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Fluorescence patterns from supramolecular polymer assembly and disassembly for sensing metallo- and nonmetalloproteins.

ABSTRACT: Critical aggregation concentration (CAC) of surfactants is lowered when polyelectrolytes act as counterions. At a concentration in between the CACs of the surfactant and the polymer-surfactant complex, protein-induced disassemblies can be achieved. This is because, when proteins competitively bind to the polyelectrolytes, the surfactants are not capable of sustaining a micelle-type assembly at this concentration. Since these amphiphilic aggregates are capable of noncovalently sequestering hydrophobic guest molecules, the protein binding induced disassembly process also results in a guest release from these assemblies. We show here that the change in fluorescence with different proteins is dependent not only on the nature of the polymer-surfactant complex, but also on the fluorescent transducer. Two processes can be responsible for the observed fluorescence change: fluorophore guest release from the hydrophobic interior of the assembly and excited state quenching due to complementary components in the analyte. The latter mechanism is especially possible with metalloproteins. We show here that an excited state quenching is possible at nanomolar concentrations of the proteins, while the disassembly based fluorescence reduction is the dominant pathway at micromolar concentrations.

SUBMITTER: Gonzalez DC

PROVIDER: S-EPMC2736297 | biostudies-literature | 2009 Jun

REPOSITORIES: biostudies-literature

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Fluorescence patterns from supramolecular polymer assembly and disassembly for sensing metallo- and nonmetalloproteins.

González Daniella C DC Savariar Elamprakash N EN Thayumanavan S S

Journal of the American Chemical Society 20090601 22

Critical aggregation concentration (CAC) of surfactants is lowered when polyelectrolytes act as counterions. At a concentration in between the CACs of the surfactant and the polymer-surfactant complex, protein-induced disassemblies can be achieved. This is because, when proteins competitively bind to the polyelectrolytes, the surfactants are not capable of sustaining a micelle-type assembly at this concentration. Since these amphiphilic aggregates are capable of noncovalently sequestering hydrop ...[more]

PMID: 19435315

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Project description:The power of sensing molecules is often characterized in part by determining their thermodynamic/dynamic properties, in particular the binding constant of a guest to a host. In many studies, traditional nonlinear regression analysis has been used to determine the binding constants, which cannot be applied to complex systems and limits the reliability of such calculations. Supramolecular sensor systems include many interactions that make such chemical systems complicated. The challenges in creating sensing molecules can be significantly decreased through the availability of detailed mathematical models of such systems. Here, we propose uncovering accurate thermodynamic parameters of chemical reactions using better-defined mathematical modeling-fitting analysis is the key to understanding molecular assemblies and developing new bio/sensing agents. The supramolecular example we chose for this investigation is a self-assembled sensor consists of a synthesized receptor, DPA (DPA = dipicolylamine)-appended phenylboronic acid (1) in combination with Zn2+(1.Zn) that forms various assemblies with a fluorophore like alizarin red S (ARS). The self-assemblies can detect multi-phosphates like pyrophosphate (PPi) in aqueous solutions. We developed a mathematical model for the simultaneous quantitative analysis of twenty-seven intertwined interactions and reactions between the sensor (1.Zn-ARS) and the target (PPi) for the first time, relying on the Newton-Raphson algorithm. Through analyzing simulated potentiometric titration data, we describe the concurrent determination of thermodynamic parameters of the different guest-host bindings. Various values of temperatures, initial concentrations, and starting pHs were considered to predict the required measurement conditions for thermodynamic studies. Accordingly, we determined the species concentrations of different host-guest bindings in a generalized way. This way, the binding capabilities of a set of species can be quantitatively examined to systematically measure the power of the sensing system. This study shows analyzing supramolecular self-assemblies with solid mathematical models has a high potential for a better understanding of molecular interactions within complex chemical networks and developing new sensors with better sensing effects for bio-purposes.

Dataset Information

Fluorescence patterns from supramolecular polymer assembly and disassembly for sensing metallo- and nonmetalloproteins.

Publications

Fluorescence patterns from supramolecular polymer assembly and disassembly for sensing metallo- and nonmetalloproteins.

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