Genetically Encoded Photocaged Proteinogenic and Non-Proteinogenic Amino Acids.

Photocaged amino acids could be genetically encoded into proteins via genetic code expansion (GCE) and constitute unique tools for innovative protein engineering. There are a number of photocaged proteinogenic amino acids that allow strategic conversion of proteins into their photocaged variants, thus enabling spatiotemporal and non-invasive regulation of protein functions using light. Meanwhile, there are a hand of photocaged non-proteinogenic amino acids that address the challenges in directly encoding certain non-canonical amino acids (ncAAs) that structurally resemble proteinogenic ones or possess highly reactive functional groups. Herein, we would like to summarize the efforts in encoding photocaged proteinogenic and non-proteinogenic amino acids, hoping to draw more attention to this fruitful and exciting scientific campaign.

Association Between Exposure to Multiple Toxic Metals in Follicular Fluid and the Risk of PCOS Among Infertile Women: The Mediating Effect of Metabolic Markers.

Polycystic ovary syndrome (PCOS) severely affects women's fertility and accompanies serious metabolic disturbances, affecting 5%-20% of women of reproductive age globally. We previously found that exposure to toxic metals in the blood raised the risk of PCOS, but the association between exposure to toxic metals and the risk of PCOS in the follicular fluid, the microenvironment for oocyte growth and development in females, and its effect on metabolism has not been reported. This study aimed to evaluate the associations between the concentrations of cadmium (Cd), mercury (Hg), barium (Ba) and arsenic (As) in FF and the risk of PCOS, and to explore the mediating effect of metabolic markers in FF on the above relationship. We conducted a case-control study, including 557 women with PCOS and 651 controls. Ba, Cd, Hg and As levels in FF were measured by ICP-MS, metabolites levels in FF was measured by LC-MS/MS among 168 participants randomly selected from all the participants. Logistic regression models were used to assess the association of a single metal level with the PCOS risk, and linear regression models were used to assess the relationships of a single metal level with clinical phenotype parameters and metabolites levels. Combined effect of metals mixture levels on the risk of PCOS were assessed via weighted quantile sum (WQS) regression and bayesian kernel machine regression (BKMR). Medication analysis was performed to explore the role of metabolic markers on the relationship of toxic metals levels with the risk of PCOS. The exposure levels of Cd, Hg, Ba and As in FF were all positively and significantly associated with the PCOS risk (with respect to the highest vs. lowest tertile group: OR = 1.57, 95% CI = 1.17 ~ 2.12 for Cd, OR = 1.69, 95% CI = 1.22 ~ 2.34 for Hg, OR = 1.76, 95% CI = 1.32 ~ 2.34 for Ba, OR = 1.42, 95% CI = 1.05 ~ 1.91 for As). In addition, levels of metal mixture also significantly correlated with the risk of PCOS, Cd level contributed most to it. Moreover, we observed significant positive relationships between Cd level and LH (ß = 0.048, 95% CI = 0.002 ~ 0.094), T (ß = 0.077, 95% CI = 0.029 ~ 0.125) and HOMA-IR value (ß = 0.060, 95% CI = 0.012 ~ 0.107), as well as Hg level with LH, FSH/LH ratio and TC. Furthermore, we revealed that estrone sulfate, LysoPE 22:6 and N-Undecanoylglycine were significantly and positively mediating the association between Cd level and the risk of PCOS (with mediated proportion of 0.39, 0.24 and 0.35, respectively), and between Hg level and the risk of PCOS (with mediated proportion of 0.29, 0.20 and 0.46, respectively). These highly expressed metabolites significantly enriched in the fatty acid oxidation, steroid hormone biosynthesis and glycerophospholipids metabolism, which may explain the reason why the levels of Cd and Hg in FF associated with the phenotype of PCOS. Ba and As in FF was not found the above phenomenon. Our results suggested that exposure to multiple toxic metals (Cd, Hg, Ba and As) in FF associated with the increased risk of PCOS, Cd was a major contributor. Levels of Cd and Hg in FF significantly associated with the phenotype of PCOS. The above association may result from that Cd and Hg in FF related with the disturbance of fatty acid oxidation, steroid hormone biosynthesis and the glycerophospholipids metabolism.

Exploring the dynamics and structure of PpiB in living Escherichia coli cells using electron paramagnetic resonance spectroscopy.

