The practical synthesis of a novel and highly potent analogue of bryostatin

Macrocycle 1 is a new highly potent analogue of bryostatin 1, a promising anti-cancer agent currently in human clinical trials. In vitro, 1 displays picomolar affinity for PKC and exhibits over 100-fold greater potency than bryostatin 1 when tested against various human cancer cell lines. Macrocycle 1 can be generated in clinically required amounts by chemical synthesis in only 19 steps (LLS) and represents a new clinical lead for the treatment of cancer.     

Probing the Intracellular Glutathione Redox Potential by In‐Cell NMR Spectroscopy

Non‐invasive and real‐time analysis of cellular redox processes has been greatly hampered by lack of suitable measurement techniques. Here we describe an in‐cell nuclear magnetic resonance (NMR) based method for measuring the intracellular glutathione redox potential by direct and quantitative measurement of isotopically labeled glutathione introduced exogenously into living yeast. By using this approach, perturbations in the cellular glutathione redox homeostasis were also monitored as yeast cells were subjected to oxidative stress.     

Quantitative measurements of glutathione in yeast cell lysate using 1H NMR

Methods for quantifying the level of glutathione (GSH) in yeast cell lysate are described using ¹H NMR analysis. For quantification purposes, the ¹H resonances corresponding to the Cys βCH₂ of GSH were identified as having the fewest overlapping spectral interferences from lysate matrix components using GSH spiked yeast lysate samples. Two methods, standard addition based on peak integration and a spectral subtraction approach, were evaluated for quantifying GSH in lysate samples. The peak integration procedure required baseline estimation and a peak fitting step to correct for background interferences while the spectral subtraction procedure was comparatively straightforward. The level of GSH measured by ¹H NMR was in good agreement with the concentration measured by the DTNB-GSSG reductase recycling assay. The proposed NMR method can lead to a reliable quantitation of GSH and could be applicable to a variety of other analytes of interest in complex biological matrices.     

The development and implementation of quality assurance programs to support nutritional measurements

The National Institute of Standards and Technology administers quality assurance programs devoted to improving measurements of nutrients and related metabolites in foods, dietary supplements, and serum and plasma samples. These programs have been developed in collaboration with the National Institutes of Health to assist measurement communities in their efforts to achieve accurate results that are comparable among different laboratories and over time. Targeted analytes include micronutrients, botanical markers, nutritional elements, contaminants, fatty acids, and vitamin D metabolites.     

The role of the CCQM OAWG in providing SI traceable calibrators for organic chemical measurements

Metrological traceability for organic chemical measurements is a documented unbroken chain of calibrations with stated uncertainties that ideally link the measurement result for a sample to a primary calibrator in appropriate SI units (e.g., mass fraction). A comprehensive chemical purity determination of the organic calibrator is required to ensure a true assessment of this result. We explore the evolution of chemical purity capabilities across metrology institute members of the Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology’s Organic Analysis Working Group (OAWG). The OAWG work program has promoted the development of robust measurement capabilities, using indirect “mass balance” determinations via rigorous assessment of impurities and direct determination using quantitative nuclear magnetic resonance spectroscopy methods. A combination of mass balance and qNMR has been shown to provide a best practice approach. Awareness of the importance of the traceability of organic calibrators continues to grow across stakeholder groups, particularly in key areas such as clinical chemistry where activities related to the Joint Committee for Traceability in Laboratory Medicine have raised the profile of traceable calibrators.

     

Evaluation of the state-of-the-art measurement capabilities for selected PBDEs and decaBB in plastic by the international intercomparison CCQM-P114

An international intercomparison involving eight national metrology institutes (NMIs) was conducted to establish their current measurement capabilities for determining five selected congeners from the brominated flame retardant classes polybrominated diphenyl ethers and polybrominated biphenyls. A candidate reference material consisting of polypropylene fortified with technical mixtures of penta-, octa- and decabromo diphenyl ether and decabromo biphenyl, which was thoroughly assessed for material homogeneity and stability, was used as study material. The analytical procedures applied by the participants differed with regard to sample pre-treatment, extraction, clean-up, employed calibrants and type of calibration procedure as well as regarding analytical methods used for separation, identification and quantification of the flame retardant congeners (gas chromatography coupled to an electron capture detector (GC-ECD), gas chromatography-mass spectrometry in the electron ionisation mode (GC-EI-MS), gas chromatography-mass spectrometry in the electron capture negative ionisation mode (GC-ECNI-MS), and liquid chromatography-inductive coupled plasma-mass spectrometry (LC-ICP-MS)). The laboratory means agreed well with relative standard deviations of the mean of means of 1.9%, 4.8%, 5.5% and 5.4% for brominated diphenyl ether (BDE) 47, 183 and 209 and for the brominated biphenyl (BB) congener 209, respectively. For BDE 206, a relative standard deviation of 28.5% was obtained. For all five congeners, within-laboratory relative standard deviations of six measurements obtained under intermediate precision conditions were between 1% and 10%, and reported expanded measurements uncertainties typically ranged from 4% to 10% (8% to 14% for BDE 206). Furthermore, the results are in good agreement with those obtained in the characterization exercise for determining certified values for the flame retardant congeners in the same material. The results demonstrate the state-of-the-art measurement capabilities of NMIs for quantifying representative BDE congeners and BB 209 in a polymer. The outcome of this intercomparison (pilot study) in conjunction with possible improvements for employing exclusively calibrants with thoroughly assessed purity suggests that a key comparison aiming at underpinning calibration and measurement capability (CMC) claims of NMIs can be conducted.

Mass Spectrometric and Photoelectron Spectroscopic Studies of Zirconium Oxide Molecular and Cluster Anions

We present a preliminary report on our mass spectrometric and photoelectron spectroscopic studies of zirconium oxide molecular and cluster anions using a newly built laser vaporization/time-of-flight/magnetic bottle, negative ion photoelectron spectrometer. This work was motivated in part by evidence which suggests that zirconium dioxide catalyzes the radiolysis of interfacial water. We present our mass spectrometric observations of oxygen-rich zirconium oxide cluster anions and our photoelectron spectra of ZrO^– and ZrO ₂ ^– . From the photoelectron spectrum of ZrO^–, the adiabatic electron affinity of ZrO was determined to be 1.3±0.3 eV, and from this value, the dissociation energy of ZrO^– (into Zr and O^–) was found to be 7.8±0.3 eV. From the photoelectron spectrum of ZrO₂, the adiabatic electron affinity of ZrO₂ was determined to be 1.8±0.4 eV.