Practice question

Post-translational modifications exhibit characteristic mass increments in mass spectrometry analysis. Formylation introduces a formyl group –CHO to lysine or N-terminus through formyl phosphate donor or chemical artifact, adding CO moiety essentially 27.995 Da rounded to +28 Da to peptide mass. This shift must be distinguished from dimethylation or ethylation. Sulfonation adds 80 Da, methylation adds 14 Da, phosphorylation adds 80 Da. Detection of +28 Da suggests formylation event often observed as artifact in formaldehyde crosslinking or as biologically relevant histone modification influencing protein function assessed in high-resolution accurate-mass protein studies carefully evaluated today.