A New 3-Ketosteroid-Δ1–Dehydrogenase with High Activity and Broad Substrate Scope for Efficient Transformation of Hydrocortisone at High Substrate Concentration

3-Ketosteroid-Δ¹-dehydrogenases (KstDs [EC 1.3.99.4]) catalyze the Δ¹-dehydrogenation of steroids and are a class of important enzymes for steroid biotransformations. In this study, nine putative kstD genes from different origins were selected and overexpressed in Escherichia coli BL21(DE3). These recombinant enzymes catalyzed the Δ¹-desaturation of a variety of steroidal compounds. Among them, the KstD from Propionibacterium sp. (PrKstD) displayed the highest specific activity and broad substrate spectrum. The detailed catalytic characterization of PrKstD showed that it can convert a wide range of 3-ketosteroid compounds with diverse substituents, ranging from substituents at the C9, C10, C11 and C17 position through substrates without C4-C5 double bond, to previously inactive C6-substituted ones such as 11β,17-dihydroxy-6α-methyl-pregn-4-ene-3,20-dione. Reaction conditions were optimized for the biotransformation of hydrocortisone in terms of pH, temperature, co-solvent and electron acceptor. By using 50 g/L wet resting E. coli cells harboring PrKstD enzyme, the conversion of hydrocortisone was about 92.5% within 6 h at the substrate concentration of 80 g/L, much higher than the previously reported results, demonstrating the application potential of this new KstD.

Directed evolution of an alcohol dehydrogenase for the desymmetric reduction of 2,2-disubstituted cyclopenta-1,3-diones by enzymatic hydrogen transfer

Directed evolution of carbonyl reductase TbADH created mutant Tb2 with balanced activity toward ethyl secodione and isopropanol, enabling the desymmetric reduction of ethyl secodione to give (13R,17S)-ethyl secol with 94% yield, >99% ee and >99% de.

[Catalytic mechanism, molecular engineering and applications of threonine aldolases]

Threonine aldolases catalyze the aldol condensation of aldehydes with glycine to furnish β-hydroxy-α-amino acid with two stereogenic centers in a single reaction. This is one of the most promising green methods for the synthesis of optically pure β-hydroxy-α-amino acid with high atomic economy and less negative environmental impact. Several threonine aldolases from different origins have been identified and characterized. The insufficient -carbon stereoselectivity and the challenges of balancing kinetic versus thermodynamic control to achieve the optimal optical purity and yield hampered the application of threonine aldolases. This review summarizes the recent advances in discovery, catalytic mechanism, high-throughput screening, molecular engineering and applications of threonine aldolases, with the aim to provide some insights for further research in this field.

Engineering a carbonyl reductase for the scalable preparation of (S)-3-Cyclopentyl-3-hydroxypropanenitrile, the key building block of ruxolitinib

( S )- 3-Cyclopentyl-3-hydroxypropanenitrile is the key precursor for the synthesis of ruxolitinib. The bioreduction of 3-cyclopentyl-3-ketopropanenitrile ( 1a ) offers an attractive method to access this important compound. A carbonyl reductase (PhADH) from Paraburkholderia hospita catalyzed the reduction of 1a giving the ( S )-alcohol ( 1b ) with 85% ee. Rational engineering of PhADH resulted in a double mutant H93C/A139L, which enhanced the enantioselectivity from 85% to >98%, as well as a 6.3-fold improvement in the specific activity. The bioreduction of 1a was performed at 200 g/L (1.5 M) substrate concentration, leading to isolation of ( S )- 1b in 91% yield. Similarly, using this mutant enzyme 3-cyclohexyl-3-ketopropanenitrile ( 2a) and 3-phenyl-3-ketopropanenitrile ( 3a ) were reduced at high concentration affording the corresponding alcohols in >99% ee, and 90% and 92% yield, respectively. The results showed that the variant H93C/A139L was a powerful biocatalyst for reduction of β-substituted-β-ketonitriles.

