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Background Cancer cells including cancer stem cells exhibit a higher rate of ribosome biogenesis than normal cells to support rapid cell proliferation in tumors. However, the molecular mechanisms governing the preferential ribosome biogenesis in glioma stem cells (GSCs) remain unclear. In this work, we show that the novel INHAT repressor (NIR) promotes ribosomal DNA (rDNA) transcription to support GSC proliferation and glioblastoma (GBM) growth, suggesting that NIR is a potential therapeutic target for GBM. Methods Immunoblotting, immunohistochemical and immunofluorescent analysis were used to determine NIR expression in GSCs and human GBMs. Using shRNA-mediated knockdown, we assessed the role and functional significance of NIR in GSCs and GSC-derived orthotopic GBM xenografts. We further performed mass spectrometry analysis, chromatin immunoprecipitation, and other biochemical assays to define the molecular mechanisms by which NIR promotes GBM progression. Results Our results show that high expression of NIR predicts poor survival in GBM patients. NIR is enriched in the nucleoli of GSCs in human GBMs. Disrupting NIR markedly suppresses GSC proliferation and tumor growth by inhibiting rDNA transcription and pre-ribosomal RNA synthesis. In mechanistic studies, we find that NIR activates rDNA transcription to promote GSC proliferation by cooperating with Nucleolin (NCL) and Nucleophosmin 1 (NPM1), 2 important nucleolar transcription factors. Conclusions Our study uncovers a critical role of NIR-mediated rDNA transcription in the malignant progression of GBM, indicating that targeting this axis may provide a novel therapeutic strategy for GBM.

The purpose of video steganography is to hide messages in the video file and prevent them from being detected, and finally the secret message can be extracted completely at the receiver. In this paper, an end-to-end video steganography based on GAN and multi-scale deep learning network is proposed, which consists of the encoder, decoder and discriminator. However, in the transmission process, videos will inevitably be encoded. Thus, a noise layer is introduced between the encoder and the decoder, which makes the model able to resist popular video compressions. Experimental results show that the proposed end-to-end steganography has achieved high visual quality, large embedding capacity, and strong robustness. Moreover, the proposed method performances better compared to the latest end-to-end video steganography.

In this paper, the inherent self-similarity between seismic characteristics and the dynamic behavior of a concrete gravity dam under decomposed near-fault ground motions is investigated. The representative low- and high-frequency components were decomposed using the continuous wavelet transform method to explore their effects on the dam response. The Koyna concrete gravity dam system was used as the basis for a numerical model. A series of dam dynamic responses under near-fault motion with and without pulse properties were obtained by numerical analyses. The relationship between the proposed dimensionless indices (intensity measure ratio (ΦIM), pulse period ratio (T1/Tp)), and response ratio (ΨEDP, m) was established to study the inherent self-similarity in the dynamic behavior of dams, which has an explicit physical significance with smaller dispersion. The response proportions of two main frequency components in the original near-fault record were revealed. Furthermore, a series of new threshold values were calculated based on the intersection of the pulse and high-frequency ratios, and the range of influence of the low- and high-frequency components was quantitatively divided. Finally, a predictive model was proposed for the dam responses to near-fault ground motions containing the proposed dimensionless indices that exhibited reasonable patterns. The pulse-like seismic characteristics and seismic responses to near-fault ground motions were analyzed and selected in the context of sensitivity, inherent self-similarity, threshold point, and regression error. Results show that the self-similarity between Φ S a ( T 1 ) , ΦASI and ΨDVR,pulse, Ψ DVR n , p u l s e is superior to that of other parameter ratios, indicating that more attention should be given to the role of intensity and pulse parameters in practical concrete dam seismic design.

