Rotational spectra of the diastereomers of Soman

The pure rotational spectrum of the nerve agent Soman has been recorded using a pulsed-molecular-beam Fourier-transform microwave spectrometer. The spectrum consists of transitions from two different isomers. The two distinguishable isomers are likely the [SS] (or [RR]) and the [RS] (or [SR]) diastereomers that result from the two chiral centers in the molecule. The rotational constants determined for the A internal rotor states of the [SS, RR] and [RS, SR] isomers are A=1645.39765(9) MHz, B=591.97752(3) MHz, and C=547.58168(3) MHz, and A=1635.0580(1), B=600.14889(6), and C=556.45840(6) MHz, respectively, where type A, k=1 or 1σ standard uncertainties are given. Structural assignments of the diastereomers were made based on comparisons of the calculated electric dipole moments at the MP2/6-311G level of theory with the observed selection rules. Many of the rotational transitions are split into doublets and correspond to the A- and E-state transitions arising from internal rotation of the methyl top attached to the phosphorus atom. These splittings have been used to obtain the V₃ barriers of the methyl groups for both diastereomers. This work is part of an ongoing project aimed at generating a spectral database of chemical agents and related families of compounds.     

Multicomponent water proton transverse relaxation and T2-discriminated water diffusion in myelinated and nonmyelinated nerve

The influence of compartmental boundaries on water proton transverse relaxation and diffusion measurements was investigated in three distinct excised nerves, namely, the non-myelinated olfactory nerve, the Schwann cell myelinated trigeminal nerve, and the oligodendrocyte myelinated optic nerve of the garfish. The transverse relaxation decay curves were multiexponential and their decomposition yielded three primary components with T₂ values 30–50, 150, and 500 ms, which were subsequently assigned to water protons in the myelin, axoplasm, and interaxonal compartments. The short T₂ component was absent in the non-myelinated olfactory nerve, but present in both myelinated nerves and thus provides supporting evidence for the use of quantitative T₂ measurements to measure the degree of myelination. The signal contribution of each T₂ component to the apparent diffusion coefficient measurements was varied by incrementing the spin-echo time with a preparatory CPMG train of radiofrequency pulses. The apparent diffusion coefficient and its anisotropy were shown to be independent of the spin-echo time over the range of 70 to 450 ms.     

用CO_2激光吻合外周神经干的实验研究

使用3WCO_2激光共吻合22只家兔计44支胫后神经干,并设常规显微缝合对照组。术后九周,测定神经传导速度和神经再生观察,均无显著差异。     

Spatial arrangements of dorsal root ganglion cells after sciatic nerve crush

The present study explores 3D spatial arrangements of the A- and B-cells within the fifth lumbar dorsal root ganglion (DRG) of rat in order to test for differences after sciatic nerve crush (SNC). The pair correlation and cross-correlation functions were estimated through counting dipole probes superimposed on DRG sections. The data showed that the A- and B-cells were clustered at distances below 40 and 35 μm in sham-operated animals, respectively. These values were 35 and 25 μm in SNC animals. Beyond these distances, the cells of the control group were arranged neither clustered nor repulsed. The A- and B-cells showed a negative correlation (repulsion) at r = 270–290 μm and r = 100 in SNC ganglions, respectively. The plot of the cross-correlation function showed that the first maximum curve was r = 51 μm and 41 μm in sham-operated and SNC rats, respectively. The other differences were seen at r = 51–61 μm and r = 165 μm between cross-covariance of the cells. The “degree of order” for the A- and B-cells showed no significant difference and the low values of the two groups indicated the random distribution of cells in them.

Conclusion

The obtained data revealed that cellular spatial patterns in the dorsal root ganglion of the sciatic nerve crush were changed.     

