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PubMed2006

Acid-cleavable polymeric core-shell particles for delivery of hydrophobic drugs.

Here we describe the combined use of acid-labile microgel approach and RAFT-mediated seeded dispersion polymerization technique to prepare an acid-cleavable core-shell like polymeric colloidal system for the delivery of hydrophobic drugs at slightly acidic sites. A new bisacrylate acetal crosslinker was copolymerized with n-butyl acrylate (BA) in the presence of a RAFT agent using a dispersion polymerization technique, which yielded crosslinked spherical particles with the size ranging between 150 and 500 nm. The particles were cleaved in a pH-dependent manner similar to the acid-labile hydrolysis behaviour of the crosslinker. In order to mask the hydrophobic surface of the particles, polyethylene glycol acrylate (PEG-A) was grafted onto poly(BA) seed particles via the RAFT agent groups on the particle surface. The acidic-site selective delivery potential of the poly(BA)-g-poly(PEG-A) particles was assessed in-vitro using a lipophilic fluorescent dye as a model hydrophobic drug. Ca. 73% and 34% of the total dye loaded in the particles was found to be released at pH 5.0 and 7.4 in 24 h, respectively. The growth of human neuroblastoma cells was not affected by the incubation with the core-shell particles and their cleavage by-products up to 3 mg/ml concentration. The physicochemical and the functional features support the potential value of the acid-cleavable poly(BA) core-poly(PEG-A) shell particles as carriers for the delivery of hydrophobic drugs at acidic sites.

Acetates↗
PubMed2004

Polymerization shrinkage: effects of boundary conditions and filling technique of resin composite restorations.

OBJECTIVE: To evaluate the linear polymerization shrinkage (LPS) and the effect of polymerization shrinkage of a resin composite and resin-dentin bond strength under different boundary conditions and filling techniques. METHODS: Two cavities (4 x 4 x 2 mm3) were prepared in bovine incisors (n=30). The teeth were divided into three groups, according to boundary conditions: In group TE, the total-etch technique was used. In group EE, only enamel was conditioned, and in group NE, none of the walls of the cavities were conditioned. A two-step adhesive system was applied to all cavities. The resin composite was inserted in one (B) or three increments (I) and light-cured with 600 mW/cm2 (80 s). The LPS (%) was measured in the top-bottom direction, by placing a probe in contact with resin composite during curing. Enamel and total mean gap widths were measured (400 x) in three slices obtained after sectioning the restorations. Then, the slices were sectioned again, either to obtain sticks from the adhesive interface from the bottom of the cavity or to obtain resin composite sticks (0.8 mm2) to be tested for tensile strength (Kratos machine, 0.5 mm/min). The data was subjected to a two-way repeated measures ANOVA and Tukey's test for comparison of the means (alpha=0.05). RESULTS: The highest percentage of LPS was found for the TE when bulk filled, and the lowest percentage of LPS was found in the EE and NE when incrementally filled. The resin-dentin bond strength was higher and the total mean gap width was lower for TE group; no significant effect was detected for the main factor filling techniques. No difference was detected for the tensile strength of resin composite among the experimental groups. CONCLUSIONS: The filling technique is not able to minimize effects of the polymerization shrinkage, and bonding to the cavity walls is necessary to assure reduced mean gap width and high bond strength values.

Analysis of Variance↗
PubMed2006

Enhanced removal of p-chloroaniline from aqueous solution by a carboxylated polymeric sorbent.

In the present study a carboxylated styrene-divinylbenzene (St-DVB) polymeric sorbent (CSPS) was prepared for enhanced removal of p-chloroaniline from aqueous solution. A commercial styrene-divinylbenzene polymeric sorbent Amberlite XAD-4 was selected as the reference sorbent to evaluate the performance of CSPS. Characterization of CSPS was determined by infrared spectroscopy and pore size distribution. A p-chloroaniline sorption enhancement on CSPS at capacity about twice of Amberlite XAD-4 was observed, which was mainly attributed to the carboxyl group added on the polymeric matrix. Different pH-dependent sorption property of p-chloroaniline onto XAD-4 and CSPS was observed partly due to the role of carboxyl group. Sorption isotherm of p-chloroaniline on CSPS could be represented by Freundlich model reasonably, and that on XAD-4 was more suitable for Langmuir model. Kinetic studies demonstrated that the uptake of p-chloroaniline on CSPS and XAD-4 followed the pseudo-second order model. Moreover, breakthrough curves on CSPS further demonstrated its better performance towards p-chloroaniline removal from aqueous solution. Complete regeneration of the spent sorbent CSPS was achieved by dilute hydrochloric acid for its repeated use, implying its potential application in associated chemical wastewater treatments.