The nucleoprotein (NP) of influenza virus is the core component of the ribonucleoprotein (RNP) and performs multiple structural and functional roles. Structures of the influenza A, B and D NP molecules have been solved previously, but structural information on how NP interacts with RNA remains elusive. Here we present the crystal structure of an obligate monomer of H5N1 NP in complex with RNA nucleotides to 2.3 Å, and a C-terminal truncation of this mutant, also in complex with RNA nucleotides, to 3 Å. In both structures, three nucleotides were identified near two positive grooves of NP suggested to be important for RNA binding. Structural evidence supports that conformational changes of flexible loops and the C-terminal tail both play important roles in the binding of RNA. Based on the structure, we propose a mechanism by which NP captures RNA by flexible loops and transfers it onto the positive binding grooves. Binding of RNA by NP is a crucial step for template re-encapsidation during transcription and replication and cRNP formation. Our structures thus provide insights into the molecular virology of the influenza virus.

Cancer cells including cancer stem cells exhibit a higher rate of ribosome biogenesis than normal cells to support rapid cell proliferation in tumors. However, the molecular mechanisms governing the preferential ribosome biogenesis in glioma stem cells (GSCs) remain unclear. In this work, we show that the Novel INHAT Repressor (NIR) promotes ribosomal DNA (rDNA) transcription to support GSC proliferation and glioblastoma (GBM) growth, suggesting that NIR is a potential therapeutic target for GBM.Immunoblotting, immunohistochemical and immunofluorescent analysis were used to determine NIR expression in GSCs and human GBMs. Using shRNA-mediated knockdown, we assessed the role and functional significance of NIR in GSCs and GSC-derived orthotopic GBM xenografts. We further performed mass spectrometry analysis, chromatin immunoprecipitation and other biochemical assays to define the molecular mechanisms by which NIR promotes GBM progression.Our results show that high expression of NIR predicts poor survival of GBM patients. NIR is enriched in nucleoli of GSCs in human GBMs. Disrupting NIR markedly suppresses GSC proliferation and tumor growth through inhibiting rDNA transcription and pre-rRNA synthesis. In mechanistic studies, we find that NIR activates rDNA transcription to promote GSC proliferation by cooperating with Nucleolin (NCL) and Nucleophosmin 1 (NPM1), two important nucleolar transcription factors.Our study uncovers a critical of NIR-mediated rDNA transcription in malignant progression of GBM, indicating that targeting this axis may provide a novel therapeutic strategy for GBM.

TGF-β is synthesized as a proprotein that dimerizes in the endoplasmic reticulum. After processing in the Golgi to cleave the N-terminal prodomain from the C-terminal growth factor (GF) domain in each monomer, pro-TGF-β is secreted and stored in latent complexes. It is unclear which prodomain and GF monomer are linked before proprotein convertase cleavage and how much conformational change occurs following cleavage. We have determined a structure of pro-TGF-β1 with the proprotein convertase cleavage site mutated to mimic the structure of the TGF-β1 proprotein. Structure, mutation, and model building demonstrate that the prodomain arm domain in one monomer is linked to the GF that interacts with the arm domain in the other monomer in the dimeric structure (i.e. the prodomain arm domain and GF domain in each monomer are swapped). Swapping has important implications for the mechanism of biosynthesis in the TGF-β family and is relevant to the mechanism for preferential formation of heterodimers over homodimers for some members of the TGF-β family. Our structure, together with two previous ones, also provides insights into which regions of the prodomain–GF complex are highly structurally conserved and which are perturbed by crystal lattice contacts.

Significance Complement is deposited on foreign antigens and particles and marks them for recognition by immune cells and removal by phagocytes. Immune cells have two homologous integrins, α X β 2 and α M β 2 , that recognize the complement fragment iC3b. Although it might have been suspected that these integrins would bind to the same site on iC3b, direct comparisons here show they do not. Using negative stain electron microscopy and purified integrin fragments and iC3b, we show that α X β 2 binds to two distinct sites on iC3b. A single α M β 2 integrin binds to two different sites on iC3b, each of which is distinct from those to which α X β 2 binds. Our findings reveal remarkable diversity among integrins that recognize complement and suggest possible cooperative responses.

