Primary Candida guilliermondii Infection of the Knee in a Patient without Predisposing Factors

Isolated primary candidal infection of joint is extremely rare, with only a few reported cases. It occurs as a result of accidental implantations of fungus during traumatic procedures, such as surgery, and is usually reported in patients with predisposing factors such as immunosuppression, malignancy, and drug abuse. If left untreated, irreversible deformity and pain with severe osteoarticular destruction occur. Thus, early diagnosis and treatment are important. This paper presents a case of 72-year-old man with primary C. guilliermondii infection of knee joint without predisposing factors and previous traumatic procedures, who was misdiagnosed with advanced degenerative osteoarthritis. Our case is the second case of primary C. guilliermondii arthritis of knee to be reported in the English-language literature and the first to be successfully treated with total knee arthroplasty following IV amphotericin B and oral fluconazole. Primary candidal infection of joint is generally asymptomatic or involves only mild pain and swelling in the affected knee. Thus, although the majority of knee joint infections are of a pyogenic or tuberculous origin, if a patient complains of mild pain and swelling in the knee and has mild signs of infection, the possibility of fungal infection should be considered

Crystal Structure of Dps-1, a Functionally Distinct Dps Protein from Deinococcus radiodurans

DNA protection during starvation (Dps) proteins play an important role in protecting cellular macromolecules from damage by reactive oxygen species (ROS). Unlike most orthologs that protect DNA by a combination of DNA binding and prevention of hydroxyl radical formation by ferroxidation and sequestration of iron, Dps-1 from the radiation-resistant Deinococcus radiodurans fails to protect DNA from hydroxyl radical-mediated cleavage through a mechanism inferred to involve continuous release of iron from the protein core. To address the structural basis for this unusual release of Fe2+, the crystal structure of D. radiodurans Dps-1 was determined to 2.0 Å resolution. Two of four strong anomalous signals per protein subunit correspond to metal-binding sites within an iron-uptake channel and a ferroxidase site, common features related to the canonical functions of Dps homologs. Similar to Lactobacillus lactis Dps, a metal-binding site is found at the N-terminal region. Unlike other metal sites, this site is located at the base of an N-terminal coil on the outer surface of the dodecameric protein sphere and does not involve symmetric association of protein subunits. Intriguingly, a unique channel-like structure is seen featuring a fourth metal coordination site that results from 3-fold symmetrical association of protein subunits through α2 helices. The presence of this metal-binding site suggests that it may define an iron-exit channel responsible for the continuous release of iron from the protein core. This interpretation is supported by substitution of residues involved in this ion coordination and the observation that the resultant mutant protein exhibits significantly attenuated iron release. Therefore, we propose that D. radiodurans Dps-1 has a distinct iron-exit channel. © 2006 Elsevier Ltd. All rights reserved

Molecular basis of the fructose-2,6-bisphosphatase reaction of PFKFB3: Transition state and the C-terminal function

The molecular basis of fructose-2,6-bisphosphatase (F-2,6-P 2ase) of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFKFB) was investigated using the crystal structures of the human inducible form (PFKFB3) in a phospho-enzyme intermediate state (PFKFB3-P•F-6-P), in a transition state-analogous complex (PFKFB3•AlF 4), and in a complex with pyrophosphate (PFKFB3•PP i) at resolutions of 2.45, 2.2, and 2.3 Å, respectively. Trapping the PFKFB3-P•F-6-P intermediate was achieved by flash cooling the crystal during the reaction, and the PFKFB3•AlF 4 and PFKFB3•PP i complexes were obtained by soaking. The PFKFB3•AlF 4 and PFKFB3•PP i complexes resulted in removing F-6-P from the catalytic pocket. With these structures, the structures of the Michaelis complex and the transition state were extrapolated. For both the PFKFB3-P formation and break down, the phosphoryl donor and the acceptor are located within ∼5.1 Å, and the pivotal point 2-P is on the same line, suggesting an in-line transfer with a direct inversion of phosphate configuration. The geometry suggests that NE2 of His253 undergoes a nucleophilic attack to form a covalent N-P bond, breaking the 2O-P bond in the substrate. The resulting high reactivity of the leaving group, 2O of F-6-P, is neutralized by a proton donated by Glu322. Negative charges on the equatorial oxygen of the transient bipyramidal phosphorane formed during the transfer are stabilized by Arg252, His387, and Asn259. The C-terminal domain (residues 440-446) was rearranged in PFKFB3•PP i, implying that this domain plays a critical role in binding of substrate to and release of product from the F-2,6-P 2ase catalytic pocket. These findings provide a new insight into the understanding of the phosphoryl transfer reaction. © 2011 Wiley Periodicals, Inc

