Kankoku tsūran.

Cover title.

Kinsei meika ibun shūran

Mounted cover title: Ibun shūran.

Hao ran tang shi ji : 6 juan /

Caption title.

Ran hou zhi zhai da wen : 20 juan.

Double leaves, oriental style, in case.

Zōho gagen shūran /

On double leaves, oriental style.

Chōsen kinseki sōran,

Mode of access: Internet.

A disappearing act performed by magnesium: the nucleotide exchange mechanism of Ran GTPase by Quantum mechanics/Molecular mechanics studies

The Ran GTPase protein is a guanine nucleotide-binding protein (GNBP) with an acknowledged profile in cancer onset, progression and metastases. The complex mechanism adopted by GNBPs in exchanging GDP for GTP is an intriguing process and crucial for Ran viability. The successful completion of the process is a fundamental aspect of propagating downstream signalling events. QM/MM molecular dynamics simulations were employed in this study to provide a deeper mechanistic understanding of the initiation of nucleotide exchange in Ran. Results indicate significant disruption of the metal-binding site upon interaction with RCC1 (the Ran guanine nucleotide exchange factor), overall culminating in the prominent shift of the divalent magnesium ion. The observed ion drifting is reasoned to occur as a consequence of the complex formation between Ran and RCC1 and is postulated to be a critical factor in the exchange process adopted by Ran. This is the first report to observe and detail such intricate dynamics for a protein in Ras superfamily.

Post-translational lysine-acetylation of Ran and its regulation by Sirtuin deacetylases

Through recent advances in high-throughput mass spectrometry it has become evident that post-translational N-(epsilon)-lysine-acetylation is a modification found on thousands of proteins of all cellular compartments and all essential physiological processes. Many aspects in the biology of lysine-acetylation are poorly understood, including its regulation by lysine-acetyltransferases and lysine-deacetylases (KDACs). Here, the role of this modification was investigated for the small GTP-binding protein Ran, which, inter alia, is essential for the regulation of nucleocytoplasmic transport. To this end, site-specifically acetylated Ran was produced in E. coli by genetic code expansion. For five previously identified sites, Ran acetylation was tested regarding its impact on the intrinsic GTP hydrolysis rate, the assembly of export complexes (modeled in vitro with the export receptor CRM1 and the export substrate Spn1) and the interaction of Ran with its GTPase activation protein RanGAP and RanBP1. Overall, mild effects of Ran acetylation were observed for intrinsic and RanGAP-stimulated GTP hydrolysis rates. The interaction of active Ran with RanBP1 was negatively influenced by Ran acetylation at K159. Moreover, CRM1 bound to Ran acetylated at K37, K99 or K159 interacted more strongly with Spn1. Thus, lysine-acetylation interferes with essential aspects of Ran function. An in vitro screen was performed to identify potential Ran KDACs. The NAD+-dependent KDACs of the Sirtuin class showed activity towards two acetylation sites of Ran, K37 and K71. The specificity of Sirtuins was further analyzed based on an additional Ran acetylation site, K38. Since deacetylation of RanAcK38 was much slower compared to RanAcK37, di-acetylated RanAcK37/38 was tested next. The deacetylation rate of di-acetylated Ran was comparable to that of RanAcK37. Deacetylation experiments under single turnover conditions revealed that deacetylation occurs first at the K38 site in the di-acetylated RanAcK37/38 background. The ability of Sirtuins to deacetylate two adjacent AcKs was further investigated based on two proteins, which had previously been found to be di-acetylated and targeted by Sirtuins, namely the tumor suppressor protein p53 and phosphoenolpyruvate carboxykinase 1 (PEPCK1). p53 was readily deacetylated at two di-acetylation sites (K372/372 and K381/382), whereas PEPCK1 was not deacetylated in vitro. Taken together, these results have important implications for the substrate specificity of Sirtuins.

Enabling 5G and beyond: millimeter wave propagation and cloud RAN evolution

In the last few years, mobile wireless technology has gone through a revolutionary change. Web-enabled devices have evolved into essential tools for communication, information, and entertainment. The fifth generation (5G) of mobile communication networks is envisioned to be a key enabler of the next upcoming wireless revolution. Millimeter wave (mmWave) spectrum and the evolution of Cloud Radio Access Networks (C-RANs) are two of the main technological innovations of 5G wireless systems and beyond. Because of the current spectrum-shortage condition, mmWaves have been proposed for the next generation systems, providing larger bandwidths and higher data rates. Consequently, new radio channel models are being developed. Recently, deterministic ray-based models such as Ray-Tracing (RT) are getting more attractive thanks to their frequency-agility and reliable predictions. A modern RT software has been calibrated and used to analyze the mmWave channel. Knowledge of the electromagnetic properties of materials is therefore essential. Hence, an item-level electromagnetic characterization of common construction materials has been successfully achieved to obtain information about their complex relative permittivity. A complete tuning of the RT tool has been performed against indoor and outdoor measurement campaigns at 27 and 38 GHz, setting the basis for the future development of advanced beamforming techniques which rely on deterministic propagation models (as RT). C-RAN is a novel mobile network architecture which can address a number of challenges that network operators are facing in order to meet the continuous customers’ demands. C-RANs have already been adopted in advanced 4G deployments; however, there are still some issues to deal with, especially considering the bandwidth requirements set by the forthcoming 5G systems. Open RAN specifications have been proposed to overcome the new 5G challenges set on C-RAN architectures, including synchronization aspects. In this work it is described an FPGA implementation of the Synchronization Plane for an O-RAN-compliant radio system.

Interference mitigation techniques for cloud-RAN deployments in 5G and beyond systems

The deployment of ultra-dense networks is one of the most promising solutions to manage the phenomenon of co-channel interference that affects the latest wireless communication systems, especially in hotspots. To meet the requirements of the use-cases and the immense amount of traffic generated in these scenarios, 5G ultra-dense networks are being deployed using various technologies, such as distributed antenna system (DAS) and cloud-radio access network (C-RAN). Through these centralized densification schemes, virtualized baseband processing units coordinate the distributed access points and manage the available network resources. In particular, link adaptation techniques are shown to be fundamental to overall system operation and performance enhancement. The core of this dissertation is the result of an analysis and a comparison of dynamic and adaptive methods for modulation and coding scheme (MCS) selection applied to the latest mobile telecommunications standards. A novel algorithm based on the proportional-integral-derivative (PID) controller principles and block error rate (BLER) target has been proposed. Tests were conducted in a 4G and 5G system level laboratory and, by means of a channel emulator, the performance was evaluated for different channel models and target BLERs. Furthermore, due to the intrinsic sectorization of the end-users distribution in the investigated scenario, a preliminary analysis on the joint application of users grouping algorithms with multi-antenna and multi-user techniques has been performed. In conclusion, the importance and impact of other fundamental physical layer operations, such as channel estimation and power control, on the overall end-to-end system behavior and performance were highlighted.