HBO1, a member of the MYST family of histone acetyltransferases (HATs), is required for global acetylation of histone H3K14 and embryonic development. It functions as a catalytic subunit in multisubunit complexes comprising a BRPF1/2/3 or JADE1/2/3 scaffold protein, and two accessory proteins. BRPF2 has been shown to be important for the HAT activity of HBO1 toward H3K14. Here we demonstrated that BRPF2 can regulate the HAT activity of HBO1 toward free H3 and H4, and nucleosomal H3. Particularly, a short N-terminal region of BRPF2 is sufficient for binding to HBO1 and can potentiate its activity toward H3K14. The crystal structure of the HBO1 MYST domain in complex with this segment of BRPF2 together with the biochemical and cell biological data revealed the key residues responsible for the HBO1–BRPF2 interaction. Our structural and functional data together indicate that the N-terminal region of BRPF2 plays an important role in the binding of HBO1 and a minor role in the binding of nucleosomes, which provide new mechanistic insights into the regulation of the HAT activity of HBO1 by BRPF2.

A nonlinear damage ETA-PDE method is proposed for the fragility analysis of concrete dam. The endurance time analysis (ETA) method and the generalized probability density evolution (PDE) method are constructed by optimization and the method of lines (MOL) algorithm especially for the randomness of ground motion. Then, by integrating the ETA method and generalized PDE method, a nonlinear damage ETA-PDE method is established. To verify the applicability and reliability of the proposed ETA-PDE method, by using the tensile damage model, the nonlinear damage dynamic calculation and the fragility analysis are carried out for the Koyna concrete gravity dam. The results show the proposed PDE method can capture details of the probability density distribution for the fragility indicators (such as the plastic dissipation energy, the damage dissipation energy, the damage volume and so on). The proposed ETA-PDE method has special advantages on the calculating scale and solving probability density. Thus, it is suitable for practical engineering applications.

The tectonic setting on both the northern and southern sides of the Dabie Mountains reveals that low-grade metamorphic rocks are important constituents produced by the subduction of the oceanic crust prior to collision between the Sino-Korean and Yangtze cratons. The Zhangbaling Group/Mulanshan schist is a pre-Ordovician oceanic crust. The Sujiahe and Xinyang/Foziling Groups are trench sediments of the Ordovician-Devonian age, and constitute an accretionary prism associated with subduction. The Yangshan coal measures/Meishan Group was a forearc basin sediment of Carboniferous age, and was overthrust by the accretionary prism during collision. The Susong Group is composed of passive continental margin sediments of the Yangtze craton. Backarc basin sediments are postulated to be concealed by Mesozoic–Cenozoic sediments to the north of the Dabie Mountains. High-ultrahigh pressure terrains are exotic tectonic slices exhumed from depths, located between low-grade metamorphic rocks, and disturb the integrity of the earlier subduction orogen. Subduction occurred during the Ordovician to Devonian periods, and collision initiated at the beginning of the Permian.

Novel luminescent mesoporous silica nanoparticles (MSNs) containing zinc 8-hydroxyquinolinate complexes were prepared by in situ formation route of metal complex in channels of MSNs. The MSNs functionalized with or without mercapto groups had a diameter of 80–170 nm and high surface area (>1010 m2/g). The 8-hydroxyquinolinate (Hq) was introduced into MSNs containing-zinc ions to form the metalloquinolates by in situ route. The metalloquinolates formed in the channels of MSNs were determined as a single coordination mode (Znq). The novel Znq-MSNs exhibit different optical properties as compared with that obtained by direct chemical adsorption of Znq2. Especially, the mercapto-modified MSNs exhibited the strong and stable fluorescent emission at about 500 nm in the pH range of 3–10. The obtained fluorescent MSNs were used in the in vitro researches of controlled release for ibuprofen and the imaging for human cervical cancer cells (HeLa).