A Direct Substrate-Substrate Interaction Found in the Kinase Domain of the Bifunctional Enzyme, 6-Phosphofructo-2-kinase/Fructose-2,6-bisphosphatase

To understand the molecular basis of a phosphoryl transfer reaction catalyzed by the 6-phosphofructo-2-kinase domain of the hypoxia-inducible bifunctional enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFKFB3), the crystal structures of PFKFB3{radical dot}AMPPCP{radical dot}fructose-6-phosphate and PFKFB3{radical dot}ADP{radical dot}phosphoenolpyruvate complexes were determined to 2.7 Å and 2.25 Å resolution, respectively. Kinetic studies on the wild-type and site-directed mutant proteins were carried out to confirm the structural observations. The experimentally varied liganding states in the active pocket cause no significant conformational changes. In the pseudo-substrate complex, a strong direct interaction between AMPPCP and fructose-6-phosphate (Fru-6-P) is found. By virtue of this direct substrate-substrate interaction, Fru-6-P is aligned with AMPPCP in an orientation and proximity most suitable for a direct transfer of the γ-phosphate moiety to 2-OH of Fru-6-P. The three key atoms involved in the phosphoryl transfer, the β,γ-phosphate bridge oxygen atom, the γ-phosphorus atom, and the 2-OH group are positioned in a single line, suggesting a direct phosphoryl transfer without formation of a phosphoenzyme intermediate. In addition, the distance between 2-OH and γ-phosphorus allows the γ-phosphate oxygen atoms to serve as a general base catalyst to induce an associative phosphoryl transfer mechanism. The site-directed mutant study and inhibition kinetics suggest that this reaction will be catalyzed most efficiently by the protein when the substrates bind to the active pocket in an ordered manner in which ATP binds first. © 2007 Elsevier Ltd. All rights reserved

Crystal structure of the hypoxia-inducible form of 6-phosphofructo-2- kinase/fructose-2,6-bisphosphatase (PFKFB3): A possible new target for cancer therapy

The hypoxia-inducible form of 6-phosphofructo-2-kinase/fructose-2,6- bisphosphatase (PFKFB3) plays a crucial role in the progression of cancerous cells by enabling their glycolytic pathways even under severe hypoxic conditions. To understand its structural architecture and to provide a molecular scaffold for the design of new cancer therapeutics, the crystal structure of the human form was determined. The structure at 2.1 Å resolution shows that the overall folding and functional dimerization are very similar to those of the liver (PFKFB1) and testis (PFKFB4) forms, as expected from sequence homology. However, in this structure, the N-terminal regulatory domain is revealed for the first time among the PFKFB isoforms. With a β-hairpin structure, the N terminus interacts with the 2-Pase domain to secure binding of fructose-6-phosphate to the active pocket, slowing down the release of fructose-6-phosphate from the phosphoenzyme intermediate product complex. The C-terminal regulatory domain is mostly disordered, leaving the active pocket of the fructose-2,6-bisphosphatase domain wide open. The active pocket of the 6-phosphofructo-2-kinase domain has a more rigid conformation, allowing independent bindings of substrates, fructose-6-phosphate and ATP, with higher affinities than other isoforms. Intriguingly, the structure shows an EDTA molecule bound to the fructose-6-phosphate site of the 6-phosphofructo-2-kinase active pocket despite its unfavorable liganding concentration, suggesting a high affinity. EDTA is not removable from the site with fructose-6-P alone but is with both ATP and fructose-6-P or with fructose-2,6-bisphosphate. This finding suggests that a molecule in which EDTA is covalently linked to ADP is a good starting molecule for the development of new cancer-therapeutic molecules. © 2006 by The American Society for Biochemistry and Molecular Biology, Inc

