Proteomic Analysis of Sarcoplasmic Peptides of Two Related Fish Species for Food Authentication

Detection of species-specific sarcoplasmic peptides can be used as proteomic markers for fish food authentication and identification of species of origin in processed products. In the present study, proteomics technology was employed for differential characterization of sarcoplasmic peptides of two closely related fish species, Sperata seenghala and Sperata aor. Species-specific peptides were searched in white muscle extracts of the two species for identification of unique peptides that might aid in differentiation of the species, under two-dimensional gel electrophoresis platform. A total of 19 proteins were identified by combined matrix-assisted laser desorption ionization time-of-flight mass spectrometry and liquid chromatography-tandem mass spectrometry, of which nine and two proteins were found to be unique to S. seenghala and S. aor, respectively. One of the proteins, triosephosphate isomerase (TPI) was found to have three isoforms, out of which two were specific to S. aor, and one was specific to S. seenghala. All the three isoforms of TPI were present in the mixed samples of raw protein extracts of S. seenghala and S. aor, an observation that can be exploited to differentiate between the species and detection of deceptive practices of fraudulent substitution of commercially valuable fish species with inferior ones and differential characterization between closely related fish species.     

Fluorescence spectroscopic studies on binding of a flavonoid antioxidant quercetin to serum albumins

Binding of quercetin to human serum albumin (HSA) was studied and the binding constant measured by following the red-shifted absorption spectrum of quercetin in the presence of HSA and the quenching of the intrinsic protein fluorescence in the presence of different concentrations of quercetin. Fluorescence lifetime measurements of HSA showed decrease in the average lifetimes indicating binding at a location, near the tryptophan moiety, and the possibility of fluorescence energy transfer between excited tryptophan and quercetin. Critical transfer distance (R _o ) was determined, from which the mean distance between tryptophan-214 in HSA and quercetin was calculated. The above studies were also carried out with bovine serum albumin (BSA).     

Trigonal propeller-shaped [Mn(III)3M(II)Na] complexes (M = Mn, Ca): structural and functional models for the dioxygen evolving centre of PSII

Two new polynuclear heterometallic cluster complexes with [Mn(III)(3)M(II)Na] (M = Mn, Ca) core were synthesized using two in situ formed Schiff bases. The compounds were structurally characterized by single crystal X-ray analysis. The compound with [Mn(III)Ca(II)Na] appeared to catalyse water oxidation which was followed by using Clark electrode and online mass spectrometry.     

Schiff base supported mononuclear organotin(IV) complexes: Syntheses,structures and fluorescence cell imaging

Three mononuclear organotin(IV) complexes supported by Schiff bases have been synthesized. The complexes [(C₆H₅)₂Sn(L)] ( 1 ), [(t‐Bu)₂Sn(L)] ( 2 ) and [(t‐Bu)₂Sn(L')] ( 3 ) (L, L' = deprotonated Schiff bases) were obtained in good yield by the reaction of Schiff bases H ₂ L or H ₂ L′ with corresponding diorganotin dichlorides respectively. All newly synthesized complexes were characterized by means of FT‐IR spectroscopy, elemental analysis and multinuclear (¹H, ¹³C and ¹¹⁹Sn) NMR spectroscopy. In addition, single crystal X‐ray diffraction analyses were employed to establish the solid state molecular structures of these complexes. The structures of 1 – 3 reveal that all complexes are mononuclear with a five‐coordinated tin(IV) centre in it. The absorption and emission properties of all complexes have been investigated. Moreover, cytotoxicity and fluorescence cell imaging studies of theses complexes have been performed.     

Existence criteria for reflection configurations in shock–vortex interactions

The length scale criteria is widely accepted as an explanation for transition and hence existence of different shock wave reflection configurations in pseudo-steady flows. However, there has not been any attempt to validate this criteria using information obtained from a time-dependent numerical simulation. A high resolution time-dependent numerical simulation in pseudo-steady flow is carried out in the present work. Time-dependent numerical data is used to calculate flow features in a laboratory frame of reference to verify validity of the length scale criteria for existence of different shock wave reflection configurations in pseudo-steady flow. This analysis is then extended to the study of unsteady shock wave reflection configurations in shock–vortex interactions. It is shown that the existence of regular reflection (RR) and Mach reflection (MR) configurations in an unsteady flowfield resulting from shock–vortex interactions can also be explained locally based on limiting conditions similar to that prescribed by the length scale criteria for pseudo-steady flow.

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