Restudy of the upper age limit of Beijing Man site

The chronological position of Beijing Man site was restudied by U-series dating of two calcite samples taken from a stalagmitic flowstone layer intercalated in 1–2 layers. Based on the weighted mean of three measurements performed on the purer one, the upper age limit of this site be 421 ₋₅₄ ⁺¹¹⁰ ka B.P., much greater than former evaluation of 230 ka based on U-series dating of fossil bones. The reliability of the obtained results was discussed.     

外显子与内含子序列分维的双碱基研究

引入碱基间的关联,研究了外显子和内含子序列以双碱基为单位的分维,我们发现在这种情况下,外显子和内显子序列在短程和中程存在自相似性并分别定义了这两个区域的分维。结果表明,短程的分维值Ｄｇ一般比中程的Ｄｍ大,外显子的两个分维值比内含子大。我们改变双联体的位相而分维却不变,这反映出在双联体基础上,外显子的不规则性大于内含子,短程的不规则性大于中程,外显子和内含子序列对以２为周期的结构没有位相的特异性。     

Proper phosphorylation of septin 12 regulates septin 4 and soluble adenylyl cyclase expression to induce sperm capacitation

Septin-based ring complexes maintain the sperm annulus. Defective annular structures are observed in the sperm of Sept12- and Sept4-null mice. In addition, sperm capacitation, a process required for proper fertilization, is inhibited in Sept4-null mice, implying that the sperm annulus might play a role in controlling sperm capacitation. Hence, we analyzed sperm capacitation of sperm obtained from SEPT12 Ser196 phosphomimetic (S196E), phosphorylation-deficient (S196A), and SEPT4-depleted mutant mice. Capacitation was reduced in the sperm of both the Sept12 S196E- and Sept12 S196A-knock-in mice. The protein levels of septins, namely, SEPT4 and SEPT12, were upregulated, and these proteins were concentrated in the sperm annulus during capacitation. Importantly, the expression of soluble adenylyl cyclase (sAC), a key enzyme that initiates capacitation, was upregulated, and sAC was recruited to the sperm annulus following capacitation stimulation. We further found that SEPT12, SEPT4, and sAC formed a complex and colocalized to the sperm annulus. Additionally, sAC expression was reduced and disappeared in the annulus of the SEPT12 S196E- and S196A-mutant mouse sperm. In the sperm of the SEPT4-knockout mice, sAC did not localize to the annulus. Thus, our data demonstrate that SEPT12 phosphorylation status and SEPT4 activity jointly regulate sAC protein levels and annular localization to induce sperm capacitation.     

Acid-Catalyzed nucleophilic substitution and racemization of 3-methoxy-N-desmethyldiazepam enantiomers in methanol

pK_a1 values of 3-methoxy-N-desmethyldiazepam in acetonitrile and methanol containing various acid concentrations were determined by spectrophotometry to be 3.5 and 1.3, respectively. Temperature-dependent racemization of enantiomeric 3-methoxy-N-desmethyldiazepam in methanol containing 0.5 M H₂SO₄ was studied by circular dichroism spectropolorimetry and the racemization reactions were found to follow apparent first-order kinetics. Thermodynamic parameters of the racemization reaction were found to be: E_act = 18.8 kcal/mol, and at 25°C: ΔH^? = 18.3 kcal/mol, ΔS^? = ?14.8 entropy unit, and ΔG^? = 22.7 kcal/mol, respectively. The racemization had an isotope effect (k_H/k_D) of 1.6 at 42°C. Based on the results of this report and those of earlier reports by other investigators, a nucleophilically solvated C3 carbocation intermediate resulting from either a P (plus) or an M (minus) conformation is proposed to be an intermediate and responsible for the stereoselective nucleophilic substitution and the subsequent racemization of 3-methoxy-N-desmethyldiazepam enantiomers. © 1993 Wiley-Liss, Inc.     

Enantioselectivity of esterases in human brain

Subcellular fractions of three human brain specimens were found to contain esterase activities which hydrolyzed racemic oxazepam 3-acetate (rac-OXA). All three human brain preparations were highly selective toward the S-enantiomer of rac-OXA. © 1993 Wiley-Liss, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

“DNA signaturing” database construction for Tetradesmus species identification and phylogenetic relationships of Scenedesmus-like green microalgae (Scenedesmaceae,Chlorophyta)

Species identification of Scenedesmus-like microalgae, comprising Desmodesmus, Tetradesmus, and Scenedesmus, has been challenging due to their high morphological and genetic similarity. After developing a DNA signaturing tool for Desmodesmus identification, we built a DNA signaturing database for Tetradesmus. The DNA signaturing tool contained species-specific nucleotide sequences of Tetradesmus species or strain groups with high similarity in ITS2 sequences. To construct DNA signaturing, we collected data on ITS2 sequences, aligned the sequences, organized the data by ITS2 sequence homology, and determined signature sequences according to hemi-compensatory base changes (hCBC)/CBC data from previous studies. Four Tetradesmus species and 11 strain groups had DNA signatures. The signature sequence of the genus Tetradesmus, TTA GAG GCT TAA GCA AGG ACCC, recognized 86% (157/183) of the collected Tetradesmus strains. Phylogenetic analysis of Scenedesmus-like species revealed that the Tetradesmus species were monophyletic and closely related to each other based on branch lengths. Desmodesmus was suggested to split into two subgenera due to their genetic and morphological distinction. Scenedesmus must be analyzed along with other genera of the Scenedesmaceae family to determine their genetic relationships. Importantly, DNA signaturing was integrated into a database for identifying Scenedesmus-like species through BLAST.     

