Exam+1+_+W12+_+v2_KEY

Exam+1+_+W12+_+v2_KEY - Exam 1 KEY MCB 120L Winter 2012 KEY...

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KEY 1 Exam 1 KEY MCB 120L Winter 2012 Friday 27 January 2012 Small peptides are quantified by labeling the N-terminus (& lysine side-chains) with Fluorescamine. Fluorescamine attaches to primary amines in aqueous solutions between pH 8.0 – 9.0 (a typical reaction is run at pH 8.35). (Fluorescamine: ε (234nm) = 28000 M -1 cm -1 ; 278.26 g/mol). 1a. From the four buffers available in the lab listed below, select one appropriate buffer to use in the Fluorescamine labeling reaction (2 points), clearly circle one choice : Tricine(base) pKa 8.16 Tris (base) pKa 8.21 TAPS(base) pKa 8.49 CAPS(base) pKa 10.4 179.17 g/mol 121.14 g/mol 243.28 g/mol 221.32 g/mol 1b. Briefly provide the two best reasons for the selection (4 points): i) Eliminate CAPS: its pKa is more than one-pH unit from the typical reaction pH 8.35 ii) Eliminate Tris: has a primary amine that will interfere with the reaction 1c. Calculate the theorectical quantities of ingredients for the preparation of 50 ml of a 50 mM concentration of the buffer selected in Question 1a above, pH 8.35. Available reagents are: dH
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This note was uploaded on 01/30/2012 for the course BIS 101/102 taught by Professor Etzler during the Spring '10 term at UC Davis.

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Exam+1+_+W12+_+v2_KEY - Exam 1 KEY MCB 120L Winter 2012 KEY...

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