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Exploiting multiple near-field optical eigenmodes is an effective means of designing, engineering, and extending the functionalities of optical devices. However, the near-field optical eigenmodes of subwavelength plasmonic nanostructures are often highly multiplexed in both spectral and spatial distributions, making it extremely difficult to extract individual eigenmodes. We propose a novel mode analysis method that can resolve individual eigenmodes of subwavelength nanostructures, which are superimposed in conventional methods. A transmission matrix is constructed for each excitation wavelength by obtaining the near-field distributions for various incident angles, and through singular value decomposition, near-field profiles and energy spectra of individual eigenmodes are effectively resolved. By applying transmission matrix analysis to conventional electromagnetic simulations, we clearly resolved a set of orthogonal eigenmodes of single- and double-slot nanoantennas with a slot width of 20 nm. In addition, transmission matrix analysis leads to solutions that can selectively excite specific eigenmodes of nanostructures, allowing selective use of individual eigenmodes.

The eukaryotic genome is prone to a high amount of DNA damage from intrinsic and extrinsic sources, causing transcriptional stress, including pausing, backtracking and stalling. If not rectified in time, these damages can further lead to transcriptional arrest and genome instability. Here, we develop a single-molecule FRET based elongation complex which allows us to insert various types of DNA damage into the transcribed region and study the effect they have on the dynamics of RNAPII transcription. We show that different DNA lesions cause a heterogenous effect on RNAPII. In some instances, such as oxidative lesions, RNAPII exhibits a high level of dynamic behaviour often backtracking up to 10 nt. While other damages, such as cyclo-butane pyrimidine dimers and abasic sites, can cause more significant static stalling. Furthermore, the repair factor Rad26 binds to RNAPII and alters these dynamics by pushing RNAPII further over the damage site and preventing long-range backtracking events.

Vibrational sum-frequency generation (VSFG) spectroscopy, a surface-specific technique, was shown to be useful even for characterizing the vibrational optical activity of chiral molecules in isotropic bulk liquids. However, accurately determining the spectroscopic parameters is still challenging because of the spectral congestion of chiroptical VSFG peaks with different amplitudes and phases. Here, we show that a time-variable infrared-visible chiroptical three-wave-mixing technique can be used to determine the spectroscopic parameters of second-order vibrational response signals from chiral chemical liquids. For varying the delay time between infrared and temporally asymmetric visible laser pulses, we measure the chiral VSFG, achiral VSFG, and their interference spectra of bulk R-(+)-limonene liquid and perform a global fitting analysis for those time-variable spectra to determine their spectroscopic parameters accurately. We anticipate that this time-variable VSFG approach will be useful for developing nearly background-free chiroptical characterization techniques with enhanced spectral resolution.

This study presents a compact rectifier array with an adaptive power distribution network (APDN). The rectifier array comprises rectifier cell 1 for both high-power mode and high-frequency band; rectifier cell 2 for both low-power mode and low-frequency band; and a power distribution network, which adaptively distributes power according to the input power and frequency. The proposed APDN is merged with input matching networks of the subrectifiers to achieve low insertion loss and high compactness with wideband characteristics. For validation, the proposed rectifier array was designed, implemented, and measured. The measurement results show that the power conversion efficiency (PCE) is over 50% within an input power range of 9.9–30.8 dBm. A peak PCE of over 50% is realized at a frequency range of 0.1–2.7 GHz.

The COVID-19 pandemic is the third outbreak this century of a zoonotic disease caused by a coronavirus, following the emergence of severe acute respiratory syndrome (SARS) in 20031 and Middle East respiratory syndrome (MERS) in 20122. Treatment options for coronaviruses are limited. Here we show that clofazimine-an anti-leprosy drug with a favourable safety profile3-possesses inhibitory activity against several coronaviruses, and can antagonize the replication of SARS-CoV-2 and MERS-CoV in a range of in vitro systems. We found that this molecule, which has been approved by the US Food and Drug Administration, inhibits cell fusion mediated by the viral spike glycoprotein, as well as activity of the viral helicase. Prophylactic or therapeutic administration of clofazimine in a hamster model of SARS-CoV-2 pathogenesis led to reduced viral loads in the lung and viral shedding in faeces, and also alleviated the inflammation associated with viral infection. Combinations of clofazimine and remdesivir exhibited antiviral synergy in vitro and in vivo, and restricted viral shedding from the upper respiratory tract. Clofazimine, which is orally bioavailable and comparatively cheap to manufacture, is an attractive clinical candidate for the treatment of outpatients and-when combined with remdesivir-in therapy for hospitalized patients with COVID-19, particularly in contexts in which costs are an important factor or specialized medical facilities are limited. Our data provide evidence that clofazimine may have a role in the control of the current pandemic of COVID-19 and-possibly more importantly-in dealing with coronavirus diseases that may emerge in the future.