The SET- and myeloid-Nervy-DEAF-1 (MYND)-domain containing (Smyd) lysine methyltransferases 1-3 share relatively high sequence similarity but exhibit divergence in the substrate specificity. Here we report the crystal structure of the full-length human Smyd2 in complex with S-adenosyl-L-homocysteine (AdoHcy). Although the Smyd1-3 enzymes are similar in the overall structure, detailed comparisons demonstrate that they differ substantially in the potential substrate-binding site. The binding site of Smyd3 consists mainly of a deep and narrow pocket, while those of Smyd1 and Smyd2 consist of a comparable pocket and a long groove. In addition, Smyd2, which has lysine methyltransferase activity on histone H3-lysine 36, exhibits substantial differences in the wall of the substrate-binding pocket compared with those of Smyd1 and Smyd3 which have activity specifically on histone H3-lysine 4. The differences in the substrate-binding site might account for the observed divergence in the specificity and methylation state of the substrates. Further modeling study of Smyd2 in complex with a p53 peptide indicates that mono-methylation of p53-Lys(372) might result in steric conflict of the methyl group with the surrounding residues of Smyd2, providing a structural explanation for the inhibitory effect of the SET7/9-mediated mono-methylation of p53-Lys(372) on the Smyd2-mediated methylation of p53-Lys(370).

The SET- and MYND-domain containing (Smyd) proteins constitute a special subfamily of the SET-containing lysine methyltransferases. Here we present the structure of full-length human Smyd3 in complex with S-adenosyl-l-homocysteine at 2.8 A resolution. Smyd3 affords the first example that other region(s) besides the SET domain and its flanking regions participate in the formation of the active site. Structural analysis shows that the previously uncharacterized C-terminal domain of Smyd3 contains a tetratrico-peptide repeat (TPR) domain which together with the SET and post-SET domains forms a deep, narrow substrate binding pocket. Our data demonstrate the important roles of both TPR and post-SET domains in the histone lysine methyltransferase (HKMT) activity of Smyd3, and show that the hydroxyl group of Tyr239 is critical for the enzymatic activity. The characteristic MYND domain is located nearby to the substrate binding pocket and exhibits a largely positively charged surface. Further biochemical assays show that DNA binding of Smyd3 can stimulate its HKMT activity and the process may be mediated via the MYND domain through direct DNA binding.

Although moissanite has been found in various rocks, reliable primary moissanite has been reported only from kimberlites and meteorites. The Dabie Mountain moissanite reported in this paper is the first occurrence of primary moissanite hosted by serpentinite. It differs from synthetic silicon carbide in optical properties, inclusions and infrared spectrum. The biaxiality of the Dabie Mountain moissanite is thought to be the result of intracrystal deformation. In reference to the ultrahigh pressure (7—8 GPa) signature of exsolution of rod-like apatite, clinopyroxene and rutile in garnets, and magnetite lamellae in olivine reported in the Dabieshan, we inferred that the moissanite from the Dabie Mountains was probably generated at a depth of 180 km; and then subducted to a depth of 210—250 km, where the moissanite became biaxial before its exhumation.

Zircon SHRIMP U–Pb ages and cathodoluminescence (CL) images reveal that most zircon separated from two tonalitic gneiss samples in the northern Dabie high T / P metamorphic zone (NDZ) have four different domains: (1) inherited core, with clear oscillatory zoning, low- P mineral inclusions and high Th/U ratios, indicating the Neoproterozoic age of the protolith; (2) inner-mantle, with homogeneous CL intensity, low Th/U ratios of ≤ 0.09 and occasionally ultrahigh pressure metamorphic (UHPM) mineral inclusions such as diamond, garnet and rutile, which defined a weighted mean 206 Pb/ 238 U age of 218 ± 3 Ma, corresponding to the age of ultrahigh-pressure metamorphism; (3) outer-mantle with lower Th/U ratio and retrograde mineral inclusions, which yields a retrogressive age of 191 ± 5 Ma; and (4) rim, which is black luminescence, with relatively high Th/U ratios of 0.12–0.40 and a weighted mean 206 Pb/ 238 U age of 126 ± 5 Ma, indicating an overprint of the Early Cretaceous migmatization. Consequently, four discrete and meaningful age groups have been identified. Remarkably, the U–Pb ages of both UHPM zircon and retrograded metamorphic zircon from the NDZ are significantly younger than the U–Pb ages of 238 ± 3 Ma–230 ± 4 Ma for UHPM zircon and U–Th–Pb ages of 218 ± 1.2 Ma–209 ± 3 Ma for rutile and monazite overgrowths (representing the cooling or retrograded metamorphic time corresponding to amphibolite-facies) from the southern Dabie UHPM zone (SDZ), respectively. Combined with reported ages for UHPM rocks from the NDZ, SDZ and Huangzhen low- T eclogite zone (HZ), we found that the metamorphic ages of these three UHPM units in the Dabie orogen gradually decrease from south to north. This age distribution suggests that the three UHPM units represent 3 exhumed crustal slices, which are decoupled from each other and have different subduction and exhumation histories. Firstly, the subducted Huangzhen crustal slice was detached from the underlying subducted continental lithosphere, and then exhumed because of the buoyancy. In the meantime, subduction of underlying continental plate continued. After the initiation of this process, lithologic separations or decoupling within subducted continental crust occurred repeatedly several times to form an imbricate megastructure in the Dabie UHPM belt.

