111,835 research outputs found
Mass Spectrometric Sequencing Of Acyclic And Cyclic Peptides
No full textElucidation of the primary structure of peptides and proteins de novo by mass spectrometry (MS) has become possible with the advent of tandem MS methods. The most widely used chemical method due to Edman (Edman & Begg, 1967) has shortcomings with regard to N- terminal blocked peptides, cyclic peptides and posttranslational modifications, for example phosphorylation (Metzger, 1994). However, mass spectrometric sequencing methods are increasingly becoming applicable for a variety of peptides and proteins, including N- and C- termini modified peptides and cyclic peptides (Jegorov et al., 2003; Sabareesh & Balaram, 2006; Sabareesh et al., 2007). Further, conventional and tandem mass spectrometry have proven useful in the detection of post-translational modifications (Hansson et al., 2004; Nair et al., 2006; Mandal et al., 2007). This thesis details mass spectrometric sequencing of acyclic and cyclic peptides, involving tandem MS methods carried out using both electrospray ionization (ESI) ion trap (Esquire 3000 plus, Bruker Daltonics) and matrix assisted laser desorption and ionization time-of-flight/time-of-flight (MALDI TOF/TOF) (Ultraflex TOF/TOF, Bruker Daltonics) instruments. The peptides are either chemically synthesized or isolated from diverse natural sources. Synthetically designed peptides possessing modified N- and C- termini and peptaibols from the soil fungus Trichoderma constitute the acyclic peptides. The cyclic peptides include backbone cyclized depsipeptides from the fungus Isaria and disulfide bonded peptides from the venom of marine cone snails.
Chapter 1 gives an account of various concepts of mass spectrometry, tandem mass spectrometry and peptide fragmentation chemistry, providing necessary background information for the following chapters.
Chapter 2 describes the fragmentation studies of [M + H]+ and [M + Na]+ adducts of six neutral peptides with blocked N- and C- termini investigated using an electrospray ion trap mass spectrometer. The N- terminus of these synthetically designed peptides is blocked with a tertiarybutyloxycarbonyl (Boc) group and the C- terminus is esterified. These peptides do not possess sidechains that are capable of complexation and hence the backbone amide units are the sole sites of protonation and metallation. The cleavage pattern of protonated adducts is strikingly different from that of sodium adducts. While the loss of the N- terminal blocking group happens quite readily in the case of MS/MS of [M + Na]+, the cleavage of C- terminal methoxy group seems to be a facile process in the case of MS/MS of [M + H]+. Fragmentation of the protonated adducts yields only bn ions, while yn and an type ions are predominantly formed from the fragmentation of sodium adducts. The an ions arising from the fragmentation of [M + Na]+ lack the N-terminal Boc group (termed as an*). MS/MS of [M + Na]+ species also yields bn ions of substantial lower intensities, that lack the N- terminal Boc group (bn*). Comparison of the fragmentation of [M + H]+ with [M + Na]+ of the peptides chosen in this study reveal that the combined use of both protonated and sodium adducts should prove useful in de novo sequencing of peptides that possess modified N- and C- termini, particularly naturally occurring neutral peptides, for example, peptaibols.
Chapter 3 describes about the ESI-MS/MS investigation of an HPLC fraction from the soil fungus Trichoderma, which aided in identification of microheterogeneous trichotoxin peptaibols in that fraction. Dramatic differences were noted between the fragmentation spectra of [M + H]+ and [M + Na]+ species. While b-type ions were noted from the former, the latter yielded a-, b-and y- type ions (the same feature was noted in the cases presented in the previous chapter). Inspection of the isotope pattern of b-ions yielded from the dissociation of H+ species, clearly revealed the presence of three microheterogeneous trichotoxin sequences; two isobars (1718 Da), each possessing one Glu residue and another completely neutral peptide (1717 Da). The microheterogeneity is due to Gly ↔ Ala, Iva ↔ Aib and Gln ↔ Glu replacements and exchanges (Iva: DIva: R-Isovaline; Aib: α-aminoisobutyric acid). The MS/MS of [M + Na]+ adduct predominantly yielded product ions from the neutral peptaibol. Further, the fragmentation patterns of H+ and Na+ adducts of two N-acetyl peptide esters were found to be very similar to that of the neutral peptaibol component. The results presented in this chapter establish that under the electrospray ion trap conditions, the fragmentation patterns of the H+ and Na+ adducts of model peptides that possess modified N- (Boc and acetyl) and C- termini are indeed very similar to that of the neutral trichotoxin.
