keratins
Enable an AI agent to recognise keratin proteins and keratin-derived materials, assess their molecular and material state, and select actions supported by their identity, processing history and measured behaviour.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
Researched by: Codex + Grok
Purpose and description
Enable an AI agent to recognise keratin proteins and keratin-derived materials, assess their molecular and material state, and select actions supported by their identity, processing history and measured behaviour.
Keratins are a family of cysteine-rich, intermediate-filament-forming fibrous proteins that assemble as obligate type I/type II heterodimers into ~10 nm filaments, conferring mechanical resilience to epithelia and to cornified appendages (hair, nails, claws, horns, feathers).
It can be Assign or challenge a keratin identity using molecular evidence and explicit alternative identifications.; Select complementary measurements to resolve composition, chain integrity, assembly and sulfur condition.; Evaluate whether a preparation can be investigated for filament reassembly, dissolution, casting or crosslinking.; Compare keratin preparations under matched hydration, composition and test conditions.; Choose processing and storage conditions from preparation-specific evidence and identify properties requiring revalidation.; Route an intended use to the relevant tissue, product or biological evaluation model with the keratin evidence attached..
Distinguishing features
Require sequence or discriminating peptide evidence for keratin-family assignment; fibrous appearance, insolubility or a protein spectrum alone cannot distinguish keratins from collagen, silk or other structural proteins.
For an intermediate-filament identity, record type I/type II assignment and evidence for compatible heterotypic assembly; assembly failure in a processed sample does not alone exclude keratin ancestry. See [recombinant keratin assembly experiments](https://pubmed.ncbi.nlm.nih.gov/1691189/).
Distinguish a keratin protein fraction from a keratin-rich tissue or composite by identifying accompanying proteins and nonprotein constituents.
For material labelled beta-keratin, require molecular-family identification before treating the label as equivalent to intermediate-filament keratin; a beta-sheet signal alone does not settle that boundary.
Distinguish intact keratin preparations from hydrolysates and chemically modified derivatives using chain-size distribution and processing evidence. See [comparative wool extraction experiments](https://ourarchive.otago.ac.nz/esploro/outputs/journalArticle/Evaluation-of-keratin-extraction-from-wool/9926515221701891).
Scope
+ Keratin protein identities, sequence variants and type I/type II composition
+ Keratin assemblies and their relationship to the surrounding biological material
+ Extracted keratin fractions, recombinant preparations and traceable keratin derivatives
+ Chain integrity, sulfur chemistry, hydration and structural condition
+ Evidence needed to select processing, storage, testing and material-use actions
- Whole hair, wool, nail, horn, feather and skin anatomy or product classification
- Keratin genes as genomic entities and their inheritance
- Clinical diagnosis and treatment of keratin-associated diseases
- Keratin-associated proteins as independent protein families
- Complete cosmetic, textile or biomedical formulations and their product-level approval
Characteristics
- Keratin molecular identity
- Protein accession and version, species, sequence variant; unresolved mixture or unconfirmed label Determines whether evidence and expected behaviour apply to the material being assessed.
- Biological or recombinant origin
- Source organism and tissue, or expression construct and host, linked to preparation Connects the keratin to expected constituents and relevant production history.
- Type I/type II composition
- Identified constituents and molar ratio, with analytical uncertainty; unknown where unresolved Supports evaluation of partner availability for filament assembly.
- Keratin fraction
- Mass percent on a stated wet or dry basis, with assay method Separates keratin properties from effects of associated proteins, additives and tissue residues.
- Polypeptide size distribution
- kDa distribution and fragment fraction, with method Helps distinguish preserved chains from fragmented material and qualify processing options.
- Assembly condition
- Dispersed chains, oligomers, filaments, network, aggregates, mixed or unmeasured Identifies the structural level responsible for current behaviour.
- Sulfur chemical condition
- Free thiol and disulfide content in micromoles per gram; identified oxidised or derivatised sulfur species Supports decisions about reduction, oxidation and potential crosslinking without relying on total sulfur alone.
