Petko Ivanov

University of National and World Economy, Business Economics, Undergraduate

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Papers by Petko Ivanov

The Li ght-House Keeper' by Henryk Sienkiewicz: An Interpretation

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The Controversial Saints: Representations of Cyril and Methodius in Modern Slavic History: Chronology and Theses

The subject of this paper is the construction of Cyril and Methodius as pan-Slavic and national S... more The subject of this paper is the construction of Cyril and Methodius as pan-Slavic and national Slavic identity symbols. It analyzes the mechanisms and the actual process of transforming the ninth-century Byzantine missionaries into eponymic Slavic forefathers destined to play a major role in the nesting of Slavic identities and in the legitimization of various political organisms in the modern Slavic world. The paper therefore does not deal in the alleged "historical truth" and deliberately avoids historical objectivism as far as the medieval events related to Cyril and Methodius are concerned. Furthermore, its primary sources are not historical documents about the actual Cyrillo-Methodian mission and its medieval aftermath, but rather the modern scholarly and other media interpretations of these "historical facts" applied to justify contemporary political aspirations. The basic theoretic al precepts that underline my analysis are Benedict Anderson 's view of nations as "imagined communities, " and Eric Hobsbawm 's thesis about invention (or "manufacturing ") of national traditions. The time scope of the material studied encompasses only the nineteenth and the twentieth centuries. This restriction is based on the premise that it was namely the nineteenth century that brought to the fore the figures of Cyril and Methodius in relation to both the birth of the political idea of Pan-Slavism and the emancipation of modern Slavic states. The main target of ideological speculations and manipulations in the Slavic world are in fact not Cyril and Methodius themselves, but their Slavonic mission understood as (1) epistemological endeavor (the invention of the Slavonic alphabet and the creation of a written Slavic language); (2) confessional achievement (confirmation of Christianity among the Slavs). Petko Ivanov The University of Chicago 2 In the first part of this paper I systematize the landmark events in the development of the "Cyrillo-Methodian question " in a chronological table. It is only a first approximation to a historical background section of a future more detailed study. In the second part I will present some preliminary theses in an attempt to conceptualize the source material. They are articulated in three paradoxes of contemporary Cyrillo-Methodiana (an obvious semiparodistic tribute to the celebrated article by Ihor Ševčenko 1964): Cyril and Methodiusthe unforgettable / imagined past of the Slavs; the national / pan-Slavic saints; the Cyrillo-Methodian mission as an emancipating communion with European civilization.

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Language in Culture Course Handouts

Language Continuity & Change in Time Synchronic linguistics will be concerned with the logical an... more Language Continuity & Change in Time Synchronic linguistics will be concerned with the logical and psychological relations that bind together coexisting terms and form a system in the collective mind of speakers. (Saussure, p.98ff.) Diachronic linguistics, on the contrary, will study relations that bind together successive terms not perceived by the collective mind but substituted for each other without forming a system." Dialectal continuums (within a language or a language family) Space: Two neighboring villages understand their speech-forms, but 100 villages away the speechforms are not mutually intelligible anymore Time: Two generations of villagers understand their speech-forms, but in 100 generations they are not mutually intelligible anymore "What is the result of differentiation through time? At one moment in history a single language may reign throughout a particular territory, and five or ten centuries later the inhabitants of two of its extremes probably will not be able to understand each other. At any particular point, however, speakers will still understand the speech-forms of neighboring regions. A traveler going from one end of the country to the other would notice only small dialectal differences from one locality to the next. But the sum of these differences would increase, and eventually he would come to a language that the inhabitants of this starting point would not understand." "[T]he language will no longer be the same after a certain length of time. Evolution will not be uniform throughout the territory but will vary from zone to zone; no records indicate that any language has ever changed in the same way throughout its territory.

