Cleavage Mode Research Articles

Pt/MgO catalysts intrinsically promoted by fast moving bed pyrolysis for hydrogenation properties

Elucidating the correlation between the geometric/electronic structure of the catalyst and its catalytic performance is of paramount importance. However, achieving precise manipulation over the geometric/electronic structure of the catalyst remains a formidable challenge. Here, we develop a fast moving pyrolysis bed (FMPB) strategy to finely regulate the geometry structure (Pt metal particle size and Pt-O coordination number (CN)) and electronic structure of the Pt/MgO catalyst. It is found that the hydrogen dissociation energy barrier is negatively related to the Pt atom electron density. The Pt1/MgO-600-N2 (600 and N2 represented the temperature and atmosphere under fast pyrolysis, respectively) with highest electron density exhibits the highest para-chloronitrobenzene (p-CNB) hydrogenation activity (66978 h−1), which is ∼220 times that of Pt nanoparticles (NPs, Pt NPs/MgO), ∼58 times that of Pt1/MgO-400-air, and ∼3 times that of Pt nanoclusters (NCs, Pt NCs/MgO). DFT calculations disclose that Pt1/MgO-600-N2 with highest Pt-5d center, which is more conducive to hydrogen dissociation. The transition of the H2 cleavage mode from homolytic (Pt NPs/MgO) to heterolytic (Pt1/MgO-600-N2) makes it more favorable for the hydrogenation of the polar nitro functional group, ensuring that substantial enhancement in its activity while preserving high selectivity in hydrogenation.

Recent Advances in the Linkers of Drug Conjugates.

Drug conjugates have emerged as a pivotal research focus in the field of targeted cancer therapy. They represent a widely explored prodrug strategy that significantly enhances the therapeutic index of drugs while minimizing side effects. The stability and selective cleavage of the linker within drug conjugates are critical for the therapeutic efficacy and targeted treatment achieved by these conjugates. In this review, we have categorized the linkers based on their cleavage mode and summarized the chemical properties, advantages, and limitations of various types of cleavable linkers. Particularly, examples have been provided to illustrate their specific potential for development.

Microstructure and properties of SLMed Ta-10W and rolled Ta-10W fiber laser welded joint

This study focused on the mechanical properties and microstructure of fiber laser-welded joints of Ta-10W alloy manufactured by selective laser melting (SLM) and rolled. In the SLMed base material side of the weld, columnar grains were formed along the weld, extending up to half of the weld width. The base material’s anisotropy influenced the subgrain morphology, and grain orientation changed after welding. When the building direction of the SLMed Ta-10W was perpendicular to the welding direction, slender columnar subgrains were prone to forming in the SLM side weld. In contrast, when the building direction was parallel to the welding direction, equiaxed subgrains tended to form in the weld. In the rolling base material side weld, mainly equiaxed grains were formed, with subgrain morphology and orientation randomly distributed. In the weld center, fine-grain zones of 10–20 μm, comprising fine grains of 2–5 μm diameter, were observed in all welds under study. Room-temperature tensile strengths of both welds were approximately 620 MPa, falling between the strengths of the two base materials. Their fracture surfaces displayed a mixed mode of cleavage and intergranular fracture. High-temperature strengths of rolled-SLMed joints varied with SLM directions X and Z, reaching 124.94 and 107.87 MPa, respectively, and exhibiting similar fracture characteristics dominated by intergranular fracture.

RNase H-sensitive multifunctional ASO-based constructs as promising tools for the treatment of multifactorial complex pathologies

Combined therapies play a key role in the fight against complex pathologies, such as cancer and related drug-resistance issues. This is particularly relevant in targeted therapies where inhibition of the drug target can be overcome by cross-activating complementary pathways. Unfortunately, the drug combinations approved to date –mostly based on small molecules– face several problems such as toxicity effects, which limit their clinical use. To address these issues, we have designed a new class of RNase H-sensitive construct (3ASO) that can be disassembled intracellularly upon cell entry, leading to the simultaneous release of three different therapeutic oligonucleotides (ONs), tackling each of them the mRNA of a different protein. Here, we used Escherichia coli RNase H1 as a model to study an unprecedented mode of recognition and cleavage, that is mainly dictated by the topology of our RNA·DNA-based hybrid construct. As a model system for our technology we have created 3ASO constructs designed to specifically inhibit the expression of HER2, Akt and Hsp27 in HER2+ breast cancer cells. These trifunctional ON tools displayed very low toxicity and good levels of antiproliferative activity in HER2+ breast cancer cells. The present study will be of great potential in the fight against complex pathologies involving multiple mRNA targets, as the proposed cleavable designs will allow the efficient single-dose administration of different ON drugs simultaneously.

