You design the protein.
We help you express it.
Turn your AI-designed candidates into proteins you can test, characterise and develop. Explore biotechrabbit RTS cell-free expression kits or work with our team on custom protein manufacturing.
The next breakthrough needs a real protein.
A model can propose a sequence, predict a fold or suggest an enzyme variant. The decisive questions emerge when that protein is made: Is it soluble? Does it bind? Does it catalyse the intended reaction? Does it remain active under the conditions that matter?
For companies developing proteins with AI, expression connects computational ambition with experimental evidence. A promising structure becomes a candidate for functional testing. A library of sequences becomes a set of proteins that can be compared. The resulting measurements can guide the next round of design.
biotechrabbit supports this step in two complementary ways: RTS kits put cell-free expression in your laboratory, while custom manufacturing services offer a route to outsourced protein production. Choose the approach that fits your team, your target and your next experiment.
Build your experimental workflow with RTS.
Use cell-free protein synthesis to explore candidates, compare constructs and prepare protein for functional or structural studies. Select from bacterial and eukaryotic expression systems.
Explore the kit portfolio →Give your protein a production partner.
Discuss custom production with biotechrabbit, from your target protein and required quantity to formulation and supply. Our manufacturing capabilities include expression in E. coli and eukaryotic cells.
Explore manufacturing services →Put cell-free expression to work for your designs.
RTS uses the protein synthesis machinery in cell lysates to express a target from a compatible DNA template outside living cells. For AI-driven protein engineering, this provides a practical way to investigate expression before committing to a cell-based production workflow. Selected RTS kits accept PCR-generated linear templates, allowing initial expression screening without cloning each candidate into a plasmid.
The RTS 100 E. coli HY Kit is a useful starting point for parallel screening. Its coupled transcription and translation reaction can produce up to 20 µg of protein in a 50 µl reaction in four hours. Both linear templates and plasmids can be used, giving teams flexibility as they move between exploratory constructs and established expression templates.1
A candidate sequence is the starting point.
Convert your design into an expression template with the regulatory elements required by the selected RTS system. Choose the lysate, template format and assay around the protein’s needs. Expression, solubility and activity remain target-dependent; suitable controls and, where necessary, purification help turn expression results into meaningful functional data.
When a candidate warrants more material, continuous-exchange cell-free (CECF) formats offer a route to higher yields. Their reaction and feeding compartments are separated by a semipermeable membrane, allowing exchange of small molecules during synthesis. The RTS 500 ProteoMaster E. coli HY Kit is designed for up to 6 mg of protein per reaction from plasmid templates; the RTS 9000 E. coli HY Kit offers up to 50 mg in a 10 ml reaction.2, 3 This opens a path from initial expression screening to more extensive characterisation.
Different designs. Different expression needs.
An engineered enzyme, a disulfide-rich binder and a membrane-associated protein can demand very different environments. The RTS portfolio gives you several starting points for selecting an expression strategy.
| RTS system | Where it fits | Explore |
|---|---|---|
| E. coli High Yield | Parallel expression screening with RTS 100; milligram-scale synthesis with RTS 500 ProteoMaster and RTS 9000 for follow-up studies. | View HY kits |
| E. coli Disulfide | Optimised conditions for functional proteins containing multiple disulfide bonds. RTS 100 and RTS 500 formats support different material requirements. | View Disulfide kits |
| Wheat Germ | A eukaryotic expression environment, including applications involving proteins dependent on eukaryotic chaperones. Screening and CECF formats are available. | View Wheat Germ kits |
| Insect Membrane | An option for membrane proteins and post-translationally modified eukaryotic proteins. Compatibility with the required modification and downstream assay should be assessed for each target. | View Insect Membrane kit |
Published yields are kit-specific upper values, not guaranteed yields for an individual design or purified protein recoveries. Consult the relevant product instructions for template requirements, reaction conditions and equipment.
