Screening method for the addition of bovine blood-based binding agents to food using liquid chromatography triple quadrupole mass spectrometry

We report the development of a qualitative method to detect the addition of blood-based binding agents to food products. The method is based on the detection of species-specific marker peptides, fibrinopeptides, released from the blood protein fibrinogen during gelling of the blood protein by thrombin. The fibrinopeptides were isolated from foods spiked with commercial bovine binding agent by acid precipitation followed by enrichment using solid-phase extraction and analysed by liquid chromatography electrospray ionisation triple quadrupole mass spectrometry. Fibrinopeptide A was found to be an effective marker in fresh, processed and cooked food matrices spiked with 5% (v/w) bovine binding agent.     

A tool for real-time acoustic species identification of delphinid whistles

The ability to identify delphinid vocalizations to species in real-time would be an asset during shipboard surveys. An automated system, Real-time Odontocete Call Classification Algorithm (ROCCA), is being developed to allow real-time acoustic species identification in the field. This Matlab-based tool automatically extracts ten variables (beginning, end, minimum and maximum frequencies, duration, slope of the beginning and end sweep, number of inflection points, number of steps, and presence/absence of harmonics) from whistles selected from a real-time scrolling spectrograph (ISHMAEL). It uses classification and regression tree analysis (CART) and discriminant function analysis (DFA) to identify whistles to species. Schools are classified based on running tallies of individual whistle classifications. Overall, 46% of schools were correctly classified for seven species and one genus (Tursiops truncatus, Stenella attenuata, S. longirostris, S. coeruleoalba, Steno bredanensis, Delphinus species, Pseudorca crassidens, and Globicephala macrorhynchus), with correct classification as high as 80% for some species. If classification success can be increased, this tool will provide a method for identifying schools that are difficult to approach and observe, will allow species distribution data to be collected when visual efforts are compromised, and will reduce the time necessary for post-cruise data analysis.     

Influence of ligand electronic effects on the structure of monovalent cobalt complexes

The syntheses, spectroscopic properties, and structures of the monovalent cobalt complexes, [PhTt (tBu)]Co(L), 1-L {PhTt (tBu) = phenyltris[( tert-butylthio)methyl]borate; L = PPh 3, PMe 3, PEt 3, PMe 2Ph, PMePh 2, P(OPh) 3, CNBu (t)}, are described. Complexes 1-L are prepared via the sodium amalgam reduction of [PhTt (tBu)]CoCl in the presence of L. The complexes display magnetic moments and paramagnetically shifted (1)H NMR spectra consistent with triplet, S = 1, ground states. The molecular geometries, determined by X-ray diffraction methods, reveal that some of the complexes display structures in which the L donor is moved off of the inherent 3-fold axis. In the most extreme cases (e.g., 1-P(OPh) 3 or 1-CNBu ( t )), the geometries can be described as cis-divacant octahedra. The origin of the geometric distortions is a consequence of the electronic characteristics of L as first deduced by Detrich et al. for [Tp (Np)]Co(L) ( J. Am. Chem. Soc. 1996, 118, 1703). The results establish a linear correlation between the magnitude of the structural distortion and the electronic parameter of the phosphine donor.     

Helicates, boxes, and polymers from simple pyridine-alcohol ligands: the impact of the identity of the transition metal ion

The coordination chemistry of 6-methylpyridine-2-methanol (1) and enantiopure (R)-1-(6-methylpyridin-2-yl)ethanol (2) with a range of divalent first-row transition metal salts has been investigated in an effort to determine whether hydrogen-bonded helicates will form, as observed for cobalt(II) salts. Hydrogen-bonded helicates, [Cu2(1)2(1-H)2X2] (X = Cl, Br), were only observed upon combining 1 with CuCl2 and CuBr2 in MeOH solution. Other metal salts led to alternative products, viz. Cu(ClO4)2 in the presence of base gives [Cu2(1)2(1-H)2](ClO4)2, ZnCl2 and ZnBr2 give the 1-D helical coordination polymers [Zn(1-H)Cl]infinity and [Zn(1-H)Br]infinity, a mixture of NiCl2 and Ni(OAc)2 produces the [Ni4(1-H)4Cl2(OAc)2(MeOH)2] cubane, NiCl2 leads to the [Ni4(1-H)4Cl4(MeOH)4] cubane, while MnCl2 gives the known cubane [Mn4(1-H)6Cl4]. The reaction of 2 with CuCl2 produces the mononuclear complex Lambda-[Cu(2)2Cl]Cl, while reaction with CuBr2 leads to a dimer, Lambda,Lambda-[Cu2(2)3(2-H)Br2]Br, which is held together by a single hydrogen bond between the monomeric subunits. The solid-state CD spectra of these latter complexes were recorded and found to be very similar. The temperature-dependent magnetic behavior of [Cu2(1)2(1-H)2X2] (X = Cl, Br), [Cu2(1)2(1-H)2](ClO4)2, [Cu2(2)3(2-H)Br2]Br, and [Ni4(1-H)4Cl2(OAc)2(MeOH)2] was investigated. Weak antiferromagnetic coupling between the copper(II) centers is mediated by the hydrogen bonds in the [Cu2(1)2(1-H)2X2] (X = Cl, Br) complexes.     

