How many tetrapeptides can be produced that contain one residue each of serine, methionine, arginine, and tyrosine? In an aqueous environment will the following peptide fragment more likely be buried...

How many tetrapeptides can be produced that contain one residue each of serine, methionine, arginine, and tyrosine? In an aqueous environment will the following peptide fragment more likely be buried inside a globular protein or located on its surface? Explain.