Assignment of oxime and hydrazone configuration using 1H‐15N and 13C‐15N coupling measurements at natural abundance

Measurement of ¹H‐¹⁵N and ¹³C‐¹⁵N coupling constants at natural abundance is demonstrated to be a reliable and generic method to determine the configuration of oximes, hydrazines, and related systems. Data on ¹H‐¹⁵N and ¹³C‐¹⁵N coupling constants on a variety of systems obtained at natural abundance confirm the geometric dependence of the measured ¹H‐¹⁵N and ¹³C‐¹⁵N coupling constants. In addition, we summarize a simple “decision‐tree” for determining configuration based on practical considerations of sample quantity, solubility, and complexity. Copyright © 2016 John Wiley & Sons, Ltd.     

Template-grown metal nanowires

The growth of metal nanowires using membranes as hard templates is reviewed. The method provides access to arrays of single-crystal metal nanowires and to quasi-one-dimensional metal nanostructures with controlled compositional variation along their length. Recent applications of these kinds of nanowires to problems in superconductivity, optical spectroscopy and sensing, and catalytic conversion of chemical to mechanical energy are reviewed.     

Catalytic micropumps: microscopic convective fluid flow and pattern formation

As innovations continue to be made in the fields of microfluidics and the colloidal assembly, new strategies for moving particles and fluids may be needed. Heterogeneous catalysis provides means of locally converting the stored chemical energy of fuels to mechanical energy. We report an ambient temperature stationary "pump" that generates a proton concentration gradient through the bipolar electrochemical decomposition of hydrogen peroxide on patterned silver-gold surfaces. The resulting electric field drives convective fluid flow and pattern formation of colloidal tracer particles at the microscopic level by a combination of electroosmotic and electrophoretic forces.     

Certification of fat-soluble vitamins,carotenoids, and cholesterol in human serum: Standard reference material 968b

In Standard Reference Material 968b, fat-soluble vitamins and cholesterol in human serum, certified values are provided for cholesterol, retinol, retinyl palmitate, -tocopherol, trans--carotene, total -carotene (trans plus cis isomers), total -carotene, and lutein. Non-certified values are also reported for -tocopherol (includes -tocopherol), -tocopherol, zeaxanthin, -cryptoxanthin, trans-lycopene, trans-lycopene, trans--carotene, total lycopene, 9-cis-carotene, 13- plus 15-cis--carotene, and 15-cis--carotene. Both certified and non-certified values are based on the agreement among results from three different liquid chromatographic analytical procedures developed at NIST and from an interlaboratory comparison exercise among institutions that participate in a NIST-managed Micronutrients Measurement Quality Assurance Program. Cholesterol is certified in this material using the NIST isotope dilution/mass spectrometric definitive method.     

Measurement of imidazoleacetic acid in urine by gas chromatography-mass spectrometry

Imidazoleacetic acid (IAA), a histamine and histidine metabolite, was quantified in human urine by gas chromatography-mass spectrometry (GC-MS). The acid was separated by ion-exchange chromatography, derivatized as the n-butyl ester with boron trifluoride-butanol and the derivative extracted with chloroform. GC-MS analysis was carried out by selected-ion monitoring of ions m/z 81 and m/z 83 corresponding, respectively, to IAA and [15N,15N']IAA used as internal standard. The mean IAA content in urine was about 8.02 nmol/mg of creatinine. The specificity of measurement was rigorously established by GC retention time, peak shape, ion abundance ratios, and recovery experiments. The method is capable of quantifying IAA in 0.05 ml of urine and in amounts as low as 0.20 nmol.     

