Conformational changes of antitoxin HigA from Escherichia coli str. K-12 upon binding of its cognate toxin HigB reveal a new regulation mechanism in toxin-antitoxin systems.

HigA functions as the antitoxin in HigB-HigA toxin-antitoxin system. It neutralizes HigB-mediated toxicity by forming a stable toxin-antitoxin complex. Here the crystal structure of isolated HigA from Escherichia coli str. K-12 has been determined to 2.0 Šresolution. The structural differences between HigA and HigA in HigBA complex imply that HigA undergoes drastic conformational changes upon the binding of HigB. The conformational changes are achieved by rigid motions of N-terminal and C-terminal domains of HigA around its central linker domain, which is different from other known forms of regulation patterns in other organisms. As a transcriptional regulator, HigA bind to its operator DNA through the C-terminal HTH motif, in which key residues were identified in this study.

Responses in reproductive organs, steroid hormones and CYP450 enzymes in female Mongolian gerbil (Meriones unguiculatus) over time after quinestrol treatment.

The aim of this study was to assess the effects and reversibility of the synthetic estrogen compound, quinestrol, on the reproductive organs, steroid hormones, and drug-metabolizing enzymes CYP3A4 and CYP1A2 in liver and kidney over time after two quinestrol treatments in female Mongolian gerbils (Meriones unguiculatus). Female gerbils were treated with 4mg/kg quinestrol (9 gerbils/group, 3 treated group) (1 control group, 0mg/kg) for 3days and treated again after 25days. Animals were killed for collection of samples at 5, 10 and 15days after the second treatment ending. Two interval quinestrol treatments significantly increased uterine weight, with trend of increase over time, but no change could be detected in ovarian weights. Quinestrol treatment increased progesterone and estradiol levels, both with trend of decline over time. Quinestrol increased liver and kidney weights and total enzyme content of CYP3A4 and CYP1A2, with trend of decline over time. On the basis of reversible changes of detoxification enzymes or organs, interval quinestrol treatment effectively and reversibly influenced the reproductive hormone and organ to some extent.

Call divergence in three sympatric Rattus species.

To reduce errors in species recognition and the probability of interbreeding that lowers fitness, individuals within sympatric zones shift the signals to differentiate from those of other species. In the present study, the differences of the acoustic features of ultrasounds (courtship calls during heterosexual encounters) and audible calls (distress calls during tail-clamp stress) are compared among three sympatric Rattus species (Rattus andamanensis, R. norvegicus, and R. losea). Results showed that the three species have significantly different call parameters, including call duration, peak frequency, bandwidth, pitch, goodness of pitch, frequency modulation, and Wiener entropy. This study provides quantitative evidence for character displacement in the acoustic signals of closely related sympatric Rattus species. Results indicate that the divergence of acoustic signal has arrived at the quite meticulous degree of evolution. Therefore, the acoustic signal trait is likely involved in the evolution of species diversity in rodents.

[Coal Combustion Reactivity of Different Metamorphic Degree and Structure Changes of FTIR Analysis in Pyrolysis Process].

The combustion reaction of raw coals in the air was analyzed withThermal Gravimetric Analyzer 6300 and FTIR (Fourier Transform infrared spectroscopy). The raw coals came from three different sources which were SL lignite, SH bitumite and TT anthracite. The chars were prepared by fixed bed pyrolysis equipment in different reaction temperature. The overlapping peaks were fitted into some sub-peaks by Gaussian function. The aromatic index (R), aromatic structure fused index (D) and organic maturity index (C) were calculated through sub-peaks areas. It showed that three kinds of ignition temperature of SL, SH and TT were 299.3, 408.2 and 441.0 ℃ respectively. The peak temperature of maximum weight loss rate were 348.6, 480.5 and 507.0 ℃ respectively. With the increase of coal rank, both ignition temperature and peak temperature of maximum weight loss rate increased in some degree. The result showed that coal structure was very complex. Vibration absorption peaks of hydroxyl (­OH), aliphatic hydrocarbons (­CH2，­CH3), aromatic (CC), oxygen-containing functional group(CO, C­O) and other major functional groups could be observed in the infrared spectral curves of all samples. With the increase of pyrolysis temperature, infrared vibration absorption peaks of aliphatic hydrocarbons (­CH2­, ­CH3) were gradually decreased. the stretching vibration peak of CO which was at 1 700 cm-1 almost disappeared after coked at 550 ℃. SL samples' absorption peak area infrared curve of oxygen functional groups at 1 000～1 800 cm-1 was more complex. With the increase of coking temperature they changed more significantly compared with others. While peak position and peak intensity for aromatic CC absorption peaks of SH and TT did not change apparently when temperature was changing. Variation trends of main functional groups among three ranks of coals were obviously different with changes of R, D and C values.

