scholarly journals Development of Novel and Highly Specific ssDNA-Aptamer-Based Electrochemical Biosensor for Rapid Detection of Mercury (II) and Lead (II) Ions in Water

Chemosensors ◽  
2019 ◽  
Vol 7 (2) ◽  
pp. 27 ◽  
Author(s):  
Hisham Abu-Ali ◽  
Alexei Nabok ◽  
Thomas Smith
Keyword(s):  
Rapid Detection ◽  
Electrochemical Biosensor ◽  
High Specificity ◽  
Thiol Groups ◽  
Buffer Solutions ◽  
Affinity Constants ◽  
Wide Range ◽  
Ssdna Aptamer ◽  
Redox Label ◽  
Kinetics Of

In this work, we report on the development of an electrochemical biosensor for high selectivity and rapid detection of Hg2+ and Pb2+ ions using DNA-based specific aptamer probes labeled with ferrocene (or methylene blue) and thiol groups at their 5′ and 3′ termini, respectively. Aptamers were immobilized onto the surface of screen-printed gold electrodes via the SH (thiol) groups, and then cyclic voltammetry and impedance spectra measurements were performed in buffer solutions with the addition of HgCl2 and PbCl2 salts at different concentrations. Changes in 3D conformation of aptamers, caused by binding their respective targets, e.g., Hg2+ and Pb2+ ions, were accompanied by an increase in the electron transfer between the redox label and the electrode. Accordingly, the presence of the above ions can be detected electrochemically. The detection of Hg2+ and Pb2+ ions in a wide range of concentrations as low as 0.1 ng/mL (or 0.1 ppb) was achieved. The study of the kinetics of aptamer/heavy metal ions binding gave the values of the affinity constants of approximately 9.10−7 mol, which proved the high specificity of the aptamers used.

Scintigraphic studies in rats. Kinetics of insulin analogues covering wide range of receptor affinities

Diabetes ◽  
1991 ◽  
Vol 40 (5) ◽  
pp. 628-632 ◽  
Author(s):  
I. Jensen ◽  
V. Kruse ◽  
U. D. Larsen
Keyword(s):  
Insulin Analogues ◽  
Wide Range ◽  
Kinetics Of

scholarly journals SARS-CoV-2 specific antibody and neutralization assays reveal the wide range of the humoral immune response to virus

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Mikail Dogan ◽  
Lina Kozhaya ◽  
Lindsey Placek ◽  
Courtney Gunter ◽  
Mesut Yigit ◽  
...  
Keyword(s):  
Specific Antibody ◽  
Neutralizing Antibodies ◽  
Vaccine Development ◽  
High Specificity ◽  
Spike Protein ◽  
Humoral Immune ◽  
Specificity And Sensitivity ◽  
Wide Range ◽  
Specific Igg ◽  
Negative Controls

AbstractDevelopment of antibody protection during SARS-CoV-2 infection is a pressing question for public health and for vaccine development. We developed highly sensitive SARS-CoV-2-specific antibody and neutralization assays. SARS-CoV-2 Spike protein or Nucleocapsid protein specific IgG antibodies at titers more than 1:100,000 were detectable in all PCR+ subjects (n = 115) and were absent in the negative controls. Other isotype antibodies (IgA, IgG1-4) were also detected. SARS-CoV-2 neutralization was determined in COVID-19 and convalescent plasma at up to 10,000-fold dilution, using Spike protein pseudotyped lentiviruses, which were also blocked by neutralizing antibodies (NAbs). Hospitalized patients had up to 3000-fold higher antibody and neutralization titers compared to outpatients or convalescent plasma donors. Interestingly, some COVID-19 patients also possessed NAbs against SARS-CoV Spike protein pseudovirus. Together these results demonstrate the high specificity and sensitivity of our assays, which may impact understanding the quality or duration of the antibody response during COVID-19 and in determining the effectiveness of potential vaccines.

scholarly journals Aptamer-based electrochemical biosensor for rapid detection of SARS-CoV-2: Nanoscale electrode-aptamer-SARS-CoV-2 imaging by photo-induced force microscopy

2021 ◽  
pp. 113595
Author(s):  
Juan Carlos Abrego-Martinez ◽  
Maziar Jafari ◽  
Siham Chergui ◽  
Catalin Pavel ◽  
Diping Che ◽  
...  
Keyword(s):  
Rapid Detection ◽  
Electrochemical Biosensor ◽  
Force Microscopy

scholarly journals Combining experimental and simulation data of molecular processes via augmented Markov models