While loss-of-function mutations in Cockayne syndrome group B protein (CSB) cause neurological diseases, this unique member of the SWI2/SNF2 family of chromatin remodelers has been broadly implicated in transcription elongation and transcription-coupled DNA damage repair, yet its mechanism remains largely elusive. Here, we use a reconstituted in vitro transcription system with purified polymerase II (Pol II) and Rad26, a yeast ortholog of CSB, to study the role of CSB in transcription elongation through nucleosome barriers. We show that CSB forms a stable complex with Pol II and acts as an ATP-dependent processivity factor that helps Pol II across a nucleosome barrier. This noncanonical mechanism is distinct from the canonical modes of chromatin remodelers that directly engage and remodel nucleosomes or transcription elongation factors that facilitate Pol II nucleosome bypass without hydrolyzing ATP. We propose a model where CSB facilitates gene expression by helping Pol II bypass chromatin obstacles while maintaining their structures.

Oxidation of guanine generates several types of DNA lesions, such as 8-oxoguanine (8OG), 5-guanidinohydantoin (Gh), and spiroiminodihydantoin (Sp). These guanine-derived oxidative DNA lesions interfere with both replication and transcription. However, the molecular mechanism of transcription processing of Gh and Sp remains unknown. In this study, by combining biochemical and structural analysis, we revealed distinct transcriptional processing of these chemically related oxidized lesions: 8OG allows both error-free and error-prone bypass, whereas Gh or Sp causes strong stalling and only allows slow error-prone incorporation of purines. Our structural studies provide snapshots of how polymerase II (Pol II) is stalled by a nonbulky Gh lesion in a stepwise manner, including the initial lesion encounter, ATP binding, ATP incorporation, jammed translocation, and arrested states. We show that while Gh can form hydrogen bonds with adenosine monophosphate (AMP) during incorporation, this base pair hydrogen bonding is not sufficient to hold an ATP substrate in the addition site and is not stable during Pol II translocation after the chemistry step. Intriguingly, we reveal a unique structural reconfiguration of the Gh lesion in which the hydantoin ring rotates ∼90° and is perpendicular to the upstream base pair planes. The perpendicular hydantoin ring of Gh is stabilized by noncanonical lone pair–π and CH–π interactions, as well as hydrogen bonds. As a result, the Gh lesion, as a functional mimic of a 1,2-intrastrand crosslink, occupies canonical −1 and +1 template positions and compromises the loading of the downstream template base. Furthermore, we suggest Gh and Sp lesions are potential targets of transcription-coupled repair.

In this Letter, the authors present a reconfigurable power divider using a hybrid matrix with variable impedance tuners. The proposed hybrid matrix-based power divider with varactor-tuned impedance tuners (VTITs) can simultaneously obtain variable power-dividing ratios at the centre frequency and variable operating frequencies for the 3 dB coupling states. The VTITs, consisting of a transmission line, an inductor, and a varactor located between the line and the inductor, are connected in parallel between two hybrid couplers for high impedance variation. Measured results demonstrate that the power-dividing ratio of the proposed divider varies from -14.3 to 13.3 dB with a return loss above 20 dB and the isolation above 20 dB at a centre frequency of 2.45 GHz. Moreover, it achieves an insertion loss of 0.7-1.45 dB and a phase variation of less than 8° across the variable power-dividing ratio at the centre frequency. The frequency-tuning range for the 3 dB coupling states is 750 MHz with a small phase variation of 5°.

