Chiroptical Properties and Conformation of Four Lasiocepsin-Related Antimicrobial Peptides: Structural Role of Disulfide Bridges

Abstract

We report an investigation of the role of disulfide bridges in the 27-residue antimicrobial peptide lasiocepsin (I) containing two disulfide groups (Cys8–Cys25, Cys17–Cys27) and three its analogs lacking one (II, III) or both (IV) native disulfides. Selective alternate incorporation of one or both disulfide bridges influences symmetry, conformation and biological properties of these peptides as demonstrated in their chiroptical (particularly Raman) properties. The effect of modifying the disulfide bridge pattern on the peptide secondary structure is investigated in water and in the presence of 2,2,2-trifluoroethanol and sodium dodecyl sulphate. A combination of experimental electronic and vibrational chiroptical data shows that both disulfide groups are necessary for stabilizing lasiocepsin secondary structure. While the Cys8–Cys25 disulfide group is important for sustaining lasiocepsin tertiary structure and maintaining its biological activity, the Cys17–Cys27 disulfide bridge has a supporting function consisting in reducing peptide flexibility.

Insights into thiram fungicide: A comparative study of solution and solid phases through Raman, DCDR, and SERS measurements and DFT simulations

“…A rule proposed in 1970s 39,40 states that Raman bands attributed to disulfide bond stretch motion, observed at ∼500, ∼520, and ∼540 cm −1 , should be assigned to three rotamers defined along the three successive bonds of the ‐C‐S‐S‐C‐ moiety, designated as g g g , g g t , and t g t . This rule fits well for diethyldisulfide 41–43 and is also utilized for Raman‐based assignment of S‐S bridges conformation in peptides, 44–46 although recent observations suggest that the situation is more complex and requires refinement of this basic rule 38,47 . Nevertheless, our DFT simulations (Figure 8) revealed a similar trend, with Raman bands corresponding to the ν(S‐S) vibration of g g g , g g t , and t g t conformers found at ∼390, ∼470, and ∼540 cm −1 , respectively (∼410, ∼495, and ∼565 cm −1 if a scaling factor of 1.05 is employed).…”