Hydrogen bonding of aromatic amines in hydroxylic solvents 2. Absorption and emission spectroscopy of substituted 7-aminocoumarins and 7-aminocarbostyrils

The absorption and fluorescence spectra of 7-aminocoumarins and 7-aminocarbostyrils with different degrees of alkylation were studied in 2-propanol (IP), polyfluorinated alcohols and water. The spectral properties of substituted 7-aminocoumarins and 7-aminocarbostyrils in hexafluoro-2-propanol (HFP) are very different from those in 2-propanol due to the strong hydrogen-bonding (HB) interaction between the solute and the solvent (HFP). The spectral behaviour can be explained in terms of the strength of the HB interaction which depends on the degree of alkylation of the amino group and the electron affinity of the electron-accepting moiety. The absorption spectra indicate that a structural change at the amino nitrogen is induced on formation of strong hydrogen bonds.     

Microscopic theory of memory functions

We define a sequence of microscopic dynamical variables by decomposing a Hilbert space into orthogonal subspaces, and construct for them a new hierarchy of equations which is particularly useful for highly correlated systems. A formal solution is shown to give a microscopic expression of Mori's generalized Langevin equation. With a classical liquid as an example, we demonstrate that the theory facilitates a first-principles calculation of memory functions.     

Binary collision expansion and partial green's functions of Kadanoff-Baym

A new formula for the binary collision expansion of the unitary operator U (t₂, t₁) is proposed. The formula is applied to the expansion of the partial Green's functions of Kadanoff-Baym in powers of the correct binary scattering amplitude. It is shown that certain linked diagrams of left-multidentate structure should be taken into account. The duration of the binary collision is seen to play an important role in the rigorous formulation. Upon neglecting this duration, a useful approximation is found for the analysis of correlations on a macroscopic time scale.     

Synthesis and conversion of 2‐(pyrazol‐1‐yl)quinoxaline 4‐oxides

The reaction of 6‐chloro‐2‐hydrazinoquinoxaline 4‐oxide 1b with acetylacetone or benzoylacetone gave 6‐chloro‐2‐(3,5‐dimethylpyrazol‐i‐yl)quinoxaline 4‐oxide 5a or 6‐chloro‐2‐(3‐methyl‐5‐phenylpyrazol‐1‐yl)quinoxaline 4‐oxide 5b , respXectively. Compound 5a or 5b was converted into the pyrrolo[1,5‐a]quinoxaline 6a or 6b , triazolo[4,3‐a]quinoxaline 9a or 9b , and tetrazolo[1,5‐a]quinoxaline 10.     

Peak spreading in linear gradient elution chromatography with a thin monolithic disk

The peak spreading of DNAs of various sizes [12-mer, 20-mer, 50-mer and 95-mer poly(T)] in linear gradient elution (LGE) chromatography with a thin monolithic disk was investigated by using our method developed for determining HETP in LGE. Electrostatic interaction-based chromatography mode (ion-exchange chromatography, IEC) was used. Polymer-based monolithic disks of two different sizes (12 mm diameter, 3mm thickness and 0.34 mL; 5.2 mm diameter, 4.95 mm thickness and 0.105 mL) having anion-exchange groups were employed. For comparison, a 15-μm porous bead IEC column (Resource Q, 6.4mm diameter, 30 mm height and 0.97 mL) was also used. The peak width did not change with the flow velocity for the monolithic disks where as it became wider with increasing velocity. For the monolithic disks the peak width normalized with the column bed volume was well-correlated with the distribution coefficient at the peak position K(R). HETP values were constant (ca. 0.003-0.005 cm) when K(R)>5. Much higher HETP values which are flow-rate dependent were obtained for the porous bead chromatography. It is possible to obtain 50-100 plates for the 3mm monolithic disk. This results in very sharp elution peaks (standard deviation/bed volume=0.15) even for stepwise elution chromatography, where the peak width is similar to that for LGE of a very steep gradient slope.     

Syntheses, structures, and antimicrobial activities of remarkably light-stable and water-soluble silver complexes with amino acid derivatives, silver(I) N-acetylmethioninates

Reaction of L- and DL-N-acetylmethionine (Hacmet) and Ag(2)O in water at ambient temperature afforded the remarkably light-stable silver complexes {[Ag(L-acmet)]}(n) (1) and {[Ag(2)(D-acmet)(L-acmet)]}(n) (2), respectively. The color of the solids and aqueous solutions of 1 and 2 did not change for more than 1 month under air without any shields. The light stability of these two silver(I) complexes is much higher than that of silver(I) methioninate {[Ag(2)(D-met)(L-met)]}(n) (3) (Hmet = methionine), silver(I) S-methyl-L-cysteinate {[Ag(L-mecys)]}(n) (4), and silver(I) L-cysteinate {[Ag(L-Hcys)]}(n) (5). X-ray crystallography of 1 obtained by vapor diffusion revealed that ladder-like coordination polymers with two O- and two S-donor atoms were formed. The acetyl group of acmet(-) prevents chelate formation of the ligand to the metal center, which is frequently observed in amino acid metal complexes, but allows for formation of hydrogen bonds between the ligands in the crystals of 1. These two silver(I) N-acetylmethioninates showed a wide spectrum of effective antimicrobial activities against gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and yeasts (Candida albicans and Saccharomyces cerevisiae), the effectiveness of which was comparable to that of water-soluble Ag-O bonding complexes.     

Re-Evaluations of Zr-DFO Complex Coordination Chemistry for the Estimation of Radiochemical Yields and Chelator-to-Antibody Ratios of 89Zr Immune-PET Tracers

(1) Background: Deferoxamine B (DFO) is the most widely used chelator for labeling of zirconium-89 (⁸⁹Zr) to monoclonal antibody (mAb). Despite the remarkable developments of the clinical ⁸⁹Zr-immuno-PET, chemical species and stability constants of the Zr-DFO complexes remain controversial. The aim of this study was to re-evaluate their stability constants by identifying species of Zr-DFO complexes and demonstrate that the stability constants can estimate radiochemical yield (RCY) and chelator-to-antibody ratio (CAR). (2) Methods: Zr-DFO species were determined by UV and ESI-MS spectroscopy. Stability constants and speciation of the Zr-DFO complex were redetermined by potentiometric titration. Complexation inhibition of Zr-DFO by residual impurities was investigated by competition titration. (3) Results: Unknown species, ZrH_qDFO₂, were successfully detected by nano-ESI-Q-MS analysis. We revealed that a dominant specie under radiolabeling condition (pH 7) was ZrHDFO, and its stability constant (logβ₁₁₁) was 49.1 ± 0.3. Competition titration revealed that residual oxalate inhibits Zr-DFO complex formation. RCYs in different oxalate concentration (0.1 and 0.04 mol/L) were estimated to be 86% and >99%, which was in good agreement with reported results (87%, 97%). (4) Conclusion: This study succeeded in obtaining accurate stability constants of Zr-DFO complexes and estimating RCY and CAR from accurate stability constants established in this study.