Buildup of Exponentially Growing Multilayer Polypeptide Films with Internal Secondary Structure (original) (raw)
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Polypeptide Multilayer Films: Role of Molecular Structure and Charge
Langmuir, 2004
The role of molecular structure, charge, and hydrophobicity in polyelectrolyte layer-by-layer assembly (LbL) of thin films has been studied using the model polypeptides poly-L-glutamatic acid (PLGA) and poly-L-lysine (PLL), quartz crystal microbalance (QCM), and circular dichroism spectroscopy (CD). The adsorption behavior of PLGA and PLL has been compared with the structure of these molecules in aqueous solution under the same conditions. The data show that the deposition of polypeptide per adsorption step scales with average secondary structure content, whether R helix or sheet. This is contrary to the expectation based on the view that hydrogen bonds are crucial to polypeptide film assembly, because secondary structure formation in a polypeptide reduces its intermolecular hydrogen-bonding potential. The data also show that polypeptide adsorption scales with ionic strength and chain length. Taken together, the results increase knowledge of polypeptide-based LbL thin film fabrication and will help to provide a firmer foundation for the use of natural or designed polypeptides in LbL.
Langmuir, 2006
Layer-by-layer (LBL) polyelectrolyte films were constructed from poly(L-glutamic acid) (PGA) and poly(L-aspartic acid) (PAA) as polyanions, and from poly(L-lysine) (PLL) as the polycation. The terminating layer of the films was always PLL. According to attenuated total reflection Fourier transform infrared measurements, the PGA/PLL and PAA/PLL films, despite their chemical similarity, had largely different secondary structures. Extended -sheets dominated the PGA/PLL films, while R-helices and intramolecular -sheets dominated the PAA/PLL films. The secondary structure of the polyelectrolyte film affected the adsorption of human serum albumin (HSA) as well. HSA preserved its native secondary structure on the PGA/PLL film, but it became largely deformed on PAA/PLL films. Both PGA and PAA were able to extrude to a certain extent the other polyanion from the films, but the structural consequences were different. Adding PAA to a (PGA/PLL) 5 -PGA film resulted in a simple exchange and incorporation: PGA/PLL and PAA/PLL complexes coexisted with their unaltered secondary structures in the mixed film. The incorporation of PGA into a (PAA/PLL) 5 -PAA film was up to 50% and caused additional -structure increase in the secondary structure of the film. The proportions of the two polyanions were roughly the same on the surfaces and in the interiors of the films, indicating practically free diffusion for both polyanions. The abundance of PAA/PLL and PGA/PLL domains on the film surfaces was monitored by the analysis of the amide I region of the infrared spectrum of a reporter molecule, HSA, adsorbed onto the three-component polyelectrolyte films.
We report here on the structural characterization of polyelectrolytes multilayer films formed by poly(L-glutamic acid) and poly(L-lysine) (PGA/PLL). The growth of this system is compared to that of poly(styrenesulfonate)/poly(allylamine hydrochloride) (PSS/PAH) multilayers by means of in situ atomic force microscopy (AFM) and by optical waveguide lightmode spectroscopy (OWLS). In contrary to the (PSS/PAH)i films that are growing linearly with the number of deposited layer pairs i, optical data evidenced that the (PGA/PLL)i films are characterized by an exponential growth. The analysis of the structure of the (PSS/PAH)i films reveals a smooth featureless surface covered by small globules. On the other hand, (PGA/PLL)i films form extended structures that appear with a vermiculate pattern. We propose a new growth mechanism based on polyelectrolyte diffusion in and out of the film coupled to the formation of polyanion/polycation complexes at the surface of the film in order to explain the whole results. † INSERM.
Tuning the Surface Properties of Poly(Allylamine Hydrochloride)-Based Multilayer Films
Materials
The layer-by-layer (LbL) method of polyelectrolyte multilayer (PEM) fabrication is extremely versatile. It allows using a pair of any oppositely charged polyelectrolytes. Nevertheless, it may be difficult to ascribe a particular physicochemical property of the resulting PEM to a structural or chemical feature of a single component. A solution to this problem is based on the application of a polycation and a polyanion obtained by proper modification of the same parent polymer. Polyelectrolyte multilayers (PEMs) were prepared using the LbL technique from hydrophilic and amphiphilic derivatives of poly(allylamine hydrochloride) (PAH). PAH derivatives were obtained by the substitution of amine groups in PAH with sulfonate, ammonium, and hydrophobic groups. The PEMs were stable in 1 M NaCl and showed three different modes of thickness growth: exponential, mixed exponential-linear, and linear. Their surfaces ranged from very hydrophilic to hydrophobic. Root mean square (RMS) roughness was...
