End-to-end Distance Distribution in Fluorescent Derivatives of Bradykinin in Interaction with Lipid Vesicles

Abstract

Cellular membranes have relevant roles in processes related to proteases like human kallikreins and cathepsins. As enzyme and substrate may interact with cell membranes and associated co-factors, it is important to take into account the behavior of peptide substrates in the lipid environment. In this paper we report an study based on energy transfer in two bradykinin derived peptides labeled with the donor-acceptor pair Abz/Eddnp (ortho-aminobenzoic acid/N-[2,4-dinitrophenyl]-ethylenediamine). Time-resolved fluorescence experiments were performed in phosphate buffer and in the presence of large unilamelar vesicles of phospholipids, and of micelles of sodium dodecyl sulphate (SDS). The decay kinetics were analyzed using the program CONTIN to obtain end-to-end distance distribution functions f(r). Despite of the large difference in the number of residues the end-to-end distance of the longer peptide (9 amino acid residues) is only 20 % larger than the values obtained for the shorter peptide (5 amino acid residues). The proline residue, in position 4 of the bradykinin sequence promotes a turn in the longer peptide chain, shortening its end-to-end distance. The surfactant SDS has a strong disorganizing effect, substantially broadening the distance distributions, while temperature increase has mild effects in the flexibility of the chains, causing small increase in the distribution width. The interaction with phospholipid vesicles stabilizes more compact conformations, decreasing end-to-end distances in the peptides. Anisotropy experiments showed that rotational diffusion was not severely affected by the interaction with the vesicles, suggesting a location for the peptides in the surface region of the bilayer, a result consistent with small effect of lipid phase transition on the peptides conformations.

Conformations of Prolyl–Peptide Bonds in the Bradykinin 1–5 Fragment in Solution and in the Gas Phase

“…Overall, the calculated CCSs presented in Table agree well with the values that we measure, given that the experimental error is estimated to be around 2 Å 2 . The compaction in the gas phase corresponds to the effect observed for BK adhered to the surface of a micelle …”

“…The compaction in the gas phase corresponds to the effect observed for BK adhered to the surface of a micelle. 97…”

Influence of Membrane Phase on the Optical Properties of DPH

“…Fluorescence spectroscopies are nowadays one of the techniques of choice for the analysis of the behavior of probes in different membrane phases, due to the different responses related to the anisotropy decay [ 51 , 52 , 53 , 54 , 55 , 56 , 57 ]. We focus on the decay time and the fluorescence anisotropy decay as model analyses which can be obtained by computations [ 29 , 30 , 31 , 33 , 34 ].…”

Effects of artepillin C on model membranes displaying liquid immiscibility

“…Simple model membranes formed by distinct lipids have been investigated for decades to obtain important biophysical parameters related to these peculiar supramolecular structures. Taking into account the taxonomic classification of the studied cells, variations of the polar head group and/or the hydrophobic tail of the lipids result in relevant model systems that mimic cell membranes (2 ,13–15). It has been shown that, depending on their composition, lipid membranes may show specific lateral structures, characterized currently as membrane domains, which can associate distinct lipids and proteins (16,17).…”