Detection of Amadori compounds by capillary electrophoresis coupled to tandem mass spectrometry

Capillary electrophoresis coupled to mass spectrometry (CE-MS) is reported for the first time as an alternative and powerful analytical method for the characterization and monitoring of N-substituted 1-amino-1-deoxyketoses (Amadori compounds). It allows rapid separation and identification of Amadori compounds, while benefiting from the well-known advantages of MS, such as specificity and sensitivity. Amadori compounds of several amino acids, such as glycine, valine, isoleucine, methionine, proline, and phenylalanine, as well as a cysteine-derived compound, were separated and/or discriminated using CE-MS/MS under standard conditions. The technique may also be useful to study the stability and degradation kinetics of other labile charged Maillard intermediates that play an important role in food and medical science.     

Enzyme activity electrophoresis and rocket immunoelectrophoresis for the qualitative and quantitative analysis of Geotrichum candidum lipase activity

The development and application of a rocket immunoelectrophoretic and an enzyme activity electrophoretic assay for the qualitative analysis of Geotrichum candidum lipase activity is presented. The sensitivities of the four assays were (in arbitrary units): enzyme activity electrophoresis, 1-0.5; rocket immunoelectrophoresis, 0.5-0.2; radial diffusion, 1; titrimetry, 1. The electrophoretic methods made it possible to distinguish between high and low molecular weight forms of the G. candidum lipases. The enzyme activity electrophoretic methods can be combined with other electrophoretic techniques, as demonstrated here with isoelectric focusing, and produce useful information on physico-chemical differences between different molecular forms of the lipase, e.g. forms with different pI.     

Forwards and backwards – synthesis of Laurencia natural products using a biomimetic and retrobiomimetic strategy incorporating structural reassignment of laurefurenynes C–F

Laurefurenynes C–F are four natural products isolated from Laurencia species whose structures were originally determined on the basis of extensive nuclear magnetic resonance experiments. On the basis of a proposed biogenesis, involving a tricyclic oxonium ion as a key intermediate, we have reassigned the structures of these four natural products and synthesized the four reassigned structures using a biomimetic approach demonstrating that they are the actual structures of the natural products. In addition, we have developed a synthesis of the enantiomers of the natural products laurencin and deacetyllaurencin from the enantiomer of (E)-laurefucin using an unusual retrobiomimetic strategy. All of these syntheses have been enabled by the use of tricyclic oxonium ions as pivotal synthetic intermediates.

The synthesis and structural reassignment of laurefurenynes C–F has been achieved, with the new structures fitting with a proposed biosynthesis. Also reported is the synthesis of ent-laurencin and ent-deacetyllaurencin via a retrobiomimetic approach.     

Optimal linear estimators of the unknown mean of a random field observed on a cross

Explicit formulas of minimum-variance linear unbiased estimators of the unknown mean are derived for homogeneous random fields with correlation functions observed on the set (a cross).Translated from Vychislitel'naya i Prikladnaya Matematika, No. 64, pp. 116–121, 1988.     

Sequencing and four-state minisatellite variant repeat mapping of the D1S7 locus (MS1) by fluorescence detection

Minisatellite variant repeat mapping by polymerase chain reaction (MVR-PCR) reveals an enormous degree of variation in the human minisatellite regions. The original approach involved the use of 32P-labelled probes to detect the MVR-PCR products generated. To date, the loci mapped include D1S8, D7S21 and D16S309. However, the most polymorphic locus, D1S7 (MS1), which has been used in forensic analysis, has presented technical difficulties, initially due to its short 9 bp repeats that are much shorter than any conventional primer sequences. This was overcome by using the method of "wrapping around" primers employing inosine at the redundancy position. The difficulty of cloning highly repetitive DNA was overcome by utilising specialised competent SURE cells. We report the cloning and sequencing of selected short MS1 alleles to determine the variety of repeat types. This survey revealed nine types, four of which represented greater than 80% of the sequenced repeats. The reported MVR-PCR system maps the MS1 locus for these four common repeat types by fluorescence detection.     

Undersampled Windowed Exponentials and Their Applications

We characterize the completeness and frame/basis property of a union of under-sampled windowed exponentials of the form

$$ {\mathcal{F}}(g): =\bigl\{ e^{2\pi i n x}: n\ge 0\bigr\} \cup \bigl\{ g(x)e^{2\pi i nx}: n< 0\bigr\} $$

for \(L^{2}[-1/2,1/2]\) by the spectra of the Toeplitz operators with the symbol \(g\). Using this characterization, we classify all real-valued functions \(g\) such that \({\mathcal{F}}(g)\) is complete or forms a frame/basis. Conversely, we use the classical non-harmonic Fourier series theory to determine all \(\xi \) such that the Toeplitz operators with the symbol \(e^{2\pi i \xi x}\) is injective or invertible. These results demonstrate an elegant interaction between frame theory of windowed exponentials and Toeplitz operators. Finally, we use our results to answer some open questions in dynamical sampling, and derivative samplings on Paley-Wiener spaces of bandlimited functions.

     

Systematic Investigation of Silver–Carbon Bonding in Coordination Frameworks with Aryl Ligands That Contain Ethynyl and Ethenyl Substituents

Single‐crystal X‐ray diffraction of a series of ten crystalline silver(I)–trifluoroacetate complexes that contained designed ligands, each of which was composed of an aromatic system that was functionalized with terminal and internal ethynyl groups and a vinyl substituent, provided detailed information on the influence of ligand disposition and orientation, coordination preferences, and the co‐existence of different types of silver(I)–carbon bonding interactions (silver–ethynide, silver–ethynyl, silver–ethenyl, and silver–aromatic) on the construction of coordination networks that were consolidated by argentophilic and weak inter/intramolecular interactions. The complex Ag L10? 6 AgCF₃CO₂ ? H₂O ? MeOH ( HL10 =1‐{[4‐(prop‐2‐ynyloxy)‐3‐vinylphenyl]ethynyl}naphthalene) is the first reported example that exhibits all four kinds of silver(I)–carbon bonding interactions in the solid state.     

Zethrene and Dibenzozethrene: Masked Biradical Molecules?

The syntheses, structures, and physical properties of dibenzozethrenes were explored. The results thus obtained were compared with those for zethrenes. Dibenzozethrenes were synthesized by the nickel‐catalyzed cyclodimerization of 9‐ethynyl‐1‐iodoanthracenes. The substituents in zethrene and dibenzozethrene twisted their backbones, and remarkably influenced their properties. Unlike closed‐shell disubstituted derivatives, the parent zethrene and dibenzozethrene are singlet open‐shell biradicals, which were studied by variable‐temperature ¹H NMR, ESR, SQUID and computational methods. Since substituents were observed to affect significantly the biradical properties, the relevant mechanisms were analyzed. The nonlinear optical performance of each of these compounds depends on its π‐conjugation and biradical properties. Dibenzozethrenes have larger two‐photon absorption cross‐sections than zethrenes, as most strongly evidenced by the parent dibenzothrene [σ_max=4323 GM at 530 nm].     

Detection and quantized conductance of neutral atoms near a charged carbon nanotube

We describe a novel single atom detector that uses the high electric field surrounding a charged single-walled carbon nanotube to attract and subsequently field-ionize neutral atoms. A theoretical study of the field-ionization tunneling rates for atomic trajectories in the attractive potential near a nanowire shows that a broadly applicable, high spatial resolution, low-power, neutral-atom detector with nearly 100% efficiency is realizable with present-day technology. Calculations also show that the system can provide the first opportunity to study quantized conductance phenomena when detecting cold neutral atoms with mean velocities less than 15 m/s.