Effect of laser energy density on cracking susceptibility and wear resistance of laser-clad tribaloy T-800 coatings on DD5 single-crystal alloys

In order to enhance the wear resistance of DD5 single-crystal alloys, Tribaloy T-800 wear-resistant coatings were prepared on their surfaces using laser-cladding technology. This study examines the effect of laser energy density on the cracking susceptibility and wear resistance of laser-clad Tribaloy T-800 coatings on DD5 single-crystal alloys. Three distinct laser energy densities (η1=33 J/mm², η2=50 J/mm², η3=60 J/mm²) were applied to create the coatings. The results show that the microstructures of the T-800 laser-clad coatings mainly consist of primary, coarsened, and spheroidized Laves phases, as well as Co-based solid solution and eutectic structures. The phases include Co3Mo2Si phase (Laves phase) and face-centered cubic Co-based solid solution. However, increasing laser energy density enhanced elemental diffusion at the heterogeneous joining interface of the DD5 substrate/T-800 coating, leading to higher Ni content in the coating. This resulted in a reduction in the tendency and content of Mo-rich Laves phase formation respective contents of 53.2 %, 49.2 %, and 47.5 %. Moreover, the decrease in the difference between laser cladding temperature and initial temperature, ∆T, led to reduced thermal stress at the interface, σ, contributing to a decrease in cracking susceptibility (a), with corresponding values of 0.16184, 0.00034, and 0.00022. Thermal expansion coefficients of materials in the cracked region near the interface, measured according to the CALPHAD method, Jmatpro software, and average EDS elemental content data at the crack edge, surpassed those of the corresponding DD5 substrate. Consequently, cracks in the coatings originated from stretching at the interface, with paths tending to cross Laves phase particles in a cleavage mode. The average microhardness of the coatings decreased due to reduced Laves phase content, with values of 783.4 HV0.5, 741.7 HV0.5, and 708.2 HV0.5, respectively, while the fatigue wear of T-800 coatings increased due to exacerbated wear damage from cracking defects. Specifically, average COFs were 0.659, 0.583, and 0.506, with corresponding mass losses of 7.1 mg, 3.4 mg, and 2.9 mg, respectively. The wear mechanisms observed encompassed fatigue wear, abrasive wear, and oxidative wear.

Highly selective oxidation of glucose to formic acid and exploring reaction pathways using continuous flow microreactors

The process of converting glucose into formic acid (FA) has been explored as a promising route for using biomass as a renewable feedstock for green chemical manufacturing. However, the most commonly used batch-tank reactor systems currently suffer from several drawbacks, including extended processing time, limited product selectivity, and high energy consumption, while the underlying reaction paths have been poorly understood. In this work, a continuous flow microchannel reactor was employed for the glucose conversion catalyzed by H5PV2Mo10O40 with O2 as an oxidant. The influence of various parameters on the conversion rate of glucose and the FA yield was characterized. Experimental results indicated that with a residence time of less than 3 min, the glucose was completely converted, and the highest FA yield reached 82.40 %. Extensive examination on the apparent by-products revealed that most of them acted as intermediates to produce FA through various pathways, including glyoxal, glyceraldehyde and glycolaldehyde as key intermediates for the oxidation of glucose to FA. Furthermore, the density functional theory (DFT) method was used to determine the bond energies of different C–C bond cleavage modes of substrate glucose and fructose produced by the isomerization of glucose. Experimentally, the conversion of three main intermediates and some other possible intermediates and their FA yield were measured with different residence time. It was also found that the CO2 was produced through the decarboxylation of α-hydroxy and α-carbonyl carboxylic acid compounds, while the aldehyde groups in the compounds were more likely converted to FA by the α-carbon bond cleavage. Finally, plausible reaction pathways were proposed for the process of glucose-to-FA catalyzed by HPA-2, providing useful guidance for the identification of side reaction pathways and further improvement of FA yield.

