Dissipative Kerr soliton microcombs for FEC-free optical communications over 100 channels.

The demand for high-speed and highly efficient optical communication techniques has been rapidly growing due to the ever-increasing volume of data traffic. As well as the digital coherent communication used for core and metro networks, intensity modulation and direct detection (IM-DD) are still promising schemes in intra/inter data centers thanks to their low latency, high reliability, and good cost performance. In this work, we study a microresonator-based frequency comb as a potential light source for future IM-DD optical systems where applications may include replacing individual stabilized lasers with a continuous laser driven microresonator. Regarding comb line powers and spectral intervals, we compare a modulation instability comb and a soliton microcomb and provide a quantitative analysis with regard to telecom applications. Our experimental demonstration achieved a forward error correction (FEC) free operation of bit-error rate (BER) <10-9 with a 1.45 Tbps capacity using a total of 145 lines over the entire C-band and revealed the possibility of soliton microcomb-based ultra-dense wavelength division multiplexing (WDM) with a simple, cost-effective IM-DD scheme, with a view to future practical use in data centers.

A protein identification method for proteomics using amino acid composition analysis with IoT-based remote control.

In the present study, we developed a protein identification method using low-cost and easy-to-operate amino acid composition analysis. The identification program automatically compares the quantitative result for each amino acid concentration obtained from the amino acid analysis to the amino acid composition data retrieved from the UniProt protein database. We found that the accuracy of protein identification using amino acid composition analysis was comparable to that of mass spectrometry analysis. The method was able to distinguish and identify differences in amino acid substitutions of several residues between proteins with high sequence homology. The identification accuracy of proteins was also improved by correcting the concentrations in the program for Cys, Trp, and Ile residues, which cannot be quantified by general sample preparation for amino acid analysis. Moreover, the amino acid analyzer was remotely controlled in accordance with the growing demand for remote work. The measured amino acid data were automatically uploaded to the IoT portal within a few minutes of each measurement, allowing researchers to download data and analyze them using the identification program anywhere and at any time by connecting to a network. The results indicated that the present method is useful for protein identification.

On-chip photon-pair generation in a silica microtoroidal cavity.

Microcavities with high Q factor and small mode volume have the potential to be efficient and compact sources of photon pairs. Here, we demonstrate on-chip photon-pair generation by spontaneous four-wave mixing in a silica microtoroidal cavity and obtain a coincidence-to-accidental ratio of 7.4 ± 0.1 with a pump power of 46 µW. The heralded photons also exhibit antibunching characterized by autocorrelation function values of gc(2)(0)=0.57±0.03<1. Comparing with a scaling model, the main noise source is found to be spontaneous Raman scattering in the cavity. This work opens a new possible means for realizing integrated nonclassical photon sources based on silica photonic circuits toward scalable quantum technologies.

Cell surface molecule, Klingon, mediates the refinement of synaptic specificity in the Drosophila visual system.

In the Drosophila brain, neurons form genetically specified synaptic connections with defined neuronal targets. It is proposed that each central nervous system neuron expresses specific cell surface proteins, which act as identification tags. Through an RNAi screen of cell surface molecules in the Drosophila visual system, we found that the cell adhesion molecule Klingon (Klg) plays an important role in repressing the ectopic formation of extended axons, preventing the formation of excessive synapses. Cell-specific manipulation of klg showed that Klg is required in both photoreceptors and the glia, suggesting that the balanced homophilic interaction between photoreceptor axons and the glia is required for normal synapse formation. Previous studies suggested that Klg binds to cDIP and our genetic analyses indicate that cDIP is required in glia for ectopic synaptic repression. These data suggest that Klg play a critical role together with cDIP in refining synaptic specificity and preventing unnecessary connections in the brain.

Role of Computational Fluid Dynamics for Predicting Delayed Cerebral Ischemia After Aneurysmal Subarachnoid Hemorrhage: Study Protocol for a Multicenter Prospective Study.