[Efficacy and safety of conformal thermocoagulation guided by stereotactic electroencephalogram in the treatment of epilepsy caused by focal cortical dysplasia in eloquent cortex]

Objective: To explore the efficacy and safety of stereotactic electroencephalography (SEEG)-guided conformal radiofrequency thermocoagulation for epilepsy caused by focal cortical dysplasia (FCD) in eloquent cortex. Methods: The data of epilepsy patients with conformal thermocoagulation in the Epilepsy Center of Guangdong Sanjiu Brain Hospital from September 2017 to August 2020 were retrospectively analyzed. SEEG electrodes were placed in patients with drug-refractory epilepsy caused by FCD in eloquent cortex with limited boundaries, which was confirmed by preoperative evaluation methods such as imaging and electroencephalography. When designing the electrode placement plan, related software was used to reconstruct the three-dimensional MRI image and lesion. SEEG electrode contacts should be designed to fully cover the lesion as much as possible. After the completion of SEEG monitoring and cortical electrical stimulation, the pre-thermocoagulation and permanent thermocoagulation modes were used in sequence. The mode of direct damage between adjacent contacts of a single electrode and cross-destruction between adjacent contacts of multiple electrodes was combined to ablate the lesions point by point. Results: A total of 22 patients were enrolled, ranging from 2 to 30 years old, with an average age of (15±9) years old. MRI showed that FCD lesions located at pre-central gyrus in 19 cases, at post-central gyrus in 3 cases, at left frontal lobe in 3 cases, at both pre-central and post-central gyrus in 1 case and at both pre-central and left frontal lobe in 2 cases. The length of the lesion was 1.2-4.0 cm, with an average length of (2.2±0.7) cm. Moreover, 7-12 SEEG electrodes were implanted, with an average of (9±2) electrodes. The number of electrodes passing through the lesion was 2-8, with an average of 5±2. The number of thermocoagulation target points was 6 to 83, with an average of 29±18, while the number of target points which proved to have function by cortical simulation was 0-21, with a median of 3.5. The number of direct thermocoagulation target points was 6 to 58, with an average of 23±13, while the number of cross thermocoagulation target points was 0 to 30, with a median of 3. The completion of the whole thermocoagulation was divided into 2 to 5 times. There were 11 cases (50%) who experienced immediate muscle strength decline, 1 case (4.5%) showed slower speech speed during thermocoagulation, 3 cases (13.6%) exhibited muscle strength decline after thermocoagulation, however, only 1 case (4.5%) had permanent hemiparalysis. There were 17 cases of Engel Ⅰ (77.3%), 3 cases of Engel Ⅱ (13.6%), and 2 case of Engel Ⅲ (9.1%), respectively, after follow-up for 6-42 months, with an average of (20±10) months. Conclusion: SEEG-guided conformal radiofrequency thermocoagulation is safe and effective for epilepsy caused by FCD in eloquent cortex with limited boundaries.

Targeting STING attenuates ROS induced intervertebral disc degeneration

OBJECTIVE

DNA damage induced by ROS is considered one of the main causes of nucleus pulposus (NP) cells degeneration during the progression of intervertebral disc degeneration (IVDD). cGAS-STING pathway acts as DNA-sensing mechanism for monitoring DNA damage. Recent studies have proved that cGAS-STING contributes to the development of various diseases by inducing inflammation, senescence, and apoptosis. This work explored the role of STING, the main effector of cGAS-STING signaling pathway, in NP degeneration.

METHOD

Immunohistochemistry was conducted to measure STING protein levels in the nucleus pulposus tissues from human and puncture-induced IVDD rat models. TBHP induces degeneration of nucleus pulposus cells in vitro. For in vivo experiments, lv-NC or lv-STING were injected into the central intervertebral disc space. The degeneration level of IVDD was assessed by MRI, X-ray, HE, and Safranin O staining.

