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Introduction
Stela Georgieva currently works at the Department of Analytic Chemistry, University of Chemical Technology and Metallurgy. Stela does research in Analytical Chemistry, Electrochemistry and Spectroscopy. Their current project is development of methods for ppm and ppb determination of metal ions in water samples.
Additional affiliations
January 2005 - November 2020
December 2003 - November 2020
Publications
Publications (64)
A study of the formation of copper (II) complexes with hemorphin peptide motifs in alkalic water solutions is presented. The effect of the peptide ligand on the complexing properties of the Cu (II) ion was quantified by giving the stoichiometry and stability of the complex compounds in the medium in which they are formed using voltammetric (cyclic)...
The endogenous hemorphins are bioactive peptides with activity on opioid receptors. They are extensively studied and summarized in numerous reviews. During the last decade, several research teams have synthesized, characterized, and pharmacologically evaluated synthetic hemorphin analogs containing unusual amino acids, D-amino acids, α-aminophospho...
Endogenous hemorphins are being intensively investigated as therapeutic agents in neuropharmacology, and also as biomarkers in mood regulation, inflammation and oncology. The datasets collected herein report physicochemical parameters of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine membranes in the presence of VV-hemorphin-5 (Val-Val-Tyr-Pro-Tr...
The emergence of diverse peptide derivatives has been due to constant efforts to find a specific peptide with pronounced biological activity for effective application as a therapeutic. Spinorphin-peptide products have been reported to possess various applications and properties. In the present study, spinorphin peptides with a rhodamine residue and...
New analogues of the endogenous heptapeptide VV-hemorphin-5 (valorphin) synthesized by amino acid replacement allow for tailoring the peptide activity in vivo. Investigation of hemorphin-induced alterations of lipid bilayers’ physicochemical parameters unravels membrane-mediated mechanisms of interaction with cells and subcellular structures. We st...
![Figure 6. Plots of Ep, [V] vs. I, [A] in differential pulse...](profile/Petar-Todorov-2/publication/362308365/figure/fig3/AS:1182820085039124@1659017692871/Plots-of-Ep-V-vs-I-A-in-differential-pulse-voltammetric-determinations-of-the_Q320.jpg)
![Figure 7. Plots of Ep, [V] vs. first current derivatives of...](profile/Petar-Todorov-2/publication/362308365/figure/fig4/AS:1182820089245696@1659017693005/Plots-of-Ep-V-vs-first-current-derivatives-of-differential-pulse-voltammetric_Q320.jpg)
![Figure 7. Plots of Ep, [V] vs. first current derivatives of...](profile/Petar-Todorov-2/publication/362308365/figure/fig5/AS:1182820089233409@1659017693060/Plots-of-Ep-V-vs-first-current-derivatives-of-differential-pulse-voltammetric_Q320.jpg)
Some new N- and C-modified biomolecular peptide analogues of both VV-hemorphin-5 and VV-hemorphin-7 with varied amino acids (Cys, Glu, His), 1-adamantanecarboxylic acid, and niacin (nicotinic acid) were synthesized by solid-phase peptide synthesis—Fmoc (9-fluorenylmethoxy-carbonyl) chemistry and were characterized in water solutions with different...
Water is a very important natural resource which is being exploited indiscriminately by humans. The water resources are getting depleted and polluted by anthropogenic sources. One of the key activities to conserve the water including the river water is to achieve a good water quality. Water quality describes the physical, chemical and biological st...
The present study describes a method for the determination of As (III) and As (V) in copper electrolytes. the method is based on the separation of as (iii) from a copper electrolyte by triple liquid-liquid extraction using a non-polar organic solvent in a medium of 10-12 mol L-1 HCl. the extract contains as (iii) and the raffinate-As (V), respectiv...
This manuscript presented the synthesis and characterization of two new N- and C-modified analogues of VV-hemorphin-7 containing RGD (Arg–Gly–Asp) residues as potential nociceptive agents and bioactive materials. It has been shown that the addition of one or two RGD sequences to natural VV-hemorphin-7 increases its effect on acute nociception, but...