Unveiling novel insights into Bacillus velezensis 16B pectin lyase for improved fruit juice processing

Microbial pectinolytic enzymes are important in various industries, particularly food processing. This study focuses on uncovering insights into a novel pectin lyase, BvPelB, from Bacillus velezensis 16B, with the aim of enhancing fruit juice processing. The study examines the structural and functional characteristics of pectinolytic enzyme, underscoring the critical nature of substrate specificity and enzymatic reaction mechanisms. BvPelB was successfully expressed and purified, exhibiting robust activity under alkaline conditions and thermal stability. Structural analysis revealed similarities with other pectin lyases, despite limited sequence identity. Biochemical characterization showed BvPelB's preference for highly methylated pectins and its endo-acting mode of cleavage. Treatment with BvPelB significantly increased juice yield and clarity without generating excessive methanol, making it a promising candidate for fruit juice processing. Overall, this study provides valuable insights into the enzymatic properties of BvPelB and its potential industrial applications in improving fruit juice processing efficiency and quality.

Effect of Sn addition on mechanical, wear, and electrochemical properties of Ti-Al-Sn alloys

This study aims to investigate the effect of Sn content on the structural, mechanical, wear, and electrochemical properties of Ti-6Al-xSn (x = 3.5–17.5, wt%) alloys fabricated by powder metallurgy method. The results showed that the microhardness generally decreased with increasing Sn content, although there was an unusual increase in microhardness in the alloy with 10.5 wt% Sn. Depending on the Sn content, various phases such as α-Ti, Ti3Sn, and Ti3Al indicated complex phase formations. The flexural and tensile strengths increased up to 10.5 wt% Sn content, but the strengths reduced above this level. The maximum values for flexural and tensile strengths were obtained as 270 MPa and 125.8 MPa, respectively. With increasing Sn content, the fracture surfaces shifted from cleavage mode to mixed brittle and ductile failure modes. The wear tests were conducted in two different environments: dry and wet conditions. Considering dry sliding conditions, the lowest specific wear rate was obtained as 0.85 × 10−6 mm3/N·m in the alloy coded 3.5Sn at a sliding distance of 1500 m. On the other hand, the highest wear was measured as 2.89 × 10−6 mm3/N·m in the 17.5Sn coded sample at a sliding distance of 6000 m in wet conditions. The wear results demonstrated a relationship between mechanical properties and wear resistance, which was influenced by the existence of porosity. The Ti-6Al-7Sn alloy exhibited the best corrosion resistance with a 2.22 × 10−7 icorr value, while the one with Ti-6Al-17.5Sn alloy showed the worst performance with a 9.71 × 10−6 icorr value.

Revealing the Indispensable Role of the RFamide Functionality using a Novel Acid Labile Benzofuranone based Amine (ALBA) Linker

AbstractThe RFamide family of peptides represents an important class of GPCR ligand neuropeptides covering a wide range of biological functions. While many analogues of the highly conserved C‐terminal RFamide motif within this peptide class have been synthesized and their functional significance elucidated, additional exploration of the structure activity relationship is of value. We have developed a novel linker for solid phase peptide synthesis (SPPS) which is able to anchor amine functionalised compounds for further elaboration. The acid labile benzofuranone based amine (ALBA) linker (5‐(3‐aminopropylcarbamoyl)‐2‐[[tert‐butyl(diphenyl)silyl]oxymethyl]benzoic acid) is compatible with Fmoc based SPPS and has two cleavage modes. As a proof of concept, the ALBA linker was used to successfully synthesise a novel analogue of Kisspeptin 10, the natural ligand for GPCR54, whereby the natural RFamide motif was replaced with an RFamine. Biological evaluation of the amine‐containing analogue revealed that the group is not compatible with receptor activation.