2017 ◽  
Vol 114 (31) ◽  
pp. 8265-8270 ◽  
Author(s):  
Simon Olsson ◽  
Hao Wu ◽  
Fabian Paul ◽  
Cecilia Clementi ◽  
Frank Noé
Keyword(s):  
Force Field ◽  
Structural Changes ◽  
Markov Models ◽  
Force Fields ◽  
Divide And Conquer ◽  
Simulation Data ◽  
Wide Range ◽  
Simulation And Experiment ◽  
Kinetics Of

Accurate mechanistic description of structural changes in biomolecules is an increasingly important topic in structural and chemical biology. Markov models have emerged as a powerful way to approximate the molecular kinetics of large biomolecules while keeping full structural resolution in a divide-and-conquer fashion. However, the accuracy of these models is limited by that of the force fields used to generate the underlying molecular dynamics (MD) simulation data. Whereas the quality of classical MD force fields has improved significantly in recent years, remaining errors in the Boltzmann weights are still on the order of a few kT, which may lead to significant discrepancies when comparing to experimentally measured rates or state populations. Here we take the view that simulations using a sufficiently good force-field sample conformations that are valid but have inaccurate weights, yet these weights may be made accurate by incorporating experimental data a posteriori. To do so, we propose augmented Markov models (AMMs), an approach that combines concepts from probability theory and information theory to consistently treat systematic force-field error and statistical errors in simulation and experiment. Our results demonstrate that AMMs can reconcile conflicting results for protein mechanisms obtained by different force fields and correct for a wide range of stationary and dynamical observables even when only equilibrium measurements are incorporated into the estimation process. This approach constitutes a unique avenue to combine experiment and computation into integrative models of biomolecular structure and dynamics.

scholarly journals Isothermal and non-isothermal kinetics of hydrolysis of 1-[2-(2- pentyloxyphenylcarbamoyloxy)-(2-methoxymethyl)-ethyl]- perhydroazepinium chloride (BK 129)

2013 ◽  
Vol 60 (2) ◽  
pp. 43-48
Author(s):  
Stankovičová M. ◽  
Bezáková Ž. ◽  
Beňo P. ◽  
Húšťavová P.
Keyword(s):  
Biological Activity ◽  
Alkaline Hydrolysis ◽  
Functional Group ◽  
Isothermal Kinetics ◽  
Basic Part ◽  
Buffer Solutions ◽  
Kinetics Of Hydrolysis ◽  
Short Time ◽  
Kinetics Of ◽  
Hydrolysis Of

Abstract The substance BK 129 - 1-[2-(2-pentyloxyphenylcarbamoyloxy)-(2-methoxymethyl)-ethyl]-perhydroazepinium chloride was prepared in terms of influence of the connecting chain between the carbamate functional group and the basic part of molecule on biological activity. Such a structural feature is important with regard to its stability. In this work we determined the rate constants of alkaline hydrolysis of this compound at increased temperature under isothermal and non-isothermal conditions. The hydrolysis was also performed in buffer solutions with the purpose of evaluating its stability. Non-isothermal tests of stability enable to reduce the number of analyses. The necessary data for stability of compound are in this way achieved in a short time.

scholarly journals Positive co-operative binding at two weak lysine-binding sites governs the Glu-plasminogen conformational change

1992 ◽  
Vol 285 (2) ◽  
pp. 419-425 ◽  
Author(s):  
U Christensen ◽  
L Mølgaard
Keyword(s):  
Ligand Binding ◽  
Binding Site ◽  
Conformational Change ◽  
Conformational Changes ◽  
Binding Sites ◽  
High Specificity ◽  
Stopped Flow ◽  
Protein Fluorescence ◽  
Lysine Residues ◽  
Kinetics Of

