Frequently Asked Questions about Solid Phase Peptide Synthesis (SPPS)
What is a safer alternative to HOBt and 6-Cl-HOBt?
OxymaPure® is an additive used in carbodiimide-mediated (DIC or EDC-HCl) reactions in the conversion of carboxylic acid to amide, with increased yield and decreased side reactions. It is a safer and more effective alternative to HOBt and has no transport restrictions. Vivitide is an official distributor of OxymaPure®. Read more about OxymaPure® here. Other alternatives to HOBt and 6-Cl-HOBt are HCTU or HATU. View all peptide synthesis reagents here.
Where can I find more information on CLEARTM Resins?
CLEAR (Cross-Linked Ethoxylate Acry- late Resins) was developed by George Barany and Maria Kempe at the University of Minnesota. These products retain the highly desirable solvation properties of polyethylene glycol (PEG) or of PEG-linked products but with greater convenience. Unlike resins for conventional liquid phase synthesis, CLEAR resin is a highly cross-linked solid support. It is produced in a bead form using a large-scale polymerization process developed at Vivitide. Read more about CLEAR resins here.
Do you carry a polymer-supported oxidant to help prepare disulfide bonds?
CLEAR-OXTM, is a polymer-supported oxidant, which combines the power of solid phase chemistry with the versatility of solution-phase reactions. CLEAR-OXTM is a highly effective, polymer-supported reagent for the formation of disulfide-bonds. CLEAR resin is the polymer of choice due to its compatibility with both aqueous and organic environments. A lysine-preformed cyclic Ellman’s reagent [5,5’-dithiobis(2-nitrobenzoic acid) = DTNB] is covalently attached to a CLEAR polymeric support with a β-alanine spacer to yield CLEAR-OXTM. Since the mechanism is based on peptide capture, sensitive residues such as Tyr, Trp, and Met are not affected, leading to increased purity and yield. These improved synthetic conditions allow for facile removal of the oxidant. Read more about CLEAR-OXTM and download resin conditioning and general methods here.
How do I choose an appropriate substitution for my resin of interest?
A Mesh is the number of square openings in a linear inch of screen or sieve. As the mesh number increases, the number of openings also increases while the size of the openings decreases. Therefore, larger mesh numbers correspond to smaller bead or particle sizes for a resin.
|
US Mesh |
Inches |
Microns |
Millimeters |
|
100 |
0.0059 |
149 |
0.149 |
|
120 |
0.0049 |
125 |
0.125 |
|
140 |
0.0041 |
105 |
0.105 |
|
170 |
0.0035 |
88 |
0.088 |
|
200 |
0.0029 |
74 |
0.074 |
|
230 |
0.0024 |
63 |
0.063 |
|
270 |
0.0021 |
53 |
0.053 |
|
325 |
0.0017 |
44 |
0.044 |
|
400 |
0.0015 |
37 |
0.037 |
What does the mesh number mean for a resin?
The higher the substitution, the greater the points of attachment points there are. However, higher substitutions can lead to decreased synthesis efficiency and cause aggregation with peptides containing long or difficult sequences. This is caused by increased steric hindrance that accompanies high density of peptide chains present in the matrix. Lower substitutions are also better to use for cyclizing linear peptides.
The substitution for resins is shown in the units, meq/g. How do you convert this to mmol/g an appropriate substitution for my resin of interest?
No conversion is required since meq/g is equivalent to mmol/g.