A Study with Peptide Dendrimers Reveals an Extreme pH Dependence of Antibiotic Activity Above pH 7.4

The presence of ionizable groups in antimicrobial peptides (AMPs) often induces a pH-dependent activity. Herein we report that removing eight low pKa amino termini in antimicrobial peptide dendrimer (AMPD) G3KL provides dendrimer XC1 with a broader pH-activity range. Furthermore, raising the pH to 8.0 reveals strong activities against Klebsiella pneumoniae and methicillin resistant Staphylococcus aureus (MRSA) against which these AMPDs are inactive at pH 7.4. We observe a similar effect with polymyxin B on MRSA. Binding experiments with a fluorescent AMPD and the effect of high salt concentration suggest that the activity increase reflects stronger electrostatic binding to the bacteria at high pH. pH-profiling of other polycationic antimicrobials (polymers, peptidomimetics, foldamers, dendrimers) might similarly enhance their activity range, with possible use for topical treatments.

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A Study with Peptide Dendrimers Reveals an Extreme pH Dependence of Antibiotic Activity Above pH 7.4

10.26434/chemrxiv.14208287.v1 ◽

2021 ◽

Author(s):

Xingguang Cai ◽

Sacha Javor ◽

Bee-Ha Gan ◽

Thilo Köhler ◽

Jean-Louis Reymond

Keyword(s):

Bacterial Infections ◽

Chronic Wounds ◽

Ph Dependence ◽

Polymyxin B ◽

Antibiotic Activity ◽

Gram Negative Bacteria ◽

Gram Negative ◽

New Class ◽

Peptide Dendrimers ◽

Lysine Residues

In our efforts to develop peptide dendrimers as a new class of antimicrobial peptides (AMPs) against Gram-negative bacteria, we investigated their activity at acidic and basic pH, which correspond to the conditions of the site of bacterial infections on skin or biofilms and chronic wounds respectively. Removing the eight low pKa amino termini of our reference dendrimer G3KL by substituting the N-terminal lysine residues with aminohexanoic acid provided dendrimer XC1 with a broader pH-activity range. Furthermore, raising the pH to 8.0 revealed strong activities against Klebsiella pneumoniae and methicillin resistant Staphylococcus aureus (MRSA) against which the dendrimers are inactive at pH 7.4, an effect which we also observed with polymyxin B and tentatively assign to stronger binding to the bacteria at higher pH as observed with a fluorescence labeled dendrimer analog.

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A Study with Peptide Dendrimers Reveals an Extreme pH Dependence of Antibiotic Activity Above pH 7.4

10.26434/chemrxiv.14208287.v2 ◽

2021 ◽

Author(s):

Xingguang Cai ◽

Sacha Javor ◽

Bee-Ha Gan ◽

Thilo Köhler ◽

Jean-Louis Reymond

Keyword(s):

Bacterial Infections ◽

Chronic Wounds ◽

Ph Dependence ◽

Polymyxin B ◽

Antibiotic Activity ◽

Gram Negative Bacteria ◽

Gram Negative ◽

New Class ◽

Peptide Dendrimers ◽

Lysine Residues

In our efforts to develop peptide dendrimers as a new class of antimicrobial peptides (AMPs) against Gram-negative bacteria, we investigated their activity at acidic and basic pH, which correspond to the conditions of the site of bacterial infections on skin or biofilms and chronic wounds respectively. Removing the eight low pKa amino termini of our reference dendrimer G3KL by substituting the N-terminal lysine residues with aminohexanoic acid provided dendrimer XC1 with a broader pH-activity range. Furthermore, raising the pH to 8.0 revealed strong activities against Klebsiella pneumoniae and methicillin resistant Staphylococcus aureus (MRSA) against which the dendrimers are inactive at pH 7.4, an effect which we also observed with polymyxin B and tentatively assign to stronger binding to the bacteria at higher pH as observed with a fluorescence labeled dendrimer analog.

