Concentration Range Research Articles

Overview of Liquid Sample Preparation Techniques for Analysis, Using Metal-Organic Frameworks as Sorbents

The preparation of samples for instrumental analysis is the most essential and time-consuming stage of the entire analytical process; it also has the greatest impact on the analysis results. Concentrating the sample, changing its matrix, and removing interferents are often necessary. Techniques for preparing samples for analysis are constantly being developed and modified to meet new challenges, facilitate work, and enable the determination of analytes in the most comprehensive concentration range possible. This paper focuses on using metal-organic frameworks (MOFs) as sorbents in the most popular techniques for preparing liquid samples for analysis, based on liquid-solid extraction. An increase in interest in MOFs-type materials has been observed for about 20 years, mainly due to their sorption properties, resulting, among others, from the high specific surface area, tunable pore size, and the theoretically wide possibility of their modification. This paper presents certain advantages and disadvantages of the most popular sample preparation techniques based on liquid-solid extraction, the newest trends in the application of MOFs as sorbents in those techniques, and, most importantly, presents the reader with a summary, which a specific technique and MOF for the desired application. To make a tailor-made and well-informed choice as to the extraction technique.

Combining capillary electrophoresis and chemometric tools for the straightforward determination of imidazolinone herbicides in plant-based milks.

Highly polar herbicides, such as imidazolinones, are used for weed control to increase agricultural productivity and crop quality. However, their misapplication can lead to residues in ready-to-eat food with a potential health risk for consumers. Hence, the fast determination of these herbicides is necessary for timely action. In this work, an eco-friendly method based on capillary zone electrophoresis combined with chemometrics was used for the determination of imazapyr and imazamox in vegetable-based beverages such as soy and quinoa milk. The analytical strategy consisted of only three steps: (i) protein precipitation prior to sample injection (ii) data pre-processing to reduce the background and make corrections on electrophoretic times shift, and (iii) resolution of fully overlapped capillary electrophoresis (CE) peaks by the well-known partial least square (PLS) algorithm, which extracts quantitative information attributed to the analytes. The method was successfully applied in the concentration range between 1.00 and 100 μg L-1 with coefficient of determination of the calibration (R2 cal) and prediction (R2 pred) > 0.90, residual prediction deviation of calibration (RPDcal) and of prediction (RPDpred) > 3, and relative error of prediction (REP) > 11 in the analyzed sample matrices, in the three built methods (quinoa samples, soy samples, and joint quinoa and soy samples). The proposed methodology offers a simple and quick alternative for determining imidazolinones at trace concentrations in vegetable beverages, such as quinoa and soy milk, without complex sample preparation. The results were consistent with those obtained using more complex techniques, confirming the applicability of this method. © 2024 Society of Chemical Industry.

Diffusion coefficients of Al<sub>2</sub>Cl<sub>7</sub><sup>–</sup> in low temperature chloroaluminate melt based on triethylamine hydrochloride

With the growing demand for renewable energy sources, much of the research in the battery industry is focused on creating safe and high-capacity energy storage systems that can handle high current loads using inexpensive and readily available materials. The aluminum-ion batteries (AIB) are considered as one of the most promising systems. Such materials as aluminum metal, carbon materials and chloroaluminate ionic liquids are used as anode, cathode and electrolyte, respectively. A low-temperature chloroaluminate melt based on triethylamine hydrochloride (Et3NHCl) is promising and inexpensive electrolytes for AIBs. This melt has the ability to reversibly precipitate/dissolve aluminum metal due to the presence of the Al2Cl7– ion in it. However, the diffusion of Al2Cl7– ions in the Et3NHCl–AlCl3 system has not been studied previously. In the presented work, the concentration dependence of the diffusion coefficients of the Al2Cl7– anion was studied using chronopotentiometry in the concentration range N = 1.3–1.95 (where N is the molar ratio of aluminum chloride to organic salt). It was shown that diffusion coefficients increase with aluminum chloride content growth in the studied melt: from 1.71·10–7 (N = 1.3) to 4.50·10–7 cm2·s–1 (N = 1.95). This behavior can be caused by the viscosity decrease of the melts with Al2Cl7– concentration growth. Based on the obtained results it can be concluded that Et3NHCl–AlCl3 with N = 1.95 is the most suitable electrolyte for AIB. Moreover, it was established that the electrochemical reduction of the Al2Cl7– on the surface of the aluminum electrode is complicated by the nucleation process, which has the lowest overvoltage at N = 1.95.