Adsorption↗
PubMed2004

Thermodynamic dissection of the polymerizing and editing modes of a DNA polymerase.

DNA polymerases with intrinsic proofreading activity interact with DNA primer/templates in two distinct modes, corresponding to the complexes formed during the 5'-3' polymerization or 3'-5' editing of a nascent DNA chain. Thermodynamic measurements designed to quantify the energetic contributions of individual DNA-protein contacts in either the polymerizing or editing complexes are complicated by the fact that both species exist in solution and are not resolved in conventional DNA-protein binding assays. To overcome this problem, we have developed a new binding analysis that combines information from steady-state and time-resolved fluorescence experiments and uses the Klenow fragment of Escherichia coli DNA polymerase I (KF) and fluorescently labeled primer/template oligonucleotides as a model polymerase-DNA system. Steady-state fluorescence titrations are used to evaluate the overall affinity of KF for the primer/template, while time-resolved fluorescence anisotropy is used to quantify the equilibrium fractions of the primer/template bound in the polymerizing and editing modes. From a combined analysis of both data, the equilibrium constant and hence standard free energy change associated with each binding mode can be obtained unequivocally. This method is initially used to determine the equilibrium constants describing binding of a correctly base-paired primer/template to the 5'-3' polymerase and 3'-5' exonuclease sites of KF. It is then extended to quantify the extent to which these parameters are affected by the introduction of mismatches into the primer/template, and by rearrangement of specific side-chains in the exonuclease domain of the protein. While these perturbants were originally designed to demonstrate the utility of our new approach, they are also relevant in their own right since they have helped identify some hitherto unknown determinants of polymerase fidelity.

Anisotropy↗
PubMed2005

Chimeric epitopes delivered by polymeric synthetic linear peptides induce protective immunity to malaria.

Polymeric linear peptide chimeras (LPCs) that incorporate Plasmodium vivax promiscuous T cell epitopes and the P. falciparum circumsporozoite protein B cell epitope have been shown to induce a high level of immunogenicity and overcome genetic restriction when tested as vaccine immunogens in BALB/c mice. The present study evaluates the biological relevance of several LPCs using a well characterized rodent malaria model. Polymeric peptide constructs based on P. berghei and P. yoelii sequences, and orthologous to the human malaria sequences included in the original LPCs, were designed and tested for immunogenicity in mice of different H-2 haplotypes. We demonstrate that robust immune responses are induced and that peptides containing the orthologous rodent Plasmodium sequences exhibited similar immunogenic capabilities. Unique to this report, we show that LPCs can also prime MHC class I-restricted cytotoxic T lymphocytes (CTLs) and, most relevantly, that a peptide construct prototype incorporating single B, T and CTL epitopes induced protection against an experimental challenge with P. berghei or P. yoelii sporozoites. Collectively, these results suggest that polymeric polypeptide chimeras can be used as a platform to deliver subunit vaccines.

Animals↗
PubMed2005

Imaging beta-amyloid fibrils in Alzheimer's disease: a critical analysis through simulation of amyloid fibril polymerization.

The polymerization of beta-amyloid (A beta) peptides into fibrillary plaques is implicated, in part, in the pathogenesis of Alzheimer's disease. A beta molecular imaging probes (A beta-MIPs) have been introduced in an effort to quantify amyloid burden or load, in subjects afflicted with AD by invoking the classic PET receptor model for the quantitation of neuronal receptor density. In this communication, we explore conceptual differences between imaging the density of amyloid fibril polymers and neuronal receptors. We formulate a mathematical model for the polymerization of A beta with parameters that are mapped to biological modulators of fibrillogenesis and introduce a universal measure for amyloid load to accommodate various interactions of A beta-MIPs with fibrils. Subsequently, we hypothesize four A beta-MIPs and utilize the fibrillogenesis model to simulate PET tissue time activity curves (TACs). Given the unique nature of polymer growth and resulting PET TAC, the four probes report differing amyloid burdens for a given brain pathology, thus complicating the interpretation of PET images. In addition, we introduce the notion of an MIP's resolution, apparent maximal binding site concentration, optimal kinetic topology and its resolving power in characterizing the pathological progression of AD and the effectiveness of drug therapy. The concepts introduced in this work call for a new paradigm that goes beyond the classic parameters B(max) and K(D) to include binding characteristics to polymeric peptide aggregates such as amyloid fibrils, neurofibrillary tangles and prions.

