scholarly journals The chemistry of vitamin B12. The coordination of biologically important molecules

1970 ◽  
Vol 120 (2) ◽  
pp. 263-269 ◽  
Author(s):  
H. A. O. Hill ◽  
J. M. Pratt ◽  
R. G. Thorp ◽  
B. Ward ◽  
R. J. P. Williams
Keyword(s):  
Charge Transfer ◽  
Absorption Band ◽  
Hydrogen Bonds ◽  
Vitamin B12 ◽  
Extinction Coefficient ◽  
Equilibrium Constants ◽  
Thiol Group ◽  
Intense Absorption Band ◽  
Intense Absorption ◽  
A Charge

The following equilibrium constants (given as logK in units of m−1) were determined for the substitution of co-ordinated H2O in aquocobalamin by glycine (bound through N) 5.8, cysteine (bound through S) 6.0 or 8.3, depending on the value chosen for the pK of the thiol group, and phenolate 2.9. The spectrum of the phenolate cobalamin shows an additional intense absorption band at 468nm with a molar extinction coefficient of 1.1×104, which is assigned to a charge transfer from the phenolate to the cobalt ion. Equilibrium constants have also been determined for the equilibria between adenylcobamide cyanide and CN−, HO− and H+, which show that the adenine is more easily displaced by CN− and HO− than is 5,6-dimethylbenziminazole in vitamin B12, but can be protonated by acid while still remaining co-ordinated to the cobalt. It is shown that in the binding of corrinoids to proteins and polypeptides the formation of hydrogen bonds is far more important than co-ordination by the metal.

scholarly journals Fused bis-azacalixphyrin that reaches NIR-II absorptions

2020 ◽  
Vol 56 (6) ◽  
pp. 896-899 ◽  
Author(s):  
Lucien Lavaud ◽  
Cloé Azarias ◽  
Gabriel Canard ◽  
Simon Pascal ◽  
Joachim Galiana ◽  
...  
Keyword(s):  
Absorption Band ◽  
New Class ◽  
Intense Absorption Band ◽  
Intense Absorption

The fusion of two azacalixphyrins produces a new class of NIR-II dyes showing an intense absorption band in the 1000–1200 nm NIR range.

BF2 complexes of 1,3-diketones on the surface of phosphorus dendrimers: synthesis and study of the photoluminescence properties

2017 ◽  
Vol 95 (9) ◽  
pp. 948-953 ◽  
Author(s):  
Cédric Rouxel ◽  
Olivier Mongin ◽  
Aurélien Hameau ◽  
Armelle Ouali ◽  
Mireille Blanchard-Desce ◽  
...  
Keyword(s):  
Absorption Band ◽  
Hypsochromic Shift ◽  
Photoluminescence Properties ◽  
Intense Absorption Band ◽  
Intense Absorption

Difluoroboron complexes of monomeric and dimeric diketones and of generations 0–4 of phosphorus dendrimers ended by diketone ligands are synthesized and characterized. Their photoluminescence properties are measured. All compounds exhibit an intense absorption band in the near UV region. Both model dimers and dendrimers show a marked hypsochromic shift of this absorption band compared with the monomeric difluoroboron complex. The fluorescence of the dioxaborine complex subunit in the multichromophoric dendritic architectures is quenched compared with the emission of the isolated monomeric fluorophore, presumably due to interactions between the terminal groups of dendrimers.

Charge transfer and electron transfer processes in biologically significant systems. 1. Charge transfer complex formation between 1,3,5-trinitrobenzene and N,N-dimethyl-3,4-di-O-methyldopamine, a dopamine analogue

1992 ◽  
Vol 70 (1) ◽  
pp. 151-157 ◽  
Author(s):  
Julian M. Dust
Keyword(s):  
Charge Transfer ◽  
Charge Transfer Complex ◽  
Equilibrium Constants ◽  
Structural Analogue ◽  
Molecular Receptors ◽  
H Nmr ◽  
Transfer Processes ◽  
A Charge ◽  
Electron Transfer Processes ◽  
Probable Type

The interactions of N,N-dimethyl-3,4-di-O-methyldopamine, 1, a structural analogue of the important neurochemical, dopamine, with 1,3,5-trinitrobenzene (TNB) were studied primarily by 1H nuclear magnetic resonance (nmr). The dopamine analogue, a donor, forms a charge transfer complex with TNB, a model acceptor, in CDCl3 and CD3CN. Equilibrium constants were determined from the 1H nmr charge transfer induced chemical shift changes. The results are discussed in terms of the probable type of donation from the amine, 1, to TNB (n → π* versus π → π*), comparison with dopamine, and with regard to possible charge transfer interactions in molecular receptors. Keywords: N,N-dimethyl-3,4-di-O-methyldopamine, charge transfer complex, equilibrium constant.

