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Peptide-oligonucleotide conjugates
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How do I write my peptide sequence termini?
The international nomenclature used for the sequence termini is as follows: - N-terminus: H means free amine (NH2-), Ac means acetyl [CH3C(O)-NH-], Pyr means pyroglutamic acid - C-terminus: OH means free acid (-COOH), NH2 means amide [-CONH2] - Modifications on the side chain of amino acids are d...
What methods do you recommend to conjugate a peptide to a carrier molecule?
The most important factor is to determine which end of the peptide should be conjugated to the carrier molecule. Once this has been determined, then there are a plethora of chemistries (linking agents) that can be used to conjugate the peptide to the carrier molecule. Maleimide-Thiol Linkage The ...
What should I do with the ends of my peptides, keep them free or block them?
We recommend that the N-terminal and C-terminal ends of the peptide mimic the protein of interest. That being said, if the peptide sequence is derived from a sequence within the protein, then both the end of the peptide should be blocked. We recommend that the N-terminal end be blocked with an Ac...
How long should a peptide that is going to be used as an antigen for antibody production be?
We usually use peptides that are 13 to 15 amino acids long in length, however shorter and longer peptides have been known to work. We have successfully raised anti-peptide antibodies to peptides that differ in the presence/absence of a single phosphate (our phospho-specific antibody programme). A...
Can you explain the M+Na and M+K mass peaks in MALDI spectra?
It is very common to see Na (sodium) and K (potassium) adducts in the MALDI spectrum. The sodium and potassium comes from the water used in the peptide solvents. Even distilled and deionized water has trace amounts of sodium and potassium ions, which can never be entirely removed. These become io...
What is Mass Spectrometry and why do we use it?
Mass spectrometry (MS) is an analytical tool used to determine the identity of molecules. In a typical MS procedure, a sample is ionized by bombarding the sample with a beam of electrons. The results are a plot of intensity as a function of the mass-to-charge ratio (m/z). These measurements can o...
How do you generally purify your peptides?
Our peptides are generally purified by reverse-phase preparative HPLC, using 2 buffers containing 0.1% trifluoroacetic acid (TFA). The first buffer (Buffer A) is composed of 0.1 % TFA in deionized water and the second buffer (Buffer B) is composed of 0.1 % TFA in acetonitrile (ACN). Generally, cr...
What is the difference between peptide content and peptide purity?
Peptide content is not an indication of the peptide purity as these are two separate measurements. Purity is determined by analytical HPLC and indicates the presence/absence of other peptidic contaminants (i.e. truncated peptides). Net peptide content determines the actual amount of the peptide (...
Do you synthesize isotope labeled peptides?
We can synthesize peptides containing non-radioactive atoms from commercially available building blocks. This includes amino acids containing 13C and/or 15N for Nuclear Magnetic Resonance (NMR) or Mass Spectrometry applications, just to name a few.
Do you synthesize 'wobble' (or degenerate) peptide libraries?
We can synthesize ‘wobble’ or degenerate peptides. As there are known differences in the incorporation rates of different amino acids, we can compensate for these rates to produce roughly equimolar amounts of each ‘wobble’ peptide.
How do you confirm a peptide is cyclized?
Generally, we can perform five types of cyclization reactions and these are shown below as: End to End [N-terminal to C-terminal] End to Side [N-terminal to a carboxylic acid from a side-chain residue] Side to End [Amine side-chain to C-terminal] Disulfide bridge cyclization Hydrocarbon-stapled p...
What spacer is there in a biotinylated peptide?
The standard biotin modification does not include a spacer. Spacers (PEG, X, etc.) are available on request. Please contact us for more guidance on the type of spacers that we offer.
How do I know if my peptide will be soluble?
The solubility of a peptide in a given solvent is dependent on the amino acid sequence and often hard to predict. In the case of catalog peptides, the solubility information is listed on the QC datasheet. For custom peptides, please see the section entitled "How should I solubilize my peptide".
How are the peptides supplied?
Peptides are shipped as lyophilized powder or oil at room temperature via an express courier. On request, we can also deliver your peptides in solution.
What quality control (QC) information do you provide?
Our QC datasheet for catalog peptides includes: Testing attributes (appearance, % peak area by analytical HPLC, identity by MS, and solubility) Test method Acceptance criteria QC results This information is listed on all of our QC datasheets and the raw data for each test can be provided upon req...
What type of chemistry do you use?
We utilize solid-phase Fmoc chemistry rather than BOC chemistry. Fmoc chemistry allows for the removal of protecting groups using mild conditions during peptide elongation, while BOC chemistry requires the use of a strong acid to remove the protecting groups during peptide elongation. Additionall...