Protein Expression Eukaryotic cells - CHO EGFP

Protein expression refers to the techniques in which a protein of interest is synthesized, modified or regulated in cells. The blueprints for proteins are stored in DNA which is then transcribed to produce messenger RNA (mRNA). mRNA is then translated into protein. In prokaryotes, this process of mRNA translation occurs simultaneously with mRNA transcription. In eukaryotes, these two processes occur at separate times and in separate cellular regions (transcription in nucleus and translation in the cytoplasm). Recombinant protein expression utilizes cellular machinery to generate proteins, instead of chemical synthesis of proteins as it is very complex. Proteins produced from such DNA templates are called recombinant proteins and DNA templates are simple to construct. Recombinant protein expression involves transfecting cells with a DNA vector that contains the template. The cultured cells can then transcribe and translate the desired protein. The cells can be lysed to extract the expressed protein for subsequent purification. Both prokaryotic and eukaryotic protein expression systems are widely used. The selection of the system depends on the type of protein, the requirements for functional activity and the desired yield. These expression systems include mammalian, insect, yeast, bacterial, algal and cell-free. Each of these has pros and cons. Mammalian expression systems can be used for transient or stable expression, with ultra high-yield protein expression. However, high yields are only possible in suspension cultures and more demanding culture conditions. Insect cultures are the same as mammalian, except that they can be used as both static and suspension cultures. These cultures also have demanding culture conditions and may also be time-consuming. Yeast cultures can produce eukaryotic proteins and are scalable, with minimum culture requirements. Yeast cultures may require growth culture optimization. Bacterial cultures are simple, scalable and low cost, but these may require protein-specific optimization and are not suitable for all mammalian proteins. Algal cultures are optimized for robust selection and expression, but these are less developed than other host platforms. Cell-free systems are open, free of any unnatural compounds, fast and simple. This system is, however, not optimal for scaling up.

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Found 2 matching solutions for this experiment

CpGrich

Yuansheng Yang, Bioprocessing Technology Institute, Agency for S

Upstream tips
CHO K1 cells (American Type Culture Collection, Manassas, VA) were cultured in tissue culture plates using Dulbecco’s modified Eagle’s medium (DMEM) + GlutaMaxTM (Life Technologies) supplemented with 10 % fetal bovine serum (FBS) (Sigma-Aldrich, St. Louis, MO). Cells were passaged every 3 to 4 days by diluting cells to 2 × 105 cells/mL. Cell density and viability were measured using the trypan blue exclusion method on a Vi-cell XR cell viability analyzer (Beckman Coulter, CA).
Protocol tips
Three separate transfections were performed using each promoter using the Nucleofector I system from Lonza (Cologne, Germany). 5 × 106 cells were transfected with 5 μg of linearized plasmids in each transfection. The transfected cells were transferred to 6-well tissue culture plates containing DMEM supplemented with 800 μg/mL of G418 (Sigma-Aldrich) for selection 24 h after transfection.
Downstream tips
Fluorescence-activated cell sorting (FACS) analysis was also performed using FACS Calibur (Becton Dickinson, Franklin Lakes, NJ) to determine the transient expression obtained using each promoter. Upon recovery of the stably transfected pools, at least nine clones were randomly selected from each stable pool by limiting dilution for a total of 30 clones to be carried forward for stability tracking.
CpGfree

Yuansheng Yang, Bioprocessing Technology Institute, Agency for S

Upstream tips
CHO K1 cells (American Type Culture Collection, Manassas, VA) were cultured in tissue culture plates using Dulbecco’s modified Eagle’s medium (DMEM) + GlutaMaxTM (Life Technologies) supplemented with 10 % fetal bovine serum (FBS) (Sigma-Aldrich, St. Louis, MO). Cells were passaged every 3 to 4 days by diluting cells to 2 × 105 cells/mL. Cell density and viability were measured using the trypan blue exclusion method on a Vi-cell XR cell viability analyzer (Beckman Coulter, CA).
Protocol tips
Three separate transfections were performed using each promoter using the Nucleofector I system from Lonza (Cologne, Germany). 5 × 106 cells were transfected with 5 μg of linearized plasmids in each transfection. The transfected cells were transferred to 6-well tissue culture plates containing DMEM supplemented with 800 μg/mL of G418 (Sigma-Aldrich) for selection 24 h after transfection.
Downstream tips
Fluorescence-activated cell sorting (FACS) analysis was also performed using FACS Calibur (Becton Dickinson, Franklin Lakes, NJ) to determine the transient expression obtained using each promoter. Upon recovery of the stably transfected pools, at least nine clones were randomly selected from each stable pool by limiting dilution for a total of 30 clones to be carried forward for stability tracking.
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