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Rationalizing the pH-Activity Response for Escherichia Coli’s Glycinamide Ribonucleotidetransformylase Through Computational Methods

10.26434/chemrxiv.7985618.v1 ◽

2019 ◽

Author(s):

Adrian Roitberg ◽

Pancham Lal Gupta

Keyword(s):

Transfer Reaction ◽

Catalytic Mechanism ◽

Ph Dependence ◽

Ph Effects ◽

Dependent Manner ◽

E Coli ◽

Gar Tfase ◽

Activity Curve ◽

Ph Dependent ◽

Formyl Transfer

<div>Human Glycinamide ribonucleotide transformylase (GAR Tfase), a regulatory enzyme in the de novo purine biosynthesis pathway, has been established as an anti-cancer target. GAR Tfase catalyzes the formyl transfer reaction from the folate cofactor to the GAR ligand. In the present work, we study E. coli GAR Tfase, which has high sequence similarity with the human GAR Tfase with most functional residues conserved. E. coli GAR Tfase exhibits structural changes and the binding of ligands that varies with pH which leads to change the rate of the formyl transfer reaction in a pH-dependent manner. Thus, the inclusion of pH becomes essential for the study of its catalytic mechanism. Experimentally, the pH-dependence of the kinetic parameter kcat is measured to evaluate the pH-range of enzymatic activity. However, insufficient information about residues governing the pH-effects on the catalytic activity leads to ambiguous assignments of the general acid and base catalysts and consequently its catalytic mechanism. In the present work, we use pH-replica exchange molecular dynamics (pH-REMD) simulations to study the effects of pH on E. coli GAR Tfase enzyme. We identify the titratable residues governing the pH-dependent conformational changes in the system. Furthermore, we filter out the protonation states which are essential in maintaining the structural integrity, keeping the ligands bound and assisting the catalysis. We reproduce the experimental pH-activity curve by computing the population of key protonation states. Moreover, we provide a detailed description of residues governing the acidic and basic limbs of the pH-activity curve.</div>

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Enhanced Analytic Approach for Describing pH Triggered Fast Drug Release Systems

Current Drug Delivery ◽

10.2174/1567201818999210112181853 ◽

2021 ◽

Vol 18 ◽

Author(s):

Aykut Elmas ◽

Guliz Akyuz ◽

Ayhan Bergal ◽

Muberra Andac ◽

Omer Andac

Keyword(s):

Drug Release ◽

Ph Dependence ◽

Slope Angle ◽

Ph Sensitive ◽

Analytic Model ◽

Two Dimensional ◽

Analytic Equation ◽

One Dimensional ◽

Ph Dependent ◽

Fast Release

Background: pH sensitive dendrimers attached to nanocarriers, as one of the drug release systems, has become quite popular due to their ease of manufacture in experimental conditions and ability to generate fast drug release in the targeted area. This kind of fast release behavior cannot be represented properly most of the existing kinetic mathematical models. Besides, these models have either no pH dependence or pH dependence added separately. So, they have remained one dimensional. Objective: The aim of this study was to establish the proper analytic equation to describe the fast release of drugs from pH sensitive nanocarrier systems. Then, to combine it with the pH dependent equation for establishing a two-dimensional model for whole system. Methods: We used four common kinetic models for comparison and we fitted them to the release data. Finding that, only Higuchi and Korsmeyer-Peppas models show acceptable fit results. None of these models have pH dependence. To get a better description for pH triggered fast release, we observed the behavior of the slope angle of the release curve. Then we puroposed a new analytic equation by using relation between the slope angle and time. Result: To add a pH dependent equation, we assumed the drug release is “on” or “off” above/below specific pH value and we modified a step function to get a desired behavior. Conclusion: Our new analytic model shows good fitting, not only one-dimensional time dependent release, but also two-dimensional pH dependent release, that provides a useful analytic model to represent release profiles of pH sensitive fast drug release systems.

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Systematic exploration of the pH dependence of a peptide hydrogel

Canadian Journal of Chemistry ◽

10.1139/cjc-2018-0419 ◽

2019 ◽

Vol 97 (6) ◽

pp. 430-434 ◽

Cited By ~ 2

Author(s):

Natashya Falcone ◽

Tsuimy Shao ◽

Xiaoyi Sun ◽

Heinz-Bernhard Kraatz

Keyword(s):

Mechanical Strength ◽

Narrow Range ◽

Ph Dependence ◽

Stimuli Responsive ◽

Systematic Exploration ◽

Ph Conditions ◽

Ph Dependent ◽

Functional Biomaterials ◽

Peptide Hydrogel

Stimuli-responsive peptide gels are a growing class of functional biomaterials that are involved in many applications in research. Here, we present a novel di-peptide hydrogel from the compound Boc–Phe–Trp–OH in various buffer and pH conditions. We examine the effects of different stimuli, including temperature and pH, on the mechanical strength of the gels through frequency rheology studies. We found that this hydrogelator is highly pH dependent, only forming a gel in a narrow range of pH 6–7. This hydrogelator hold promise for the development of new stimuli-responsive biomaterials for specific applications that require this type of specific stimuli.