Anaerobic biotransformation of hexachlorocyclohexane isomers in aqueous condition: Dual C[sbnd]Cl isotope fractionation and impact on microbial community compositions

Hexachlorocyclohexane (HCH) isomers are persistent organic pollutants (POPs) with high toxicity, lipid solubility, chemical stability. Despite the current ban on usage of Lindane, residual contamination cannot be ignored, and HCH are frequently detected in groundwater and threaten human health. Cultures capable of degrading α-HCH, β-HCH, γ-HCH, and δ-HCH individually have been enriched in anoxic aqueous conditions. Compound-Specific Isotope Analysis (CSIA) was applied to examine the transformation mechanisms of different HCH isomers by the four enrichment cultures. 16S rRNA sequencing techniques were employed to examine the community composition of the enrichment cultures and detect changes in these communities resulting from adding individual HCH isomers. The results indicated that the ability of the enrichment cultures for dichloroelimination of HCH isomers was inconsistent. During dichloroelimination, different bond cleavage mode of β- and δ-HCH led to distinct isotopic effects. HCH isomers had significant impact on the microbial community, while different microbial communities showed comparable isotopic effects during the transformation of a specific HCH isomer. In addition, bacteria in the phyla Proteobacteria and Firmicutes were proposed as the dominant dechlorinators. This study provides a novel perspective on the mode of bond cleavage during HCH dichloroelimination and the effect of HCH on microbial communities, which could potentially support the evaluation of HCH transformation by CSIA and their effects on the microecosystems of groundwater.

Amide C–N bonds activation by A new variant of bifunctional N-heterocyclic carbene

We report an organocatalyst that combines a triazolium N-heterocyclic carbene (NHC) with a squaramide as a hydrogen-bonding donor (HBD), which can effectively catalyze the atroposelective ring-opening of biaryl lactams via a unique amide C–N bond cleavage mode. The free carbene species attacks the amide carbonyl, forming an axially chiral acyl-azolium intermediate. Various axially chiral biaryl amines can be accessed by this methodology with up to 99% ee and 99% yield. By using mercaptan as a catalyst turnover agent, the resulting thioester synthon can be transformed into several interesting atropisomers. Both control experiments and theoretical calculations reveal the crucial role of the hybrid NHC-HBD skeleton, which activates the amide via H-bonding and brings it spatially close to the carbene centre. This discovery illustrates the potential of the NHC-HBD chimera and demonstrates a complementary strategy for amide bond activation and manipulation.

Understanding contact electrification via direct covalent bond cleavage of polymer chains for ultrahigh electrostatic charge density

This study unveils a direct covalent bond cleavage mode within polymer chains for a unified and enhanced understanding of both electrostatic charges and mechanoradicals generated via contact electrification for ultrahigh charge density.

Carotenoid Cleavage Dioxygenase 1 and Its Application for the Production of C13-Apocarotenoids in Microbial Cell Factories: A Review.

C13-apocarotenoids are naturally derived from the C9-C10 (C9'-C10') double-bond cleavage of carotenoids by carotenoid cleavage dioxygenases (CCDs). As high-value flavors and fragrances in the food and cosmetic industries, the sustainable production of C13-apocarotenoids is emerging in microbial cell factories by the carotenoid cleavage dioxygenase 1 (CCD1) subfamily. However, the commercialization of microbial-based C13-apocarotenoids is still limited by the poor performance of CCD1, which severely constrains its conversion efficiency from precursor carotenoids. This review focuses on the classification of CCDs and their cleavage modes for carotenoids to generate corresponding apocarotenoids. We then emphatically discuss the advances for C13-apocarotenoid biosynthesis in microbial cell factories with various strategies, including optimization of CCD1 expression, improvement of CCD1's catalytic activity and substrate specificity, strengthening of substrate channeling, and development of oleaginous microbial hosts, which have been verified to increase the conversion rate from carotenoids. Lastly, the current challenges and future directions will be discussed to enhance CCDs' application for C13-apocarotenoids biomanufacturing.

