The cationic antimicrobial peptide CA14 with the sequence  CWGEAFSAGVHRLA was found to inhibit the growth of bacteria. The physical stability and secondary structure of CA14 were investigated in the presence of model membranes. The model membranes are composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-Dioleoyl-sn-glycero-3-phosphocholine (DOPC). Infrared (IR), dynamic light scattering (DLS), fluorescence, differential scanning calorimetry (DSC), and atomic force microscopy (AFM) techniques were employed. Infrared spectroscopy was used to examine changes in secondary structure content while AFM imaging was used to examine the morphological differences. DLS measurements were performed to monitor the aggregation process. IR spectra indicate that CA14  adopts a major α-helix structure in the absence of model membranes. An increase in β-sheet structure content of  CA14 is observed in the presence of model membranes. Interaction of CA14 with model membranes was examined using tryptophan and phenylalanine fluorescences. Upon addition of the model membranes, the initial fluorescence of CA14 is quenched. The decrease in fluorescence is selective for DPPC relative to other neutral phospholipid DOPC. Dynamic light scattering (DLS) data indicate that CA14 peptide has an influence on the size distribution of model membranes. In the presence of increasing amount of CA14, a disappearance of large vesicle aggregates was observed. AFM images show a significant change in the surface roughness level of DPPC and DOPC vesicles in the presence of CA14. DSC data indicate that the incorporation of CA14 greatly modifies the thermal stability of DPPC and DOPC

Aggregation properties of a short antimicrobial peptide in the presence of model membranes

251st National Meeting (2016)

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