Chapter 4 delineates the applicability of liquid chromatography coupled to conventional and tandem electrospray ionization mass spectrometry (LC-ESI-MS, LC-ESI-MS/MS, LC-ESI-MS3) for the screening of novel cyclic hexadepsipeptide metabolites directly from the crude hyphal extract of the fungus Isaria. The fungal strain was grown on a solid medium (potato carrot agar), which yields aerial hyphae growing erect from the basal mycelial colony (Ravindra et al., 2004). A total of ten microheterogeneous components were identified to belong to the isariin class of cyclodepsipeptides from the LC-ESI-MS and LC-ESI-MS/MS analysis of the crude hyphal extract. Out of ten, six are determined to be new and the remaining four are previously reported isariins A-D. The primary structures of isariins A-D were from the fungi Isaria cretacea and Isaria felina (Vining & Taber 1962; Deffieux et al., 1981) and the fungal strain used in this study resembles Isaria felina (Sabareesh et al., 2007). Isariins are backbone cyclized hexadepsipeptides composed of a D-β-hydroxy acid possessing a hydrocarbon sidechain and five α-amino acids; one of the α-amino acids is a D-amino acid (Vining & Taber 1962; Deffieux et al., 1981). The detection of fragment ions due to loss of CO concomitant with the loss of H2O from the protonated precursor ion ([M + H]+) ascertained the cyclic depsipeptide nature of both the known and the new components. The fragmentation behavior of the [M + H]+ of known isariins facilitated sequence determination of the new components. Therefore, the configuration of the amino acids and the β-hydroxy acid of the new components is assumed to be same as that of the reported peptides. The microheterogeneity of the ten sequences is due to changes in the D-β-hydroxy acid (residue 1) and the adjoining α-amino acid (residue 6), whose carbonyl is linked to the hydroxyl function by an ester linkage. The number of methylene units ((-CH2)n) in the hydrocarbon sidechain of the residue 1 differs between 2 and 8 and the variability of the residue 6 is limited to Ala/Val. The ester oxygen atom was chosen as the preferable site of protonation causing ring-opening, based on the observed distribution of the fragment ions.
Chapter 5 demonstrates the utility of the LC-ESI-MS and LC-ESI-MS/MS methods in the identification and characterization of six microheterogeneous backbone cyclized hexadepsipeptides, isaridins, directly from the crude hyphal extract of the fungus Isaria. Among the six components, four were found to be novel. The other two peptides, isaridins A and B were identified earlier from this laboratory (Ravindra et al., 2004). The isaridins are characterized by the presence of unusual amino acids such as N-methylated residues, β-methylproline (β-MePro) and hydroxyleucine (HyLeu) (Ravindra et al., 2004). The cyclic nature of both the known and the new peptides were confirmed from the observation of peaks due to loss of CO and H2O from the protonated precursor ion ([M + H]+). However, unlike isariins (Chapter 4), the intensity of the peak corresponding to [M + H - H2O]+ was noted to be of very low intensity, in the case of isaridins. Detection of product ion peak due to [M + H - CO2]+ suggests an additional dissociation pathway involving cleavage at the depsipeptide linkage and is supportive of the cyclic depsipeptide nature (Eckart, 1994). The sequencing of the newly detected components was enabled by understanding the fragmentation mechanism of the known isaridins. The tertiary amide nitrogens of the N-methylated residues were regarded as the preferable sites of protonation leading to ring-opening, as noted from the fragmentation spectra. The microheterogeneity in the sequences was identified using the diagnostic product ions obtained from the protonated precursor of the known isaridins. The microheterogeneity can be attributed to the variations of two residues; Pro ↔ β-MePro and N-MePhe ↔ N-MeLxx (Lxx: Leu, Ile, alloIle). The recently reported ‘isarfelins’ from the fungus Isaria felina (Guo et al., 2005) were reassigned as ‘isaridins’. The reassignment was based on very similar fragmentation profiles observed for the [M + Na]+ adduct of isaridins and isarfelins; further, the fungal strain used in this study resembles Isaria felina (Sabareesh et al., 2007).
