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Molecular interactions and controlled expression of enzymatic activities are fundamental to all cellular functions in an organism. The active polyphenol in turmeric known as curcumin (CCM) is known to exhibit diverse pharmacological activities. Ribonucleases (RNases) are the hydrolytic enzymes that plays important role in ribonucleic acid (RNA) metabolism. Uncontrolled and unwanted cleavage of RNA by RNases may be the cause of cell death leading to disease states. The protein ribonuclease A (RNase A) in the superfamily of RNases cleaves the RNA besides its role in different diseases like autoimmune diseases, and pancreatic disorders. Interaction of CCM with RNase A have been reported along with the possible role of CCM to inhibit the RNase A enzymatic activity. The interaction strength was found to be 104 M−1 order from spectroscopic results. Quenching of RNase A fluorescence by CCM was 104 M−1 order. Non-radiative energy transfer from RNase A (donor) to CCM (acceptor) suggested a distance of 2.42 nm between the donor–acceptor pair. Circular dichroism studies revealed no structural changes in RNase A after binding. Binding-induced conformational variation in protein was observed from synchronous fluorescence studies. Agarose gel electrophoresis revealed a partial inhibition of the RNase A activity by CCM though not significant. Molecular docking and molecular dynamics studies suggested the residues of RNase A involved in the interaction with supporting the experimental finding for the partial inhibition of the enzyme activity. This study may help in designing new CCM analogues or related structures to understand their differential inhibition of the RNase A activity. [ABSTRACT FROM AUTHOR]

For the determination of tin(II) traces, an extractive spectrophotometric approach is devised. The applied method serves a powerful tool for determination of tin(II), involves the formation of yellow colored complex after the binding of 6-bromo-3-hydroxy-2-(5-methylfuran-2-yl)-4H-chromen-4-one (BHMF) and tin(II) in 1:2 stiochiometry in a slightly acidic medium (HCl). The complex shows absorbance at 434 nm with respect of the blank reagent. The outcomes of spectral investigation for complexation showed a Beer's range of 0–1.3 μg Sn mL−1, molar absorptivity, specific absorptivity and Sandell's complex sensitivity are 9.291 × 104 L mol−1 cm−1, 0.490 mL g−1 cm−1 and 0.002040 μg cm−2 at 434 nm that was stable for two days. The interferences study results showed that this method is free from interferences, when tested with metal ions including Ag, Be, Bi, Ca, Cd, Ce, Co, Hg, Mo, Re, Pt, Se,Ti, U, V, W and other common cations, anions, and complexing agents. The applied method is quite simple, highly selective, and sensitive with good re-producibility. This method has been satisfactorily by utilizing the proposed procedure, and its applicability has been tested by analyzing synthetic samples and an alloy sample of gunmetal. The procedure assumes this because of the scarcity of better methods for determining tin(II). The results are in good agreement with the certified value. [ABSTRACT FROM AUTHOR]

Five novel bright orange color emitting Sm(III) complexes (C1-C5) have been synthesized via energy efficient and cost effective solution precipitation method with 5-phenyl 2-furoic acid as primary organic sensitizer and nitrogen donor neocuproine, 2, 2- bipyridyl, bathophenanthroline, and 1,10-phenanthroline as secondary ligands. All the newly synthesized metal complexes are thoroughly characterize to examine the appropriateness of the organic ligand for the sensitization process. All the outcomes of the various advanced and fundamental spectroscopic techniques validate the bonding of carboxylate group with the Sm(III) ion. The luminescence spectra reflects the dominance of magnetic dipole transition which designate the occurrence of harmonized chemical environment in the coordination sphere which is further validated by enhanced values of intensity ratio. These complexes possess suitable thermal stability with excellent photoluminescent features as confirmed by thermogravimetric analysis and photoluminescence studies. The luminescence lifetime of samarium complexes [C2-C5] is relatively long due to the synergistic effect presented by ancillary ligands. The emission color of the synthesized complexes show shift from orange to bright orange red color which is displayed through CIE color coordinates. [ABSTRACT FROM AUTHOR]

The interaction between Trp-Arg dipetide (WR) and calf thymus DNA (ctDNA) in pH 7.4 Tris-HCl buffer was investigated by multi-spectroscopic techniques and molecular modeling. The fluorescence spectroscopy and UV absorption spectroscopy indicated that WR interacted with ctDNA in a minor groove binding mode and the binding constant was 4.1 × 10. The ionic strength effect and single-stranded DNA (ssDNA) quenching effect further verified the minor groove binding mode. Circular dichroism spectroscopy (CD) was employed to measure the conformation change of ctDNA in the presence of WR. The molecular modeling results illustrated that electrostatic interaction and groove binding coexisted between them and the hydrogen bond and Van der Waals were main acting forces. All the above methods can be widely used to investigate the interaction of peptide with nucleic acids, which contributes to design the structure of new and efficient drugs. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]