Assessment of effects of mifepristone administration to lactating mice on the development and fertility of their progeny.

AIM: Mifepristone, a synthetic steroid compound that induces abortion, was recently found to potentially pass into human milk. This study aimed to determine the effects of mifepristone administration to lactating mice on the development and reproduction of their progeny. METHODS: Lactating mice were gavage fed with mifepristone (8 mg/kg) daily for 4 days either from days 1-4 or from days 7-10 of lactation; controls received only peanut oil. Growth, mortality rate, organ weight to bodyweight ratio, sex hormone at 20, 40 and 60 days, fertility of these F1 progeny and litter size, sex ratio and mortality rate of the second generation were recorded. RESULTS: No significant differences were observed in the average bodyweight, mortality rate of the female or male pups, and organ coefficient of uterus and ovaries of females in adulthood in comparison with the controls. However, the organ coefficient of testis at day 20 and 40 and testosterone concentration at day 60 were increased in male pups. Moreover, the reproductive capacity of the F1 pups was unaffected by 4 days exposure to mifepristone via their mother's milk: time to birth of F2 pups, litter size, sex ratio and mortality rate were similar to control F1 pups. CONCLUSION: The study showed that treating lactating mice with 8 mg/kg mifepristone influenced only the organ coefficient of testis at day 40 and the testosterone concentration in male pups at day 60, however, it did not affect the development and fertility of female and male pups.

Study on mechanical properties and acoustic emission characteristics of deep diorite under uniaxial compression.

The research object is diorite in the Lingbei TBM section of the Hanjiang-To-Weihe River Qinling tunnel, with a buried depth of over 1 km. Using MTS-2000 microcomputer-controlled electro-hydraulic servo universal testing machine and DS5-16b acoustic emission (AE) monitoring system, uniaxial compression and acoustic emission monitoring tests were carried out on rock samples, to study the uniaxial compression mechanical properties and acoustic emission characteristics of the deep diorite. The results of the study indicate that: (1) During uniaxial compression, diorite undergoes four stages: initial compaction, elasticity, yield and failure, in which the curve of the initial compaction stage is significantly smoother. The uniaxial compressive strength is 41.95 MPã102.42 MPa, with an average of 74.07 Mpa; The axial peak strain ranges from 1 % to 1.4 %, and the failure mode belongs to brittle ductile splitting failure. (2) The cumulative ringing count and energy showed a very slow increase trend during the calm period; After entering a surge period (with the appearance of Kaiser points), both show a significant transition state; During the slow increase period, the overall growth rate of the two slowed down and remained almost silent. (3) On the basis of the analysis of RA-AF values during the deformation and rupture process of diorite, it can be seen that the damage type of diorite is tensile damage by the significant low RA value and high AF value characteristics, which coincides with the actual damage fracture characteristics of the rocks in the sample. (4) During the compaction stage, there are few acoustic emission location points, which correspond to low energy and are mainly distributed at the higher and lower ends of the sample; After entering the elasticity stage, the number of positioning points significantly increases and gradually expands towards the middle; Near Kaiser point, the number of location points and corresponding energy are both in a sharp increase state, and this trend is in good agreement with the changes in the ringing count-time and energy-time curves. (5) The damage time mainly starts at the end of the calm period, and the pattern of change in the damage curve coincides with the localization point and energy evolution. The results of the research can be used as a referential basis for the development of the excavation, protection and other construction plans for the Lingbei TBM section of the Hanjiang-To-Weihe River Qinling tunnel or similar surrounding rock tunnels, as well as for further conducting triaxial unloading tests on diorite.

Structure analysis of the global metabolic regulator Crc from Pseudomonas aeruginosa.

The global metabolic regulator catabolite repression control (Crc) has recently been found to modulate the susceptibility to antibiotics and virulence in the opportunistic pathogen Pseudomonas aeruginosa and been suggested as a nonlethal target for novel antimicrobials. In P. aeruginosa, Crc couples with the CA motifs from the small RNA CrcZ to form a post-transcriptional regulator system and is removed from the 5'-end of the target mRNAs. In this study, we first reported the crystal structure of Crc from P. aeruginosa refined to 2.20 Å. The structure showed that it consists of two halves with similar overall topology and there are 11 ß strands surrounded by 13 helices, forming a four-layered α/ß-sandwich. The circular dichroism spectroscopy revealed that it is thermostable in solution and shares similar characteristics to that in crystal. Comprehensive structural analysis and comparison with the homologies of Crc showed high similarity with several known nucleases and consequently may be classified into a member exodeoxyribonuclease III. However, it shows distinct substrate specificity (RNA as the preferred substrate) compared to these DNA endonucleases. Structural comparisons also revealed potential RNA recognition and binding region mainly consisting of five flexible loops. Our structure study provided the basis for the future application of Crc as a target to develop new antibiotics.