![A Plots of Ep, [V] vs. I, [A] in differential pulse voltammetric...](publication/357536750/figure/fig4/AS:1129735685963778@1646361385863/A-Plots-of-Ep-V-vs-I-A-in-differential-pulse-voltammetric-determinations-of_Q320.jpg)
In the present study, a series of new analogues of both LVV- and VV-hemorphin-7 have been synthesized and characterized. They were modified at the N- and C-terminus with varied amino acids (Ile, D-Leu, D-Val, D-Phe) and enantiopure chiral S- and R- α-aminophosphonic acids ((dimethoxyphosphoryl)methyl)-valine and ((dimethoxyphosphoryl) methyl)-leuci...
Herein, the synthesis and characterization of some novel N-modified hybrid analogues of hemorphins containing a C-5 substituted hydantoin residue as potential anticonvulsants and blockade of sodium channels are presented. Their structure-property relationships have been highlighted by electrochemical and Fourier Transform Infrared Spectroscopy (FT-...
In this article the current changes in the water quality of rivers Topolnitsa and Luda Yana have
been analyzed and evaluated. The river basins are under the significant anthropogenic impact of
various origins and nature. The main sources of pollution, the emitted substances and the spatiotemporal features of the change of the water quality are dete...
Here we report on the synthesis and characterization of three new N-modified analogues of hemorphin-4 with rhodamine B. Modified with chloroacetyl, chloride cotton fabric has been dyed and color coordinates of the obtained textile materials were determined. Antiviral and virucidal activities of both the peptide-rhodamine B compounds and the dyed te...
In this work the transmittance coefficient (T), the reflectance coefficient (R), the refractive index (n), the extinction
coefficient (k), the optical absorption coefficient (α) and the optical band gap (Eg) of thin (poly[1-[4-(3-carboxy-
4-hydroxyphenylazo)benzenesulfonamido]-1,2-ethanediyl, sodium salt]), shortly PAZO, azopolymer films with em-...
Abstract: Herein, the spectral and electrochemical characterizations of three different substituted N-phthalimide azo-azomethine (NAA) dyes (L) containing an o-hydroxy group and their NAA-M(II) chelates [M(II): Cu, Ni, Co, Pb] were reported by using UV–Vis and fluorescence spectroscopy and potentiometric and voltamperometric techniques. The pK valu...
A new cyclic voltammetric method has been developed for the determination of Cu(II) in the presence of Fe(III) in tap and surface water samples using complexing properties of 5,5'-diphenylimidazolidine-2,4-dione derivative. In acetate buffer solution (0.1 mol L-1 ; pH 5.25 ± 0.01) containing minimum tenfold excess of imidazolidine derivative, coppe...
In the present study, a novel analogue of azobenzene-containing hemorphin-4 has been synthesized and investigated for assessment of spectral, electrochemical, and biological effects. The synthesis was achieved by a modified solid-phase peptide synthesis (SPPS) by Fmoc-strategy. This compound represents a newly synthesized and unstudied peptide-base...
The paper presents a study of the diffraction efficiency of polarization holographic gratings recorded in thin films of the azopolymer PAZO (poly[1-[4-(3-carboxy-4-hydroxyphenylazo) benzenesulfonamido]-1,2-ethanediyl, sodium salt]) doped with Cu(II) 3-amino-5,5'-dimethylhydantoin (CLP) and Ni(II) 3-amino-5,5'-dimethylhydantoin (NLP) at three differ...
In the present study, several new analogues of hemorphin-4, modified with unnatural conformationally restricted amino acids followed the structure Aaa–Tyr–Xxx–Trp–Thr–NH2, where Aaa is the low-molecular-weight lipophilic adamantyl building block, and Xxx is Ac5c (1-aminocyclopentanecarboxylic acid) or Ac6c (1-aminocyclohexane carboxylic acid) was s...
Herein, the synthesis and characterization of four novel 5,5'
-diphenylhydantoin Schiff bases containing
different aromatic species are presented. Their structure–property relationship was studied by X-ray,
optical and electrochemical methods as well as DFT calculations in terms of their E/Z photoisomerization
and enol/keto phototaumerization. The...
Natural and anthropogenic sources produce mainly metal ions which can be accumulated in sediments that have a significant environmental impact on local areas, especially for their river water quality. The environmental analysis applies chemical sensors having the inherent ability to detect in real-time analytes as cations, anions, or small molecule...
Herein, some new analogues of VV-hemorphin-7, modified at position 4 and 7 by the unnatural amino acids followed the structure Val-Val-Tyr-Xxx-Trp-Thr-Yyy-Arg-Phe-NH2, where Xxx is Ac5c (1-aminocyclopentanecarboxylic acid) or Ac6c (1-aminocyclohexane carboxylic acid) and Yyy is Dap (diaminopropanoic acid) or Dab (diaminobutanoic acid), were synthes...
