Organic Chemistry MCAT Practice Exam

Disable ads (and more) with a membership for a one time $2.99 payment

Master Organic Chemistry for the MCAT. Use flashcards and multiple choice questions to understand concepts, with each question offering hints and detailed explanations. Prepare effectively for your exam!

Each practice test/flash card set has 50 randomly selected questions from a bank of over 500. You'll get a new set of questions each time!

Practice this question and more.

In metal ion affinity chromatography, what is the role of the Ni2+ ions?

To act as a buffer for the mobile phase.
To elute proteins by changing the pH.
To capture proteins tagged with a histidine sequence.
To separate based on boiling point.

The correct answer is: To capture proteins tagged with a histidine sequence.

In metal ion affinity chromatography, Ni2+ ions play a crucial role by specifically binding to proteins that have been engineered to possess a histidine tag. This technique exploits the strong interaction between the divalent nickel ions and the imidazole side chains of histidine residues in the proteins. When proteins containing these histidine sequences are introduced into the chromatographic column that has been pre-treated with Ni2+, they bind effectively due to this interaction. The presence of the Ni2+ ions allows for the selective purification of histidine-tagged proteins from a mixture, as these proteins will adhere to the column while non-tagged proteins are washed away. Later, to elute the bound histidine-tagged proteins from the column, a solution containing a high concentration of imidazole can be used, which competes with the histidine for the binding sites on the Ni2+. This strategy makes use of the specific affinity of the Ni2+ for histidine, thereby achieving a targeted purification process that is highly efficient and specific for histidine-tagged proteins.