The combined effects of the cellular environment on proteins led to the definition of a fifth level of protein structural organization termed quinary structure. To explore the implication of potential quinary structure for globular proteins, we studied the dynamics and conformations of Escherichia coli (E. coli) peptidyl-prolyl cis/trans isomerase B (PpiB) in E. coli cells. PpiB plays a major role in maturation and regulation of folded proteins by catalyzing the cis/trans isomerization of the proline imidic peptide bond. We applied electron paramagnetic resonance (EPR) techniques, utilizing both Gadolinium (Gd(III)) and nitroxide spin labels. In addition to using standard spin labeling approaches with genetically engineered cysteines, we incorporated an unnatural amino acid to achieve Gd(III)-nitroxide orthogonal labeling. We probed PpiB's residue-specific dynamics by X-band continuous wave EPR at ambient temperatures and its structure by double electron-electron resonance (DEER) on frozen samples. PpiB was delivered to E. coli cells by electroporation. We report a significant decrease in the dynamics induced by the cellular environment for two chosen labeling positions. These changes could not be reproduced by adding crowding agents and cell extracts. Concomitantly, we report a broadening of the distance distribution in E. coli, determined by Gd(III)-Gd(III) DEER measurements, as compared with solution and human HeLa cells. This suggests an increase in the number of PpiB conformations present in E. coli cells, possibly due to interactions with other cell components, which also contributes to the reduction in mobility and suggests the presence of a quinary structure.

Using Bayesian and weighted regression to evaluate the association of idiopathic oligoastenoteratozoospermia with seminal plasma metal mixtures.

Idiopathic oligoastenoteratozoospermia (iOAT) affects 30% of infertile men of reproductive age. However, the associations between Cr, Fe, Cu, Se or Co levels and iOAT risk have not been determined. This research aimed to assess the associations between Cr, Fe, Cu, Se and Co levels as well as their mixtures in seminal plasma and the risk of iOAT and severe iOAT. Therefore, a case‒control study including 823 participants (416 iOAT patients and 407 controls) recruited from October 2021 to August 2022 at the reproductive medicine center of the First Affiliated Hospital of Anhui Medical University was conducted in Anhui, China. The concentrations of Cr, Fe, Cu, Se and Co in seminal plasma were detected via inductively coupled plasma‒mass spectrometry. Binary logistic regression models were used to assess the associations between the levels of Cr, Fe, Cu, Se and Co and the risk of iOAT and severe iOAT; additionally, Bayesian kernel machine regression (BKMR) and weighted quantile sum (WQS) regressions were performed to evaluate the joint effect of seminal plasma levels of Cr, Fe, Cu, Se and Co on the risk of iOAT and explore which elements contributed most to the relationship. We found significant associations between the concentrations of Fe, Cu and Se in seminal plasma and iOAT risk after adjusting for covariates (Fe, lowest tertile vs. second tertile: aOR = 1.86, 95% CI = 1.31, 2.64; Cu, lowest tertile vs. second tertile: aOR = 1.95, 95% CI = 1.37, 2.76; Se, lowest tertile vs. second tertile: aOR = 1.65, 95% CI = 1.17, 2.35). A lower Se concentration in seminal plasma (lowest tertile vs. second tertile: aOR = 1.84, 95% CI = 1.10, 3.10) was positively associated with the risk of severe iOAT. Additionally, we also observed an association between the concentration of Cr in seminal plasma and the risk of iOAT before adjusting for covariates (Cr, third tertile vs. lowest tertile: OR=1.44, 95% CI: 1.03, 2.02). According to the BKMR analyses, the risk of iOAT increased when the overall concentrations were less than the 25th percentile. The results from the WQS regression indicated that a negative WQS index was significantly associated with the iOAT risk, while a positive WQS index was not. Se and Fe had significant weights in the negative direction. In conclusion, lower Cu, Fe and Se levels in seminal plasma were positively associated with iOAT risk, while higher Cr levels in seminal plasma were positively associated with iOAT risk according to the single element model, and lower levels of Se were related to a greater risk of severe iOAT; when comprehensively considering all the results from BKMR and WQS regression, Fe, Se and Cr levels contributed most to this relationship.

Elevated levels of Zn, Cu and Co are associated with an increased risk of endometriosis: Results from a casecontrol study.