Experimental and Theoretical Comparison and Analysis of Surface-Enhanced Raman Scattering Substrates with Different Morphologies

The following research paper concerns the analysis and characterisation of commercially available surface-enhanced Raman scattering (SERS) substrates. SERS has long been a potentially very powerful method with a great deal of interest around it; however, there are still many obstacles which do not allow SERS to be easily applied to real-world detection and analysis problems. As such, research around the various types of substrates is ongoing, in the hope of streamlining and improving the Raman enhancement mechanism. Scanning electron microscope images were obtained for each of the three substrates, and their features and scales were described. Enhanced Raman spectra for Rhodamine B were obtained for a range of concentrations using each of the three substrates, and, in addition, surface enhancement maps are presented. Enhancement factors were calculated for the 1358 cm−1 peak of Rhodamine B. Complementing the experimental work, theoretical FEM modelling in COMSOL Multiphysics was performed, with the resulting calculations yielding an enhancement prediction adequately accurate to the real substrates.

Enzymeless Gabapentin Sensor Based on Prussian Blue-modified Indium Tin Oxide Electrodes for Sensing Gabapentin in Capsules

Background: In this study, we reported on developing a susceptible, accurate, simple, and economical electrochemical sensor for gabapentin determination in capsules. Methods: The ITO electrode was modified with a layer of Prussian blue nanoparticles and then used as the working electrode. Gabapentin was extracted from commercial capsules, and a series of concentrations of gabapentin were prepared for studying the efficacy of the proposed sensor. The electrochemical measurements were performed using cyclic voltammetry and square wave voltammetry techniques. Results: The sensitivity and selectivity of the developed electrode toward gabapentin in different interferences, including citric acid, glucose, and urea, were investigated. The modified electrode showed detection and quantification limits of 31.58 and 94.74 nM, respectively, over a dynamic range of concentrations from 100 nM to 3 μM. Conclusion: The proposed sensor displayed a high sensitivity and selectivity for monitoring gabapentin in pharmaceutical drugs without a noticeable interference. Hence, the modified electrodes are great candidates for gabapentin routine analysis.

Synthesis of a novel water-soluble pyridine dicarboxylate and its application in fluorescence cell imaging

Abstract A novel water-soluble substituted pyridine dicarboxylate containing a quaternary ammonium ion with potential applications in fluorescence cell imaging was synthesized and characterized. Remarkably, this compound exhibited water solubility in the absence of additional solubilizers, enabling direct dissolution in phosphate-buffered saline for cell studies. No obvious cytotoxicity was observed in 4T1 cells (mouse breast cancer cells) within the concentration range of 0.2–25 μmol L−1, with a cell survival rate above 89%. Furthermore, the compound exhibited a maximum two-photon absorption cross-section of 86 GM at an excitation wavelength of 780 nm, demonstrating high cell permeability, effective distribution in the cytoplasm, and preferential targeting of organelles. Single- and two-photon fluorescence imaging of cells revealed a distinctive blue emission and strong bright green emission, respectively. The newly synthesized substituted pyridine dicarboxylate exhibited low cytotoxicity and strong fluorescence imaging properties, demonstrating its potential in cell imaging applications.

