Seasonal variation of polycyclic aromatic hydrocarbons in the surface sediments of the southern Caspian Sea.

The concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) were determined in sediments from the southern Caspian Sea in fall 2015 and winter 2016. The sum of 16 PAH (ΣPAH) concentrations varied from 17.3±3.05 to 926.7±157.37ngg-1 dry weight and 14.3±0.58 to 85.8±4.41ngg-1 dry weight in fall and winter, respectively. There was no significant correlation between PAH and total organic carbon contents (p>0.05). PAH source identification showed that the PAHs in the sediments originated from petroleum and petroleum combustion. When classified according to the pollution levels, sediments from the southern Caspian Sea could be considered to be low to moderately polluted with PAHs.

Denaturation and intermediates study of two sturgeon hemoglobins by n-dodecyl trimethylammonium bromide.

Varieties of hemoglobin (Hb) forms exist in fish, which are usually well adapted to the different ecological conditions or various habitats. In the current study, Hbs from two Sturgeon species of the Southern Caspian Sea Basin were purified and studied upon interaction with n-dodecyl trimethylammonium bromide (DTAB; as a cationic surfactant) by various methods including UV-visible absorption, dynamic light scattering (DLS), and ANS fluorescence spectrophotometry. The chemometric analysis of Hbs was investigated upon interaction with DTAB under titration, using UV-visible absorption spectra. The chemometric resolution techniques were used to determine the number of the components and mole fraction of the oxidized Hbs. These results provided the evidence for the existence of three different molecular components including native (N), intermediate (I) and denatured (D) in sturgeon Hbs. According to the distribution of intermediates, which were broadened in a range of DTAB concentration, the aggregation states, DLS experiments, and thermal stability (T(m) obtained by differential scanning calorimetry (DSC)), the Acipenser stellatus Hb was more stable compared to Acipenser persicus Hb. These results demonstrate a significant relationship between the stability of fish Hbs and the habitat depth requirements.

Biochemical characterization of hemoglobins from Caspian Sea sturgeons (Acipenser persicus and Acipenser stellatus).

Hemoglobin (Hb) variability is a commonly used index of phylogenetic differentiation and molecular adaptation in fish enabling them to adapt to different ecological conditions. In this study, the characteristics of Hbs from two Sturgeon species of the Southern Caspian Sea Basin were investigated. After extraction and separation of hemoglobin from whole blood, the polyacrylamide gel electrophoresis (SDS-PAGE), cellulose acetate electrophoresis, and isoelectric focusing (IEF) were used to confirm Hb variabilities in these fishes. We showed that although both species have variable Hbs with different isoelectric points, their dominant Hbs can be identified. Ion exchange on CM-cellulose chromatography was used for purification of the dominant Hbs from these fishes. The accuracy of the methods was confirmed by IEF and SDS-PAGE. Spectral studies using fluorescence spectrophotometery indicated that although the Hbs from these fishes had similar properties they exhibited clear differences with human Hb. A comparative study of Hbs alpha-helix secondary substructures was performed by circular dichroism spectropolarimetry (CD) analysis. UV-vis spectrophotometery was also utilized to measure oxygen affinity of Hbs by sodium dithionite. Oxygen affinities of these Hbs were compared using Hb-oxygen dissociation curves. Together, these results demonstrate a significant relationship between oxygen affinity of fish hemoglobins and environmental partial pressure of oxygen.