We have found >10 in situ microdiamonds in thin sections of eclogites from the Dabie and Su-Lu regions of central eastern China since the first occurrence of microdiamond in eclogites from the Dabie Mountains (DMT) reported in 1992. The microdiamonds are found not only in the central part but also in the northern part of the DMT. Several free crystals have been recovered from the crushed eclogites from the central DMT. Most in situ microdiamonds are inclusions in garnets but a few larger ones are intergranular. Most of the diamondiferous eclogites in the central part of the DMT are associated with coesite. Most importantly, the observation of microdiamonds in northern Dabie lead us to question the supposition that this is a low-P metamorphic terrane. All the diamondiferous eclogites from both the north and central DMT are of continental affinity as demonstrated by their negative εNd values. Therefore, both the north and central eclogite belts in the DMT are considered to be from the deep subducted terrane. Five in situ microdiamonds and two free crystals are first reported in this paper. The dimensions of the in situ microdiamonds are 30–180 µm and the free crystals are up to 400–700 mm across. All the microdiamonds are confirmed as such by Raman spectroscopy. The results of an infrared spectroscopic investigation on two larger free crystals and two in situ microdiamonds show that all the microdiamonds from both the Dabie and Su-Lu regions are mixed types IaA and IaB diamonds and there is no indication of any synthetic microdiamonds in our samples because such synthetic microdiamonds are always rich in type Ib.

As a contribution to the discussion about the “in situ” vs. “exotic” origin of the ultrahigh-pressure metamorphic (UHPM) rocks, and to the real size of the exhumed tectonic units, the Wuhe–Pailou Unit (WPU) in eastern Dabie Shan was studied. The WPU typically consists of two micas—epidote gneiss, marble with minor eclogite, and jadeite-bearing granofels with rare garnetite and eclogite nodules; these lithologies are enclosed within leucocratic granitic gneiss. Jadeite-bearing granofels is the most peculiar lithology of the WPU, being the only felsic rock in Dabie Shan still preserving extensive relics of the UHPM mineral assemblage. The UHP peak assemblage is coesite+jadeite+garnet±epidote±phengite±kyanite, with accessory rutile, apatite, and zircon. All eclogites consist of garnet, omphacite, quartz/coesite, rutile or high-Al titanite±phengite±clinozoisite±kyanite. Two micas—epidote gneiss associated with the jadeite-bearing granofels typically consists of epidote, muscovite, biotite, plagioclase, K-feldspar, rare garnet, and accessory rutile, titanite, apatite, and zircon. Locally, the WPU paragneiss contains garnet with inclusions of phengite, kyanite, rutile, and amphibole+Na plagioclase symplectite after omphacite. A clockwise P–T path was inferred for the WPU, which consists of an early prograde part up to coesite–eclogite facies conditions (P∼3.3 GPa and T∼720 °C), an early decompression stage and a late part characterised by a near-adiabatic decompression down to medium pressure (P∼1.1 GPa, T∼670 °C) and to low-pressure amphibolite-facies conditions, followed by a final cooling to greenschist-facies conditions. Both field and laboratory data consistently suggest that the WPU, characterised by the close association of paragneiss, marble, eclogite, and granofels, is a supracrustal metasedimentary sequence, which underwent subduction, UHPM, and exhumation as a coherent tectonic unit. Therefore, within collisional orogens, large coherent slices of continental crust may be subducted at depths greater than 100 km.