The anthropogenic pollution of the Yantra River was assessed during six year period (2013-2018) in terms of metals in key sites along the river, pointed near to industrial activities, municipal effluents and pollution from tributaries in the catchment area. The assessment of metal concentrations in the water samples was made in accordance with Dire...
A new series of N-modified analogues of the VV-hemorphin-5 with aminophosphonate moiety have been synthesized, characterized and investigated for anticonvulsant activity. The novel peptide analogues were prepared by solid-phase peptide synthesis–Fmoc-strategy and were evaluated in the timed intravenous pentylenetetrazole infusion test (ivPTZ) and 6...
A biologically active VV-hemorphin-5 (Valorphin: Val-Val-Tyr-Pro-Trp-Thr-Gln) analogue was characterized electrochemically. In this regard the oxidation and adsorption reactions of the peptide on an electrode surface in a phosphate buffer solution have been studied and compared with those of valorphin and polarographic active tryptophan and tyrosin...
A novel analog of VV-hemorphin-5 containing azobenzene moiety has been synthesized and investigated for anticonvulsant activity in relation to its E → Z photophysical properties activated by long wavelength light at 365 nm. The synthesis was achieved by a modified SPPS by Fmoc-dimerization strategy. The electrochemical behavior before and after UV...
The present study reports synthesis, structural, photophysical and electrochemical properties of five new Schiff bases containing hydantoin ring. The compounds were synthesized via condensation reaction between 3-amino-5,5’-dimethylhydantoin and five different aromatic aldehydes. All the compounds were characterized using different spectroscopic an...
We present a single crystal XRD, LA-ICP-MS and cyclic voltammetry studies on the observed interaction of the
protein lysozyme and TiO2 nanosized particles (JRC NM-101, anatase). The diffraction quality of lysozyme single
crystals grown in presence and absence of TiO2 was comparable. The X-ray structure solution reveled that lysozyme
crystallizes in...
In the present study, some new analogues of VV-hemorphin-5, modified at position 1 and 7 by the non-proteinogenic and/or natural amino acids followed the structures Xxx-Val-Val-Tyr-Pro-Trp-Thr-Gln-NH2 and Val-Val-Tyr-Pro-Trp-Thr-Yyy-NH2, where Xxx is Ile or Aib and Yyy is Lys/Orn/Dap/Dab were synthesized to investigate their potential antinocicepti...
The anthropogenic source pollution of the Mesta River was assessed during the period 2011 and 2016 in terms of pH, conductivity, chemical oxygen demand (COD), anions and heavy metals in key sites of the Mesta river pointed as: S1 (the Mesta river before the Iztok river); S2 (the Iztok river before the Mesta river); S3 – the river Mesta after the Iz...
Abstract The interaction of 3-amino-5,5′-dimethylhydantoin with nickel and zinc ions was investigated at different conditions by means of UV–Vis, FTIR spectroscopy and electrochemical methods as well as DFT quantum chemical calculations. Through calculated DFT frequencies and experimental FTIR spectra of the complexes the correlation analysis has b...
In this paper we present the results of the study of ceramic composite Y123/BaCuO 2 obtained in one-step procedure, which appears to lead to material possessing both superconducting and magnetic properties at low temperatures. By applying scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), spectrophotometry for oxygen in...
New copper(II)-aminohydantoin complexes ([CuAPh2Cl2(OH2)2]; [CuAPh2(NH3) (OH2)2], where APh is 3-amino-5,5-diphenylhydantoin), were synthesized and analyzed by means of elemental analysis, atomic absorption spectroscopy, UV-Vis spectroscopy and voltamperometric method. The complex forming processes in the Cu(II)- aminophenytoin (APh) system are stu...
Abstract: The anthropogenic source pollution of the Chepinska River was assessed in terms of pH, conductivity, chemical oxygen demand (COD), anions and heavy metals. The application of multivariate cluster analysis (CA) for the interpretation of a large and complex data matrix obtained during a monitoring program of surface waters in Chepinska Rive...
This manuscript reports the results of a qualitative study introducing engineering student into the workplace and increasing their job opportunities. Student Training Internship Programs funding by the European Social Fund have been started in Bulgarian universities (BG051РО001-3.3.07-0002) in order to increase the possibility for the student trans...