Despite significant advances in all aspects of single particle cryo-electron microscopy (cryo-EM), specimen preparation still remains a challenge. During sample preparation, macromolecules interact with the air-water interface, which often leads to detrimental effects such as denaturation or adoption of preferred orientations, ultimately hindering structure determination. Randomly biotinylating the protein of interest (for example, at its primary amines) and then tethering it to a cryo-EM grid coated with two-dimensional crystals of streptavidin (acting as an affinity surface) can prevent the protein from interacting with the air-water interface. Recently, this approach was successfully used to solve a high-resolution structure of a test sample, a bacterial ribosome. However, whether this method can be used for samples where interaction with the air-water interface has been shown to be problematic remains to be determined. Here we report a 3.1 A structure of an RNA polymerase II elongation complex stalled at a cyclobutane pyrimidine dimer lesion (Pol II EC(CPD)) solved using streptavidin grids. Our previous attempt to solve this structure using conventional sample preparation methods resulted in a poor quality cryo-EM map due to Pol II EC(CPD)’s adopting a strong preferred orientation. Imaging the same sample on streptavidin grids improved the angular distribution of its view, resulting in a high-resolution structure. This work shows that streptavidin affinity grids can be used to address known challenges posed by the interaction with the air-water interface.

Transcription, catalyzed by RNA polymerase II (Pol II) in eukaryotes, is the first step in gene expression. RNA Pol II is a 12-subunit enzyme complex regulated by many different transcription factors during transcription initiation, elongation, and termination. During elongation, Pol II encounters various types of obstacles that can cause transcriptional pausing and arrest. Through decades of research on transcriptional pausing, it is widely known that Pol II can distinguish between different types of obstacles by its active site. A major class of obstacles is DNA lesions. While some DNA lesions can cause transient transcriptional pausing, which can be bypassed by Pol II itself or with the help from other elongation factors, bulky DNA damage can cause prolonged transcriptional pausing and arrest, which signals for transcription coupled repair. Using biochemical and structural biology approaches, the outcomes of many different types of DNA lesions, DNA modifications, and DNA binding molecules to transcription were studied. In this mini review, we will describe the in vitro transcription assays with Pol II to investigate the impacts of various DNA lesions on transcriptional outcomes and the crystallization method of lesion-arrested Pol II complex. These methods can provide a general platform for the structural and biochemical analysis of Pol II transcriptional pausing and bypass mechanisms.

Live cell imaging provides essential information in the investigation of cell biology and related pathophysiology. Refractive index (RI) can serve as intrinsic optical imaging contrast for 3-D label-free and quantitative live cell imaging, and provide invaluable information to understand various dynamics of cells and tissues for the study of numerous fields. Recently significant advances have been made in imaging methods and analysis approaches utilizing RI, which are now being transferred to biological and medical research fields, providing novel approaches to investigate the pathophysiology of cells. To provide insight into how RI can be used as an imaging contrast for imaging of biological specimens, here we provide the basic principle of RI-based imaging techniques and summarize recent progress on applications, ranging from microbiology, hematology, infectious diseases, hematology, and histopathology.

Transcription elongation by RNA polymerase II (Pol II) is constantly challenged by numerous types of obstacles that lead to transcriptional pausing or stalling. These obstacles include DNA lesions, DNA epigenetic modifications, DNA binding proteins, and non-B form DNA structures. In particular, lesion-induced prolonged transcriptional blockage or stalling leads to genome instability, cellular dysfunction, and cell death. Transcription-coupled nucleotide excision repair (TC-NER) pathway is the first line of defense that detects and repairs these transcription-blocking DNA lesions. In this review, we will first summarize the recent research progress toward understanding the molecular basis of transcriptional pausing and stalling by different kinds of obstacles. We will then discuss new insights into Pol II-mediated lesion recognition and the roles of CSB in TC-NER.

Humans have lost the ability to convert urate into the more soluble allantoin with the evolutionary inactivation of three enzymes of the uricolytic pathway. Restoration of this function through enzyme replacement therapy can treat severe hyperuricemia and Lesch-Nyhan disease. Through a genomic exploration of natural gene fusions, we found that plants and diatoms independently evolved a fusion protein (allantoin synthase) complementing two human pseudogenes. The 1.85-Å-resolution crystal structure of allantoin synthase from the diatom Phaeodactylum tricornutum provides a rationale for the domain combinations observed in the metabolic pathway, suggesting that quaternary structure is key to the evolutionary success of protein domain fusions. Polyethylene glycol (PEG) conjugation experiments indicate that a PEG-modified form of the natural fusion protein provides advantages over separate enzymes in terms of activity maintenance and manufacturing of the bioconjugate. These results suggest that the combination of different activities in a single molecular unit can simplify the production and chemical modification of recombinant proteins for multifunctional enzyme therapy.

