Proteins serve as the workhorse macromolecules that function in nearly every task of cellular life and are the key determinants of the maintenance, growth, and development of a living cell. They often undergo specific changes, including chemical modifications and cleavages, that determine their structure and function. Such changes occur mostly after translation, so they are referred to as posttranslational modifications (PTMs). The PTMs are generally dynamic and conditional and thus play crucial roles in readjusting physiological and metabolic activities. PTMs also serve as the key regulators of the survival and adaptation of living organisms under stressful conditions. Among the PTMs, chemical modifications generally occur on the R-groups of the specific amino acids under different developmental and stress conditions to confer stability and activity to the proteins. Various methods have been devised to identify and precisely quantify different PTMs. These methods include protein enrichment through fractionation and affinity-based techniques followed by identifications of PTMs using PTM-specific antibodies or through mass spectrometry, where the former is qualitative, whereas the latter is quantitative. Given their importance, there is ample thrust for investigating PTMs, especially their relevance in plant stress and memory. Since stress is accompanied by enhanced reactive oxygen species generation, oxidative modifications are prevalent but very less studied and, thus, warrant thorough investigations. Considering these factors, the present protocol presents a general overview for investigating PTMs, emphasizing oxidative PTMs specific to stress and memory.