Peptoids successfully inhibit the growth of gram negative E. coli causing substantial membrane damage

Peptoids are an alternative approach to antimicrobial peptides that offer higher stability towards enzymatic degradation. It is essential when developing new types of peptoids, that mimic the function of antimicrobial peptides, to understand their mechanism of action. Few studies on the specific mechanism of action of antimicrobial peptoids have been described in the literature, despite the plethora of studies on the mode of action of antimicrobial peptides. Here, we investigate the mechanism of action of two short cationic peptoids, rich in lysine and tryptophan side chain functionalities. We demonstrate that both peptoids are able to cause loss of viability in E. coli susceptible cells at their MIC (16–32 μg/ml) concentrations. Dye leakage assays demonstrate slow and low membrane permeabilization for peptoid 1, that is still higher for lipid compositions mimicking bacterial membranes than lipid compositions containing Cholesterol. At concentrations of 4 × MIC (64–128 μg/ml), pore formation, leakage of cytoplasmic content and filamentation were the most commonly observed morphological changes seen by SEM in E. coli treated with both peptoids. Flow cytometry data supports the increase of cell size as observed in the quantification analysis from the SEM images and suggests overall decrease of DNA per cell mass over time

Current Serum Lipoprotein Levels and fMRI Response to Working Memory in Midlife

Aims: Given that high cholesterol levels at midlife are a risk factor for future cognitive decline, the goal of the current study was to determine if cholesterol-related alterations in the cerebrovascular response to cognition could be detected at midlife. Methods: Forty adults, aged 40-60 years, performed a 2-Back working memory task during fMRI. The associations between serum total cholesterol, HDL-cholesterol, and total cholesterol/HDL-cholesterol concentrations to task-related activation intensity were modeled using multivariate multiple regression (two-tailed p \u3c 0.02). Results: Higher levels of total cholesterol/HDL-cholesterol related to reduced working memory-related activation intensity in the left inferior parietal lobe, right superior frontal gyrus, and right middle frontal gyrus. Conclusion: These data provide preliminary support for a deleterious effect of elevated total cholesterol/HDL-cholesterol ratio on cerebrovascular support for cognition in midlife. Copyright © 2011 S. Karger AG, Basel