Crystal and solution structures of methyltransferase RsmH provide basis for methylation of C1402 in 16S rRNA.

RsmH is a specific AdoMet-dependent methyltransferase (MTase) responsible for N(4)-methylation of C1402 in 16S rRNA and conserved in almost all species of bacteria. The methylcytidine interacts with the P-site codon of the mRNA and increases ribosomal decoding fidelity. In this study, high resolution crystal structure (2.25Å) of Escherichia coli RsmH in complex with AdoMet and cytidine (the putative rRNA binding site) was determined. The structural analysis demonstrated that the complex consists of two distinct but structurally related domains: the typical MTase domain and the putative substrate recognition and binding domain. A deep pocket was found in the conserved AdoMet binding domain. It was also found that the cytidine bound far from AdoMet with the distance of 25.9Å. It indicates that the complex is not in a catalytically active state, and structural rearrangement of RsmH or the nucleotides neighboring C1402 may be necessary to trigger catalysis. Although there is only one molecule in the asymmetric unit of the crystals, RsmH can form a compact dimer across a crystallographic twofold axis. Further analysis of RsmH by small-angle X-ray scattering (SAXS) also revealed the dimer in solution, but with a more flexible conformation than that in crystal, likely resulting from the absence of the substrate. It implies that an active status of RsmH in vivo is achieved by a formation of the dimeric architecture. In general, crystal and solution structural analysis provides new information on the mechanism of the methylation of the fine-tuning ribosomal decoding center by the RsmH.

[Influence of synthetic technology on the structure and luminescent properties of Sr3B2O6:Eu2+ yellow phosphor].

The Sr3B2O6:Eu(2+) yellow phosphor for warm white LED was synthesized by high temperature solid phase method. The influences on the phosphor structure and luminous properties of sintering temperature and holding time were systematically studied. Results indicated that the optimum synthetic temperature and soaking is 1 150 degrees C and 2 hours respectively. The crystalline structure of phosphor is rhombohedral Sr3B2O6. Sintering temperature and holding time has a significant influence on grain development. The excitation spectrum of phosphor composes of a wide-band spectrum main peaking at 398 nm, and the phosphor can be excited by near ultraviolet and blue light. The luminescence spectrum of phosphor is a broad spectrum peaking at 574 nm. Sintering temperature and holding time have a main effect on luminous intensity of phosphor.

Towards fully ab initio simulation of atmospheric aerosol nucleation.

Atmospheric aerosol nucleation contributes to approximately half of the worldwide cloud condensation nuclei. Despite the importance of climate, detailed nucleation mechanisms are still poorly understood. Understanding aerosol nucleation dynamics is hindered by the nonreactivity of force fields (FFs) and high computational costs due to the rare event nature of aerosol nucleation. Developing reactive FFs for nucleation systems is even more challenging than developing covalently bonded materials because of the wide size range and high dimensional characteristics of noncovalent hydrogen bonding bridging clusters. Here, we propose a general workflow that is also applicable to other systems to train an accurate reactive FF based on a deep neural network (DNN) and further bridge DNN-FF-based molecular dynamics (MD) with a cluster kinetics model based on Poisson distributions of reactive events to overcome the high computational costs of direct MD. We found that previously reported acid-base formation rates tend to be significantly underestimated, especially in polluted environments, emphasizing that acid-base nucleation observed in multiple environments should be revisited.

[Preparation and characterization of SrS : Eu, Sm phosphor].

In the present paper, SrS : Eu, Sm phosphors for the broad frequency infrared up-conversion were prepared. XRD analysis indicates that the SrS : Eu, Sm samples calcined at 1 100 degrees C for 1 h exhibit good luminescence properties and they are face-center cubic structure of SrS. Excitation spectrum reveals that the samples can be excited by ultra violet and visible light. Fluorescence spectrum of the samples is composed of four emission peaks at 567 nm, 589 nm, 602 nm and 648 nm respectively. Infrared photo-stimulation luminescence spectrum is a broad-band spectrum peaking at about 595 nm. Infrared response range of the samples is mainly between 800 and 1 400 nm.

[Preparation and characterization of MgxZn(1-x)O powders].

