Which of the following peptides would exhibit the greatest steric constraints?

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11ecba2d_0f09_fc6b_a3bf_092c8014f14a_MD0008_00 Steric effects occur within a molecule when electron clouds in close proximity interact and repel each other. Molecules (or substituent branches) that contain many atoms or atoms with large electron clouds are more prone to experiencing steric effects than molecules with few atoms or atoms that have small electron clouds. Molecular structures that are prone to steric effects (ie, large molecules) are constrained in the conformations they can adopt because many conformations result in repulsive interactions and are not stable. The twenty standard amino acids found in natural peptides and proteins vary greatly in the sizes of their side chains, and therefore they vary in the sizes of their electron clouds. The amino acids phenylalanine (F), isoleucine (I), leucine (L), lysine (K), methionine (M), arginine (R), tryptophan (W), and tyrosine (Y) all contain large side chains that make substantial contributions to steric constraints. Peptides that contain these amino acids experience greater steric effects than peptides of the same length that contain smaller amino acids. Each of the peptides in this question is made from six amino acids. However, the peptide FYLWIR consists entirely of amino acids with large side chains and will exhibit the greatest steric constraints of the choices given. (Choices A, B, and C) The peptides AGSCTN, ICGHLA, and PDNETQ all contain multiple amino acids with small side chains that will not exhibit as much steric hindrance as peptides containing amino acids with larger side chains. Educational objective: Steric effects occur when two electron clouds in close proximity repel each other. Amino acids with large side chains (F, I, L, K, M, R, W, and Y) contribute more to steric constraints within a peptide than other amino acids do.

Which of the Following Peptides Would Exhibit the Greatest Steric