The K18PEPTIDE™ powering the leave-in molecular repair hair mask and both steps of  K18REPAIR™, K18’s salon-exclusive damage repair service, was intentionally designed to reverse damage on all hair types hair—from within. 

How was it created? By combining cutting-edge biotechnology with practical salon expertise through AI-assisted design, rigorous lab testing, and real-world validation by professional stylists.

Today we’ll walk you through every step of how this revolutionary biomimetic peptide came to deliver the healthy hair results you know and love.

let’s start at the beginning—why a peptide?

As you may know, hair is a multilayered structure made predominantly of keratin proteins. The outer layer, called the cuticle, is composed of keratins that form overlapping tile-like cells. Beneath the cuticle, keratins form long polypeptide chains that weave together to form larger, stronger structures. 

Keratin proteins are made of smaller building blocks called amino acids. Proteins are large molecules composed of long chains of amino acids called polypeptides, while shorter chains of amino acids are called peptides. 

Hair’s elasticity and strength largely depend on the integrity of the proteins and chemical bonds between keratin proteins within it. Peptide bonds join keratin’s individual amino acid building blocks along hair’s length. Disulfide bonds crosslink these chains to stabilize hair’s structure across its width. When damage occurs, these bonds break, weakening hair. Other weaker interactions, called hydrogen and ionic bonds, also contribute to hair’s stability, but they are easily broken by water, causing frizz. 

The best way to repair damaged polypeptide chains is to mimic keratin’s natural structure. By scanning the keratin genome, K18’s team of scientists found a peptide with optimal characteristics to provide hair repair from within.

in-silico + AI peptide design

Before selecting and testing keratin peptides physically, K18 scientists started with in-silico (computer-based) experiments powered by artificial intelligence (AI).

Through molecular models—computer simulations mimicking the molecular dynamics between keratin and peptides—over 1,235 peptide sequences of the human hair genome were analyzed to identify the best peptide structure and sequence for hair repair.

Molecular modeling showed how each peptide functioned under different conditions and when combined with different ingredients. These in-silico experiments enabled K18s scientists to narrow down options for the selection of the right hair repair peptide. 

then, in-vitro model testing

The team then analyzed those 1,235 peptides to assess those with a high affinity for human hair keratin through a series of in-vitro—chemical and physical—experiments in the lab.

These tests revealed that the K18PEPTIDE™ had the right size and charge to penetrate to the core of the hair fiber and the right chemistry to form a network of bonds to repair damaged polypeptide chains.

testing peptide effects on strength & elasticity

Hair’s keratin has a helix-like structure. When stabilized by disulphide and hydrogen bonds, these proteins are hard to stretch, making them more elastic. When stretched too far, they can break. Hair with higher elasticity and strength has higher resilience to stretching and can withstand more stress before breaking.

Because the K18PEPTIDE™ penetrates to the core of the hair fiber and is able to click into to hair’s proteins and efficiently form a network of bonds, it’s uniquely able to repair damage and improve elasticity, strength, and therefore service and styling outcomes.