Peptides, by nature, are composed of amino acids with potentially ionizable chemical moieties. The ionization state of any of these moieties can significantly impact the peptide’s chromatographic behavior, both in terms of peak shape and retention by the solid support. Peptide purification by reversed-phase chromatography, however, almost exclusively includes an acidic additive to the mobile phase solvents, maintaining the solution at a pH of 2-3 throughout the purification cycle. But have you ever considered trying an alternative additive in the mobile phase to improve your purification results?
Mass-directed purification, whether with a preparative HPLC or a bench-top flash system, is quickly gaining interest in the peptide purification space. The simple fact is that using a specific mass, rather that UV absorbance, to trigger fraction collection allows for greater confidence in the identity of the collected fraction. Importantly though, this technique can also reduce your time required for purification, by significantly reducing or even eliminating the need for secondary mass analysis of each collected fraction.
Ion pairing agents are used in a variety of strategies to improve overall purification efficiency. In a previous post, I utilized ion pairing agents to increase the peptide’s hydrophobicity, improving retention by the stationary phase and enabling purification. But what other strategies can be improved by using ion pairing agents?
In this post, I’ll utilize ion pairing agents to enable rapid peptide purification by flash chromatography. The use of ion pairing agents can in fact alter the peptide’s apparent hydrophobicity sufficiently that the desired peptide and it’s closely eluting impurities can be resolved. The question is, which one to choose?
Recently there has been substantial motivation to consider and evaluate alternative, more environmentally friendly solvents. Some countries have even gone so far as to ban some of the more toxic, yet commonly used solvents. In addition to general toxicity, additional consideration in the green chemistry movement is the volume of solvent used in any particular application. In this regard, purification solvent selection is closely monitored as they are often used in large quantities.
In peptide purification, sample loading onto the column is rarely considered. Most, if not all, HPLC instruments come equipped with a sample injection loop which demands a liquid injection of the sample for purification. If you decide to use flash chromatography to purify your peptides though, liquid injection is no longer the exclusive method for sample introduction to the column. Alternatively, dry loading crude material is a strategy often used in small molecule purification, particularly when sample solubility concerns arise.
Chemical synthesis of peptides, and even proteins, offers the possibility to expand the functionality and stability imbued by nature. However, chemical synthesis of very long peptides and small proteins remains today an exceedingly difficult task. Several ligation strategies have been developed that help to alleviate this challenge. These strategies though, require a purified, yet fully protected peptide fragment.
In today’s post I’ll answer the above question by comparing the crude purity of peptides synthesized using amino acid stock solutions or freshly dissolved amino acids.
Our seasoned peptide chemist Dr. Elizabeth Denton has tried it all when it comes to peptides. In this short video she shows that using DMSO (dimethyl sulfoxide) in a peptide synthesis workflow is perfectly fine together with the Biotage® V-10 Touch evaporator. Watch her evaporate it in just over eight minutes.