BACKGROUND: Endometriosis is a common gynecological disease that affects approximately 5 %∼10 % of reproductive-aged women. Zinc (Zn), selenium (Se), copper (Cu), cobalt (Co) and molybdenum (Mo) are essential trace elements and are very important for human health. However, studies on the relationship between mixtures of essential trace elements and the risk of endometriosis are limited and inconsistent. In particular, studies confirming the association via different sample types are limited. OBJECTIVE: This study aimed to investigate the associations between Zn, Se, Cu, Co and Mo concentrations in blood and follicular fluid (FF) and endometriosis risk in a Chinese population. METHODS: A total of 609 subjects undergoing in vitro fertilization (IVF) were recruited; 836 samples were analyzed, including 451 blood samples (234 controls and 217 cases) and 385 FF samples (203 controls and 182 cases). In addition, 227 subjects provided both blood and FF samples. Zn, Se, Cu, Co and Mo concentrations in blood and FF were quantified via inductively coupled plasma-mass spectrometry (ICP-MS). The associations between the levels of Zn, Se, Cu, Co and Mo and the risk of endometriosis were assessed using single-element models (logistic regression models), and the combined effect of the trace elements on endometriosis risk was assessed using multielement models (Bayesian kernel machine regression (BKMR) and weighted quantile sum (WQS) regression). RESULTS: Based on the single-element models, significant associations of Zn concentrations in blood (high-level vs. low-level group: aOR = 14.17, 95 % CI: 7.31, 27.50) and FF (first tertile vs. second tertile group: aOR = 0.34, 95 % CI: 0.16, 0.71; third tertile vs. second tertile group: aOR = 2.32, 95 % CI: 1.38, 3.91, respectively) and Co concentrations in blood (first tertile vs. second tertile group, aOR = 0.24, 95 % CI: 0.12, 0.48) and FF (third tertile vs. second tertile group: aOR = 3.87, 95 % CI: 2.19, 6.84) with endometriosis risk were found after adjustment for all confounders. In FF, Cu and Mo levels were significantly greater among the cases than among the controls, with a positive association with endometriosis risk (Cu (first tertile vs. second tertile group: aOR = 0.39, 95 % CI: 0.19, 0.81; third tertile vs. second tertile group: aOR = 2.73, 95 % CI: 1.61, 4.66, respectively) and Mo (high-level vs. low-level group: aOR = 14.93, 95 % CI: 7.16, 31.12)). However, similar associations between blood Cu and Mo levels and endometriosis risk were not found. In addition, the levels of these five essential trace element mixtures in blood and in FF were significantly and positively associated with endometriosis risk according to the BKMR analyses; the levels of Zn and Cu in blood and the levels of Mo in FF were significantly related to the risk of endometriosis, and the posterior inclusion probabilities (PIPs) were 1.00, 0.99 and 1.00 for Zn and Cu levels in blood and Mo levels in FF, respectively. Furthermore, Zn and Mo were the highest weighted elements in blood and FF, respectively, according to WQS analyses. CONCLUSION: The risk of endometriosis was associated with elevated levels of several essential trace elements (Zn, Cu and Co). Elevated levels of these elements may be involved in the pathomechanism of endometriosis. However, further studies with larger sample sizes will be necessary to confirm these associations.

Site-Specific Anchoring a Luminescent Tag in a Protein with Non-Emissive Iridium(III) Complex.

Site-specific modification of proteins with synthetic fluorescent tag effectively improves the resolution of imaging, and such a labeling method with negligible three-dimensional structural perturbations and minimal impact on the biological functions of proteins is of high interest to dissect the high-resolution activities of biomolecules in complex systems. To this end, several non-emissive iridium(III) complexes [Ir(C-N)2 (H2 O)2 ]+ OTF- (C-N denotes various cyclometalated ligands) were designed and synthesized. These complexes were tested for attaching a protein by coordinating to H/X (HisMet, HisHis, and HisCys) that are separated by i and i+4 in α-helix. Replacement of the two labile water ligands in the iridium(III) complex by a protein HisHis pair increases the luminescent intensity up to over 100 folds. This labeling approach has been demonstrated in a highly specific and efficient manner in a number of proteins, and it is also feasible for labeling target proteins in cell lysates.

C-terminal domain dimerization in yeast Hsp90 is moderately modulated by the other domains.