Screening of organophosphorus flame retardant residues in rice by QuEChERS-gas chromatography-quadrupole time-of-flight mass spectrometry

Organophosphorus flame retardants (OPFRs) have emerged as good alternatives to brominated flame retardants, the use of which is globally restricted. In this study, a screening method based on QuEChERS-gas chromatography-quadrupole time-of-flight mass spectrometry (GC-Q-TOF/MS) was established for the determination of 21 OPFRs in rice. First, full scan (scanning range, m/z 50-450) was performed with a mixed standard solution of the 21 OPFRs (0.1 μg/g) by GC-Q-TOF/MS. The fragmentation pathways of these OPFRs were then investigated to explore their cleavage fragments, the interrelationships among fragments, and the possible cleavage modes of alkylated, chlorinated, and aromatic OPFRs. The retention times, isotopic abundance ratios, and molecular formulas of the characteristic fragments as well as the exact mass of the compounds were obtained to establish a mass spectral library of the OPFRs. Rice samples were extracted and purified by the QuEChERS method, and 0.5% formate acetonitrile solution was used as the extraction solvent; 4 g of magnesium sulfate, 1 g of sodium chloride, 0.5 g of disodium hydrogen citrate, and 1 g of sodium citrate as the extraction-salt combination; and 50 mg of primary secondary amine (PSA), 50 mg of octadecylsilane (C18), and 150 mg of magnesium sulfate as the purification materials. The chromatographic separation of the 21 OPFRs was completed within 16 min under optimized temperature program conditions on the DB-5MS UI column. The screening parameters were optimized, and a full scan of the samples was performed under the following conditions: number of characteristic fragment ions ≥2; accurate mass window=±2×10-5 (±20 ppm); retention time deviation=±0.2 min, and ion abundance deviation<20%. The developed method was applied to the screening 21 OPFRs in the samples. The results indicated that the matrix interference was greatly reduced by decreasing the extraction accurate mass window, thereby improving the signal-to-noise ratio of the analytes. The targets were extracted from the matrix interference and background noise using deconvolution software, which improved the match between the target compounds and the mass spectral library. The detection rates of alkyl and aromatic OPFRs increased by 22% and 25%, respectively, when the spiking level was increased from 2 to 10 ng/g. Among the chlorinated OPFRs, only tris(2-chloroisopropyl) phosphate (TCIPP) was not detected at a spiking level of 2 ng/g, indicating that chlorinated OPFRs could be identified even at low concentrations. The characteristic ions of the detected compounds matched those of the home-made mass spectral library well, indicating that the practical application of the home-made mass spectral library. The established screening method was applied in the determination of OPFRs in rice samples from different regions in China. A total of 11 OPFRs were detected, among which trimethyl phosphate (TMP), tri-iso-butyl phosphate (TiBP), and tris(3,5-dimethylphenyl) phosphate (T35DMPP) had the highest detection rates. These results indicate that these three OPFRs are widely used and can easily come into contact with rice samples through various routes. Differences in the types of OPFRs detected in the actual samples may be related to the types of OPFRs produced in local factories. OPFRs can be detected in rice samples by the developed GC-Q-TOF/MS screening method, which is helpful for the identification of OPFRs in complex matrix samples.

Micro-mechanical behavior of lamellar structured Ti6Al4V alloy upon compression via experimental and crystal plasticity study

The micro-mechanical behavior of lamellar structured Ti6Al4V alloy to a small compressional strain of 4.5% was studied. Strain and stress intends to localize along grain boundaries (GBs), triple points (TPs) as well as grain interiors (GIs). The maximum strain and stress is found at some GB-TPs with soft and grain clustering mostly owing to their strong strain incompatibility. Their heterogeneous distribution is highly related to individual crystallographic orientation, their size, shape and grain-grain interactions. The local dislocation behavior forms ledges along with Geometrically necessary dislocations (GNDs) to accomodate strain incompatibility. EBSD and crystal plasticity (CP) simulation disclosed some long range meso-bands (about 45° to loading direction) which crosse multi-grains and some mini-bands within grain interiors (GIs) reflecting a concentrated strain behavior and ductile nature of the Ti6Al4V material. Prismatic slip dominates Ti6Al4V lattice (mainly from surface dislocation activation) determined by its low critical resolved shear stress (CRSS) which is away from some findings of literature. Dislocation is found commenced from some high angle GBs (HAGBs) and extened into GI which can pass through GBs of both low (LA) and high angles given their slip plane coherency. The substructures (α-lamellae) separated by LAGBs within α-colonies, have no significant effect to dislocation movement. Fatigue failure can be inferred from the early stage micro-mechanical behavior through accumulated plastic strain and strong strain incompatability. Fractography reaveals fatigue failure from surface, sub-surface, shearing, cleavage and intergranular modes are presumed highly related to surface defects, compressional residual stress gradient, easy prismatic slip and soft and hard GBs. Multiple crack origins from such combinations are deemed for reduced fatigue life of shot peened samples regardless of the surface compressional residual stress being generated.

