Prediction of Antibacterial Activity from Physicochemical Properties of Antimicrobial Peptides

Consensus is gathering that antimicrobial peptides that exert their antibacterial action at the membrane level must reach a local concentration threshold to become active. Studies of peptide interaction with model membranes do identify such disruptive thresholds but demonstrations of the possible correlation of these with the in vivo onset of activity have only recently been proposed. In addition, such thresholds observed in model membranes occur at local peptide concentrations close to full membrane coverage. In this work we fully develop an interaction model of antimicrobial peptides with biological membranes; by exploring the consequences of the underlying partition formalism we arrive at a relationship that provides antibacterial activity prediction from two biophysical parameters: the affinity of the peptide to the membrane and the critical bound peptide to lipid ratio. A straightforward and robust method to implement this relationship, with potential application to high-throughput screening approaches, is presented and tested. In addition, disruptive thresholds in model membranes and the onset of antibacterial peptide activity are shown to occur over the same range of locally bound peptide concentrations (10 to 100 mM), which conciliates the two types of observations

Temperature dependence of delayed ehlorophyll fluorescence in intact leaves of higher plants. A rapid method for detecting the phase transition of thylakoid membrane lipids

The temperature dependence of the yield of in vivo prompt and delayed chiorophyll fluorescence was investigated in maize and barley leaves. In the chilling-sensitive maize, delayed fluorescence at steady-state level showed a maximum near the temperature at which thylakoid membrane lipids undergo a phase transition as revealed by differential scanning calorimetry measurements. In the chilling-resistant barley, no phase transition was detected above 0°C and the delayed light emission varied in a monotonic fashion. It was shown that measurements of delayed luminescence intensity in vivo can provide a rapid and sensitive method for detecting the phase change of membrane lipids in intact leaves of chilling-sensitive plant species such as tomato, cotton, cucumber, castor bean or avocado. In contrast, the use of steady-state prompt chlorophyll fluorescence as an indicator of membrane fluidity change was not successful. © 1983 Martinus Nijhoff/Dr W. Junk Publishers.SCOPUS: ar.jinfo:eu-repo/semantics/publishe