Bacterial cell wall charge

The presence of nanopartides suspended within the starch matrix would ensure continuous release of ions into the nutrient media. Copper ions released by the nanopartides may attach to the negatively charged bacterial cell wall and rupture it, thereby leading to protein denaturation and cell death [31]. The attachment of both ions and nanopartides to the cell wall caused accumulation of envelope protein precursors, which resulted in dissipation of... 

Bacterial cell walls contain different types of negatively charged (proton-active) functional groups, such as carboxyl, hydroxyl and phosphoryl that can adsorb metal cations, and retain them by mineral nucleation. Reversed titration studies on live, inactive Shewanella putrefaciens indicate that the pH-buffering properties of these bacteria arise from the equilibrium ionization of three discrete populations of carboxyl (pKa = 5.16 0.04), phosphoryl (oKa = 7.22 0.15), and amine (/ Ka = 10.04 0.67) groups (Haas et al. 2001). These functional groups control the sorption and binding of toxic metals on bacterial cell surfaces. 

Indeed, these results are qualitatively similar to those depicted in Figs. 12 and 13, and it is therefore tempting to ascribe them to the presence, on the bacterial cell walk, of polyanionic environments surrounding the sites where lysozyme cleaves the polysaccharide network. However, the point is that, although several authors have concluded from various experimental observations that the cell walls of bacteria such as Escherichia coli and Micrococcus luteus are predominantly negatively charged (Katerakky et al, 1953 Salton, 1964 Davies et al, 1969), the complexity of the bacterial cell wall architecture means that little is known about the... 

Polymyxin B. Polymyxin antibiotics are cationic compounds that are attracted to negatively charged phospholipids in the bacterial cell membrane. These drugs penetrate and disrupt the architecture and integrity of the surface membrane. Essentially, polymyxins act as detergents that break apart the phospholipid bilayer, which creates gaps in the bacterial cell wall, leading to the subsequent destruction of the bacteria.31... 

Positively charged photosensitizers, particularly cationic metallophthalocy-anines, have been proved to be most efficient in photodynamic inactivation of both Gram-negative and -positive bacteria. The reason is believed to lie in the electrostatic interaction of cationic photosensitizer with negatively charged sites at the outer surface of the bacterial cell wall, which facilitates the photosensitizer molecule binding to bacterial cells. 

US with changing salt concentration, indicating the presence of relatively thick adsorbed layers on the sulfur particles (see Fig. 4). This, as well as surface charge density measurements showing values comparable to surface charge densities of bacterial cell walls and humic acids, support the suggestion of proteins adsorbed on the particles. In addition, electrophoretic mobility experiments showed an iso-electric point comparable to the pKa-value of carboxylic acid groups in proteins (pKa=2.3) [45]. 

A problem arises if the surfaces are not smooth, but hairy. At various biological surfaces, such as bacterial cell walls, polymers or oligomeric molecules extend from the surface into the solution and may cause substantial modification of the tangential flow pattern the slip plane might be much farther out from the surface, and if nonspeciflcally adsorbed counterions infiltrate within the surface-polymer layer, o k is proportionally lowered and, at any rate, (o k - Oq) no longer represents the charge density of specifically adsorbed ions. 

The situation is more complicated when the surface comprises a permeable zone containing fixed charged groups. This is, for instance, the case for surfeces coated by a layer of polyelectrolytes. Coatings of polyelectrolytes are often present at biological surfaces, such as bacterial cell walls. We pay attention to these systems in Section 10.3.3. 

Radovic-Moreno AF, Lu TK, Puscasu VA, Yoon CJ, Danger R, Farokhzad OC. Surface charge-switching polymeric nanoparticles for bacterial cell wall-targeted dehvery of antibiotics. 2012. 

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