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The subtraction of background components from observed spectra is essential in performing multivariable analysis, frequently applied to Raman spectra of cells. The subtraction procedure, however, is manual and time consuming, especially for big data. Here, we propose an automated method for removing background information from measured spectra of cells, exhibiting the theoretical framework and an experimental application.

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Energy demands have motivated the development of shale formations as significant unconventional reservoirs. The anisotropy of shales plays a significant role in both the mechanical behavior and engineering activities. Alternating layers presented in shales affect the propagation of waves, causing anisotropy at various frequencies. Simplifying the complicated interior structures of shales is conducive to characterize the anisotropic properties. Therefore, simulative shale core samples were designed and fabricated using additive manufacturing processes, and layer-caused dielectric anisotropy was investigated by terahertz (THz) time-domain spectroscopy. On the basis of effective medium theory, the change of the optical length caused by refraction of rays was discussed and modeled. It is believed that the refraction of rays at the interfaces is the source of THz propagation anisotropy in the multilayered structure, and the anisotropy degree is mainly influenced by the layer thickness as well as the refractive index.

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A sensitive fluorescent method for the detection of Hg²⁺ was developed based on triple-helix molecular switch (THMS)-induced hybridization chain reaction (HCR) amplification. THMS was composed of a T-rich mercury-specific probe and an initiator probe, designed by the Watson–Crick and Hoogsteen base pairings and employed as a signal trigger. Two hairpin probes containing the G-quadruplex sequence were used as signal amplification elements. In the presence of Hg²⁺, the T-Hg²⁺-T mismatch resulted in disassembling the THMS and releasing the initiator probe. One of the hairpins was opened by the released initiator probe, which triggered a successive cross-opening of two hairpins based the strand displacement principle, resulting in the formation of long-chain DNA with multiple G-quadruplex. When thioflavin T (ThT), a fluorophore, was bound to the G-quadruplex, an obvious fluorescence enhancement would occur. This sensing system enabled the highly sensitive and selective detection of aqueous Hg²⁺ with a limit-of-detection of 10.2 pM.

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A new kinetic and automated assay was developed to determine ceruloplasmin ferroxidase activity. Ferrous ions are turned into ferric ions via catalytic activity of the ferroxidase enzyme. Acetohydroxamic acid, a chromogen, forms a colored complex with ferric ions. This reaction was measured kinetically. Significant and strong correlations were obtained between the new acetohydroxamic method and the p-phenylenediamine oxidase (r = 0.988, p <0.001), o-dianisidine oxidase (r = 0.981, p <0.001), norfloxacine oxidase (r = 0.989, p <0.001) and nephelometric methods (r = 0.861, p <0.001). This reliable, applicable, user-friendly, and low-priced method can be performed fully automatically or with manual spectrophotometry, and can be used to measure the ferroxidase activity of ceruloplasmin.

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A label-free fluorescent probe based on autofluorescent hyperbranched poly(amide amine) (HPAMAM) for copper ions was designed. HPAMAM is a cationic polymer containing many amino groups, which could bind Cu²⁺ ions to form cupric amine complexes, leading to a selective quenching of the fluorescence intensity of HPAMAM via inner filter effect. The fluorescence intensity of HPAMAM decreased with increasing concentration of Cu²⁺ ions and the linear response ranged from 0.05 to 25 μM (R² = 0.995), with the corresponding detection limit (3σ/k) of 17.15 nM. The HPAMAM fluorescent probe provided a simple, rapid, selective and sensitive fluorometric method for detecting Cu²⁺ ions, which could be also applied for detection of Cu²⁺ ions in real water samples.

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The niobium(V) complex with tetraphenylporphin having OH⁻ as an auxilliay ligand exists as a dimeric complex, [Nb₂(tpp)₂O₃] at a total concentration >10^−4.5 mol dm⁻³, and reacts with an aliphatic or aromatic polyhydroxy compound to form a monomeric complex containing chelate rings by coordination of the deprotonated species, and to cause an appreciable UV-Vis spectral change. In contrast to phenylboronic acid (PBA), the reactivity of [Nb₂(tpp)₂O₃] is independent of pH at least between 4 and 8. Aliphatic comounds are more reactive than aromatic compounds in dioxane–water, while the reactivity order is reversed in the two-phase reaction. The sugar selectivity order of [Nb₂(tpp)₂O₃] in dioxane–water (10:1) (sorbose > fructose >> mannose > arabinose, galactose > glucose) is appreciably different from that of PBA (fructose > sorbose >> arabinose > galactose > mannose > glucose). This may be related to the difference in size of the Lewis acidic center.

