Technical Support Frequently Asked Questions
If your inquiry is not addressed in this FAQ section, please contact:
US: technicalsupport@tocrisusa.com
UK: technicalsupport@tocris.co.uk
Catalogue Entry Information
Chemical Abstracts Registry (CAS) numbers
The Chemical Abstracts Service (CAS) number is a unique identification code assigned to a chemical substance by the American Chemical Society. While these are given as accurately as possible they may not reflect the salt or level of hydration of the product supplied.
Stereochemistry
Where specific stereochemistry is indicated in a diagram, the product is supplied in the conformation shown. When products are supplied as mixtures of stereoisomers, for clarity only one form is shown. The existence of both enantiomers in a product is indicated by the notation ‘and enantiomer’.
Batch numbers
Batch numbers can be found at the top of the product data sheet, or on the vial label, as a 1, 2 or 3 digit number, to the left of a letter. The numbers to the right of this letter are for internal use only. For example, in the case 15A/466444, 15 identifies the batch number.
Molecular weights
The molecular weight displayed in the catalogue and website represents the product as shown by the chemical structure.
During manufacture it is common for water of hydration to be incorporated with the product. The degree to which this occurs can vary from batch to batch and as a consequence the molecular weight of the material supplied can change. Additionally, we may add or change a salt from that stated in the catalogue. Any change is clearly stated on the vial labels and accompanying product datasheets; any variation should not affect the basic pharmacological properties of the compound. Consequently solutions should only be made up using the molecular weight as stated on the product datasheets and vial labels.
Weighing accuracies
The quantity of compound supplied in our vials is not weighed to the accuracy required for direct solution preparation unless specifically stated on the product datasheet. It is the responsibility of the individual researcher to accurately reweigh the compound in order to obtain solutions of defined concentration.
[top]
Product Appearance
Empty vials
Some products, especially those sold in small quantities and/or lyophilized, are transparent. This can make the product appear as a clear, thin film on the bottom and walls of the vial and may not be readily visible without careful scrutiny.
[top]
Solubility
Stock solutions
Stock solutions should be made up using the molecular weight of the product as stated on the vial label (the same figure is on the accompanying product datasheet).
The Tocris Molarity Calculator is a useful tool to help you make up stock solutions.
Solubility information
Solubility information for any product can be found on our website and the product datasheet.
Making solutions as molar equivalents
Aqueous solutions of some amino acids can be difficult to achieve, so a common technique is to use 1 molar equivalent (1eq.) of sodium hydroxide (NaOH) as a solubility aid.
We generally recommend that a 100 mM sodium hydroxide solution is used to dissolve the active compound.
Take the molecular weight (M.W.) of the compound as detailed on the vial label and data sheet and calculate the amount in grams (M.W./10) is required to form a 100 mM solution when 1L solvent is added (X). From this, calculate the amount in grams required to form a 100 mM solution when 1 ml solvent is added (X/1000). 1 ml of the NaOH stock solution prepared above can now be added to this weight to dissolve the compound. In some cases warming of the solution or sonication may aid solubilisation.
Below is a working example:
Glutamic acid (Catalogue Number 0217)
M.W.: 147.13
For 100 mM solution: M.W./10 = 14.7 g in 1L
For amount needed to make 1 ml of a 100 mM solution:
14.7/1000 = 14.7 x 10-3 g in 1 ml
= 14.7 mg in 1 ml
Weigh 14.7 mg glutamic acid
add 1 ml NaOH (100 mM)
= 1 ml of a 100 mM solution of glutamic acid in 1eq. NaOH
This solution can then be further diluted (with water) to the required concentration.
Peptide solubility
Most peptides are soluble in distilled water. If they do not completely dissolve, the addition of 1.0 M acetic acid for basic peptides (those containing Arg, Lys, His), or 1.0 M ammonium hydroxide for acidic peptides (those containing Asp, Glu) may help. Solubilization of extremely insoluble peptides can be assisted with 10% DMSO or DMF, although the use of these may interfere with some biological assays. Sonication can also be a useful aid. It is recommended that the peptide be dissolved to the highest possible concentration and then diluted with water or buffer to the working concentration. Buffer should only be added when the peptide is completely dissolved as salts may otherwise cause aggregation.
Tocriset solubility
Detailed solubility instructions, including suitable solvents, are provided in the Tocriset booklet. This can also be downloaded as a PDF.
Tocriset stock solutions
Each Tocriset has been designed so that 0.5 or 1 ml of a solvent can be added directly to each vial to produce a stock solution of 10 or 5 mM, respectively.
