The interaction between hexavalent chromium Cr(VI), as K(2)CrO(4), and standard humic acids (HAs) in bulk solution was studied using three complementary analytical methods: UV-Visible spectroscopy, X-ray absorption spectroscopy and differential pulse stripping voltammetry. The observed UV-Vis and X-ray absorption spectra showed that, under our experimental conditions, HAs did not induce reducti...

Syntheses of N,N'-phenyltetrazole podands link with aliphatic chains containing oxygen, nitrogen and sulphur atoms, are described. The complexing properties of these compounds towards metal cations (Fe2+, Cu2+, Zn2+, Co2+, Ni2+) were investigated by absorption and infrared spectroscopy. The UV-Vis titrations were performed to estimate the stability constant values of the respective complexes wi...

The UV absorption and electronic circular dichroism (ECD) spectra of (R)- and (S)-nicotine and (S)-nornicotine in aqueous solution were measured to a significantly lower wavelength range than previously reported, allowing the identification of four previously unobserved electronic transitions. The ECD spectra of the two enantiomers of nicotine were equal in magnitude and opposite in sign, while...

The effect of various clay minerals and humic acid on the survival of Klebsiella aerogenes exposed to ultraviolet (UV) irradiation was investigated. A protective effect was observed and found to depend on the specific light absorption and light scattering properties of the clay minerals and the humic acid used. The higher the specific absorption, the better was the survival of K. aerogenes afte...

Typically, the first thing one wants to know about a DNA preparation is its concentration and purity. Both can be determined by measuring the absorption of ultraviolet light. DNA absorbs UV more or less strongly depending upon the wavelength. We will be using a NanoDrop spectrophotometer, which takes measurements at wavelengths of 260 and 280 nm, and in addition determines an absorption spectru...

Abstract: The stability of aqueous and non-aqueous papaverine hydrochloride solutions exposed to the UV radiation is poor. In order to enhance its photo-stability suitable light absorbers may be used. There werefour photo-protectors considered in this work: 4-aminobenzoic acid, sodium benzoate, methyl 4-hydroxybenzoate and propyl 4-hydroxybenzoate, whose UV absorption spectra characteristics ma...

Slow kinetics of homopyrimidine PNA binding to single stranded DNA and RNA targets is manifested in significant hysteresis in thermal UV absorption experiments. We have compared temperatures of dissociation (Tdis) and reassociation (Tass) for triplexes formed by DNA and single or bis PNAs with K50 derived from gel mobility experiments. Results indicated there was no correlation between Tdis and...

X-ray crystallography at third-generation synchrotron sources permits tremendous insight into the three-dimensional structure of macromolecules. Additional information is, however, often required to aid the transition from structure to function. In situ spectroscopic methods such as UV-Vis absorption and (resonance) Raman can provide this, and can also provide a means of detecting X-ray-induced...

The high-resolution X-ray spectrum of NGC 3783 shows several dozen absorption lines and a few emission lines from the H-like and He-like ions of O, Ne, Mg, Si, and S as well as from Fe XVII–Fe XXIII L-shell transitions. We have reanalyzed the Chandra HETGS spectrum using better flux and wavelength calibrations along with more robust methods. Combining several lines from each element, we clearly...

We present observations of the UV absorption lines in the luminous Seyfert 1 galaxy Mrk 509, obtained with the medium resolution (λ/∆λ ≈ 40,000) echelle gratings of the Space Telescope Imaging Spectrograph on the Hubble Space Telescope. The spectra reveal the presence of eight kinematic components of −1 with respect to an emission-line redshift of z = 0.03440, seven of which were detected in an...