A fluorescence study of the interactions between sodium alginate and surfactants

Neumann, Miguel G.; Cavalheiro, Carla Cristina Schmitt; Iamazaki, Eduardo T.

doi:10.1016/s0008-6215(03)00051-x

Cited by 38 publications

(22 citation statements)

References 29 publications

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“…A study using the neutral fluorophore pyrene with alginate suggested the presence of hydrophobic regions within alginate, but only at concentrations approaching the solubility limit of alginate (45). Thus, while both M‐blocks and G‐blocks of alginate contain ‘hydrophobic regions’, their intrinsic hydrophobicity at typical concentrations is relatively weak as they would be comprised of primarily C–H groups of the pyranosyl rings and the occasional O ‐acetyl groups.…”

Section: Discussionmentioning

confidence: 99%

Hydrophobic Interactions in Complexes of Antimicrobial Peptides with Bacterial Polysaccharides

Kuo¹,

Chan²,

Burrows³

et al. 2007

Chem Biol Drug Des

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Biofilms of Pseudomonas aeruginosa are responsible for chronic lung infections in cystic fibrosis patients, where they are characterized by overproduction of the exopolysaccharide alginate and are recalcitrant to treatment with conventional antibiotics. Cationic antimicrobial peptides (CAPs) are potential alternatives for the treatment of multi-drug-resistant P. aeruginosa. However, alginate in P. aeruginosa biofilms has been proposed to bind these peptides through hydrophobic interactions, consequently reducing their activity [Chan et al., J Biol Chem 2004; 279: 38749-38754]. Here we perform biophysical analyses of the interactions of alginate with a series of novel peptide antibiotics (alpha-CAPs) of prototypic sequence KK-AAAXAAAAAXAAWAAXAAA-KKKK (where X = Phe, Trp or Leu). The hydrophobic interaction interface in alginate was investigated by examining (i) the effects of polysaccharide composition with respect to D-mannuronate and L-guluronate content; (ii) glycan chain length; (iii) alpha-CAP Trp fluorescence; and (iv) 1-anilinonaphthalene-8-sulfonate fluorescence. The results show that, while M and G residues produce equivalent effects, hydrophobic interactions between alginate and alpha-CAPs require a minimal glycan chain length. Peptide interactions with alginate are deduced to be mediated by hydrophobic microdomains comprised of pyranosyl C-H groups that are inducible upon formation of alpha-CAP-alginate complexes due to charge neutralization between the two species.

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Section: Discussionmentioning

confidence: 99%

Hydrophobic Interactions in Complexes of Antimicrobial Peptides with Bacterial Polysaccharides

Kuo¹,

Chan²,

Burrows³

et al. 2007

Chem Biol Drug Des

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“…From the present results, we postulate that peptides, by interacting with alginate, neutralize (some) negative charges on alginate, and thus produce a disruptive effect on lipid vesicles. These results also support the notion that alginate contains a significant hydrophobic domain which would be required in order to insert into a membrane mimetic environment (7,16).…”

Section: Effect Of Alginate On Peptide‐induced Calcein Releasementioning

confidence: 99%

Alginate as an auxiliary bacterial membrane: binding of membrane‐active peptides by polysaccharides*

Chan

Burrows

Deber

2005

The Journal of Peptide Research

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The chronicity of Pseudomonas aeruginosa infections in cystic fibrosis (CF) patients is characterized by overproduction of the exopolysaccharide alginate, in which biofilm bacteria are embedded. Alginate apparently contributes to the antibiotic resistance of bacteria in this form by acting as a diffusion barrier to positively charged antimicrobial agents. We have been investigating cationic antimicrobial peptides (CAPs) (prototypic sequence: KKAAAXAAAAAXAAWAAXAAAKKKK-NH(2), where X is any of the 20 commonly occurring amino acids) that were originally designed as transmembrane mimetic peptides. Peptides of this group above a specific hydrophobicity threshold insert spontaneously into membranes and have antibacterial activity at micromolar concentrations. While investigating the molecular basis of biofilm resistance to peptides, we found that the anionic alginate polysaccharide induces conformational changes in the most hydrophobic of these peptides typically associated with insertion of such peptides into membrane environments [Chan et al., J. Biol. Chem. (2004) vol. 279, pp. 38749-38754]. Through a combination of experiments measuring release of the fluorescent dye calcein from phospholipid vesicles, peptide interactions with vesicles in the presence and absence of alginate, and affinity of peptides for alginate as a function of net peptide core hydrophobicity, we show here that alginate offers a microenvironment that provides a protective mechanism for the encased bacteria by both binding and promoting the self-association of the CAPs. The overall results indicate that hydrophilic alginate polymers contain a significant hydrophobic compartment, and behave as an 'auxiliary membrane' for bacteria, thus identifying a unique protective role for biofilm exopolysaccharide matrices.