MgxZn(1-x)O has been subjects of intense attention as a novel photo-electronic functional material in recent years. In the present paper, MgxZn(1-x)O powders were prepared by sol-gel method. Effects of Mg contents on MgxZn(1-x)O structure and luminescence properties were studied. The authors observed that MgxZn(1-x)O exhibited two kinds of structures, hexagonal wurtzite and face center cubic while x was in the range of 0 and 1. The MgxZn(1-x)O powders were hexagonal wurtzite structure with x < 0.2, face center cubic structure with x > 0. 2 and their blend structure with x between 0.2 and 0.8. Luminescence spectrum analysis indicated that all MgxZn(1-x)O samples with various composition showed luminescence of ultra-violet and visible light. The ultraviolet emission peak was from 370 nm to 384 nm and the visible emission peak was around at 468 nm. The average size of MgxZn(1-x)O powders was about 100 nm.

[Synthesis and characterization of broadband IR-to-visible upconversion material caS : Ce, Sm by low-temperature combustion synthesis method].

Broadband IR-to-visible upconversion material CaS : Ce, Sm was synthesized for the first time by the low-temperature combustion synthesis (LCS) method. The effect of the rare earth dopant concentration on the upconversion properties was studied. XRD analysis shows that the sample features the cubic CaS crystal structure. The excitation spectrum of the sample is in the range of 200-500 nm, i. e. ultraviolet light or the visible light can excite the sample effectively to complete the "charged" process, and the excitation effect of the visible light is dominant. The IR sensitivity spectrum of the sample is in the range of 800-1 400 nm, indicating that CaS : Ce, Sm possesses the broadband IR-to-visible upconversion effect. The IR-to-visible upconversion spectrum of the sample is a broadband spectrum in the range of 450-650 nm, with two adjacent emission peaks at 513.4 and 572 nm, resulting from the transitions of Ce3+2T2g(5d)-->2F5/2 (4f) and the transitions of Ce3+2T2g(5d)-->2F7/2 (4f), respectively.

[The high level expression of CTLA-4/Ig fusion protein in CHO cell].

OBJECTIVE: To establish the basis in the function study and clinical application of the fusion protein of cytotoxic T lymphocyte antigen 4 CTLA-4 and IgG Crl (CTLA-4/Ig), by studying the expression of CTLA-4/Ig fusion protein in eukaryotic CHO cells and purifying CTLA-4/Ig fusion protein expressing in CHO cells. METHODS: The CHO/dhfr- cells were transfected with linearized plasmids of pMM-CTLA-4-IgG4/WG and pMMGR. The clones of CHO/pCTLA-4+/pMMGR+ were in suspension cultured in serum-free culture media. The expression level of CTLA-4/Ig fusion protein in cell culture media was detected through Western blot. The biological identification of relative molecular mass, purity and antigen specificity of the expressing CTLA-4/Ig fusion protein that have been purified with protein A affinity chromatography was studied by SDS-PAGE or Western blot respectively. RESULTS: The CHO cells that could steadily express at high level the CTLA-4/Ig fusion protein was selected for cloning. By SDS-PAGE for the CTLA-4/Ig fusion protein that have been purified with protein A affinity chromatography, a protein band was found to match well with the predicted relative molecular mass. This protein could specifically bind with human CTLA-4 monoclonal antibody. CONCLUSION: The CHO cells that can express steadily CTLA-4/Ig fusion protein that is of the bioactivity at high level are successfully obtained.

Effects of quinestrol on the vocal behavior of mice during courtship interactions.

Vocalizations are a crucial part of courtship and mating in a wide variety of species. Mating behavior, including courtship calls, is modulated by sex steroid hormones. Male mice produce courtship ultrasonic vocalizations to attract females during heterosexual encounters. However, rare is the knowledge on whether vocal behavior of mice changes under sterilant treatment which will affect gonadal hormone levels. In the present study, we treat male mice with quinestrol, which interferes with the release of the gonadotropin-releasing hormone (GnRH) and has a significant anti-fertility effect in rodents. We compared the differences in the syllable structures (including peak intensity, peak frequency, duration, and bandwidth), total number of calls, and harmonic syllable proportions between quinestrol treated and control male mice. Male mice treated with quinestrol produced more courtship calls and more harmonic syllables than control mice, whereas the parameters of call syllables showed no significant change between the two groups. The results indicate that normal male vocal behavior during sexual interactions could be retained or even reinforced after quinestrol treatment. In addition, female mice approached male mice treated with quinestrol more than control mice, suggesting that the treated male mice were more attractive to the female mice than the controls. Thus, competitive reproductive interference is enhanced. Further, findings provided behavior mechanism in vocal context of the fertility control in mice.

CryoEM structure of yeast cytoplasmic exosome complex.