Alzheimer Disease↗
PubMed2004

Repair strength of autopolymerizing, microwave, and conventional heat-polymerized acrylic resins.

STATEMENT OF PROBLEM: Acrylic resin dentures are susceptible to fracture after clinical use. The repair procedure should be time saving, strong, and should not affect dimensional accuracy. PURPOSE: This study evaluated the transverse repair strength of a conventional heat-polymerized (Lucitone 199, "L") and a microwave-polymerized (Acron MC, "A") acrylic resin that were repaired with these same resins and with an autopolymerizing acrylic resin (Acron MC/R, "AR"). MATERIAL AND METHODS: Twenty-four rectangular specimens (65.0 x 10.0 x 3.3 mm) of L or A and 6 of AR were manufactured according to ISO/FDI 1567 and stored in distilled water at 37 degrees C for 7 days. Eighteen specimens of L or A were selected randomly. Six specimens of each material remained intact (control), each 6 were sectioned in the middle to create a 10-mm gap and repaired with the materials L, A, or AR. After an additional 7 days of storage at 37 degrees C, the transverse strength (MPa) of the repaired and intact specimens was measured using a 3-point bending test. A 2-way ANOVA and a Tukey HSD test were performed to identify significant differences (alpha=.05). The nature of the failure was noted as adhesive, cohesive, or mixed. RESULTS: The intact and repaired specimens showed similar transverse strength values (MPa), except for A-intact (80.6 +/- 2.9), which was significantly stronger (P<.05) than the other materials tested as well as the repaired groups (P<.05). No differences were detected among the repaired groups. Repaired specimens exhibited 3 types of failures: adhesive (interface), cohesive (only in the repair material), and mixed (interface and repair material), with incidences of 2.8, 25, and 72.2%, respectively. CONCLUSION: The autopolymerizing resin exhibited a repair strength similar to those found for the conventional heat- and microwave-polymerized materials.

Acrylic Resins↗
PubMed2006

Comparison of temperature increase in the pulp chamber during the polymerization of materials used for the direct fabrication of provisional restorations.

STATEMENT OF PROBLEM: Polymerization of resin materials used for the fabrication of provisional restorations is associated with an exothermic reaction. This temperature rise may present a serious biological problem, since it can cause iatrogenic thermal trauma to the pulp. PURPOSE: This in vitro study compared the temperature increase in the pulp chamber of a molar placed in contact with different resins used for the direct fabrication of provisional restorations. MATERIAL AND METHODS: Polymethyl methacrylate (Jet), polyethyl methacrylate (Snap), polyvinylethyl methacrylate (Trim), Bis-acrylic composite (Protemp II), and a VLP urethane dimethacrylate (Revotec LC) were compared with respect to their exothermic reaction properties during polymerization. A mandibular molar prepared for a complete coverage restoration was placed in an acrylic resin block. A thermal probe connected to a digital thermometer was placed into the pulp chamber. Specimens were submerged in a water bath to simulate intraoral conditions. The provisional resin materials tested were measured and mixed according to manufacturer's instructions. The resin mixture was placed into a vacuum-formed acetate template and was then positioned on the prepared molar tooth. The temperature was recorded during polymerization at 30-second intervals until it was evident that the peak temperature had been reached. Temperature increase was measured ( degrees C) for both the initial crown fabrication and the reline procedures. Data were analyzed with descriptive statistics, 1-way analysis of variance, and Tukey Honestly Significant Difference tests (alpha=.05). RESULTS: One-way ANOVA revealed significant differences (F=57.010, P<.0001) in temperature rise for different provisional resin materials. Mean temperature increase for the provisional crown fabrication ranged from 37.76 degrees C for the polyvinylethyl methacrylate to 39.40 degrees C for the polymethyl methacrylate. Mean temperature rise for the reline procedures ranged from 36.80 degrees C for the polyvinylethyl methacrylate to 37.69 degrees C for the polymethyl methacrylate. All of the tested materials produced an exothermic chemical reaction. CONCLUSIONS: Polymethyl methacrylate produced the higher exothermic reaction in both initial crown fabrication and reline procedures. Polyethyl methacrylate, polyvinylethyl methacrylate, and Bis-acrylic resins tested were not significantly different from each other.

