Practice question

Sulfur constitutes cysteine and methionine residues, essential for disulfide bonds and enzyme active sites, making sulfur tracking ideal for protein synthesis studies. Sulfur-35 is chemically identical to natural sulfur, emits moderate beta particles easily detected without excessive radiation damage, and half-life of 87 days allows pulse-chase labeling. Phosphorus-32 labels nucleic acids preferentially, tritium and carbon-14 label broadly all macromolecules lacking specificity for sulfhydryl amino acids. Incorporation of labeled methionine containing sulfur-35 into nascent polypeptides directly monitors translation rates and protein turnover.