Processing of Angelica (Angelica sylvestris L.) into a functional jam with addition of carob and cinnamon extracts: Evaluation of sensorial, physicochemical, and nutritional characteristics and in vitro bioaccessibility of phenolics

AbstractA traditional Angelica jam has been produced from stems of Angelica sylvestris L. growing at the foot of Mount Uludag in Bursa for many years. The aim of this study was to develop new functional formulations of Angelica jam by adding carob and cinnamon extracts, and to evaluate the effect of jam processing and the extracts' addition on the sensory attributes, physicochemical and nutritional characteristics of Angelica jams as well as in vitro bioavailability of phenolics. The main physicochemical properties of the jams including total water‐soluble dry matter (Brix value), pH, invert sugar content, total dietary fiber content, and 5‐(hydroxymethyl) furfural (HMF) ranged between 71.80–72.70 °Bx, 3.65–3.91, 39.30%–49.60%, 0.70–0.90 g/100 g, and 91.00–105.50 mg/kg, respectively. The most abundant minerals were potassium (K), calcium (Ca), magnesium (Mg), phosphorus (P), and iron (Fe) within a concentration range of 80.49–388.67 mg/kg, 111.10–135.00 mg/kg, 24.00–43.28 mg/kg, 7.57–28.06 mg/kg, and 0.52–1.14 mg/kg, respectively. Sensory analysis revealed that general acceptability of Angelica jams in a 9‐point hedonic scale was above 7. The highest antioxidant capacity values of Angelica jam and its functional forms fortified with carob and cinnamon extracts were obtained as 96.68 ± 11.30 mg TE/100 g DM, 248.49 ± 17.78 mg TE/100 g DM, and 193.11 ± 16.06 mg TE/100 g DM, respectively, with the ABTS (2,2′‐azino‐bis‐3‐ethylbenzothiazoline‐6‐sulfonic acid) method. It was observed that the main phenolic compound of the jams was caffeic acid. Depending on the type of extract added into the formulations, trans‐cinnamic acid and gallic acid (GA) became predominant phenolics. Total antioxidant capacity (TAC) of Angelica sylvestris stem decreased by 72%–85% with the heat treatment applied during jam processing. While total phenolic content (TPC) and total antioxidant capacity (measured by the DPPH (1,1‐diphenyl‐2‐picrylhydrazyl) method) increased as a result of intestinal digestion of the jam, it was observed that bioaccessibility of most of the phenolic compounds decreased after intestinal digestion of the jams.

Wide angle wide band polarization insensitive metamaterial absorber for C, X and Ku band application with hexagonal packaging

Abstract In this paper wide angle wide band polarization insensitive Metamaterial absorber (MA) has been proposed. The proposed unit cell structure consists of hexagonal concentric ring along with hexagonal packing. The structure is fabricated on FR4 substrate. The advantage of hexagonal packing is that it covers less area as compared to square packing. The unit cell structure is scaled w.r.t hexagonal ring and resistance of the substrate. The absorptivity achieved range from 6.54 to 14.85 GHz having Bandwidth (BW) of 8.31 GHz. The metamaterial behaviour of the structure is proven by plotting real and imaginary pat of permittivity and permeability. Absorption mechanism is shown by plotting surface current distribution at the top and bottom of the surface. The proposed MA structure is analysed for normal and oblique incidence. From the normal incidence it was found that structure has wide angle polarization insensitive. The absorptivity of the fabricated structure is measured inside the anechoic chamber. The simulated and measured plot is compared and found that both the results are very close to each other. At last, the proposed and already reported MAs are compared and from the observation it was found that proposed unit cell have larger BW compact in size, polarization insensitive and have hexagonal packing. The proposed MA covers partial C band, full X band and partial Ku band. The Proposed MA found practical applications for satellite communication, Wi-Fi devices, cordless telephone, military, air traffic control, defence tracking, vehicle speed detection.

