The use of the method of continuous variation for the classification of complexes with mole ratio 1:1

It is shown theoretically and experimentally that curves of continuous variation may be used to classify complexes of the form A_mB_n for which $\text{m}\text{n}$ = 1, into two different groups: one group comprises complexes for which m = n = 1, and another group contains those for which m = n > 1.The system iron(III)-chrome azurol S was used to demonstrate the applicability of the method.     

A new and practical PIFA-promoted olefin amidohydroxylation: six- versus five-membered ring formation

A novel access to the isoindolinone and isoquinolin-2-one skeletons from adequately substituted aromatic precursors is described. The key intramolecular cyclization step was performed by the action of phenyliodine(III)bis(trifluoroacetate) (PIFA) on the corresponding vinyl or allyl substituted N-(p-methoxyphenyl)benzamide derivatives leading to the heterocyclic compounds through 5-exo-trig and 6-exo-trig processes, respectively.     

The HLA-A2-supermotif: a QSAR definition

Identification of epitopes capable of binding multiple HLA types will significantly rationalise the development of epitope-based vaccines. A quantitative method assessing the contribution of each amino acid at each position was applied to over 500 nonamer peptides binding to 5 MHC alleles--A*0201, A*0202, A*0203, A*0206 and A*6802--which together define the HLA-A2-like supertype. FXIGXI (L)IFV was identified as a supermotif for the A2-supertype based on the contributions of the common preferred amino acids at each of the nine positions. The results indicate that HLA-A*6802 is an intermediate allele standing between A2 and A3 supertypes: at anchor position 2 it is closer to A3 and at anchor position 9 it is nearer to A2. Models are available free on-line at http://www.jenner.ac.uk/MHCPred and can be used for binding affinity prediction.     

Mixing with bubbles: a practical technology for use with portable microfluidic devices

This paper demonstrates a methodology for micromixing that is sufficiently simple that it can be used in portable microfluidic devices. It illustrates the use of the micromixer by incorporating it into an elementary, portable microfluidic system that includes sample introduction, sample filtration, and valving. This system has the following characteristics: (i) it is powered with a single hand-operated source of vacuum, (ii) it allows samples to be loaded easily by depositing them into prefabricated wells, (iii) the samples are filtered in situ to prevent clogging of the microchannels, (iv) the structure of the channels ensure mixing of the laminar streams by interaction with bubbles of gas introduced into the channels, (v) the device is prepared in a single-step soft-lithographic process, and (vi) the device can be prepared to be resistant to the adsorption of proteins, and can be used with or without surface-active agents.     

The mole is not an ordinary measurement unit

In this paper, it is argued that the SI system has not carefully enough taken into account the differences that exist between stoichiometry and physics, and because of this neglect forced the kind-of-quantity amount of substance into a false form. The mole is not a unit such as the metre, the kilogram, and the second. It is a ??unit?? only in the sense in which purely mathematical scaling factors can be called units.     

The definition of core electrons

The traditional separation of electrons in molecules into core and valence types is often based on molecular orbital energies. This method is known to lead in some cases to large relative errors in correlated calculations. Instead, we propose a method based on the definition of molecular core character using separation of basis functions into core and valence types. This gives size-consistency to separation of electrons in molecules into core and valence types.     

The use of isotopic centrifugal distortion differences towards a better definition of the molecular harmonic potential function

It is demonstrated that the use of heavy isotopic differences in quartic distortion constant data contributes to a significant improvement in the definition of the empirically determined harmonic potential function of a molecule, provided the data are determined with sufficient precision. Formaldehyde is used as a test case.     

Michael-type addition of hydroxide to alkynylselenonium salt: practical use as a ketoselenonium ylide precursor

A novel synthetic method of ketodiphenylselenonium ylide from alkynylselenonium salt is described. A reaction of alkynylselenonium salt, hydroxide ion, and aldehyde in the presence of silver triflate and triethylamine gave oxiranylketones just as a trans-isomer in moderate to good yields, whereas benzoyl aziridine derivatives were obtained from the reaction with sodium p-toluenesulfonamide instead of a hydroxide ion.     

Methodologies for the practical determination and use of method detection limits

Underwater NaI(T1) and HPGe detectors are used in the environmental measurements programs at the Savannah River Site (SRS). A 22.9 cm × 10.2 cm NaI(T1) detector on the Savannah River continuously monitors effluent releases from both SRS (DOE) and Plant Vogtle (Georgia Power). Correlations with known releases indicate a sensitivity of 4 mBq/l for⁵⁸Co with 1500 min spectra; such levels are well below those of hazardous or legal concern. A 30%-efficient HPGe detector has appraised radionuclides in SRS cooling pond sediments; the dominant gamma-emitting radionuclide detected was¹³⁷Cs, at levels ranging up to 2.0 MBq/m². The pond activities were adequately quantified by 1 min counts with the HPGe detector; resulting contour maps of sediment¹³⁷Cs provided guidance for partially draining the ponds for dam repairs.     

