Berovin is a Ca2+- binding photoprotein from Beroe abyssicola that belongs to the CTENOPHORES group. A comparison of the two most famous groups of calcium-regulated photoproteins, Coelentrates and CTENOPHORES, showed high degree of structural similarity regardless of their low sequence identity. Up to now, the crystal structures of several photoproteins such as aequorin, obelin have been solved. Based on these crystal structures, a mechanism have been proposed to explain how Ca2+ binding might trigger the bioluminescence reaction in Coelentrates group. The side chains of His175 and Tyr190 along with the Trp179 in obelin are in close vicinity to the peroxy group of 2-hydroperoxy coelenterazine implying strong hydrogen bonds between them. It was suggested that the His-Trp-Tyr triad participates in stabilization of the 2-hydroperoxy derivative of coelenterazine and might be involved in some steps of the bioluminescence reaction. Despite the precise investigation of Ctenophore binding site, sequence alignment between Coelenterates and CTENOPHORES group and mutagenesis studies on berovin and mnemiopsin, we could not obtain its catalytic triad. This result refers to this point that another light emission mechanism can be existed in CTENOPHORES group. In this study, the localization of coelentrazine in photoprotein of berovin was investigate by docking study. We optimized the full structure of berovin resulting from docking simulation by molecular dynamics simulation. At the optimized conformation, the interactions between amino acids of cavity and the ligand were examined. The results showed that the coelentrazine was located in protein structure with different orientation compared with other Coelentrates photoproteins.

The biochemical composition of the Caspian Sea ctenophore, Mnemiopsis leidyi. was analysed in terms of total fractions of protein, lipid, ninhydrin-positive substances (NPS), polysaccharides (PS) and low molecular- weight carbohydrates (LMC).The sum of organic substance per garm dry weight was 84.18 mg/g. Protein was the major fraction followed by lipid and NPS. The NPS/ protein and LMC/PS ratios were 0.45 and 0:50 mg/g DM, respectively. Starvation of Mnemiopsis leidyi for one week resulted in reduction of all biochemical fractions, and for 3 weeks, high loss of body weight occurred. The sum of organic substances per gram dry weight after one week starvation was 56.7 mg which was 30% less than the non-starved condition. In unfavorable conditions all biochemical fraction changed simultaneously.

The aim of study was Mnemiopsis leidyi’s feeding on zooplankton in the southern Caspian Sea. For this purpose, collecting of CTENOPHORES from surface waters of Khazarabad area were done with a plankton net (500 microns) in 2009 Experiments had done under<18, 18-22 and 22-25oC for 70 days trial in 14 aquaria based on diversity of zooplankton (4 zooplankton groups) with salinity condition of Caspian Sea.4 species of Caspian Sea zooplankton included: Copepod (Acartia tonsa), Rotifer (Branchionus sp.), Cladocera (Podon polyphemoides) and invertebrate benthic larvae (Hypania sp. and Nereis sp.) were collected. Feeding carried out by each 8 hours interval with 7000-9000 individuals. Zooplankton diets of the comb jelly were analyzed on quantity and quality of each feeding rate in all levels of treatments. Laboratory experiments of M. leidyi feeding showed that among different diet exposed to these animals, maximum tendency and digestion were occurred in 22-25oC from Balanide (Balanus sp., 98.1%), Rotifer (95%) and Copepods (90%), respectively. Balanus supposed to be the favorite food item with 98% digestion and Rotifers were the second group after Balanide in M. leidyi diet. Copepods included juvenile, adults and nauplii consisted 34-38% of food item in M. leidyi diet in which benthic larvae was only 27%. Electivity of M. leidyi to Balanide and Copepods adults and Nauplii (A. tonsa) being considered positively while to Nereis sp. was negative.