ad eeiea eciie. Y ca e he ece fa POWER cacae he ae f he diffeece. Y cee i iia he fig ice. 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