Modified peptides

Isogen Life Science offers a wide variety of chemical modification on its custom peptides. Here follows a brief description and the price of the offered modifications. Prices for modification depends on synthetic scale and peptide final purity. The listed prices should be added to the price of the peptide.

MAPS 4

Multiple Antigen Peptide System consists of a core of bifurcating Lysines (resembling a Christmas tree) on which 4 or 8 peptide copies are made growing starting from their C-terminal end. Literature data claim that Abs generation with such constructs, as alternative immunizing agents, might result equal to or better than the classical peptide-carrier protein conjugates. We provide custom synthesis only of MAPS 4 constructs that in our experience are giving end products homogeneous enough to be somehow characterized. Nevertheless, even in this case, analytical data are not very exciting: typical MALDI (mass spectra) signals and HPLC profiles are most of the time blob-like (gaussian shape). Longer the peptide sequence, less homogeneous the end product.
Suggested peptide length: equal to or shorter than 15 residues.

Peptide Cyclization

As widely recognized, the main uncertainty in the cyclization process concerns yields! In all cases the final amount of cyclized product would depend upon quantity of starting linear precursor, cyclization yields and degree of desired (achievable !) final purity. Depending upon peptide sequence and length the cyclization yields may vary from 0 up to > 50% depending upon proneness of the linear precursor to fold correctly as to bring in close spatial proximity the two ends that have to meet and to form the chemical bond. On the basis of a conservative estimate, starting from a given amount of linear precursor, a 5-20% overall yields, accounting for both cyclization and purification, should reasonably be expected in most cases. Thus, unless there are sounding/reliable data, either from literature and/or direct customer's experience, on the proneness of the linear precursor to cyclize, quotation would be made upon sequence inspection, according to the following:

• pre-defined quantity of highly purified, >95% whenever possible, linear precursor (cost defined by price/residue)
• fixed price for the cyclization (see below)

Standard suggested starting amount of linear precursor is 25 mg >95%, to end up with at least 1-5 mg of final purified cyclic compound. Were cyclization not to work, we would deliver 2-3 mg of linear precursor.

SPECIALS

Stable Isotopes

Custom Synthesis of peptides having in their sequence special amino acid derivatives bearing stable isotopes (²H, ¹³C, ¹⁵N) is also available.
Please submit your sequence and enquire for a customized quote.

Metal binding

Custom Synthesis of peptide conjugates in which a chelating agent (DOTA, DTPA, DTPAGlu, Porphyrins) is covalently linked to the peptide is also available. These conjugates are able to give very stable complexes of many metals or with radioactive isotopes of metals currently in use in Nuclear Medicine (¹¹¹In, ⁹⁰Y, ^99mTc, ¹⁷⁷Lu, ⁶⁸Ga).
Please ask for a customized quote.

Additional Services

• Conjugation of 3-5 mg of peptide to carrier protein (OVA, KLH, BSA)
• 3-5 mg of peptide bound to 0.5 g CNBr Sepharose
• Serum purification with immunoaffinity or protein A/G column