Trichromophoric systems from square-planar Pt-ethynylbipyridine and octahedral Ru- and Os-bipyridine centers: syntheses, structures, electrochemical behavior, and bipartition of energy transfer

The synthetic approach, electrochemical behavior, and optical absorption and emission properties are reported of the Pt-bipyridine-acetylide/Ru-bipyridine complex [(dbbpy)Pt{(ebpy)Ru(bpy) 2} 2] (4+), PtRu 2, the Pt-bipyridine-acetylide/Os-bipyridine analogue, PtOs 2, and the Pt/Ru/Os complex [(dbbpy)Pt(ebpy) 2Ru(bpy) 2Os(bpy) 2] (4+), PtRuOs; ebpy is 5-ethynylbpy, dbbpy is 4,4'-ditertiobutylbpy, and bpy is 2,2'-bipyridine. These triads are investigated in acetonitrile solvent by comparing their electrochemical and spectroscopic properties with those of the mononuclear species [(dbbpy)Pt(ebpy) 2], Pt, [Ru(ebpy)(bpy) 2] (2+), Ru, and [Os(ebpy)(bpy) 2] (2+), Os. Results of X-ray analysis of Pt are reported, which show the planar arrangement of this unit that features two free bpy sites. The absorption spectra of the triads and the mononuclear species show that light at 452 or 376 nm can be employed to observe luminescence spectra of these complexes; for the observation of emission lifetimes, nanoled sources at 465 and 373 nm are employed. With lambda exc = 452 (and 465) nm, one selectively produces Ru --> bpy/ebpy CT (RuLCT) or Os --> bpy/ebpy CT states (OsLCT); MLCT is a metal-to-ligand charge-transfer. With lambda exc = 376 (and 373) nm, one populates Pt --> dbbpy CT and intraligand charge transfer (ILCT, involving the ebpy fragment) levels, in addition to Ru(II)- or Os(II)-centered excited states, in aliquots that are estimated from comparison of the absorption features of the components. Upon excitation with light at 376 (and 373) nm, the optical studies of PtRu 2, PtOs 2, and PtRuOs reveal full quenching of the Pt-based emission and occurrence of efficient photoinduced energy transfer, leading to exclusive MLCT emission from the ruthenium and osmium centers. In particular, PtRuOs is found to exhibit a Ru- and Os-based dual luminescence, whose intensities ratio is consistent with a Pt --> Os intramolecular energy transfer step being 3-6 times faster than the Pt --> Ru one.     

Calculation of residual dipolar couplings from disordered state ensembles using local alignment

Residual dipolar couplings (RDCs) have been observed in disordered states of several proteins. While their nonuniform values were initially surprising, it has been shown that reasonable approximation of experimental RDCs can be obtained using simple statistical coil models and assuming global alignment of each structure, provided that many thousands of conformers are averaged. Here we show that, by using short local alignment tensors, we can achieve good agreement between experimental and simulated RDCs with far fewer structures than required when using global alignment. This makes the possibility of using RDCs as direct restraints in structural calculations of disordered proteins much more feasible. In addition, it provides insight into the nature of RDCs in disordered states, suggesting that they are primarily reporting on local structure.     