The eukaryotic multi-subunit RNA exosome complex plays crucial roles in 3'-to-5' RNA processing and decay. Rrp6 and Ski7 are the major cofactors for the nuclear and cytoplasmic exosomes, respectively. In the cytoplasm, Ski7 helps the exosome to target mRNAs for degradation and turnover via a through-core pathway. However, the interaction between Ski7 and the exosome complex has remained unclear. The transaction of RNA substrates within the exosome is also elusive. In this work, we used single-particle cryo-electron microscopy to solve the structures of the Ski7-exosome complex in RNA-free and RNA-bound forms at resolutions of 4.2 Å and 5.8 Å, respectively. These structures reveal that the N-terminal domain of Ski7 adopts a structural arrangement and interacts with the exosome in a similar fashion to the C-terminal domain of nuclear Rrp6. Further structural analysis of exosomes with RNA substrates harboring 3' overhangs of different length suggests a switch mechanism of RNA-induced exosome activation in the through-core pathway of RNA processing.

[Study on rare earth doped long luminescence glass].

A luminosilicate glass samples doped with Eu203 and Dy2O3 were prepared under the air and reducing atmosphere respectively. The excitation spectra, emission spectra and thermal luminescence spectra of the samples prepared under different atmosphere were measured. Luminescence mechanism of the afterglow glasses wa s analyzed. The results showed that the sample prepared under an ambient atmosphere has no afterglow. Its excitation and emission spectra showed the typical transitions of (5)Di( i = 0, 1) --> (7)Fj (j = 0-4) from Eu3+ but the sample reheated at a reducing atmosphere has afterglow. The sample doped with Eu2+ shows luminescence peaking at 462 nm. And the sample codoped with Eu2+ and Dy3+ shows luminescence peaking at 457 nm. The afterglowluminescence can last more than 12 h.

[Preparation and characterization of CaAl2O4:Eu2+, Nd3+ nanoparticles].

Long persistent phosphoresceoce CaAl2O4:Eu2+, Nd3+ nanoparticles were synthesized through sol-gel method. The structures and properties of the samples were analyzed by DTA, TGA, XRD, TEM and spectrometer. Results indicated that the CaAl2O4 crystalline phase was formed at 800 degrees C. The particles are spherical in shape and about 20-40 nm in size. The peaks of the excitation, emission and thermoluminescence spectra shift compared with the CaAl2O4: Eu2+,Nd3+ coarse crystals. The luminescence decay includes a initial rapid part and a following slow part. The decay time lasts for about 5 h.

Immobilized Tryptophanyl-tRNA Synthetase from Bacillus subtilis.

In order to investigate the recognition mechanism and the relationship between structure and function of tRNA(Trp) with tryptophanyl-tRNA synthetase (TrpRS), TrpRS from Bacillus subtilis was purified and immobilized on CNBr-activated Sepharose 4B. Protein recovery and activity recovery of the immobilization were 95.5% and 31.3%, respectively. Properties of immobilized TrpRS were studied in detail. The thermal stability and the shelf stability of immobilized TrpRS were much higher than those of the native TrpRS. Besides these, the immobilized TrpRS, with good operation stability, had increased optimum temperature and optimum pH. A 56-base single-stranded RNA library containing 20 consecutive completely randomized bases was subjected to 3 successive rounds of immobilized TrpRS column selection with SELEX method, resulting in a sharp increase of the percentage of the RNA pool that could bind immobilized TrpRS from 4.3% for the first round pool to 14.7% for the third-round pool. After sequencing the third-round RNA pool, a RNA secondary structure resembling the structure of the acceptor stem in tRNA(Trp) was obtained though the selection. All the results indicated that immobilized TrpRS could be used as an affinity chromatography matrix and was qualified for the SELEX of a RNA pool simulating tRNA(Trp) molecule.

Isolation and Identification of Membrane Proteins Binding to Transfer RNA.

Crude extract of total membrane proteins of yeast was obtained by a method of phase separation in Triton X-114. The membrane extract was applied to the affinity column on which yeast total tRNAs were covalently coupled to hydrazinyl Sepharose 4B. By eluting with increasing concentration gradient of (NH(4))(2)SO(4), eluted proteins were found between concentrations of (NH(4))(2)SO(4) 0.1 mol/L to 0.3 mol/L. By gel mobility-shift assays, it was also observed that there were more than two mobility-shift bands on the gel electropherogram after incubation of sample of (32)P-labeled tRNA with the eluent proteins and the reaction mixtures were analyzed by non-denaturing polyacrylamide gel electrophoresis. These results confirm that these eluted proteins contain two major tRNA specific binding proteins.