Template preparation is part of the workflow, too. The RTS Linear Template Kit Plus supports the generation of multiple constructs for expression screening, with primer options for affinity tags and signal sequences. These tools can help you compare construct designs alongside the protein sequences themselves.7
Make the design cycle informative.
Producing a protein enables the experiments that distinguish an attractive prediction from a useful molecule. Depending on your application, that may mean measuring enzyme activity, comparing binding, assessing stability or preparing material for structural analysis. Expression yield and solubility also provide valuable information about which candidates deserve further investment.
Cell-free screening meets machine learning.
In a study published in ACS Synthetic Biology, Thornton and colleagues used cell-free protein synthesis to screen protease variants in a machine learning workflow. An initial set of 48 variants was followed by 32 more targeted variants, identifying proteins with improved kinetic properties.
The study illustrates how cell-free expression can support the collection of functional data for protein engineering. It is evidence for the approach, rather than a performance claim for biotechrabbit RTS kits.
Read the research →Real proteins. Measured function. Published results.
From engineered binders to active enzymes and plant proteins, researchers have used biotechrabbit RTS kits to answer questions that require experimental material. These studies show distinct capabilities of the platform and offer useful starting points for teams developing new protein sequences.
Selecting engineered binders against IL-9 receptor
RTS 100 E. coli HY Kit
Huličiak and colleagues used RTS to transcribe and translate combinatorial libraries of two protein scaffolds for ribosome display. Their workflow combined cell-free selection with competitive yeast display to identify soluble binders with improved specificity for the IL-9 receptor α-chain.
The best binder from one scaffold had a measured dissociation constant of 510 nM. RTS supported the ribosome-display stages; subsequent production and characterisation also used cell-based expression.
Why it matters: This is a concrete example of RTS supporting the experimental selection of engineered protein variants, a relevant capability for teams exploring new binders.
Read the binder selection study →Producing an enzyme for expanded protein chemistry
RTS 500 E. coli HY Kit
In a study developing orthogonal eukaryotic cell-free translation systems, the researchers used RTS to synthesise eAzFRS, an engineered tyrosyl-tRNA synthetase, and purified it through its Strep tag.
The purified enzyme was used as a component in CHO-based cell-free reactions investigating site-specific incorporation of a non-canonical amino acid into an adenosine receptor construct. The receptor experiments used CHO lysates, while RTS produced the engineered enzyme.
Why it matters: RTS can provide protein reagents that enable further engineering experiments, extending its role beyond production of the final target.
Read the orthogonal translation study →Taking soybean haemoglobin to milligram-scale investigation
RTS 500 ProteoMaster E. coli HY Kit
In a study of cell-free production of soybean leghemoglobins and nonsymbiotic haemoglobin, the authors used the RTS 500 system specifically for medium-scale synthesis of nonsymbiotic haemoglobin (nsHb).
The RTS reaction produced approximately 0.5 mg of target protein in 1 ml. The authors also reported purification losses and co-purifying proteins, identifying chromatography optimisation as an important next step.
Why it matters: The result demonstrates expression of a plant protein in a bacterial cell-free system and illustrates why production yield and purified recovery should be evaluated separately.
Read the soybean protein study →Making a fungal hydrolase for functional characterisation
RTS 100 Wheat Germ CECF Kit
Knauer and colleagues compared cell-free systems for synthesis of GH78 from Xylaria polymorpha. Their wheat germ experiments used the biotechrabbit RTS 100 Wheat Germ CECF system.
The wheat germ-produced enzyme showed α-L-rhamnosidase activity and was evaluated through kinetic and substrate-conversion measurements. The recombinant enzyme did not reproduce every activity of the native fungal protein, underlining the value of functional testing after expression.
Why it matters: RTS supported production of an active fungal enzyme for biochemical analysis, an instructive example for enzyme discovery and engineering.
Read the fungal enzyme study →These are independent research examples using biotechrabbit RTS products. They are not AI-design case studies or commissioned biotechrabbit manufacturing projects. Each study used its own constructs, conditions and downstream methods.