RESULTS

We found that the expression of STING was upregulated in human and rat degenerated NP tissue as well as in TBHP-treated NP cells. Overexpression of STING promoted the degradation of extracellular matrix; it also promoted apoptosis and senescence of TBHP-treated and untreated NP cells. Knock-down of STING significantly reversed these effects. Mechanistically, STING activated IRF3, whereas blockage of IRF3 attenuated STING-induced apoptosis, senescence and ECM degradation. In vivo experiments revealed that STING knock-down alleviated puncture-induced IVDD development.

CONCLUSION

STING promotes IVDD progress via IRF3, while suppression of STING may be a promising treatment for IVDD.

[Chromosomal karyotypes and C-band analysis of Triatoma rubrofasciata in China]

OBJECTIVE

To investigate the karyotypes and C bands of Triatoma rubrofasciata in China, so as to understand its chromosome number, morphology and C-band staining of T. rubrofasciata.

METHODS

The testis specimens were sampled from male T. rubrofasciata collected from Shunde City, Guangdong Province, prepared into slides of metaphase chromosomes and subjected to Giemsa staining and C-band staining. The morphology of metaphase chromosomes and the location of heterochromatin were observed using microscopy, and the long arm and short arm of each chromosome and total chromosome length were recorded to analyze the karyotypes and C bands of T. rubrofasciata.

RESULTS

The male T. rubrofasciata presented a chromosome number of 2n = 25, including 22 autosomes and 3 sex chromosomes. The relative length of chromosomes ranged from 3.59% to 12.76%, the arm ratio was 1.06 to 1.24, and the centromere index was 44.76% to 48.47%. All chromosomes were metacentric chromosomes and the karyotype formula was 2n = 22 metacentric + X₁X₂Y, and the C bands varied on different chromosomes. No heterochromatin was found in the X chromosome, and the overall staining appeared pale, while heterochromatin was detected in all regions of the Y chromosome, and the overall staining appeared dark. In addition, heterochromatin was present in both ends of the autosome.

CONCLUSIONS

The male T. rubrofasciata presents a chromosome number of 2n = 25 in China, and the karyotype formula is 2n = 22 metacentric + X₁X₂Y. C-banding shows dark staining of the Y chromosome, pale staining of the X chromosome, and dark staining of both ends of the autosome. Our data may provide insights into the investigation on the origin, evolution and gene mapping of T. rubrofasciata in China.

ORAI3 contributes to hypoxia-inducible factor 1/2α-sensitive colon cell migration

BACKGROUND

Hypoxia is a pivotal initiator of tumor angiogenesis and growth through the stabilization of hypoxia-inducible factors (HIFs). This study set out to examine the involvement of HIF-1α and HIF-2α in colon cancer and ascertained whether ORAI3 was involved in the pathway.

MATERIALS AND METHODS

Patients and murine models as well as human colorectal adenocarcinoma tumor (CW2) cells were included to examine the levels of ORAI1/3 and HIF-1/2α levels. Calcium imaging was utilized to ascertain the activity of calcium channel. Scratch assay was used to assess the migration capacity of the cells.

RESULTS

Tumors from murine colon cancer xenograft models and patients with colon cancer displayed high ORAI1/3 and HIF-1/2α levels. Hypoxia treatment, mimicking the tumor microenvironment in vitro, increased ORAI1/3 and HIF-1/2α expression as well as store-operated Ca2+ entry (SOCE). Of note is that HIF-1/2α silencing decreased SOCE, and HIF-1/2α overexpression facilitated SOCE. Furthermore, ORAI3 rather than ORAI1 expression was inhibited by HIF-1/2α silencing while increased by ML228. Luciferase assay also confirmed that ORAI3 was elevated in the presence of ML228, indicating the linkage between HIF-1/2α and ORAI3. Additionally, colony-forming potential and cell migration capacity were decreased in siHIF-1α and siHIF-2α as well as siORAI3 cells, and the facilitating effect of ML228 on cell migration and colony-forming potential was also decreased in siORAI3 CW-2 cells, which points out the importance of ORAI3 in HIF1/2α pathway.