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Continuous wave electron paramagnetic resonance (CW EPR) and X-band (9 GHz) EPR imaging (EPRI) were used to nondestructively investigate the possible differentiation between malignant melanoma (MM) and nevus pigmentosus (NP) melanin radicals in paraffin-embedded specimens. The EPR spectra of both samples were analyzed using linewidth, spectral pattern, and X-band EPRI. The CW-EPR spectra of the MM showed an additional signal overlap. Eumelanin- and pheomelanin-related radicals were observed in the MM specimens. The EPR results revealed that the peak-to-peak linewidths (ΔH_pp) of paraffin-embedded MM and NP samples were 0.65 ± 0.01 and 0.69 ± 0.01 mT, respectively. The g-value was 2.005 for both samples. Moreover, the two-dimensional (2D) EPRI of the MM showed different signal intensities at the different tumor stages, unlike the NP, which displayed fewer variations in signal intensity. Thus, the present results suggest that EPR and 2D EPRI can be useful for characterization of the two melanin radicals in the MM and for determination of their size and concentration.

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A new concept of flow analysis, internal standard-amplitude modulated multiplexed flow analysis, is proposed. A proof of concept was verified by applying it to the determination of ferrous ion (Fe²⁺) by 1,10-phenanthroline (o-Phen) spectrophotometry. The flow rates of sample solutions containing Methylene Blue (MB) as an internal standard substance were sinusoidally varied at different frequencies. The solutions were merged with a color reagent (o-Phen) solution, while the total flow rate was held constant. Downstream, analytical signals were monitored at the maximum absorption wavelengths of Fe²⁺-o-Phen complex and of MB (510 and 644 nm, respectively). The signals were respectively analyzed by fast Fourier transform. The concentrations of the analytes in respective samples were simultaneously determined from the amplitudes of the corresponding wave components. The precision, linearity of the calibration curve, limit of detection and robustness against deliberate fluctuation in flow rate were greatly improved by introducing the internal standard method. Good recoveries of around 100% were obtained for Fe²⁺ spiked into real water samples.

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A novel biosensor for sensitively detecting potassium ion (K⁺) has been developed based on fluorescent copper nanoparticles (Cu NPs). In our design, we employ a label-free single-strand DNA (ssDNA) that contains two parts. One is 3′-terminus structure-switching aptamers (SSAs) that can fold into G-quadruplex after binding with its target K⁺. The other is 5′-terminus poly thymine (polyT) which works as a template to construct fluorescent Cu NPs. After incubating with K⁺, the part SSAs go through target-induced conformational changes. Benifiting from the exceptional digestion ability of exonuclease I (Exo I), the G-quadruplexes display effective resistance to nuclease digestion, so that 5′-terminus polyT remains and the in situ formation of Cu NPs provides a turn-on fluorescent signal that is used to evaluate the concentration of K⁺. The recovery of the fluorescence intensity is linearly correlated with the K⁺ concentration in the range of 0.05 to 1 mM with a detection limit of 0.05 mM. Compared with some methods, this assay is cost-effective and facile with high specificity. Meanwhile, this excellent strategy shows a great potentiality in other sensing approaches that can study the interaction between similar SSAs and different specific targets.

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Reaction conditions for the selective derivatization of three types of aromatic diamines without clean-up in an aqueous solution using 4-(N-chloroformylmethyl-N-methylamino)-7-nitro-2,1,3-benzoxadiazole (NBD-COCl) have been developed for simple, fast, and selective analysis by HPLC. The aromatic amines were derivatized to give di-NBD-CO-aromatic amines at 35°C for 5 min in a buffer solution at pH 5 containing a low acetonitrile concentration (0 – 400 ng/mL, n = 5, r >0.998). The retention times of these di-NBD-CO-aromatic amines were <5 min. Sample solutions containing aromatic amines, phenols, and an aliphatic amine were also prepared. Under the optimized reaction conditions (i.e., low acetonitrile content and acidic conditions), no derivatization of the phenols and the aliphatic amine was observed. These were related to the differences in the pK_a values of the target substances, the organic solvent concentration, and the reaction solution pH. For the model system, a sulfuric acid-impregnated filter was spiked with the aromatic amines, phenols, and aliphatic amine prior to extraction, derivatization, and measurement by HPLC. Only aromatic amines were detected quantitatively, with no other compounds being observed.