BACKGROUND: Delayed cerebral ischemia (DCI) is a significant cause of morbidity and mortality after aneurysmal subarachnoid hemorrhage (SAH). Recently, we reported the possibility that computational fluid dynamics (CFD) could predict DCI in terms of the cross-sectional area and flow velocity of the ipsilateral extracranial internal carotid and distal parent arteries in a single-center retrospective study. METHODS: This is a multicenter, prospective, cohort study. Patients with aneurysmal SAH will undergo CFD analyses using preoperative three-dimensional computed tomography angiography, and we will investigate hemodynamic features of cerebral arteries in an acute stage of SAH. Primary outcome measures will be CFD features in patients with subsequent occurrence of DCI. Secondary outcome measures will be CFD features in patients with subsequent occurrence of cerebral vasospasm and cerebral infarction and the relationships with eventual modified Rankin scale score at 3 months. CONCLUSIONS: The present protocol for a multicenter prospective study is expected to provide a novel diagnostic method to predict DCI before aneurysmal obliteration in an acute stage of SAH.

Crystal structure of the NADP+ and tartrate-bound complex of L-serine 3-dehydrogenase from the hyperthermophilic archaeon Pyrobaculum calidifontis.

A gene encoding L-serine dehydrogenase (L-SerDH) that exhibits extremely low sequence identity to the Agrobacterium tumefaciens L-SerDH was identified in the hyperthermophilic archaeon Pyrobaculum calidifontis. The predicted amino acid sequence showed 36% identity with that of Pseudomonas aeruginosa L-SerDH, suggesting that P. calidifontis L-SerDH is a novel type of L-SerDH, like Ps. aeruginosa L-SerDH. The overexpressed enzyme appears to be the most thermostable L-SerDH described to date, and no loss of activity was observed by incubation for 30 min at temperatures up to 100 °C. The enzyme showed substantial reactivity towards D-serine, in addition to L-serine. Two different crystal structures of P. calidifontis L-SerDH were determined using the Se-MAD and MR method: the structure in complex with NADP+/sulfate ion at 1.18 Å and the structure in complex with NADP+/L-tartrate (substrate analog) at 1.57 Å. The fold of the catalytic domain showed similarity with that of Ps. aeruginosa L-SerDH. However, the active site structure significantly differed between the two enzymes. Based on the structure of the tartrate, L- and D-serine and 3-hydroxypropionate molecules were modeled into the active site and the substrate binding modes were estimated. A structural comparison suggests that the wide cavity at the substrate binding site is likely responsible for the high reactivity of the enzyme toward both L- and D-serine enantiomers. This is the first description of the structure of the novel type of L-SerDH with bound NADP+ and substrate analog, and it provides new insight into the substrate binding mechanism of L-SerDH. The results obtained here may be very informative for the creation of L- or D-serine-specific SerDH by protein engineering.

Antimicrobial effects of novel peptides cOT2 and sOT2 derived from Crocodylus siamensis and Pelodiscus sinensis ovotransferrins.

In light of the increasing threat of bacterial drug resistance to human health on a global scale, research and development of antimicrobial peptides as a novel class of potent antibiotics has gained considerable attention. The present study focuses on the structural evaluation and membrane interaction of two new cationic antimicrobial peptides, cOT2 and sOT2, derived from Siamese crocodile (Crocodylus siamensis) and Chinese softshell turtle (Pelodiscus sinensis) ovotransferrins. Here, cOT1 (+3) and sOT1 (+3) were derived from reptile ovotransferrins by chromatographic purification and characterized by mass spectrometry and N-terminal sequencing analysis. In order to increase the antimicrobial efficacy, two novel peptides, cOT2 (+6) and sOT2 (+5), were designed and synthesized as "naturally-engineered" by primary amino acid sequence extension of cOT1 and sOT1, respectively. These rational designs of modified peptides were assayed in term of antimicrobial activity. These peptides display strong antimicrobial activity against several bacterial strains, e.g. Vibrio cholerae, Bacillus megaterium, and Bacillus pumilus TISTR 905, with MICs of 7-16.1µM. In terms of structural conformation in mimic environments, CD spectroscopic analysis of the secondary peptides structure features revealed fairly the similarity on α-helical content with magainin II. Hence, the modes of actions have been speculated as toroidal and carpet model. Furthermore, the disruption of intact bacterial cells induced by cOT2 and sOT2 was investigated by SEM and AFM. The results provided evidence that cOT2 and sOT2 have the potential to cause different morphological changes of bacterial cells and that these effects can be enhanced by increasing the peptide concentration.

