The role of NAA in securing the accuracy of analytical results in the inorganic trace analysis

Journal of Radioanalytical and Nuclear Chemistry - The unique value of the neutron activation analysis (NAA) for analytical quality assurance is demonstrated through its contribution to the...     

Vitamin A and Bone Health: A Review on Current Evidence

Vitamin A is a fat-soluble micronutrient essential for growth, immunity, and good vision. The preformed retinol is commonly found in food of animal origin whereas provitamin A is derived from food of plant origin. This review summarises the current evidence from animal, human and cell-culture studies on the effects of vitamin A towards bone health. Animal studies showed that the negative effects of retinol on the skeleton were observed at higher concentrations, especially on the cortical bone. In humans, the direct relationship between vitamin A and poor bone health was more pronounced in individuals with obesity or vitamin D deficiency. Mechanistically, vitamin A differentially influenced the stages of osteogenesis by enhancing early osteoblastic differentiation and inhibiting bone mineralisation via retinoic acid receptor (RAR) signalling and modulation of osteocyte/osteoblast-related bone peptides. However, adequate vitamin A intake through food or supplements was shown to maintain healthy bones. Meanwhile, provitamin A (carotene and β-cryptoxanthin) may also protect bone. In vitro evidence showed that carotene and β-cryptoxanthin may serve as precursors for retinoids, specifically all-trans-retinoic acid, which serve as ligand for RARs to promote osteogenesis and suppressed nuclear factor-kappa B activation to inhibit the differentiation and maturation of osteoclasts. In conclusion, we suggest that both vitamin A and provitamin A may be potential bone-protecting agents, and more studies are warranted to support this hypothesis.     

Micelles as Containers for Self‐Assembled Nanodevices: A Fluorescent Sensor for Lipophilicity

Potentiometric titrations, fluorescence versus pH titrations, dynamic light scattering and fluorescence polarization anisotropy studies demonstrate that inside the nanodimensioned Triton X‐100 micelles, 1‐pyrenecarboxylic acid, PCOO^?, forms an apical complex with the Zn²⁺ cation encircled by a lipophilic cyclen ligand and hugely increasing its fluorescence. The ability of the Zn²⁺‐cyclen‐PCOO^? complex plus its micellar container to act as a fluorescent sensor to evaluate the lipophilicity of molecular species is demonstrated on the fatty acid series CH₃(CH₂)_xCOOH (x=0–16). At pH 7.4 a decrease in fluorescence is observed on the addition of fatty acids that is directly related to their chain length, that is, to their tendency to enter the micellar containers, where they dislocate PCOO^? from the Zn²⁺ centre. The independent determination of fatty acid pK_a values in the presence of Triton X‐100 micelles confirms that our fluorescent micellar device is capable of sensing their lipophilicity.     

A definitive RNAA method for determination of selenium in biological samples: uncertainty evaluation and assessment of degree of accuracy

This article describes work on the development of a highly accurate RNAA method for determination of selenium in biological samples. The analytical post-irradiation procedure is based on a combination of cation-exchange and extraction chromatography with final selective and quantitative fixation of selenium on a column packed with 3,3′-diaminobenzidine (DAB) supported on Amberlite XAD4, followed by gamma-ray spectrometric measurement. The suitability and accuracy of the method was demonstrated by analysing CRMs with certified selenium content. The uncertainty budget for Se determination in standard reference material Peach Leaves NBS 1547 was estimated; the combined standard uncertainty was calculated as 1.7%. The described method fulfils all the criteria for definitive methods. It was subsequently used for determination of selenium in biological materials intended as new CRMs and proficiency test samples.     

Spectroscopic characterisation of LaGaO3:Er3+ crystals

LaGaO₃ crystals doped with Er³⁺ ions were grown by the Czochralski method and their optical properties were examined. The Er³⁺ energy levels have been determined from the low-temperature absorption and emission spectra. The results of Judd–Ofelt analysis are presented and compared with experimental data. The emission cross sections are determined for the ⁴ I _13/2→⁴ I _15/2 (1.55 μm) and ⁴ I _11/2→⁴ I _13/2 (2.85 μm) transitions of erbium. Received: 6 December 1999 / Revised version: 10 February 2000 / Published online: 27 April 2000     

Laser oscillation of Er3+:YVO4 and Er3+, Yb3+:YVO4 crystals in the spectral range around 1.6 μm

Laser oscillation around 1.6 μm was realised at room temperature for low-doped Er:YVO₄ crystals (0.5 at % and 1 at %) as well as for Er(1 at %), Yb(5 at %):YVO₄ crystal in continuous-wave mode. The maximum slope of the input–output curve was about 19% (vs. absorbed power) for Er(0.5 at %):YVO₄. The laser oscillation was discretely tunable in the spectral range between 1531 and 1604 nm. Received: 24. August 2000 / Published online: 8 November 2000     

