How would a protein found in the nonpolar interior of a membrane fold?

A polypeptide composed of 13 unique amino acids undergoes partial hydrolysis to yield the following peptides:

(i) Arg, Gln, Thr   (ii) Leu, Arg            (iii) Phe, Cys, Gln       (iv) Thr, Arg

(v) Glu, Lys, Pro  (vi) Met, Ala, Pro     (vii) Leu, Tyr, Arg        (viii) Gln, Lys, Cys

(ix) Pro, Met        (x) Lys, Glu, Gln       (xi) Gln, Phe                (xii) Val, Ala

If the reaction of the intact polypeptide with carboxypeptidase A releases Leu, what is the sequence of the polypeptide? 

Give the structure of the tetrapeptide Ser-Cys-Met-Asp and highlight the peptide bonds in red to indicate them.

Draw the three-dimensional structure of L-glutamic acid.

Enzymes are chiral and react at different rates with a pair of enantiomers. Hydrolysis of esters can be catalyzed using the enzyme esterase. This enzyme hydrolyzes esters of L-amino acids much more rapidly than the esters of D-amino acids. Describe how you can separate L-alanine and D-alanine using this enzyme.

Draw the three-dimensional structure of L-lysine.

Provide the three-dimensional representation of D-aspartic acid.

Determine whether valine (pI = 6.02) or cysteine (pI = 5.15) has a more negative charge at pH 7.0.

Show how electrophoresis can separate glutamic acid (PI 3.2), lysine (PI 9.7), and glycine (PI 6.0) from a solution having pH 6.

How much of the α-amino group of serine is protonated at its isoelectric point (pI)?

Draw the predominant form of serine present in a solution of pH = 12.0. 

Show the location and the type of charge on the tripeptide Gly-Ala-Ser at pH 11.0.

Draw the predominant forms of phenylalanine, tryptophan, and tyrosine present as a mixture at pH 7.