摘要:

It was found that the photoexitation of a frozen solution of vitamin K1(phyllonaphtoquinone) gave rise to the formation of biradicals with a very bright spectra (ΔH ∼ 200 G), typical for randomly oriented radical pairs with a summary spin of S = 1. This spectra was not overlaped by those of the other radical products generated following the photolysis of vitamin K1in different matrices. This method is proposed for the determination of vitamin K, in biological samples and was successful in following the accumulation of vitamin K1in mouse liver following subcutaneous injection.

ISSN:0038-7010    

DOI:10.1080/00387019808003280

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The1H- and13C-NMR spectra of 6,7-dihalo-1,4-dihydro-4-oxo-1-(2,3,5-tri-0-benzoyl-pβ-D-ribofuranosyl)quinoline-3-carboxylic acids (3), (4), the ester (3a), 6-chloro-1-(2-deoxy-3,5-di-O-tolouyl-α- and β-D-erythropentofuranosyl)-7-fluoro-1,4-dihydro-4-oxo-quinoline-3-carboxylic acid (5), and its free a-nucleoside (5a) have been investigated. Resonance signals were assigned by homo- and heteronuclear two dimensional NMR methods (DQF-COSY, HMQC, and HMBC) for (3), (4), (5), and (5a). Ribosylation sites and anomeric configurations were identified from ROESY spectra.

ISSN:0038-7010    

DOI:10.1080/00387019808003281

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The study of interactions of xenobiotics with macromolecular receptors is very important for understanding the chemical behaviour of xenobiotic compounds in the biological organisms.

ISSN:0038-7010    

DOI:10.1080/00387019808003282

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The multicomponent analysis with Partial Least-Squares Method (PLS) using FTIR spectroscopy has been studied in this paper. In order to ensure the reliability of the prediction results, a criterionSOandSAis created in the PLS algorithm to conclude the similarity between the prediction samples and the calibration ones. An example for the simultaneous determination of Ethylbenzene, Styrene, o-Xylene, m-Xylene and p-Xylene is supplied. The experimental designs of the both the calibration and prediction samples are discussed as well as the significant factor number. With proper multivariate calibration conditions, the average mean relative error (MRE %) is 0.25 % and the average relative standard deviations (RSD%) for Ethylbenzene, Styrene, o-Xylene, m-Xylene and p-Xylene are 0.19, 0.15, 0.06, 0.44 and 0.13 %, respectively.

ISSN:0038-7010    

DOI:10.1080/00387019808003283

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Tetra(3-pyridyl)porphyrazine is soluble in trifluoroethanol yielding intense blue solutions. The electronic spectra exhibit the characteristic Soret and Q bands around 330 and 610 nm, respectively; however, the absorption profile is strongly dependent on the concentration, reflecting the occurrence of an association process. The system has been elucidated by solving the equilibrium and the absorbance-concentration equations for all the wavelengths in the spectral range, according to a variational procedure. In this way the consistent spectra of the individual species have been generated. The study has also been extended to the luminescence properties of the porphyrazine molecule, and discussed in terms of the ground state association and the exciplex formation involving the monomeric species.

ISSN:0038-7010    

DOI:10.1080/00387019808003284

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The binding of β-methyl-pyridine (β-MePy) to horse heart ferricytochorme c (cyt c) was studied by two-Dimensional exchange spectroscopy. Kinetic and equilibrium data for β-MePy binding to cyt c have been determined. Some hyperfine shifted resonances of β-MePy-cyt c have been assigned. Differences between β-MePy-cyt c and pyridine bound cyt c (py-cyt c) have been disscussed.

ISSN:0038-7010    

DOI:10.1080/00387019808003285

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

1H-NMR spectra of DBH (1), DBO (2) and of the synthetic precursor to1, 1,4-phenyl-2,4,6-triazatricyclo[5.2.1.02,6]heplanc-3,5-dione (3), were recorded in acetone-d6and C6D6at 500 MHz. Assignment was aided by complete resolution of signals of1and3in C6D6by aromatic solvent-induced shifts (ASIS). The effect of the change from phenyllriazolinedione to a diazene functional group on the chemical shifts of theexo,endoandsyn,antiprotons was investigated. The chemical shifts of theexo,endoprotons of1are exceptionally sensitive to the functional group at the hetero substituted bridge in the DBH skeleton. However, the relative chemical shift of thesyn,antiproton pair is independent of the nature of the functional group. The role of stereochemical effects on these chemical shifts is discussed.

ISSN:0038-7010    

DOI:10.1080/00387019808003286

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The infrared spectrum of 3-bromo-1,3-dinitroazetidine was interpreted with the aid of normal coordinate calculations. A seventy-two parameter modified valence field was used in those calculations, and the observed wave numbers were fit with an average error of 2.5 cm−1. An assignment of the bands in terms of symmetry coordinates is given. Many of the force constants were transferred to 1-acetyl-3,3-dinitroazetidine to aid in normal coordinate calculations for that compound.

ISSN:0038-7010    

DOI:10.1080/00387019808003287

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The effect of the substituents, solvent polarities and hydrogen ion concentration on the electronic structure and UV/VIS absorption spectra of some Schiff bases, derivatives of N-(R-benzylidene)benzidine (R = o-NO2and o-OH, p-OH) and N-(R-furfurylidene)benzidine (R = H and 5 - NO2), have been studied. The spectral shifts obtained in various organic solvents were discussed on the basis of the specific solute - solvent interactions through the formation of hydrogen bonds between hydrogen-bond donor (HBD) solvents and the benzidine nitrogen atom of the Schiff bases. Some interpretations of the electronic aspects of this type of hydrogen bonding were discussed as well as the stabilization effects due to the solvation. Finally, the pK values of the compounds were determined.

ISSN:0038-7010    

DOI:10.1080/00387019808003288

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0038-7010    

DOI:10.1080/00387019808003289

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor