What is essential for phosphoprotein antibodies in resolving specific changes?

The ability to resolve a single change at the appropriate site is crucial for phosphoprotein antibodies because these antibodies are designed to detect specific phosphorylation events on proteins, which can signal various biological processes like cell signaling, differentiation, and response to external stimuli. Phosphorylation typically occurs at specific residues, such as serine, threonine, or tyrosine. Thus, for effective resolution of these changes, the antibody must recognize a specific target with precise site specificity. This ensures that the detected signal directly correlates with the biological effect that the phosphorylation event mediates.

When phosphoprotein antibodies can accurately identify these site-specific modifications, they provide valuable insights into the dynamics of cellular signaling pathways. Accurate detection allows researchers to study the temporal and spatial aspects of phosphorylation, leading to a better understanding of cellular functions and diseases.

This focus on site-specificity is why the other choices do not align with the core requirement of phosphoprotein antibodies. Their ability to recognize phosphorylated targets only, the ability to bind non-phosphorylated targets, or function in low pH conditions, while important in certain contexts, do not directly serve the main purpose of detecting precise phosphorylation changes relevant to biological processes.