Chapter 6 presents mass spectrometric sequencing of disulfide bonded peptides from marine cone snails (conopeptides), using the MALDI LIFT MS/MS method. Lo959, a single disulfide bonded octapeptide isolated from Conus loroisii, was identified to belong to the class of contryphans (Sabareesh et al., 2006). Contryphans are small single disulfide bonded conopeptides, whose length is in the range of 7-11 residues and are rich in tryptophan. A significant feature of the contryphans is the presence of conserved DTrp (DW) at the 3rd residue within the disulfide loop (Sabareesh et al., 2006). Lo959 displays an unusual behavior under reverse phase chromatographic conditions, typical of the DW containing contryphans (Jacobsen et al., 1998). It undergoes slow conformational interconversion on the chromatographic time scale exhibiting two distinct peaks. The presence of DW at the 4th position in Lo959 was established by comparing the chromatographic profiles of natural peptide with that of two chemically synthesized peptides, one containing LW (4) and another possessing DW (4). De novo sequencing of the two peptides Ar1446 and Ar1430 from Conus araneosus established that they belonged to M-superfamily of conotoxins, in particular m-2 branch. M-superfamily conotoxins are three-disulfide bonded peptides characterized by the consensus cysteine framework, CC…C…C…CC (Corpuz et al., 2005). Ar1446 and Ar1430 are fourteen residue long peptides, each possessing three disulfide bonds. The peptides have the cysteine scaffold typical of the M-superfamily, as shown above. Specifically, the peptides belong to m-2 branch of M-superfamily, where the fourth and fifth cysteines are separated by two residues (Corpuz et al., 2005). The sequences of the peptides were derived following chemical and enzymatic modifications. The carboxamidomethylation reaction established the presence of three disulfide bonds. Indeed, the sequences were deduced from the MALDI LIFT MS/MS of [M + H]+ of the tryptic peptides. The sequences of the two peptides are almost identical and they differ only at residue 12; hydroxyproline in Ar1446, proline in Ar1430
author-bios-SRD-19-0063.R1 – Supplemental material for The Network Structure of Police Misconduct
No full textSupplemental material, author-bios-SRD-19-0063.R1 for The Network Structure of Police Misconduct by George Wood, Daria Roithmayr and Andrew V. Papachristos in Socius</p
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Využití sociálních médií v B2B prodeji
No full textTato diplomová práce se zabývá tím, jak mohou B2B obchodníci využívat sociální média v prodeji. Na základě systematické rešerše literatury, autor zjistil, že akademici, zkoumající danou problematiku, navrhují další výzkum, a to: v kterých konkrétních krocích se dají využít sociální média v prodeji (Salo, 2017). Autor se na základě toho rozhodl zjistit, jaké sociální sítě, různé technologie a pluginy se dají využít v B2B prodeji - tzv. social sellingu. Social selling se v této práci týká primárně procesu akvizice a okrajově péčí o stávající zákazníky. Autor si vybral kvalitativní průzkum pomocí 10 hloubkových polo-strukturovaných rozhovorů, aby odhalil jak, která sociální média to jsou, tak i motivaci prodejců, proč tato média používat/nepoužívat. Aby autor dodržel správnost vyhodnocení výsledků, data byla analyzována pomocí Tématické analýzy, která v této studii vykrystalizovala 2 hlavní strategické přístupy v social sellingu. Tyto přístupy (tzv. Push a Pull strategie) obsahují praktické příklady a konkrétní aktivity, které mohou prodejci využívat v každodenní praxi. Tyto výsledky jsou prezentovány s důrazem na praktičnost a jednoduchost implementace. Tvoří proto hlavní přínos autorovo výzkumu. V poslední části autor zmiňuje výzvy a manažerská doporučení, které mohou obchodníci využít v každodenním pracovním životě.This diploma thesis focuses on social media usage in B2B sales. Based on the systematic literature review conducted by the author, he has found out that recent researchers (Salo, 2017) suggest further research in the area of how and in which sales phase should various social networking sites, technologies and plugins used. To further fill this research gap, author decided to identify these social media and their usage among B2B salespeople in the so-called social selling process. The social selling process in this thesis applies mainly to acquiring new prospects and tangentially to taking care of existing clients (follow-up step). Author has chosen a qualitative research method via conducting 10 in-depth semi-structured interviews to reveal these instruments as well as motivation of a sales person on why to use social media in the selling process. The collected data was analyzed using Thematic analysis to ensure the right procedure and to identify main themes which crystalized into 2 main strategic approaches in social selling. These approaches (Push and Pull) include practical examples of concrete activities which sales people can use in their daily jobs and are presented with focus on practicality and ease of implementation. These also form the main contribution of author`s research. In the last part, author mentions challenges in social selling and recommended managerial implications for salesforce