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Characterization of a Histidine Containing Antimicrobial Peptide with pH Dependent Activity

Biophysical Journal ◽

10.1016/j.bpj.2018.11.493 ◽

2019 ◽

Vol 116 (3) ◽

pp. 83a ◽

Cited By ~ 1

Author(s):

Luis Santiago-Ortiz ◽

Morgan Hitchner ◽

Thaddeus Palmer ◽

Gregory A. Caputo

Keyword(s):

Antimicrobial Peptide ◽

Dependent Activity ◽

Ph Dependent

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pH-dependent Perforation of Macrophage Phagosomes by Listeriolysin O from Listeria monocytogenes

Journal of Experimental Medicine ◽

10.1084/jem.186.7.1159 ◽

1997 ◽

Vol 186 (7) ◽

pp. 1159-1163 ◽

Cited By ~ 173

Author(s):

Kathryn E. Beauregard ◽

Kyung-Dall Lee ◽

R. John Collier ◽

Joel A. Swanson

Keyword(s):

Listeria Monocytogenes ◽

Ph Dependence ◽

Mouse Bone Marrow ◽

Listeriolysin O ◽

Bafilomycin A1 ◽

Wild Type ◽

Major Virulence Factor ◽

Ph Dependent ◽

Vacuolar Ph

The pore-forming toxin listeriolysin O (LLO) is a major virulence factor implicated in escape of Listeria monocytogenes from phagocytic vacuoles. Here we describe the pH-dependence of vacuolar perforation by LLO, using the membrane-impermeant fluorophore 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS) to monitor the pH and integrity of vacuoles in mouse bone marrow–derived macrophages. Perforation was observed when acidic vacuoles containing wild-type L. monocytogenes displayed sudden increases in pH and release of HPTS into the cytosol. These changes were not seen with LLO-deficient mutants. Perforation occurred at acidic vacuolar pH (4.9–6.7) and was reduced in frequency or prevented completely when macrophages were treated with the lysosomotropic agents ammonium chloride or bafilomycin A1. We conclude that acidic pH facilitates LLO activity in vivo.

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A systematic approach to study the pH-dependent release, productivity and product specificity of dextransucrases

Microbial Cell Factories ◽

10.1186/s12934-019-1208-8 ◽

2019 ◽

Vol 18 (1) ◽

Cited By ~ 6

Author(s):

Jonas Schmid ◽

Julia Bechtner ◽

Rudi F. Vogel ◽

Frank Jakob

Keyword(s):

Extracellular Enzymes ◽

Methodological Approach ◽

Reaction Conditions ◽

Product Specificity ◽

Ph Values ◽

Gelling Properties ◽

Dependent Activity ◽

Ph Dependent ◽

The Stability ◽

Extracellular Environment

Abstract Background Dextransucrases are extracellular enzymes, which catalyze the formation of α-1→6-linked glucose polymers from sucrose. These enzymes are exclusively expressed by lactic acid bacteria, which commonly acidify the extracellular environment due to their physiology. Dextransucrases are thus confronted with steadily changing reaction conditions in regards to the environmental pH, which can further affect the amount of released dextransucrases. In this work, we studied the effect of the environmental pH on the release, the productivity and the product specificity of the dextransucrase expressed by Lactobacillus (L.) hordei TMW 1.1822. Dextransucrases were recovered as crude extracts at pH 3.5–pH 6.5 and then again used to produce dextrans at these pH values. The respectively produced dextran amounts and sizes were determined and the obtained results finally systematically correlated. Results Maximum dextran amounts were produced at pH 4.0 and pH 4.5, while the productivity of the dextransucrases significantly decreased at pH 3.5 and pH 6.5. The distribution of dextran amounts produced at different pH most likely reflects the pH dependent activity of the dextransucrases released by L. hordei, since different transglycosylation rates were determined at different pH using the same dextransucrase amounts. Moreover, similar hydrolysis activities were detected at all tested conditions despite significant losses of transglycosylation activities indicating initial hydrolysis prior to transglycosylation reactions. The molar masses and rms radii of dextrans increased up to pH 5.5 independently of the stability of the enzyme. The gelling properties of dextrans produced at pH 4.0 and pH 5.5 were different. Conclusions The presented methodological approach allows the controlled production of dextrans with varying properties and could be transferred and adapted to other microbes for systematic studies on the release and functionality of native sucrases or other extracellular enzymes.

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