scholarly journals Interaction of uranium(VI) towards glutathione – an example to study different functional groups in one molecule

2011 ◽  
Vol 1 (1) ◽  
pp. 357-362
Author(s):  
L. Frost ◽  
Gerhard Geipel ◽  
K. Viehweger ◽  
G. Bernhard
Keyword(s):  
Stability Constant ◽  
Fluorescence Spectroscopy ◽  
Thiol Group ◽  
Spectroscopic Properties ◽  
Laser Fluorescence ◽  
Fluorescent Label ◽  
Binding Potential ◽  
Complex Stability ◽  
Vis Spectroscopy ◽  
The Stability

Abstract Glutathione, the most abundant thiol compound of the cell, has a great binding potential towards heavy metal ions. Hence it might influence the distribution of actinides on a cellular level. The unknown strength of the interaction of uranium(VI) with glutathione at physiologically relevant pH is subject of this paper and was studied with UV-vis spectroscopy and time-resolved laser-induced fluorescence spectroscopy (TRLFS). The complex stability constant of UO2H2GS+, logβ 0 121, was calculated to be 39.09 ± 0.15 and 39.04 ± 0.02 in case of UV-vis spectroscopy and TRLFS respectively. Therefore the average formation constant for UO2 2+ + H2GS− = UO2H2GS+ can be assigned to be log K 0 11 = 19.83 ± 0.15. Furthermore it was demonstrated that derivatization of the ligand associated with an enhancement of the ligand's spectroscopic properties can be used for the determination of complex stability constants and to assess the coordination chemistry in more detail. Using UV-vis spectroscopy, the stability constant of the complex between UO2 2+ and glutathione pyruvate S-conjugate, a well absorbing ligand in contrast to glutathione, was calculated to be >39.24 ± 0.08. Furthermore the interaction of UO2 2+ with glutathione derivatized with the fluorescent label monobromobimane was examined with femtosecond laser fluorescence spectroscopy. Thereby the stability constant of the 1:1 complex was determined to be >39.35 ± 0.02. Although the thiol group of glutathione was blocked a strong coordination was found. Thus a significant involvement of the thiol group in the coordination of U(VI) can be excluded.

scholarly journals Binding of proteinases to human α2-macroglobulin with its thioester bonds cleaved by methylamine in the presence of a thiol-group-cyanylating reagent

1985 ◽  
Vol 231 (2) ◽  
pp. 451-457 ◽  
Author(s):  
I Björk
Keyword(s):  
Conformational Change ◽  
Major Change ◽  
Thiol Group ◽  
Spectroscopic Properties ◽  
Structural Features ◽  
Bait Region ◽  
Α2 Macroglobulin ◽  
Bean Trypsin Inhibitor ◽  
Similar Mode ◽  
The Stability

After cleavage of the thioester bonds of human alpha 2-macroglobulin (alpha 2M) by methylamine, the inhibitor undergoes an extensive conformational change and loses its ability to bind proteinases. In contrast, similar cleavage in the presence of dinitrophenyl thiocyanate, a reagent that cyanylates the liberated thiol groups, does not change the mobility of alpha 2M in gel electrophoresis, and the inhibitor also retains activity [Van Leuven, Marynen, Cassiman & Van den Berghe (1982) Biochem. J. 203, 405-411]. Analyses in this work show that also the spectroscopic properties of alpha 2M are essentially unperturbed under these conditions. These observations are consistent with the major change of the conformation of the protein having been arrested by the cyanylation reaction. However, several functional properties of the protein are altered, indicating that a limited conformational change does occur. The apparent stoichiometry of binding of trypsin is thus decreased to about 0.5 mol of enzyme/mol of alpha 2M. Nevertheless trypsin induces a similar conformational change in all molecules of the modified inhibitor as that induced in untreated alpha 2M. This behaviour indicates a similar mode of binding of the enzyme to the modified alpha 2M as to intact alpha 2M, but also a high extent of non-productive activation of binding sites in the modified inhibitor. A further difference to untreated alpha 2M is that most of the bound trypsin molecules react considerably faster with soya-bean trypsin inhibitor. The rate of inhibition of thrombin is also greatly decreased, and the modified inhibitor is more sensitive than untreated alpha 2M to proteolysis at sites outside the ‘bait’ region. The properties of the cyanylated human alpha 2M are thus similar to those of bovine alpha 2M in which the thioester bonds have been cleaved by methylamine in the absence of the cyanylating reagent [Björk, Lindblom & Lindahl (1985) Biochemistry 24, 2653-2660]. These results indicate that the thioester bonds of human and bovine alpha 2M are not required as such for the stability of the gross conformation of the protein or for the binding of proteinases. Nevertheless they participate directly in maintaining certain structural features, similar in the two inhibitors, that are necessary for full proteinase-binding ability. Disruption of these structures leads to a slower and less efficient trapping of the enzymes.