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Language in Culture Syllabus

The course is an introduction to linguistic anthropology with a main focus on language "use" in s... more The course is an introduction to linguistic anthropology with a main focus on language "use" in society. Among the main topics to be addressed are the notions of language ideology (how language is conceptualized by its users, e.g., what they think they do with language when they talk and otherwise utilize their language); pragmatics and metapragmatics; socio-cultural semiosis of linguistic practices, incl. language as group identity flag; making and differentiating languages, incl. class/gender/race and geographic stratifications; the social life of utterances from speech genres to entextualizations; indexicality in semiotically mediated social practices; the dynamics of language change (synchrony and diachrony); and, above all, language as denotational code and a system of signs. The readings include the classic texts of Saussure,

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Entropy Rules: Molecular Dynamics Simulations of Model Oligomers for Thermoresponsive Polymers

Entropy

We attempted to attain atomic-scale insights into the mechanism of the heat-induced phase transit... more We attempted to attain atomic-scale insights into the mechanism of the heat-induced phase transition of two thermoresponsive polymers containing amide groups, poly(N-isopropylacrylamide) (PNIPAM) and poly(2-isopropyl-2-oxazoline) (PIPOZ), and we succeeded in reproducing the existence of lower critical solution temperature (LCST). The simulation data are in accord with experimental findings. We found out that the entropy has an important contribution to the thermodynamics of the phase separation transition. Moreover, after decomposing further the entropy change to contributions from the solutes and from the solvent, it appeared out that the entropy of the solvent has the decisive share for the lowering of the free energy of the system when increasing the temperature above the LCST. Our conclusion is that the thermoresponsive behavior is driven by the entropy of the solvent. The water molecules structured around the functional groups of the polymer that are exposed to contact with the...

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Experimental evaluation of mechanical and electrical properties of RBC suspensions under flow. Role of RBC aggregating agent

Clinical hemorheology and microcirculation, 2010

Mechanical and electrical properties of red blood cells (RBC) suspensions in dextran 70 (Dx70), d... more Mechanical and electrical properties of red blood cells (RBC) suspensions in dextran 70 (Dx70), dextran 150 (Dx150), dextran 500 (Dx500) and polyethileneglycol (PEG) 35,000 with different concentrations were evaluated through apparent viscosity and conductivity measurements under steady and unsteady flow conditions. RBCs suspensions of the washed RBS in PBS (control) and Dx70, Dx150, Dx500 and PEG in PBS with different concentrations, adjusted to the same hematocrit of 40% were used for the experiments. Conductivity time and shear rate dependences in parallel with the rheological properties of the samples were studied under transient flow regimes at different local structure of the uniform Couette flow. Their relationships on dextrans and PEG concentrations were evaluated too. Low shear viscosity increased and conductivity decreased of RBC suspensions, compared to non-aggregating suspensions, depending on dextrans and PEG concentrations. A time course of blood conductivity recorded ...

Self-initiation of translation of mRNAs devoid of translational initiators in Escherichia coli

Folia biologica, 2001

Recent studies have shown that the canonical SD-anti-SD interaction is dispensable for the initia... more Recent studies have shown that the canonical SD-anti-SD interaction is dispensable for the initiation of translation of certain mRNAs in Escherichia coli. In this study the cat and tetR genes were modified to either destroy complementarity to E. coli 16S RNA or completely delete their 5' non-translated regions. Thus a series of cat- and tetR-derived genes were constructed, cloned under a strong constitutive promoter and expressed in E. coli cells. The efficiency of expression was evaluated by the yield of CAT (for the cat gene) and cell viability in increasing concentrations of antibiotic (for both cat and tetR genes). The obtained results show that the mRNAs transcribed from both series of reporter genes (cat and tetR) were active in vivo. Their activity was preserved even in the cases when the length of their 5' non-translated leader sequences was reduced to one nucleotide for the cat gene and eight nucleotides for the tetR gene. The yield of protein obtained with the latt...

