Deuterium Solid State NMR Studies of Intact Bacteria Treated With Antimicrobial Peptides

Abstract

Solid state NMR has been tremendously useful in characterizing the structure and dynamics of model membranes composed of simple lipid mixtures. Model lipid studies employing solid state NMR have included important work revealing how membrane bilayer structure and dynamics are affected by molecules such as antimicrobial peptides (AMPs). However, solid state NMR need not be applied only to model membranes, but can also be used with living, intact cells. NMR of whole cells holds promise for helping resolve some unsolved mysteries about how bacteria interact with AMPs. This mini-review will focus on recent studies using 2H NMR to study how treatment with AMPs affect membranes in intact bacteria.

Cell Penetrating Peptides: Classification, Mechanisms, Methods of Study, and Applications

“…Static solid‐state NMR is a technique commonly used with model lipid systems to study perturbations, including alterations in lipid acyl chain order. Since CPP‐induced permeabilization of the lipid bilayer affects the lipid acyl chains, this technique can be used to assess changes in lipid orientation resulting from the membrane disruption by CPPs [183,184] . In a recent study, the influence of lipopolysaccharide on the ability of the CPP to cause disordering of the lipid membranes of the E. coli has been studied with deuterium solid‐state NMR ( 2 H‐NMR) on intact bacteria cells.…”

“…Since CPP-induced permeabilization of the lipid bilayer affects the lipid acyl chains, this technique can be used to assess changes in lipid orientation resulting from the membrane disruption by CPPs. [183,184] In a recent study, the influence of lipopolysaccharide on the ability of the CPP to cause disordering of the lipid membranes of the E. coli has been studied with deuterium solid-state NMR ( 2 H-NMR) on intact bacteria cells. Experimental observations are consistent with a CPP-induced increase in the angular amplitude of lipid chain motions, diagnostic of enhanced permeabilization of the membrane.…”

A review on the measurement of the bending rigidity of lipid membranes

“…It is capable of performing measurements across a broad range of time scales, including measurement of the structural and mechanical properties of lipid membranes, [37][38][39][40][41] and proteins 42,43 along with techniques to reveal the mechanism of peptide interaction. 44,45 In 2 H NMR, the dePaked spectra are used to estimate the quadrupolar splitting of the ith C-2 H bond, and a frequency splitting, n (i) Q , appears which is proportional to the orientational order parameter, S (i) CD , that is, v…”

Antimicrobial Peptide Mechanisms Studied by Whole-Cell Deuterium NMR

“…To facilitate comparison with both MIC assays and model lipid studies, the amount of MSI-78 in the whole-cell NMR is expressed as a weight % of the dry weight of bacteria. Interestingly, much more (~30 times more) MSI-78 per lipid needs to be added to the whole bacteria samples to see the same lipid disruption in the corresponding model lipid NMR studies [ 68 , 71 ]. This observation is consistent with some of the AMP binding non-lipid targets and/or the presence of the non-lipid components of the cell envelope protecting the lipid bilayer from AMP-induced disruption.…”

“…Gram (+) bacteria, B. subtilis , treated with AMPs CAME and BP100, have also been studied with whole-cell NMR [ 70 , 71 , 72 , 73 ]. This work adjusted the ratio of deuterated PA to unlabelled oleic acid in the media to keep the cells healthy.…”