Peptide & Protein Nomenclature in Skincare
The goal of this educational post is to help you understand the difference between these two molecules, where they come from, and how to identify them on ingredient listings.
The simplest explanation as to what these molecules are is “a chain of amino acids”. If anyone remembers protein biochemistry from school, these are chains of amino acids, with varying chain lengths (number of amino acids), connected to each other via covalent amide/peptide bonds. How many amino acids are present in the chain, and their specific arrangement will determine if it is a peptide or protein, and its biochemical functionality. There are only 20 amino acids that are either naturally produced (non-essential) or required in diet (essential). From only these 20 amino acids there is an astonishing number of different molecules that can be created, each with completely different behavioral characteristics.
A peptide is any molecule that has anywhere from 2-50 amino acids in the chain (BTW in Biochemistry we call the amino acids “residues”). A molecule with 51 or more amino acid residues is called a protein. Peptides are often called small fragments of proteins. Most of the peptides you find in personal care products are synthetically created in the lab via chemical reactions that allow the amino acids to form these chains with high specificity. The scientists creating these molecules can look at larger proteins and assemble fractions of them in the lab. For instance, Matrixyl is the trademarked name for one of the oldest and most evidence-based peptides in skincare. It is known as a “matrikine”, which is essentially a fragment of larger matrix molecules (collagen, GAGs, et.). It tricks the skin into producing more of these substances.
Where do you get these peptides and proteins from? For the sake of simplicity, we will only be discussing lab-made and human cell-derived molecules. You can get peptides via chemical hydrolysis and protein denaturing of larger proteins “in nature” (i.e., human hair, animal hair, plants, etc.). Peptides or Proteins can be created in the lab, as mentioned, via a synthetic or recombinant process.
Synthetic is when you use no cellular material to make the molecule, just amino acids, and other chemicals and reagents to put the molecule together in the lab. Synthetics can be used to create completely new peptides that aren’t naturally found in the body or to create peptides/proteins that ARE found in the body. Recombinant is when you take human DNA coding for a specific protein, implant it in a non-human cell (oftentimes bacterial cells are used as the vector here, but plants cells have been used), hijack the cell’s genetic machinery, and get it to manufacture and release that exact same, molecularly identical human protein. With both methods, you are only producing ONE peptide or protein molecule at a time. And with synthetics, you are limited to relatively small molecules.
You can also get these molecules through the laboratory culture of human cells. You take the cells (yes, they must be alive) and in the lab you create the perfect environment for them to grow (mimicking their environment in the human body). They’ll start to grow and proliferate (produce copies of themselves), and as they do, they are in literal communication with each other by producing and pumping out their genetically pre-determined portfolio of molecules, which you will all recognize as being Cytokines, Growth Factors, etc. These are proteins, but the cells also produce a significant number of other biomolecules including peptides, chemokines, GAG’s, enzymes, lipids, sugars, etc. As you can see the cells aren’t producing one molecule at a time, they are producing a naturally secreted and physiologically balanced portfolio of these molecules. And they are produced in ABUNDANCE (depending on cell type)!
Ok, now that we know what these molecules are, and where they come from, how do you recognize them on an ingredient listing? This is where it can get slightly complicated, as indicated by someone’s recent post. Let’s begin by explaining the INCI. This stands for International Nomenclature for Cosmetic Ingredients. There is a global organization that determines the LEGAL way you are supposed to list your ingredients on your bottles/boxes, so that they can be identified and recognized globally.
In the INCI for a lot of these molecules you will often see “polypeptide”, or “oligopeptide”, of “tripeptide”, etc. What does it all mean? A peptide that consists of 2-20 amino acids in length is called an OLIGOPEPTIDE, and any chain that contains 20+ amino residues is called a POLYPEPTIDE (poly=many). However, the oligopeptide range can be further identified by how many amino acids are in the chain. EXAMPLE:
Dipeptide - 2 amino acids
Tripeptide - 3 amino acids
Tetrapeptide - 4 amino acids
Pentapeptide - 5 amino acids
Hexapeptide - 6 amino acids
Heptapeptide - 7 amino acids
Octapeptide - 8 amino acids
Nonapeptide - 9 amino acids
Decapeptide - 10 amino acids
And so on… USUALLY, if the peptide is in the 2-10 amino acid length range, it will be called by its residue content as explained above. Then from 10-20 amino acids, it is usually called Oligopeptide. Again, anything above this now becomes Polypeptide. Not to complicate things further, but there is an exception here! If the molecule consists of more than 20 amino acids, but there is only ONE single chain (not many linked together) it will still be called an Oligopeptide.