CONCLUSION

Our findings allow to conclude that both HIF-1α and HIF-2α facilitate ORAI3 expression, hence enhancing colon cancer progression.

Modulating the active site lid of an alcohol dehydrogenase from Ralstonia sp. enabled efficient stereospecific synthesis of 17β-hydroxysteroids

Enzymatic stereospecific reduction of 17-oxosteroids offers an attractive approach to access 17β-hydroxysteroids of pharmaceutical importance. In this study, by adjusting the flexibility of α6-helix at the substrate entrance of the alcohol dehydrogenase from Ralstonia sp. (RasADH), the catalytic activity toward the stereospecific 17β-reduction of androstenedione was improved without sacrifice of the enantioselectivity. Among the mutants, F205I and F205A exhibited up to 623- and 523-fold improvement in catalytic efficiency, respectively, towards a range of different 17-oxosteroids compared to the wild-type enzyme. The corresponding 17β-hydroxysteroids were prepared in optically pure form with high space-time productivity and isolated yields using F205I as the biocatalyst, indicating that these mutants are promising biocatalysts for this useful transformation. These results suggest that modulating the flexibility of the active site lid offers an effective approach to engineer alcohol dehydrogenase for accommodating bulky steroidal substrates.

POS0228 BASELINE CHARACTERISTICS AND TREATMENT RESPONSE TO IXEKIZUMAB CATEGORISED BY SEX IN RADIOGRAPHIC AND NON-RADIOGRAPHIC AXIAL SPONDYLARTHRITIS PATIENTS THROUGH 52 WEEKS: DATA FROM 3 PHASE III, RANDOMIZED, CONTROLLED TRIALS

Background:

Axial spondyloarthritis (axSpA) is a chronic inflammatory disease of the axial skeleton comprising two subtypes within the same spectrum: radiographic (r-axSpA) and non-radiographic (nr-axSpA). Previous studies have shown that clinical presentation and treatment response of males and females may differ1 despite similar disease burden.2 Ixekizumab (IXE), a high-affinity monoclonal antibody that selectively targets interleukin-17A, has demonstrated superior efficacy to placebo in the treatment of patients with r-axSpA (COAST-V/W [bDMARD- naïve/TNFi-experienced]) and nr-axSpA (COAST-X [bDMARD-naïve]).3

Objectives:

Assess baseline characteristics and treatment response to IXE categorised by sex in patients with r-axSpA and nr-axSpA for up to 52 weeks.

Methods:

Patients fulfilled the ASAS classification criteria for r-axSpA or nr-axSpA. Patients were randomized to receive 80 mg subcutaneous IXE every 2 weeks (Q2W) or 4 weeks (Q4W), or to placebo (PBO) [16 weeks COAST-V/W; 52 weeks COAST-X]. Baseline characteristics and treatment outcomes were assessed. Patients were categorised by sex, missing data was controlled for using non-responder imputation (NRI) and modified baseline observation carried forward (mBOCF) analysis was conducted on continuous efficacy variables.

Results:

At baseline, females were older, with significantly higher pain and fatigue scores and peripheral joint symptoms (table 1). ASAS40 response rate with IXEQ4W was achieved in 39% of males with r-axSpA by week 16, and 44% by week 52. Females achieved 16.7% at week 16, and 33.3% at week 52. In nr-axSpA, 46% of IXEQ4W males achieved ASAS40 at week 16 and 30% at week 52. 23.9% of females achieved ASAS40 at week 16, increasing to 30.4% at week 52.

Table 1.