[Pontine Hemorrhage Suspected due to Dural Arteriovenous Fistula at the Craniocervical Junction:A Case Report].

Dural arteriovenous fistulas occurring at the craniocervical junction(CCJd-AVF)are uncommon; however, they demonstrate a wide range of clinical presentations. We describe the case of a patient with pontine hemorrhage suspected due to CCJd-AVF. A 68-year-old man presented to our hospital with a sudden onset of left hemiparesis. Cranial computed tomography(CT)revealed pontine and subarachnoid hemorrhage. Magnetic resonance imaging, as well as MR, CT, and left vertebral angiograms were performed and showed a CCJd-AVF in addition to a varix coincident with the hematoma cavities. The patient was successfully treated using surgical drainer clipping. A CCJd-AVF presenting concomitantly with a pontine hemorrhage is extremely rare. Careful assessment of the anatomical relationship between the skull base and the surrounding vascular structures is important to plan neurosurgical procedures for direct interruption of the draining vein. Three-dimensional CT angiography is a useful modality that facilitates visualization of complex and anomalous anatomical structures.

A goose-type lysozyme from ostrich (Struthio camelus) egg white: multiple roles of His101 in its enzymatic reaction.

A goose-type lysozyme from ostrich egg white (OEL) was produced by Escherichia coli expression system, and the role of His101 of OEL in the enzymatic reaction was investigated by NMR spectroscopy, thermal unfolding, and theoretical modeling of the enzymatic hydrolysis of hexa-N-acetylchitohexaose, (GlcNAc)6. Although the binding of tri-N-acetylchitotriose, (GlcNAc)3, to OEL perturbed several backbone resonances in the (1)H-(15)N HSQC spectrum, the chemical shift of the backbone resonance of His101 was not significantly affected. However, apparent pKa values of His101 and Lys102 determined from the pH titration curves of the backbone chemical shifts were markedly shifted by (GlcNAc)3 binding. Thermal unfolding experiments and modeling study of (GlcNAc)6 hydrolysis using a His101-mutated OEL (H101A-OEL) revealed that the His101 mutation affected not only sugar residue affinities at subsites -3 and -2 but also the rate constant for bond cleavage. His101 appears to play multiple roles in the substrate binding and the catalytic reaction.

The structure of the proteinaceous inhibitor PliI from Aeromonas hydrophila in complex with its target lysozyme.

Recent microbiological data have revealed that Gram-negative bacteria are able to protect themselves against the lytic action of host lysozymes by secreting proteinaceous inhibitors. Four distinct classes of such inhibitors have been discovered that specifically act against c-type, g-type and i-type lysozymes. Here, the 1.24 Šresolution crystal structure of the periplasmic i-type lysozyme inhibitor from Aeromonas hydrophila (PliI-Ah) in complex with the i-type lysozyme from Meretrix lusoria is reported. The structure is the first to explain the inhibitory mechanism of the PliI family at the atomic level. A distinct `ridge' formed by three exposed PliI loops inserts into the substrate-binding groove of the lysozyme, resulting in a complementary `key-lock' interface. The interface is principally stabilized by the interactions made by the PliI-Ah residues Ser104 and Tyr107 belonging to the conserved SGxY motif, as well as by the other conserved residues Ser46 and Asp76. The functional importance of these residues is confirmed by inhibition assays with the corresponding point mutants of PliI-Ah. The accumulated structural data on lysozyme-inhibitor complexes from several classes indicate that in all cases an extensive interface of either a single or a double `key-lock' type is formed, resulting in highly efficient inhibition. These data provide a basis for the rational development of a new class of antibacterial drugs.

