Staircase turret of the St. George’s cathedral in the Yuriev Monastery: archaeology, architecture and fresco painting

The article focuses on the architecture of the staircase turret of the St. George’s Cathedral in the Yuriev (St. George’s) Monastery near Novgorod and fresco wall paintings in the drum and dome at the top of the turret as well as those marked on the walls of the spiral staircase itself. This painting made in the first half of the 12th century can be interpreted in different ways: at present, experts have been associating it with the monastic use. Moreover, the room in the drum of the dome is regarded as a solitary space for monastic prayer. The analysis of the architecture of the staircase turret leads to conclusion that most of its features are related to the princely order and with the main purpose of the tower: a way to rise to the choir loft intended for the prince and his entourage. In this regard, the understanding of the nature of the painting at the top of the turret may change. The article also touches on the chronology of the construction and painting of the St. George’s Cathedral: the painting of the turret was suddenly stopped, which may be due to several events. The most probable one is the beginning of the construction of the princely St. John’s Church in Petryatin Court in 1127, where masters from the St. George’s Cathedral could be transferred to.

Structures of the human LONP1 protease reveal regulatory steps involved in protease activation

The human mitochondrial AAA+ protein LONP1 is a critical quality control protease involved in regulating diverse aspects of mitochondrial biology including proteostasis, electron transport chain activity, and mitochondrial transcription. As such, genetic or aging-associated imbalances in LONP1 activity are implicated in pathologic mitochondrial dysfunction associated with numerous human diseases. Despite this importance, the molecular basis for LONP1-dependent proteolytic activity remains poorly defined. Here, we solved cryo-electron microscopy structures of human LONP1 to reveal the underlying molecular mechanisms governing substrate proteolysis. We show that, like bacterial Lon, human LONP1 adopts both an open and closed spiral staircase orientation dictated by the presence of substrate and nucleotide. Unlike bacterial Lon, human LONP1 contains a second spiral staircase within its ATPase domain that engages substrate as it is translocated toward the proteolytic chamber. Intriguingly, and in contrast to its bacterial ortholog, substrate binding within the central ATPase channel of LONP1 alone is insufficient to induce the activated conformation of the protease domains. To successfully induce the active protease conformation in substrate-bound LONP1, substrate binding within the protease active site is necessary, which we demonstrate by adding bortezomib, a peptidomimetic active site inhibitor of LONP1. These results suggest LONP1 can decouple ATPase and protease activities depending on whether AAA+ or both AAA+ and protease domains bind substrate. Importantly, our structures provide a molecular framework to define the critical importance of LONP1 in regulating mitochondrial proteostasis in health and disease.

The Experimental Composition Improvisation Continua Model: A Tool for Musical Analysis

Among improvisers and composers today there is a resurgence of interest in experimental music (EM) practices that welcome contingency; engaging with unforeseen circumstances as an essential component of the music-making process, and a means to sonic discovery. I propose the Experimental Composition Improvisation Continua (ECIC) as a model with which to better understand these experimental musical works. The historical Experimental Music movement of the 1950s and 60s is briefly revisited, and the jazz tradition included as an essential protagonist; both being important historical movements leading to the formulation of ideas around contingent musical practices. The ECIC model is outlined as providing a means to observe the interactions and continua between composition and improvisation on the one hand and more or less experimentally conceived music on the other. This model is applied as an investigative and comparative tool to three distinctive works in order to illuminate the presence or otherwise of various experimental interactions within them. The works are: “Spiral Staircase” – a composition by written by Satoko Fujii in late 2007, John Cage’s 4′33″, and a performance of “My Favorite Things” by the John Coltrane Quartet. Further possible applications of the ECIC are suggested in the conclusion.

Structures of the Human LONP1 Protease Reveal Regulatory Steps Involved in Protease Activation

The human mitochondrial AAA+ protein LONP1 is a critical quality control protease involved in regulating diverse aspects of mitochondrial biology including proteostasis, electron transport chain activity, and mitochondrial transcription. As such, genetic or aging-associated imbalances in LONP1 activity are implicated in the pathologic mitochondrial dysfunction associated with numerous human diseases. Despite this importance, the molecular basis for LONP1-dependent proteolytic activity remains poorly defined. Here, we solved cryo-electron microscopy structures of human LONP1 to reveal the molecular mechanism of substrate proteolysis. We show that, like bacterial Lon, human LONP1 adopts both an open and closed spiral staircase orientation dictated by the presence of substrate and nucleotide. However, unlike bacterial Lon, human LONP1 contains a second spiral staircase within its ATPase domain that engages substrate to increase interactions with the translocating peptide as it transits into the proteolytic chamber for proteolysis. Further, we show that substrate-bound LONP1 includes a second level of regulation at the proteolytic active site, wherein autoinhibition of the active site is only relieved by the presence of a peptide substrate. Ultimately, our results define a structural basis for human LONP1 proteolytic activation and activity, establishing a molecular framework to understand the critical importance of this protease for mitochondrial regulation in health and disease.

Recupero architettonico e strutturale del “mastio” e del suo cortile della fortezza nuova di Volterra

Architectural and structural recovery of “mastio” and its courtyard of the new fortress of VolterraThe recovery of the “mastio” and the surrounding courtyard of the new fortress of Volterra (1472-1474) has as its objective the opening to the public of this fortified work, after 542 years from its construction, with the possibility of being enjoyed without interposing with the prison function of the complex, it also represents the possibility of knowledge and study of a constructive typology in the context of the Renaissance fortified architecture of the Italian school called “transition” with the use of the first artillery. The fortress was born as a military garrison and at the time of Lorenzo the magnificent only a part was used as a prison, it will be definitively transformed into a House of Imprisonment during the Grand Duchy of Lorraine in the middle of the eighteenth century. It is the first work by Francesco di Giovanni di Matteo called the Francione (1428-1495), it has an almost square shape with large cylindrical towers at the corners (rondelle) and at the center of the inner courtyard, a large cylindrical tower like of “mastio” (donjon) and inserted the artillery in the walls. The “mastio” consists of a basement and five floors above ground with a domed roof and connected by a narrow spiral staircase. After the cognitive essays carried out on the internal domes of the “mastio”, placed in the first three floors including the cistern, the presence of “hemispherical domes” emerged, made by workers of the Opera del Duomo in Florence, built entirely in bricks without the carpentry of “centina” (self-supporting), with the system called “alla fiorentina”, as well as the dome of Santa Maria del Fiore in Florence by Filippo Brunelleschi. This construction system is also applied in the fortified structures of Pietrasanta, Poggibonsi, Sarzanello, Castrocaro, Pisa and Terra del Sole.