On the far ultraviolet absorption spectrum of ethyl fluoride

The absorption spectrum of C₂H₅F has been measured in the region down to 1150 Å with absorption maxima at 1290, 1240 and 1180 Å and has been interpreted with Rydberg transitions from the σ(CC) and pseudo π(CH₃) orbitals to the carbon 3s and 3p orbitals.     

Structure and ultraviolet absorption spectra of indazolones

The UV spectra of indazolone and its derivatives are investigated, and hypotheses regarding their structure advanced. It is shown that the UV spectra of 1- and 2- acylindazolones have different characters, which can be utilized to identify those particular isomers.     

Vacuum ultraviolet absorption spectra of simple amides

Vacuum ultraviolet absorption spectra of six simple amides were measured. It was found that the positions of the firstπ→π ^* transition bands shift appreciably by the substitutions of methyl groups for hydrogen atoms of the NH₂ and\(\begin{gathered} | \hfill \\ H - C = O \hfill \\ \end{gathered} \) groups. A general tendency is that the substitution in the NH₂ group shifts the band toward longer wavelengths, in the\(\begin{gathered} | \hfill \\ H - C = O \hfill \\ \end{gathered} \) group however towards shorter wavelengths. This was explained satisfactorily by considering the nature of the band (intramolecular charge-transfer band) and the hyperconjugation effect of the methyl group.     

A model of the effects of pressure on the near ultraviolet absorption spectrum of crystalline naphthalene

The variation with pressure of the two components of the electronic origin band of the first singlet-singlet transition in crystalline naphthalene is considered. A model is constructed which gives a satisfactory account of this variation. The splitting contains both Coulomb and overlap-dependent terms and the mean shift contains dispersion terms.     

8-Arylpurines and their ultraviolet absorption spectra

Dehydrocyclization of 4-amino-5-arylamidopyrimidines in polyphosphoric acid to 8-arylpurines was further investigated. Various other 8-arylpurines were synthesized by this new procedure in high purity and yield. The ultraviolet absorption spectra of the arylpurines and the corresponding acylamidopyrimidines were measured at pH 1, 7, and 13 at 0.1 molar ionic strength. The spectra of the purines resemble those of the corresponding acylamidopyrimidines and, to a lesser extent, the corresponding 4,5-diaminopyrimidines. The bathochromic shifts caused by different substituting groups in monosubstituted purines, in general, parallel the inductive effect of the substituting groups. The hyperchromicity and the inductive constant of the substituting groups assume a linear relationship, for substitution at either the 2 or 6 position. These changes in the wave length of maximum absorption and in the molar extinction coefficient caused by 2, 6 and 8 substitutions of the purines reported here are in agreement with previous studies by Mason.     

Solvent effects on the ultraviolet absorption spectrum of mercury atom

Absorption spectrum of mercury dissolved in hexane and heptane in the region 280–180 nm was found to consist of three bands. These bands were assigned to the ¹S₀ → ¹P₁ transition (A band, λ = 254 nm), to the ¹S₀ → ³P₂ transition (B band, λ = 226 nm) and to the ¹S₀ → ¹P₁ transition (C band, λ = 190 nm) of a mercury atom placed into a liquid cell. The B and C absorption bands of mercury in liquid solutions were observed for the first time. It was found that the A band and the C band have, respectively, distinct doublet and triplet structure, while the doublet structure of the B band is only slightly seen. The oscillator strengths of all three bands of mercury in solutions were estimated. The structure of the C, A and B bands of mercury in solutions most probably results from the removal of the degeneracy of the excited states ¹P₁, ³P₁ and ³P₂ of a mercury atom, placed into a cell of low symmetry.     

The absorption spectrum of the anthracene molecule in the vacuum ultraviolet

The optical absorption of anthracene vapour for photon energies from 5 to 8.5 eV was found to differ in finer structure from the spectra reported earlier for parts of this range. Above the strong ¹B_2u long axis polarized πlπ^* transition at 5.24 eV three short axis polarized ¹B_1u ππ^* transitions are assigned on the basis of the oriented gas model in comparison to spectra from anthracene single crystals. A tentative new assignment for most of the additionally observed sharp Rydberg bands leading to the first ionization potential at 7.47 eV is given.     

Vacuum ultraviolet absorption spectra of stearic acid multilayers

Vacuum ultraviolet absorption spectra up to 10 eV of stearic acid multilayers prepared at acid, neutral and alkaline pH have been obtained. It is suggested that a hydrogen bonded dimer is formed in the multilayers prepared at acid pH and the σ-σ^* transitions polarized in the direction of the n-alkane chain are at shorter wavelengths than the perpendicularly polarized ones.     