- Secondary-structure signature
- Method-specific spectral indicators or estimated helix, sheet and disordered fractions Helps track conformational changes while keeping them distinct from molecular-family identity.
- Hydration
- Grams of water per gram of dry material at stated temperature and relative humidity Makes comparisons of swelling and mechanical behaviour interpretable.
- Soluble and dispersed fractions
- Mass percent at specified solvent, pH, ionic strength, temperature and equilibration time Distinguishes dissolution from suspended particles when selecting processing conditions.
- Mechanical response
- Modulus and strength in MPa, strain in percent, or rheological moduli in Pa, with specimen and test conditions Supports use decisions for the tested material form without assigning one universal strength to keratins.
- Processing lineage
- Ordered extraction, purification, chemical treatment, drying and storage events Explains which native properties may have been altered and which require remeasurement.
Also called
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 7 bundles · 13 layers · 20 findings · 32 questions.
Keratin identity and boundaries Establish what the keratin designation refers to and how securely that identity is supported.
Keratin labels can refer to identified proteins, heterogeneous tissue extracts or extensively modified materials.
Molecular family assignment
Resolve protein-family membership and constituent identities.
Identity evidence
Record the evidence supporting each keratin assignment and the alternatives it excludes.
- Which species-specific protein identities or sequence variants are supported by sequence, discriminating peptides or validated recognition assays? definition
- Can the evidence distinguish those keratins from other intermediate-filament proteins and accompanying structural proteins? boundary
Keratin label interpretation
Separate protein identity from tissue names, historical terms and derivative labels.
Label-to-material boundary
State whether the subject is a protein, mixture, tissue constituent or derivative, preserving unresolved terminology.
- Does keratin here denote identified proteins, a keratin-rich material, an extract or a hydrolysate? definition
- If beta-keratin is claimed, what molecular evidence resolves whether it denotes a corneous beta-protein or another use of the term? boundary
Keratin origin and composition Connect the preparation to its biological or recombinant source and account for its constituents.
Source names alone cannot establish the protein mixture or the contribution of accompanying material.
Source context
Record where the keratin originated and which source details affect interpretation.
Source-to-preparation link
Trace the preparation to a tissue source or recombinant production route.
- Which organism and tissue supplied the material, or which construct and expression host produced it? provenance
- Which source lots were pooled, and which source details remain unavailable? provenance
Constituent balance
Distinguish keratin constituents from associated proteins and nonprotein matter.
Keratin and companion fractions
Account for the measured composition and the unidentified remainder.
- What fractions are assigned to keratins, keratin-associated proteins, other proteins and nonprotein constituents on a stated mass basis? measurement
- Which extraction residues, additives or source constituents could account for behaviour attributed to keratin? boundary
Keratin assembly and architecture Describe partner composition, assembly competence and observed organisation.
Identifying keratin chains does not establish whether they currently form functional filaments or a load-bearing network.
Heterotypic partners
Establish which type I and type II constituents are available and whether their assembly has been demonstrated.
Partner availability and competence
Record partner identities, relative abundance and preparation-specific assembly evidence.
- Which type I and type II constituents are present, and what is their measured molar ratio? measurement
- Under which tested conditions do these constituents assemble, and what evidence distinguishes filaments from nonspecific aggregates? measurement
Observed keratin organisation
Connect molecular conformation to filament, network and specimen architecture.
Assembly state and alignment
Describe the organisation actually observed at each measured scale.
- What microscopy, scattering or spectroscopic evidence supports the reported chain, filament, aggregate or network state? measurement
- What alignment, packing and matrix relationships must be recorded before interpreting the specimen's directional behaviour? measurement
Keratin chemical integrity Track chain preservation and chemical changes relevant to keratin behaviour.
Processing can change chain size and sulfur chemistry independently, so neither an origin label nor a single assay establishes current integrity.
Chain preservation
Assess fragmentation, modifications and preservation of regions needed for the intended function.
