scholarly journals The Role of UV-Visible Spectroscopy for Phenolic Compounds Quantification in Winemaking

2019 ◽  
Author(s):  
Jose Luis Aleixandre-Tudo ◽  
Wessel du Toit
Keyword(s):  
Phenolic Compounds ◽  
Visible Spectroscopy ◽  
Uv Visible

scholarly journals The HA2 haemagglutinin domain of the lysine-specific gingipain (Kgp) of Porphyromonas gingivalis promotes μ-oxo bishaem formation from monomeric iron(III) protoporphyrin IX

Microbiology ◽  
2006 ◽  
Vol 152 (6) ◽  
pp. 1839-1845 ◽  
Author(s):  
J. W. Smalley ◽  
A. J. Birss ◽  
B. Szmigielski ◽  
J. Potempa
Keyword(s):  
Fourier Transform ◽  
Infrared Spectroscopy ◽  
Porphyromonas Gingivalis ◽  
Crucial Role ◽  
Protoporphyrin Ix ◽  
Visible Spectroscopy ◽  
Host Proteins ◽  
Pigment Formation ◽  
Uv Visible

The lysine- and arginine-specific gingipains (Kgp, and RgpA and RgpB) are the major proteinases produced by the black-pigmented periodontopathogen Porphyromonas gingivalis. They play a role in degrading host proteins, including haemoglobin, from which is formed the μ-oxo bishaem complex of iron(III) protoporphyrin IX, [Fe(III)PPIX]2O, the major haem component of the black pigment. Kgp and RgpA bind haem and haemoglobin via the haemagglutinin-adhesin 2 (HA2) domain, but the role of this domain in the formation of μ-oxo bishaem-containing pigment is not known. UV-visible spectroscopy was used to examine the interaction of iron(III) protoporphyrin IX monomers [Fe(III)PPIX.OH] with recombinant HA2 and purified HRgpA, Kgp and RgpB gingipains. The HA2 domain reacted with Fe(III)PPIX.OH to form μ-oxo bishaem, the presence of which was confirmed by Fourier transform infrared spectroscopy. Both HRgpA and Kgp, but not RgpB, also mediated μ-oxo bishaem formation and aggregation. It is concluded that the Arg- and Lys-gingipains with HA2 haemagglutinin domains may play a crucial role in haem-pigment formation by converting Fe(III)PPIX.OH monomers into [Fe(III)PPIX]2O and promoting their aggregation.

ZnTPPS demetalation: Role of polyelectrolytes on aggregation after protonation in acid

2017 ◽  
Vol 21 (04-06) ◽  
pp. 426-430 ◽  
Author(s):  
Massimiliano Gaeta ◽  
Rosalba Randazzo ◽  
Domenico Andrea Cristaldi ◽  
Alessandro D’Urso ◽  
Roberto Purrello ◽  
...  
Keyword(s):  
Metal Ion ◽  
Electrostatic Interactions ◽  
Inner Core ◽  
Plane Deformation ◽  
Strong Acid ◽  
Central Metal ◽  
Visible Spectroscopy ◽  
Out Of Plane ◽  
Uv Visible

Acid-base properties of tetra-anionic zinc meso-5,10,15,20-tetrakis-(4-sulfonatophenyl)porphyrin (ZnTPPS) in presence of cationic and anionic polyelectrolytes are studied by UV-visible spectroscopy. In fact, spectral modifications related to the out-of-plane deformation of porphyrins after protonation allow for an easy probing of the protonation event that, in presence of a metal derivative, requires a deprotonation step. Interactions with poly-D-glutamate and poly-L-lysine, modulated by system electrostatics and by the presence of an axially-coordinated central metal ion, trigger both protonation occurrences as well as porphyrin self-aggregation. The crucial role of electrostatic interactions experienced by the metalated inner core in strong acid solution, probed by UV-visible spectroscopy, are discussed.

scholarly journals The role of multihaem cytochromes in the respiration of nitrite in Escherichia coli and Fe(III) in Shewanella oneidensis

2008 ◽  
Vol 36 (5) ◽  
pp. 1005-1010 ◽  
Author(s):  
Thomas A. Clarke ◽  
Tracey Holley ◽  
Robert S. Hartshorne ◽  
Jim K. Fredrickson ◽  
John M. Zachara ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Polypeptide Chain ◽  
Shewanella Oneidensis ◽  
Visible Spectroscopy ◽  
Truncated Form ◽  
E Coli ◽  
Uv Visible ◽  
Electron Carriers ◽  
Iron Reductase