Polyelectrolyte functionalized multi-walled carbon nanotubes as strong anion-exchange material for the extraction of acidic degradation products of nerve agents

Extraction, enrichment and gas chromatography mass spectrometric analysis of degradation products of nerve agents from water is of significant importance for verification of Chemical Weapons Convention (CWC) and gathering forensic evidence of use of nerve agents. Multi-walled carbon nanotubes (MWCNTs) were non-covalently functionalized with poly(diallyldimethylammonium chloride) (PDDA) to afford the cationic functionalized nano-tubes, which were used as solid-phase anionic-exchanger sorbents to extract the acidic degradation products of nerve agents from water. Extraction efficiencies of MWCNTs-PDDA were compared with those of mixed mode anion-exchange (HLB) and silica based strong anion-exchange (Si-SAX) cartridges. Optimized extraction parameters included MWCNTs-PDDA 12 mg, washing solvent 5 mL water and eluting solvent 3 mL of 0.1M aqueous HCl followed by 3 mL methanol. At 1 ng mL(-1) spiking concentration of mono- and di-basic phosphonic acids, MWCNTs-PDDA exhibited higher extraction efficiencies in comparison to Si-SAX and HLB. The limits of detection were achieved down to 0.05 and 0.11 ng mL(-1) in selected ion and full scan monitoring mode respectively; and limits of quantification in selected ion monitoring mode were achieved down to 0.21 ng mL(-1).     

Selective enrichment of the degradation products of organophosphorus nerve agents by zirconia based solid-phase extraction

Selective extraction and enrichment of nerve agent degradation products has been achieved using zirconia based commercial solid-phase extraction cartridges. Target analytes were O-alkyl alkylphosphonic acids and alkylphosphonic acids, the environmental markers of nerve agents such as sarin, soman and VX. Critical extraction parameters such as modifier concentration, nature and volume of washing and eluting solvents were investigated. Amongst other anionic compounds, selectivity in extraction was observed for organophosphorus compounds. Recoveries of analytes were determined by GC-MS which ranged from 80% to 115%. Comparison of zirconia based solid-phase extraction method with anion-exchange solid-phase extraction revealed its selectivity towards phosphonic acids. The limits of detection (LOD) and limit of quantification (LOQ) with selected analytes were achieved down to 4.3 and 8.5 ng mL(-1), respectively, in selected ion monitoring mode.     

The slow wave solution to the FitzHugh-Nagumo equations

This paper gives a new existence proof for a travelling wave solution to the FitzHugh-Nagumo equations, u_t = u_xx +f(u)?w, w _t = ? (u?γw). The proof uses a contraction mapping argument, and also shows that the solution (u, c, w) to the travelling wave equations, where c is the wave speed, converges as ? → 0⁺ to the solution to the equations having ?=0, c=0, and w=0.     

Synthese des vermuteten Nervenwachstumsfaktor-Aktivzentrums

The synthesis of an unsymmetrical cystine peptide corresponding to the sequence 10–25/75–88 of mouse nerve growth factor was performed via the newly developed sulfenohydrazide procedure. The triacontapeptide isolated at a high degree of purity after Sephadex-LH 20 chromatography, did not exhibit in the biological assays the expected nerve growth factor activity as reported byRevoltella and coworkers.

Auszugsweise vorgetragen am 8. Amer. Peptid Symposium, Tucson (1983)¹ und am 18. Europ. Peptid Symposium, Djurönäset (1984)².     

Microsynthesis and electron ionisation mass spectrometric analysis of chemical weapons convention (CWC)-related O,O-dialkyl-N,N-dialkylphosphoramidates

The paper describes microsynthesis and GC/EIMS analysis of O,O-dialkyl-N,N-dialkylphosphoramidates (DADAPs). DADAPs belong to schedule 2B6 category of chemical weapons convention (CWC), as they are important markers of the chemical warfare agent Tabun and its analogues. The study was undertaken to develop a spectral database of DADAPs for verification of CWC. The reported synthetic strategy can be adopted to prepare several analogues of DADAPs simultaneously and rapidly during official proficiency tests, for the unambiguous identification of analytes within a short period. Based on the EIMS data of more than 60 compounds, fragmentation routes are proposed which explain the formation of most of the characteristic fragment ions. Subtle differences in EIMS of isomeric DADAPs are discussed to facilitate their identification.