Micro-diamonds were only found ten years ago in eclogite associated with marble at Xindian in the Dabie Mountains. This paper reports our new finding of micro-diamonds not only in eclogites at Maobei in the Sulu region and at Xindian and Laoyoufang in the south part of the Dabie Mountains (South Dabie), but also in eclogites at Baizhangya and Huangweihe in the northern part of the Dabie Mountains (North Dabie) that has usually been considered not to experience ultrahigh pressure metamorphism. Except the micro-diamond at Huangweihe that was found from the artificial heavy sands of zircons used for isotopic dating, the micro-diamonds from other localities were identified in thin sections of the eclogites. Besides a few interstitial grains, most of the micro-diamond grains in thin sections occur as inclusion in garnet. Three crystals of microdiamond at Maobei in the Sulu region are sized in 120, 60 and 30 μm, respectively. Crystal forms look like octahedron and the composite of octahedron and hexahedron. The largest micro-diamond crystal comes from Xindian, which is measured to be 180 μm in diameter with distinct zonal structure and inclusions. The zonal structure occurs as an inclined octahedron inside rounded by an incomplete hexagonal girdle. A smaller micro-diamond inclusion occurs inside the central octahedron, and a larger graphite inclusion is within the outer zone. The Laoyoufang micro-diamond is partially retrograded to graphite. Micro-diamond from the Baizhangya eclogite in the ultramafic rock belt of North Dabie is an aggregate of 70 μm×90 μm in size. All the micro-diamonds are confirmed by the Raman spectrum analysis. The occurrence of the micro-diamonds from the eclogites in the ultramafic rock belt of North Dabie demonstrates that this region was also subjected to ultrahigh pressure metamorphism as well as the South Dabie did.

The compositional zoning of the garnet in a strongly deformed eclogite from Raobazhai foliated peridotite has been recognized. The CaO concentrations of the garnet are decreased from the core to the rim, while its MnO concentrations are increased, suggesting the retrograde origin of such CaO—MnO zoning. The tie line of garnet + omphacite from this eclogite gives a Sm-Nd age of (187 ± 5) Ma, which is less significant than the Sm-Nd ages of (221±5)—(228 ± 3) Ma and (210 ± 6)—(214 ± 6) Ma for ultrahigh-pressure eclogites in the southern Dabie zone and in the northern Dabie zone, respectively. This younger Sm-Nd age could result from the143Nd/144 Nd ratio decrease of the retrograde zone in the garnet. The δ18O values of the garnet and omphacite show that their fractionation values are less than the equilibrium fractionation value between the garnet and omphacite at 500—900°C, which suggests an oxygen isotopic disequilibrium between them.

The petrologic geochemical and Sr-Nd isotopic compositions of the eclogites from the mafic-ultramafic rock belt (MUMRB) in the Northern Dabie Mountains indicate that: (1) the protoliths of most of eclogites are tholeiitic basalt and a few may be gabbro, and most of them produced from the Yangtze subducted continental crust (lower crust and formed during the deep subduction) and a part may be from paleo-oceanic relics between the Yangtze and North China continental plates; (2) their positive Nb anomalies and related trace element characteristics show that they did not form in the island-arc setting; (3) the metamorphosed MUMRB with eclogite and meta-peridotite blocks along the southern part of the Mozitan-Xiaotian fault zone may represent the suture zone produced during the collision between the Yangtze and North China continental plates, which included the Yangtze subducted continental crust and paleo-oceanic relics.