诱发小麦成熟胚愈伤组织及其再生植株抗盐性变异的研究

本研究以普通小麦成熟胚为起始材料,以平阳霉素(PYM)和正定霉素(ZDM)为诱变剂。发现不同基因型对药物的敏感性不同,其中对药物敏感的在含盐筛选培养基上的存活率高。在诱导培养基内添加一定量的诱变剂可以产生耐盐变异。这种抗性愈伤组织转入与筛选培养基含盐量相同的分化培养基,比较容易产生耐盐再生植株。其M_1、M_2代较亲本系表现株高降低,穗长变短、籽粒饱满度也差;M_1代的结实率仅有5.5%,M_2代恢复到40.9%。利用M_1代和亲本系实生苗叶片,进行脯氨酸含量测定。发现耐盐变异株在无盐的Hoagland溶液中,游离脯氨酸的含量超过亲本系,对盐胁迫不敏感,其耐受力强于对照,具有一定的抗盐稳定性。     

Quantitative Detection of 15 Serum Bile Acid Metabolic Products by LC/MS/MS in the Diagnosis of Primary Biliary Cholangitis

To determine 15 bile acid metabolic products in human serum by liquid chromatography-tandem mass spectrometry (LC/MS/MS) and value their diagnostic outcome in primary biliary cholangitis (PBC). Serum from 20 healthy controls and 26 patients with PBC were collected and went LC/MS/MS analysis of 15 bile acid metabolic products. The test results were analyzed by bile acid metabolomics, and the potential biomarkers were screened and their diagnostic performance was judged by statistical methods such as principal component and partial least squares discriminant analysis and area under curve (AUC). 8 differential metabolites can be screened out: Deoxycholic acid (DCA), Glycine deoxycholic acid (GDCA), Lithocholic acid (LCA), Glycine ursodeoxycholic acid (GUDCA), Taurolithocholic acid (TLCA), Tauroursodeoxycholic acid (TUDCA), Taurodeoxycholic acid (TDCA), Glycine chenodeoxycholic acid (GCDCA). The performance of the biomarkers was evaluated by the AUC, specificity and sensitivity. In conclusion, DCA, GDCA, LCA, GUDCA, TLCA, TUDCA, TDCA and GCDCA were identified as eight potential biomarkers to distinguish between healthy people and PBC patients by multivariate statistical analysis, which provided reliable experimental basis for clinical practice.     

Efficient polymer-mediated delivery system for thiocyclam: Nanometerization remarkably improves the bioactivity toward green peach aphids

The unscientific application of synthetic pesticides has brought various negative effects on the environment, hindering the sustainable development of agriculture. Nanoparticles can be applied as carriers to improve pesticide delivery, showing great potential in the development of pesticide formulation in recent years. Herein, a star polymer (SPc) was constructed as an efficient pesticide nanocarrier/adjuvant that could spontaneously assemble with thiocyclam or monosultap into a complex, through hydrophobic association and hydrogen bonding, respectively, with the pesticide-loading contents of 42.54% and 19.3%. This complexation reduced the particle sizes of thiocyclam from 543.54 to 52.74 nm for pure thiocyclam, and 3 814.16 to 1 185.89 nm for commercial preparation (cp) of thiocyclam. Interestingly, the introduction of SPc decreased the contact angles of both pure and cp thiocyclam on plant leaves, and increased the plant uptake of cp thiocyclam to 2.4–1.9 times of that without SPc. Meanwhile, the SPc could promote the bioactivity of pure/cp thiocyclam against green peach aphids through leaf dipping method and root application. For leaf dipping method, the 50% lethal concentration decreased from 0.532 to 0.221 g/L after the complexation of pure thiocyclam with SPc, and that decreased from 0.390 to 0.251 g/L for cp thiocyclam. SPc seems a promising adjuvant for nanometerization of both pure and cp insecticides, which is beneficial for improving the delivery efficiency and utilization rate of pesticides.     

Engineered nickel bioaccumulation in Escherichia coli by NikABCDE transporter and metallothionein overexpression

Mine wastewater often contains dissolved metals at concentrations too low to be economically extracted by existing technologies, yet too high for environmental discharge. The most common treatment is chemical precipitation of the dissolved metals using limestone and subsequent disposal of the sludge in tailing impoundments. While it is a cost-effective solution to meet regulatory standards, it represents a lost opportunity. In this study, we engineered Escherichia coli to overexpress its native NikABCDE transporter and a heterologous metallothionein to capture nickel at concentrations in local effluent streams. We found the engineered strain had a 7-fold improvement in the bioaccumulation performance for nickel compared to controls, but also observed a drastic decrease in cell viability due to metabolic burden or inducer (IPTG) toxicity. Growth kinetic analysis revealed the IPTG concentrations used based on past studies lead to growth inhibition, thus delineating future avenues for optimization of the engineered strain and its growth conditions to perform in more complex environments.