Identification and analysis of alkaloids in cortex Phellodendron amurense by high‐performance liquid chromatography with electrospray ionization mass spectrometry coupled with photodiode array detection

Alkaloids from Cortex Phellodendron amurense Rupr. were identified to determine the material basis for the bioactivity of this herb. HPLC–ESI‐MS with photodiode array detection coupled to XCharge C₁₈ column was applied to analyze the alkaloids qualitatively and quantitatively. A total of 37 alkaloids were identified and tentatively characterized from the ethanol extract by online ESI‐MSⁿ fragmentation and UV spectral analysis. A total of ten alkaloids, including four novel natural products, were tentatively identified for the first time in P. amurense. The fragmentation pathways for certain compounds were analyzed. The contents of a pair of isomers (columbamine and jatrorrhizine) and four main alkaloids (phellodendrine, magnoflorine, berberine, and palmatine) were simultaneously quantified using the aforementioned method. Results showed that the newly discovered and known components of P. amurense were helpful in determining the material basis for the bioactivity of the herb. The application of the XCharge C₁₈ column is a suitable and practical method for the isolation of alkaloids in plants.     

Quantification of erythromycin in pharmaceutical formulation by transmission Fourier transform infrared spectroscopy

A simple, cost-effective and environmental friendly analytical method was developed for the quantification of erythromycin in tablet formulation using transmission Fourier Transform Infrared (FT-IR) spectroscopy for routine quality control analysis. There is no need of sample preparation except pellet formation for FT-IR analysis. Use of solvent was totally avoided in this method. Calibration was carried out by using simple Beer’s law in the FT-IR region between 1743 and 1697 cm⁻¹. The excellent coefficient of determination (R² = 0.998) was achieved with 0.0247 and 1.14 root mean square error of prediction (RMSEP) and root mean square error of cross validation (RMSECV), respectively. The results of the study revealed that the transmission FT-IR spectroscopy could be effectively used for rapid determination of active ingredients like erythromycin in pharmaceutical formulations to control the quality of finished products.     

Supramolecular optical sensor arrays for on-site analytical devices

Supramolecular optical chemosensors are useful tools in analytical chemistry for the visualization of molecular recognition information. One advantage is that they can be utilized for array systems to detect multiple analytes. However, chemosensor arrays have been evaluated mainly in the solution phase, which limits a wide range of practical applications. Thus, appropriate solid support materials such as polymer gels and papers are required to broaden the scope of the application of chemosensors as on-site analytical tools. In this review, we summarize the actual approaches for the fabrication of solid-state chemosensor arrays combined with powerful data processing techniques and portable digital recorders for real-world applications.     

Improved Stabilities of Labeling Probes for the Selective Modification of Endogenous Proteins in Living Cells and In Vivo

To date, various affinity-based protein labeling probes have been developed and applied in biological research to modify endogenous proteins in cell lysates and on the cell surface. However, the reactive groups on the labeling probes are also the cause of probe instability and nonselective labeling in a more complex environment, e. g., intracellular and in vivo. Here, we show that labeling probes composed of a sterically stabilized difluorophenyl pivalate can achieve efficient and selective labeling of endogenous proteins on the cell surface, inside living cells and in vivo. As compared with the existing protein labeling probes, probes with the difluorophenyl pivalate exhibit several advantages, including long-term stability in stock solutions, resistance to enzymatic hydrolysis and can be customized easily with diverse fluorophores and protein ligands. With this probe design, endogenous hypoxia biomarker in living cells and nude mice were successfully labeled and validated by in vivo, ex vivo, and immunohistochemistry imaging.     

Raman Imaging: An Impending Approach Towards Cancer Diagnosis

In accordance with the recent studies, Raman spectroscopy is well experimented as a highly sensitive analytical and imaging technique in biomedical research, mainly for various disease diagnosis including cancer. In comparison with other imaging modalities, Raman spectroscopy facilitate numerous assistances owing to its low background signal, immense spatial resolution, high chemical specificity, multiplexing capability, excellent photo stability and non-invasive detection capability. In cancer diagnosis Raman imaging intervened as a promising investigative tool to provide molecular level information to differentiate the cancerous vs non-cancerous cells, tissues and even in body fluids. Anciently, spontaneous Raman scattering is very feeble due to its low signal intensity and long acquisition time but new advanced techniques like coherent Raman scattering (CRS) and surface enhanced Raman scattering (SERS) gradually superseded these issues. So, the present review focuses on the recent developments and applications of Raman spectroscopy-based imaging techniques for cancer diagnosis.     