Statistical properties of circular and rectangular multi-sinc Schell-model beams propagating in uniaxial crystals

With the extended Huygens–Fresnel principle, we derive the expressions for the spectral intensity, coherence, and effective beam width of circular and rectangular multi-sinc Schell-model (MSSM) beams propagating through uniaxial crystals. Numerical simulations are employed to extensively explore how beam and crystal parameters modulate the optical field. The results reveal that the propagating field exhibits multiple ring-shaped and array-like intensity distributions, with adjustable features such as the number of concentric rings, central brightness, array dimensions, and the morphology and diversity of sub-beams. Additionally, the spectral coherence displays an oscillatory distribution that evolves into a Gaussian distribution as the transmission distance increases. The anisotropy of uniaxial crystals not only influences the morphology of intensity distribution but also affects the evolution rate of coherence and the expansion rate of effective beam width. Our work contributes to optimizing beam propagation through uniaxial crystals, potentially benefiting precision optical systems in laser technology.

A novel sustainable and ecofriendly UV-Spectrophotometric method for the determination of Naringenin in bulk and vaginal niosomal nanoformulation

Naringenin, a flavonoid found in several fruits like oranges, grapefruit, and bergamot, exhibits a wide range of biological effects. These include antidiabetic, antidepressant, antiatherogenic, antitumor, immunomodulatory, anti-inflammatory, hypolipidemic, antioxidant, peroxisome proliferator-activated receptors (PPARs) activation, hepatoprotective properties, memory enhancement and DNA protective properties. The aim of this current study is to develop a simple and precise UV spectrophotometric technique for measuring Naringenin Active Pharmaceutical Ingredient (API) in bulk and vaginal niosomal nanoformulation using PBS (Phosphate buffer solution) pH 4.5. The absorption peak of Naringenin was identified at 287 nm, and it adhered to Beer's law within the concentration range of 2 to 14 µg/ml. The calibration curve demonstrates a linear relationship between absorbance and concentration within the range of 2 to 14 µg/ml. The determined limit of detection and limit of quantification were found to be 0.587672µg/mL and 1.780824µg/mL, respectively. The validity of the method was assessed for repeatability, accuracy and precision. The results obtained indicated minimal intraday and interday variation. The excipients in the nanoformulation did not interfere the analysis. The developed analytical UV spectrophotometric method is simple, rapid and consistent, making it suitable for estimating the drug in both bulk and nanoformulation.

Machine learning-aided quantitative detection of two mixed antibiotics in a narrow concentration range based on oxygen incorporation-induced 3D SERS substrates

Amoxicillin (AMO) and ciprofloxacin (CIP) as frequently-used antibiotics are often simultaneously taken for anti-infection to protect pig and poultry production, while their effective therapeutic window is narrow. How to quantitatively detect the two antibiotics mixed in a narrow concentration range is essential to ensure their treatment efficacy and food safety. In this study, quantitative detection of AMO and CIP mixed in animal flesh in one order of magnitude concentration range was performed using a triple SERS signal amplification sensor combined with machine learning. The SERS sensor based on oxygen incorporation (Oi)-induced 3D NiO nanoflowers (NFs) coated with Ag nanoparticles included 3D hot spot effect from strong internal electromagnetic couple in NiO NFs, the Oi effect of NiO and synergistic charge transfer effect of between NiO and Ag. Based on triple enhancement effects, sensitive SERS detection of AMO and CIP was made with the limits of detection of 1 nM and 100 nM. Through the use of machine learning techniques like principal component analysis and partial least square regression, qualitative and quantitative detection of AMO and CIP in their mixture from 1.33 μM to 8.69 μM was successfully achieved, where the average proportion of absolute prediction error (p ≤ 0.15) for concentration was 98.06 %.