A review of the DNA standard reference materials developed by the National Institute of Standards and Technology

The Standard Reference Materials Program at the US National Institute of Standards and Technology (NIST) has three human DNA standard reference materials (SRM 2390, SRM 2391a, and SRM 2392) currently available¹ (Orders and requests for information concerning these SRMs should be directed to the Standard Reference Materials Program, National Institute of Standards and Technology, 100 Bureau Drive, Stop 2321, Gaithersburg, MD 20899-2321, Telephone (301) 975-6776, FAX: (301) 948-3730.) [1, 2]. Both the DNA profiling SRM 2390 and the polymerase chain reaction (PCR)-based DNA profiling SRM 2391a are intended for use in forensic and paternity identifications, for instructional law enforcement, or for non-clinical research purposes and are not intended for clinical diagnostics. The mitochondrial DNA (mtDNA) SRM 2392 is to provide standardization and quality control when performing PCR and sequencing any segment or the entire 16,569 base pairs that comprise human mitochondrial DNA. SRM 2392 is designed for use by the forensic, medical, and toxicological communities for human identification, disease diagnosis or mutation detection.     

Self-chemical ionization of diethylzinc

The self-chemical ionization of diethylzinc is examined by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry and semiempirical molecular orbital calculations. Electron impact of diethylzinc neutral produces the radical cation, C(4)H(15)Zn(+) (m/z x 122), which reacts further with the neutral (C(2)H(5))(2)Zn to give the following product ions: Zn(+) (m/z x 64), C(2)H(5)Zn(+) (m/z x 93), C(4)H(9)Zn(+) (m/z x 121), C(4)H(11)Zn(2)(+) (m/z x 187), and C(6)H(15)Zn(2)(+) (m/z x 215). To determine the structure and pathways for production of these ions, monoisotopic (12)C(4)H(15)(64)Zn(+), (64)Zn(+) and (12)C(2)H(5)(64)Zn(+) were individually isolated and reacted with the neutral background. We also performed semiempirical molecular orbital calculations (ZINDO/1). The molecular orbital calculations and experimental data are consistent in predicting that the ethyl group on the diethylzinc cation carries the positive charge. Copyright 1999 John Wiley & Sons, Ltd.     

Metathesis depolymerization for removable surfactant templates

Current methodologies for the production of meso- and nanoporous materials include the use of a surfactant to produce a self-assembled template around which the material is formed. However, post-production surfactant removal often requires centrifugation, calcination, and/or solvent washing which can damage the initially formed material architecture(s). Surfactants that can be disassembled into easily removable fragments following material preparation would minimize processing damage to the material structure, facilitating formation of templated hybrid architectures. Herein, we describe the design and synthesis of novel cationic and anionic surfactants with regularly spaced unsaturation in their hydrophobic hydrocarbon tails and the first application of ring closing metathesis depolymerization to surfactant degradation resulting in the mild, facile decomposition of these new compounds to produce relatively volatile nonsurface active remnants.     

The effect of relaxation on the epitope mapping by saturation transfer difference NMR

The effect of longitudinal relaxation of ligand protons on saturation transfer difference (STD) was investigated by using a known binding system, dihydrofolate reductase and trimethoprim. The results indicate that T1 relaxation of ligand protons has a severe interference on the epitope map derived from a STD measurement. When the T1s of individual ligand protons are distinctly different, STD experiments may not give an accurate epitope map for the ligand-target interactions. Measuring the relaxation times prior to mapping is strongly advised. A saturation time shorter than T1s is suggested for improving the potential epitope map. Reduction in temperature was seen to enhance the saturation efficiency in small to medium size targets.     

perpendicular organization of macromolecules: synthesis and alignment studies of a soluble poly(iptycene)

We describe herein a polymeric material that prefers to align perpendicular to a stretch-aligned polymer host in the solid state. Poly(iptycene) poly-1 was synthesized from monomer 1 under hyperbaric techniques via a Diels-Alder polymerization. Polarized excitation spectra of the anthracene end groups in this material in a stretch-aligned, solution-cast poly(vinyl chloride) (PVC) film showed that the poly(iptycene) prefers to align normal (counter aspect ratio) to the stretching direction of the PVC. This is explained by a "threading" mechanism, whereby the PVC intercalates through the internal free volume presented by poly-1, similar to effects observed in small molecule iptycenes under similar conditions.