Path B - Module 24: Peptide Synthesis#

In protein engineering, we often need to add small peptide sequences to our enzymes, such as signal peptides for secretion or purification tags.

In this module, you will learn to use build_peptide() to synthesize a 6xHis-Tag (a sequence of 6 Histidines) that is commonly used to purify enzymes like PETase in the lab.

import molsysmt as msm
from molsysmt import systems

1. Synthesizing the Purification Tag#

The function build_peptide() can transform the sequence “HHHHHH” into a 3D structure ready to be attached to your enzyme.

# Build the 6xHis-Tag
his_tag = msm.build.build_peptide('HHHHHH')

print(f"His-Tag synthesized. Form: {msm.get_form(his_tag)}")
msm.info(his_tag)

2. Adding Cappings to the Tag#

To make the tag more stable and avoid unwanted charges at the ends, we can add terminal protections.

# Build a capped version of the tag
capped_tag = msm.build.build_peptide('HHHHHH', n_terminal='ACE', c_terminal='NME')

msm.info(capped_tag, element='group')

3. Visualizing the New Component#

Let’s see how the tag looks before we “glue” it to our PETase enzyme.

msm.view(capped_tag)

🏆 Path B Challenge: The Tag Designer#

  1. Synthesize a Strep-tag II, another popular purification sequence: WSHPQFEK.

  2. Add an Acetyl (ACE) group to the N-terminal.

  3. Use msm.get() to find the total Mass of this Strep-tag.

  4. Check if the Strep-tag is recognized as a single Molecule using msm.info().

You now know how to create new protein fragments! In Module 25, we will learn how to put our enzyme and our tags into a Solvated Box with specific ion concentrations.