RESUMO
The effect of pectin esterification on the assembly of multilayers consisting of poly-L-lysine (PLL) and pectin was studied using surface plasmon resonance (SPR), Fourier transform infrared-attenuated total reflection spectroscopy (FTIR-ATR), and a quartz crystal microbalance with dissipation monitoring (QCMD). With each layer deposited, there was a progressive increase in mass. The net charge of the multilayers was positive and increased with increasing degree of esterification of the pectin. Multilayer fabrication involved a limited fractionation of the pectin preparations, with the more highly esterified pectins having a weaker affinity for PLL. The multilayers were relatively hydrated structures with estimates of solids content in the range 10-32% w/w. The more highly esterified pectins had a tendency to form more hydrated structures, which showed a strong deswelling when PLL was added to a freshly deposited pectin layer.
Assuntos
Membranas Artificiais , Pectinas , Polilisina/química , Esterificação , Pectinas/síntese química , Pectinas/química , Quartzo , Sensibilidade e Especificidade , Espectroscopia de Infravermelho com Transformada de Fourier , Ressonância de Plasmônio de Superfície , Propriedades de Superfície , Fatores de TempoRESUMO
The deposition of alternating layers of pectin and chitosan at a solid surface was studied using surface plasmon resonance. The binding of biopolymer to the surface was irreversible over the time scales examined. The deposition was dependent on the flow rate through the measurement cell with mass transport limitation at lower flow rates. The thickness of the deposited layer was dependent on the biopolymer concentration and was particularly marked for pectin. This was consistent with a process of initial attachment, followed by a slower structural rearrangement, which was inhibited at high initial surface concentrations of adsorbed biopolymer. Sequential deposition resulted in the formation of multilayers with an essentially linear growth rate.
Assuntos
Quitosana/química , Pectinas/química , Adsorção , Eletrólitos/química , Membranas Artificiais , Polímeros/síntese química , Análise Espectral , Ressonância de Plasmônio de Superfície , Propriedades de SuperfícieRESUMO
The effect of chitosan concentration on the gelation of pectins differing in charge density and distribution was examined, through the determination of gel stiffness and the binding of chitosan to the gel network. Chitosan acts as a crosslinker of concentrated pectin solutions, with its effectiveness showing a dependency on charge on the pectin. The networks produced are clear even under conditions of charge neutralisation.
Assuntos
Quitosana/química , Pectinas/química , Géis/química , Ligação Proteica , Espectroscopia de Infravermelho com Transformada de Fourier , Fatores de TempoRESUMO
The effect of poly-L-lysine concentration and degree of polymerisation on the gelation of pectins differing in charge density and distribution was examined, through the determination of gel stiffness, swelling behaviour and the binding of poly-L-lysine to the gel network. Poly-L-lysine acts as a crosslinker of concentrated pectin solutions, with its effectiveness showing dependencies on pH and charge distribution on the pectin. Neutralisation of the anionic charge on the pectin with the polycationic peptide leads to gel opacity and eventually network collapse.