The periplasmic nitrite reductase system from Escherichia coli and the extracellular Fe(III) reductase system from Shewanella oneidensis contain multihaem c-type cytochromes as electron carriers and terminal reductases. The position and orientation of the haem cofactors in multihaem cytochromes from different bacteria often show significant conservation despite different arrangements of the polypeptide chain. We propose that the decahaem cytochromes of the iron reductase system MtrA, MtrC and OmcA comprise pentahaem ‘modules’ similar to the electron donor protein, NrfB, from E. coli. To demonstrate this, we have isolated and characterized the N-terminal pentahaem module of MtrA by preparing a truncated form containing five covalently attached haems. UV–visible spectroscopy indicated that all five haems were low-spin, consistent with the presence of bis-His ligand co-ordination as found in full-length MtrA.

Phytochemical Preparation, Characterization and Photocatalytic Applications of Ag-TiO2 Nanocatalyst

2015 ◽  
Vol 1086 ◽  
pp. 1-6 ◽  
Author(s):  
P. Yuvasree ◽  
K. Nithya ◽  
N. Neelakandeswari ◽  
N. Rajasekaran ◽  
K. Uthayarani ◽  
...  
Keyword(s):  
Silver Nanoparticles ◽  
Rhodamine B ◽  
X Ray Diffraction ◽  
Visible Spectroscopy ◽  
Ag Nps ◽  
X Ray ◽  
Chemical Approach ◽  
Uv Visible ◽  
Photocatalytic Applications

Green chemical approach is adopted for the synthesis of silver nanoparticles (Ag NPs). Since the nanoparticles tend to aggregate during the course of the catalytic reaction, they need to be stabilized by employing a suitable template or a support. Hence the prepared nanoparticles were loaded on titania support and used as a photocatalyst. Silver loaded titania (Ag-TiO2) is characterized by UV-visible spectroscopy, powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic absorption spectroscopy (AAS). Prepared composite was also tested for its photocatalytic activity against the degradation of an industrial pollutant Rhodamine B dye. Effect of pH, ratio between the catalyst and the substrate and also the role of free radical generator in the degradation have been tested and summarized in this work.Keywords: Silver nanoparticles, Phytochemical preparation, Green chemical approach, Photocatalysis, Rhodamine B

scholarly journals Intermediate band in the gap of photosensitive hybrid gel based on titanium oxide: role of coordinated ligands during photoreduction

2014 ◽  
Vol 2 (29) ◽  
pp. 11499-11508 ◽  
Author(s):  
Thomas Cottineau ◽  
Annabelle Rouet ◽  
Vincent Fernandez ◽  
Luc Brohan ◽  
Mireille Richard-Plouet
Keyword(s):  
Titanium Oxide ◽  
Visible Spectroscopy ◽  
Intermediate Band ◽  
Hybrid Gel ◽  
Uv Visible

UV induced Intermediate band appearance in a new hybrid organic–inorganic TiOx based material is studied by XPS and UV-visible spectroscopy.

Biocompatibility of Silver Nano Bio-conjugates from Vitis vinifera Seeds and its Major Component Resveratrol

2016 ◽  
Vol 6 (3) ◽  
Author(s):  
R. Preethi ◽  
P. Padma
Keyword(s):  
Zeta Potential ◽  
Vitis Vinifera ◽  
Silver Ions ◽  
Seed Extract ◽  
Polydispersity Index ◽  
Potential Range ◽  
Visible Spectroscopy ◽  
Grape Seeds ◽  
X Ray ◽  
Uv Visible