Intact chains and fragments
Record chain-size evidence and limitations in assigning intactness.
- What molecular-size distribution and peptide coverage support the reported intact-chain and fragment fractions? measurement
- Which observed truncations or modifications require testing before assuming filament assembly or film formation remains possible? action
Sulfur and crosslink condition
Distinguish thiols, disulfides and chemically altered sulfur from other crosslinks.
Crosslink reactivity
Record measured chemical species and evidence for their accessibility or participation in crosslinking.
- What free thiol, disulfide and oxidised or derivatised sulfur species have been measured, using which mass basis and assay? measurement
- What evidence supports reduction, reoxidation or another crosslinking action for this preparation? action
Keratin material response Describe behaviour under defined hydration, solvent, load and exposure conditions.
An agent needs condition-specific measurements to compare keratin materials and avoid transferring bulk tissue properties to isolated proteins.
Water and solvent response
Separate water uptake, swelling, dissolution and dispersion.
Hydration and solubility window
Record how the preparation responds to controlled moisture and liquid environments.
- What water uptake or swelling occurs at specified temperature, humidity or immersion conditions? measurement
- What fraction dissolves rather than remains dispersed at the tested pH, ionic strength, solvent composition and exposure time? measurement
Load and exposure response
Assess mechanical performance and changes caused by relevant exposures.
Conditioned performance
Tie performance to the specimen form, conditioning and evidence of deterioration.
- What mechanical or rheological response was measured at the stated hydration, geometry, orientation, temperature and loading rate? measurement
- Which thermal, chemical or enzymatic exposures change chain integrity, mass or performance enough to rule out the intended action? action
Keratin processing and use decisions Translate preparation history and measured condition into justified next actions.
Keratin provenance must remain connected to treatment-induced changes and the requirements of the intended use.
Extraction and transformation history
Record treatments that produced the current keratin fraction.
Treatment-to-property link
Connect extraction, purification and subsequent processing to measured changes.
- Which reduction, oxidation, sulfitolysis, hydrolysis or other treatments were applied, with what reagents, conditions and sequence? provenance
- Which before-and-after measurements demonstrate retained identity, chain integrity and removal of processing residues? measurement
Preparation-specific action selection
Identify supported operations and the evidence still needed for the intended use.
Action readiness
State whether this preparation is ready for a proposed operation or requires further characterisation.
- Which measured properties support the proposed reassembly, casting, blending, crosslinking or storage conditions? action
- Which unresolved residues, stability limits or performance requirements require testing or referral to the intended product model before use? action
Evidence and external alignment What the world already says about this thing, gathered so the model can be checked against it.
A model that cannot be lined up against existing standards, identifiers and practice cannot be adopted by anyone who already uses them.
Reported evidence
Findings from the breadth pass, kept separate from the structural claims.
Kinds and varieties
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Type I (acidic) epithelial keratins (human K9-K28)
- Type II (basic/neutral) epithelial keratins (human K1-K8 and related)
- Hair/trichocyte keratins (type I K31-K40 and type II K81-K86, plus related hair keratins)
- Soft (epithelial/epidermal) keratins versus hard (appendage) keratins, distinguished by cysteine content and disulfide cross-linking
- α-keratins of mammals (coiled-coil intermediate-filament proteins)
- Reptile and bird corneous β-proteins, historically called β-keratins, which are not intermediate-filament keratins
- Cytokeratins, the pathology-lab name for epithelial keratins used in immunohistochemistry (e.g. CK7, CK20)
- Industrial/commodity keratins: wool, horn, hoof, feather, and hydrolyzed keratin used as fiber or cosmetic ingredient
- Which of these kinds and varieties hold for the sense of keratins this model covers, and on what evidence? provenance
Identifiers and schemes
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Wikidata - Q169921 - Item for keratin as a protein class.
- HGNC gene symbol - KRT1-KRT86 (and related KRT genes) - Human gene nomenclature; protein products are often written K1, K14, etc.