Negative refraction and imaging of acoustic waves in a two-dimensional square chiral lattice structure

The negative refraction behavior and imaging effect for acoustic waves in a kind of two-dimensional square chiral lattice structure are studied in this paper. The unit cell of the proposed structure consists of four zigzag arms connected through a thin circular ring at the central part. The relation of the symmetry of the unit cell and the negative refraction phenomenon is investigated. Using the finite element method, we calculate the band structures and the equi-frequency surfaces of the system, and confirm the frequency range where the negative refraction is present. Due to the rotational symmetry of the unit cell, a phase difference is induced to the waves propagating from a point source through the structure to the other side. The phase difference is related to the width of the structure and the frequency of the source, so we can get a tunable deviated imaging. This kind of phenomenon is also demonstrated by the numerical simulation of two Gaussian beams that are symmetrical about the interface normal with the same incident angle, and the different negative refractive indexes are presented. Based on this special performance, a double-functional mirror-symmetrical slab is proposed for realizing acoustic focusing and beam separation.     

Precision and sensitivity optimization of quantitative measurements in solid state NMR

This work presents a methodology for optimizing the precision, accuracy and sensitivity of quantitative solid state NMR measurements based on the external reference method. It is shown that the sample must be exclusively located within and completely span the coil region where the NMR response is directly proportional to the sample amount. We describe two methods to determine this "quantitative" coil volume, based on whether the probe is equipped or not with a gradient coil. In addition, to improve the sensitivity and the accuracy, an optimum rotor packing design is described, which allows the sample volume of the rotor to be matched to the quantitative coil volume. Experiments conducted on adamantane and NaCl, which are representative of a soft and hard material, respectively, show that one order of magnitude increase in experimental precision can be achieved with this methodology. Interestingly, the precision can be further improved by using the ERETIC method in order to compensate for most instrumental instabilities.     

Dispersion measurements using time-of-flight remote detection MRI

Remote detection nuclear magnetic resonance and magnetic resonance imaging can be used to study fluid flow and dispersion in a porous medium from a purely Eulerian point of view (i.e., in a laboratory frame of reference). Information about fluid displacement is obtained on a macroscopic scale in a long-time regime, while local velocity distributions are averaged out. It is shown how these experiments can be described using the common flow propagator formalism and how experimental data can be analyzed to obtain effective porosity, flow velocity inside the porous medium, fluid dispersion and flow tracing of fluid.     

High-resolution transmission electron microscopy study on reversion of Al2CuMg precipitates in Al–Cu–Mg alloys under irradiation

Image deconvolution analyses showed that reversion of S-Al₂CuMg precipitates occurred in an Al–Cu–Mg alloy during high-resolution transmission electron microscopy observations. A fraction of Mg and Cu atoms in the precipitates diffused into Al matrix due to electron beam irradiation at 300 kV, resulting in structural/chemical reversion of the precipitates. The structural reversion of the S-Al₂CuMg precipitates is closely related with irradiation-induced displacement of atoms. The strong attraction between Cu and Mg atoms might assist the sub-threshold displacement of Cu atoms. One transitional structure is determined to be S′′-Al₁₀Cu₃Mg₃, a precursor of S-Al₂CuMg. Two other transitional structures, Al₃CuMg and Al₁₈Cu₅Mg₅ which have the same lattice parameters of a = c = 0.405 nm as that of S′′-Al₁₀Cu₃Mg₃, but different b values, are suggested.     

Three dimensional accurate morphology measurements of polystyrene standard particles on silicon substrate by electron tomography

Polystyrene latex (PSL) nanoparticle (NP) sample is one of the most widely used standard materials. It is used for calibration of particle counters and particle size measurement tools. It has been reported that the measured NP sizes by various methods, such as Differential Mobility Analysis, dynamic light scattering (DLS), optical microscopy (OM), scanning electron microscopy (SEM) and atomic force microscopy (AFM), differ from each other. Deformation of PSL NPs on mica substrate has been reported in AFM measurements: the lateral width of PSL NPs is smaller than their vertical height. To provide a reliable calibration standard, the deformation must be measured by a method that can reliably visualize the entire three dimensional (3D) shape of the PSL NPs. Here we present a method for detailed measurement of PSL NP 3D shape by means of electron tomography in a transmission electron microscope. The observed shape of the PSL NPs with 100 nm and 50 nm diameter were not spherical, but squished in direction perpendicular to the support substrate by about 7.4% and 12.1%, respectively. The high difference in surface energy of the PSL NPs and that of substrate together with their low Young modulus appear to explain the squishing of the NPs without presence of water film.