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The selective isolation of phosphorylated peptides and subsequent analysis using mass spectrometry is important for understanding how protein kinase and phosphatase signals can precisely modulate the on/off states of signal transduction pathways. However, the isolation and detection of multi-phosphorylated peptides is still limited due to their distinct affinity to various materials and their poor ionization efficiency. Here, we report a highly efficient and selective enrichment of phosphorylated peptides using binuclear Zn²⁺-dipicolylamine complex-coated magnetic microspheres (ZnMMs). ZnMMs can utilize the rapid and selective isolation/enrichment of phosphorylated peptides and the subsequent mass spectrometric analysis, given the intrinsic magnetic property of magnetic microspheres and the highly selective binding ability of the binuclear Zn²⁺-dipicolylamine complex to phosphate groups. α-Casein and β-casein were chosen for a proof-of-concept demonstration. We contemplated that phosphopeptides were selectively isolated and enriched from both the tryptic digests of casein proteins and mixed samples with a high degree of sensitivity by facilitating ZnMMs. Especially, ZnMMs showed high efficiency with multi-phosphopeptides, which are in general difficult to be examined by mass analysis on account of their poor ionization efficiency. For the model protein α, β-casein mixture of the tryptic digest, 17 phosphopeptides were identified with ZnMMs and 82% of the enriched phosphopeptides were multi-phosphorylated peptides, indicating that ZnMMs have excellent enrichment efficiency and strong affinity towards multi-phosphorylated peptides.

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Tandem mass tags (TMT) are usually introduced at the levels of isolated proteins or peptides. Here, for the first time, we report the labeling of whole cells and a critical evaluation of its performance in comparison to conventional labeling approaches. The obtained results indicated that TMT protein labeling using intact cells is generally possible, if it is coupled to a subsequent enrichment using anti-TMT antibody. The quantitative results were similar to those obtained after labeling of isolated proteins and both were found to be slightly complementary to peptide labeling. Furthermore, when using NHS-based TMT, no specificity towards cell surface proteins was observed in the case of cell labeling. In summary, the conducted study revealed first evidence for the general possibility of TMT cell labeling and highlighted limitations of NHS-based labeling reagents. Future studies should therefore focus on the synthesis and investigation of membrane impermeable TMTs to increase specificity towards cell surface proteins.

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The transmission infrared absorption spectra of an aqueous lactic acid solution was measured over a pH range of 2.66 – 1.59 using a cell with an optical path length of 12 μm. Absorption peaks were then identified by density functional theory (DFT) calculations. The observed pH-dependent changes in the absorbance spectra were consistent with the properties of the assigned functional groups. We therefore believe that the present method can be applied to the contactless and non-invasive quantitative evaluation of pH values in aqueous systems, such as bioprocesses and bioimaging.

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Two simple and sensitive kinetic-fluorometric methods have been developed for the determination of lanthanum(III): fluorescence quenching generated by the oxidation of safranine T or phenosafranine with potassium bromate in an acetate buffer solution. The rate of the oxidation reaction is significantly accelerated after adding lanthanum(III). A good linearity between the relative fluorescence intensity and lanthanum(III) is observed in the range of both 0.04 – 2.0 and 4.0 – 16 μg/mL. The detection limits have been 3.6 × 10⁻³ and 0.334 μg/mL respectively. The accuracy and reliability of the methods are further validated by recovery studies via a standard-addition method, with percentage recoveries ranging from 98 to 102%. Comparing the results of two measured reaction systems, we find that the safranine T reaction system provides high sensitivity and a wider linear range. In consequence, we have chosen the safranine T system to detect sample water, and explored the reaction mechanism.