Your team designs the protein.
Let’s discuss how to produce it.
For AI companies seeking a production partner, biotechrabbit offers contract manufacturing of molecular biology proteins and antibodies at its Berlin production site. Capabilities include expression in E. coli and eukaryotic cells, with batch, continuous and high-density fermentation options.
Production shaped around your project
We work with customers on the development of enzymes, reagents and antibodies. Share the intended function, expression challenges and material requirements of your designed protein so we can assess a suitable production approach and define the project scope.
Supply shaped around your application
OEM options include bulk production, custom formulations, lyophilisation services and custom vialing, packaging and labelling, with quality certificates. Formulation and supply requirements can be discussed as part of your project.
RTS expression and contract manufacturing offer complementary routes. Use kits for your own experimental work, discuss outsourced production directly, or explore both as your programme develops. The manufacturing method, achievable quantity and deliverable specifications are agreed for the individual target.
Explore biotechrabbit OEM capabilities →Working on the biology behind better production.
Connecting computational models with protein production.
biotechrabbit was a consortium partner in LEANPROT, an international project developing a systems biology platform for lean-proteome E. coli strains. The project aimed to free cellular resources for recombinant protein production by identifying and removing proteins unnecessary under industrial cultivation conditions.
The approach combined metabolic modelling, proteomics-based characterisation and biological experiments, with plans to test production of recombinant proteins relevant to research, industry and diagnostics. It documents biotechrabbit’s involvement in research on production hosts, a key part of translating a protein sequence into a workable manufacturing process.
The public project description establishes biotechrabbit’s participation and the development objectives. It does not report a target-specific manufacturing outcome or a verified productivity improvement.
Explore the LEANPROT project →Bring us the protein you want to test.
Tell us about your candidate sequences, protein class, intended assay and required quantity. Include any known requirements for disulfide bonds, membrane association, modifications or formulation. We can help you choose an RTS starting point or discuss the feasibility of custom manufacturing.
Product information and further reading
- RTS 100 E. coli HY Kit: batch expression, template compatibility and published yield.
- RTS 500 ProteoMaster E. coli HY Kit: CECF expression from plasmid templates.
- RTS 9000 E. coli HY Kit: reaction format and published yield.
- E. coli Disulfide kits.
- Wheat Germ kits.
- Insect Membrane kit.
- Vectors and Linear Template kits.
- biotechrabbit OEM and contract manufacturing capabilities.
- Thornton EL, Boyle JT, Laohakunakorn N, Regan L. Cell-Free Protein Synthesis as a Method to Rapidly Screen Machine Learning-Generated Protease Variants. ACS Synthetic Biology (2025), 14(5), 1710–1718.
- Huličiak M et al. Combined in vitro and cell-based selection display method producing specific binders against IL-9 receptor in high yields. The FEBS Journal (2023). RTS use: Materials and methods, construction of mRNA-ribosome-scaffold complex.
- Cell Engineering and Cultivation of Chinese Hamster Ovary Cells for the Development of Orthogonal Eukaryotic Cell-free Translation Systems. Frontiers in Molecular Biosciences (2022), 9:832379. RTS use: Cell-free Protein Synthesis methods, preparation of eAzFRS.
- Cell-Free Production of Soybean Leghemoglobins and Nonsymbiotic Hemoglobin. ACS Synthetic Biology (2025), 14, 3445–3456. RTS use: medium-scale nsHb expression, results and section 4.3.
- Knauer JF et al. Cell-free production of the bifunctional glycoside hydrolase GH78 from Xylaria polymorpha. Enzyme and Microbial Technology (2022), 161:110110. RTS use: section 2.2; functional analyses: sections 3.3 and 3.4.
- ERASysAPP LEANPROT project description and consortium: biotechrabbit participation and research objectives.
Product information and research examples reviewed in October 2026. Refer to current product documentation when planning experiments.