[top]
Purity
Bioactive chemical purity
Tocris bioactive chemicals are of high purity, typically > 98%. For purity of an individual product please consult the Certificate of Analysis (COA).
Peptide purity
Unless otherwise stated, peptides supplied by Tocris have a purity of > 95%. For purity of an individual product please consult the Certificate of Analysis (COA).
Product sterility
Tocris products are not weighed out under sterile conditions, and should not be treated as such. If required, sterile solutions can be prepared by subsequent filtration.
Quality control
Chemical purity is assessed using an array of techniques including HPLC, chiral HPLC, NMR, microanalysis, high voltage electrophoresis, melting point, optical rotation, TLC and mass spectrometry. Please see the individual product Certificate of Analysis for details. In all cases we believe that the purity of any material supplied by Tocris will match or exceed the purity of the product originally reported in the scientific literature.
[top]
Stability and Storage
Bioactive chemical stability and storage
Due to the novelty of many of our products, information concerning product stability has rarely been reported and in most cases we can only offer a general guide. Our standard storage recommendations are as follows:
Solid: Provided storage is as stated on the product vial and the vial is kept tightly sealed, the product can be stored for up to 6 months.
Solution: We recommend that stock solutions, once prepared, are stored as aliquots in tightly sealed vials at -20°C. Generally, these will be useable for up to one month. Wherever possible, solutions should be made up and used on the same day. Before use, and prior to opening the vial, it is recommended that the product be allowed to stand at room temperature for at least 60 minutes.
|
In all cases refer to the datasheet as conditions vary for different products.
Antibody stability and storage
Antibodies should be stored at -20°C. Avoid storage in a frost-free freezer, as changes in moisture and temperature may affect stability. Stored under these conditions, the antibody will be stable for 6 months. To aliquot the antibody, to ensure maximum recovery we suggest the following: block the new vials by filling with a solution of sterile 10% w/v Bovine Serum Albumin (BSA) for a minute, aspirate and then aliquot the antibody. Note that all our affinity-purified antibodies are supplied in buffer containing freeze-thaw protectants, which should remove the requirement for aliquoting.
Tocrisolve stability and storage
Tocrisolve products must not be stored at -20°C as freezing has an adverse effect on the stability of the formulation. Provided that the vial is kept tightly sealed, protected from exposure to light and stored at +4°C, the product should be stable for 1 month from the date of despatch.
Peptide stability and storage
Peptides are provided in lyophilized form and should be stored dessicated at -20°C. Long-term storage of peptides in solution is not recommended.
Short periods of high temperature
Short periods at higher temperatures than recommended (periods < 1 week), such as can occur during shipping, will not significantly affect product life or efficacy.
[top]
Safety
Safety information
Every possible precaution should be taken when handling, using, storing or disposing of any research chemical supplied by Tocris. We will, so far as we are able, provide all possible advice and assistance to customers concerning the safe handling of our products. As research chemicals, the potential hazards are often not known and an absence of warning does not mean that no hazard exists. It is the users’ responsibility to ensure that relevant safety precautions are taken at all times.
Product Material Safety Datasheets are supplied with all products and contain information relating to their safe handing. Additional copies are readily available on our website and from Technical Support.
Ampoule/glass vial opening instructions
The majority of our products are supplied in glass vials with a screw top lid. During transit, material may accumulate in the vial top. This can be dislodged by gently tapping the vial before opening. In contrast, some of our products are shipped in glass ampoules – caution must be exercised when opening these. We recommend wearing gloves and safety goggles. To open, cover the ampoule with a cloth and place thumbs on score line; apply gentle pressure away from the body and snap the vial open. Products classified as very toxic are supplied in screw top bio-tubes.
Product use
All our products are intended for laboratory use only. They must not under any circumstances be used for human, drug, food, cosmetic, agricultural, domestic or any purpose. They should only be used by trained scientists working under controlled conditions who are familiar with the potential hazards.
[top]
Material Safety Datasheets (MSDS) and Certificates of Analysis (COA)
Material Safety Datasheets (MSDS) and Certificates of Analysis (COA)
Copies of the Product Material Safety Datasheets (MSDS) and Certificates of Analysis (COA) are included with each individual product when shipped. They are also available on-line, to find them locate the relevant product information page. The default MSDS and COA is always for the batch currently on sale, to view earlier batches simply select from the drop down box.