Suppression of magnetic ordering in XXZ-type antiferromagnetic monolayer NiPS3

How a certain ground state of complex physical systems emerges, especially in two-dimensional materials, is a fundamental question in condensed-matter physics. A particularly interesting case is systems belonging to the class of XY Hamiltonian where the magnetic order parameter of conventional nature is unstable in two-dimensional materials leading to a Berezinskii-Kosterlitz-Thouless transition. Here, we report how the XXZ-type antiferromagnetic order of a magnetic van der Waals material, NiPS3, behaves upon reducing the thickness and ultimately becomes unstable in the monolayer limit. Our experimental data are consistent with the findings based on renormalization group theory that at low temperatures a two-dimensional XXZ system behaves like a two-dimensional XY one, which cannot have a long-range order at finite temperatures. This work provides experimental examination of the XY magnetism in the atomically thin limit and opens new opportunities of exploiting these fundamental theorems of magnetism using magnetic van der Waals materials.Comment: 57 pages, 24 figures (including Supplementary Information

High-Performance Flexible Organic Light-Emitting Diodes Using Amorphous Indium Zinc Oxide Anode

We demonstrate a high-performance flexible organic light-emitting diode (OLED) employing amorphous indium zinc oxide (IZO) anode. The amorphous IZO on flexible polycarbonate (PC) substrate shows similar electrical conductivity and optical transmittance with commercial (ITO) glass, even though it was prepared at <50°C. Moreover, it exhibits little resistance change during 5000 bending cycles, demonstrating good mechanical robustness. A green phosphorescent OLED fabricated on amorphous IZO on flexible PC shows maximum external quantum efficiency of ext=13.7% and power efficiency of p=32.7 lm/W, which are higher than a device fabricated on a commercial ITO on glass (ext=12.4% and p=30.1 lm/W) and ITO on flexible PC (ext=8.5% and p =14.1 lm/W). The mechanical robustness and low-temperature deposition of IZO combined with high OLED performance clearly manifest that the amorphous IZO is a promising anode material for flexible displays.This work was supported by the Ministry of Commerce, Industry, and Energy through the OLED center and Samsung SDI. H.K.K. thanks the Korea Research Foundation (contract no. KRF-2006-331- D00243) for its support

IR-QNN Framework: An IR Drop-Aware Offline Training Of Quantized Crossbar Arrays

Resistive Crossbar Arrays present an elegant implementation solution for Deep Neural Networks acceleration. The Matrix-Vector Multiplication, which is the corner-stone of DNNs, is carried out in O(1) compared to O(N-2) steps for digital realizations of O(log(2)(N)) steps for in-memory associative processors. However, the IR drop problem, caused by the inevitable interconnect wire resistance in RCAs remains a daunting challenge. In this article, we propose a fast and efficient training and validation framework to incorporate the wire resistance in Quantized DNNs, without the need for computationally extensive SPICE simulations during the training process. A fabricated four-bit Au/Al2O3/HfO2/TiN device is modelled and used within the framework with two-mapping schemes to realize the quantized weights. Efficient system-level IR-drop estimation methods are used to accelerate training. SPICE validation results show the effectiveness of the proposed method to capture the IR drop problem achieving the baseline accuracy with a 2% and 4% drop in the worst-case scenario for MNIST dataset on multilayer perceptron network and CIFAR 10 dataset on modified VGG and AlexNet networks, respectively. Other nonidealities, such as stuck-at fault defects, variability, and aging, are studied. Finally, the design considerations of the neuronal and the driver circuits are discussed