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Conformations of Some Large-Ring Cyclodextrins Derived from Conformational Search with Molecular Dynamics Simulations and Principal Component Analysis

The Journal of Physical Chemistry B, 2010

Principal component analysis (PCA) was applied for postprocessing of trajectories from conformati... more Principal component analysis (PCA) was applied for postprocessing of trajectories from conformational search, based on 50.0 ns molecular dynamics (MD) simulations, with the purpose to elucidate the conformations of some large-ring cyclodextrins (LR-CDs), CDn (n = 24, 25, 26, 27, 28, 29). The dominant PCA modes for concerted motions of the macroring atoms were monitored in a lower-dimension subspace. The first 10 lowest indexed modes describe more than 90% of the total atomic motions in all cases, with about 85% (CD27, CD29) to more than 90% (CD24, CD25) contribution coming from the six highest-eigenvalue principal components. Representative average geometries of the cyclodextrin macrorings were also obtained for the whole simulation and for the five 10.0 ns time intervals of the simulation. Two conformations for CD26, the largest LR-CD for which X-ray data is available, are characterized by possessing, respectively, one and two helical turns. Resemblance to computed representative conformations of CD26 in water was found for CD27 and CD28, with the similarity being better expressed for the former case. Only CD24, among the two smaller size LR-CDs, displays resemblance during short simulation intervals to one of the conformations of CD26. The formation of small loops of six to seven glucose units is a favorable deformation mode of the macrorings. Besides, once a small loop of six to seven glucoses is formed, the next natural mode for deformation of the macromolecule is toward the creation of a short helix that further enhances the stability of the structure. The average geometry of CD29 has no likeness at all to the conformations of CD26. Thus, the difference of three glucose units between CD26 and CD29 already influences significantly the shape of the most probable conformation.

The bidentate complexes of (R,R)- and meso-α,α′-bis(trifluoromethyl)-9,10-anthracenedimethanol with cis-1-amino-2-indanol

Tetrahedron: Asymmetry, 2005

ABSTRACT The enantiorecognition of 1-aminoindane 3 and cis-1-amino-2-indanol 2 by (R,R)-alpha,alp... more ABSTRACT The enantiorecognition of 1-aminoindane 3 and cis-1-amino-2-indanol 2 by (R,R)-alpha,alpha&#39;-bis(trifluoromethyl)-9,10-anthracenedimethanol 1 is reported. The examination of the bidentate associations between 1 and 2 revealed that the cisoid conformation of 1 is responsible for the separation of the NMR signals. Two types of bimodal associations resulted from a cisoid conformation when meso-1 isomer was tested. Molecular mechanics modelling studies gave the possible structures of the associate species.

Subnanosecond 4H-SiC diode current breakers

Semiconductors, 2012

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Computational study on the ring distortions of 1,4-dicyanobenzene in the gas phase and in the crystal

Journal of Molecular Structure, 1998

Abstract A molecular mechanics software enhanced to perform empirical energy calculations on crys... more Abstract A molecular mechanics software enhanced to perform empirical energy calculations on crystals (KESSHOU) was further developed to handle intermolecular electrostatic interactions as well. The packing of the molecules of 1,4-dicyanobenzene and 1,4-diisocyanobenzene in the crystal was studied. The role of the van der Waals and the electrostatic interactions in the balance of nonbonded atom-atom interactions is analyzed. The packing forces are dominated by van der Waals forces. The electrostatic interactions have higher stabilizing contribution for the dicyano isomer than for the diisocyano form. The dependence of the results on the size of the crystal, the molecular mechanics force field (MM2 vs MM3), and the dielectric constant are also assessed. Ab initio MP2/6–311G∗∗ geometries of the isolated molecules are in accordance with the observed benzene ring distortions determined by electron diffraction.

Molecular mechanics (CONFLEX/MM3) search/minimization study of the conformations of ornoside and escuside

Journal of Molecular Structure, 2005

ABSTRACT The conformations of a secoiridoid glucoside (ornoside, 1) and a coumarine-secoiridoid (... more ABSTRACT The conformations of a secoiridoid glucoside (ornoside, 1) and a coumarine-secoiridoid (escuside, 2) were studied with the MM3 force field. The CONFLEX conformational search procedure was used for finding low-energy conformations. The computed data of 1 indicate an equilibrium between several hydrogen bonded conformations with prevailing folded conformations of the macroring endocyclic dihedrals. The conformational preference of 2 is biased towards two conformations that differ only in the rotations about bonds adjacent to the ester function. The present results provide insight into the most probable conformations of ornoside and escuside and compliment earlier NMR studies.