Determination of protein in solutions from absorption in the ultraviolet region

A comparison of spectrophotometric methods of determining protein in solutions from absorption in the UV region has shown the advantage of a procedure based on measuring the optical densities at 235 and 280 nm and the possibility of its use for the analysis of plant proteins.     

Determination of protein in solutions from absorption in the ultraviolet region

A comparison of spectrophotometric methods of determining protein in solutions from absorption in the UV region has shown the advantage of a procedure based on measuring the optical densities at 235 and 280 nm and the possibility of its use for the analysis of plant proteins.Scientific-Research Institute of Biology, Dnepropetrovsk State University. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 693–695, September–October, 1989.     

Preparation and ultraviolet absorption spectra of the isomeric naphthobenzothiophenes and naphthobenzofurans

Naphtho[2,1-b]benzothiophene has been synthesized unequivocally by the ring closure of 2-phenylmercapto-1-tetralone, followed by dehydrogenation of the resulting dihydro derivative. The other isomeric naphthobenzothiophenes have been prepared by modifications of known methods and their ultraviolet absorption spectra have been compared. Condensation of α-naphthol with 2-chlorocyclohexanone leads to 7,8,9,10-tetrahydronaphtho-[1,2--6]benzofuran, which can be readily dehydrogenated with selenium to naphtho[1,2-b]-benzofuran. The ultraviolet spectra of the naphthobenzofurans are reported, and compared to their sulfur analogs.     

Origin of the anomalous two-photon absorption in fluorescent protein DsRed

The red fluorescent protein DsRed displays a two-photon excitation band around 760 nm which is not accompanied by any feature in the corresponding one-photon spectral region (380 nm). By means of time-dependent density functional theory, we are able to explain such an effect, as arising from an electronic excitation of the DsRed chromophore with ability to couple with a charge-transfer state, through an effective two-photon absorption channel.     

Photoelectron and ultraviolet absorption spectra of allenyl vinyl ethers

The electronic structure of allenyl vinyl ethers (I) has been studied with the aid of photoelectron and UV spectroscopy, as well as MNDO and CNDO/S quantumchemical calculations. Divinyl ether has been selected as a model system for these molecules. The photoelectron spectra of I are similar to the spectrum of divinyl ether, with the exception of the band at 10.2–10.6 eV. The long-wavelength band in the UV spectra of I has been assigned to a transition localized in the allene group. The short-wavelength band of I corresponds to the ^* transition observed in divinyl ether.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2011–2014, September, 1989.     

Origin of the unusual kinetics of iron deposition in human H-chain ferritin

From microorganisms to humans, ferritin plays a central role in the biological management of iron. The ferritins function as iron storage and detoxification proteins by oxidatively depositing iron as a hydrous ferric hydroxide mineral core within their shell-like structures. The mechanism by which the mineral core is formed has been the subject of intense investigation for many years. A diiron ferroxidase site located on the H-chain subunit of vertebrate ferritins catalyzes the oxidation of Fe(II) to Fe(III) by molecular oxygen. A previous stopped-flow kinetics study of a transient mu-peroxodiFe(III) intermediate formed at this site revealed very unusual kinetics curves, the shape of which depended markedly on the amount of iron presented to the protein. In the present work, a mathematical model for catalysis is developed that explains the observed kinetics. The model consists of two sequential mechanisms. In the first mechanism, turnover of iron at the ferroxidase site is rapid, resulting in steady-state production of the peroxo intermediate with continual formation of the mineral core until the available Fe(II) in solution is consumed. At this point, the second mechanism comes into play whereby the peroxo intermediate decays and the ferroxidase site is postulated to vacate its complement of iron. The kinetic data reveal for the first time that Fe(II) in excess of that required to saturate the ferroxidase site promotes rapid turnover of Fe(III) at this site and that the ferroxidase site plays a role in catalysis at all levels of iron loading of the protein (48-800 Fe/protein). The data also provide evidence for a second intermediate, a putative hydroperoxodiFe(III) complex, that is a decay product of the peroxo intermediate.     

The determination of nitrite by ultraviolet absorption spectrometry in the gas phase

Aliquots of nitrite-containing solutions are injected into small aliquots of 8 M hydrochloric acid and the evolved gases are swept by a stream of carrier gas through an absorption cell where transient absorbance in the gas phase is measured at 195 nm. The detection limit is 0.2 μg NO₂^- ml^-1 with the calibration curve remaining linear to 65 μg NO₂^- ml^-1 Reproducibility is reflected in 2.4% relative standard deviation from the mean at the 5 μg NO₂^- ml^-1 level. There is no interference from CO₃^2-, NO₃^-, SO₄^2-, Br^-, CN^-, CNO^-, or NH₄⁺, but SCN^-, I^-, S^2- and SO₃^2- interfere.