Synthesis and solvatochromic studies of 2- amino-3-phenolazo1-(4-sulfophenyl)-3-methyi-5-pyrozolone and use it for the determination of trace amount of Nickel (II) in blood samples

2016 ◽  
Vol 5 (10) ◽  
pp. 4920
Author(s):  
Amar M. Ali ◽  
Hussain. J. Mohammed*
Keyword(s):  
Stability Constant ◽  
Trace Amount ◽  
Benzenesulfonic Acid ◽  
Determination Method ◽  
Blood Samples ◽  
Determination Of Nickel ◽  
Normal Human ◽  
The Stability ◽  
Normal Human Blood

A new, simple, sensitive and rapid spectrophotometric method is proposed for the determination of trace amount of Nickel (II). The method is based on the formation of a 1:2 complex with 4-(4-((2-hydroxy-6-nitrophenyl) diazenyl) -3-methyl-5-oxo-2, 5-dihydro-1H-pyrazol-1-yl) benzenesulfonic acid (2-ANASP) as a new reagent is developed. The complex has a maximum absorption at 516 nm and εmax of 1. 84 X 105 L. mol-1. cm-1. A linear correlation (0. 25 – 4. 0μg. ml-1) was found between absorbance at λmax and concentration. The accuracy and reproducibility of the determination method for various known amounts of Nickel (II) were tested. The results obtained are both precise (RSD was 1. 2 %) and accurate (relative error was 0. 787 %). The effect of diverse ions on the determination of Nickel (II) to investigate the selectivity of the method were also studied. The stability constant of the product was 0. 399 X 106 L. mol-1. The proposed method was successfully applied to the analysis of diabetes blood and normal human blood. 

scholarly journals Antimicrobial Activity of Cationic Poly(3-hexylthiophene) Nanoparticles Coupled with Dual Fluorescent and Electrochemical Sensing: Theragnostic Prospect

Sensors ◽  
2021 ◽  
Vol 21 (5) ◽  
pp. 1715
Author(s):  
Nada Elgiddawy ◽  
Shiwei Ren ◽  
Wadih Ghattas ◽  
Waleed M. A. El Rouby ◽  
Ahmed O. El-Gendy ◽  
...  
Keyword(s):  
Antimicrobial Activity ◽  
Fluorescence Spectroscopy ◽  
Bacterial Infections ◽  
Electrochemical Impedance ◽  
Spectroscopic Properties ◽  
Electrochemical Sensing ◽  
E Coli ◽  
Normal Human ◽  
Dual Detection ◽  
Bacteria And Fungi

Designing therapeutic and sensor materials to diagnose and eliminate bacterial infections remains a significant challenge for active theragnostic nanoprobes. In the present work, fluorescent/electroactive poly(3-hexylthiophene) P3HT nanoparticles (NPs) stabilized with quaternary ammonium salts using cetyltrimethylammonium bromide (CTAB), (CTAB-P3HT NPs) were prepared using a simple mini-emulsion method. The morphology, spectroscopic properties and electronic properties of CTAB-P3HT NPs were characterized by DLS, zeta potential, SEM, TEM, UV-vis spectrophotometry, fluorescence spectroscopy and electrochemical impedance spectroscopy (EIS). In an aqueous solution, CTAB-P3HT NPs were revealed to be uniformly sized, highly fluorescent and present a highly positively charged NP surface with good electroactivity. Dual detection was demonstrated as the binding of the bacteria to NPs could be observed by fluorescence quenching as well as by the changes in EIS. Binding of E. coli to CTAB-P3HT NPs was demonstrated and LODs of 5 CFU/mL and 250 CFU/mL were obtained by relying on the fluorescence spectroscopy and EIS, respectively. The antimicrobial activity of CTAB-P3HT NPs on bacteria and fungi was also studied under dark and nutritive conditions. An MIC and an MBC of 2.5 µg/mL were obtained with E. coli and with S. aureus, and of 0.312 µg/mL with C. albicans. Additionally a good biocompatibility toward normal human cells (WI38) was observed, which opens the way to their possible use as a therapeutic agent.

scholarly journals Investigations of ternary complexes of Co(II) and Ni(II) with thiodiacetate anion and 1,10-phenanthroline or 2,2’-bipyridine in aqueous solutions