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We examined photochemical effects by ultraviolet irradiation on facilitated proton transfer at a water/1,2-dichloroethane (W/DCE) interface by ion-transfer voltammetry using a Xe flash lamp. 5,10,15,20-Tetraphenyl-21H,23H-porphine (H₂TPP) or its metal complex, such as cobalt (Co(II)TPP), zinc (Zn(II)TPP), and nickel (Ni(II)TPP) complexes, was added into the DCE phase as an ionophore for the facilitated proton transfer. After we irradiated the W/DCE interface through the W phase, the voltammetric waves for proton transfer facilitated by H₂TPP and Co(II)TPP were remarkably enhanced and shifted to the lower potential region, compared to those before irradiation. We confirmed from the pH and argentometric titrations that such enhancements and shifts of the waves were caused by hydrogen chloride (HCl) produced by photodecomposition of DCE. On the other hand, the waves for proton transfer facilitated by Zn(II)TPP and Ni(II)TPP were very small from the beginning, and showed neither enhancement nor any shift upon irradiation.

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A carbon screen-printed electrode was modified with copper nanoparticles from their dispersion obtained via pulsed laser ablation of a copper target in ethanol. The modified electrode exhibited activity in ascorbic acid electrochemical oxidation, giving an anodic current peak on voltammograms. Linear sweep and cyclic voltammetry have shown a linear dependence of the signal (both peak height and peak area) on the ascorbic acid concentration. The linear range from 1 to 250 μM of ascorbic acid was studied, and the detection limit was experimentally found to be 0.5 μM. The amperometric response to the addition of ascorbic acid portions into the solution was recorded. For the case of the simultaneous presence of ascorbic acid and glucose, two separate signal were obtained. Thus, the modified electrodes are characterized by the following advantages: disposable use; small amount of the samples required for the analysis; lower price (cheap copper is used); simple and easy modification procedure; good metrological characteristics; selectivity.

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A bilayer lipid membrane sensor was constructed with a miniaturized auto-patch system. The performance of the patch system was optimized to obtain an analytically relevant signal. A biosensor based on an anti-BSA-antibody as a receptor and gramicidin as a signal transduction element was demonstrated. The sensor for BSA exhibited a detection limit of pg/mL level for BSA.

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In this study, poly(glycidyl methacrylate-methyl methacrylate-divinylbenzene) was synthesized in the form of microspheres, and then functionalized by 2-aminobenzothiazole ligand. The sorption properties of these functionalized microspheres were investigated for separation, preconcentration and determination of Al(III), Fe(II), Co(II), Cu(II), Cd(II) and Pb(II) ions using flame atomic absorption spectrometry. The optimum pH values for quantitative sorption were 2 – 4, 5 – 8, 6 – 8, 4 – 6, 2 – 6 and 2 – 3 for Al(III), Fe(II), Co(II), Cu(II), Cd(II) and Pb(II), respectively, and also the highest sorption capacity of the functionalized microspheres was found to be for Cu(II) with the value of 1.87 mmol g⁻¹. The detection limits (3σ; N = 6) obtained for the studied metals in the optimal conditions were observed in the range of 0.26 – 2.20 μg L⁻¹. The proposed method was successfully applied to different beverage samples for the determination of Al(III), Fe(II), Co(II), Cu(II), Cd(II) and Pb(II) ions, with the relative standard deviation of <3.7%.

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Caenorhabditis elegans (C. elegans), which shares a considerable amount of characteristics with human genes is one of the important model organisms for the study of behavioral responses. Thermotaxis is a representative behavior response of C. elegans; C. elegans stores the cultivation temperature in thermosensory neurons and moves to the cultivation temperature region in a temperature variation. In this study, we developed a microfluidic system for effective thermotaxis analysis of C. elegans. The microfluidic channel was fabricated using polydimethylsiloxane (PDMS) by soft lithography process. The temperature gradient (15 – 20°C) was generated in the microchannel and controlled by Peltier modules attached to the bottom of the channel. The thermotaxis of wild type (N2), tax-4(p678) and ttx-7(nj50) mutants were effectively analyzed using this microfluidic system. We believe that this system can be employed as a basic platform for studying the neural circuit of C. elegans responding to external stimuli.