[top]
Antibodies
Antibody shipping
Antibodies are shipped in polystyrene igloos with refrigerant appropriate for the prevailing climate. Due to the temperature-sensitive nature of antibodies, special processing, shipping and packaging is required and, as such, additional costs may be incurred. Depending on the destination, restrictions may apply to the day we are able to dispatch. Please contact the Customer Service Department for details.
Blocking peptides
Subject to availability, Tocris will endeavour to provide a sample of blocking peptide with each antibody supplied. Blocking peptides may also be purchased separately.
Blocking peptide use
It is recommended that the blocking peptide is used at 100-500 fold molar excess to antibody.
|
Step 1
First calculate the antibody’s approximate molarity using the optimal working dilution for Western immunoblot analysis (typically 0.5 – 2 μg/ml) and an average IgG molecular weight of 150000 Da.:
| Antibody molarity |
(M) = μg (amount of antibody) |
|
150000 (average molecular weight of antibody) |
Secondly, to calculate the amount of blocking peptide (μg) required, multiply the antibody molarity by the following:
x 2 (peptide binding sites per antibody)
x 200 (fold excess peptide)
x peptide molecular weight (from product datasheet)
Example: For an antibody with optimal working concentration of 0.5 μg/ml in a final volume of 10 ml, calculate the amount of blocking peptide (molecular weight 2345) required at 200-fold excess.
Solution:
| 5 μg |
x 2 x 200 x 2345 |
|
| 150000 |
|
= 31.3 μg blocking peptide |
Step 2
Dilute primary antibody in 100 μl of appropriate buffer containing the amount of blocking peptide as calculated above. Incubate with gentle agitation overnight at 4°C.
Step 3
Adjust volume of antibody/blocking peptide mixture to 10 ml with appropriate buffer and analyze by Western Immunoblotting following the standard protocol.
|
Antibody incubation
Many protocols incubate antibodies for 1 hour at 37°C to save time. However, we recommend an overnight incubation at 4°C to help prolong the antibody and antigen interaction and obtain an optimal signal to noise ratio. Low temperature incubations can also minimize problems with lower affinity antibodies such as those discriminating between phosphorylated and unphosphorylated forms of the target protein.
Bovine Serum Albumin (BSA)
Tocris antibodies do not posses any risk of livestock disease. The glycerol used as a freeze-thaw protectant is synthetic and most of our antibody buffers contain Trehelose rather than BSA as a stabilizing agent. Where BSA is used in a buffer, it has been sourced from countries certified as free from prion disease.
Sodium azide
Sodium azide is added to Tocris antibodies to aid long-term storage of antibodies. Sodium azide however, strongly inhibits horseradish peroxidase based detection systems. We therefore do not recommend the inclusion of sodium azide in working buffers but suggest that solutions are appropriately sterilized by either filtration through a 0.2 micron filter or autoclaved. Where horseradish peroxidase based detection systems are being used, we recommend that membranes are washed throughly prior to detection to remove any residual traces of sodium azide.
Antibody applications
Our antibodies have been tested by Western immunoblotting as a standard part of our QC procedures. However, we do not routinely check them for other applications due to the number of variables involved. We are always delighted to hear of new applications for our antibodies.
Cross-reactivity
Antibodies are assessed for species cross-reactivity between human, rat and mouse tissues and this are stated in the catalogue and datasheet entries. For alternative species we suggest the use of a protein-protein (Blastp) Blast Search [www.ncbi.nih.gov/BLAST/] to compare the protein sequence homology between the peptide sequence used in raising the antibody and the alternative species protein sequence. Although all our antibodies are affinity purified against the original peptide sequence, some cross-reactivity against proteins differing by only one or two amino acid residues within the overlapping region can be expected. We cannot guarantee that the antibody will recognize the alternative protein sequence. If the antibody does not initially recognize the alternative protein sequence we suggest removing the Tween20 detergent from all buffers and extending the 4°C incubation period to maximize potential binding.
[top]
Tocrisolve
Tocrisolve
Tocrisolve 100 is a formulation composed of a 1:4 ratio of soya oil/water which is emulsified with the block co-polymer, Pluronic F68. Lipids in Tocrisolve can be conveniently diluted with any aqueous medium for further use. Each Tocrisolve 100 product is supplied with a 1 ml sample of the plain emulsion Tocrisolve 100 (Cat. No. 1684) for use as a negative control.
[top]
New Product Suggestions
New Product Suggestions
We welcome suggestions for new products. Please complete your product requirements and we will contact you shortly.
[top]
|
