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CHE 214

Tutorial 2

Problem 1

A MS/MS spectrum of an unmodified peptide with the precursor mass 636.30 2+ shows the following y-ions: 106.0, 219.1, 356.2, 457.2, 558.2, 661.3, 774.4, 889.4, 1018.4, 1174.5.

What is the [M+H]+ precursor mass?

Please identify all possible peptide sequences.

Problem 2

a) Identify the anomeric carbon of each of the sugars shown below, and specify whether the structure shown is a hemiacetal or hemiketal.

b) Draw mechanisms for cyclization of the open-chain forms to the cyclic forms shown.

Problem 3

Draw Fischer projection of the following sugars in their open-chain forms

Problem 4

a) The metabolic intermediate shown below undergoes an intramolecular imine formation as a step in the biosynthesis of lysine. Draw the product of this intramolecular imine formation step.

b) Predict the product of this iminium hydrolysis step from the proline degradation pathway.