Amino acids are the fundamental building blocks of proteins and play an important role in maintaining human health. However, in the environment, amino acids are easily damaged by factors such as oxidation, acidity, and alkalinity. In order to protect the integrity and stability of amino acids, people have developed some methods and techniques to protect amino acids. 

Omizzur Peptide Ltd will spend 5 minutes introducing the protected amino acids and peptide synthesis. You can bookmark this page for your scientific research.

What is Protected Amino Acids?

Protected amino acids refer to amino acid derivatives whose functional groups react with other protective groups to block the activity of amino acid functional groups. This type of amino acid is more stable and easy to store and use.

The commonly used amino acid groups for protection include FMOC, BOC, and CBZ. We call them fmoc-amino acids, boc-amino acids, and cbz-amino acids.

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What is the Role of Protected Amino Acids?

1. Prevent oxidation: Oxidation is one of the main causes of amino acid decomposition and inactivation. Oxidative reactions can cause changes in the structure of amino acids, leading to their loss of activity. Therefore, in order to protect amino acids, antioxidant methods can be adopted, such as adding antioxidants such as vitamin C and vitamin E.

2. Inhibition of acid-base reactions: Acid-base reactions are also an important factor in the decomposition of amino acids. Under acidic or alkaline conditions, amino acids undergo acid-base neutralization reactions, leading to structural changes and loss of activity.

To protect amino acids, the method of adjusting pH value can be adopted to keep them under suitable acid-base conditions and maintain their stability and activity.

20 Commonly used Fmoc Protected Amino acids in Peptide Production：

*** The above are the most commonly used fmoc-protected amino acids in peptide synthesis.  Omizzur provides stable quality year-round. If you need other amino acid derivatives, please contact customer service for product catalogs and prices.

What are the Uses of Protected Amino Acids?

1. Peptide preparation: fmoc/boc amino acids, as one of the main components of peptide, are widely used in peptide synthesis and large scale peptide production. To protect the activity and stability of amino acids, appropriate protective groups can be used to protect amino acid molecules from unnecessary damage during the reaction process.

2. Biotechnology: Amino acids play an important role in biotechnology, such as protein engineering and antibody preparation. In order to protect the integrity and stability of amino acids, appropriate protection strategies can be adopted, such as using protective groups to protect the stability and activity of amino acid molecules during the reaction process.

3. Cosmetic industry: Amino acids are also widely used in the cosmetics industry to regulate and protect the skin. In order to protect the activity and stability of amino acids, appropriate formulas and additives such as moisturizers, antioxidants, etc. can be adopted to protect the function of amino acids in cosmetics.

Classification of 20 Common Amino Acids

20 amino acids can be divided into 4 groups based on their physicochemical properties:

① Non polar and hydrophobic amino acids:

Glycine (G), alanine (A), valine (V), leucine (L), methionine (M), isoleucine (I), phenylalanine (F), and proline (P). Supplement: Methionine, also known as methionine (M).

② Polar and neutral amino acids: 

tryptophan (W), serine (S), tyrosine (Y), cysteine (C), asparagine (N), glutamine (Q), and threonine (T).

③ Acidic amino acids: 

aspartic acid (D) and glutamic acid (E).

④ Basic amino acids: 

lysine (K), arginine (R), and histidine (H).

(Omizzur biotech tip: Multiple hydrophobic amino acids appear consecutively in peptide sequences, which is a difficulty in solid-phase synthesis. Hydrophobic amino acids cause the carrier resin of solid-phase synthesis to condense, resulting in the closure of amino acid sites. The connecting sites are blocked, and subsequent amino acids cannot be connected normally. Therefore, for peptide sequences of the same length, the synthesis of hydrophobic amino acids is more difficult.)

The Difference Between Synthetic Amino acids and Natural Amino acids

Artificial synthesized peptides are different from the synthesis of natural proteins. Artificial solid-phase synthesis generally involves gradually adding amino acids in sequence from the C-terminus to the N-terminus for connection. In order to reduce the generation of side reactions in synthesis, amino acids are used with protective groups, which not only protect the active groups that are temporarily not used in synthesis. And the 20 common natural amino acids are all L-amino acids. In addition to L-amino acids, there are also D-amino acids used in artificial synthesis. This enables artificial synthesis of peptide sequences that do not exist in the natural world.

Amino acid-protecting groups used in artificial peptide synthesis:

Common amino end protecting groups: Fmoc protecting group, Boc and Cbz protecting group, Alloc - (allyl) carbamate

Common carboxyl end protecting groups: tBu ： (tert-butyl) ester，PfP ： (pentafluorophenyl) este

Common side chain protective groups: Boc, OtBu, tBu, Pbf, Trt protecting group.

How to Use Protected Amino Acids to Synthesize Peptide Sequences?

Give an example of the Fmoc protection strategy used by Omizzur peptide. Synthesis consists of the following steps:

① Hanging resin: Select and weigh the corresponding amount of resin according to the order, and put it into the reactor for swelling and standby.

② To protect: The columns and monomers protected by Fmoc must be removed with 20% piperidine to remove the amino protecting groups.

③ Detection: Check whether the protective group has been removed, and whether the amino group has been exposed. (Omizzur Biology commonly uses ninhydrin as a detection reagent. If the result is positive, it is judged that the amino group is exposed.)

④ Activation and cross-linking: The carboxyl group of the next amino acid is activated by an activator. Activated monomers react with free amino groups to crosslink, forming peptide bonds. We need to note that the amount of amino acid input is not arbitrary. To ensure the accuracy of peptide chain synthesis; Amino acids, condensation agents, and bases have a ratio. Here is a reference scale provided. (Scale (mol): Amino acid: Condensing agent: Base=1:3:3:6)

⑤ Detection: Check if the required amino acids have been connected. The result is negative, indicating that the amino acids have been completely connected.

⑥ Cycle: Repeat cycle ② - ⑤ until the synthesis is completed.

⑦ Cut and deprotect the synthesized peptide from the resin. (The Fmoc strategy uses TFA (strong acid) to cleave peptides from the resin.)

Omizzur Fmoc-Protected Amino Acids & Peptides

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