Titrimetry

The constantly increasing requests for the measurement of serum 25-hydroxyvitamin D over the last years has led reagent manufacturers to market different automated and semi-automated methods, that being unfortunately not fully harmonized, yield different results. Liquid chromatography coupled to tandem mass spectrometry has more recently been introduced. This approach allows the distinction between the two forms of 25-hydroxyvitamin D and to measure other metabolites. This approach also requires harmonization to curtail the differences between the different analytical methods. To meet this requirement, the American national institutes of health (NIH), the CDC (Center for disease control and prevention) in Atlanta, the NIST (National institute of standards and technology) and the vitamin D Reference laboratory of Ghent University have pooled their expertise to develop a standardization program. This article reviews the main elements and the difficulties of the automated and semi-auto...

The purposes of this experiment were to determine the relative concentrations of HCl and NaOH; standardize NaOH using 99.9% pure KHP as the primary standard; and, to determine the acetic acid content in Silver Swan™ Sukang Puti, by applying the principles of titration and titrimetric analysis. Using two drops of phenolphthalein as the indicator, acid-to-base and base-to-acid ratios were determined by titrating prepared NaOH solution to the prepared HCl solution, of unknown concentrations. Then, the NaOH solution was standardized using KHP. Lastly, the vinegar was titrated with NaOH to determine its acetic acid content. About 0.11M NaOH and 0.09M HCl were calculated. According to the manufacturer’s information, the said vinegar should contain 4.5% w/v acetic acid.  However, in this experiment, the generated result was 3.904±0.038%. Using t-Test at 95% confidence level, the results of this experiment were detected with systematic and random errors. The addressed errors and impaired skills were noted and should be improved for the next experiments.

Indole and urea based two organic receptors have been synthesized by an easy synthetic process. These two receptors have strong sensitivity and selectivity for several bio-relevant anions. Receptor 1 and 2 were synthesized from indole-2-carboxylic acid and p-anisidine respectively, which are low cost starting materials. Receptor 1 can selectively sense anions like F(-), OAc(-) and H2PO4(-), while receptor 2 can only sense F(-) and H2PO4(-). Both receptors are silent toward anions like Cl(-), Br(-), I(-) and NO3(-). It is the difference in their shape and size which are responsible for different anion sensing. The nature of these host-guest type interactions was analyzed by convenient spectrophotometric techniques like UV-Vis, fluorescence, (1)H NMR, FT-IR studies and also confirmed by electrochemical techniques like cyclic voltammetry studies of the two ligand receptors with convenient anions. Between receptor 1 and 2, receptor 2 was crystallographically characterized also.

Lentiviral vectors have emerged over the last decade as powerful, reliable and safe tools for stable gene transfer in a wide variety of mammalian cells. Unlike other vectors derived from oncoretroviruses, they allow for stable gene delivery into most nondividing primary cells, including neurons. This is why LVs are becoming the most useful and promising tools in the field of neuroscience, not only for research, but also for future gene and cell therapy approaches. Lentivectors (LVs) derived from HIV-1 have gradually evolved to display many desirable features aimed at increasing both their safety and their versatility. These latest designs are reviewed in this unit. This unit also describes protocols for production and titration of LVs that can be implemented in a research laboratory setting, with an emphasis on standardization to improve transposability of results between laboratories.

Human purine nucleoside phosphorylase (HsPNP) is a target for inhibitor development aiming at T-cell immune response modulation. In this work, we report the development of a new set of empirical scoring functions and its application to evaluate binding affinities and docking results. To test these new functions, we solved the structure of HsPNP and 2-mercapto-4(3H)-quinazolinone (HsPNP:MQU) binary complex at 2.7 Å resolution using synchrotron radiation, and used these functions to predict ligand position obtained in docking simulations. We also employed molecular dynamics simulations to analyze HsPNP in two conditions, as apoenzyme and in the binary complex form, in order to assess the structural features responsible for stability. Analysis of the structural differences between systems provides explanation for inhibitor binding. The use of these scoring functions to evaluate binding affinities and molecular docking results may be used to guide future efforts on virtual screening focused on HsPNP.

A new rhodamine-derived Schiff base ( RS) was synthesized and its sensing property to metal ions was investigated by UV/vis and fluorescence spectroscopies. Addition of Hg 2+ ions to the aqueous solution of RS gave a visual color change as well as significantly fluorescent enhancement, while other ions including Pb 2+, Cd 2+, Cr 3+, Zn 2+, Cu 2+, Fe 2+, Co 3+, Ni 2+, Ca 2+, Mg 2+, K + and Na + ions did not induce any distinct color/spectral changes, which constituted a Hg 2+-selective fluorescent OFF- ON chemosensor. The Hg 2+-induced ring-opening of spirolactam of rhodamine in RS resulted in the dual chromo- and fluorogenic observation.