The local definition of the Optimum ascent path on a multi-dimensional potential energy surface and its practical application for the location of saddle points

Density corrected distribution functions are used to calculate γ_o and γ₂ moments for the collision induced absorption spectra of a helium-argon system for a number of assumed dipole moment functions. These calculations indicate that corrections due to density effects can be of greater magnitude than the quantum corrections for these moments and can account for 10% of the moment at 200 amagats. The density corrections for γ_o show great variability with the choice of dipole parameters while the corrections for ν₂ were very consistent irrespective of the precise values of the dipole parameters. In addition, we correct some errors in our previous paper on the formal theory of these moments.     

A validation study on the practical use of automated de novo design

The de novo design program Skelgen has been used to design inhibitor structures for four targets of pharmaceutical interest. The designed structures are compared to modeled binding modes of known inhibitors (i) visually and (ii) by means of a novel similarity measure considering the size and spatial proximity of the maximum common substructure of two small molecules. It is shown that the Skelgen algorithm generates representatives of many inhibitor classes within a very short time and that the new similarity measure is useful for comparing and clustering designed structures. The results demonstrate the necessity of properly defining search constraints in practical applications of de novo design.     

The iterative synthesis of discrete dimethylsiloxane oligomers: A practical guide

Discrete dimethylsiloxane oligomers are interesting building blocks for the synthesis of high χ–low N block co-oligomers (BCOs) forming highly organized nanostructures. Here, a practical guide to the synthesis of molecularly defined oligodimethylsiloxanes (oDMS) from 7-mer to 40-mer via a linear growth strategy is described. The iteration of a hydroxylation reaction and the condensation of mono- or bifunctional hydroxysiloxanes with chloro-octamethyltetrasiloxane results in asymmetric and symmetric siloxanes, respectively. The synthesis contains critical washing and purification steps to remove minor amounts of low and high-molecular weight byproducts, which are detected using Fourier transform infrared spectrometry, gas chromatography–mass spectrometry, and size-exclusion chromatography. The oligomers are obtained on a multigram scale in yields of 94–50% and in high purity with only one molar mass detected. The formation of the chloride, hydroxide or hydride functional groups is adequately analyzed using ²⁹Si NMR spectroscopy. The hydride terminated siloxane oligomers are used in Karstedt catalyzed hydrosilylation reactions with alkene-functional substrates to obtain oDMS-based oligomers and BCOs. Byproduct formation as a result of isomerization and reduction are followed by ¹H NMR spectroscopy and minimized using dry conditions and low-catalyst loadings.     

Neutral-carrier-type potassium ion-selective electrodes based on polymer-supported liquid-crystal membranes for practical use.

Polymer-supported liquid-crystal membranes have been designed for neutral-carrier-type potassium ion-selective electrodes, aiming for practical applications of high-performance liquid-crystalline membrane ion sensors. Two types of polymer-supported liquid-crystal membranes were tested for their usefulness; one is microporous poly(tetra fluoroethylene) (PTFE) membranes impregnated by thermotropic liquid-crystalline compounds, and another is poly(methyl methacrylate) (PMMA) membrane dispersing the same liquid-crystalline compounds. Both of the polymer-supported liquid-crystal membranes containing a liquid-crystalline benzo-15-crown-5 neutral carrier as well as a lipophilic anion excluder work well as ion-sensing membranes for potassium ion-selective electrodes, the ion selectivities of which can be switched by the measurement temperatures. Specifically, PTFE-impregnated liquid-crystal membranes are better than the PMMA-dispersed ones in the sensitivity and selectivity of the resulting ion electrodes. A potassium ion assay in blood sera has proved that neutral-carrier-type ion-selective electrodes based on the polymer-supported liquid-crystal membranes are reliable for practical uses.     

New practical tools for the implementation and use of ultrafast 2D NMR experiments

Ultrafast (UF) 2D NMR is a very promising methodology enabling the acquisition of 2D spectra in a single scan. In the last few years, the analytical performance of UF 2D NMR has been highly increased, consequently maximizing its range of applications. However, its implementation and use by non‐specialists are far from being straightforward, because of the specific acquisition and processing procedures and parameters characterizing UF NMR. To make this methodology implementable and applicable by non‐specialists, we developed a simple routine capable of translating conventional parameters (spectral widths and transmitter frequencies) into specific UF parameters (gradient and chirp pulse parameters). This macro was subsequently implemented in a Web page, which is available for external users. Although the algorithm was designed for two widely used 2D experiments, COSY and HSQC, it can easily be extended to any other pulse sequence. The robustness of this routine was verified successfully on a variety of small molecules. We believe that this tool will eliminate much of the technical difficulties related to UF 2D NMR and will make the technique accessible to a wider audience of organic and analytical chemists. Copyright © 2013 John Wiley & Sons, Ltd.     

A practical and inexpensive ‘convertible’ isonitrile for use in multicomponent reactions

N-tert-Butylamides are readily converted into the corresponding carboxylic acids by simple nitrosation. The process, which occurs under mild nonaqueous conditions, leaves carboxylic esters untouched and transforms multicomponent reaction products into useful building blocks for further synthetic elaboration.     

Homogeneity of solids: A proposal for quantitative definition

A simple formula has been deduced to predict the detectability of chemical homogeneity of solid substances by use of an analytical method with known spatial resolution. The formula includes the ratio of the spatial resolution of the method to the spatial distribution of the component to be determined, and the standard deviation of the method.