The kinetics of a series of Glu-plasminogen ligand-binding processes were investigated at pH 7.8 and 25 degrees C (in 0.1 M-NaCl). The ligands include compounds analogous to C-terminal lysine residues and to normal lysine residues. Changes of the Glu-plasminogen protein fluorescence were measured in a stopped-flow instrument as a function of time after rapid mixing of Glu-plasminogen and ligand at various concentrations. Large positive fluorescence changes (approximately 10%) accompany the ligand-induced conformational changes of Glu-plasminogen resulting from binding at weak lysine-binding sites. Detailed studies of the concentration-dependencies of the equilibrium signals and the rate constants of the process induced by various ligands showed the conformational change to involve two sites in a concerted positive co-operative process with three steps: (i) binding of a ligand at a very weak lysine-binding site that preferentially, but not exclusively, binds C-terminal-type lysine ligands, (ii) the rate-determining actual-conformational-change step and (iii) binding of one more lysine ligand at a second weak lysine-binding site that then binds the ligand more tightly. Further, totally independent initial small negative fluorescence changes (approximately 2-4%) corresponding to binding at the strong lysine-binding site of kringle 1 [Sottrup-Jensen, Claeys, Zajdel, Petersen & Magnusson (1978) Prog. Chem. Fibrinolysis Thrombolysis 3, 191-209] were observed for the C-terminal-type ligands. The finding that the conformational change in Glu-plasminogen involves two weak lysine-binding sites indicates that the effect cannot be assigned to any single kringle and that the problem of whether kringle 4 or kringle 5 is responsible for the process resolves itself. Probably kringle 4 and 5 are both participating. The involvement of two lysine binding-sites further makes the high specificity of Glu-plasminogen effectors more conceivable.

scholarly journals Non-Isothermal Crystallisation Kinetics of Polypropylene at High Cooling Rates and Comparison to the Continuous Two-Domain pvT Model

Polymers ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1515
Author(s):  
Jonathan Alms ◽  
Christian Hopmann ◽  
Jian Wang ◽  
Tobias Hohlweck
Keyword(s):  
Injection Moulding ◽  
Polymer Processing ◽  
Nucleation And Growth ◽  
Growth Theory ◽  
Crystallisation Kinetics ◽  
Cooling Rates ◽  
Dsc Measurements ◽  
Wide Range ◽  
High Cooling Rates ◽  
Kinetics Of

The modelling of the correlation between pressure, specific volume and temperature (pvT) of polymers is highly important for applications in the polymer processing of semi-crystalline thermoplastics, especially in injection moulding. In injection moulding, the polymer experiences a wide range of cooling rates, for example, 60 °C/min near the centre of the part and up to 3000 °C/min near the mould walls. The cooling rate has a high influence on the pvT behaviour, as was shown in the continuous two-domain pvT model (CTD). This work examined the Hoffman–Lauritzen nucleation and growth theory used in the modified Hammami model for extremely high cooling rates (up to 300,000 °C/min) by means of Flash differential scanning calorimeter (DSC) measurements. The results were compared to those of the empirical continuous two-domain pvT model. It is shown that the Hammami model is not suitable to predict the crystallisation kinetics of polypropylene at cooling rates above 600 °C/min, but that the continuous two-domain pvT model is well able to predict crystallisation temperatures at high cooling rates.

scholarly journals Automated System for Kinetic Analysis of Particle Size Distributions for Pharmaceutically Relevant Systems

2014 ◽  
Vol 2014 ◽  
pp. 1-8
Author(s):  
John-Bruce D. Green ◽  
Phillip W. Carter ◽  
Yingqing Zhang ◽  
Dipa Patel ◽  
Priyanka Kotha ◽  
...  
Keyword(s):  
Particle Size ◽  
Clinical Importance ◽  
Automated System ◽  
Size Distributions ◽  
Mixing Conditions ◽  
Particle Size Distributions ◽  
Complex Formulation ◽  
Wide Range ◽  
Key Variables ◽  
Kinetics Of

Detailing the kinetics of particle formation for pharmaceutically relevant solutions is challenging, especially when considering the combination of formulations, containers, and timescales of clinical importance. This paper describes a method for using commercial software Automate with a stream-selector valve capable of sampling container solutions from within an environmental chamber. The tool was built to monitor changes in particle size distributions via instrumental particle counters but can be adapted to other solution-based sensors. The tool and methodology were demonstrated to be highly effective for measuring dynamic changes in emulsion globule distributions as a function of storage and mixing conditions important for parenteral nutrition. Higher levels of agitation induced the fastest growth of large globules (≥5 μm) while the gentler conditions actually showed a decrease in the number of these large globules. The same methodology recorded calcium phosphate precipitation kinetics as a function of [Ca2+] and pH. This automated system is readily adaptable to a wide range of pharmaceutically relevant systems where the particle size is expected to vary with time. This instrumentation can dramatically reduce the time and resources needed to probe complex formulation issues while providing new insights for monitoring the kinetics as a function of key variables.

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