A novel type of metal‐containing polyimides based on tricarbonylrhenium(I) diimine complexes

A series of rhenium containing polyimides was prepared by the polymerization between a tricarbonylrhenium diimine complex with various aromatic dianhydrides. Electronic absorption spectra of the polymers showed a very strong intramolecular charge transfer transition which obscures the transfer transition band due to the rhenium complex in the visible region. A large photocurrent response was also observed when the polyimide was irradiated at 514 nm.     

Determination of internucleotide (h)J(HN) couplings by the modified 2D J(NN)-correlated [(15)N, (1)H] TROSY

Recent developments in the direct observation of J couplings across hydrogen bonds in proteins and nucleic acids provide additional information for structure and function studies of these molecules by NMR spectroscopy. A J(NN)-correlated [(15)N, (1)H] TROSY experiment proposed by Pervushin et al. (Proc. Natl. Acad. Sci. USA 95, 14147-14151, 1998) can be applied to measure (h)J(HN) in smaller nucleic acids in an E.COSY manner. However, it cannot be effectively applied to large nucleic acids, such as tRNA(Trp), since one of the peaks corresponding to a fast relaxing component will be too weak to be observed in the spectra of large molecules. In this Communication, we proposed a modified J(NN)-correlated [(15)N, (1)H] TROSY experiment which enables direct measurement of (h)J(HN) in large nucleic acids.     

Studies in the furan series. XXXIX. Reaction of furan and 2-methylfuran with acrylonitrile

Furan undergoes a diene-synthesis type of reaction with acrylonitrile to give stereoisomeric 3, 6-endoxotetrahydrobenzonitriles whose configurations are established by PMR spectra. 2-Methylfuran undergoes a similar reaction with acrylonitrile. Some aspects of the relationship between the diene substitution reaction and substitutive addition in the furan series are considered.Communication XXXVIII, see [1].     

Time-resolved resonance Raman observation of the 2-fluorenylnitrenium ion reaction with guanosine to form a C8 intermediate

Time-resolved resonance Raman spectroscopy was used to directly observe the reaction of the 2-fluorenylnitrenium ion with guanosine to produce a C8 intermediate species. Comparison of the Raman spectra with results of density functional theory calculations indicates the C8 intermediate forms two C=N conjugated bonds in ring 1 of the guanosine moiety.     

Separation and determination of metal cations in milk and dairy products by CE

To prevent casein adsorption and improve between-run repeatability, a CE procedure is developed for cation analysis in milk using a modified imidazole/alpha-hydroxyisobutyric acid (HIBA) BGE system to operate at pH 6 to match the pH of milk and elevate imidazole concentration to enhance its buffer action. The procedure is shown to produce a fast, economic and efficient method for cation separation in milk with only simple dilution. Upon direct hydrodynamic injection of diluted milk sample at 8 cm for 30 s in an uncoated column with a BGE consisting of 10 mM imidazole, 10 mM HIBA and 10% methanol at pH 6.0 under +18 kV, baseline separation was achieved for K(+), Na(+), Ca(2+), Mg(2+), Mn(2+), Cd(2+), Co(2+), Ni(2+)and Zn(2+). Agreeable results at 95% confidence level were obtained using CE and inductively coupled plasma-atomic emission spectrometry (ICP-AES) for milk samples after protein removal. Baseline-resolved peaks for essential minerals were obtained for fresh and non-refrigerated reconstituted milks. Long-term stability was demonstrated by repeated determinations without rinsing and improvement in repeatability was shown by rinsing with 60 mM SDS in BGE. Information on metal speciation useful for nutritional assessment was obtained from CE to complement the ICP methods.     

HYBRID LINEAR AND QUADRATIC FINITE ELEMENT MODELS FOR 3D HELMHOLTZ PROBLEMS

In this paper, linear and quadratic finite element models are devised for the three- dimensional Helmholtz problem by using a hybrid variational functional. In each element, contin- uous and discontinuous Helmholtz fields are defined with their equality enforced over the element boundary in a weak sense. The continuous field is based on the C° nodal interpolation and the discontinuous field can be condensed before assemblage. Hence, the element can readily be in- corporated seamlessly into the standard finite element program framework. Discontinuous fields constructed by the plane-wave, Bessel and singular spherical-wave solutions are attempted. Nu- merical tests demonstrate that some of the element models are consistently and considerably more accurate than their conventional counterparts.     

Maintaining radiochemical purity of [177Lu]Lu-DOTA-PSMA-617 for PRRT by reducing radiolysis

Journal of Radioanalytical and Nuclear Chemistry - [177Lu]Lu-DOTA-PSMA-617 for PRRT is subject to radiolysis and therefore loses receptor affinity. This will be detrimental for treatment efficacy....     

Oligomers-model building in protonation equilibria of sitagliptin

Mixed protonation constants of sitagliptin phosphate at various ionic strengths I (mol kg^?1) in range 0.01 and 0.50 and at 298.15 K are determined using FBSTAC4 and HYPERQUAD nonlinear regression analyses of the potentiometric titration curve. At a low concentration c _L = 1.1 mmol kg^?1 the monomers L, LH, LH₂, LH₃ and LH₄ dominate, while for a concentration range from c _L = 13.7 to 24.7 mmol kg^?1 dimers L₂H₂, L₂H₃, L₂H₄ and L₂H are mainly present. The regression programme has almost no influence on the precision of the protonation constants. The accuracy of the protonation constants log β _qr depends on the accuracy of the group parameters. As two group parameters c _L,0, c _H,T are ill-conditioned in a model, their determination is therefore uncertain: both can significantly cause a systematic error in the estimated common parameters log₁₀β _qr . Fitness tests using regression diagnostics have proven the reliability of the parameter estimates.      

Reliability of protonation constants of vildagliptin dimers by the regression analysis of pH-titration data

Protonation constants of protonated monomers and dimers of the vildagliptin are determined potentiometrically. For the low concentration c _L = 3.3 mmol dm^?3 the monomers L and LH dominate, while for a higher concentration c _L = 6.3 mmol dm^?3 the dimers L₂H₂, L₂H₃, L₂H₄ and L₂H are mainly present. The algorithm used has little influence on the precision of the formation constants in comparison with the reproducibility of the titration. The mixed protonation constants of vildagliptin dimers L _q H _r at various temperatures are determined using FBSTAC4 and HYPERQUAD regression analysis of the potentiometric titration data. The accuracy of the protonation constants log₁₀ β _qr depends on the accuracy of the group parameters. As two group parameters L ₀, H _T are ill conditioned in a model, their determination is therefore uncertain; both can significantly cause a systematic error in the estimated common parameters log₁₀ β _qr . Using various regression diagnostics the goodness-of-fit proves the reliability of all parameter estimates. A rough estimation of thermodynamic enthalpies ΔH ⁰ (kJ mol^?1) and entropies ΔS ⁰ (J K^?1 mol^?1) is determined from the temperature variation of protonation constants. The enthalpy shows the protonation process is exothermic, and the entropy indicates that it is spontaneous.