S S symmetry Article Chiroptical Properties and Conformation of Four Lasiocepsin-Related Antimicrobial Peptides: Structural Role of Disulfide Bridges Markéta Pazderková 1,2,* ,Václav Profant 1, Petr Malo ˇn 1, Rina K. Dukor 3,Václav Ceˇrovskˇ ý 2 , Vladimír Baumruk 1 and Lucie Bednárová 2,* 1 Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, 121 16 Prague 2, Czech Republic;
[email protected]ff.cuni.cz (V.P.);
[email protected] (P.M.);
[email protected]ff.cuni.cz (V.B.) 2 Institute of Organic Chemistry and Biochemistry AS CR v.v.i., Fleming Square 2, 166 10 Prague 6, Czech Republic;
[email protected] 3 BioTools, Inc., 17546 Bee Line Highway, Jupiter, FL 33548, USA;
[email protected] * Correspondence:
[email protected]ff.cuni.cz (M.P.);
[email protected] (L.B.); Tel.: +420-220183593 (L.B.) Received: 17 April 2020; Accepted: 7 May 2020; Published: 13 May 2020 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.