Homework1 - reaction you reach half‐life (8.95 Activity)...

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Determine remaining inactive enzyme concentration at each time point using the formula: [E] inactive = [E] o {1 – (Activity/17.9)} For the Zero‐order plot, use the equation: [E] inactive = [E] o - kt For the 1 st order plot, use the equation: ln[E] inactive = ln[E] o - kt 5 10 15 20 25 30 35 -5 0 5 10 15 20 Zero Order Fit Inactive [E], 10 nM Inactive [E], 30 nM y = 9.3315 - 0.23821x R= 0.97971 y = 25.481 - 1.1434x R= 0.95369 Inactive [E] Time (min) 1.5 2 2.5 3 3.5 -5 0 5 10 15 20 First Order Fit ln[E], 10 nM ln[E], 30 nM y = 2.2467 - 0.031471x R= 0.9917 y = 3.2825 - 0.067032x R= 0.98917 ln[E] Time (min)
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For the 2 nd order plot, use the equation: (1/[E] inactive ) = kt + (1/[E] o ) From the plots and the linear curve fits, it should be apparent that the data best fits a second order process. You can confirm this by noting that the value of k (slope) remains the same for both initial concentrations (k = 0.0042 nM ‐1 min ‐1 ). You might also note that for the 30 nM
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Unformatted text preview: reaction you reach half‐life (8.95 Activity) between 7 and 8 minutes. However, for the 10 nM reaction, you do not reach this point until after 15 minutes (the half life is actually 23.8 minutes). This relationship between starting concentrations and half‐lives, increasing initial [E] decreases the half‐life, also fits with a 2 nd order process. One possible explanation for the observed inactivation and reactivation is that this protein is only active in its dimeric form. The enzyme is inactivated at 60 ° C due to the dimers dissociating into inactive monomers. As two monomers bind to form a dimer at 5 ° C, they regain their activity: 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18-5 5 10 15 20 Second Order Fit 1/[E], 10 nM 1/[E], 30 nM y = 0.10361 + 0.0042163x R= 0.99728 y = 0.033465 + 0.0041852x R= 0.99903 1/[E] Time (min)...
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This note was uploaded on 03/16/2012 for the course MCB MCB 123 taught by Professor Christopherfraser during the Spring '11 term at UC Davis.

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Homework1 - reaction you reach half‐life (8.95 Activity)...

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