Baseline Characteristics of Patients Categorised by Sex

Patients with r-axSpA(COAST-V/W)(n=376)Patients with nr-axSpA(COAST-X)(n=198)CharacteristicMale (n=298)Female (n=78)p valueMale (n=99)Female (n=99)p valueAge at onset (yrs), mean (SD)26.5 (8.7)30.1 (10.1)0.002*27.9 (7.7)32.0 (10.7)0.002*Symptom duration (yrs), mean (SD)16.7 (10.5)17.8 (12.2)0.4209.5 (9.2)12.3 (11.3)0.057ASDAS, mean (SD)4.0 (0.8)3.9 (0.7)0.3043.7 (0.8)3.9 (0.8)0.143BASDAI, mean (SD)7.10 (1.4)7.4 (1.5)0.1796.9 (1.4)7.4 1.4)0.013*Fatigue/tiredness (BASDAI Q1), mean (SD)7.4 (1.6)7.8 (1.5)0.036*7.0 (1.6)7.9 (1.5)<0.001*Spinal pain (BASDAI Q2), mean (SD)7.9 (1.5)8.0 (1.5)0.6827.5 (1.4)7.9 (1.5)0.029*Pain/swelling in other joints (BASDAI Q3), mean (SD)6.5 (2.1)6.9 (2.2)0.1296.6 (2.3)7.2 (1.9)0.039*Tenderness to touch/pressure (BASDAI Q4), mean (SD)6.8 (1.8)7.0 (1.9)0.3396.6 (1.9)6.8 (1.8)0.404Morning stiffness (BASDAI Q5), mean (SD)7.5 (1.6)7.7 (1.8)0.5047.3 (1.7)7.7 (1.9)0.137Morning stiffness duration (BASDAI Q6), mean (SD)6.5 (2.3)6.5 (2.8)0.9446.3 (2.3)6.6 (2.5)0.392Spinal pain at night NRS, mean (SD)7.4 (1.5)7.8 (1.7)0.033*7.0 (1.8)7.6 (1.8)0.027*BASFI, mean (SD)6.8 (1.8)7.0 (2.0)0.4666.2 (1.8)6.7 (2.1)0.108SF-36 PCS, mean (SD)30.9 (8.3)28.9 (8.2)0.07533.1 (7.7)32.1 (7.2)0.348

p-value from Fisher’s exact test analysis of variance (ANOVA) with sex as a factor for continuous data. Data includes pooled IXEQ2W and IXEQ4W.

Conclusion:

This analysis demonstrates that for the axSpA disease spectrum, females present with higher disease burden as reflected by higher scores in fatigue/tiredness, and spinal pain at night. Our findings indicate that males and females respond to IXE; however, females experience this benefit later in their treatment course, with a more prolonged attainment of peak response.

References:

[1]van der Horst-Bruinsma IE, et al. Ann Rheum Dis. 2019;78:1550-1558.

[2]Zhao SS, et al. Rheumatology. 2019;58:2025-2030.

[3]Deodhar A, et al. Lancet. 2020;395:53-64.

Figure 1.

COAST-V/W ASAS40 (ITT, NRI) Patients initially randomized to PBO in COAST-V/W switched to IXEQ2W or Q4W at week 16 by study design; PBO data are summarised up to week 16.

Acknowledgements:

Writing support was provided by Dr Geraldine Fahy, an employee of Eli Lilly and Company

Disclosure of Interests:

Irene van der Horst-Bruinsma Speakers bureau: BMS, AbbVie, Pfizer, UCB, MSD, Consultant of: Abbvie, UCB, MSD, Lilly, Novartis, Grant/research support from: MSD, Pfizer, AbbVie, Rebecca Bolce Shareholder of: Eli Lilly, Employee of: Eli Lilly, Theresa Hunter Shareholder of: Eli Lilly, Employee of: Eli Lilly, David Sandoval Shareholder of: Eli Lilly, Employee of: Eli Lilly, Danting Zhu Employee of: Eli Lilly, Vladimir J. Geneus Employee of: Eli Lilly, Jeffrey Lisse Shareholder of: Eli Lilly, Employee of: Eli Lilly, Soyi Liu Leage Shareholder of: Eli Lilly, Employee of: Eli Lilly, Marina Magrey Consultant of: Novartis, Eli Lilly, Pfizer, Abbvie, UCB and Jansen, Grant/research support from: Amgen, AbbVie, and UCB Pharma