The electrochemical behavior of four biologically active cycloalkane espirohydantoins with 5-, 6-, 7-, and 8-membered rings: 1,3-diazaspiro[4.4] nonane-2,4-dione (CSH(5)); 1,3-diazaspiro[4.5]decane-2,4-dione (CSH(6)); 1,3-diazaspiro[4.6]undecane-2,4-dione (CSH(7)); and 1,3-diazaspiro[4.7]dodecane-2,4-dione (CSH(8)) has been investigated at the pH r...
Development of biosensors for lactate determination has gained an increased research interest because of their wide application in clinical analysis and control of fermentation processes in food industry. Lactate biosensors with enzyme modified modules are a perspective alternative to the conventional methods in clinical analysis for their fast res...
This review article is concerned with the oxygen stoichiometry determination in YBa2Cu3Oy and
REBa2Cu3Oy (RE = Er, Eu, Gd) superconductors. The nondestructive and destructive methods for
the determination of the oxygen coefficient y (y = 6.5 + δ, δ is the non-stoichiometric oxygen
coefficient) are described. The destructive methods as titrimetry an...
A student research project for sampling and analysis of drinking water from different Bulgarian regions has been parallel incorporated into analytical and organic courses at the second level of high engineering education in Bulgaria. The degree of quality of drinking water has been evaluated in fi ve cities from different Bulgarian regions: Stara Z...
Abstract: We have developed and applied a spectrophotometric method using measurement of the absorbance of the complex Co(III)-EDTA for the determination of the oxygen stoichiometry in RBa2Cu3Oy (R = Er, Y, Eu and Dy) high-Tc bulk materials. The obtained results were compared with those obtained by second destructive spectrophotometric method and R...
The chemical stability of YBCO (Y1Ba2Cu3O7–x) and GdBCO (Gd1Ba2Cu3O7-x) superconducting ceramics in an
alkaline medium was studied by analyzing polycrystalline samples of the ceramics before and after exposure to an
alkaline solution (7M KOH), normally used as a basic electrolyte in alkaline batteries. The high chemical resistance of
the ceramics t...
Novel mixed complexes of copper (II) and cobalt (II) with 3-amino-5,5-dimethylhydantoin were synthesized and their in vitro anticancer activity was investigated. The structures of the compounds were confirmed by IR, UV–Vis spectrometry, voltammetry and elemental analysis. The cytotoxic effects of novel complexes of copper (II) and cobalt (II) with...
The present chapter discusses our experimental results on morphology, stability, and the mechanical properties of two-component charged lipid bilayers in aqueous solutions with controlled ionic strength at low pH. Observations by phase-contrast and fluorescent microscopy revealed coexistence of two structural phases in membranes from stearoyl oleoy...
Detailed investigations on the possibility for determination of the oxygen stoichiometry in YBa2Cu3Oy superconducting samples by measuring the absorbance of the colored Co(III)-EDTA and Cu(II)-EDTA complexes in one solution have been performed. The absorptivity of the complexes at pH 2.5 and 4.9 as well as Beer’s law have been studied. The content...
The oxygen stability of the REBa2Cu3Oy (RE = Y, Gd; y = 6,5+δ) superconducting ceramics previously immersed
in strong alkaline electrolyte bath have been studied. The samples were placed in solution of 7М KOH (pH 13) for 96 h
and then the oxygen content was determined by spectrophotometry and XRD-spectrometry. The results obtained by the
both metho...
The present chapter discusses our experimental results on morphology, stability, and
the mechanical properties of two-component charged lipid bilayers in aqueous solutions
with controlled ionic strength at low pH. Observations by phase-contrast and fluorescent
microscopy revealed coexistence of two structural phases in membranes from
stearoyl oleoy...
The oxygen stability of the REBa2Cu3Oy (RE = Y, Gd; y = 6,5+δ) superconducting ceramics previously immersed in strong alkaline electrolyte bath have been studied. The samples were placed in solution of 7M KOH (pH 13) for 96 h and then the oxygen content was determined by spectrophotometry and XRD-spectrometry. The results obtained by the both metho...
Spectrophotometric study of competitive complex formation equilibria involving overlapped spectral responding species applying a simple and versatile algorithm was carried out. The algorithm involves multivariable regression for calculation of equilibrium concentrations from multiwavelength data and mass action law for the stability constant calcul...