Surface analysis of doped lanthanide cobalt perovskites by X-ray photoelectron spectroscopy

Journal of Materials Science Letters, 1996

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Characterization of Functional Domains of Human EB1 Family Proteins

Journal of Biological Chemistry, 2003

EB1 family proteins are evolutionarily conserved proteins that bind microtubule plus-ends and cen... more EB1 family proteins are evolutionarily conserved proteins that bind microtubule plus-ends and centrosomes and regulate the dynamics and organization of microtubules. Human EB1 family proteins, which include EB1, EBF3, and RP1, also associate with the tumor suppressor protein adenomatous polyposis coli (APC) and p150 glued , a component of the dynactin complex. The structural basis for interaction between human EB1 family proteins and their associated proteins has not been defined in detail. EB1 family proteins have a calponin homology (CH) domain at their N terminus and an EB1-like C-terminal motif at their C terminus; the functional importance of these domains has not been determined. To better understand functions of human EB1 family proteins and to reveal functional similarities and differences among these proteins, we performed detailed characterizations of interactions between human EB1 family proteins and their associated proteins. We show that amino acids 1-133 of EB1 and EBF3 and the corresponding region of RP1, which contain a CH domain, are necessary and sufficient for binding microtubules, thus demonstrating for the first time that a CH domain contributes to binding microtubules. EB1 family proteins use overlapping but different regions that contain the EB1-like C-terminal motif to associate with APC and p150 glued. Neither APC nor p150 glued binding domain is necessary for EB1 or EBF3 to induce microtubule bundling, which requires amino acids 1-181 and 1-185 of EB1 and EBF3, respectively. We also determined that the EB1 family protein-binding regions are amino acids 2781-2820 and 18-111 of APC and p150 glued , respectively.

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Effect of tandemly repeated AGG triplets on the translation of CAT-mRNA inE. coli

FEBS Letters, 1992

It has been shown that tandems of rare arginine codons AGG have a strong inhibitor)' effect on tr... more It has been shown that tandems of rare arginine codons AGG have a strong inhibitor)' effect on translation of mRNA in fi '. cob [5]. This has been explained by the rate-limiting interaction of these codons with the less abundant tRNA Aca . In this study tandemly repeated AGO triplets were introduced into the chloramphcnicot acetyltransl'¢rase (CAT) gen¢ either upstream of the initiation ATG codes or downstream of it {both in frame and out of frame) and the expression of the modified genes was investigated. We report that the addition of AGO clusters resulted in a substantial inhibitory effect on CAT gene expression independently of their localization in mRNA. This inhibitory effect is explained by it competition of the tandem AGGAGG with the natural Shine-Dalgarno (SD) sequence (consensus AAGGAGGU) for the Y.end of the 16S small ribosomal RNA (rRNA).

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Substrate Specificity of the Escherichia Coli F RL B Amadoriase

Biotechnology & Biotechnological Equipment, 2012

Amadoriases are discovered in distant groups of organisms ranging from bacteria to humans. These ... more Amadoriases are discovered in distant groups of organisms ranging from bacteria to humans. These enzymes catalyze the degradation of Amadori products which are formed in the early stage a non-enzymatic reaction between reducing sugars and primary amines called the Maillard reaction or glycation. The physiological role of amadoriases is debatable and perhaps not constrained to one cellular process only. Among other functions amadoriases are proposed to ensure enzymatic defense against the deleterious consequences of protein glycation. A decade ago an amadoriase enzyme (the FrlB amadoriase) has been discovered in Escherichia coli catalyzing the removal of Amadori products form the ɛ-amino group of free lysine. The E. coli FrlB enzyme has been suggested to catabolize glycated lysine released in the human intestine upon digestion of food proteins. In the present study we demonstrate that the E. coli FrlB amadoriase is capable of catalyzing in the reverse reaction the formation of Amadori products on a number of free amino acids and on polypeptides as well. Based on these results we suggest that in the forward reaction the FrlB enzyme might serve to deglycate E. coli proteins thus helping bacterial cells to withstand the protein glycation burden.