Activation Mechanism of CcGSDMEb-1/2 and Regulation for Bacterial Clearance in Common Carp (Cyprinus carpio).

Gasdermin E (GSDME), to date, is considered the only direct executor of the pyroptosis process in teleost and plays an important role in innate immunity. In common carp (Cyprinus carpio), there contains two pairs of GSDME (GSDMEa/a-like and GSDMEb-1/2), and the pyroptotic function and regulation mechanism of GSDME still remain unclear. In this study, we identified two GSDMEb genes of common carp (CcGSDMEb-1/2), which contain a conserved N-terminal pore-forming domain, C-terminal autoinhibitory domain, and a flexible and pliable hinge region. We investigated the function and mechanism of CcGSDMEb-1/2 in association with inflammatory and apoptotic caspases in Epithelioma papulosum cyprinid cells and discovered that only CcCaspase-1b could cleave CcGSDMEb-1/2 through recognizing the sites 244FEVD247 and 244FEAD247 in the linker region, respectively. CcGSDMEb-1/2 exerted toxicity to human embryonic kidney 293T cells and bactericidal activity through its N-terminal domain. Interestingly, after i.p. infection by Aeromonas hydrophila, we found that CcGSDMEb-1/2 were upregulated in immune organs (head kidney and spleen) at the early stage of infection, but downregulated in mucosal immune tissues (gill and skin). After CcGSDMEb-1/2 were knocked down and overexpressed invivo and invitro, respectively, we found that CcGSDMEb-1/2 could govern the secretion of CcIL-1β and regulate the bacterial clearance after A. hydrophila challenge. Taken together, in this study, it was demonstrated that the cleavage mode of CcGSDMEb-1/2 in common carp was obviously different from that in other species and played an important role in CcIL-1β secretion and bacterial clearance.

Effects of Temperatures of Rolling and Annealing on Microstructures and Tensile Properties of Low Carbon Ferritic Low Density Steels

The microstructural modification and the effect of cold/warm rolling and annealing on tensile properties of ferritic low density steels containing different amounts of carbon (0.0035 mass%, Steel 1 and 0.04 mass%, Steel 2) and aluminium (6.8 mass%, Steel 1 and 9.7 mass%, Steel 2) were investigated with respect to amount of ferrite, grain size and formation of Fe3Al intermetallic. The Steel 1 was deformed by cold rolling at room temperature and Steel 2 was deformed through warm rolling at 250°C to avoid prior cracks formation. After rolling, samples of Steels 1 and 2 were annealed at 900°C for 5 minutes. The yield strength, ultimate tensile strength and ductility increase while yield ratio decreases with annealing. This is due to formation of Fe3Al intermetallic and reduction of ferrite grain size. Due to high interstitial Carbon in Steel 2, yield point phenomenon was observed which may reduce the formability of the steel. The cracks started during tensile test at the ferrite grains and ferrite grain boundaries and the fracture took place in the quasi cleavage mode in Steels 1 and 2. The grain refinement and the microstructural features due to rolling and annealing are accountable for the good combination of strength and ductility of the both steels.

Superior strength-ductility synergy of high potassium-doped tungsten rods with large swaging deformation

The high ductile-to-brittle transition temperature (DBTT) is a key factor limiting the use of tungsten (W) - based materials in future nuclear fusion reactors. To overcome this challenge, and to obtain W alloys with improved mechanical properties without sacrificing substantial thermal conductivity, a large-sized W rod with a total weight of 42 kg and with 96 ppm doped potassium (K) was fabricated through a powder metallurgy mass production route. Then high-temperature swaging processes were conducted to produce a rod with large plastic deformation of 94.7% (log. Strain of 2.95). The swaged rod showed good low-temperature ductility and high strength simultaneously. At 50 °C, the AKS-W rod fractured in brittle cleavage mode. The fracture changed to a mixture of brittle and ductile at 100 °C, indicating a DBTT of 50 °C - 100 °C. This value was lower than many other reported in pure W and K-doped alloys. The swaged W rod exhibited a high strength of larger than 1.0 GPa up to 100 °C, with good conductivity at low temperatures. The maximum total elongation of 30.24% was obtained at 200 °C. The superior strength-ductility synergy of AKS-W rod was observed to be attributed to its unique microstructure and K bubbles morphology, which evolved during severe hot plastic deformation.