The fungal pathogen Cryptococcus neoformans is a causative agent of meningoencephalitis in humans. For its pathogenicity, the inositol polyphosphate biosynthetic pathway plays critical roles. Recently, Ipk1 from C. neoformans (CnIpk1) was identified as an inositol 1,3,4,5,6-pentakisphosphate 2-kinase that catalyzes the phosphorylation of IP5 to form IP6, a substrate for subsequent reaction to produce inositol pyrophosphates, such as PP-IP5/IP7. Furthermore, it was shown that deletion of IPK1 significantly reduces the virulence of C. neoformans, indicating that Ipk1 is a major virulence contributor. In this study, we determined a crystal structure of the apo-form of CnIpk1 at 2.35A resolution, the first structure for a fungal Ipk1, using a single-wavelength anomalous dispersion method. Even with a low sequence similarity of 26-28%, its overall structure resembles two other Ipk1 orthologs from Arabidopsis thaliana (AtIpk1) and Mus musculus (MmIpk1), and the most crucial residues in the active site are conserved. Unlike AtIpk1 and MmIpk1, however, metal-binding sites for structural stabilization and conformational variations are absent in CnIpk1. The binding environments for substrate IP5 could be inferred by the two different binding sites for sulfate ion in CnIpk1. Taken together, these observations suggest structural similarities and discrepancies for fungal Ipk1 among members of the Ipk1 family and provide structural information for the possible development of drug design for treatment of cryptococcosis.

In Burkholderia species, the production of oxalate, an acidic molecule, is a key event for bacterial growth in the stationary phase. Oxalate plays a central role in maintaining environmental pH, which counteracts inevitable population-collapsing alkaline toxicity in amino acid-based culture medium. In the phytopathogen Burkholderia glumae, two enzymes are responsible for oxalate production. First, the enzyme oxalate biosynthetic component A (ObcA) catalyzes the formation of a tetrahedral C6-CoA adduct from the substrates acetyl-CoA and oxaloacetate. Then the ObcB enzyme liberates three products from the C6-CoA adduct: oxalate, acetoacetate, and CoA. Interestingly, these two stepwise reactions are catalyzed by a single bifunctional enzyme, Obc1, from Burkholderia thailandensis and Burkholderia pseudomallei. Obc1 has an ObcA-like N-terminal domain and shows ObcB activity in its C-terminal domain despite no sequence homology with ObcB. We report the crystal structure of Obc1 in its apo and glycerol-bound form at 2.5 Å and 2.8 Å resolution, respectively. The Obc1 N-terminal domain is essentially identical both in structure and function to that of ObcA. Its C-terminal domain has an α/β hydrolase fold that has a catalytic triad for oxalate production and a novel oxyanion hole distinct from the canonical HGGG motif in other α/β hydrolases. Functional analyses through mutagenesis studies suggested that His-934 is an additional catalytic acid/base for its lyase activity and liberates two additional products, acetoacetate and CoA. These results provide structural and functional insights into bacterial oxalogenesis and an example of divergent evolution of the α/β hydrolase fold, which has both hydrolase and lyase activity.

RNA polymerase II (Pol II) has an intrinsic fidelity control mechanism to maintain faithful genetic information transfer during transcription. 8-Oxo-guanine (8OG), a commonly occurring damaged guanine base, promotes misincorporation of adenine into the RNA strand. Recent structural work has shown that adenine can pair with the syn conformation of 8OG directly upstream of the Pol II active site. However, it remains unknown how 8OG is accommodated in the active site as a template base for the incoming ATP. Here, we used molecular dynamics (MD) simulations to investigate two consecutive steps that may contribute to the adenine misincorporation by Pol II. First, the mismatch is located in the active site, contributing to initial incorporation of adenine. Second, the mismatch is in the adjacent upstream position, contributing to extension from the mismatched bp. These results are supported by an in vitro transcription assay, confirming that 8OG can induce adenine misincorporation. Our simulations further suggest that 8OG forms a stable bp with the mismatched adenine in both the active site and the adjacent upstream position. This stability predominantly originates from hydrogen bonding between the mismatched adenine and 8OG in a noncanonical syn conformation. Interestingly, we also found that an unstable bp present directly upstream of the active site, such as adenine paired with 8OG in the canonical anti conformation, largely disrupts the stability of the active site. Our findings have uncovered two main factors contributing to how 8OG induces transcriptional errors and escapes Pol II transcriptional fidelity control checkpoints.

Nitrogen remobilization is a key issue in plants. Recent studies in Arabidopsis thaliana have revealed that nucleoside catabolism supplies xanthine, a nitrogen-rich compound, to the purine ring catabolic pathway, which liberates ammonia from xanthine for reassimilation into amino acids. Similarly, pyrimidine nuclosides are degraded and the pyrimidine bases are fully catabolized. During nucleoside hydrolysis, ribose is released, and ATP-dependent ribokinase (RBSK) phosphorylates ribose to ribose-5'-phosphate to allow its entry into central metabolism recycling the sugar carbons from nucleosides. In this study, we report the crystal structure of RBSK from Arapidopsis thaliana (AtRBSK) in three different ligation states: an unliganded state, a ternary complex with ribose and ATP, and a binary complex with ATP in the presence of Mg2+. In the monomeric conformation, AtRBSK is highly homologous to bacterial RBSKs, including the binding sites for a monovalent cation, ribose, and ATP. Its dimeric conformation, however, does not exhibit the noticeable ligand-induced changes that were observed in bacterial orthologs. Only in the presence of Mg2+, ATP in the binary complex adopts a catalytically competent conformation, providing a mode of action for Mg2+ in AtRBSK activity. The structural data combined with activity analyses of mutants allowed assignment of functional roles for the active site residues. Overall, this study provides the first structural characterization of plant RBSK, and experimentally validates a previous hypothetical model concerning the general reaction mechanism of RBSK.

A 79-GHz adaptive-gain and low-noise ultra-wideband radar receiver RF front-end integrated circuit in 65-nm CMOS is presented in this paper. The receiver consists of an adaptive-gain low-noise amplifier (AGLNA) and a ${ g}_{ m}$ -boosted sub-harmonic mixer (SHM). The proposed AGLNA controls the gain with adaptive biased circuits, which lowers the gain as the received signal power increases to provide wide dynamic range to the radar receiver without any external controls. We analyzed the input impedance of a cascode amplifier with a parallel resonant inductor, which improves the noise figure. The proposed ${ g}_{ m}$ -boosted SHM uses a transformer-based feedback network with NMOS bleeding circuits to provide a high conversion gain. The SHM was designed to use a differential local oscillator (LO) signal to have a simple structure and operate at low LO power. The measured conversion gain range was from 16 to $-{\hbox{7.5 dB}}$ with a received power range from $-{\hbox{45}}$ to $-{\hbox{5 dBm}}$ at 79.5 GHz. The measured noise figure was 10.5 dB and the measured 2LO-to-RF isolation was 70 dB. The chip area is ${\hbox{0.47}}\times {\hbox{1.23}}~{\hbox{mm}}^{2}$ .

This paper presents a fully integrated W-band 4-GHz bandwidth (BW) pseudo-noise (PN)-coded pulse compression radar transmitter (TX) in a CMOS technology. The PN-coded pulse compression scheme is adopted to obtain high spectral density and to lower the TX leakage using a 63-bit PN code generator based on linear feedback shift registers. We propose a sub-harmonic pumped pulse former and a pulsed power amplifier for high TX efficiency with the suppression of local oscillator (LO)/2LO leakage. A frequency synthesizer including a frequency divider chain generates a sub-harmonic LO signal, as well as a 5-GHz digital clock. Digital blocks with the PN-code generator are synchronized with the clock signal, which makes all pulses start with the same phase. The proposed TX achieves 14.5-dBm maximum output power with the tuning range of 75–81.5 GHz, and the phase noise is ${-}{\hbox{95.2}}$ dBc/Hz at a 1-MHz offset in the range of LO frequencies. In pulse mode, it generates a 4-GHz BW RF pulse signal, which corresponds to a range resolution of 7.5 cm, and the average dc power dissipation is 160 mW.

A miniaturized continuous-wave Doppler radar sensor operating at 915 MHz to remotely detect both respiration and heart rate (beats per minute) is presented. The proposed radar sensor comprises a front-end module including an implemented complementary metal-oxide semiconductor low-noise amplifier (LNA) and fractal-slot patch antennas, whose area was reduced by 15.2%. The two-stage inverter-based LNA was designed with an interstage capacitor and a feedback resistor to acquire ultrawide bandwidth. Two operating frequencies, 915 MHz and 2.45 GHz, were analyzed with regard to path loss for efficient operation because frequency affects detection sensitivity, reflected signal power from the human body, and measurement distance in a far-field condition. Path-loss calculation based on the simplified layer model indicates that the reflected power of the 915 MHz radar could be higher than that of the 2.45 GHz radar. The implemented radar front-end module excluding the LNA occupies 35 &times, 55 mm2. Vital signs were obtained via a fast Fourier transform and digital filtering using raw signals. In an experiment with six subjects, the respiration and heart rate obtained at 0.8 m using the proposed radar sensor exhibited mean accuracies of 99.4% and 97.6% with respect to commercialized reference sensors, respectively.

A W-band 2.5 GHz bandwidth pulse generator comprising a voltage-controlled oscillator (VCO) and a novel pulse former in a 65 nm CMOS technology is presented. The proposed sub-harmonic pumped pulse former, which plays roles as both a frequency doubler and a pulse former, is designed to obtain high efficiency using a transformer-based current reuse circuit. The VCO is implemented with a parallel combining transformer, which makes it insensitive to load variations due to pulse formation. Measurements show that the pulse generator achieves −1 dBm peak output power at 79 GHz. It can generate 800 ps pulse signals with an RF carrier of 76.1–79.6 GHz, achieving the energy cost rate of 50 pJ/pulse with a 1.25 GHz pulse repetition period.

A W-band differential frequency doubler using a current-reuse configuration in a 65 nm CMOS process is presented in this letter. The differential current-reuse circuit with a second harmonic coupling transformer is introduced to improve conversion gain at small input powers minimizing the effect of the RF bypass capacitor. The proposed circuit achieves a conversion gain of $0.8\sim -4.2~{\rm dB}$ and a fundamental rejection above 19 dB in the input frequency range of 36.5~44 GHz with $-4 ~{\rm dBm}$ input power. It has conversion gain variation below 1 dB when the input power varies from $-7.4$ to 0.1 dBm at 77 GHz. The dc power consumption is 14 mW. It has the highest conversion gain with the smallest chip size of 0.22 ${\rm mm}^{2}$ among all V-/W-band CMOS frequency doublers.

This paper presents a 77-GHz CMOS power amplifier (PA) with a parallel power combiner based on a transmission-line transformer (TLT). An inter-stage matched cascode power cell structure is applied to obtain high output power and efficiency, where a simple matching network between the common-gate and common-source stage is introduced. The parallel power combiner based on a broadside-coupled TLT is analyzed and compared with a series power combiner. The PA is fabricated using a 65-nm RF CMOS process. It achieves the saturated output power of 15.8 dBm, the power-added efficiency of 15.2%, and the power gain of 20.9 dB with a supply voltage of 2.0 V at 77 GHz.

We present a new approach to three-dimensional (3D) temperature distribution imaging using optical diffraction tomography (ODT). We reconstruct the 3D temperature distribution near gold nanorods under an illumination at their plasmonic resonance wavelength.

The 26 GHz and 79 GHz UWB frequency bands are used for short-range radar applications for automobile. In this paper, single chip front-end ICs for both frequency bands are presented. The pulsed oscillator at 26 GHz can produce UWB short pulses. It consumes power only during short duty cycles; thus, it allows a power-efficient radar. A stereo radar, which comprises two synchronized radars, is demonstrated with the ICs. Hybrid beam forming techniques based on base-band delay are also demonstrated. The pulsed front-end architecture of the proposed 79 GHz UWB pulse radar is discussed, which is expected to reduce power consumption. The performance of some circuit elements is also reported.

In this paper, a 79 GHz g m -boosted sub-harmonic mixer with high conversion gain is presented. As a g m -boosting technique, a transformer based feedback network with an NMOS bleeding path is proposed to achieve high conversion gain. The differential LO-driven sub-harmonic mixer has a simple structure and operates at low LO power. The measurement results show a conversion gain of 1.6 dB at a LO power of −5 dBm, a noise figure of 13 dB, and a 2LO-to-RF isolation of 38 dB. The power consumption of the sub-harmonic mixer is 12 mW. The circuit was fabricated using 65-nm CMOS technology with a chip area of 0.69×0.45 mm2.