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Conformational analysis of acetyl-L-phenylalaninep-acetyl andp-valeryl anilides

Biopolymers, 1983

ABSTRACT Empirical force-field calculations and ir and 1H-nmr spectra indicate that five-membered... more ABSTRACT Empirical force-field calculations and ir and 1H-nmr spectra indicate that five-membered (C5) and seven-membered (C) hydrogen-bonded rings are the preferred conformations of acetyl-L-Phe p-acetyl and p-valeryl anilides in nonpolar media. The C5/C ratio was found to be dependent on the dryness of the solute and the solvent. This fact and the results from conformational-energy calculations suggest that a molecule of water participates in the stabilization of the C conformation.

Angiogenin-induced tRNA-derived stress-induced RNAs promote stress-induced stress granule assembly

Journal of Biological …, 2010

The Journal of Biological Chemistry Skip to main page content. ...

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Molecular dynamics study of the conformational dynamics and energetics of some large‐ring cyclodextrins (CDn, n= 24, 25, 26, 27, 28, 29)

Chirality, 2007

Molecular dynamics simulations in water solution were performed on six large-ring cyclodextrins (... more Molecular dynamics simulations in water solution were performed on six large-ring cyclodextrins (LR-CDs) with a degree of polymerization 24, 25, 26, 27, 28, and 29. The AMBER parm99 force field and explicit water molecules (TIP3P) were used in the simulations. The present research was aimed at further extending our knowledge on the structural dynamics and the energetics of this new class of compounds that may eventually provide chiral cavities suitable for formation of inclusion complexes with small molecules, and, accordingly, to serve as host structures for chiral recognition. The study focused on several representatives flanking CD26-the largest LR-CD for which X-ray data is available. Both the monitoring of the structural variations during the simulations as well as the analyses of energy balances are indicative for high flexibility of the macrorings. Slight differences of the overall preferred shapes were detected with diminishing the size of the macromolecules from CD29 to CD24. An elongated cavity (CD28) or a double parallel strand in different specific representations are the dominating motifs in the LR-CDs studied: with loops at the two ends (CD25, CD28, CD29), with a loop at one end (CD25), twisted (CD26, CD27) or twisted with an open portion in the middle (CD24), helical (CD24, CD25), or linking two loops from one of their sides (CD27). Two loops connected by an arc (CD28, CD29) and a cavity with the shape of an extended rectangular (CD24, CD28) appear preferentially during the conformational interconversions of the two larger CDs, whereas helical motifs are present in the smaller macrorings: an extended helix with ends linked by an arc (CD24), helical turn and helical portion (CD26, CD27). A triple propeller conformation or three symmetrical loops of almost equal size were also detected for CD26 and CD29, respectively. The present results further support the hypothesis for the existence of more than one cavity in large-ring cyclodextrins and suggest preferred conformations in water solution for the LR-CDs with degree of polymerization from 24 to 29.

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New asymmetric monomethine cyanine dyes for nucleic-acid labelling: absorption and fluorescence spectral characteristics

… of Photochemistry and …, 2000

Absorption spectra and fluorescence properties of a series of newly synthesized asymmetric monome... more Absorption spectra and fluorescence properties of a series of newly synthesized asymmetric monomethine cyanine dyes are studied. The dyes carry one or two positive charges. They are devoid of their own fluorescence in solution and become fluorescent upon binding to nucleic acids only. The fluorescence maxima of the new dyes are localized between 530 and 650 nm. The wavelength and intensity of fluorescence are dependent on molecular structure of the dye, type of nucleic acid and the concentration of both nucleic acid and salts. Some of the dyes are capable of distinguishing between single-stranded and double-stranded (ds) polynucleotides giving fluorescence maxima localized at different wavelengths. Detection threshold for dsDNA for most of the dyes is comparable to that of ethidium bromide. The sensitivity of the dye-dsDNA complexes to NaCl concentrations show that the new dyes interact with dsDNA by both intercalation and electrostatically.

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Petko Ivanov

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