The isoelectric point of most proteins generally falls within which range?

The isoelectric point (pI) of a protein is the pH at which the protein carries no net electric charge. Most proteins have functional groups that can accept or donate protons depending on the pH, which leads to a balance of positive and negative charges.

The range of 4.0 to 7.5 encompasses the pI for the majority of naturally occurring proteins, as this range accommodates the diverse chemical structures and amino acid compositions of proteins. It captures proteins that are more acidic or more basic based on their respective amino acid content, with many proteins having pI values skewed toward neutral pH.

Understanding the pI is important for techniques like isoelectric focusing, where proteins are separated based on their charge at a specific pH. Proteins with pI values within this range are generally soluble, while those outside this range may precipitate at their respective pI, impacting analytical and purification techniques.

The other provided ranges either fall outside the typical pI values seen in many proteins or are too broad, limiting the specificity needed for accurate characterization in biochemical studies.