scholarly journals Oxygen- and pH-Dependent Photophysics of Fluorinated Fluorescein Derivatives: Non-Symmetrical vs. Symmetrical Fluorination

Sensors ◽  
2020 ◽  
Vol 20 (18) ◽  
pp. 5172
Author(s):  
Ciaran K. McLoughlin ◽  
Eleni Kotroni ◽  
Mikkel Bregnhøj ◽  
Georgios Rotas ◽  
Georgios C. Vougioukalakis ◽  
...  
Keyword(s):  
Singlet Oxygen ◽  
Fluorescent Probe ◽  
Fluorescent Probes ◽  
Wide Ph Range ◽  
Ph Dependent ◽  
Ph Range ◽  
Derivatives Of

Fluorescein, and derivatives of fluorescein, are often used as fluorescent probes and sensors. In systems where pH is a variable, protonation/deprotonation of the molecule can influence the pertinent photophysics. Fluorination of the xanthene moiety can alter the molecule’s pKa such as to render a probe whose photophysics remains invariant over a wide pH range. Di-fluorination is often sufficient to accomplish this goal, as has been demonstrated with compounds such as Oregon Green in which the xanthene moiety is symmetrically difluorinated. In this work, we synthesized a non-symmetrical difluorinated analog of Oregon Green which we call Athens Green. We ascertained that the photophysics and photochemistry of Athens Green, including the oxygen-dependent photophysics that results in the sensitized production of singlet oxygen, O2(a1Δg), can differ appreciably from the photophysics of Oregon Green. Our data indicate that Athens Green will be a more benign fluorescent probe in systems that involve the production and removal of O2(a1Δg). These results expand the available options in the toolbox of fluorescein-based fluorophores.

Use of bentonite to control the release of copper from contaminated soils

Soil Research ◽  
2007 ◽  
Vol 45 (8) ◽  
pp. 618 ◽  
Author(s):  
Wanting Ling ◽  
Qing Shen ◽  
Yanzheng Gao ◽  
Xiaohong Gu ◽  
Zhipeng Yang
Keyword(s):  
Heavy Metals ◽  
Sorption Capacity ◽  
Contaminated Soils ◽  
Montmorillonite Clay ◽  
Maximum Sorption Capacity ◽  
Maximum Sorption ◽  
Wide Ph Range ◽  
Ph Dependent ◽  
Ph Range ◽  
Soil Ageing

A decrease in release and availability of heavy metals in soil has been of worldwide interest in recent years. Bentonite is a type of expandable montmorillonite clay, and has strong sorption for heavy metals. In this work, the control of amended bentonite on the release of copper (Cu2+) from spiked soils was investigated using a batch equilibrium technique. Sorption of Cu by bentonite was pH-dependent, and could be well described using the Langmiur model. Maximum sorption capacity of the bentonite used in this study was 5.4 mg/g, which was much greater than soils reported in the literature. The extent of Cu2+ release from spiked soils was correlated with slurry concentrations, pH, and soil ageing process. In all cases, the amendment of bentonite was observed to effectively decrease the release of Cu2+ from soils. The apparent aqueous concentrations of Cu2+ released from soils devoid of bentonite treatment were 113–1160% higher than those from the soils amended with bentonite. Moreover, the magnitude of Cu2+ release decreased with increasing amount of bentonite added to soils. The bentonite added was more effective in retaining Cu2+ in sorbents for aged contaminated soils. Such enhanced retention resulting from the presence of bentonite was observed within a wide pH range from 2.5 to 7.0. Bentonite, as one of the most abundant minerals in soils, is regarded to improve the soil overall quality. The results obtained from this work provide useful information on utilisation of bentonite to control the release of heavy metals from contaminated soils.

A novel fluorescent probe for Hg2+ detection in a wide pH range and its application in living cell imaging

2018 ◽  
Vol 10 (46) ◽  
pp. 5554-5558 ◽  
Author(s):  
Jing Xu ◽  
Honglin Li ◽  
Yanchi Chen ◽  
Bing Yang ◽  
Qingcai Jiao ◽  
...  
Keyword(s):  
Amino Acids ◽  
Metal Ions ◽  
Fluorescent Probe ◽  
Living Cell ◽  
Cell Imaging ◽  
Enhanced Fluorescence ◽  
Wide Ph Range ◽  
Ph Range ◽  
Living Cell Imaging

A novel fluorescent probe (XL-1) exhibited over 50-fold enhanced fluorescence in the presence of Hg2+ and no interference could be produced by other metal ions, anions and amino acids.

