Characterizing Stability Conditions for Coiled-Coil Formation

In Nature, complex biopolymer molecules help form the basis of life. Proteins and polypeptides are made up of sequences of amino acids, which define the structure and function of the molecule. The primary sequence specificity and its associated assembly into higher ordered structures provides a framework for engineering of materials. One higher ordered structure is the coiled-coil motif, which has a variety of desired properties as a molecular building block. The coiled-coil can be designed to be tolerant to a variety of solution conditions and can be modified with a variety of chemical handles. Characterization of the thermodynamic properties that underlie the coiled-coil stability is critical for understanding when and how these motifs form and provide insight into more reliable peptide design. Here, the temperature dependent assembly/disassembly of peptides to form coiled coils are assessed over a range of solution conditions using circular dichroism (CD) spectroscopy. The effect of both peptide concentration in water and salt types of different concentrations on the melting temperature was assessed. For the computationally designed coiled-coil sequence that was selected, the melting temperature was found to be independent of coiled-coil concentration from 25 µM to 200 µM, while up to 70 mM concentrations of salts enhanced the melting temperatures. Future work includes the evaluation of salts over different valences as well as pH conditions.