Translational Dynamics of Lipidated Ras Proteins in the Presence of Crowding Agents and Compatible Osmolytes

Ras proteins are small GTPases and are involved in transmitting signals that control cell growth, differentiation, and proliferation. Since the cell cytoplasm is crowded with different macromolecules, understanding the translational dynamics of Ras proteins in crowded environments is crucial to yielding deeper insight into their reactivity and function. Herein, the translational dynamics of lipidated N‐Ras and K‐Ras4B is studied in the bulk and in the presence of a macromolecular crowder (Ficoll) and the compatible osmolyte and microcrowder sucrose by fluorescence correlation spectroscopy. The results reveal that N‐Ras forms dimers due to the presence of its lipid moiety in the hypervariable region, whereas K‐Ras4B remains in its monomeric form in the bulk. Addition of a macromolecular crowding agent gradually favors clustering of the Ras proteins. In 20 wt % Ficoll N‐Ras forms trimers and K‐Ras4B dimers. Concentrations of sucrose up to 10 wt % foster formation of N‐Ras trimers and K‐Ras dimers as well. The results can be rationalized in terms of the excluded‐volume effect, which enhances the association of the proteins, and, for the higher concentrations, by limited‐hydration conditions. The results of this study shed new light on the association state of these proteins in a crowded environment. This is of particular interest for the Ras proteins, because their solution state—monomeric or clustered—influences their membrane‐partitioning behavior and their interplay with cytosolic interaction partners.     

Wang-aldehyde resin as a recyclable support for the synthesis of alpha,alpha-disubstituted amino acid derivatives

Merrifield resin was functionalised with hydroxybenzaldehyde under microwave irradiation. The resultant resin was used as a means for immobilisation and activation of alpha-amino acid esters for alkylation reactions. Alpha,alpha-disubstituted and cyclic amino acid esters were prepared in good yields.     

Synthesis of diverse β-(nitrooxy)-substituted amines by regioselective ring-opening of aziridines under neat conditions

An efficient and regioselective method was developed for the synthesis of β-(nitrooxy)-substituted amine derivatives by ring-opening of different aziridines with Zn(NO₃)₂·6H₂O without using additives or catalyst. A library of β-(nitrooxy)-substituted amine derivatives having a variety of substituents has been synthesized. Excellent regioselectivity, high yields, clean reaction, ease of product isolation, easily accessible reactants, and solvent-free as well as environment friendly reaction conditions are the notable advantages of the present methodology. The nitrooxy derivative was successfully transformed into hydroxy derivative by simple reduction. Gram-scale synthesis demonstrates the potential applications of the present method.     

Physicochemical properties and supercapacitor behavior of electrochemically synthesized few layered graphene nanosheets

Journal of Solid State Electrochemistry - The study emphasizes on the scalable production and comparison of few layered graphene nanosheets (FLGNSs). The FLGNSs have been electrochemically...     

Chemoselective Reduction of Some Condensates derived from Chromone-3-carbaldehyde using Sm and Zn

Condensates 4–6 undergo reductive dimerization with Sm in THF containing aqueous NH₄Cl to produce 7–9, whereas with Zn under similar reaction condition 3–5 produce 10–12.     

Phenylacetylene: A Hydrogen Bonding Chameleon

Molecules with multiple hydrogen bonding sites offer the opportunity to investigate competitive hydrogen bonding. Such an investigation can become quite interesting, particularly when the molecule of interest has neither lone‐pair electrons nor strongly acidic/basic groups. Phenylacetylene is one such molecule with three hydrogen bonding sites that cannot be ranked into any known hierarchical pattern. Herein we review the structures of several binary complexes of phenylacetylene investigated using infrared optical double‐resonance spectroscopy in combination with high‐level ab initio methods. The diversity of intermolecular structures formed by phenylacetylene with various reagents is remarkable. The nature of intermolecular interaction with various reagents is the result of a subtle balance between various configurations and competition between the electrostatic and dispersion energy terms, while trying to maximize the total interaction strength.     

