Final answer:
The fractions containing the most rubisco protein and phosphoproteins are the ones obtained with 20% and 40% ammonium sulfate precipitations.
Step-by-step explanation:
The fractions that are expected to contain the most rubisco protein are the ones produced with 20% and 40% ammonium sulfate (AS) precipitations. The large subunit of rubisco, which is one of the most abundant proteins, is predominantly located in these fractions. Additionally, these fractions also contain the most phosphoproteins, which can be observed through phospho-specific staining. Therefore, the 20% and 40% AS fractions are excellent sources for both rubisco protein and phosphoprotein enrichment.