Let’s look at a few molecules and see how they would be listed (INCI) on the packaging. For isolated, individual molecules, you will often see the COMMON name listed with the INCI name.
EXAMPLE #1: Epidermal Growth Factor (EGF)
EGF would be the COMMON name, and the INCI name for this molecule is sh-Oligopeptide-1. Without this education, one would assume this is a peptide by category, because it says peptide in the name. But EGF is a protein because it has more than 50 amino acids. 53 to be specific, one of the smaller proteins. Remember I said there is an exception to the oligopeptide nomenclature? If EGF has 53 amino acids, how is it an Oligopeptide? Because EGF is made up ONE chain, not multiple chains pieced together.
You can see that the INCI name gives no indication as to how many amino acid residues there are. That would be far too complicated (unless less than 10 residues). So, what does the rest of the INCI name mean? The prefix says sh. That stands for synthetic human. This means that it was produced synthetically as mentioned above, but it is the exact same molecule you would find in the human body. Molecularly identical. If you see a prefix that says rh, which means recombinant human, it means it was produced in vector cells (bacteria usually) with human DNA. Either way, they would be identical molecules. You can find EGF in both rh and sh forms.
And finally, what does the 1 mean as the suffix? 99% of the time people think it has to do with number of amino acids, but that would be incorrect. It has to do with global INCI registration. The number indicates the order in which the molecule was registered. Think about it - you could have HUNDREDS or THOUSANDS of different peptides that all have the same tripeptide, oligopeptide, or polypeptide name. How do you tell them apart? The order in which they were registered! So, EGF is the very FIRST Oligopeptide to be registered in the global regulatory database. Hence its name is sh-Oligopeptide-1.
EXAMPLE #2: ARGIRELINE
This is the trademarked name for a peptide and its INCI name is Acetyl Hexapeptide-8. This is a synthetic peptide. It is a fragment of cellular membrane protein that the neurotoxin botulinum (Botox) binds to, hence it used to soften dynamic expression lines. What can you already tell me about the peptide? It is a Hexapeptide, so it has 6 amino acids! And it was the 8th Hexapeptide ever registered. What about the acetyl prefix?
MOST of these peptides (and certainly all proteins) are very large molecules. On average, each amino acid residue has a molar mass of around 110 Daltons. So, if we look at something like EGF, with 53 amino acids, its molar mass is around 6,000 Daltons. Argireline has a molar mass around 888 Daltons (well, about 660 Daltons prior to the acetylation explained below). We all know about the 500 Dalton Rule in skincare. There is more nuance to this, but largely anything over 500 Daltons will not penetrate the skin. So, what can you do to facilitate the penetration?
You can use penetration enhancers, various forms of liposomes, and/or you can add lipid moieties to the molecule. Say what? In Chemistry, a moiety is “a part of the molecule” that can be found in other molecules as well. These are often called functional groups, or sometimes “arms” when being colorful in explanation. They can be naturally occurring or, in this case, can be ADDED to the molecule to give it different biochemical properties. In the case of Argireline, the molecule has been acetylated, meaning one of the Hydrogens on the peptide has been replaced with an Acetyl functional group (CH3CO). This increases the molecules lipophilicity so it can wiggle its way into the skin’s lipid bilayers easier, even though it made the molecule slightly larger (888 Daltons). You might also see prefixes that say palmitoyl or myristoyl, and these are other “arms” added to the molecule to increase penetration into skin. In this case the arms are fatty acids. So, the molecule Acetyl Hexapeptide-8 is the 8th Hexapeptide ever registered, and it has been acetylated for enhanced skin penetration.
EXAMPLE #3: Human Cell Derived Proteins and Peptides
Now that we have looked at two different types of ISOLATED peptides and proteins, let’s explore how we get them from actual human cells. You will know you have human cell-derived molecules when you see the INCI Conditioned Media, and a prefix that tells you which cell was used, i.e., Human Bone Marrow Stem Cell Conditioned Media, Human Fibroblast Conditioned Media, or Human Adipose Stem Cell Conditioned Media.
What does this mean? The process is relatively straightforward. You take human cells (again, must be alive), and in the lab you put them in a cell culture dish (think petri dish) that has a special liquid inside. This liquid is called the media, and it consists of various nutrients, sugars, amino’s, electrolytes, etc. that the cells feed on to maintain their viability. We need to be sure that proper pH levels are maintained, osmolality is maintained, etc., so the cells can feel like they are at home. A few extra steps can be taken to ensure you are creating the perfect environment for the cells, such as anchoring them on tiny beads so they grow in a three-dimensional suspension and putting them in bioreactors to induce hypoxia (low O2 levels), though not all cells should be grown in hypoxic environments as it can stress them out and they become extra defensive (i.e., they produce a lot of pro-inflammatory molecules).
