Final answer:
Q-Sepharose is an anion exchange resin composed of cross-linked agarose beads with positively charged functional groups that bind negatively charged molecules in a process known as ion exchange chromatography. This allows for the separation and purification of proteins based on their charge.
Explanation:
The chemical nature of Q-Sepharose which allows it to function as an ion exchanger is rooted in its composition. Q-Sepharose is a form of cross-linked agarose beads which have been chemically modified to carry positively charged functional groups, typically quaternary ammonium groups.
This anion exchange resin can capture and bind negatively charged molecules, such as certain proteins, through electrostatic interactions. When a mixture containing various ionic species is passed through a column containing Q-Sepharose, negatively charged species will bind to the positively charged groups on the Q-Sepharose, while other species will pass through.
During ion exchange chromatography, to elute (wash off) the bound molecules, the ionic strength of the elution buffer is typically increased. This is done by adding salts, which provide counter-ions that compete with the protein for binding to the resin, resulting in the release of the protein into the buffer. Hence, proteins bound through ion-ion interactions can be selectively detached and collected. The physical nature of Q-Sepharose—its high density of charged groups, chemical stability, and structural robustness—makes it suitable for repeated use in chromatography processes.