The study focused on the green synthesis of silver nanobioconjugates (AgNPs) from phenolic-rich fruit source, Vitis vinifera seed extract and its major component phenolic, resveratrol respectively. Sunlight exposure for 20 minutes was the method of choice for the synthesis of AgNPs of the extract as well as the phenolic, resveratrol. The synthesized nanobioconjugates were characterized using UV-Visible spectroscopy, Transmission electron microscopy (TEM), Energy dispersive X-ray analysis (EDAX), X-ray diffraction (XRD), Polydispersity index, Zeta potential and Fourier transform infrared spectroscopy (FTIR). The reduction of silver ions was confirmed by UV-visible spectroscopy with peaks at 440nm for both nanobioconjugates synthesized from seed extract and compound. The nanobioconjugates showed the spherical in shape with 14-35nm in size and crystalline in nature. The conjugates are well dispersed with 0.301 and 0.287 polydispersity index and the zeta potential range at -13.6 and -14.3mV for stability. The FTRI data proved that the components in grape seeds act as good reductants and stabilizers for the silver nanobioconjugate synthesis. All the synthesized nanobioconjugates exhibited steady and sustained release of the medicinal components conjugated, proving their druggability, and were biocompatible with human cells, demonstrating their safety. The findings of the study validate the anticancer properties of silver nanobioconjugates of Vitis vinifera and its active component resveratrol.

Liquid-liquid extraction of succinate using a dicopper cryptate

2020 ◽  
Author(s):  
Riccardo Mobili ◽  
Sonia La Cognata ◽  
Francesca Merlo ◽  
Andrea Speltini ◽  
Massimo Boiocchi ◽  
...  
Keyword(s):  
Aqueous Phase ◽  
Visible Spectrum ◽  
Tca Cycle ◽  
Residual Concentration ◽  
Waste Products ◽  
Liquid Liquid Extraction ◽  
The Tca Cycle ◽  
Quantitative Extraction ◽  
Uv Visible

<div> <p>The extraction of the succinate dianion from a neutral aqueous solution into dichloromethane is obtained using a lipophilic cage-like dicopper(II) complex as the extractant. The quantitative extraction exploits the high affinity of the succinate anion for the cavity of the azacryptate. The anion is effectively transferred from the aqueous phase, buffered at pH 7 with HEPES, into dichloromethane. A 1:1 extractant:anion adduct is obtained. Extraction can be easily monitored by following changes in the UV-visible spectrum of the dicopper complex in dichloromethane, and by measuring the residual concentration of succinate in the aqueous phase by HPLC−UV. Considering i) the relevance of polycarboxylates in biochemistry, as e.g. normal intermediates of the TCA cycle, ii) the relevance of dicarboxylates in the environmental field, as e.g. waste products of industrial processes, and iii) the recently discovered role of succinate and other dicarboxylates in pathophysiological processes including cancer, our results open new perspectives for research in all contexts where selective recognition, trapping and extraction of polycarboxylates is required. </p> </div>

Evaluation of Antibacterial and Antidiabetic Potential of Silver Nanoparticles using Eugenia Uniflora L. Seed Extract

2020 ◽  
Vol 13 (6) ◽  
pp. 5217-5225
Author(s):  
Guru Kumar Dugganaboyana ◽  
Chethankumar Mukunda ◽  
Suresh Darshini Inakanally
Keyword(s):  
Biomedical Applications ◽  
Pathogenic Bacteria ◽  
Seed Extract ◽  
Drug Formulation ◽  
Visible Spectroscopy ◽  
Plant Materials ◽  
X Ray ◽  
Eugenia Uniflora ◽  
Uv Visible

In recent years, green nanotechnology-based approaches using plant materials have been accepted as an environmentally friendly and cost-effective approach with various biomedical applications. In the current study, AgNPs were synthesized using the seed extract of the Eugenia uniflora L. (E.uniflora). Characterization was done using UV-Visible spectroscopy, X-ray diffraction (XRD), scanning electronic microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) analyses. The formation of AgNPs has confirmed through UV-Visible spectroscopy (at 466 nm) by the change of color owing to surface Plasmon resonance. Based on the XRD pattern, the crystalline property of AgNPs was established. The functional group existing in seed of E.uniflora extract accountable for the reduction of Ag+ ion and the stabilization of AgNPs was investigated. The morphological structures and elemental composition was determined by SEM and EDX analysis. With the growing application of AgNPs in biomedical perspectives, the biosynthesized AgNPs were evaluated for their antibacterial and along with their antidiabetic potential. The results showed that AgNPs are extremely effective with potent antidiabetic potential at a very low concentration. It also exhibited potential antibacterial activity against the three tested human pathogenic bacteria. Overall, the results highlight the effectiveness and potential applications of AgNPs in biomedical fields such as in the treatment of acute illnesses as well as in drug formulation for treating various diseases such as cancer and diabetes. It could be concluded that E. uniflora seed extract AgNPs can be used efficiently for in vitro evaluation of their antibacterial and antidiabetic effects with potent biomedical applications.

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