Eclogite from the Northern Dabie Mountain is a new finding by the authors. These eclogites in foliated perdotite are enveloped by banded gneiss and occur in the mafic-ultramafic rock belt. They are mainly composed of omphacite, garnet, diopside, orthopyroxene, amphibole, plagioclase and magnetite, and a small amount of rutile, spinel, olivin and 鏾rundum. The mineral association of peak metamorphism of the eclogite is omphacite+garnet+rutile. The existence of eclogite in the Northern Dabie Mountain implies that there was an eclogitic metamorphism prior to the granulitic facies one in the mafic-ultramafic rock belt.

The kyanite quartzite from the ultrahigh-pressure metamorphic belt in the eastern Dabie Mountains is composed mainly of quartz, kyanite, talc and epidote, which contains a typical mineral assemblage of white schist. It suffered an eclogite facies metamorphism ofP = (2.4 ±0.3) GPa andT = 630 ° C together with coexisting eclogite. The protolith may be an aplite replaced by high-pressure fluid of eclogite facies.

DNA methylation and demethylation regulate many crucial biological processes in mammals and are linked to many diseases. Active DNA demethylation is believed to be catalyzed by TET proteins and a putative DNA decarboxylase that may share some similarities in sequence, structure and catalytic mechanism with isoorotate decarboxylase (IDCase) that catalyzes decarboxylation of 5caU to U in fungi. We report here the structures of wild-type and mutant IDCases from Cordyceps militaris and Metarhizium anisopliae in apo form or in complexes with 5caU, U, and an inhibitor 5-nitro-uracil. IDCases adopt a typical (β/α)8 barrel fold of the amidohydrolase superfamily and function as dimers. A Zn(2+) is bound at the active site and coordinated by four strictly conserved residues, one Asp and three His. The substrate is recognized by several strictly conserved residues. The functional roles of the key residues at the active site are validated by mutagenesis and biochemical studies. Based on the structural and biochemical data, we present for the first time a novel catalytic mechanism of decarboxylation for IDCases, which might also apply to other members of the amidohydrolase superfamily. In addition, our biochemical data show that IDCases can catalyze decarboxylation of 5caC to C albeit with weak activity, which is the first in vitro evidence for direct decarboxylation of 5caC to C by an enzyme. These findings are valuable in the identification of potential DNA decarboxylase in mammals.

This note reports the preiswerkite that was found as the first occurrence in the UHP metamorphic belt of the Dabie Mountain. It occurs in the quartz jadeitite, and coexists with plagioclase, taramite and magnetite as retrograde symplectite. The calculated temperature of formation for preiswerkite is about 600 – 620 °C (at P=1.0 – 1.5GPa), suggesting that the preiswerkite is an indicator mineral of high-grade greenschist facies retrograded from eclogitefacies rocks.

Under experimental conditions, characteristic fracture patterns can be produced on cleavage plates on mica by using a blunt tool. If stress is applied rapidly by striking the surface in a controlled way, a pattern known as the “percussion figure” is produced. When the stress is applied by steady pressure on the tool, a different but complementary pattern of fracture is formed. In sum, these induced fractures constitute the “pressure figure”. The orientation of each of these two sets of fractures with respect to the optical axial plane (OAP) of mica is different and therefore diagnostic of the manner in which they are produced. These patterns are distinct from those formed as a result of exsolution of Fe-Ti oxides which are commonly visible in sections of biotite cut parallel to the basal plane (001). A description is given of percussion figures produced by natural deformation in biotites from mylonite belts cutting the Proterozoic metasediments of the Feidong Group in eastern Anhui Province and another from Yunnan Province, China. The principal fracture of the natural percussion figure evidently is parallel to the (OAP) of the biotite and the other two sets are quite distinct as well, thus identifying it really as a percussion figure. Microscopic inclusions of sphene also are located along the crystallographically controlled fracture planes of the percussion figures. The data indicate that high strain rates would be required to form these natural percussion figures and that a special history of deformation must have affected the mylonites in which they occur. It is proposed that the homogeneous deformation of the mylonite in a ductile regime was complicated by strain hardening which led to episodes of abrupt stress itself relief (stick-slip) at rates of strain high enough to induce the formation of percussion figures in the biotites.