Asp48 function in the hydrogen-bonding network involving Asp52 of hen egg-white lysozyme.

To characterize the hydrogen-bonding network in lysozyme, we focused on the residue of Asp48 located at the active site in hen egg-white lysozyme. We constructed a mutant lysozyme (D48A) and analyzed using (GlcNAc)3 and chitin-affinity chromatography. The substrate binding of subsites D-F in D48A and the activity against (GlcNAc)5 were decreased. The parameters of substrate binding and rate constants obtained from computer simulations confirmed these changes. In the crystal structure, (GlcNAc)4 was located at the same position as wildtype. However, the side chains of Arg45 and Thr47 at subsites E-F were moved by the replacement. Further, the loss of the hydrogen bond between Asp48 and Ser50 changed the hydrogen-bonding network, and this resulted in an alteration of the side chain of Asn59. This result suggests that the hydrogen-bonding network plays a crucial in the function of Asp52 and of transglycosylation at subsites E-F.

Prediction of hematoma expansion in spontaneous intracerebral hemorrhage using a multimodal neural network.

Hematoma expansion occasionally occurs in patients with intracerebral hemorrhage (ICH), associating with poor outcome. Multimodal neural networks incorporating convolutional neural network (CNN) analysis of images and neural network analysis of tabular data are known to show promising results in prediction and classification tasks. We aimed to develop a reliable multimodal neural network model that comprehensively analyzes CT images and clinical variables to predict hematoma expansion. We retrospectively enrolled ICH patients at four hospitals between 2017 and 2021, assigning patients from three hospitals to the training and validation dataset and patients from one hospital to the test dataset. Admission CT images and clinical variables were collected. CT findings were evaluated by experts. Three types of models were developed and trained: (1) a CNN model analyzing CT images, (2) a multimodal CNN model analyzing CT images and clinical variables, and (3) a non-CNN model analyzing CT findings and clinical variables with machine learning. The models were evaluated on the test dataset, focusing first on sensitivity and second on area under the receiver operating curve (AUC). Two hundred seventy-three patients (median age, 71 years [59-79]; 159 men) in the training and validation dataset and 106 patients (median age, 70 years [62-82]; 63 men) in the test dataset were included. Sensitivity and AUC of a CNN model were 1.000 (95% confidence interval [CI] 0.768-1.000) and 0.755 (95% CI 0.704-0.807); those of a multimodal CNN model were 1.000 (95% CI 0.768-1.000) and 0.799 (95% CI 0.749-0.849); and those of a non-CNN model were 0.857 (95% CI 0.572-0.982) and 0.733 (95% CI 0.625-0.840). We developed a multimodal neural network model incorporating CNN analysis of CT images and neural network analysis of clinical variables to predict hematoma expansion in ICH. The model was externally validated and showed the best performance of all the models.

Crystal structure of binary and ternary complexes of archaeal UDP-galactose 4-epimerase-like L-threonine dehydrogenase from Thermoplasma volcanium.

A gene from the thermophilic archaeon Thermoplasma volcanium encoding an L-threonine dehydrogenase (L-ThrDH) with a predicted amino acid sequence that was remarkably similar to the sequence of UDP-galactose 4-epimerase (GalE) was overexpressed in Escherichia coli, and its product was purified and characterized. The expressed enzyme was moderately thermostable, retaining more than 90% of its activity after incubation for 10 min at up to 70 °C. The catalytic residue was assessed using site-directed mutagenesis, and Tyr(137) was found to be essential for catalysis. To clarify the structural basis of the catalytic mechanism, four different crystal structures were determined using the molecular replacement method: L-ThrDH-NAD(+), L-ThrDH in complex with NAD(+) and pyruvate, Y137F mutant in complex with NAD(+) and L-threonine, and Y137F in complex with NAD(+) and L-3-hydroxynorvaline. Each monomer consisted of a Rossmann-fold domain and a C-terminal catalytic domain, and the fold of the catalytic domain showed notable similarity to that of the GalE-like L-ThrDH from the psychrophilic bacterium Flavobacterium frigidimaris KUC-1. The substrate binding model suggests that the reaction proceeds through abstraction of the ß-hydroxyl hydrogen of L-threonine via direct proton transfer driven by Tyr(137). The factors contributing to the thermostability of T. volcanium L-ThrDH were analyzed by comparing its structure to that of F. frigidimaris L-ThrDH. This comparison showed that the presence of extensive inter- and intrasubunit ion pair networks are likely responsible for the thermostability of T. volcanium L-ThrDH. This is the first description of the molecular basis for the substrate recognition and thermostability of a GalE-like L-ThrDH.