Hydrated Electrons Formed in the Flash Photolysis of Ag° and Tl°

1973 ◽  
Vol 51 (15) ◽  
pp. 2497-2501 ◽  
Author(s):  
Norman Basco ◽  
Sunil K. Vidyarthi ◽  
David C. Walker
Keyword(s):  
Charge Transfer ◽  
Absorption Band ◽  
Work Function ◽  
Wavelength Range ◽  
Flash Photolysis ◽  
Transient Species ◽  
Hydrated Electrons ◽  
A Charge ◽  
Silver Metal ◽  
Double Flash

The transient species Ag0, formed in the reduction of Ag+ by hydrated electrons, may be photodissociated to eaq− again by light in the absorption band of Ag0 centered at ~315 nm.[Formula: see text]It suggests that this band is a charge-transfer-to-solvent band. The photon energy threshold for photoionization of Ag0 (3.0 eV) is substantially smaller than the vacuum photoelectric work function of silver metal (4.5 eV). Analogous results were obtained in solutions of Tl+ indicating that Tl0 may also yield eaq− on photolysis at ~300 nm. The experiments utilized a double flash photolysis technique, in which hydrated electrons were produced by u.v. photolysis of SO42− in the first flash, reacted with Ag+ or Tl+ to give the short-lived intermediates Ag0 (lifetime ~60 μs) and T10 (lifetime < 20 μs) which were photolyzed by a second flash containing light in a restricted wavelength range.

scholarly journals VII. On the relations of turacin and turacoporphyrin to the colouring matter of the blood

1896 ◽  
Vol 59 (353-358) ◽  
pp. 339-342 ◽  
Keyword(s):  
Absorption Band ◽  
Royal Society ◽  
Intense Absorption Band ◽  
Intense Absorption ◽  
Derivatives Of

In a recent paper read before the Royal Society, I have shown that the intense absorption band in the extreme violet, which is observed, by means of photography, in the spectrum of highly diluted solutions of hemoglobin and its compounds, is (with slight changes in its position) exhibited by certain of the derivatives of the blood colouring matter, e. g ., by hemochromogen and the compounds of hematin, and by that remarkably interesting coloured but iron-free derivative of the latter body, hematoporphyrin.

scholarly journals FAR-INFRARED STUDIES OF THE STATE OF IONICAGGREGATION IN MIXTURES OF POLYETHERURETHANE AND K IONOMER STYRENE COPOLYMER WITH ACRYLIC ACID

2020 ◽  
pp. 150-160
Author(s):  
Валерий Александрович Рыжов
Keyword(s):  
Spectral Analysis ◽  
Absorption Band ◽  
Ion Pairs ◽  
Far Infrared ◽  
Carboxyl Groups ◽  
Styrene Copolymer ◽  
Ionic Groups ◽  
Intense Absorption Band ◽  
Infrared Studies ◽  
Intense Absorption

Методом спектрального анализа в дальнем (70 - 420 см) ИК-диапазоне исследовано влияние введения ионных групп на формирование сетки физических связей в композитах на основе полиэфир уретана и сополимера стирола. Анализ спектров ПУИ / Ст-со-АК (К+) композитов показал, что при увеличении содержания Ст-со-АК (К+) в системе образуется новая сетка межмолекулярных (ион-молекулярных) связей. Появление интенсивной полосы поглощения при ~ 180 см, обусловленной колебаниями катионов К+ в электростатической области анионов (СОО-) карбоксильных групп, её значительная полуширина и наличие максимумов при 145, 155, 177, 185, и 200 см свидетельствуют об образовании различных по организации форм катион-анионных ассоциатов в системе: от простых ионных пар до сложных мультиплетов и кластеров. He effect of the introduction of ionic groups on the formation of a network of physical bonds in composites based on polyether urethane (PEUI) and styrene copolymer (S-co-AA (K+)) was studied by the method of spectral analysis in the far (70-420 cm) IR range. An analysis of the spectra of PEUI / S-co-AA (K+) composites showed that with an increase in the content of S-co-AA (K+), a new network of intermolecular (ion-molecular) bonds forms in the system. The appearance of an intense absorption band at ~ 180 cm, due to vibrations of K+ cations in the electrostatic region of anions (COO-) carboxyl groups, its significant half width and the presence of maxima at 145, 155, 177, 185, and 200 cm indicate the formation of various on the organization of forms of cation-anion associates in the system: from simple ion pairs to complex multiplets and clusters.

Ultraviolet spectrum of domoic acid

1989 ◽  
Vol 67 (9) ◽  
pp. 1421-1425 ◽  
Author(s):  
Michael Falk ◽  
John A. Walter ◽  
Paul W. Wiseman
Keyword(s):  
Absorption Band ◽  
Domoic Acid ◽  
Ultraviolet Spectrum ◽  
Acid Solutions ◽  
Intense Absorption Band ◽  
Intense Absorption

The ultraviolet spectrum of aqueous domoic acid solutions has an intense absorption band, whose λmax shifts from 240.0 ± 0.3 nm at pH 1.3 to 244.7 ± 0.3 nm at pH 12.3. At the same time, its εmax increases from 24250 to 26700 L mol−1 cm−1. At pH 7 λmax is 242.8 ± 0.3 nm and εmax is 26035 ± 200 L mol−1 cm−1 Analysis of the variation of λmax and εmax with pH allowed us to estimate the values of these quantities for each of the five stages of protonation of domoic acid and to verify the pK values reported by Takemoto and Daigo. Keywords: ultraviolet spectrum, pK values, protonation, domoic acid.

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