Heat shock protein 90 (Hsp90) serves as a crucial regulator of cellular proteostasis by stabilizing and regulating the activity of numerous substrates, many of which are oncogenic proteins. Therefore, Hsp90 is a drug target for cancer therapy. Hsp90 comprises three structural domains, a highly conserved amino-terminal domain (NTD), a middle domain (MD), and a carboxyl-terminal domain (CTD). The CTD is responsible for protein dimerization, is crucial for Hsp90's activity, and has therefore been targeted for inhibiting Hsp90. Here we addressed the question of whether the CTD dimerization in Hsp90, in the absence of bound nucleotides, is modulated by allosteric effects from the other domains. We studied full length (FL) and isolated CTD (isoC) yeast Hsp90 spin-labeled with a Gd(III) tag by double electron-electron resonance measurements to track structural differences and to determine the apparent dissociation constant (Kd). We found the distance distributions for both the FL and isoC to be similar, indicating that the removal of the NTD and MD does not significantly affect the structure of the CTD dimer. The low-temperature double electron-electron resonance-derived Kd values, as well as those obtained at room temperature using microscale thermophoresis and native mass spectrometry, collectively suggested the presence of some allosteric effects from the NTDs and MDs on the CTD dimerization stability in the apo state. This was evidenced by a moderate increase in the Kd for the isoC compared with the FL mutants. Our results reveal a fine regulation of the CTD dimerization by allosteric modulation, which may have implications for drug targeting strategies in cancer therapy.

Relaxation-Assisted Magnetization Transfer Phenomena for a Sensitivity-Enhanced 2D NMR.

2D NOESY and TOCSY play central roles in contemporary NMR. We have recently discussed how solvent-driven exchanges can significantly enhance the sensitivity of such methods when attempting correlations between labile and nonlabile protons. This study explores two scenarios where similar sensitivity enhancements can be achieved in the absence of solvent exchange: the first one involves biomolecular paramagnetic systems, while the other involves small organic molecules in natural abundance. It is shown that, in both cases, the effects introduced by either differential paramagnetic shift and relaxation or by polarization sharing among networks of protons can provide a similar sensitivity boost, as previously discussed for solvent exchange. The origin and potential of the resulting enhancements are analyzed, and experiments that demonstrate them in protein and natural products are exemplified. Limitations and future improvements of these approaches are also briefly discussed.

Real-Time Monitoring of the Level and Activity of Intracellular Glutathione in Live Cells at Atomic Resolution by 19F-NMR.

Visualization and quantification of important biomolecules like glutathione (GSH) in live cells are highly important. The existing methods are mostly from optical detection and lack of atomic resolution on the activity of GSH. Here, we present a sensitive 19F-NMR method to quantify real-time variations of GSH in live cells in a reversible manner. This NMR method prevents extracellular leakage and irreversible consumption of intracellular GSH during the detection. The high performance of the reactive 19F-probe enables accurate determination of intracellular GSH content at atomic resolution, from which information on GSH variations with respect to the extracellular and intracellular conditions can be inferred. In addition, we demonstrate the applicability of this NMR method to quantify the GSH levels between different live cell lines and to disclose the distinct differences between the intracellular environment and cell lysates. We foresee the application of 19F-NMR to monitor real-time variations of intracellular GSH levels in relation to GSH-involved central cellular processes.

Constructing Photoactivatable Protein with Genetically Encoded Photocaged Glutamic Acid.

Genetically replacing an essential residue with the corresponding photocaged analogues via genetic code expansion (GCE) constitutes a useful and unique strategy to directly and effectively generate photoactivatable proteins. However, the application of this strategy is severely hampered by the limited number of encoded photocaged proteinogenic amino acids. Herein, we report the genetic incorporation of photocaged glutamic acid analogues in E. coli and mammalian cells and demonstrate their use in constructing photoactivatable variants of various fluorescent proteins and SpyCatcher. We believe genetically encoded photocaged Glu would significantly promote the design and application of photoactivatable proteins in many areas.

Effective assessment of lanthanide ion delivery into live cells by paramagnetic NMR spectroscopy.

We report an effective assessment of lanthanide ion (Ln3+) delivery into live cells by paramagnetic NMR spectroscopy. Free Ln3+ ions are toxic to live cells resulting in a gradual leakage of target proteins to the extracellular media. The citrate-Ln3+ complex is an efficient and mild reagent over the free Ln3+ form for live cell delivery.

Novel economical, accurate, sensitive, single-cell analytical method for mitochondrial DNA quantification in mtDNA mutation carriers.