The tertiary structure of an i-type lysozyme isolated from the common orient clam (Meretrix lusoria).

To evaluate the structure-function relationships of invertebrate lysozymes, a new invertebrate-type (i-type) lysozyme was isolated from the common orient clam (Meretrix lusoria) and the tertiary structure of this enzyme was determined. Comparison of the tertiary structure of this enzyme with those of chicken and Venerupi philippinarum lysozymes revealed that the location of the side chain of the second catalytic residue, an aspartic acid, and the N-acetylglucosamine trimer bound at subsites A-C were different. Furthermore, the amino acid electrostatically interacting with Asp30 in V. philippinarum lysozyme, Lys108, was substituted by Gly in M. lusoria lysozyme and no other possible amino acid that could contribute to this interaction was found in M. lusoria lysozyme. It therefore seems that the substitutions of the amino acids at the interface of the V. philippinarum lysozyme dimer are likely to change the oligomeric state of the M. lusoria lysozyme.

Crystallization and preliminary X-ray analysis of L-serine 3-dehydrogenase complexed with NADP+ from the hyperthermophilic archaeon Pyrobaculum calidifontis.

An NAD(P)(+)-dependent L-serine 3-dehydrogenase from the hyperthermophilic archaeon Pyrobaculum calidifontis was crystallized using the sitting-drop vapour-diffusion method with ammonium sulfate as the precipitant. The crystals belonged to the monoclinic space group C2, with unit-cell parameters a = 120.81, b = 57.40, c = 56.37 Å, ß = 106.88°. Diffraction data were collected to 1.57 Å resolution on beamline NE3A at the Photon Factory. The overall R(merge) was 4.2% and the data completeness was 90.1%.

The mutational effect of Ile58 at subsite C in hen egg-white lysozyme on substrate binding, enzymatic activity, and protein stability.

Ile58 of hen egg-white lysozyme (HEL) is buried in the interior of the molecule and is considered to participate in sugar residue binding at subsite C through hydrophobic interaction. The contribution of Ile58 to lysozyme function and stability was investigated by replacement of Ile58 with less hydrophobic residues, Val (I58V) and Ala (I58A). Replacement of Ile58 with Ala decreased substrate binding ability to an N-acetylglucosamine trisaccharide, (GlcNAc)3, and a GlcNAc polymer, chitin, whereas replacement with Val had little effect. Similar results were obtained as to enzymatic activity toward both the bacterial cell substrate and glycol chitin. Kinetic analysis by substrate (GlcNAc)5 revealed that replacement of the Ile residue reduced the sugar residue affinity at subsite C and the rate constant of glycosidic bond cleavage. The rate constant of glycosidic cleavage for mutant I58A was about one-third of that for the wild-type. Guanidine hydrochloride unfolding experiments showed that mutants I58V and I58A were less stable than the wild-type, by 1.88 and 2.88 kcal/mol respectively. Moreover, the stability of the protein inserted at this position decreased linearly with decreasing hydrophobicity of the inserted residue. It appears that the hydrophobicity of Ile58 is an important factor in the efficient substrate binding, enzymatic reaction, and structural stability of HEL.

The complete amino acid sequence and enzymatic properties of an i-type lysozyme isolated from the common orient clam (Meretrix lusoria).