Recent discoveries of UHP eclogites from the northern Dabie Complex (NDC) in central China provide an opportunity to improve our understanding of the tectonic setting of the NDC and exhumation mechanism of UHPM rocks. The petrology, geochemistry, Sr–Nd–O isotopic compositions and Sm–Nd isotopic chronology of some eclogites from the NDC were obtained in this study. The major elemental compositions and relatively low ɛNd (T) of about −10 for the eclogites suggest that the protoliths of most eclogites were ancient basaltic rocks developed in continental crust, and thus these eclogites were produced by subduction of the Yangtze continental crust. However, some of the eclogites within foliated peridotites with relatively high ɛNd (T) values up to +2.4 are interpreted as pieces of lithospheric mantle scraped off the overlying mantle by subducting continental crust and then subducted together into mantle depths. Therefore, the metamorphosed mafic-ultramafic belt containing eclogite and meta-peridotite blocks along the southern part of the Mozitan–Xiaotian fault zone may represent the tectonic melange produced by the subduction of the Yangtze continental crust. The Sm–Nd age of 212±4 Ma defined by garnet+omphacite is interpreted to represent a cooling age corresponding to in the retrograde stage of granulite-facies metamorphism during eclogite exhumation. The relationship between the δ18O values of the eclogitic minerals such as garnet and omphacite from an eclogite sample suggests oxygen isotope equilibrium, pointing to Sm–Nd isotope equilibrium between garnet and omphacite according to comparability between O and Sm–Nd diffusivities. However, the Sm–Nd ‘isochrons’ defined by whole+garnet or omphacite+zonal garnet yield a large age range of 187–266 Ma, which may be produced by Nd isotopic disequilibrium between garnet and retrograded minerals in whole-rocks. Therefore, the eclogites in the NDC also underwent Triassic UHP metamorphism like the UHP eclogites in the southern Dabie Mountains. The δ18O values of whole-rocks for the eclogites are 2.40 to 4.32‰, indicating that protolith of the eclogites in the NDC underwent hydrothermal alteration at high-temperature by surface water before subduction of the Yangtze continental crust during the Triassic period in a manner similar to protoliths of UHP rocks in the southern Dabie Mountains.

The Zhu-Jia-Chong quartz eclogites occur within two mica–epidote–garnet–plagioclase gneiss as lenses up to 200 m thick and more than 1 km long. The eclogite is medium-grained and consists of omphacite, garnet, clinozoisite, minor kyanite and quartz. No evidence for the former presence of coesite was found. Locally, poikiloblastic amphibole occurs, which is zoned from glaucophane in the core to Mg–cummingtonite in the rim. In some localities, clinozoisite occurs as polycrystalline aggregates, interpreted as pseudomorphs after former porphyroblasts of lawsonite. The eclogite is cut by irregular metamorphic veins up to 20 cm thick and several meters long, consisting of kyanite ± zoisite ± omphacite ± rutile ± apatite ± clinozoisite in a quartz matrix. Locally, vein minerals attain pegmatite-like grain size. Geothermobarometric calculations and mineral compatibilities of peak and retrograde minerals of both eclogite and veins indicate a clockwise P–T path, characterized by initial eclogitic conditions prograding from the lawsonite to the epidote stability field. The veins are considered to have formed before peak metamorphic conditions by prograde dehydration of lawsonite to kyanite + zoisite/clinozoisite + quartz + fluid; the fluid released from the reaction favored the growth of coarse-grained vein minerals. The eclogitic peak, estimated at ∼ 24 kbar and 700 °C, is followed by a two-stage retrograde evolution: the earlier stage, characterized by a quasi-adiabatic decompression from eclogite- to the amphibolite-facies conditions, implies a rapid exhumation from depths of ∼ 90 km to mid-crustal levels; the later stage, characterized by slower exhumation rates, led to the final exposure of eclogites and country rocks. The role of lawsonite as storage of fluid in subducting plates is therefore discussed.