Monolayers of poly-L-lysine on mica--Electrokinetic characteristics.

Journal of colloid and interface science (2015-06-27)
Maria Morga, Zbigniew Adamczyk, Sebastian Gödrich, Magdalena Oćwieja, Georg Papastavrou
ABSTRACT

Physicochemical properties of poly-l-lysine and its monolayers on mica were thoroughly investigated by dynamic light scattering, electrokinetic methods and atomic force microscopy. The hydrodynamic diameter of PLL was equal to 25.5 nm within a wide range of pH and ionic strength. The electrophoretic measurements revealed that the molecules are positively charged for pH<10.5. By exploiting the electrophoretic mobility data, theelectrokinetic charge on the PLL molecules and their zeta potential were calculated. PLL monolayers of controlled coverage were deposited on mica under diffusion-controlled conditions by varying PLL bulk concentration and adsorption time. The electrokinetic characteristics of the monolayers were acquired in situ via streaming potential measurements. These studies allowed to uniquely determine the zeta potential of the monolayers as a function of pH and ionic strength. In this way the isoelectric point of the monolayers can be determined in a more convenient way compared to bulk measurements disturbed by the PLL molecule interactions. The stability of the monolayers under flow conditions was quantitatively evaluated via streaming potential measurements. The adsorption constant and the binding energy depth of PLL molecules were determined for different ionic strengths. These parameters indicate that the PLL monolayers remain stable over prolonged times.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Sodium chloride, BioXtra, ≥99.5% (AT)
Sigma-Aldrich
Sodium chloride, for molecular biology, DNase, RNase, and protease, none detected, ≥99% (titration)
Sigma-Aldrich
Sodium hydroxide solution, BioUltra, for molecular biology, 10 M in H2O
Sigma-Aldrich
Sodium chloride, BioReagent, suitable for cell culture, suitable for insect cell culture, suitable for plant cell culture, ≥99%
Sigma-Aldrich
Sodium chloride solution, 0.9% in water, BioXtra, suitable for cell culture
Sigma-Aldrich
Sodium hydroxide solution, 1.0 N, BioReagent, suitable for cell culture
Sigma-Aldrich
Sodium chloride solution, 5 M in H2O, BioReagent, for molecular biology, suitable for cell culture
Sigma-Aldrich
Sodium chloride solution, 5 M
SAFC
Sodium chloride solution, 5 M
Sigma-Aldrich
Sodium chloride, meets analytical specification of Ph. Eur., BP, USP, 99.0-100.5%
Sigma-Aldrich
Sodium chloride, BioUltra, for molecular biology, ≥99.5% (AT)
Sigma-Aldrich
Sodium chloride solution, 0.85%
Sigma-Aldrich
Sodium chloride solution, BioUltra, for molecular biology, ~5 M in H2O
Sigma-Aldrich
Sodium chloride, 99.999% trace metals basis
Sigma-Aldrich
Sodium chloride, BioPerformance Certified, ≥99% (titration), suitable for insect cell culture, suitable for plant cell culture
Sigma-Aldrich
Sodium hydroxide, BioUltra, for luminescence, ≥98.0% (T), pellets
Sigma-Aldrich
Sodium hydroxide, ultra dry, powder or crystals, 99.99% trace metals basis
Sigma-Aldrich
Sodium chloride, tablet
Sigma-Aldrich
Sodium chloride, AnhydroBeads, −10 mesh, 99.999% trace metals basis
Sigma-Aldrich
Sodium chloride, random crystals, optical grade, 99.9% trace metals basis
Sigma-Aldrich
Sodium chloride, AnhydroBeads, −10 mesh, 99.99% trace metals basis
Sigma-Aldrich
3-Ethyl-2,4-pentanedione, mixture of tautomers, 98%
Sigma-Aldrich
1,2-Dilinoleoyl-3-palmitoyl-rac-glycerol, ≥95% (TLC), liquid
Sigma-Aldrich
Sodium hydroxide-16O solution, 20 wt. % in H216O, 99.9 atom % 16O
Sigma-Aldrich
Sodium chloride-35Cl, 99 atom % 35Cl