To determine the structure and functional relationships of invertebrate lysozymes, we isolated a new invertebrate (i)-type lysozyme from the common orient clam (Meretrix lusoria) and determined the complete amino acid sequence of two isozymes that differed by one amino acid. The determined sequence showed 65% similarity to a lysozyme from Venerupis philippinarum (Tapes japonica), and it was therefore classified as an i-type lysozyme. The lytic activities of this lysozyme were similar to those of previously reported bivalve i-type lysozymes, but unlike the V. philippinarum lysozyme, it did not exhibit an increase in activity in high ionic strength. Our data suggest that this lysozyme does not have a dimeric structure, due to the replacement of Lys108 which contributes to dimer formation in the V. philippinarum lysozyme. GlcNAc oligomer activities suggested an absence of transglycosylation activity and a higher number of subsites on this enzyme compared with hen egg lysozyme.

Expression, purification, crystallization and preliminary X-ray analysis of NAD(P)H-dependent carbonyl reductase specifically expressed in thyroidectomized chicken fatty liver.

An NAD(P)H-dependent carbonyl reductase specifically expressed in thyroidectomized chicken fatty liver was crystallized using the sitting-drop vapour-diffusion method with polyethylene glycol 300 as the precipitant. The crystals belonged to the monoclinic space group C2, with unit-cell parameters a=104.26, b=81.32, c=77.27 Å, ß=119.43°, and diffracted to 1.86 Šresolution on beamline NE3A at the Photon Factory. The overall Rmerge was 5.4% and the data completeness was 99.4%.

Amino acid sequence of Egyptian goose egg-white lysozyme and effects of amino acid substitution on the enzymatic activity.

The amino acid sequence of Egyptian goose lysozyme (EGL) from egg-white and its enzymatic properties were analyzed. The established sequence had the highest similarity to wood duck lysozyme (WDL) with five amino acid substitutions, and had eighteen substitutions difference from hen egg-white lysozyme (HEL). Tyr34 and Gly37 were found at subsites E and F of the active site when compared with HEL. The experimental time-course characteristics of EGL against the N-acetylglucosamine pentamer substrate, (GlcNAc)(5), revealed higher production of (GlcNAc)(4) and lower production of (GlcNAc)(2) when compared with HEL. The saccharide-binding ability of subsites A-C in EGL was also found to be weaker than in HEL. An analysis of the enzymatic reactions of five mutants in respect of positions 34, 37 and 71 in HEL indicated the time-course characteristics of EGL to be caused by the combination of three substitutions (F34Y, N37G and G71R) between HEL and EGL. A computer simulation of the EGL-catalyzed reaction suggested that the time-course characteristics of EGL resulted from the difference in the binding free energy for subsites A, B, E and F and the rate constant of transglycosylation between EGL and HEL.

Novel Transdural Epiarachnoid Approach for Large Central Disk Herniation in Upper Lumbar Spine.

BACKGROUND AND IMPORTANCE: The treatment for large central disk herniation (LCDH) at upper lumbar spine is often challenging. Previous reports showed various surgical strategies, such as microdiscectomy with posterior fixation, endoscopic surgery, and microdiscectomy through transdural approach. However, there is no consensus regarding which surgical option is better for LCDH at upper lumbar spine. In this report, we describe the novel transdural epiarachnoid approach (TDEA), which uses the corridor of epiarachnoid space for microdiscectomy. Compared with classical transdural approaches, this novel approach may reduce risks of postoperative cerebrospinal fluid leakage and the development of arachnoiditis. CLINICAL PRESENTATION: A 69-yr-old man presented with progressive bilateral radiating leg pain, intermittent claudication, and low back pain. Magnetic resonance images and computed tomography scans revealed LCDH at L2/3 level. We performed microdiscectomy using the TDEA. Postoperative course was uneventful, and his symptoms were relieved after surgery. CONCLUSION: The novel TDEA for LCDH at upper lumbar spine is illustrated with a video. This novel approach has an advantage of the preservation of subarachnoid components compared with classical transdural approaches.