Methyl Jasmonate (MeJA) Promotes the Self-Pollen Tube Growth of Camellia oleifera by Regulating Lignin Biosynthesis

Self-incompatibility (SI) poses a significant reproductive barrier, severely impacting the yield, quality, and economic value of Camellia oleifera. In this study, methyl jasmonate (MeJA) was employed as an exogenous stimulus to alleviate SI in C. oleifera. The research findings revealed that an exogenous dose of 1000 μmol·L−1 MeJA enhanced the germination and tube growth of C. oleifera self-pollen and greatly improved ovule penetration (18.75%) and fertilization (15.81%), ultimately increasing fruit setting (18.67%). It was discovered by transcriptome analysis that the key genes (CAD, C4H) involved in the lignin production process exhibited elevated expression levels in self-pistils treated with MeJA. Further analysis showed that the lignin concentration in the MeJA-treated pistils was 31.70% higher compared with the control group. As verified by pollen germination assays in vitro, lignin in the appropriate concentration range could promote pollen tube growth. Gene expression network analysis indicated that transcription factor bHLH may be pivotal in regulating lignin biosynthesis in response to MeJA, which in turn affects pollen tubes. Further transient knockdown of bHLH (Co_33962) confirmed its important role in C. oleifera pollen tube growth. In summary, the application of MeJA resulted in the stimulation of self-pollen tube elongation and enhanced fruit setting in C. oleifera, which could be associated with the differential change in genes related to lignin synthesis and the increased lignin content.

Determination of the optimal dose and dosing strategy for effective L-menthol oral rinsing during exercise in hot environments.

This multi-study programme investigated the optimal concentration of L-menthol delivered as an oral mouth rinse to modulate thermo-behaviour during exercise in a hot environment (35°C). In study 1, 38 participants completed a survey to establish an effective and tolerable range of L-menthol concentration. 31 participants completed an RPE-protocol examining 1. the dose-response effect of L-menthol mouth rinse on exercise performance (n = 16) and 2. the temporal effectiveness of administering L-menthol in an incremental and decremental dosing pattern (n = 15). Power output, heart rate, body core temperature and thermal sensation were reported throughout. The optimal menthol concentration for peak power was between 0.01 and 0.1% (~ 6% increase, P < 0.05) and 0.5% (~ 9% increase, P < 0.05) with respect to control. Work completed was increased at 0.01% (~ 5%, P < 0.05), at 0.1% (~ 3%, P < 0.05) and had a detrimental effect at 0.5% (- 10% decrease, P < 0.05). There were no differences between an ascending dose protocol (0.01 to 0.5%), descending dose protocol (0.5-0.01%) or a constant 0.01% dose protocol. There were no reported differences in body core temperature or heart rate across trials (P > 0.05). The optimal dose of L-menthol when delivered via oral rinsing is between 0.01 and 0.1%. At lower concentrations, L-menthol appears to be less effective and at higher concentrations (> 0.5%) L-menthol appears to elicit greater irritation and may not positively modulate thermo-behaviour during exercise in a hot environment.

8530 Characterizing the Genomic Effects of Low-Dose Estrogen in Breast Cancer Cells

Abstract Disclosure: H. Kim: None. T.S. Nandu: None. W.L. Kraus: None. Estrogens are steroid hormones that play a key role in a wide range of physiological and pathological processes. The predominant nuclear receptor for estrogens, estrogen receptor-alpha (ERɑ), functions primarily as a nuclear transcription factor (TF) through ligand-dependent activation by 17β-estradiol (E2), the major naturally-occurring estrogen. The physiological levels of E2 are regulated by production, sequestration, and degradation, which can limit the amount of bioavailable E2. However, many studies examining the genomic effects of E2-regulated signaling in cell-based assays used supraphysiological levels of hormone. While this has allowed us to understand the extremes of E2 signaling, it limits our ability to examine cellular functions which operate at lower hormone concentrations. The genomic actions of ligand-bound ERɑ are mediated through transcriptional enhancer formation and function. Alterations in protein and DNA components dictate different enhancer molecular subtypes that specify distinct regulatory mechanisms and downstream cellular phenotypes. How the amount of available hormone affects these genomic processes is unknown. In order to understand the genomic effects of physiological low-dose levels of E2, we have treated MCF-7 ERɑ-positive human breast cancer cells with a range of E2 concentrations and examined the global regulation of gene expression using a multi-omics approach (RNA-seq, ERɑ ChIP-seq, H3K27ac ChIP-seq, PRO-seq, ATAC-seq). Interestingly, we identified gene sets that are preferentially expressed maximally at picomolar or nanomolar concentrations. We are using these genes sets to explore the mechanisms of estrogen-regulated gene expression at physiologically relevant of E2 concentrations. Analysis of nascent RNA transcription using PRO-seq indicates regulation at the transcriptional level. Preliminary ERɑ chromatin binding assays show that while many loci require high levels of E2 for maximum ERɑ binding, others show maximum ERɑ binding at lower doses of E2. Further analyses show distinct enhancer features, such as chromatin accessibility and H3K27ac enrichment, may play a role in determining the response to E2 dosage. We are now determining the molecular mechanisms of dosage sensitivity using a multipronged approach integrating genomics, molecular biology, and cell-based assays. With these studies, we hope to understand a long overlooked physiological aspect of E2 with a comprehensive and global analysis of signal-dependent genomic responses. Presentation: 6/3/2024

