Cycloviolacin H4, a hydrophobic cyclotide from Viola hederaceae

Cycloviolacin H4, a new macrocyclic miniprotein comprising 30 amino acid residues, was isolated from the underground parts of the Australian native violet Viola hederaceae. Its sequence, cyclo-(CAESCVWIPCTVTALLGCSCSNNVCYNGIP), was determined by nanospray tandem mass spectrometry and quantitative amino acid analysis. A knotted disuffide arrangement, which was designated as a cyclic cystine knot motif and characteristic to all known cyclotides, is proposed for stabilizing the molecular structure and folding. The cyclotide is classified in the bracelet subfamily of cyclotides due to the absence of a cis-Pro peptide bond in the circular peptide backbone. A model of its three-dimensional structure was derived based on the template of the homologous cyclotide vhr1 (Trabi et al. Plant Cell 2004, 16, 2204-2216). Cycloviolacin H4 exhibits the most potent hemolytic activity in cyclotides reported so far, and this activity correlates with the size of a surface-exposed hydrophobic patch. This work has thus provided insight into the factors that modulate the cytotoxic properties of cyclotides.

Discovery and characterization of a linear cyclotide from Viola odorata: Implications for the processing of circular proteins

Cyclotides are mini-proteins of 28-37 amino acid residues that have the unusual feature of a head-to-tail cyclic backbone surrounding a cystine knot. This molecular architecture gives the cyclotides heightened resistance to thermal, chemical and enzymatic degradation and has prompted investigations into their use as scaffolds in peptide therapeutics. There are now more than 80 reported cyclotide sequences from plants in the families Rubiaceae, Violaceae and Cucurbitaceae, with a wide variety of biological activities observed. However, potentially limiting the development of cyclotide-based therapeutics is a lack of understanding of the mechanism by which these peptides are cyclized in vivo. Until now, no linear versions of cyclotides have been reported, limiting our understanding of the cyclization mechanism. This study reports the discovery of a naturally occurring linear cyclotide, violacin A, from the plant Viola odorata and discusses the implications for in vivo cyclization of peptides. The elucidation of the cDNA clone of violacin A revealed a point mutation that introduces a stop codon, which inhibits the translation of a key Asn residue that is thought to be required for cyclization. The three-dimensional solution structure of violacin A was determined and found to adopt the cystine knot fold of native cyclotides. Enzymatic stability assays on violacin A indicate that despite an increase in the flexibility of the structure relative to cyclic counterparts, the cystine knot preserves the overall stability of the molecule. (c) 2006 Elsevier Ltd. All rights reserved.

A novel suite of cyclotides from Viola odorata: sequence variation and the implications for structure, function and stability

Cyclotides are a fascinating family of plant-derived peptides characterized by their head-to-tail cyclized backbone and knotted arrangement of three disulfide bonds. This conserved structural architecture, termed the CCK (cyclic cystine knot), is responsible for their exceptional resistance to thermal, chemical and enzymatic degradation. Cyclotides have a variety of biological activities, but their insecticidal activities suggest that their primary function is in plant defence. In the present study, we determined the cyclotide content of the sweet violet Viola odorata, a member of the Violaceae family. We identified 30 cyclotides from the aerial parts and roots of this plant, 13 of which are novel sequences. The new sequences provide information about the natural diversity of cyclotides and the role of particular residues in defining structure and function. As many of the biological activities of cyclotides appear to be associated with membrane interactions, we used haemolytic activity as a marker of bioactivity for a selection of the new cyclotides. The new cyclotides were tested for their ability to resist proteolysis by a range of enzymes and, in common with other cyclotides, were completely resistant to trypsin, pepsin and thermolysin. The results show that while biological activity varies with the sequence, the proteolytic stability of the framework does not, and appears to be an inherent feature of the cyclotide framework. The structure of one of the new cyclotides, cycloviolacin O14, was determined and shown to contain the CCK motif. This study confirms that cyclotides may be regarded as a natural combinatorial template that displays a variety of peptide epitopes most likely targeted to a range of plant pests and pathogens.

A graduate viola recital with extended program notes

The extended program notes include historical facts of the composers and characteristics of the pieces being performed. The graduate viola recital will include the following works: Concerto in D-Major by Franz Anton Hoffmeister, Suite No. I in G-Major by Johann Sebastian Bach, and Sonata in A-Minor (Arpeggione) by Franz Schubert.