TeX v jednoduchém unixovém prostředí
No full textsummary:Při ladění TeXového dokumentu potřebujeme mnohokrát opakovaně pouštět TeX, podívat se, jak dopadl výsledek v prohlížeči DVI nebo PDF souboru, mrknout na výpis TeXu na terminálu, podívat se případně do logu a celou činnost opakovat. V tomto článku je ukázáno, jak tuto práci dělá autor článku. Proces "editor-TeX-kuk" je zde podporován jednoduchými unixovými nástroji: bashovým skriptem texloop, který si autor pro tyto účely vytvořil, dále terminálem Xterm a jednoduchým editorem, který umí navázat na klávesovou zkratku spuštění příkazu v systému. Čtenář se zde může inspirovat a přizpůsobit tyto nástroje svým vlastním potřebám. V článku je popsána funkce skriptu texloop, dále je neformálně rozveden dlouholetý vývoj autorova vztahu k textovým editorům a konečně je zde uvedena konfigurace terminálu Xterm, aby vyhovoval českému prostředí jak v kódování ISO-8859-2, tak v kódování UTF-8. Pro kódování UTF-8 si v závěru článku vygenerujeme TeXový formát csplain.summary:By debugging a TeX document it is necessary many times repeatedly to run TeX, to look for the result in DVI or PDF file, to gander the TeX output on the terminal, or eventually to have a look in the log-file, and all that action to repeat. In the paper it is show, how this work is made by author. The process '‘'editor-TeX-look' is supported by simple Unix tools: bash script texloop, created by author for these purposes, Xterm terminal and a simple editor, which is able to link to the shortcut key the activation of a system command. The reader could be inspired with the solution and to adapt these tools to his/her own needs. In the paper the function of the texloop script is described, and further the longstanding evolution of the author's relation to text editors is informal elaborated and finally a configuration of Xterm terminal, suitable for the czech environment with both ISO-8859-2 and UTF-8 encoding is introduced. For UTF-8 encoding the TeX format csplain is generated at the end of the paper
Spin dynamics in the single-ion magnet [Er(W5O18)2]9−
No full textIn this work we present a detailed NMR and μ+SR investigation of the spin dynamics in the new hydrated sodium salt containing the single-ion magnet [Er(W5O18)2]9-. The H1NMR absorption spectra at various applied magnetic fields present a line broadening on decreasing temperature which indicates a progressive spin freezing of the single-molecule magnetic moments. The onset of quasistatic local magnetic fields, due to spin freezing, is observed also in the muon relaxation curves at low temperature. Both techniques yield a local field distribution of the order of 0.1-0.2 T, which appears to be of dipolar origin. On decreasing the temperature, a gradual loss of the H1NMR signal intensity is observed, a phenomenon known as wipe-out effect. The effect is analyzed quantitatively on the basis of a simple model which relies on the enhancement of the NMR spin-spin, T2-1, relaxation rate due to the slowing down of the magnetic fluctuations. Measurements of spin-lattice relaxation rate T1-1 for H1NMR and of the muon longitudinal relaxation rate λ show an increase as the temperature is lowered. However, while for the NMR case the signal is lost before reaching the very slow fluctuation region, the muon spin-lattice relaxation λ can be followed until very low temperatures and the characteristic maximum, reached when the electronic spin fluctuation frequency becomes of the order of the muon Larmor frequency, can be observed. At high temperatures, the data can be well reproduced with a simple model based on a single correlation time τ=τ0exp(Δ/T) for the magnetic fluctuations. However, to fit the relaxation data for both NMR and μ+SR over the whole temperature and magnetic field range, one has to use a more detailed model that takes into account spin-phonon transitions among the Er3+ magnetic sublevels. A good agreement for both proton NMR and μ+SR relaxation is obtained, which confirms the validity of the energy level scheme previously calculated from an effective crystal field Hamiltonian
Analýza perspektivy vedoucích prodeje na řízení pojišťovacích agentů v etnicky různorodých zastoupeních v Organizaci G, Malajsie.