9273 Characterizing the Genomic Effects of Low-Dose Estrogen in Breast Cancer Cells

Abstract Disclosure: H. Kim: None. T.S. Nandu: None. W.L. Kraus: None. Estrogens are steroid hormones that play a key role in a wide range of physiological and pathological processes. The predominant nuclear receptor for estrogens, estrogen receptor-alpha (ERɑ), functions primarily as a nuclear transcription factor (TF) through ligand-dependent activation by 17β-estradiol (E2), the major naturally-occurring estrogen. The physiological levels of E2 are regulated by production, sequestration, and degradation, which can limit the amount of bioavailable E2. However, many studies examining the genomic effects of E2-regulated signaling in cell-based assays used supraphysiological levels of hormone. While this has allowed us to understand the extremes of E2 signaling, it limits our ability to examine cellular functions which operate at lower hormone concentrations. The genomic actions of ligand-bound ERɑ are mediated through transcriptional enhancer formation and function. Alterations in protein and DNA components dictate different enhancer molecular subtypes that specify distinct regulatory mechanisms and downstream cellular phenotypes. How the amount of available hormone affects these genomic processes is unknown. In order to understand the genomic effects of physiological low-dose levels of E2, we have treated MCF-7 ERɑ-positive human breast cancer cells with a range of E2 concentrations and examined the global regulation of gene expression using a multi-omics approach (RNA-seq, ERɑ ChIP-seq, H3K27ac ChIP-seq, PRO-seq, ATAC-seq). Interestingly, we identified gene sets that are preferentially expressed maximally at picomolar or nanomolar concentrations. We are using these genes sets to explore the mechanisms of estrogen-regulated gene expression at physiologically relevant of E2 concentrations. Analysis of nascent RNA transcription using PRO-seq indicates regulation at the transcriptional level. Preliminary ERɑ chromatin binding assays show that while many loci require high levels of E2 for maximum ERɑ binding, others show maximum ERɑ binding at lower doses of E2. Further analyses show distinct enhancer features, such as chromatin accessibility and H3K27ac enrichment, may play a role in determining the response to E2 dosage. We are now determining the molecular mechanisms of dosage sensitivity using a multipronged approach integrating genomics, molecular biology, and cell-based assays. With these studies, we hope to understand a long overlooked physiological aspect of E2 with a comprehensive and global analysis of signal-dependent genomic responses. Presentation: 6/3/2024

Fluorescent lateral flow assay strip for Mycobacterium tuberculosis and Mycobacterium smegmatis based on mycobacteriophage tail protein and aptamer

