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Calmodulin (CaM) regulates the activity of a Ca2+ channel known as the cardiac ryanodine receptor (RyR2), which facilitates the release of Ca2+ from the sarcoplasmic reticulum during excitation-contraction coupling in cardiomyocytes. Mutations that disrupt this CaM-dependent channel inactivation result in cardiac arrhythmias. RyR2 contains three different CaM binding sites: CaMBD1 (residues 1940-1965), CaMBD2 (residues 3580-3611), and CaMBD3 (residues 4246-4275). Here, we report a crystal structure of Ca2+-bound CaM bound to RyR2 CaMBD3. The structure reveals Ca2+ bound to the four EF-hands of CaM as well as a fifth Ca2+ bound to CaM in the interdomain linker region involving Asp81 and Glu85. The CaM mutant E85A abolishes the binding of the fifth Ca2+ and weakens the binding of CaMBD3 to Ca2+-bound CaM. Thus, the binding of the fifth Ca2+ is important for stabilizing the complex in solution and is not a crystalline artifact. The CaMBD3 peptide in the complex adopts an α-helix (between Phe4246 and Val4271) that interacts with both lobes of CaM. Hydrophobic residues in the CaMBD3 helix (Leu4255 and Leu4259) form intermolecular contacts with the CaM N-lobe, and the CaMBD3 mutations (L4255A and L4259A) each weaken the binding of CaM to RyR2. Aromatic residues on the opposite side of the CaMBD3 helix (Phe4246 and Tyr4250) interact with the CaM C-lobe, but the mutants (F4246A and Y4250A) have no detectable effect on CaM binding in solution. We suggest that the binding of CaM to CaMBD3 and the binding of a fifth Ca2+ to CaM may contribute to the regulation of RyR2 channel function.

Bimetallic (Ag-Au/Au-Ag) nanoparticles have been synthesized using Litchi chinesis leaf extract and characterised using UV-visible spectroscopy, dynamic light scattering (DLS), zeta potential and transmission electron microscopy (TEM). The hydrodynamic size of Ag-Au/Au-Ag NPs are found to be 83 nm/90 nm, respectively, by DLS techinque. The catalytic capability of green synthesised silver, gold and bimetallic(Ag-Au) nanoparticles is described in this study by choosing the degradation of methylene blue, as a model dye. [ABSTRACT FROM AUTHOR]

The influence of dipeptide glycyl-l-valine (gly-l-val) on the micellization and surface active properties of two different gemini surfactants varying in their spacer group i.e. ethylene-1,2-bis (N,N-dimethyl-N-dodecylammonium bromide) (12–2–12) and hexamethylene-1,6-bis-(N,N-dimethyl-N-dodecylammonium bromide) (12–6–12) was explored using tensiometry as well as conductivity technique. Conductivity measurements at several temperatures (293.15, 298.15, 303.15 and 308.15) K and tensiometric measurements at 298.15 K at several concentrations of dipeptide (0.02, 0.04 and 0.06) mol/kg were conducted so as to deduce the interactions amid dipeptide and two surfactants. Several parameters viz. critical micelle concentration (CMC) as well as the degree of ionization (α) along with various parameters associated with thermodynamics; standard entropy of micellization ( Δ S m 0 ), Gibbs free energy of micellization ( Δ G m 0 ) and standard enthalpy of micellization ( Δ H m 0 ) have been evaluated through conductivity data. Various additional thermodynamic parameters such as free energy of adsorption ( Δ G a d 0 ) and surface free energy (G min s ) have been also estimated through surface tension measurements. [ABSTRACT FROM AUTHOR]

The study aims to scrutinize the mixed micellization and interfacial behavior of two 1-alkyl-3-butylimidazolium based surface-active ionic liquids (SAILs) i.e., 1-decyl-3-butylimidazolium bromide [C10bim][Br] and 1-tetradecyl-3-butylimidazolium bromide [C14bim][Br] under the influence of streptomycin sulphate (SS) drug in 5 mM concentration in aqueous media. Imidazolium-based SAILs have unique physicochemical properties and greater surface activity than conventional surfactants, which allows them to increase drug permeability, making them better drug carriers than currently available formulations. To fully utilize [C14bim][Br] and [C10bim][Br] in drug delivery applications, deep insight into the interactions occurring in the mixed micellar [C10bim][Br]/[C14bim][Br] systems in the drug's presence are necessary to be examined. Thus, the study is conducted using conductivity and surface tension measurement techniques to fully exploit the self-assembly, micellization behavior and interactions occurring in the pure and mixed micellar system of [C10bim][Br]/[C14bim][Br] in water and 5 mM of SS solution in aqueous media. For this, various thermodynamic, surface-active and mixed micellar parameters of micellization have been calculated and analyzed with respect to change in mole fraction, temperature and addition of SS in solution. [ABSTRACT FROM AUTHOR]

Molecular interactions present between 1-pentadecyl-3-methylimidazolium bromide and the biologically important amino acid additives (glycine, l-alanine, and l-valine) have been examined in aqueous media by employing conductivity, UV–Visible, refractive index, and FT-IR spectroscopy at different compositions and temperatures. Furthermore, using the electrical conductivity data, critical micelle concentration, degree of counter-ion dissociation, and various thermodynamic parameters of micellization have been computed. To study the interactions in the micellar system, the effects of additives on these parameters have been carefully analyzed. UV–Visible and refractive index are carried out to outline the results stated above, along with FT-IR results to confirm the various interactions prevailing in the system. [ABSTRACT FROM AUTHOR]

Byline: Rupinder. Singh, Ramanjeet. Kaur, Pawan. Pokhariyal, Rajul. Aggarwal Sir, Chikungunya, a relatively rare and benign form of viral infection caused by a RNA-virus belonging to the genus Alphavirus of [...]