how does the protein environment surrounding an amino acid chain affect its chemical properties?Consider the carboxyl group on an asparate side chain in the following environments in a protein. Rank in order these environments from the highest to the lowest proportion of carboxyl groups in the -COO- form.that is in terms of pKas. 1. an aspartate side chain on the surface of protein with no other ionizable groups nearby. 2. an aspartate side chain buried in a hydrophobic pocket on the surface of a protein 3. an asparate chain in a hydrophobic pocket adjacent to a glutamte side chain 4. an asparate side chain in a hydrophobic porket adjacent to a lysine side chain

Amino acid structure For any ionizable group, indicate the pka value and draw the structure that would be expected at the pH inside the cell (~7.4).

Which of the following amino acids are more likely to be on the interior of the protein? And which are more likely to be exposed to the surface? L I D E W A V K H M Q Y

A tetrameric protein dissociates into dimers when the detergent sodium dodecyl sulfate (SDS) is added to a solution of the protein. But the dimers are termed SDS-resistant because they do not further dissociate into monomers in the presence of the detergent. What intermolecular forces might be acting at the dimer-dimer interface? Are the intermolecular forces acting at the monomer-monomer interface different? Explain.

Among these amino acid combinations listed above, only the combination of Lys and Glu have side chains with groups that have the greatest ability to stabilize the tertiary structure of a protein.   Explain by drawing (a) why Lys and Glu side chain interaction stabilizes the tertiary structure of a protein (b) why the pairs of Glu and Asp & Arg and Pro cannot provide the stability to the protein structure.

Glutamine is an amino acid that has -CH₂-CH2-CO-NH₂ as its R group. The R group of the amino acid isoleucine is -CH2-CH-(CH3)2. If these amino acids were in a globular protein in aqueous solution, where would they most likely be? O Both glutamine and isoleucine would be in the interior and on the exterior of the globular protein. O Glutamine would be in the interior, and isoleucine would be on the exterior of the globular protein. O There isn't enough information O Both glutamine and isoleucine would be on the exterior of the globular protein. O Isoleucine would be in the interior, and glutamine would be on the exterior of the globular protein.

Consider the phenolic hydroxyl group of a particular Tyr residue in a protein. Suppose the hydroxyl group in the unfolded protein in aqueous solution, where the group is exposed to H2O, has a pKa of 10.0. If that group is found in a hydrophobic environment in the interior of the protein when the protein is folded into its native tertiary structure, would you expect the pKa of the phenolic hydroxyl to be higher or lower in the folded protein interior than in H2O? Explain your reasoning.

Consider protein folding that results when the following components interact:   Where the solution is at a pH of 7, green (thick-dotted line) represents aspartic acid (R group contains a carboxylic acid with pKa = 4), orange (thick-solid line) represents lysine (R group contains an amine with pKa = 10), and blue (thin-solid line) represents hydrophilic groups. Rank the three complexes in order from lowest to highest dissociation constants Kd (low Kd values correspond to good binding constants and low energy, while high Kd values correspond to low binding constants and high energy) as determined by intermolecular charge-charge interactions. For those complexes with charge-charge interactions being equal, look at the possibility for the formation of hydrogen bonds via carboxylic acid dimers (only possible when the carboxylic acid is protonated) which are low energy structures.

There is parts A-D for the picture provided. A) A peptide has the sequence, Arg-Cys-His-Tyr-Glu-Asn-Lys-Asp. What is the net charge at pH 1? Choices: -5 -4 -3 -2 -1 0 +1 +2 +3 +4 +5   B) A peptide has the sequence Arg-Cys-His-Tyr-Glu-Asn-Lys-Asp. What is the net charge at pH 5?   Choices: -5 -4 -3 -2 -1 0 +1 +2 +3 +4 +5   C) Same Peptide sequence, What is the net charge at pH8.5, (N-terminus is pronated) Choices:    -5 -4 -3 -2 -1 0 +1 +2 +3 +4 +5   D) A  peptide has the sequence, Arg-Cys-His-Tyr-Glu-Asn-Lys-Asp. What is the net charge at pH 13?   Choices: -5 -4 -3 -2 -1 0 +1 +2 +3 +4 +5   Thank You!

Suppose you have a solution of a protein, which contains a specific Tyr residue that has an actual (measured) pKa of 8.8. The protein binds a ligand by several noncovalent interactions, one of which is a hydrogen bond in which the Tyr phenolic hydroxyl group must serve as a hydrogen bond donor. Calculate the percentage of the protein molecules in which that tyrosyl residue's phenolic hydroxyl group could serve as a hydrogen bond donor at pH 8.5