Timely and facile monitoring of Mycobacterium tuberculosis (M. tuberculosis) plays an important role for preventing and controlling tuberculosis infection. Mycobacterium smegmatis (M. smegmatis) has long been employed as a safe surrogate for the investigation of M. tuberculosis. In this work, an aqueous soluble tail protein derived from our previously isolated mycobacteriophage was prepared with a recombinant expression technique and noted as GP89, which shows noticeable binding capacity to Mycobacterium genus. GP89 was sprayed as a capture agent onto a nitrocellulose membrane for forming the test line of a lateral flow assay (LFA) strip. Moreover, an aptamer binding M. tuberculosis and M. smegmatis was labeled with fluorescent microspheres to act as the signal tracer of the LFA method. With the GP89 based LFA, M. tuberculosis and M. smegmatis can be detected with the aid of a handheld UV flashlight or a portable fluorescent strip reader within 10 min. The concentration range for quantitating M. tuberculosis and M. smegmatis are both 1.0 × 102 CFU mL−1 - 1.0 × 106 CFU mL−1, and the detection limits for the two mycobacteria are 2.0 and 24 CFU mL−1 (S/N = 3), respectively. The test strip was applied to detect M. tuberculosis and M. smegmatis in different samples such as physiological salt solution, urine, and saliva. This study offers a promising screening tool for diagnosing M. tuberculosis infection in resource-limited institutes.

6703 Age-Related Reference Intervals for 11-Oxygenated Androgens in Children

Abstract Disclosure: L. IJsselstijn: None. R. Zellerer: None. R. Oude Engberink: None. B. van Zelst: None. S.A. van den Berg: None. Context: 11-Oxygenated androgens have emerged as major components of several disorders of androgen excess. Levels of 11-keto androstenedione (11KA4), 11β-hydroxy androstenedione (11OHA4), 11-keto testosterone (11KT) and 11β-hydroxy testosterone (11OHT) have been mainly studied in adults and in relation to various disorders. Although it is known that 11-oxygenated androgens are pivotal in adrenarche and pubarche, well established reference intervals for children are lacking. Objective: To establish age-related reference intervals for 11-oxygenated androgens in children. Methods: Serum samples were collected from apparently healthy children with ages ranged 0-18 years (n=186, 108 boys and 78 girls). Concentrations of 11KA4, 11OHA4, 11KT and 11OHT were determined by isotope dilution mass spectrometry. Before measurement the serum was deproteinized and purified by solid-phase extraction. The lower limit of quantitation for 11KA4, 11KT and 11OHT were 3.0 ng/dL (0.10 nmol/L), and for 11OHA4 9.1 ng/dL (0.30 nmol/L). Results: For 11KA4 a difference between boys and girls was observed until the age of 6. In girls 11KA4 was undetectable where in boys concentration up to 9.61 ng/dL (0.32 nmol/L) were measured. From the age of 6 an increase of 11KA4 was observed with increasing age. From the age of 13 concentrations stabilized at 4.21-28.5 ng/dL (0.14-0.95 nmol/L) without a difference between boys and girls. 11OHA4 was detectable at all ages and showed no differences between boys and girls, except for an apparently slightly higher concentration for boys until the age of 4. The concentration 11OHA4 increased with age in an almost linear way. At the age of 18 concentrations were observed of 60.5- 296.4 ng/dL (2.00-9.80 nmol/L). For 11KT a similar relation between the concentration and age was observed until the age of 14. At the age of 14 a plateau seems to be reached at concentrations of 14.5-74.4 ng/dL (0.48-2.46 nmol/L), which slightly decreased from the age of 17. 11OHT was undetectable in both boys and girls up to the age of 9 years. After the age of 9 the concentration range increased by age up to 30.4 ng/dL (1.00 nmol/L). From the age of 12 11OHT was detectable in all girl samples, where as in boys samples with undetectable concentrations were present at all ages. Conclusions: Age-related reference ranges were established for 11KA4, 11OHA4, 11KT and 11OHT. Overall no differences were observed between boys and girls, except for 11KA4 at a young age. The concentrations measured at the age of 18 correspond to the adult values known from literature for all 4 11-oxygenated androgens. Presentation: 6/1/2024

Diluting humic substances in water in molecular dynamics simulations: Are aggregates stable?

