Custom Peptides

Isca Biochemicals pay close attention to every step of the process involved in providing our customers with high quality peptides, from the earliest design stages through to synthesis, purification and analysis. We keep up with the literature to make sure that we are employing the best possible techniques to provide reliable custom peptides of the highest quality.

Use of highest quality reagents and solvents, together with close monitoring of synthetic steps, ensures that individual syntheses progress as efficiently as possible and that the final product is analysed to an appropriate specification to provide a peptide product that is suitable for the application for which it has been synthesised.

Our standard purities are >80% and >95%, although we are always happy to discuss purity with our customers to provide the most appropriate product for their needs.

We can routinely supply peptides of between 5mg and 1g, depending upon the number of amino acids and complexity of the desired amino acid sequence and are always willing to discuss the provision of multi-gram quantities.

MODIFICATIONS

Peptides are routinely provided as free N-terminal and C-terminal acid, although N-terminal acetylation and C-terminal amidation can be offered at no extra cost. Other modifications which can be offered include:

Acetylation and amidation.
Biotinylation can be offered as an N-terminal or lysine modification.
Conjugation to a range of carrier proteins suitable for antibody production.
Cyclisation can be offered either as a cysteine to cysteine disulfide bridge OR as head-to-tail or side chain bridge.
D-Amino Acids may be incorporated as individual residues or as a complete peptide.
Farnesylation of cysteine and sulfhydryl functionalities.
Fluorescent labelling employing a range of fluorescent reagents including fluoresceines, rhodamines, coumarins and many more.
Glycosylation of serine and threonine.
MAP multiple antigen peptides with a range of functionalities.
Methylation at the N-terminus or the mono- di- or tri-methylation of lysine side chains.
Myristoylation and addition of fatty acids of various lengths.
PEGylation of a wide variety of polyethylene glycol adducts.
Phosphorylation of tyrosine, threonine and serine.
Stable Isotope labelling can be arranged with the popular 13C and 15N cold labels.
Sulfation of tyrosine.

PURIFICATION

Peptides synthesised by Isca Biochemicals are subjected to the most exacting synthetic routes reducing, where possible, unwanted side reactions.


All of our peptides are purified by Reversed Phase High Performance Liquid Chromatography (HPLC), ion exchange chromatography or gel filtration techniques. Higher quality peptides (>95%) are subject to our most rigorous purification to ensure that they meet your specifications. Peptides of lower quality specification are always purified, so you can be sure that their quality is always as high as required.


ANALYSIS

HPLC
All peptides supplied by Isca Biochemicals are subject to Reversed Phase HPLC and, if appropriate, ion exchange chromatography. Purity is stated as area under the curve of the major peak when analysed at a specific wavelength, usually 230nm.

Mass Analysis
All peptides supplied by Isca Biochemicals are subject to mass analysis in order to provide confidence in the integrity of the supplied product. A copy of the mass analysis is always supplied as part of the datasheet delivered with the peptide.

Amino Acid Analysis
This technique can be provided as an additional service to give further confidence in peptide integrity, but is also a valuable tool to determine the nett peptide content of the product as supplied in freeze-dried form. All peptides, as supplied, will contain counter ions to charged functionalities within the peptide sequence. No guarantee of nett peptide content can be given for custom peptides, although experience suggests that the majority are >70%.


STORAGE AND HANDLING

Peptides will usually be supplied by Isca Biochemicals as freeze dried solid. They should be stored at -20°C or -80°C. Peptides should be stored in dark conditions and should be stored desiccated.

Solubility
Peptides should be reconstituted in sterile distilled water. A very small quantity of dilute ammonium hydroxide may be added to aid dissolution of peptides rich in acidic moieties, but note that this may facilitate unwanted cyclisation or disulfide bridge formation if cysteine is present in a peptide. A very small quantity of dilute acetic acid may be added to aid dissolution of peptides rich in basic moieties. If a sample of peptide will not dissolve in aqueous media, then the peptide should be dissolved in a minimal volume of dimethylsulfoxide (DMSO), followed by diluting the dissolved peptide into the buffer of choice to the desired concentration. Warming and sonication may aid dissolution, but may also accelerate unwanted cyclisation or degradation.  

Peptides are far less stable in solution than in lyophilised form. It is advisable to aliquot peptides into useful volumes to avoid freeze-thaw cycles, which may lead to peptide degradation.

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