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The extensive use of polybrominated diphenyl ethers (PBDEs) has resulted in its increasingly widespread presence. Especially the lower halogenated PBDEs accumulate to a greater degree than the higher halogenated PBDEs in house dust, sewage sludge, pets, or even humans. In the present work, we developed an ultrasensitive biotin-streptavidin-enhanced carbon nanotube amplification strategy for the immunodetection of PBDEs, in which single-walled carbon nanotubes were used to immobilize numerous streptavidin. Meanwhile, we used biotin conjugated horseradish peroxidase (B-HRP) and biotin conjugated Goat anti-rabbit (B-IgG) to link the HRP and IgG to CNTs by using a biotin-streptavidin system. The sensitivity of the streptavidin-biotin-IgG-CNTs-HRP bioconjugate was compared with a commercial HRP-labelled IgG by using indirect competitive ELISA. The limit of this proposed ELISA detection (IC₁₀) was 0.0059 ng/mL, showing a 20-time lower detection limit over the commercial one (IC₁₀ = 0.1193 ng/mL). Finally, we applied the assay to the detection of PBDEs in dust samples. The results were consistent with those using GC-ECD, which confirmed that the proposed amplification strategy was accurate and receptive. This proposed biotin-streptavidin-enhanced carbon nanotube amplification strategy would be useful for ultrasensitive immunodetection in environmental studies.

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The distribution behavior of amphoteric 8-quinolinol (HQ) between ionic liquid (IL) phase and aqueous phase and ionic liquid chelate extraction behavior of iron(III) with HQ were investigated using four 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (C_nmimTf₂N, n = 2, 4, 6 and 8) ILs. Not only neutral HQ but also cationic H₂Q⁺ were distributed into the IL phase, and the latter distribution based on cation-exchange with C_nmim⁺ was pronounced in the use of IL having a less-hydrophobic cation, such as C₂mim⁺. In the IL chelate extraction of iron(III), the extractability increased with the increase in the hydrophobicity of IL as the extraction phase. Nevertheless, the determined equilibrium constants for the extraction as the neutral complex FeQ₃ were similar to one another. The difference in the extractability among the ILs was due to the difference in the distribution of H₂Q⁺ into the extraction phase. In addition, the cationic coordinatively-unsaturated complex FeQ₂⁺ was also extracted in use of less-hydrophobic C₂mimTf₂N.

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In order to advance the performances of micro chemical and biochemical systems on a chip, the fabrication of microstructures such as channels and pillars is an essential basic technology. However, conventional fabrication methods based on wet etching have limitations in their applications for device engineering. In this study, we report on a new microchannel fabrication process on a fused silica substrate using photoresist and plasma etching based on C₃F₈, CHF₃, and Ar gases. Deep, rectangular microchannels, having vertical angles close to 90°, 10 μm-scale deep and low surface roughness of less than 1 nm, could be fabricated on a fused silica substrate at high etching rates on the order of 5 – 7 nm s⁻¹. This metal-free fabrication methodology is expected to be a low-cost, easy, and simple technique for a fused silica microstructure applications.

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A fluorescence quenching assay based on a ligase detection reaction was developed for facile and rapid detection of point mutations present in a mixed population of non-variant DNA. If the test DNA carried a targeted mutation, then the two allele-specific primers were ligated to form a molecular beacon resulting in the expected fluorescence quenching signatures. Using this method, we successfully detected as low as 5% mutant DNA in a mixture of wild-type DNA (t test at 99% confidence level).

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We report on the photoluminescent (PL) properties of carbon nanodots (CNDs) doped with nitrogen and sulfur obtained by the pyrolytic carbonization of amino acids as precursors. Prepared CNDs exhibit stable PL emission under a wide variety of aqueous conditions. The results also provided the way to tune a PL intensity of CNDs by varying the amount of heteroatoms in precursors with a binary mixture of amino acids. The PL quantum yields of the obtained CNDs were determined to be from 0.079 to 0.571.

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A novel friction tester has been developed to clarify the friction mechanism between engine oil and metals by in situ/operando measurements of the X-ray absorption near edge structure (XANES) using the total electron yield (TEY) method. The tester can perform frictional motion with engine oil and metals in a vacuum chamber under a vacuum of 10⁻⁷ Torr during TEY-XANES measurements in BL-6.3.2 at the Advanced Light Source (ALS). From in situ XANES measurements in the C K and Fe L regions, the organic molecule layers at the oil/metals interfaces have been successfully observed.

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