Recombinant Human DHFR

Lyophilized powder can be adhered to the wall or cap of the tube due to external factors. Before opening, centrifuge the tube first, then collect the lyophilized powder to the tube bottom to avoid loss and waste.

After centrifugation, follow the manual to add redissolving buffer into the lyophilized powder and keep the protein concentration of 0.1 - 1mg/ml via gently pipetting instead of shaking with vortex mixer.

Lyophilized protein can be stably stored for one year at -20℃. The protein solution redissolved under sterile condition can be stored at controlled temperature for 3 months(-20℃--80℃) or one week(2 - 8℃).

Aliquot the prepared stock solution and refrigerate respectively to avoid the freeze - thawing induced inactivation during using the product.

Recombinant proteins can have the best activity with the spatial structure. During dissolution, it's suggested to gently pipet or inversely shake instead of rapidly shaking with vortex mixer.

Main reasons are listed below:

Genetic engineering modification: Recombinant proteins are obtained via genetic engineering technology which can modify or add amino acid sequence of proteins to change the molecular weight. The modification may include insertion, deletion or replacement of amino acid, resulting in the different molecular weight between recombinant and natural proteins.

Post - translational modification: Recombinant proteins may be subject to different post - translational modifications during expression, such as glycosylation, phosphorylation etc. These modifications can increase the molecular weight of proteins. In contrast, natural proteins may not be modified or the degree of modification is different. Thus, the molecular weight is different.

Changes in Purification: During purification, possible degradation or polymerization for recombinant proteins can cause the difference between final molecular weight and theoretical value. However, chemical or physical changes during natural protein extraction may not happen.

Different Expression Systems: Protein expression and modification modes depend on different expression systems(e.g. bacteria, yeast, mammalian cells etc.) This can result in the different molecular weight as well.

The activity of some cytokine and eukaryotic proteins is guaranteed. Due to limited conditions, the activity of other proteins is not tested and guaranteed.

Usually, cytokine proteins and proteins for cell culture remove endotoxin, which is specified in the basic product information. Customers’ request for removing endotoxin from the protein should be submitted in advance.

Most lyophilized protein powders consist of 10 mM Hepes, 150 mM NaCl with 5% trehalose and pH 7.4 lyophilized protein solution. Some proteins contain other components. For more details, please read the product manual.

Trehalose is a kind of non - reducing sugar and doesn't react with amino acid or proteins. Addition of trehalose stabilizes proteins to avoid freezing injury, and also keeps the protein more wet - resistant. Thus, the product can’t be precipitated easily during redissolution.

Please check protein product sheet or search for relevant protein information on our website.

Most FineTest recombinant proteins are lyophilized powders and delivered via ice pack. Only a small proportion of proteins are liquid and delivered via dry ice.

Not suggested. Follow the redissolving method in the manual. The offered buffer has been tested.

The species cross - activity of recombinant proteins depend on the product. It's suggested to choose the relevant species of recombinant proteins. If species can’t be matched, please refer to the following information:

1. Most human cytokines are efficient for mouse cells.(a few exceptions)
2. Most mouse cytokines are efficient for human cells. However, the specificity may not be strong. Such as: mouse EGF is active for human epidermal cell, and may be effective for other human cells.
3. Interferons, GM - CSF, IL - 3 and IL - 4 have species specificity. Recombinant human cytokines are only effective for human cells, except species like mouse and rat. Recombinant mouse cytokines are only applied in mouse, except human cells.
4. Fibroblast growth factors(FGFs), Neurotrophins(e.g. BDNF, GDNF, CNTF, β - NGF etc) and TGF - β are highly conserved. The cross - activity among species are strong.

FineTest can offer custom protein services like E.Coli, mammalian cell and insect cell expression system.