Crystal Structures and Catalytic Mechanism of l-erythro-3,5-Diaminohexanoate Dehydrogenase and Rational Engineering for Asymmetric Synthesis of β-Amino Acids

Amino acid dehydrogenases (AADHs) have shown considerable potential as biocatalysts in the asymmetric synthesis of chiral amino acids. However, compared to the widely studied α-AADHs, limited knowledge is available about β-AADHs that enable the synthesis of β-amino acids. Herein, we report the crystal structures of a l-erythro-3,5-diaminohexanoate dehydrogenase and its variants, the only known member of β-AADH family. Crystal structure analysis, site-directed mutagenesis studies and quantum chemical calculations revealed the differences in the substrate binding and catalytic mechanism from α-AADHs. A number of rationally engineered variants were then obtained with improved activity (by 110-800 times) toward various aliphatic β-amino acids without an enantioselectivity trade-off. Two β-amino acids were prepared by using the outstanding variants with excellent enantioselectivity (>99 % ee) and high isolated yields (86-87 %). These results provide important insights into the molecular mechanism of 3,5-DAHDH, and establish a solid foundation for further design of β-AADHs for the asymmetric synthesis of β-amino acids.

Can perihaematomal radiomics features predict haematoma expansion?

AIM

To evaluate the association between perihaematomal radiomics features and haematoma expansion (HE).

MATERIALS AND METHODS

Clinical and radiological data were collected retrospectively. The 1:1 propensity score matching (PSM) method was used to balance the difference of baseline characteristics between patients with and without HE. Radiomics features were extracted from the intra- and perihaematomal regions. Top HE-associated features were selected using the minimum redundancy, maximum relevancy algorithm. Support vector machine models were used to predict HE. Predictive performance of radiomics features from different regions was evaluated by receiver operating characteristic curve and confusion matrix-derived metrics.

RESULTS

A total of 1,062 patients were enrolled. After PSM analysis, the propensity score-matched cohort (PSM cohort) included 314 patients (HE: n=157; non-HE: n=157). The PSM cohort was distributed into the training (n=218) and the validation cohorts (n=96). The predictive performance of intra- and perihaematomal features were comparable in the training (area under the receiver operating characteristic curve [AUC], 0.751 versus 0.757; p=0.867) and the validation cohorts (AUC, 0.724 versus 0.671; p=0.454). By incorporating intra- and perihaematomal features, the combined model outperformed the single intrahaematomal model in the training cohort (AUC, 0.872 versus 0.751; p<0.001). Decision curve analysis (DCA) further confirmed the clinical usefulness of the combined model.

CONCLUSION

Perihaematomal radiomics features can predict HE. The integration of intra- and perihaematomal signatures may provide additional benefit to the prediction of HE.

Asymmetric Synthesis of N-Substituted α-Amino Esters from α-Ketoesters via Imine Reductase-Catalyzed Reductive Amination

N-Substituted α-amino esters are widely used as chiral intermediates in a range of pharmaceuticals. Here we report the enantioselective biocatalyic synthesis of N-substituted α-amino esters through the direct reductive coupling of α-ketoesters and amines employing sequence diverse metagenomic imine reductases (IREDs). Both enantiomers of N-substituted α-amino esters were obtained with high conversion and excellent enantioselectivity under mild reaction conditions. In addition >20 different preparative scale transformations were performed highlighting the scalability of this system.