Now that you have created the perfect environment for them, they will start to grow, proliferate, and replicate themselves in the culture dish. As they do this, the cells will communicate with each other by releasing their portfolio of biomolecules such as Cytokines, Growth Factors, etc. These proteins are signaling molecules (think text messages between cells) that coordinate the activity of the cells. The molecules are released into the media. Once the cells have no more room to grow (we call this max expansion), fine filters are used to remove the whole living cells from the media so they can be transferred to another culture dish filled with media (we call this passage) to continue the process repeatedly (until the cells finally poop out, differentiate, become senescent, etc.). Once the cells have been removed, all you are left with is the media that is now rich in the proteins that were secreted into it. That media is now called conditioned.
As mentioned earlier, the cells will pump out all the molecules they are genetically programmed to produce. Cytokines, Growth Factors, Chemokines, Sugars, GAG’s, Enzymes, Peptides, etc. They do NOT produce one molecule at a time like the synthetic or recombinant processes. They are producing hundreds if not thousands of these molecules, which is why you will never see all the molecules they release listed on the ingredient deck. It would be far too complicated and LONG, requiring the largest packaging imaginable for a simple bottle. So, the global regulatory body decided that to standardize “the collection of all cell-derived molecules” for INCI purposes, they simply call it Conditioned Media, with the cell that was used as the prefix. Just know that within that one INCI, an immense number of molecules will be found within (though this is also cell-dependent, as some produce less molecules than others).
The media is now ready to be put into skincare products. However, if you just use the media as-is, you will run into a few issues. Stability and lack of skin penetration. Cell-derived molecules in a media need to be stabilized, and as mentioned above, most of the molecules are quite large so they can’t really get into the skin efficiently. One method used to stabilize and enhance delivery is to wrap the molecules inside liposomes, or a more advanced version of liposomes called Nanostructured Lipid Carriers. These small “lipid envelopes” protect and stabilize the precious molecules and promote penetration of them through human lipid bilayers and cell membranes.
SUMMARY
I hope this explanation can help you better identify the proteins and/or peptides that might be in your skincare products. We know that we can get these molecules from predominantly three sources:
· Completely synthetic where scientists are using building blocks (amino acids) and piecing them together to form chains (peptides). This can also be used to create human identical molecules and the peptide/protein prefix will be sh (synthetic human). This method has some limits and only peptides and small proteins can be created. Only 1 type of protein/peptide can be produced at a time.
· Recombinant processes where human DNA coded for the specific protein is implanted in non-human vector cells (bacterial), and the cell then takes those instructions and manufactures the human molecule that is identical to the ones found in the body. The prefix would be rh (recombinant human). Only 1 type of protein/peptide can be produced at a time. This is the most efficient and economical way to produce larger proteins at scale. In fact, the bulk of the insulin today is produced via recombinant technology. Insulin was the very first human protein drug produce via this tech.
· Human Cell Culture, where living cells are grown in the right environment to get them to pump out their full portfolio of the molecules, they are genetically hamstrung to produce. You get MYRIAD molecules, not just 1 like the two other methods. The INCI would read Conditioned Media with the prefix being the cell source that was used, i.e., Human Bone Marrow Stem Cell Conditioned Media.
And remember that these molecules are rather large for the most part and need assistance getting into the skin. Liposomes, Nano Lipids, lipophilic moieties, penetration enhancers, etc. can all be used to facilitate this. However, some proteins are so large that no matter what, they would never get into the skin. Collagen is the perfect example! The triple helix bundle contains around 3000 amino acid residues. That means it has a molar mass of around 330, 000 Daltons. Other than providing some surface moisture retention, collagen in skincare is nonsensical.
Usually, the INCI will contain the COMMON name AND the legally required INCI name. For instance, EGF will often present on the INCI as sh-Oligopeptide-1 (EGF), or EGF (sh-Oligopeptide-1). The only LEGAL requirement is to list the INCI name. You would have to do a search to find out what the peptide or protein is if the manufacturer doesn’t call it out.
And finally, this is just the BASICS of peptide/protein nomenclature. You will find some peptides that don’t fit this convention and can get really complicated for you to understand. For instance, one peptide’s INCI name is Dipeptide Diaminobutyroyl Benzylamide Diacetate and another one is called Tetradecyl Aminobutyroylvalylaminobutyric Urea Trifluouroacetate. These are very complex molecules with multiple groups added and are not as simple as your basic proteins/peptides. But that story and explanation will be for another day. J