Analysis of Cation-Dependent DNA (G<Subscript>3</Subscript>T<Subscript>1</Subscript>)<Subscript>4</Subscript> Shape Change Using Fluorescence Correlation Spectroscopy

In G-rich DNA, it is well known that the form changes from single-strand DNA to G-quadruplex due to cations. In this study, we analyze the diffusion coefficient and fluorescence intensity obtained by fluorescence correlation spectroscopy for short G-rich DNA of the (G₃T₁)₄ sequence labeled as 5-Carboxytetramethylrhodamine (TAMRA) with variation of the K⁺ ion concentration. At a K⁺ ion concentration of more than 200 mM, the single-strand DNA was changed to the G-quadruplex. The size of the G-quadruplex decreased to 86% than the size of the single strand DNA at K⁺ ion concentration of 0 M. The size of the G-quadruplex and the fluorescence intensity of TAMRA attached to the DNA were constant with an increase in the K⁺ ion concentration between 200 and 800 mM. This means that the size of the DNA and the fluorescence intensity of the TAMRA are not affected by the K⁺ ion concentration at the G-quadruplex structure because the binding structure of DNA and TAMRA dye leads to stability at a concentration of less than 100 mM K⁺. Based on our short G-rich DNA results, longer G-rich DNA is analyzed for the diffusion coefficient of the DNA and the fluorescence intensity variation of fluorescence dye attached to the DNA.     

Analysis of Quantum Rod Diffusion by Polarized Fluorescence Correlation Spectroscopy

To measure the polarization dependence of fluorescent probes, a confocal-microscope-based polarized fluorescence correlation spectroscopy system was developed, and the polarization dependence on the rotational diffusion of well-defined quantum rods (Qrods) was investigated and characterized. The rotational diffusion region of the Qrods was observed over a time range of less than 10^?5 s in a water solution, and the rotational diffusion parameters were extracted using a rotational diffusion model in which the viscosity of the solution media was varied. Our work demonstrated that polarized fluorescence correlation spectroscopy (FCS) is useful for investigating both the rotational and translational diffusion of fluorescent probes.     

The Health-Promoting Properties and Clinical Applications of Rice Bran Arabinoxylan Modified with Shiitake Mushroom Enzyme—A Narrative Review

Rice bran arabinoxylan compound (RBAC) is derived from defatted rice bran hydrolyzed with Lentinus edodes mycelial enzyme. It has been marketed as a functional food and a nutraceutical with health-promoting properties. Some research has demonstrated this rice bran derivative to be a potent immunomodulator, which also possesses anti-inflammatory, antioxidant, and anti-angiogenic properties. To date, research on RBAC has predominantly focused on its immunomodulatory action and application as a complementary therapy for cancer. Nonetheless, the clinical applications of RBAC can extend beyond cancer therapy. This article is a narrative review of the research on the potential benefits of RBAC for cancer and other health conditions based on the available literature. RBAC research has shown it to be useful as a complementary treatment for cancer and human immunodeficiency virus infection. It can positively modulate serum glucose, lipid and protein metabolism in diabetic patients. Additionally, RBAC has been shown to ameliorate irritable bowel syndrome and protect against liver injury caused by hepatitis or nonalcoholic fatty liver disease. It can potentially ease symptoms in chronic fatigue syndrome and prevent the common cold. RBAC is safe to consume and has no known side effects at the typical dosage of 2–3 g/day. Nevertheless, further research in both basic studies and human clinical trials are required to investigate the clinical applications, mechanisms, and effects of RBAC.     

High‐performance liquid chromatographic method for the quantification of Mitragyna inermis alkaloids in order to perform pharmacokinetic studies

In Africa, Mitragyna inermis (Willd.) O. Kuntze (Rubiaceae) is commonly used in traditional medicine to treat malaria. Antimalarial activity is mostly due to the hydromethanolic extract of M. inermis leaves and especially to the main alkaloids, uncarine D and isorhynchophilline. In the present study, we describe for the first time an HPLC method for the simultaneous quantification of uncarine D and isorhynchophylline in biological matrices. SPE was used to extract the components and the internal standard naphthalene from human and pig plasma samples. Chromatographic separation was performed on a C‐18 reversed column at a flow rate of 1 mL/min, using methanol–phosphate buffer (10:90, pH 7), as a mobile phase. Good linearity was observed over the concentration ranges of 0.0662–3.31 μg/mL for uncarine D and 0.0476–2.38 μg/mL for isorynchophylline. The precision was less than 12% and the accuracy was from 86 to 107% without any discrepancy between the two species. Uncarine D and isorhynchophylline recoveries were over 80%. These results allowed the quantification of both uncarine D and isorhynchophylline in pig plasma after intravenous administration of M. inermis extract.