Annexin V CF® Dye Conjugates, Azide-Free, Lyophilized

MTT and XTT are colorimetric based assays, while resazurin can be measured using colorimetric or fluorescence detection. MTT is not a soluble product, so the cells must be lysed to solubilize the formazan salt before absorbance can be measured. XTT and resazurin do not require cell lysis, allowing kinetic monitoring of the same samples at different timepoints.

Category: Apoptosis, Necrosis, and Cell Viability Kits

Check to make sure your cell densities are in the linear range of the cell viability assay. Too few cells may fall below the limit of detection, and too many cells may saturate the OD. Perform an initial experiment to check the best linear range for your cell type and experimental set-up. You may need to vary the cell density assay incubation time. The kit protocols provide general guidelines and may need to be optimized for your experimental system.

Category: Apoptosis, Necrosis, and Cell Viability Kits

Resazurin is reduced by cells to the fluorescent product resorufin. Resorufin can be reduced further to a non-fluorescent compound. Therefore the densest wells may have lowest fluorescence due to over-reduction of the substrate. Please see the product information sheet for more details. The kit protocol provides general guidelines and may need to be optimized empirically for your experimental system. You may need to vary cell density or assay incubation time to ensure that your samples fall in the linear range of the kit.

Category: Apoptosis, Necrosis, and Cell Viability Kits

Coelenterazines are predominantly yellow solids, but may contain dark red or brown flecks. This does not affect product stability or performance. If your coelenterazine is uniformly brown, then it is oxidized and needs to be replaced.

Category: Luciferase Assays, Product shipping, storage, shelf life, & solubility

Bioscience kits
The guaranteed shelf life from date of receipt for bioscience kits is listed on the product information sheet. Some kits have an expiration date printed on the kit box label, this is the guaranteed shelf life date calculated from the day that the product shipped from our facility. Kits often are functional for significantly longer than the guaranteed shelf life. If you have an older kit in storage that you wish to use, we recommend performing a small scale positive control experiment to confirm that the kit still works for your application before processing a large number of samples or precious samples.

Antibodies and other conjugates
The guaranteed shelf life from date of receipt for antibodies and conjugates is listed on the product information sheet. Antibodies and other conjugates often are functional for significantly longer than the guaranteed shelf life. If you have an older conjugate in storage that you wish to use, we recommend performing a small scale positive control experiment to confirm that the product still works for your application before processing a large number of samples or precious samples.

For lyophilized antibodies, we recommend reconstituting the antibody with glycerol and antimicrobial preservative like sodium azide for the longest shelf life (note that sodium azide is not compatible with HRP-conjugates).

Chemicals, dyes, and gel stains
Biotium guarantees the stability of chemicals, dyes, and gel stains for at least a year from the date you receive the product. However, the majority of these products are highly stable for many years, as long as they are stored as recommended. Storage conditions can be found on the product information sheet or product safety and data sheet, material safety data sheet, and on the product label. Fluorescent compounds should be protected from light for long term storage.

If you have a Biotium compound that has been in storage for longer than one year that you wish to use, we recommend performing a small scale positive control experiment to confirm that the compound still works for your application before processing a large number of samples or precious samples.

Expiration date based on date of manufacture (DOM)
If your institution requires you to document expiration date based on date of manufacture for reagents, please contact techsupport@biotium.com for assistance.

Chemical products with special stability considerations:

Esters

Ester compounds include the following:
• Succinimidyl esters (SE, also known as NHS esters), such as our amine-reactive dyes
• Acetoxymethyl esters (AM esters) such as our membrane-permeable ion indicator dyes
• Diacetate-modified dyes, like ViaFluor™ 405, CFDA, and CFDA-SE cell viability/cell proliferation dyes

Ester dyes are stable in solid form as long as they are protected from light and moisture. Esters are not stable in aqueous solution. Concentrated stock solutions should be prepared in anhydrous DMSO (see Biotium catalog no. 90082). Stock solutions in anhydrous DMSO can be stored desiccated at -20°C for one month or longer. Esters should be diluted in aqueous solution immediately before use. Succinimidyl esters (SE) should be dissolved in a solution that is free of amine-containing compounds like Tris, glycine, or protein, which will react with the SE functional group. AM esters and diacetate compounds should be dissolved in a solution that is free of serum, because serum could contain esterases that would hydrolyze the compound.

