Naresh Dhanasekar

• In this thesis, we investigated two different subjects: Firstly, we studied the permeation of peptides and a fluoroquinolone antibiotic namely, ciprofloxacin across the major channel of Campylobacter jejuni (C. jejuni). Secondly, we studied the gating properties of another complex porin from Pseudomonas aeruginosa (P. aeruginosa). In-vitro single channel measurements were utilized to understand the permeation of peptide and antibiotics. However, in addition to electrophysiology, molecular simulations were also performed to better understand the gating properties of the porin from P. aeruginosa. With respect to the transport properties of porin, in the second chapter, we studied the translocation of short cationic peptides across the major outer membrane protein (MOMP) channel from C. jejuni. Basic single channel properties such as ion-conductance and selectivity were reported. Furthermore, to understand the transport properties, short cationic peptides were used. Voltage dependent transport properties of peptides through MOMP was reported.In Chapter 2.2, we studied the translocation of ciprofloxacin across the MOMP channel. Interestingly, we studied the single channel properties of two different variants of MOMP namely the MOMP purified from C. jejuni (nMOMP) and the heterologously expressed in E. coli (rMOMP). The channel was further tested with the divalent cation, Ca2+. The presence of Ca2+, has influenced the binding kinetics across the MOMP channel of Campylobacter.In the third chapter (Annexe, Manuscript in preparation) we made a detailed study in the gating properties of OccK5 porin of P. aeruginosa. The gating transitions were analysed in all environmental conditions such as pH and ion-concentration. In addition, we report a single point mutation (Gln) can drastically modulate the gating scheme of the channel.