- UniProt keyword - KW-0416 - Keyword Keratin; individual chains have their own UniProt accessions (e.g. P04264 for human KRT1).
- INCI (cosmetics) - Keratin; Hydrolyzed Keratin; Hydrolyzed Hair Keratin - Ingredient names for intact or hydrolyzed keratin in personal-care products.
- CAS - 68238-35-7 (keratin); 69430-36-0 (hydrolyzed keratin, commonly cited) - Commodity/cosmetic registry numbers, not a unique molecular identity.
- Which of these identifiers and schemes hold for the sense of keratins this model covers, and on what evidence? provenance
Standards and regulation
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- HUGO Gene Nomenclature Committee (HGNC): official KRT gene symbols and the keratin gene group.
- Schweizer et al. 2006 consensus (Journal of Cell Biology / accompanying keratin community agreement): protein numbering K1, K5, K14, etc., replacing older cytokeratin catalog numbers in cell biology.
- EU Cosmetic Products Regulation (EC) No 1223/2009 and CosIng/INCI: naming and safety listing of Keratin and Hydrolyzed Keratin as cosmetic ingredients.
- ISO 17751 (parts 1-2) and related IWTO/ISO wool-fibre test methods: identification and quantification of animal-hair (keratin) fibres in textiles.
- Clinical immunohistochemistry practice (CAP/CLSI-aligned lab protocols, not a single keratin statute): cytokeratin panels (CK7/CK20 and others) used to classify epithelial tumours.
- Which of these standards and regulation hold for the sense of keratins this model covers, and on what evidence? provenance
Real-world use
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Structural protein of human epidermis, hair shafts, nails, and of wool, horn, hoof, claw, and feather.
- Diagnostic IHC: epithelial versus non-epithelial lineage, and CK7/CK20 (and other keratin) profiles to suggest primary site of carcinoma.
- Mutation diagnostics: KRT5/KRT14 in epidermolysis bullosa simplex; KRT1/KRT10 in epidermolytic ichthyosis; selected hair-keratin genes in monilethrix and related shaft disorders.
- Textiles and materials: wool and other animal-hair fibres; historic horn and hoof goods; research use of extracted keratin as films, sponges, and wound-dressing scaffolds.
- Personal care: hydrolyzed keratin as a film-former/conditioner in hair and nail products.
- Which of these real-world use hold for the sense of keratins this model covers, and on what evidence? provenance
Typical measurements
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Monomer molecular mass (epithelial keratins) - 40-70 - kDa
- Intermediate-filament diameter - 8-12 (nominal ~10) - nm
- Cysteine content (soft epithelial versus hard appendage keratins) - ~2-7 (soft) vs ~8-18 (hard/hair/wool), residue percent; wool often cited near 11-12% Cys - mol% Cys (or g Cys/100 g protein)
- Isoelectric point (type I acidic versus type II basic) - ~4.9-5.4 (type I) vs ~6.5-8.5 (type II) - pI
- α-helix content of α-keratins (coiled-coil rod) - ~40-60 of the chain in the rod domain; fibre α-keratins often ~40-50 overall - %
- Which of these typical measurements hold for the sense of keratins this model covers, and on what evidence? provenance
Failure modes and hazards
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Dominant or recessive KRT mutations causing epidermolysis bullosa simplex, epidermolytic ichthyosis, pachyonychia congenita, palmoplantar keratodermas, and selected hair-shaft diseases (e.g. monilethrix).
- Chemical or thermal damage to hair/wool: cleavage of disulfide cross-links by bleaching, perming, or high heat, with loss of tensile strength and cuticle integrity.
- Misclassification in pathology if a limited cytokeratin panel is over-interpreted (some non-epithelial tumours can express keratins; some carcinomas lose them).
- Rare contact allergy or irritation attributed to hydrolyzed keratin or other animal-protein hydrolysates in cosmetics.
