Synthetic Synthesis of Proteins

Introduction to Synthetic Protein Synthesis

• Synthetic protein synthesis is different from natural protein synthesis in the human body.

• Our focus is on creating proteins in a lab setting.

• Proteins are made of long chains of amino acids arranged in a specific order.

Importance of Specificity in Protein Synthesis

• Changing the order of amino acids can lead to the loss of protein function and may result in diseases.

• Synthetic synthesis must be:

  • Highly specific to ensure the correct order of amino acids.

  • Have a good percent yield to produce usable products.

Example: Combining Amino Acids

• Using Glycine and Alanine as a simple example:

  • Possible products when combining two amino acids:

    • Glycine-Alanine (desired product)

    • Alanine-Glycine (another product)

    • Glycine-Glycine (identical)

    • Alanine-Alanine (identical)

• A total of four different products can potentially arise from just these two amino acids.

Challenges in Synthetic Protein Synthesis

• As the number of amino acids increases, the number of potential products increases dramatically.

• Need to focus on directing the reaction to yield only the desired product.

Enhancing Specificity in Reactions

• Use of activating and deactivating reagents to control which reactions occur:

  • Activate: Enhance the reactivity of the carboxylate group of Glycine to promote the desired reaction.

  • Deactivate: Reduce reactivity on the amino group of Glycine and the carboxylate group of Alanine.

Chemicals Used in Synthetic Reactions

• Activating Reagents:

  • SOCl2 (Thionyl Chloride): Converts the carboxylate group into an acid chloride and promotes nucleophilic attack.

• Deactivating Reagents:

  • T-Boc (Di-tert-butyl dicarbonate): Blocks the amino group from acting as a nucleophile, reducing unwanted reactions.

  • The transformation of the carboxylate group into an ester deactivates it as well.

Formation of Peptide Bonds

• Use of a dehydrating reagent, DDC (Dicyclohexylcarbodiimide), to catalyze the formation of the peptide bond between amino acids.

• DDC facilitates the hydration reaction leading to bond formation:

  • Peptide bond formation occurs after activating and blocking the proper groups.

• After synthesis:

  • Blocking groups can be removed under mild acidic conditions.

Merrifield Procedure for Improved Yield

• Named after Bruce Merrifield, it was developed in the 1960s.

• The procedure involves:

  • Anchoring the peptide chain to a polymeric material, from the carboxylate to the amino end.

  • Continuous attachment of amino acids to the anchored chain to synthesize the intended protein.

• The body synthesizes proteins in reverse; it starts from the amino end to the carboxylate end.

Summary of Key Steps in Synthetic Protein Synthesis

• Ensure proper activation and deactivation of amino groups.

• Use Merrifield procedure to achieve a higher yield and maintain specificity.

Conclusion

• Understanding synthetic protein synthesis is vital for producing effective proteins in lab settings, highlighting the importance of reagents and techniques used to control reactions and yield.