THE POLAROGRAPHY OF THE METHYL DERIVATIVES OF MALEIC HYDRAZIDE AND EXPLANATION OF THE MALEIC HYDRAZIDE WAVES

1956 ◽  
Vol 34 (12) ◽  
pp. 1760-1767 ◽  
Author(s):  
D. M. Miller
Keyword(s):  
Maleic Hydrazide ◽  
Low Ph ◽  
Adequate Explanation ◽  
Quantitative Expression ◽  
Half Wave ◽  
Methyl Derivatives ◽  
Ph Dependent ◽  
Ph Range ◽  
Derivatives Of

Maleic hydrazide was previously reported to have two sets of pH dependent double waves, one at low pH for which existing theories provide adequate explanation and one at higher pH for which no explanation has been offered to date. The present work is an attempt to discover the reasons for the existence of the second set of waves. An investigation of several methyl derivatives of maleic hydrazide failed to provide the desired explanation; however, a mechanism which gives a good qualitative and approximately quantitative expression for the dependence of diffusion currents and half wave potentials on pH is offered. This theory is based on the fact that succinic hydrazide, a probable product of the reduction of maleic hydrazide, has been found to have a pKa of 8.10 and thus to be present in both ionized and unionized forms over the pH range for which the double waves occur.

Effect of pH on the cation exchange capacity of some halloysite nanotubes

Clay Minerals ◽  
2016 ◽  
Vol 51 (3) ◽  
pp. 373-383 ◽  
Author(s):  
Nia Gray ◽  
David G. Lumsdon ◽  
Stephen Hillier
Keyword(s):  
Cation Exchange ◽  
Cation Exchange Capacity ◽  
Halloysite Nanotubes ◽  
Exchange Capacity ◽  
Average Value ◽  
Two Samples ◽  
Wide Ph Range ◽  
Capacitance Model ◽  
Ph Dependent ◽  
Ph Range

AbstractThe cation exchange capacity (CEC) of seven well characterized halloysite nanotubes (HNTs) in the dehydrated 7 Å form has been measured using a method based on cobalt hexammine exchange. In addition to unbuffered measurements, which varied between 2.9 and 9.3 cmol(+)kg−1, CECs were also determined over a wide pH range and proton titration measurements were conducted on two samples. The data were fitted using a constant capacitance model based on the presence of two sites: permanently charged sites and pH-dependent variable charged sites. Normalization of CEC to the average specific surface area (BET) of the halloysite samples reduces considerably the variation of CEC values for the different samples particularly over the intermediate pH range (5–9) with the average value at pH 7 equal to 8.5 cmol(+)kg−1and a standard deviation of 1.17. Overall the CEC behaviour of the seven samples appears reasonably consistent throughout the set. Calculations based on proton titrations suggest a ratio of variable charge to basal sites for the dehydrated halloysite nanotubes of ∼3:1.

Water-soluble gold nanoclusters with pH-dependent fluorescence and high colloidal stability over a wide pH range via co-reduction of glutathione and citrate

RSC Advances ◽  
2014 ◽  
Vol 4 (43) ◽  
pp. 22651-22659 ◽  
Author(s):  
Wenchao Ding ◽  
Yong Liu ◽  
Yijing Li ◽  
Qiurong Shi ◽  
Houshen Li ◽  
...  
Keyword(s):  
Fluorescence Intensity ◽  
Colloidal Stability ◽  
Gold Nanoclusters ◽  
Water Soluble ◽  
Simple Strategy ◽  
Wide Ph Range ◽  
Ph Dependent ◽  
Ph Range ◽  
Co Reduction

We present a simple strategy for synthesis of water-soluble, monodisperse, highly fluorescent gold nanoclusters (Au NCs) with sizes of 1.8 nm by co-reduction of glutathione and citrate for 24 h at 50 °C. The fluorescence intensity of the GS/C–Au NCs obtained is pH-dependent and can be reversibly adjusted in the pH range from 4.1 to 8.6.

A novel NhaD-type Na+/H+ antiporter from the moderate halophile and alkaliphile Halomonas alkaliphila

2017 ◽  
Vol 63 (7) ◽  
pp. 596-607 ◽  
Author(s):  
Yanhong Wang ◽  
Na Song ◽  
Lina Yang ◽  
Heba Abdel-motaal ◽  
Rui Zhang ◽  
...  
Keyword(s):  
Membrane Vesicles ◽  
Activity Profile ◽  
Moderate Halophile ◽  
E Coli ◽  
Significant Difference ◽  
Dependent Activity ◽  
Wide Ph Range ◽  
Ph Dependent ◽  
Ph Range ◽  
Selection Of