2014 ◽  
Vol 13 (1) ◽  
Author(s):  
Dariusz Wyrzykowski ◽  
Joanna Pranczk ◽  
Dagmara Jacewicz ◽  
Aleksandra Tesmar ◽  
Bogusław Pilarski ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Substitution Reactions ◽  
Experimental Conditions ◽  
Kinetic Measurements ◽  
Hydroxo Complexes ◽  
Binary Complexes ◽  
Vis Spectroscopy ◽  
Potentiometric Titration Method ◽  
The Stability ◽  
Ph Range

AbstractA potentiometric titration method (PT) and a stopped-flow kinetic technique monitored by a UV−Vis spectroscopy have been used to characterize the stability of series of Co(II)- and Ni(II)-thiodiacetato complexes, M(TDA), in the presence of 1,10-phenanthroline (phen) or 2,2’-bipyridine (bipy) in aqueous solutions. The stability constants of the binary (1:1), ternary (1:1:1) as well as the resulting hydroxo complexes were evaluated and compared to the corresponding oxydiacetate complexes. Based on the species distribution as a function of pH the relative predominance of the species in the system over a pH range was discussed. Furthermore, the kinetic measurements of the substitution reactions of the aqua ligands to phen or bipy in the coordination sphere of the binary complexes M(TDA) were performed in the 288–303 K temperature range, at a constant concentration of phen or bipy and at seven different concentrations of the binary complexes (0.2–0.5 mM). The kinetic stability of the M(TDA) complexes was discussed in relation to the experimental conditions and the kind of the auxiliary ligands (phen/bipy). Moreover, the influence of the type of primary ligand (thiodiacetate/oxydiacetate) on the substitution rate of the auxiliary ligands was also compared.

Comparative characterisation of two fulvic acids from East Lake and Liangzi Lake in central China

2015 ◽  
Vol 12 (2) ◽  
pp. 189 ◽  
Author(s):  
Jun Wang ◽  
Huijie Li ◽  
Yong Chen ◽  
Yuan Fang ◽  
Zongping Wang ◽  
...  
Keyword(s):  
Fluorescence Spectroscopy ◽  
Cost Effective ◽  
Fulvic Acids ◽  
Central China ◽  
Anthropogenic Activity ◽  
Cost Effective Method ◽  
Vis Spectroscopy ◽  
East Lake ◽  
Ft Ir ◽  
Eem Fluorescence

Environmental context Fulvic acids account for a large proportion of dissolved organic matter in aquatic environments and affect the transportation and bioavailability of organic and inorganic pollutants. The structural and spectroscopic characteristics of fulvic acids mainly depend on the sources, seasons and anthropogenic activity. We present an advanced approach using fluorescence spectroscopy as a rapid and cost-effective method to investigate the composition, properties and origins of fulvic acids. Abstract Fulvic acids (FAs) isolated seasonally from the sediments of East Lake and Liangzi Lake in central China were comparatively investigated. The structural features of the FAs were characterised using chemical and spectroscopic methods, including elemental analysis, UV-Vis spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy, and three-dimensional excitation emission matrix (EEM) fluorescence spectroscopy coupled with parallel factor analysis (PARAFAC). The O/C, (O+N)/C and C/N ratios of FA extracted from Liangzi Lake (FAL) were higher than those of FA extracted from East Lake (FAE), indicating higher oxygen-containing functionality and polarity and less nutrient in FAL compared with FAE. The two FAs had similar UV-Vis spectra with different absorbance intensities. The FT-IR spectra showed that the two FAs had similar functional groups. The total fluorescence intensity and aromaticity of samples from Liangzi Lake were higher than those of East Lake except for those taken in the summer. The two FAs were largely terrestrially derived organic materials. Five fluorescent components, including four humic-like and two fulvic-like components, were identified by PARAFAC modelling of the EEM spectral data. The fluorescence was dominated by two components. The findings suggest that EEM fluorescence spectroscopy together with PARAFAC is a rapid and cost-effective method for understanding the characteristics and origins of FAs in natural water systems.

scholarly journals UV-VIS spectroscopy for monitoring yogurt stability during storage time

2016 ◽  
Vol 8 (30) ◽  
pp. 5962-5969 ◽  
Author(s):  
B. Aliakbarian ◽  
L. Bagnasco ◽  
P. Perego ◽  
R. Leardi ◽  
M. Casale
Keyword(s):  
Storage Time ◽  
Dairy Product ◽  
Entire Period ◽  
Vis Spectroscopy ◽  
The Stability ◽  
Color Texture

Color, texture and taste are key elements of a consumer's buying decision; thus, monitoring the stability of these features throughout the entire period of yogurt validity is fundamental for dairy product producers.

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