The spectrophotometric method using the measurement of the absorbance of an I 3 --starch compound is applied for the determination of the oxygen stoichiometry of high temperature Y 1 Ba 2 Cu 3 O y (y=6.5+ä) cuprates with oxygen content from 6.6 to 7.0. In order to measure the absorbance values of the solutions precisely some changes in the procedur...
Lipid bilayers (or membranes) are biomimetic, two-dimensional liquid crystalline structures, readily obtainable in laboratory conditions. The increasing in-terest towards them is due in a great extent to the potential of their application in the biomolecular electronics. In this respect, the experimental and theoretical inves-tigation of the fundam...
High temperature Gd(1)Ba(2)Cu(3)O(y) and Er(1)Ba(2)Cu(3)O(y) (y = 6.5 + delta) superconducting ceramics were prepared via solid-state reaction. The amount of oxygen in the synthesized samples was varied as they were kept at 460+/-5 degrees C in flowing argon. The oxygen non-stoichiometry content, delta was determined by measuring the absorption of...
Criteria for the determination of the peak potential r p E of reversible and same cases of quasireversible electrode reactions in the differential pulse polarography are proposed. On the base of the r p E values found De Ford and Humes, as well as Ledens functions are recommended to be used for the determination of stability constants of complexe...
The conditions for formation of the I(3)(-)-starch compound and measuring its absorbance have been found, and a spectrophotometric method has been developed for the determination of the oxygen content in YBa(2)Cu(3)O(y) superconducting bulk samples. The method involves the following stages: a decomposition of the sample in an acid medium in the pre...
We have developed and employed a spectrophotometric method for the determination of the oxygen stoichiometry in Ca doped RE (Rare Earth elements)Ba2Cu3Oz high-Tc bulk materials. The method possesses several advantages: the apparatus is simple and inexpensive, so it can be widely used; the operational procedure is simple and time saving. Moreover, t...
The chemistry graduate requires not only a
solid knowledge base but also the ability to
apply and extend their knowledge in order to
solve unfamiliar problems. Analytical and
critical thinking skills are assumed and, in
addition, communication, team working, time
management, independent learning skills and,
last but not least, enthusiasm. The conte...
The conditions for the spectrophotometric Cu (II) determination by the system I --starch in the presence of Fe (III) are studied. The redoxy reaction between Cu(II) and I -ions, and the reaction between -3 I -complex and starch proceed in a medium of 0.08 mol l -1 sodium acetate -acetic acid buffer with pH 4.9 in the presence of 0.34 mol l -1 KI an...
Projects
Projects (4)
Договор: № КП-06-ДК1/11 от 29.03.2021г., С ВЪЗЛОЖИТЕЛ ФНИ-МОН: на тема: „Текстилни материали за предотвратяване разпространението на SARS-CoV2 и на други патогени“.
Сайт на проекта: http://antiviraltextile.eu/
The project is supported by Bulgarian National Scientific Fund project № КП-06-ДК1/11 - 29.03.2021 (title: “Textile materials to prevent the spread of SARS-CoV2 and other pathogens”) of the Ministry of Education and Science, Bulgaria.
http://antiviraltextile.eu/
ДОГОВОР № КП-06-ОПР03-3/14.12.2018 С ВЪЗЛОЖИТЕЛ ФНИ-МОН
Изследване и разкриване, класификация и типологизация на повърхностни водни тела от тип „РЕКИ“ по отношение на физикохимичното им състояние в зависимост от характера и особеностите на антропогенното въздействие върху качеството на водите им.
Обект на изследване са реките Тополница и Луда Яна, които са подложени на интензивно, мащабно и разнородно антропогенно въздействие. значителна част от водните тела в басейните се намират в лошо химично състояние.
Предмет на изследването са състоянието, трансформациите и тенденциите в качеството на речните води, характера и механизмите на антропогенния натиск върху водите.
The project is supported by National Science Fund of Bulgaria ДН 18/5. This project aims synthesis and property characterization of the new azo polymer (polyimide) materials with potential photophysical and photodynamic applications. The general idea is to development of new materials for excellence in nanotechnology science. The investigations are focused on a development of photoresponsive azo polymers or small molecules. In this proposals we suggest to synthesize and investigate polyimide based azo materials, because they exhibit good mechanical properties, high stability against temperature, solvents and liquid crystals and thus they are considered as very attractive candidates for applications in optical storage or liquid crystal alignment.