In this study, a NhaD-type Na+/H+ antiporter gene designated Ha-nhaD was obtained by selection of genomic DNA from the moderate halophile and alkaliphile Halomonas alkaliphila in Escherichia coli KNabc lacking 3 major Na+/H+ antiporters. The presence of Ha-NhaD conferred tolerance of E. coli KNabc to NaCl up to 0.6 mol·L–1 and to LiCl up to 0.2 mol·L–1 and to an alkaline pH. pH-dependent Na+(Li+)/H+ antiport activity was detected from everted membrane vesicles prepared from E. coli KNabc/pUC-nhaD but not those of KNabc/pUC18. Ha-NhaD exhibited Na+(Li+)/H+ antiport activity over a wide pH range from 7.0 to 9.5, with the highest activity at pH 9.0. Protein sequence alignment and phylogenetic analysis revealed that Ha-NhaD is significantly different from the 7 known NhaD-type Na+/H+ antiporters, including Dw-NhaD, Dl-NhaD, Vp-NhaD, Vc-NhaD, Aa-NhaD, He-NhaD, and Ha-NhaD1. Although Ha-NhaD showed a closer phylogenetic relationship with Ha-NhaD2, a significant difference in pH-dependent activity profile exists between Ha-NhaD and Ha-NhaD2. Taken together, Ha-nhaD encodes a novel pH-dependent NhaD-type Na+/H+ antiporter.

Development of an AIE based fluorescent probe for the detection of nitrate anions in aqueous solution over a wide pH range

RSC Advances ◽  
2016 ◽  
Vol 6 (9) ◽  
pp. 6997-7001 ◽  
Author(s):  
Shiyan Chen ◽  
Xin-Long Ni
Keyword(s):  
Aqueous Solution ◽  
Fluorescent Probe ◽  
Living Cells ◽  
Selective Detection ◽  
Ionic Interaction ◽  
Turn On ◽  
Wide Ph Range ◽  
New Type ◽  
Ph Range ◽  
Nitrate Anions

A new type of AIE-based turn-on fluorescent probe 1 was reported to highly selective detection of NO3− anion in aqueous solution and living cells by virtue of ionic interaction.

pH-Dependent Thermal Stability of Vibrio cholerae L-asparaginase

2019 ◽  
Vol 26 (10) ◽  
pp. 743-750 ◽  
Author(s):  
Remya Radha ◽  
Sathyanarayana N. Gummadi
Keyword(s):  
Vibrio Cholerae ◽  
Conformational Changes ◽  
Kinetic Studies ◽  
Structural Features ◽  
Structure Stability ◽  
Kcal Mole ◽  
Scanning Calorimetry ◽  
Wide Range ◽  
Ph Dependent ◽  
Ph Range

Background:pH is one of the decisive macromolecular properties of proteins that significantly affects enzyme structure, stability and reaction rate. Change in pH may protonate or deprotonate the side group of aminoacid residues in the protein, thereby resulting in changes in chemical and structural features. Hence studies on the kinetics of enzyme deactivation by pH are important for assessing the bio-functionality of industrial enzymes. L-asparaginase is one such important enzyme that has potent applications in cancer therapy and food industry.Objective:The objective of the study is to understand and analyze the influence of pH on deactivation and stability of Vibrio cholerae L-asparaginase.Methods:Kinetic studies were conducted to analyze the effect of pH on stability and deactivation of Vibrio cholerae L-asparaginase. Circular Dichroism (CD) and Differential Scanning Calorimetry (DSC) studies have been carried out to understand the pH-dependent conformational changes in the secondary structure of V. cholerae L-asparaginase.Results:The enzyme was found to be least stable at extreme acidic conditions (pH< 4.5) and exhibited a gradual increase in melting temperature from 40 to 81 °C within pH range of 4.0 to 7.0. Thermodynamic properties of protein were estimated and at pH 7.0 the protein exhibited ΔG37of 26.31 kcal mole-1, ΔH of 204.27 kcal mole-1 and ΔS of 574.06 cal mole-1 K-1.Conclusion:The stability and thermodynamic analysis revealed that V. cholerae L-asparaginase was highly stable over a wide range of pH, with the highest stability in the pH range of 5.0–7.0.

Polarographic and spectrophotometric behaviour of some N-p-phenyl substituted benzamidines

1991 ◽  
Vol 56 (12) ◽  
pp. 2791-2799 ◽  
Author(s):  
Juan A. Squella ◽  
Luis J. Nuñez-Vergara ◽  
Hernan Rodríguez ◽  
Amelia Márquez ◽  
Jose M. Rodríguez-Mellado ◽  
...  
Keyword(s):  
Spectrophotometric Study ◽  
Absorption Bands ◽  
Electrochemical Parameters ◽  
Wide Ph Range ◽  
Group A ◽  
Substituent Constants ◽  
Ph Range ◽  
The Waves

Five N-p-phenyl substituted benzamidines were studied by DC and DP polarography in a wide pH range. Coulometric results show that the overall processes are four-electron reductions. Logarithmic analysis of the waves indicate that the process are irreversible. The influence of the pH on the polarographic parameters was also studied. A UV spectrophotometric study was performed in the pH range 2-13. In basic media some variations in the absorption bands were observed due to the dissociation of the amidine group. A determination of the pK values was made by deconvolution of the spectra. Correlations of both the electrochemical parameters and spectrophotometric pK values with the Hammett substituent constants were obtained.

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