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“…The peptides consist of a nonamphipathic hydrophobic core sequence (11)(12)(13)(14)(15)(16)(17)(18)(19) residues) flanked at one or both termini by a number of Lys or Arg residues. These peptides, which were originally designed as transmembrane mimetic model peptides (6,7), have the prototypic sequence KKAAAXAAAAAX-AAWAAXAAAKKKK-NH 2 with several key features: (i) Ala is the preferred background residue because of its mid-range hydropathy and frequent occurrence in membrane protein transmembrane domains; (ii) a Trp residue is inserted into the hydrophobic segment as a fluorescent probe; and (iii) N-and C-terminal hydrophilic Lys residues act to solubilize the otherwise hydrophobic peptides in aqueous media to facilitate purification and characterization.…”

mentioning

confidence: 99%

Helix Induction in Antimicrobial Peptides by Alginate in Biofilms

Chan

Burrows

Deber

2004

Journal of Biological Chemistry

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Bacterial exopolysaccharides provide protection against phagocytosis, opsonization, and dehydration and act as a major structural component of the extracellular matrix in biofilms. They contribute to biofilmrelated resistance by acting as a diffusion barrier to positively charged antimicrobial agents including cationic antimicrobial peptides (CAPs). We previously created novel CAPs consisting of a nonamphipathic hydrophobic core flanked by Lys residues and containing a Trp residue in the hydrophobic segment as a fluorescent probe. Peptides of this type above a specific hydrophobicity threshold insert spontaneously into membranes and have antimicrobial activity against Gram-positive and Gram-negative bacteria at micromolar concentrations. Here we show that alginate, a polymer of ␤-Dmannuronate and ␣-L-guluronate secreted by the cystic fibrosis pathogen Pseudomonas aeruginosa, induces an ␣-helical conformation detected by circular dichroism spectroscopy and blue shifts in Trp fluorescence maxima in peptides above the hydrophobicity threshold, changes typically observed upon association of such peptides with nonpolar (membrane) environments. Parallel effects were observed in the archetypical CAPs magainin II amide and cecropin P1. Fluorescence resonance energy transfer studies indicated that alginate induces peptide-peptide association only in peptides above the hydrophobicity threshold, suggesting that the hydrophilic alginate polymer behaves as an "auxiliary membrane" for the bacteria, demonstrating a unique protective role for biofilm matrices against CAPs.Pseudomonas aeruginosa is the predominant respiratory tract pathogen in cystic fibrosis (CF) 1 patients, where chronic infection is due to the bacteria growing as a mucoid biofilm, a state characterized by overproduction of alginate (1-3). Alginate is a secreted extracellular polysaccharide composed of the uronic acid ␤-D-mannuronate and its C-5 epimer ␣-L-guluronate (4), which is partially O-acetylated at the second and/or third position(s) of the D-mannuronate residues. The chronicity of P. aeruginosa infections in CF; its high level intrinsic antimicrobial resistance, a result of the low permeability of its outer membrane to antibiotics and multidrug efflux systems; and its propensity to develop resistance during prolonged antimicrobial therapy have all presented major therapeutic challenges to CF caregivers.Our laboratory has developed a new category of cationic antimicrobial peptides that display antibacterial activity (5). The peptides consist of a nonamphipathic hydrophobic core sequence (11-19 residues) flanked at one or both termini by a number of Lys or Arg residues. These peptides, which were originally designed as transmembrane mimetic model peptides (6, 7), have the prototypic sequence KKAAAXAAAAAX-AAWAAXAAAKKKK-NH 2 with several key features: (i) Ala is the preferred background residue because of its mid-range hydropathy and frequent occurrence in membrane protein transmembrane domains; (ii) a Trp residue is inserted into the hydrophobic segment ...

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A fluorescence study of the interactions between sodium alginate and surfactants

Cited by 38 publications

References 29 publications

Hydrophobic Interactions in Complexes of Antimicrobial Peptides with Bacterial Polysaccharides

Hydrophobic Interactions in Complexes of Antimicrobial Peptides with Bacterial Polysaccharides

Alginate as an auxiliary bacterial membrane: binding of membrane‐active peptides by polysaccharides*

Helix Induction in Antimicrobial Peptides by Alginate in Biofilms

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