Natural organic matter (NOM) and humic substances (HS) as its part are key players in diverse biogeochemical processes occurring at interfaces at different scales, contributing to the carbon cycling, sorption reactions, transport and environmental fate of chemicals and biological activity. One important vision considers HS composed of small molecules interacting through non-covalent forces rather than representing high-molecular-weight substances. There is a continued interest in understanding the structure of NOM/HS and modeling their physico-chemical characteristics using molecular simulations. This work aimed to examine the stability of HS models, represented as aggregates formed by small molecules, upon dilution in water, by performing molecular dynamics (MD) simulations. The HS models were built to reproduce a 13C NMR-derived composition of standard Leonardite humic acid (HA) by using the Vienna Soil Organic Matter Modeler. The models varied in molecular size, amount of water and the choice of counter cation (Na+ vs Ca2+), while keeping the chemical composition identical, to link low-hydrated HS systems with aqueous NOM solutions in the concentration range of environmental significance. MD simulations demonstrated that HS aggregates disintegrate to some degree by diluting the system. The process occurs more easily in the presence of monovalent Na+ compared to divalent Ca2+. Strong interactions within the HS aggregates may remain at the level of dimers of small molecules revealing a higher stability against dilution. The simulation results support a step-wise mode of HS aggregation. It is suggested also that the existence of large-size HS molecules possibly undergoing step-wise aggregation should be taken into account while examining HS properties in aqueous solutions.

Sandwich-Type Electrochemical Aptasensor with Supramolecular Architecture for Prostate-Specific Antigen

A novel sandwich-type electrochemical aptasensor based on supramolecularly immobilized affinity bioreceptor was prepared via host–guest interactions. This method utilizes an adamantane-modified, target-responsive hairpin DNA aptamer as a capture molecular receptor, along with a perthiolated β-cyclodextrin (CD) covalently attached to a gold-modified electrode surface as the transduction element. The proposed sensing strategy employed an enzyme-modified aptamer as the signalling element to develop a sandwich-type aptasensor for detecting prostate-specific antigen (PSA). To achieve this, screen-printed carbon electrodes (SPCEs) with electrodeposited reduced graphene oxide (RGO) and gold nanoferns (AuNFs) were modified with the CD derivative to subsequently anchor the adamantane-modified anti-PSA aptamer via supramolecular associations. The sensing mechanism involves the affinity recognition of PSA molecules on the aptamer-enriched electrode surface, followed by the binding of an anti-PSA aptamer–horseradish peroxidase complex as a labelling element. This sandwich-type arrangement produces an analytical signal upon the addition of H2O2 and hydroquinone as enzyme substrates. The aptasensor successfully detected the biomarker within a concentration range of 0.5 ng/mL to 50 ng/mL, exhibiting high selectivity and a detection limit of 0.11 ng/mL in PBS.

(±)-Catechins inhibit prehaustorium formation in the parasitic weed Phelipanche ramosa and reduce tomato infestation.

Phelipanche ramosa L. (Pomel) is a noxious parasitic weed in field and vegetable crops in Mediterranean countries. Control of this pest is complex and far from being achieved, and new environmentally-friendly strategies are being sought. The present study evaluates the possibility of using (±)-catechins as a natural herbicide against broomrapes. The results show that (±)-catechins have no effect on GR24-induced germination over a wide concentration range (10-4 to 10-10 m), nor on radicle elongation after germination, but strongly inhibit, at 10-4 and 10-5 m, prehaustorium formation in response to the haustorium-inducing factor, cis/trans-zeatin. Accordingly, pot experiments involving the supplies of 10-5 m of (±)-catechins to tomato plants infested or not with P. ramosa demonstrate that (±)-catechins do not influence growth of non-parasitized tomato plants and prevent heavy infestation by strongly reducing parasite attachments and inducing parasite necrosis once they are attached. This study points the potential use of (±)-catechins for parasitic weed control. It raises also the question of the mechanisms involved in the inhibition of prehaustorium formation and the necrosis of parasite attachments in response to (±)-catechins application. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.