PURPOSE: Although a variety of analytical methods have been developed to detect mitochondrial DNA (mtDNA) heteroplasmy, there are special requirements of mtDNA heteroplasmy quantification for women carrying mtDNA mutations receiving the preimplantation genetic diagnosis (PGD) and prenatal diagnosis (PD) in clinic. These special requirements include various sample types, large sample number, long-term follow-up, and the need for detection of single-cell from biopsied embryos. Therefore, developing an economical, accurate, high-sensitive, and single-cell analytical method for mtDNA heteroplasmy is necessary. METHODS: In this study, we developed the Sanger sequencing combined droplet digital polymerase chain reaction (ddPCR) method for mtDNA quantification and compared the results to next-generation sequencing (NGS). A total of seventeen families with twelve mtDNA mutations were recruited in this study. RESULTS: The results showed that both Sanger sequencing and ddPCR could be used to analyze the mtDNA heteroplasmy in single-cell samples. There was no statistically significant difference in heteroplasmy levels in common samples with high heteroplasmy (≥ 5%), low heteroplasmy (< 5%), and single-cell samples, either between Sanger sequencing and NGS methods, or between ddPCR and NGS methods (P > 0.05). However, Sanger sequencing was unable to detect extremely low heteroplasmy accurately. But even in samples with extremely low heteroplasmy (0.40% and 0.92%), ddPCR was always able to quantify them. Compared to NGS, Sanger sequencing combined ddPCR analytical methods greatly reduced the cost of sequencing. CONCLUSIONS: In conclusion, this study successfully established an economical, accurate, sensitive, single-cell analytical method based on the Sanger sequencing combined ddPCR methods for mtDNA heteroplasmy quantification in a clinical setting.

Equilibrium between monomers and dimers of the death domain of the p75 neurotrophin receptor in solution.

p75 neurotrophin receptor (p75NTR) contains a C-terminal globular protein module known as the death domain (DD), which plays a central role in apoptotic and inflammatory signaling through the formation of oligomeric protein complexes. A monomeric state of the p75NTR-DD also exists depending on its chemical environment in vitro. However, studies on the oligomeric states of the p75NTR-DD have produced conflicting findings and sparked great controversy. Here we present new evidence from biophysical and biochemical studies to demonstrate the coexistence of symmetric and asymmetric dimers of the p75NTR-DD, which may equilibrate with the monomeric form in solution and in the absence of any other protein. The reversible close-open solution behavior may be important for the p75NTR-DD to serve as an intracellular signaling hub. This result supports an intrinsic ability of the p75NTR-DD to self-associate, in congruence with the oligomerization properties of all members of the DD superfamily.

Efficient Metabolic Fingerprinting of Follicular Fluid Encodes Ovarian Reserve and Fertility.

Ovarian reserve (OR) and fertility are critical in women's healthcare. Clinical methods for encoding OR and fertility rely on the combination of tests, which cannot serve as a multi-functional platform with limited information from specific biofluids. Herein, metabolic fingerprinting of follicular fluid (MFFF) from follicles is performed, using particle-assisted laser desorption/ionization mass spectrometry (PALDI-MS) to encode OR and fertility. PALDI-MS allows efficient MFFF, showing fast speed (≈30 s), high sensitivity (≈60 fmol), and desirable reproducibility (coefficients of variation <15%). Further, machine learning of MFFF is applied to diagnose diminished OR (area under the curve of 0.929) and identify high-quality oocytes/embryos (p < 0.05) by a single PALDI-MS test. Meanwhile, metabolic biomarkers from MFFF are identified, which also determine oocyte/embryo quality (p < 0.05) from the sampling follicles toward fertility prediction in clinics. This approach offers a powerful platform in women's healthcare, not limited to OR and fertility.

Stabilizing Nitroxide Spin Labels for Structural and Conformational Studies of Biomolecules by Maleimide Treatment.

Nitroxide (NO) spin radicals are effective in characterizing structures, interactions and dynamics of biomolecules. The EPR applications in cell lysates or intracellular milieu require stable spin labels, but NO radicals are unstable in such conditions. We showed that the destabilization of NO radicals in cell lysates or even in cells is caused by NADPH/NADH related enzymes, but not by the commonly believed reducing reagents such as GSH. Maleimide stabilizes the NO radicals in the cell lysates by consumption of the NADPH/NADH that are essential for the enzymes involved in destabilizing NO radicals, instead of serving as the solo thiol scavenger. The maleimide treatment retains the crowding properties of the intracellular components and allows to perform long-time EPR measurements of NO labeled biomolecules close to the intracellular conditions. The strategy of maleimide treatment on cell lysates for the EPR applications has been demonstrated on double electron-electron resonance (DEER) measurements on a number of NO labeled protein samples. The method opens a broad application range for the NO labeled biomolecules by EPR in conditions that resemble the intracellular milieu.

Frequency swept pulses for the enhanced resolution of ENDOR spectra detecting on higher spin transitions of Gd(III).

