Structural features specific to plant metallothioneins

The metallothionein (MT) superfamily combines a large variety of small cysteine-rich proteins from nearly all phyla of life that have the ability to coordinate various transition metal ions, including ZnII, CdII, and CuI. The members of the plant MT family are characterized by great sequence diversity, requiring further subdivision into four subfamilies. Very peculiar and not well understood is the presence of rather long cysteine-free amino acid linkers between the cysteine-rich regions. In light of the distinct differences in sequence to MTs from other families, it seems obvious to assume that these differences will also be manifested on the structural level. This was already impressively demonstrated with the elucidation of the three-dimensional structure of the wheat Ec-1 MT, which revealed two metal cluster arrangements previously unprecedented for any MT. However, as this structure is so far the only one available for the plant MT family, other sources of information are in high demand. In this review the focus is thus set on any structural features known, deduced, or assumed for the plant MT proteins. This includes the determination of secondary structural elements by circular dichroism, IR, and Raman spectroscopy, the analysis of the influence of the long linker regions, and the evaluation of the spatial arrangement of the sequence separated cysteine-rich regions with the aid of, e.g., limited proteolytic digestion. In addition, special attention is paid to the contents of divalent metal ions as the metal ion to cysteine ratios are important for predicting and understanding possible metal-thiolate cluster structure

"To move wild laughter in the throat of death" : an anatomy of Black Humor

Includes vita.This dissertation presents an extended definition of a literary genre that has been labelled "Black Humor" by many contemporary critics. Though the phrase has been used with increasing frequency in the last ten years, it has not yet been satisfactorily defined. This study examines thoroughly the identity of the Black Humorist and the chemistry of his art in order to provide the satisfactory definition which is at present so badly needed. Although the dissertation does not consider every novelist who has been called a Black Humorist, it does draw from the work of approximately fourteen novelists, including John Barth, Stanley Elkin, Bruce Jay Friedman, Joseph Heller, Ken Kesey, Walker Percy, Thomas Pynchon, and Kurt Vonnegut. The informing structure for the study is Kenneth Burke’s pentad of key terms. In A Grammar of Motives Burke develops his pentad as the generating principle for his investigation of human motives. The five terms of the pentad are Act (what took place), Agent (who performed the Act), Scene (the situation in which the Act occurred), Agency (the means used), and Purpose (the reasons for which the Act was performed). The dissertation focuses on who the Black Humorist is, when he writes, what world view dominates the scene of his fiction, what literary modes he employs, and what goals he seeks to accomplish. Chapter One provides an overview of the literary history of the label, with special attention to the controversy which the term has stimulated and to the inadequacies of the major attempts at defining it. Chapter Two examines Act/Agent and Scene. Act here refers to Black Humor itself, the act of writing in that particular mode. Agent refers to the Black Humorist. The first two components of the pentad are treated together in order to advance the viewpoint that Black Humor has appeared in literary periods other than the twentieth century. The section on Scene discusses these six assumptions which constitute the Black Humorist’s world view: (1) That the world is absurd; (2) That man is the victim of some vague, sinister conspiracy; (3) That the Self has been lost or heavily masked; (4) That "society is sterile, reductive, and confining, a conviction projected repeatedly through controlling metaphors of the waste land, the asylum, and the prison; (5) That man is threatened by technology; and (6) That the world may be at, or near, the Apocalypse. The apocalyptic vision of the Black Humorist ranges from Nathanael West’s and Vonnegut’s traditional images of fire, war, plague, and riots to the entropy-induced Apocalypse of Pynchon. Chapter Three examines Agency in Black Humor. After an initial consideration of the relationship between traditional comic theory and Black Humor, the chapter asserts that the three major agencies of the Black Humorist are satire, gallows humor, and the grotesque. Most critics who have attempted to define Black Humor either deny the relevance of satire and the grotesque or they assume the relevance without specifically anatomizing the relationship. This chapter rejects both of these approaches by studying the three agencies separately and then establishing the connection between each of these genres and Black Humor. Chapter Four investigates the Purpose of Black Humor, concluding that the aim if two-fold: to promote laughter and to instill a qualified hope that humanity can at least cope with the world's absurdity and thereby survive. The chapter stresses the therapeutic value of laughter and the presence in all Black Humor of some degree of hope, ranging from the life-affirming symbolic gestures of Heller and Kesey to the extremely muted hope of Barth and Pynchon.Includes bibliographical references

Plato's Breath

May Swenson Poetry Award Volume 1 with foreward by Herbert Leibowitz. Freisinger's new poetry collection is inhabited alike by bright, tangible images and thoughtful, intricate meditations. Pumpkins, poultry houses, sperm tests, a vacuum cleaner salesman, a father's damaged brain, an anatomist's tools, a baby falling from a fourth-story window-all of these come to the page distinct and palpable. At the same time, the work finds a central inspiration in theoretical work like Jeremy Rifkin's social criticism. Poetry of both the mind and the heart, Plato's Breath embraces the power of imagination to transform the ordinary into an extraordinary affirmation of life

An optimized intein-mediated protein ligation approach for the efficient cyclization of cysteine-rich proteins