Macromolecules, 2002
We report here on the structural characterization of polyelectrolytes multilayer films formed by poly(L-glutamic acid) and poly(L-lysine) (PGA/PLL). The growth of this system is compared to that of poly(styrenesulfonate)/poly(allylamine hydrochloride) (PSS/PAH) multilayers by means of in situ atomic force microscopy (AFM) and by optical waveguide lightmode spectroscopy (OWLS). In contrary to the (PSS/PAH)i films that are growing linearly with the number of deposited layer pairs i, optical data evidenced that the (PGA/PLL)i films are characterized by an exponential growth. The analysis of the structure of the (PSS/PAH)i films reveals a smooth featureless surface covered by small globules. On the other hand, (PGA/PLL)i films form extended structures that appear with a vermiculate pattern. We propose a new growth mechanism based on polyelectrolyte diffusion in and out of the film coupled to the formation of polyanion/polycation complexes at the surface of the film in order to explain the whole results.
We report on the correlation of polyelectrolyte chain dynamics in polyelectrolyte complexes (PECs) with the deposition mode and chain mobility of polyelectrolytes (PEs) within layer-by-layerassembled (LbL) films. The study was performed using two polyelectrolyte systems: poly(2-(dimethylamino)ethyl methacrylate)/ poly(methacrylic acid) (PDMA/PMAA) and completely quaternized PDMA (Q100M)/PMAA. Hydrodynamic sizes of PDMA/PMAA and Q100M/PMAA complexes in solution were followed by fluorescence correlation spectroscopy (FCS), while three different techniques were applied to probe the structure and dynamics of the same PE pairs within LbL films. Specifically, deposition of PEs at surfaces was monitored by phase-modulated ellipsometry, film internal structureby neutron reflectometry (NR), and diffusion of assembled chains in the direction parallel to the substrateby fluorescence recovery after photobleaching (FRAP). By applying these complementary techniques to PDMA/PMAA and Q100M/PMAA systems in solution and at surfaces at various pH values, we found that the dynamics of polyelectrolyte chains within PECs underwent a prominent pH-dependent transition, and that this transition in chain dynamics was closely correlated with the transition between linear and exponential film growth modes. Neutron reflectometry results confirm that, at the transition point, film structure changed from layered for linearly depositing films to highly intermixed for exponentially depositing LbLs. Moreover, FRAP indicated a several-fold difference in PE lateral diffusion coefficient for the two different film growth modes. In addition, the pH transition point was affected by steric restrictions to ionic pairing, and the pH range of exponential growth and higher chain mobility was wider for Q100M/PMAA as compared with the PDMA/PMAA system, due to the presence of a methyl spacer at the amino group, resulting in weaker ionic pairing.
The Journal of Physical Chemistry B, 2003
Polyelectrolyte multilayers were built up layer by layer from a polycation (poly(L-lysine) (PLL)) solution and polyanion solutions containing simultaneously poly(L-glutamic acid) (PGA) and poly(L-aspartic acid) (PAA). Quartz crystal microbalance-dissipation (QCM-D) measurements revealed that, for a given number of bilayers, the mass of the films is a nonlinear function of the composition of the polyanion build-up solution: it remains independent of the composition up to a PGA content of about 50% and increases strongly at higher PGA contents. The secondary structures of these polyelectrolyte multilayers were monitored by Fourier transform infrared (FTIR) spectroscopy in the attenuated total reflection mode. The "pure" PLL/PGA films exhibited a large extent of -structure, characterized by a band at around 1609 cm -1 . In contrast, no such -structure elements were found in the "pure" PLL/PAA multilayers. The FTIR spectra of the polyelectrolyte multilayers constructed from PGA/PAA solutions of various compositions were analyzed by linear combinations of "pure" PLL/PGA and PLL/PAA film infrared spectra. It was found that the proportions of the two polyanions in the multilayers differed from those in the build-up solutions, with a preference toward the incorporation of PAA. At all film compositions, the -sheet content was higher than expected on the basis of the assumption that PGA and PAA interact independently with PLL. This indicates a cooperative effect between PGA and PAA for the formation of -sheets. This study may open up a route toward the utilization of the self-assembly of polyelectrolyte multilayers constructed from mixed polyanion and mixed polycation solutions, leading to films whose properties are directly related to the local interactions between the polyanions or the polycations constituting each layer of the film; such structures could not be attained by multilayers constructed from pure polyanion and polycation solutions.
Polypeptides mixed monolayers: collapse mechanism
Colloid and Polymer Science, 1989
The mechanism of the collapse process of monolayers of poly-L-alanine and of its mixtures with poly-γ-methyl-L-glutamate was studied at the water/air interface at temperatures of 15°, 20°, 25°, and 30 °C. From measurements of the collapse surface pressure as a function of molar ratios and from the determination of the collapse kinetics, as well as from ellipsometrical measurements of the thickness of the film, the complete solubility of the components, even in the collapsed phase, was deduced. Furthermore, activation energies and values ofΔG*,ΔH*, andΔS* in relationship to the kinetics of this process were deduced; it was shown that this process is constituted of a first phase of nucleation and of a second phase of growth both for the poly-L-alanine alone and for its mixtures with poly-γ-methyl-L-glutamate.