The Burkholderia species utilize acetyl-CoA and oxaloacetate, substrates for citrate synthase in the TCA cycle, to produce oxalic acid in response to bacterial cell to cell communication, called quorum sensing. Quorum sensing-mediated oxalogenesis via a sequential reaction by ObcA and ObcB counteracts the population-collapsing alkaline pH of the stationary growth phase. Thus, the oxalic acid produced plays an essential role as an excreted public good for survival of the group. Here, we report structural and functional analyses of ObcA, revealing mechanistic features distinct from those of citrate synthase. ObcA exhibits a unique fold, in which a (β/α)8-barrel fold is located in the C-domain with the N-domain inserted into a loop following α1 in the barrel fold. Structural analyses of the complexes with oxaloacetate and with a bisubstrate adduct indicate that each of the oxaloacetate and acetyl-CoA substrates is bound to an independent site near the metal coordination shell in the barrel fold. In catalysis, oxaloacetate serves as a nucleophile by forming an enolate intermediate mediated by Tyr322 as a general base, which then attacks the thioester carbonyl carbon of acetyl-CoA to yield a tetrahedral adduct between the two substrates. Therefore, ObcA catalyzes its reaction by combining the enolase and acetyltransferase superfamilies, but the presence of the metal coordination shell and the absence of general acid(s) produces an unusual tetrahedral CoA adduct as a stable product. These results provide the structural basis for understanding the first step in oxalogenesis and constitute an example of the functional diversity of an enzyme for survival and adaptation in the environment. Background: Oxalogenesis in the Burkholderia species is an indispensable event for their survival in the stationary phase. Results: Structural and functional analyses of ObcA, the first enzyme in oxalogenesis, unravel an unprecedented reaction mechanism. Conclusion: ObcA produces a tetrahedral CoA adduct. Significance: This study provides a structural basis for understanding the first step in oxalogenesis.

The Burkholderia species utilize acetyl-CoA and oxaloacetate, substrates for citrate synthase in the TCA cycle, to produce oxalic acid in response to bacterial cell to cell communication, called quorum sensing. Quorum sensing-mediated oxalogenesis via a sequential reaction by ObcA and ObcB counteracts the population-collapsing alkaline pH of the stationary growth phase. Thus, the oxalic acid produced plays an essential role as an excreted public good for survival of the group. Here, we report structural and functional analyses of ObcA, revealing mechanistic features distinct from those of citrate synthase. ObcA exhibits a unique fold, in which a (β/α)8-barrel fold is located in the C-domain with the N-domain inserted into a loop following α1 in the barrel fold. Structural analyses of the complexes with oxaloacetate and with a bisubstrate adduct indicate that each of the oxaloacetate and acetyl-CoA substrates is bound to an independent site near the metal coordination shell in the barrel fold. In catalysis, oxaloacetate serves as a nucleophile by forming an enolate intermediate mediated by Tyr322 as a general base, which then attacks the thioester carbonyl carbon of acetyl-CoA to yield a tetrahedral adduct between the two substrates. Therefore, ObcA catalyzes its reaction by combining the enolase and acetyltransferase superfamilies, but the presence of the metal coordination shell and the absence of general acid(s) produces an unusual tetrahedral CoA adduct as a stable product. These results provide the structural basis for understanding the first step in oxalogenesis and constitute an example of the functional diversity of an enzyme for survival and adaptation in the environment. Background: Oxalogenesis in the Burkholderia species is an indispensable event for their survival in the stationary phase. Results: Structural and functional analyses of ObcA, the first enzyme in oxalogenesis, unravel an unprecedented reaction mechanism. Conclusion: ObcA produces a tetrahedral CoA adduct. Significance: This study provides a structural basis for understanding the first step in oxalogenesis.

A 77 GHz CMOS medium power amplifier (PA) with high efficient matching networks based on transformer is presented. The unit transistor size of a power cell is selected by analyzing its maximum available gain. The broadside-coupled Transmission-Line Transformers (TLTs) are implemented as matching networks for low insertion loss and wide band matching characteristics. The PA is fabricated using a 65-nm RF CMOS process. The saturated output power and the peak power-added efficiency at 76.5GHz is 12.8 dBm and 8%, respectively. The DC power consumption is 236 mW with a supply voltage of 2.0V.