Head-to-tail backbone cyclization of proteins is a widely used approach for the improvement of protein stability. One way to obtain cyclic proteins via recombinant expression makes use of engineered Intein tags, which are self-cleaving protein domains. In this approach, pH-induced self-cleavage of the N-terminal Intein tag generates an N-terminal cysteine residue at the target protein, which then attacks in an intramolecular reaction the C-terminal thioester formed by the second C-terminal Intein tag resulting in the release of the cyclic target protein. In the current work we aimed to produce a cyclic analog of the small γ-Ec-1 domain of the wheat metallothionein, which contains six cysteine residues. During the purification process we faced several challenges, among them premature cleavage of one or the other Intein tag resulting in decreasing yields and contamination with linear species. To improve efficiency of the system we applied a number of optimizations such as the introduction of a Tobacco etch virus cleavage site and an additional poly-histidine tag. Our efforts resulted in the production of a cyclic protein in moderate yields without any contamination with linear protein specie

Metal ion binding properties of Triticum aestivum Ec-1 metallothionein: evidence supporting two separate metal thiolate clusters

Metallothioneins are ubiquitous low molecular mass, cysteine-rich proteins with an extraordinary high metal ion content. In contrast to the situation for the vertebrate forms, information regarding the properties of members of the plant metallothionein family is still scarce. We present the first spectroscopic investigation aiming to elucidate the metal ion binding properties and metal thiolate cluster formation of the Tricium aestivum (common wheat) early cysteine-labeled plant metallothionein (Ec-1). For this, the protein was overexpressed recombinantly in Escherichia coli. Recombinant Ec-1 is able to bind a total of six divalent d 10 metal ions in a metal thiolate cluster arrangement. The pH stability of the zinc and cadmium clusters investigated is comparable to stabilities found for mammalian metallothioneins. Using cobalt(II) as a paramagnetic probe, we were able to show the onset of cluster formation taking place with the addition of a fourth metal ion equivalent to the apo protein. Limited proteolytic digestion experiments complemented with mass spectrometry and amino acid analysis provide clear evidence for the presence of two separate metal thiolate clusters. One cluster consists of four metal ions and is made up by a part of the protein containing 11 cysteine residues, comparable to the situation found in the mammalian counterparts. The second cluster features two metal ions coordinated by six cysteine residues. The occurrence of the latter cluster is unprecedented in the metallothionein superfamily so fa

Metal ion binding properties of Tricium aestivum Ec-1 metallothionein: evidence supporting two separate metal thiolate clusters

Metallothioneins are ubiquitous low molecular mass, cysteine-rich proteins with an extraordinary high metal ion content. In contrast to the situation for the vertebrate forms, information regarding the properties of members of the plant metallothionein family is still scarce. We present the first spectroscopic investigation aiming to elucidate the metal ion binding properties and metal thiolate cluster formation of the Tricium aestivum (common wheat) early cysteine-labeled plant metallothionein (Ec-1). For this, the protein was overexpressed recombinantly in Escherichia coli. Recombinant Ec-1 is able to bind a total of six divalent d 10 metal ions in a metal thiolate cluster arrangement. The pH stability of the zinc and cadmium clusters investigated is comparable to stabilities found for mammalian metallothioneins. Using cobalt(II) as a paramagnetic probe, we were able to show the onset of cluster formation taking place with the addition of a fourth metal ion equivalent to the apo protein. Limited proteolytic digestion experiments complemented with mass spectrometry and amino acid analysis provide clear evidence for the presence of two separate metal thiolate clusters. One cluster consists of four metal ions and is made up by a part of the protein containing 11 cysteine residues, comparable to the situation found in the mammalian counterparts. The second cluster features two metal ions coordinated by six cysteine residues. The occurrence of the latter cluster is unprecedented in the metallothionein superfamily so fa

The Bioinorganic Periodic Table

Life depends on metals. While carbon, in terms of abundance and versatility, is considered THE element of life, the vast variety and diversity of the chemistry taking place in living organisms could not be achieved without metal ions. More than twenty metals are found in the human body, most of them being essential, some beneficial, and for others it is still unknown what role they might fulfil in a living cell. Here we give a short introduction into the bioinorganic world of the periodic table, providing just a few examples of key metals for life and aiming to give a flavour to gain further insights into this exciting field of inorganic chemistry at the intersection to the life sciences

The adoption of algorithmic decision-making agents over time: algorithm aversion as a temporary effect?

Many individuals encounter algorithmic decision-making agents with algorithm aversion – the irrational discounting of superior algorithmic advice. So far, we know little about how algorithm adoption develops over time and how people may overcome algorithm aversion. In response, we explore the factors that foster the adoption of algorithmic decision-making agents – initially and over time. Based on an experiment with incentive-compatible awards over several rounds, we find that one’s knowledge about peers successfully using the technology as well as low transaction costs serve as strong initial motivators to foster initial algorithm adoption. Further, by revealing that adoption rates increase and initial difference in adoption rates become smaller over time, we find evidence that despite the technology’s particularities, algorithm aversion seems to have a temporary effect only

Business Model Innovation Through the Lens of Time: An Empirical Study of Performance Implications Across Venture Life Cycles

Current literature suggests that the innovation of a business model is among the most important success factors for organizations and has a positive influence on their performance. What is not yet clear, however, is how this relationship unfolds during an organization’s life cycle. We posit that business model innovation strongly contributes to firm performance in earlier phases, but ultimately gets less important. We therefore collected data on 250 organizations in Germany and used structural equation modeling for analytical purposes. We make the following two main contributions to the literature: (1) We confirm recent findings about the positive impact of business model innovation on performance; (2) we provide first empirical evidence for the important role of life cycle stages as moderator with regard to this relationship. With respect to the latter, our findings show that business model innovation is an important pathway of organizations, especially in their early years of existence, yet somewhat diminishing over time. In conclusion, this study opens new research avenues by extending and incorporating explanations for the life cycle theory and business model innovation