Search results for "surface"
showing 10 items of 9345 documents
Surface Modified Arundo Donax Natural Fibers for Oil Spill Recovery
2021
The use of green materials for oil recovery applications is the goal to be achieved to reduce the environmental impact of these essential processes. In this context, Arundo Donax L. is a plant known for its wide uses whose absorbent properties have been previously investigated. In this paper, the influence of silane surface treatment on the absorbent behavior of natural fibers extracted from the culms of this eco-friendly and cost-effective material was assessed. A close correspondence has been identified between the physical characteristics of the investigated oil and the fiber size, by means of microstructural and morphological analysis. Excellent results have been achieved with an absorp…
Preorganization and reorganization as related factors in enzyme catalysis: the chorismate mutase case.
2003
In this paper a deeper insight into the chorismate-to prephenate-rearrangement, catalyzed by Bacillus subtilis chorismate mutase, is provided by means of a combination of statistical quantum mechanics/molecular mechanics simulation methods and hybrid potential energy surface exploration techniques. The main aim of this work is to present an estimation of the preorganization and reorganization terms of the enzyme catalytic rate enhancement. To analyze the first of these, we have studied different conformational equilibria of chorismate in aqueous solution and in the enzyme active site. Our conclusion is that chorismate mutase preferentially binds the reactive conformer of the substrate--that…
Recent advances of electrochemical and optical biosensors for detection of C-reactive protein as a major inflammatory biomarker
2020
Abstract Early detection of inflammatory mediators including C-reactive protein (CRP) is of great diagnostic importance in many human diseases. CRP elevates very fast in conditions such as tissue injuries, infections, cancers, and renal and cardiovascular diseases. Conventional techniques for detecting CRP are based on antigen–antibody, agglutination, and precipitation reactions. Newer methods based on immunoturbidimetry and immunonephelometry are also time-consuming and relatively expensive. For solving these problems, highly efficient techniques based on CRP-biosensors have been introduced. Here, our aim was to summarize the features of recent biosensors for detection of CRP in biological…
Seeking the Source of Catalytic Efficiency of Lindane Dehydrochlorinase, LinA.
2020
Herein we present the results of an in-depth simulation study of LinA and its two variants. In our analysis, we combined the exploration of protein conformational dynamics with and without bound substrates (hexachlorocyclohexane (HCH) isomers) performed using molecular dynamics simulation followed by the extraction of the most frequently visited conformations and their characteristics with a detailed description of the interactions taking place in the active site between the respective HCH molecule and the first shell residues by using symmetry-adapted perturbation theory (SAPT) calculations. A detailed investigation of the conformational space of LinA substates has been accompanied by desc…
The binding of G-protein to rod outer segment phospholipids at the nitrogen–water interface
1989
In the visual process, one photoexcited rhodopsin (R*) catalyzes the activation of hundreds of G-proteins. It remains to be determined whether G-protein and R* find one another by membrane surface diffusion of these components (diffusion model) or by diffusion of G-protein through the aqueous phase (hopping model). A monolayer of each main rod outer segment (ROS) phospholipid interacting with a subphase containing G-protein, has been used to simulate the interaction of G-protein with the cytoplasmic surface of discal membranes. The possible diffusion of G-protein through the aqueous phase was then measured by observing its adsorption–desorption in the monolayer of each main ROS phospholipi…
Charge Transfer Transitions in Neutral and Ionic Polypeptides: A Theoretical Study
2001
We report on the vertical electronic excitation spectra of neutral polypeptides and their radical ions. Model systems including tri-, tetra-, and octamers in an α-helix and β-sheet alike conformation are studied by various computational methods. The results allow us to assign the band centered at about 7.5 eV in the absoption spectra of proteins to charge transfer states. The calculations also support conclusions from recent experiments which propose charge transfer as a possible mechanism for photoinduced electron transfer in polypeptide cations.
Surface Modification of Porous Polyethylene Implants with an Albumin-Based Nanocarrier-Release System
2021
Background: Porous polyethylene (PPE) implants are used for the reconstruction of tissue defects but have a risk of rejection in case of insufficient ingrowth into the host tissue. Various growth factors can promote implant ingrowth, yet a long-term gradient is a prerequisite for the mediation of these effects. As modification of the implant surface with nanocarriers may facilitate a long-term gradient by sustained factor release, implants modified with crosslinked albumin nanocarriers were evaluated in vivo. Methods: Nanocarriers from murine serum albumin (MSA) were prepared by an inverse miniemulsion technique encapsulating either a low- or high-molar mass fluorescent cargo. PPE implants …
Application of Grote-Hynes theory to the reaction catalyzed by thymidylate synthase.
2010
A theoretical study of dynamic effects on the rate-limiting step of the thymidylate synthase catalyzed reaction has been carried out by means of Grote-Hynes theory, successfully predicting the values of the recrossing effects for a chemical reaction that involves the transfer of a classical light particle. The transmission coefficients, obtained at 278, 293, 303, and 313 K, are almost invariant and in all cases far from unity, revealing a significant coupling of the environment motions and the reaction coordinate. Nevertheless, their energetic contribution to the activation free energy represents less than 0.50 kcal/mol for each of the four tested temperatures. Calculation of the transmissi…
A remarkable selectivity in the N-functionalization of polyaza[n]paracyclophanes. Synthesis of N-(4-picolyl)-substituted 2,6,9,13-tetraaza[14]paracyc…
1997
Abstract Interaction of cationic host species, in particular Zn 2+ salts, with polyaza[n]paracyclophanes (i.e. 2,6,9,13-Tetraaza[14]paracyclophane, B323 (1a) ) directs their selective N-functionalization. In this way compounds mono- or difunctionalized with ArCH 2− groups at the benzylic nitrogen atoms can be easily obtained. Direct reaction with the alkylating agent, in the absence of the Zn 2+ species, produces, in general, very complex mixtures of mono- and polyalkylated compounds except when 4-picolyl chloride is used. In this case, mono-, di-, tri- and tetra N-substituted derivatives of D323 can be isolated depending on the amount of the alkylating agent used. In this case, the mono- a…
Force probe measurements of antibody-antigen interactions.
2000
The surface force apparatus has been used to quantify directly the forces that govern the interactions between proteins and ligands. In this work, we describe the measured interactions between the antigen fluorescein and the Fab' fragment of the monoclonal 4-4-20 anti-fluorescyl IgG antibody. Here we first describe the use of the surface force apparatus to demonstrate directly the impact of the charge composition in the region of the antibody binding site on the antibody interactions. Several approaches are described for immobilizing antigens, antibodies, and proteins in general for direct force measurements. The measured force profiles presented are accompanied by an extensive discussion o…