EZH2-mediated H3K27me3 enrichment on the lncRNA MEG3 promoter regulates the growth and metastasis of glioma cells by regulating miR-21-3p

OBJECTIVE

Glioma is one of the most common and invasive brain tumors worldwide. Long non-coding RNAs (LncRNAs) play an important role in the development of glioma. However, the regulatory mechanism of LncRNAs in glioma has not been fully elucidated. This study aimed to explore the interaction of lncRNA maternally expressed gene 3 (MEG3) and aberrant histone modification in glioma.

MATERIALS AND METHODS

The expression levels of MEG3 and miR-21-3p in glioma cells were measured by quantitative polymerase chain reaction (qPCR). EZH2 (enhancer of zeste homolog 2) and H3K27me3 expression in glioma cells were detected by Western Blot (WB). The binding site of the promoter of MEG3 by H3K27me3 was confirmed by ChIP-Real-time PCR. The direct target of MEG3 and miR-21-3p in glioma cells was measured by a luciferase reporter assay. Cell proliferation was detected by Cell Counting Kit-8 (CCK8), and cell invasion and migration were measured by Transwell assays.

RESULTS

EZH2 and miR-21-3p were upregulated and MEG3 was downregulated in glioma cells. Silencing of EZH2 inhibited cell proliferation, migration, and invasion in U87 and U251 cells. Meanwhile, the expression of H3K27me3 could be significantly inhibited by EZH2 interference. H3K27me3 protein can bind to MEG3 promoter directly. EZH2 inhibition and MEG3 down-expression in U87 cells reversed the effects of silencing of EZH2 on glioma cell growth and metastasis. However, EZH2 inhibition and MEG3 overexpression in U251 cells restricted cell proliferation, migration, and invasion. Furthermore, miR-21-3p was verified to interact with MEG3 by direct binding. Inhibition of MEG3 promoted U87 cell growth and metastasis, which was further strengthened following the co-transfection of si-MEG3 and miR-21-3p. Overexpressed MEG3 inhibited U251 cell growth and metastasis and a complete reversal of the results observed in the co-transfection of LV-MEG3 and miR-21-3p.

CONCLUSIONS

EZH2 was highly expressed in glioma cells and EZH2-mediated H3K27me3 enrichment on the MEG3 promoter regulated the growth and metastasis of glioma cells by targeting miR-21-3p. It potentially provided a new therapeutic marker targeting glioma.

Strongly correlated superconductivity in a copper-based metal-organic framework with a perfect kagome lattice

Metal-organic frameworks (MOFs), which are self-assemblies of metal ions and organic ligands, provide a tunable platform to search a new state of matter. A two-dimensional (2D) perfect kagome lattice, whose geometrical frustration is a key to realizing quantum spin liquids, has been formed in the π - d conjugated 2D MOF [Cu₃(C₆S₆)] _n (Cu-BHT). The recent discovery of its superconductivity with a critical temperature T _c of 0.25 kelvin raises fundamental questions about the nature of electron pairing. Here, we show that Cu-BHT is a strongly correlated unconventional superconductor with extremely low superfluid density. A nonexponential temperature dependence of superfluid density is observed, indicating the possible presence of superconducting gap nodes. The magnitude of superfluid density is much smaller than those in conventional superconductors and follows the Uemura's relation of strongly correlated superconductors. These results imply that the unconventional superconductivity in Cu-BHT originates from electron correlations related to spin fluctuations of kagome lattice.

Single-photon detection in the mid-infrared up to 10 μm wavelength using tungsten silicide superconducting nanowire detectors

We developed superconducting nanowire single-photon detectors based on tungsten silicide, which show saturated internal detection efficiency up to a wavelength of 10 μm. These detectors are promising for applications in the mid-infrared requiring sub-nanosecond timing, ultra-high gain stability, low dark counts, and high efficiency, such as chemical sensing, LIDAR, dark matter searches, and exoplanet spectroscopy.