Tandem synthesis of [1,2,4]-triazoles mediated by iodine—a regioselective approach

A tandem regioselective one-pot synthesis of 3-amino-[1,2,4]-triazoles has been achieved from 1,3-disubstituted thioureas using molecular iodine. In this one-pot strategy, the intermediate carbodiimide generated in situ from thiourea upon reaction with HCONHNH₂ gives diaryl/alkylhydrazinecarboximidamide or acylureidrazone, which then undergoes an intramolecular cyclodehydration to afford the corresponding 3-amino-[1,2,4]-triazole. The product regioselectivity for unsymmetrical 1,3-disubstituted thioureas correlate well with the pK_as of the parent amines attached, in which the amine having higher pK_a goes to the ring nitrogen while the other nitrogen remains flanked as an exocyclic nitrogen of the triazole core. This method is milder and environmentally sustainable giving good to excellent yields of the desired products.     

Sodium 1, 4‐dihydroxy‐9, 10‐anthraquinone‐ 2‐sulphonate interacts with calf thymus DNA in a way that mimics anthracycline antibiotics: an electrochemical and spectroscopic study

The anthracycline drugs, adriamycin and daunorubicin, efficient in the treatment of various human cancers, form strong intercalation complexes with DNA. The therapeutic efficiency and toxic properties of the drugs are associated with electron transfer processes, which correlate well with the redox behaviour of the compounds. Sodium 1,4‐dihydroxy 9,10‐anthraquinone‐2‐sulphonate (sodium quinizarin‐2‐sulphonate, NaLH₂) (Na‐Qz‐2S) is a molecule that resembles anthracycline drugs and has a simpler structure in comparison to these drugs. Two electrons in the course of chemical action reduce this molecule like the anthracyclines. Electrochemical methods were used to identify this process. UV‐Vis and fluorescence spectroscopy were used to analyse binding of the compound to calf thymus DNA. The binding constant and site size were evaluated for Na‐Qz‐2S and the same compared to that of the anthracyclines. Such comparisons are essential in order to understand whether the simpler hydroxy‐anthraquinones can be a substitute for anthracycline drugs in cancer chemotherapy. Copyright © 2009 John Wiley & Sons, Ltd.     

The anion exchange behavior of Te and Sb

The absorption behavior of Te and Sb in different oxidation states by anion exchange resins in hydrochloric acid medium has been studied. Distribution coefficients for Te(IV), Te(VI) as a function of HCl acid concentration (upto 3M HCl) have been determined. The absorbability for Sb(III) was noticed to be very high and could not be eluted out of the column using HCl as eluent. Sb(V) could be eluted quantitatively using 3M HCl. The present study clearly indicate that due to the EC/β⁺ decay of the parent isotopes^117,118Te, the daughter nuclei^117,118Sb are produced predominantly as Sb(III).     

Recoil ranges of nuclei produced in α-induced reactions on 1107 109Ag and 115In

Integral recoil ranges of evaporation residues for the reactions ¹⁰⁷Ag(α, 3n), ¹⁰⁷Ag(α, α2n), ¹⁰⁹Ag(α, 2n), ¹⁰⁹Ag(α, 3n), ¹⁰⁹Ag(α, 4n), ¹¹⁵In(α, 2n), ¹¹⁵In(α, 3n) and ¹¹⁵In(α, αn) have been measured in the energy range of 202 - 60 MeV α-particles using the conventional thick target thick catcher technique. Transfer of linear momenta to the product nuclei for the above reactions have been deduced from experimental recoil range data. Detailed comparisons of the observations with predictions of theoretical calculations based on statistical model are presented and discussed. For (α, xn) reactions, overall agreement between the theory and the experiment is found to be satisfactory specially at low projectile energy. In cases of (α, αxn) reactions, the theory failed to reproduce the experimental linear momentum transfer even at low incident alpha energy.