Half-Integer High Spin (HIHS) systems with zero-field splitting (ZFS) parameters below 1 GHz are generally dominated by the spin |─1/2>→|+1/2 > central transition (CT). Accordingly, most pulsed Electron Paramagnetic Resonance (EPR) experiments are performed at this position for maximum sensitivity. However, in certain cases it can be desirable to detect higher spin transitions away from the CT in such systems. Here, we describe the use of frequency swept Wideband, Uniform Rate, Smooth Truncation (WURST) pulses for transferring spin population from the CT, and other transitions, of Gd(III) to the neighbouring higher spin transition |─3/2>→|─1/2 > at Q- and W-band frequencies. Specifically, we demonstrate this approach to enhance the sensitivity of 1H Mims Electron-Nuclear Double Resonance (ENDOR) measurements on two model Gd(III) aryl substituted 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (DO3A) complexes, focusing on transitions other than the CT. We show that an enhancement factor greater than 2 is obtained for both complexes at Q- and W-band frequencies by the application of two polarising pulses prior to the ENDOR sequence. This is in agreement with simulations of the spin dynamics of the system during WURST pulse excitation. The technique demonstrated here should allow more sensitive experiments to be measured away from the CT at higher operating temperatures, and be combined with any relevant pulse sequence.

GdIII -19 F Distance Measurements for Proteins in Cells by Electron-Nuclear Double Resonance.

Studies of protein structure and dynamics are usually carried out in dilute buffer solutions, conditions that differ significantly from the crowded environment in the cell. The double electron-electron resonance (DEER) technique can track proteins' conformations in the cell by providing distance distributions between two attached spin labels. This technique, however, cannot access distances below 1.8 nm. Here, we show that GdIII -19 F Mims electron-nuclear double resonance (ENDOR) measurements can cover part of this short range. Low temperature solution and in-cell ENDOR measurements, complemented with room temperature solution and in-cell GdIII -19 F PRE (paramagnetic relaxation enhancement) NMR measurements, were performed on fluorinated GB1 and ubiquitin (Ub), spin-labeled with rigid GdIII tags. The proteins were delivered into human cells via electroporation. The solution and in-cell derived GdIII -19 F distances were essentially identical and lie in the 1-1.5 nm range revealing that both, GB1 and Ub, retained their overall structure in the GdIII and 19 F regions in the cell.

Deciphering the mitochondrial genome of Juglans mandshurica (Juglandaceae).

Juglans mandshurica Maxim., 1856 is a second-class, protected, rare tree species of high economic and ecological value. We elucidated the complete mitochondrial (mt) genome of J. mandshurica using the Illumina Novaseq 6000 and Nanopore platforms. The complete sequences of 558,032 and 161,386 bp had an overall GC content of 45.0% and 45.3%, respectively, and 61 genes could be annotated, including 38 protein-coding, 20 tRNA, and 3 rRNA genes. The high-quality J. mandshurica mt genomic sequences presented in this study will serve as a useful resource for a range of genetic, functional, evolutionary, and comparative genomic studies on this species of the Juglandaceae family.

A phenomenographic study of Chinese primary school students' conceptions about technology.

Although there are some researches conducted about students' conceptions of technology, little research has been conducted to reveal the primary school students' conceptions concerning technology in China. This research investigated Chinese primary school students' (aged 9-12) conceptions of technology as regards their understanding of (a) the concept of technology, (b) the impact of technology on human life and nature, and (c) the relationship between technology and science. Phenomenography as the methodological framework was adopted for this study. A total of 63 primary school students were chosen as participants in the study to probe their conceptions about technology through picture/photo eliciting activities, and semi-structured, personal interviews in a website video format. It is found that the primary school students defined technology from diverse perspectives, including the dimensions of its attributes, production, operation and use, function, with most of them regarding technology as a double-edged sword. It is also found that they lack a comprehensive and rational understanding of the concept of technology and cannot understand the relationship between science and technology properly. This study contributes better to understanding primary school students' conceptions about technology in mainland China and beyond, thus providing an empirical basis for improving technology education policy, curriculum, instruction, and assessment in the future for China and other countries.

Stereospecific recognition of a chiral centre over multiple flexible covalent bonds by 19F-NMR.

High performance in chiral recognition by a reactive 19F-tag was demonstrated for a variety of enantiomers. The analytes with up to five flexible covalent bonds from the chiral center can be discriminated by a sensitive chiral reporter manifested in the 19F-NMR spectrum. Simultaneous identification of chiral amines in a mixture and high accuracy ee determination were achieved.