Comprehensive characterization of narirutin metabolites in vitro and in vivo based on Analogous-Core recursion analysis strategy using UHPLC-Q-Exactive Orbitrap MS/MS

Narirutin, extracted from the dried ripe pericarp of Rutaceae orange and its cultivated varieties, is a dihydroflavone compound with various biological activities and pharmacological effects. So far as we know, the metabolism profiling of narirutin has been insufficient until now. In the present study, an efficient method was employed to perform rapid analysis and identification of narirutin metabolites by using ultra-high performance liquid chromatography quadrupole exactive orbitrap MS/MS (UHPLC-Q-Exactive Orbitrap MS/MS) combined with an analogous core recursion (ACR) analysis strategy. Firstly, according to the basic core structure of the dihydroflavonoid, the cleavage mode and fragmentation ions of narirutin were summarized. Secondly, based on the difference of the substituent groups, the fragment ions of narirutin were preliminarily inferred and verified by the secondary mass spectra of its standard compound. Thirdly, the fragment ions of narirutin in positive and negative ion modes were summarized to provide a basis for the identification of metabolites. Fourthly, candidate metabolites were accurately and tentatively identified according to the cleavage law of mass spectrometry, literature reports, comparison of reference substances, and especially the diagnostic fragment ion clusters (DFICs) and characteristic suggestive ions (CSIs) deduced preliminarily. Finally, a total of 46 metabolites (30 in vivo and 19 in vitro), including prototype drugs were identified based on the ACR analysis strategy, chromatographic retention behavior of metabolites, corresponding ClogP value and accurate molecular weight. Among them, 22 metabolites were discovered in rats plasma, 12 in urine, 4 in liver tissue, 19 in liver microsomes, respectively. Additionally, metabolites relative contents were also studied by extracted ion chromatography (EIC) method. Our result also illustrated that narirutin primarily underwent glucuronidation, sulfation, glutathione binding, deglycosylation, oxidation, reduction, methylation, hydroxylation, ring-opening and their composite reactions. A novel strategy was constructed to comprehensively elucidate the biotransformation pathways of narirutin in vitro and in vivo, and a systematic metabolic profile of narirutin was generated. This study provided a great reference for further understanding of the biotransformation pathways and guiding for clinical application of narirutin.

Patient- and cycle-specific factors affecting the outcome of frozen–thawed embryo transfers

PurposeThis study attempted at identifying the main parameters influencing the outcome of frozen embryo transfers.MethodsThis is a single-center retrospective cohort study of 830 frozen-embryo-transfer cycles performed at a German university hospital from January 2012 to December 2016. Main outcome parameters were the clinical pregnancy and live birth rate. Twelve patient- and cycle-dependent factors were analyzed in terms of their influence on the outcome of frozen embryo transfers. Multivariate logistic regression analysis was used for the modelling of the dependency of the different parameters on outcomes.ResultsThe clinical pregnancy rate in our study was 25.5%, the live birth rate was 16.1% with an average maternal age of 34.2 years at the time of the oocyte retrieval. In the univariate analysis age, number of transferred embryos, blastocyst versus cleavage stage transfer, embryo quality and mode of endometrial preparation affected the birth rate significantly. The birth rate after artificial endometrial preparation was significantly lower than the birth rate after transfers in modified natural cycles (12.8 versus 20.6% with p = 0.031). The multivariate logistic regression analysis showed a significant independent influence of age, number of transferred embryos, culture duration and mode of endometrial preparation on the frozen embryo transfer success rates. Body mass index, nicotine abuse, a history of PCO syndrome or endometriosis and the co-transfer of a second poor-quality embryo to a good-quality embryo appeared to be irrelevant for the outcome in our collective.ConclusionAge, number of transferred embryos, embryo culture duration and the mode of endometrial preparation are independent predictive factors of frozen embryo transfer outcomes.