Acrylic Resins↗
PubMed2006

Effect of substrate and fibrin polymerization inhibitor on determination of plasma thrombin generation in vitro.

BACKGROUND: Thrombin generation potential, a critical haemostatic measure, can be determined by continuous detection of total thrombin or direct subsampling. However, differences between methods exist in area under the curve or peak thrombin calculated. Also, impact of anticoagulants on thrombin generation may vary depending on mode of analysis. OBJECTIVE: We studied the effect of components on thrombin generation in the presence or absence of anticoagulants. METHODS: The continuous method was conducted with plasma +/- fibrin(ogen) +/- fibrin polymerization inhibitor. Plasma contained slow-reacting TG5134 substrate at 37 degrees C and reaction was started with dilute thromboplastin in CaCl(2)/Tris buffer. Absorbance (405 nm) was recorded over time and free thrombin calculated from total thrombin activity. For the subsampling method, similar plasma mixtures +/- TG5134 were reacted and free thrombin measured directly as the difference in activity against S2238 substrate of timed subsamples taken into EDTA or EDTA + antithrombin + heparin. RESULTS: Slow-reacting substrate in the continuous method acted as a competitor for thrombin, giving delayed but greater free thrombin than direct subsampling. These differences persisted to varying extents with all anticoagulants tested. In either method, presence of polymerization inhibitor increased the amount of free thrombin. Continuous method detection of alpha(2)macroglobulin complexes was hampered by sensitivity limits leading to inordinate free thrombin calculations. Especially with hirudin, although free thrombin remained at the end of the subsampling method, continuous method calculations assumed no residual free thrombin. CONCLUSION: In vitro plasma thrombin generation is delayed and increased by slow-acting substrate and fibrin polymerization inhibitor.

Adult↗
PubMed2004

Preparation of polyacrylamide and gamma-zirconium phosphate nanocomposites by intercalative polymerization.

A new inorganic-organic nanocomposite of polyacrylamide (PAM) and gamma-zirconium phosphate (gamma-ZrP) was prepared by intercalative polymerization. Intercalation of acrylamide (AM) monomer in gamma-ZrP was investigated by sonochemical and refluxing methods. High-intensity ultrasound does not induce the polymerization of AM but enhances greatly the intercalation rate. On the other hand, ultrasound also enhanced hydrolyzation of -CONH2 and shrinkage of PAM gel. The interlayer distance of AM-intercalated gamma-ZrP is 16.4 A. The polymerization and intercalation of AM occurred nearly at the same time by refluxing method. The same gamma-ZrP/PAM nanocomposites were obtained with (NH4)2S2O8 treatment.

Journal Article↗
PubMed2004

Electrochemical removal of bisphenol A based on the anodic polymerization using a column type carbon fiber electrode.

Electrochemical removal based on the polymerization of organic pollutants on an anode surface was performed on bisphenol A (BPA) and its derivatives, bisphenol S (BPS) and diphenolic acid (DPA). It was confirmed by voltammetric techniques that the electrochemical oxidation of these compounds leads to the formation of a polymeric film on a carbon electrode surface. The electrochemical removals of BPA, BPS and DPA based on the anodic polymerization were attempted in the batch type cell. A carbon fiber (CF) was used as an anode with a very large surface area. The high removal efficiency for BPA, BPS, and DPA was obtained by applying a potential at 0.75-, 1.0-, and 0.8-V, respectively. The removal efficiency for BPA does not decrease in the presence of 10ppm humic acid. The electropolymerized BPA film formed on the CF surface was characterized by FT-IR and UV/vis. The continuous treatment of BPA was achieved by using the flow system with a column type of CF electrode. The applicability of this method for removal of BPA from aqueous solution was tested at several different conditions, i.e., flow rate of solution and concentration of electrolyte and BPA. This system can be applied for removal of a low concentration BPA even from low electrolyte concentrations of aqueous solution.

Benzhydryl Compounds↗
PubMed2002

Fluorescent assay for polymerization of purified bacterial FtsZ cell-division protein.

Septum formation in Escherichia coli is a complex cascade of interactions among cell-division proteins. The tubulin-like FtsZ division protein localizes to the division site and serves a cytoskeletal role during septum formation. A novel fluorescent-based 96-well format filter assay has been developed to measure the polymerization of FtsZ. A mixture of monomers and aggregates (38 to approximately 200 KDa in range) of purified wild-type FtsZ and a fluorescently tagged derivative of FtsZ protein in stoichiometric ratio passes through a 0.2-microm filter membrane, while polymerized FtsZ is retained on the filter. Addition of the SulA protein to the assay leads to rapid disassembly of existing FtsZ polymers, demonstrating its natural regulatory effect on FtsZ under the assay conditions. This assay is sensitive (requiring 2 microM FtsZ or less) and facilitates high-throughput screening of factors affecting FtsZ polymerization.

Bacterial Proteins↗
PubMed2003

Reducing the incidence and severity of pericardial adhesions with a sprayable polymeric matrix.

PURPOSE: This study was undertaken to evaluate the antiadhesive properties of a polymeric agent in infants undergoing staged surgical correction of congenital heart abnormalities. DESCRIPTION: Sixteen infants having staged surgical repair were treated with a polymeric matrix at the completion of the initial surgery. There were 5 untreated controls. The tenacity and extent of adhesions at five separate regions of the heart were evaluated at the follow-up surgery. EVALUATION: For all sites combined, there was a threefold difference in median tenacity scores in favor of the experimental treatment (1.0 vs 3.0, p < 0.01). Significant differences were achieved separately at the right ventricle and the anterior surface of the great vessels (p = 0.02 for both comparisons). Analysis of adhesion scores reflecting the extent of adhesions similarly favored the experimental treatment for all sites (80 vs 270, p < 0.01), with significant differences persisting at the right atrium (p < 0.01) and the anterior surface of the great vessels (p = 0.04). There were no treatment-related adverse events. CONCLUSIONS: Use of this polymeric agent at the completion of open cardiac surgery may prevent the occurrence or reduce the severity of pericardial adhesions.

Female↗
PubMed1988

Thiol group reactivity and polymerization of actin in the presence of ATP analogs.

We have investigated polymerization and the number of SH-groups of monomeric actin exposed in the presence of (beta, gamma)-substituted ATP-analogs. Actin, when depolymerized in a buffer containing 10 equiv. of APPCP exposes 4 thiol groups. The time course of the SH-titration is similar to that obtained when F-actin is depolymerized in a nucleotide free buffer. When actin is depolymerized in a buffer containing 10 equiv. of APPNP it also exposes 4 thiols. However, thiol-titration follows different kinetics. While one SH group reacts quickly the reaction of 3 others is retarded. We conclude that APPNP exhibits a shielding effect on part of the thiols for a period of time, while APPCP does not. In agreement with this, in the presence of APPNP yield of polymerization as well as stability against denaturation are distinctly higher than without added nucleotide or in the presence of APPCP. In line with this a hydrolysis product, most probably APPNH2, was associated with the filaments, as indicated by the replacement of tritiated ADP during polymerization, and from analysis of the attached nucleotide. Under the same conditions APPCP replaced tritiated ADP only to a small extent. The data indicate that APPNP interacts with monomeric actin much less than ATP and still less than ADP, but more so APPCP. APPNP is cleaved by actin ATPase and a hydrolysis product is incorporated into filaments.

Actins↗
PubMed2003

Tubulin polymerizing activity of dictyostatin-1, a polyketide of marine sponge origin.

Dictyostatin-1 had previously been isolated from a marine sponge of the genus Spongia sp. and described as a cytotoxic agent to murine and human cancer cells, but its mechanism of activity was unknown. In a routine screening assay used to detect cytotoxic compounds of marine origin, dictyostatin-1 was identified as a highly active component in an extract from a Lithistida sponge and exploration into its pharmacology was pursued. Initial studies demonstrated that dictyostatin-1 arrested cells in the G(2)/M phase of the cell cycle. Staining of these cells with antitubulin revealed cells having multiple aster formations and microtubule matrix bundling patterns similar to that seen in cells exposed to paclitaxel. Dictyostatin-1 was able to induce the polymerization of purified bovine brain tubulin in vitro and the polymerized tubulin remained stable at cold temperatures. Dictyostatin-1 also proved to be highly potent in two paclitaxel-resistant human cancer cell lines expressing active P-glycoprotein. Together, these results indicate that dictyostatin-1 is a potent inducer of tubulin polymerization and retains activity in cells expressing the P-glycoprotein efflux pump.

Animals↗
PubMed2000

Polymerization of rod-like macromolecular monomers studied by stopped-flow, multiangle light scattering: set-up, data processing, and application to fibrin formation.