Oxygen atom transfer from nitrite mediated by Fe(III) porphyrins in aqueous solution

Aqueous solutions of the iron(III) porphyrin complex FeIII(TPPS) (1, TPPS = tetra(4-sulfonatophenyl)-porphyrinato) and nitrite ion react with various substrates S to generate the ferrous nitrosyl complex FeII(TPPS)(NO) (2) plus oxidized substrate. When S is a water-soluble sulfonated phosphine, the product is the resulting monoxide. When air is introduced to the product solutions, 2 is rapidly reoxidized to 1; however, even in the absence of air, there is a slow regeneration of the ferric species with concomitant production of nitrous oxide. Thus, in an anaerobic aqueous environment, FeIII(TPPS) catalyzes oxygen atom transfer from nitrite ion to substrates with the eventual formation of N2O.     

A simple method to prepare single isomer tetrasubstituted olefins by successive Suzuki–Miyaura cross-couplings of E-β-chloro-α-iodo-α,β-unsaturated esters

A convenient method of synthesizing tetrasubstituted olefins as single isomers is described. E-β-Chloro-α-iodo-α,β-unsaturated esters are first converted into the corresponding E-β-chloro-α,β-unsaturated esters using Suzuki–Miyaura coupling reactions with arylboronic acids and alkenylboronic acids. These transformations gave complete selectivity, and proceeded with substitution at the more activated α-iodide position. These compounds, isolated as single isomers, were then transformed into tetrasubstituted olefins by Suzuki–Miyaura couplings with arylboronic acids, alkenylboronic acids, and alkyl boranes to afford the corresponding tetrasubstituted olefins as single isomers. During this coupling process, it was discovered that the use of small ligands, such as PMe₃ or PEt₃, was critical for efficient coupling. The stereochemistry and regiochemistry of the products were unequivocally established using NMR methods.     

Round-robin evaluation of a solid-phase microextraction-gas chromatographic method for reliable determination of trace level ethylene oxide in sterilized medical devices

Medical devices that are sterilized with ethylene oxide (EtO) retain small quantities of EtO residuals, which may cause negative systemic and local irritating effects, and must be accurately quantified to ensure non-toxicity. The goal of this round-robin study is to investigate the capability of a novel solid-phase microextraction-gas chromatographic (SPME-GC) method for trace-level EtO residuals analysis: three independent laboratories conducted a guided experiment using this SPME-GC method, in assessing method performance, ruggedness and the feasibility of SPME fibers. These were satisfactory across the independent laboratories, at the 0.05-5.00 ppm EtO range. This method was then successfully applied to analyze EtO residuals in several sterilized/aerated medical devices of various polymeric composition, reliably detecting and quantifying the trace levels of EtO residuals present ( approximately 0.05 ppm EtO). SPME is a feasible alternative for quantifying trace-level EtO residuals in sterilized medical devices, thereby lowering the limit of quantification (LOQ) by as much as two to three orders of magnitude over the current GC methodology of direct liquid injection.     

A phosphine-mediated through-space exchange coupling pathway for unpaired electrons in a heterobimetallic lanthanide-transition metal complex

The reaction of P(CH2OH)3 with methyl anthranilate NH2C6H4-2-CO2Me produced the ligand precursor P(CH2NHC6H4-2-CO2Me)3 (1). The reaction of 1 with [Y{N(SiMe3)2}3] produced hexadentate yttrium complex [Y{P(CH2NC6H4-2-CO2Me)3}] (2), in which the metal centre is coordinated by three amido donors and the three carbonyl oxygen atoms of the ester groups. The 31P{1H} NMR spectrum features 1J Y,P=15 Hz, and DFT calculations demonstrate that through-space interaction between the minor lobe of the phosphine lone pair and the yttrium centre allows a large Fermi contact contribution to this spin coupling constant. The EPR spectrum of the analogous paramagnetic Gd complex [Gd{P(CH2NC6H4-2-CO2Me)3}] (3) can be modelled by using a B20 crystal field parameter of +/-0.19 cm(-1). Heterodinuclear complexes were prepared by the reactions of 1 and 3 with [5,10,15,20-tetrakis(4-methoxyphenyl)porphinato]cobalt(II), by binding of the phosphine lone pair to the d(7) cobalt centre. The solid-state EPR spectrum of the heterodinuclear yttrium complex 4 exhibits large superhyperfine coupling to the phosphorus nucleus, indicative of an S=1/2 complex in which the unpaired electron resides in the cobalt dz2 orbital directed at the phosphine donor. The magnetic susceptibility of the heterodinuclear Gd-Co complex 5 demonstrates that through-space antiferromagnetic coupling occurs between unpaired electrons on the gadolinium and cobalt centres.