a) From the chemical structure above, write the amino acid sequence using both three-letter and one-letter abbreviations. Disregard chirality for this question. b) Indicate adjacent to the alpha-carbon of each residue whether it has an L- or D-configuration.

с" CH2 CH2 "НaN H с. CH С" CH Нзс CHз ZI о-о

Consider a short peptide with the sequence M-C-Q-L-Y-P-E-D-K. List the ionizable groups in this peptide, and the net charge of the whole peptide at pH a) 1.5, b) 7.0, and c)12.0.

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!

Proline is one of the amino acids in the "special" groups of sidechains. One reason for this is the dramatic impact it can have on secondary structure.  a) draw the lewis structure for a tripeptide with the sequence Ala-Pro-Ala b) Proline residues are rarely found in alpha helices - in fact, they are often referred to as helix-disrupting amino acids. Thinking about intermolecular interactions, provide an explanation for why proline might disrupt alpha-helices. c) Proline also has a similar effect on beta-sheets, and is rarely found in the middle of beta sheets. Thinking about noncovalent interactions, provide an explanation for why proline might disrupt beta-sheets.

Consider an amino acid (A) with no ionizable side chains, and call the three species involved in the acid/base equilibria H2A+, HA, and A- (see scheme below). Assume that pKa(1) = 2.0 and that pKa(2) = 9.0. Suppose that the total concentration of the amino acid is 1.0 mM. Report to two significant digits.  pH [H2A+] (mM) [HA] (mM) [A-] (mM) 1.0       2.0       3.0       4.0       5.0       6.0       7.0       8.0       9.0       10.0       11.0       12.0

can u help me