No full textCílem této práce je odhalit klíčové faktory a výzvy spojené s řízením etnicky různorodého pojišťovacího zastoupení v oboru životního pojištění v Malajsii. Autor si klade za cíl zkoumat pohled vedoucích prodeje v Organizaci G v Malajsii na jejich způsob řízení agentů. Kombinované kvantitativní a kvalitativní metody budou použity prostřednictvím průzkumu a rozhovorů se 79 agenty a 12 vedoucími prodeje. Odpovědi budou analyzovány za účelem porozumění výzvám, kterým čelí vedoucí prodeje při řízení etnicky různorodého zastoupení, a zkoumat potenciální řešení. Autor navrhuje iniciativy a metody k posílení stylů vedení a zlepšení procesů pro udržení úspěšného zastoupení v kontextu etnické rozmanitosti.The goal of this thesis is to uncover the key factors and challenges in managing an ethnically diverse insurance agency in Malaysia's life insurance industry. The author aims to examine the sales managers' perspective in Organisation G, Malaysia, regarding their expression of managing their agents. Quantitative and qualitative methods will be employed through surveys and interviews among 79 agents and 12 sales managers. The responses will be analysed to understand the challenges sales managers face in managing a multi-ethnic agency and explore potential solutions. The author proposes initiatives and methods to enhance leadership styles and improve the processes for maintaining a successful agency in the context of multi-ethnicity
AUTHOR BOOK
No full textVytvořil jsem autorskou knihu o čtyřiceti stránkách s ilustracemi a minimem textu. Kniha je černobílá, dominuje v ní tušová kresba štětcem a perem. Kromě té je v knize ale i text, který slouží jako poetické doplnění ilustrací.
Obsah knihy se zaměřuje na úzký kruh přátel a zároveň vypovídá o autorovi jak vybranými motivy, situacemi tak linkou.
Vyznění knihy je spíše pocitové, má zanechat dojem, ne popisně vysvětlovat.ObhájenoI have created author book that has 40 pages with ilustrations and minimum of text. The book is black and white and contains ink drawings. There is also text poetically coresponding with pictures
Genderová nerovnost v odměňování v Kazachstánu
No full textBakalářská práce sleduje problematiku genderové nerovnosti v odměňování se zaměřením na Kazachstán. Cílem práce je analýza genderové nerovnosti v odměňování zaměstnanců konkrétní společnosti X. Teoretická část se zaměřuje na důvody existence genderové nerovnosti ze sociologického a ekonomického hlediska. Pozornost je věnována genderové politice a historii vzniku genderové nerovnosti v Kazachstánu, jakož i rozdílům ve mzdách žen a mužů v Kazachstánu. V rámci vlastního výzkumu využila autorka kvantitativní metod. Výzkum sleduje vztah mezi pohlavím a mzdou ve firmě X. Název společnosti neuveden v práci z důvodu ochrany dat. Výsledná zjištění ukazují na nerovnost v odměňování žen a mužů ve společnosti X od roku 2015 do roku 2018. Výsledky slouží k formulaci doporučení, které by mohly přispět k redukci genderových nerovností ve mzdách ve firmě X.This bachelor thesis analyzes the problem of gender inequality in terms of wages in Kazakhstan. The thesis aims to study the problem of gender inequality and to reveal it on the example of wages of company X's employees. The theoretical basis of the thesis focused on reasons for the existence of gender inequality from sociological and economic points of view, gender policy and history of the formation of gender inequality in Kazakhstan, as well as on differences in female and male wages in Kazakhstan. The author used quantitative method for the research in the practical part. The research investigates the relationship between gender and wage in company X. In order to support data protection rules and desire of the company X to maintain privacy, the name of the organization was not revealed in the current thesis. Results showed the persistent existence of the gender pay inequalities in company X from 2015 to 2018. The findings of the current research serve to provide recommendations for the reduction of gender inequalities in terms of wages in company X
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