Sugestões performáticas do bilhete de um jogral para viola sozinha e das três peças para viola e piano de César Guerra-Peixe

This work is aimed at providing an interpretive study of the work for viola and piano titled Three Pieces, and work for solo viola titled Ticket of a Jogral, by Brazilian composer César Guerra Peixe. This study will be divided into three parts: The first will bring a brief history of the composer focusing on his visit to Pernambuco in the late 1940s and early 1950s; the second shows the use of Pernambuco musical regionalism elements used by the composer in the aforementioned documents; the third will present a set of interpretive suggestions based: the analysis of regional musical elements identified in these works; the technical rudiments used in writing for viola depicting the arcades, dynamics, fingerings, articulations, phrasing; and the experiences lived by the author of this research as an interpreter of these works.

Sugestões performáticas do bilhete de um jogral para viola sozinha e das três peças para viola e piano de César Guerra-Peixe

This work is aimed at providing an interpretive study of the work for viola and piano titled Three Pieces, and work for solo viola titled Ticket of a Jogral, by Brazilian composer César Guerra Peixe. This study will be divided into three parts: The first will bring a brief history of the composer focusing on his visit to Pernambuco in the late 1940s and early 1950s; the second shows the use of Pernambuco musical regionalism elements used by the composer in the aforementioned documents; the third will present a set of interpretive suggestions based: the analysis of regional musical elements identified in these works; the technical rudiments used in writing for viola depicting the arcades, dynamics, fingerings, articulations, phrasing; and the experiences lived by the author of this research as an interpreter of these works.

Der sterbende Jesus in einer Cantata : à basso solo con 2 hautbois, 2 violini, 1 viola, violoncello et organo

di Telemann

Introdução à música contemporânea portuguesa de viola d’arco : um estudo de caso

Esta dissertação baseia-se no estudo da introdução da música contemporânea portuguesa de viola d’arco num grupo de alunos de viola d’arco da Casa Pia de Lisboa, através de composições encomendadas a nove compositores portugueses. Incide também na análise das atitudes em relação à música contemporânea portuguesa por parte de professores de viola d’arco portugueses. Procurou-se ampliar o repertório da viola d’arco através da encomenda de obras didáticas, e o repertório expressivo dos alunos envolvidos. Verificou-se que a introdução tardia da música contemporânea no ensino da música e a desatualização dos programas podem condicionar a atitude dos músicos em relação à mesma, sendo importante uma mudança de paradigma. Parecem não existir dificuldades técnicas na abordagem a estas obras por parte dos alunos. Houve também uma aceitação por parte dos professores em introduzir estes conceitos, tendo existido igualmente uma abertura por parte dos compositores contemporâneos envolvidos, em criar obras didáticas para viola d’arco.

NEW PERSPECTIVES: TRANSCRIPTIONS FOR VIOLA

One must only glance upon Franz Zeyringer’s 400-page, exhaustive Literatur für Viola to understand the error of the familiar but casual criticism of the paucity of the viola catalogue. Examining Zeyringer’s resource, however, we find a trend: while the viola repertoire contains many pieces (over 14,000 works) and does lay claim to many masterworks (Bartok’s Viola Concerto, Hindemith’s Sonatas, Mozart’s Sinfonia Concertante, etc.), many of the pieces originally written for the instrument are not widely recognized compositions and not often considered outstanding achievements. The violist, much like the double-bassist, bassoonist, and hornist, faces a certain challenge when selecting repertoire for a recital: a lack of large, important works that both fit the instrument and challenge the recitalist. This project will aim to expand recital repertoire for the viola through the development of new transcriptions, using the previously transcribed Fantasy Pieces by Schumann (trans. Leonard Davis) and Sonata No. 2 in E-flat, Op. 120 by Brahms (trans. Brahms) as an inspiration and guide. As a result, the catalogue of viola repertoire will not only be increased but the difference in tone and depth of the instrument may unveil previously unnoticed perspectives on the works. With a primary aim to expand the literature of the viola through the development of new transcriptions, this project will also strive to offer new, previously unnoticed perspectives on preexisting works. Through the changing of the instrumentation, listeners and performers will have the opportunity to explore the character of the compositions in a fresh and possibly illuminating way. Perhaps this project will encourage previously unexplored transcriptions to be realized and performed. While the recital repertoire for the viola boasts many and great works, the original transcriptions of this project attempt to infuse the collection with new and interesting possibilities for both study and performance. This dissertation project is comprised of three recitals featuring works transcribed for viola and, in most cases, newly transcribed by myself. All events took place on the campus of University of Maryland, College Park: Recital #1 on November 9, 2014 in the Gildenhorn Recital Hall of the Clarice Smith Performing Arts Center; Recital #2 on May 9, 2015, in Ulrich Recital Hall; and Recital #3 on November 6, 2015, in the Gildenhorn Recital Hall.