What does the term "post-translational modification" refer to in biochemistry?

The term "post-translational modification" refers specifically to the changes made to proteins after they have been synthesized, which aligns perfectly with the selected answer. After proteins are created during the translation process, they often undergo several biochemical modifications that can affect their activity, localization, stability, and function. These modifications can include processes such as phosphorylation, glycosylation, methylation, acetylation, and ubiquitination, among others. Each of these alterations can play critical roles in modulating protein function and facilitating cellular processes.

The other choices provide definitions that do not accurately describe post-translational modification. The creation of new proteins from DNA is related to transcription and translation, while cutting proteins into smaller peptides (such as proteolysis) is a specific type of modification but does not encompass the full range of alterations proteins can undergo post-synthesis. Lastly, the interaction of proteins with nucleic acids refers to distinct molecular interactions that are also important in biochemistry but are not post-translational modifications themselves. Therefore, the selected answer is indeed correct in encapsulating the essence of post-translational modifications.