Secondary Structural Preferences of Some Antibacterial Cyclooctapeptides in the Presence of Calcium(II)

Table 1

HPLC and mass spectrometry data of the synthesized cyclopeptides (COP4–9).

Test peptides		Retention time; (min)	ESI-MS; (𝑚/𝑧); [M]^+
COP 4	c[D-Leu-Leu-D-Leu-Lys-D-Lys-Lys-D-Lys-Glu]	15.2	981.68 (981.27)^a
COP 5	c[D-Leu-Leu-D-Leu-His-D-Lys-Lys-D-Lys-Glu]	15.4	990.68 (990.24)
COP 6	c[D-Leu-Leu-D-Leu-Cys-D-Lys-Lys-D-Lys-Glu]	18.2	956.61 (956.24)
COP 7	c[D-Leu-Leu-D-Leu-Leu-D-Lys-Lys-D-Lys-Glu]	20.2	966.88 (966.26)
COP 8	c[D-Leu-Leu-D-Leu-His-D-Lys-His-D-Lys-Glu]	15.1	999.80 (999.21)
COP 9	c[D-Leu-Leu-D-Leu-Glu-D-Lys-Lys-D-Lys-Glu]	16.8	982.80 (982.23)

^aCalculated [M]⁺ values are shown in parenthesis.