Our scientists, with over 20 years of experience in molecular biology, protein expression, protein purification and structural/physicochemical characterization, will advance your project to match your exact needs from gene synthesis to fully characterized purified proteins using state-of-the-art instrumentation. With their wide technical expertise, our scientists can solve various protein expression and purification challenges.
We can optimize your antigens to improve immunoassay efficiency and reproducibility, adapt them to the desired throughput, multiplexing, or other innovative technologies, thus reducing overall cost. To further analyze particular aspects of the immune response, we also offer a service of antigen modifications (e.g. truncations, multimerization, mutations, etc.).
Vast protein and enzyme expertise, in particular:
- Amine transferases
- Cystein proteinases
- Viral, bacterial proteins
- Host cell contaminants
- Intracellular proteins
- Integral membrane proteins
- Native proteins
- Surface proteins
- Complex/multimeric proteins
- Hetero-oligomer proteins
- Particle-forming proteins (i.e. VLPs)
- Pseudoparticles (lentivirus)
- Various types of receptors
- Ion channels
Nexelis offers tailored recombinant DNA services according to your specific requirements, including gene synthesis with codon optimization, construct design, molecular cloning, mutagenesis, endotoxin-free plasmid isolation and DNA sequence verification. Other molecular biology techniques, such as qPCR, can be performed and adapted to your needs.
Your gene of interest can be synthesized, codon optimized and verified, to improve expression of your protein in prokaryote and eukaryote expression systems.
DNA Plasmid Production
Nexelis can prepare endotoxin-free plasmid DNA for sensitive cell culture experiments.
Nexelis provides construct design services, including subcloning your gene of interest into our appropriate vector for the expression system.
Nexelis can perform the real-time quantitative polymerase chain reaction (qPCR) to amplify and simultaneously detect, characterize and quantify nucleic acids in biological samples.
Site-directed mutagenesis to introduce point mutations, small insertions or deletions, into your protein with high accuracy and efficiency.
Our Protein Sciences experts use recombinant protein expression technology for protein production using recombinant DNA. To achieve the highest level of expression, the appropriate expression system is selected. The selection of the expression system is based on the protein type and properties, the need of post-translational modifications (PTM) and the protein yield and cost.
These expression systems include bacterial, insect, mammalian and yeast, in which protein expression parameters are optimized.
The E. coli expression system is one of the systems of choice to produce recombinant proteins since it is low cost, provides high expression level, ease of scaling, and has a short turnaround time. This type of system is mainly used to produce bacterial proteins.
When prokaryotic expression systems fail to generate correctly folded functional proteins or to express glycoproteins, a eukaryotic-based expression system should be considered.
Our team of scientists has developed both transient and stable expression platforms that utilizes HEK293 (human embryonic kidney) or CHO (Chinese hamster ovary) cells. Mammalian cell expression systems are ideal to produce post-translationally modified recombinant proteins for appropriate folding and biological activity of eukaryotic proteins. The mammalian cells can properly and efficiently recognize the signals for synthesis, processing and secretion of eukaryotic proteins.
The baculovirus expression vector system (BEVS) is a well-known eukaryotic system for the expression of recombinant proteins in insect cells. To express heterogeneous proteins, a recombinant baculovirus is generated by replacing one of its non-essential genes through a homologous recombination process with the recombinant gene coding for the protein of interest directly in Spodoptera frugiperda (Sf9). The recombinant proteins can be purified from infected cells or their supernatants and typically have appropriate folding, disulfide bond formation and oligomerization, resulting in production of proteins that are functionally similar to their native forms.
A yeast protein expression system is a simple, economical and highly efficient eukaryotic expression system. Both secretion and intracellular protein expression can be utilized. It enables partial post-translational modification and folding of eukaryotic proteins, while maintaining easy culture and scale-up production. The two most commonly used yeast strains for protein expression are Saccharomyces cerevisiae and Pichia pastoris.
Protein purification is the isolation of one protein from a complex mixture. Nexelis is proficient in a variety of chromatographic techniques and use state-of-the-art chromatography systems.
The Nexelis scientific team has extensive experience in the development and optimization of purification strategies using multiple chromatographic steps, such as:
- Affinity Chromatography
A chromatography method in which proteins with a known affinity are tagged to aid their purification from a biochemical mixture.
- Hydrophobic Chromatography
Proteins are separated according to their surface hydrophobicity in their native state.
- Size Exclusion Chromatography
A chromatography method in which proteins in solution are separated based on their size.
- Ion-Exchange Chromatography
Ion-exchange chromatography involves the separation of molecules based on their net charge under the given solvent conditions. This technique enables the separation of similar types of molecules by retardation on an anionic or cationic column by increasing the ionic strength of the mobile phase, or by changing the pH.
All purified proteins are delivered with:
- Protein concentration
- Percentage purity
- Optimized formulation to prevent protein from degradation or aggregation and ensuring long-term storage
- Custom aliquoting as specified by client
- Certificate of analysis
Purification of native proteins from natural sources can be challenging. The amount of the protein of interest tends to be quite small and contamination issues are inevitable. Moreover, protein can be unstable and there is no way to amplify the protein, except via enrichment. To enable successful purification, the intrinsic physical and chemical properties of the proteins must be understood and exploited to select the appropriate purification scheme in a logical way to maximize yield and minimize steps.
The Nexelis protein characterization platform provides a comprehensive range of high-quality analytical assays to ensure the identity, purity and physicochemical properties of the protein of interest. We perform several routine protein analyses throughout the project to ensure quality control and minimal batch-to-batch variability.
Identity and Purity
Nexelis utilizes both electrophoretic and liquid chromatographic instrumentation to provide you with information relating to the identity, homogeneity, and purity of your proteins.
Typical identity and purity analyses include:
- Western Blot
- SEC-HPLC (Size Exclusion Chromatography High-Performance Liquid Chromatography)
Nexelis can help you in understanding the structure and physicochemical properties of your protein of interest. In addition, we can determine the protein aggregation profile and the optimal storage conditions that should prevent aggregation and degradation, while maintaining protein functionalities of your sample with a variety of orthogonal analytical characterization techniques.
Typical studies for stability investigation include:
- Accelerated stability studies
- Stress testing (e.g. oxydation, temperature, shearing, etc.)
- Short- and long-term testing
- Protein freeze/thaw impact evaluation