Which of the following seperates proteins solely on the basis of it’s molecular size?
## **Core Concept**
Gel filtration chromatography, also known as size-exclusion chromatography, is a technique used to separate proteins based on their molecular size. This method relies on the differential elution of molecules through a column packed with porous beads, where smaller molecules are retained longer than larger ones.
## **Why the Correct Answer is Right**
The correct answer, Gel Filtration Chromatography, separates proteins solely on the basis of their molecular size. This technique works by passing a mixture of proteins through a column containing porous beads. Larger proteins, which cannot enter the pores, pass around the beads and elute first. Smaller proteins enter the pores and take a longer path through the column, eluting later. This size-based separation allows for the purification and estimation of molecular weights of proteins.
## **Why Each Wrong Option is Incorrect**
* **Option A: Ion Exchange Chromatography** - This method separates proteins based on their charge, not size. Proteins bind to the resin based on their ionic properties and are eluted by changing the ionic strength or pH of the buffer.
* **Option B: Affinity Chromatography** - This technique separates proteins based on their specific biochemical interactions, such as enzyme-substrate or antigen-antibody interactions, not size.
* **Option D: Electrophoresis** - While certain types of electrophoresis, like SDS-PAGE, can separate proteins based on size (in the presence of SDS, which denatures proteins and coats them with a negative charge proportional to their length), the question seems to focus on chromatography techniques. Electrophoresis is an electric field-based method, not chromatography.
## **Clinical Pearl / High-Yield Fact**
A key point to remember is that Gel Filtration Chromatography is often used for desalting and concentrating protein solutions in addition to sizing. It's a gentle method that doesn't require harsh chemicals, making it suitable for sensitive or large proteins.
## **Correct Answer:** C. Gel Filtration Chromatography.