- Conservation and fraud issues around keratinous wildlife products (rhino horn, pangolin scale, tortoise shell) sold as traditional materials or medicines; these are keratin (or keratin-like corneous) tissues, not a distinct bioactive drug.
- Which of these failure modes and hazards hold for the sense of keratins this model covers, and on what evidence? provenance
Regional variation
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Clinical pathology, especially in older and North American lab usage, still says 'cytokeratin' (CK5/6, CK7, CK20); cell biology and HGNC use keratin/KRT.
- Herpetology and ornithology long used 'β-keratin' for sauropsid corneous proteins; current literature often prefers corneous beta-proteins (CBPs) to avoid implying they are intermediate-filament keratins.
- Textile trade names fibres by animal and processing (wool, cashmere, mohair, alpaca) rather than by keratin isoform.
- East Asian pharmacopoeial and folk practice historically treats horn, antler, and scale as materia medica; modern conservation law, not keratin chemistry, now dominates that trade.
- Which of these regional variation hold for the sense of keratins this model covers, and on what evidence? provenance
Neighbouring kinds and how to tell them apart
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Collagen - Collagen is an extracellular triple-helical protein rich in Gly-X-Y and hydroxyproline; keratins are intracellular (or residual cornified) intermediate-filament proteins rich in Cys and lack that collagen repeat. IHC (keratin vs collagen types) and amino-acid composition separate them.
- Other intermediate filaments (vimentin, desmin, neurofilaments, lamins) - Same ~10 nm filament architecture and rod-domain fold, but different genes, tissue restriction, and antibody profiles (e.g. vimentin in mesenchymal cells vs keratins in epithelia).
- Keratin-associated proteins (KAPs / KRTAPs) - Matrix proteins that cross-link hair-keratin intermediate filaments; they do not form the IF polymer themselves. Named KRTAP, not KRT.
- Cornified-envelope proteins (involucrin, loricrin, filaggrin) - They scaffold or aggregate keratin filaments during cornification but are not keratins; detected by distinct antibodies and genes (IVL, LORICRIN, FLG).
- Silk fibroin - A β-sheet structural protein of silkworm/spider silk, not an intermediate-filament keratin; fibre origin (Bombyx/spider vs hair/wool) and sequence/IR spectroscopy separate them.
- Chitin - A polysaccharide of arthropod cuticle and fungal walls, not a protein; dissolved by chitinase or detected as GlcNAc polymer, whereas keratin is a protein digestible by keratinases/proteases after disulfide reduction.
- Sauropsid corneous β-proteins (historical 'β-keratins') - Small β-sheet corneous proteins of feathers, scales, and claws; they are not type I/II IF keratins. Sequence family (corneous beta vs KRT) is the discriminator.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of keratins this model covers, and on what evidence? provenance
Sources
- New consensus nomenclature for mammalian keratins - The K/KRT numbering system, type I versus type II classes, and the split between epithelial and hair keratins.
- Structure and functions of keratin proteins in simple, stratified, keratinized and cornified epithelia - Tissue distribution, hard versus soft keratin, and the distinction from cornified-envelope proteins.
- HGNC gene group: Keratins (KRT) - Official human gene symbols KRT1-KRT86 and the type I/type II gene grouping.
- UniProtKB keyword: Keratin - Protein-family definition, cysteine-rich filament character, and accession-level identifiers for individual keratins.
What the second pass must settle
- Does the registry intend keratins to include corneous beta-proteins historically labelled beta-keratin, or should this entry record only a boundary relation to them?
- What evidence threshold should distinguish a verified keratin constituent from a commercial keratin claim in a highly processed mixture?
- At what degree of hydrolysis or chemical modification should a material be owned by a neighbouring peptide or derivative model while retaining its keratin provenance?
- Which assay combinations permit reliable comparison of chain integrity, sulfur condition and assembly competence across native, extracted and recombinant preparations?
- Which preparation-specific stability and performance limits can research substantiate for the intended uses, without extrapolating from whole keratinous tissues?