Many biological supramolecular structures are formed by polymerization of macromolecular monomers. Light scattering techniques can provide structural information from such systems, if suitable procedures are used to collect the data and then to extract the relevant parameters. We present an experimental set-up in which a commercial multiangle laser light scattering photometer is linked to a stopped-flow mixer, allowing, in principle, the time-resolved extrapolation of the weight-average molecular weight M(w) and of the z-average square radius of gyration (z) of the polymers from Zimm-like plots. However, if elongated structures are formed as the polymerization proceeds, curved plots rapidly arise, from which M(w) and (z) cannot be recovered by linear fitting. To verify the correctness of a polynomial fitting procedure, polydisperse collections of rod-like or worm-like particles of different lengths, generated at various stages during bifunctional polycondensations of rod-like macromolecular monomers, were considered. Then, the angular dependence of their time-averaged scattered intensity was calculated in the Rayleigh-Gans-Debye approximation, with random and systematic noise also added to the data. For relatively narrow size distributions, a third-degree polynomial fitting gave satisfactory results across a broad range of conversion degrees, yielding M(w) and (z) values within 2% and no greater than 10-20%, respectively, of the calculated values. When more broad size distributions were analyzed, the procedure still performed well for semiflexible polymers, but started to seriously underestimate both M(w) and (z) when rigid rod-like particles were analyzed, even at relatively low conversion degrees. The data were also analyzed in the framework of the Casassa approximation, from which the mass per unit length of the polymers can be derived. These procedures were applied to a set of data taken on the early stages of the thrombin-catalyzed polymerization of fibrinogen, a rod-like macromolecule approximately 50 nm long. The polymers, grown in the absence of Ca(2+) by rate-limiting amounts of thrombin, appeared to be characterized by a much broader size distribution than the one expected for a classical Flory bifunctional polycondensation, and they seem to behave as relatively flexible worm-like double-stranded chains. Evidence for the formation of fibrinogen-fibrin monomer complexes is also inferred from the time dependence of the mass/length ratio. However, our data are also compatible with the presence of limited amounts of single-stranded structures in the very early stages, either as a secondary, less populated pathway, or as transient intermediates to the classical double-stranded fibrils.

Chromatography, High Pressure Liquid↗
PubMed2003

Force generation by actin polymerization II: the elastic ratchet and tethered filaments.

The motion of many intracellular pathogens is driven by the polymerization of actin filaments. The propulsive force developed by the polymerization process is thought to arise from the thermal motions of the polymerizing filament tips. Recent experiments suggest that the nucleation of actin filaments involves a phase when the filaments are attached to the pathogen surface by a protein complex. Here we extend the "elastic ratchet model" of Mogilner and Oster to incorporate these new findings. We apply this "tethered ratchet" model to derive the force-velocity relation for Listeria and discuss relations of our theoretical predictions to experimental measurements. We also discuss "symmetry breaking" dynamics observed in ActA-coated bead experiments, and the implications of the model for lamellipodial protrusion in migrating cells.

Actins↗
PubMed1999

Surface-induced polymerization of actin.

Living cells contain a very large amount of membrane surface area, which potentially influences the direction, the kinetics, and the localization of biochemical reactions. This paper quantitatively evaluates the possibility that a lipid monolayer can adsorb actin from a nonpolymerizing solution, induce its polymerization, and form a 2D network of individual actin filaments, in conditions that forbid bulk polymerization. G- and F-actin solutions were studied beneath saturated Langmuir monolayers containing phosphatidylcholine (PC, neutral) and stearylamine (SA, a positively charged surfactant) at PC:SA = 3:1 molar ratio. Ellipsometry, tensiometry, shear elastic measurements, electron microscopy, and dark-field light microscopy were used to characterize the adsorption kinetics and the interfacial polymerization of actin. In all cases studied, actin follows a monoexponential reaction-limited adsorption with similar time constants (approximately 10(3) s). At a longer time scale the shear elasticity of the monomeric actin adsorbate increases only in the presence of lipids, to a 2D shear elastic modulus of mu approximately 30 mN/m, indicating the formation of a structure coupled to the monolayer. Electron microscopy shows the formation of a 2D network of actin filaments at the PC:SA surface, and several arguments strongly suggest that this network is indeed causing the observed elasticity. Adsorption of F-actin to PC:SA leads more quickly to a slightly more rigid interface with a modulus of mu approximately 50 mN/m.

Actins↗