A note on CF™ dye succinimidyl ester stability
Succinimidyl esters are generally susceptible to hydrolysis, which can result in lower labeling efficiency. Heavily sulfonated dyes, such as the Alexa Fluor® dyes, DyLight® dyes and IRDyes® are particularly hygroscopic, worsening the hydrolysis problem. For example, the percent of active Alexa Fluor® 488 succinimidyl ester (SE) could be well below 50% by the time of application (according to the manufacturer’s product datasheet). In a number of Alexa Fluor® SE reactive dyes, the SE group is derived from an aromatic carboxylic acid, while in all of Biotium’s CF™ dyes the SE group is prepared from an aliphatic carboxylic acid. This structural difference reduces the susceptibility of CF™ dye SE reactive groups to hydrolysis, resulting in relatively stable reactive dyes with consistently higher labeling efficiency compared to other SE derivatives of other fluorescent dyes.

Maleimides, MTS and thiosulfate dyes
Like the succinimidyl ester dyes, these dyes are also susceptible to hydrolysis, although generally to a much lower degree. Thus, for long term storage, anhydrous DMSO is recommended for making stock solutions.

Other reactive dyes
Amines, aminooxy (also known as oxylamine), hydrazide, azide, alkyne, BCN, and tyramide reactive dyes, as well as dye free acids, are generally stable in aqueous solution when stored at -20°C for 6-12 months or longer, as long as no compounds are present that may react with the dye’s functional group. See the product information sheets for specific reactive dyes more information.

Coelenterazines and D-luciferin

Coelenterazines are stable in solid form when stored as recommended; they are not stable in aqueous solution. Concentrated coelenterazine stock solutions (typically 1-100 mg/mL) should be prepared in ethanol or methanol; do not use DMSO or DMF to dissolve coelenterazines, because these solvents will oxidize the compounds. Ethanol or methanol stocks of coelenterazine can be stored at -20°C or below for six months or longer; alcohol stocks may evaporate during storage, so use tightly sealing screw cap vials and wrap the vials with Parafilm for long term storage. Propylene glycol also can be used as a solvent to minimize evaporation. If the solvent evaporates, the coelenterazine will still be present in the vial, so note the volume in the vial prior to storage so that you can adjust the solvent volume to correct for evaporation if needed. Prepare working solutions in aqueous buffers immediately before use. Coelenterazines are stable for up to five hours in aqueous solution.

Aquaphile™ coelenterazines are water soluble formulations of coelenterazines. They are stable in solid form when stored as recommended. Aquaphile™ coelenterazines should be dissolved in aqueous solution immediately before use. They are stable for up to five hours in aqueous solution.

Note that coelenterazines are predominantly yellow solids, but may contain dark red or brown flecks. This does not affect product stability or performance. If your coelenterazine is uniformly brown, then it is oxidized and needs to be replaced.

D-luciferin is stable in solid form and as a concentrated stock solution when stored as recommended; it is not stable at dilute working concentrations in aqueous solution. Prepare concentrated D-luciferin stock solutions (typically 1-100 mg/mL) in water, and store in aliquots at -20°C or below for six months or longer. Prepare working solutions immediately before use.

Category: NucView® Caspase-3 Enzyme Substrates, Mix-n-Stain™ Antibody Labeling Kits, DNA Quantitation Kits, Luciferase Assays, CF® Dyes, Product shipping, storage, shelf life, & solubility

The storage conditions that a Biotium label recommends are deliberately conservative. Long term storage at low temperatures usually will increase the time that the product will remain within specification, unless specific instructions otherwise are provided (such as “do not refrigerate” or “do not freeze”).

Biotium labels and product information sheets may show a specific temperature for long term storage, or a temperature range that is adequate for long term storage. For all products, the implied range is as follows for the following storage conditions:

• Room Temperature
  For Biotium products where the label indicates room temperature or RT, this implies storage in ambient conditions between 20°C and 30°C.

• Refrigerator
  For Biotium products where the label indicates 4°C, this implies storage in a refrigerator that is between 2°C and 8°C.

• Freezer
  For Biotium products where the label indicates -20°C, this implies storage in a freezer that is between -35°C and -5°C.

• Ultra Low Temperature Freezer
  For Biotium products where the label indicates -70°C, this implies storage in an ultra low-temperature (ULT) freezer that is below -60°C.

Category: Product shipping, storage, shelf life, & solubility