Calculation of the Density and Activity of Water in ATPS Systems for Separation of Biomolecules

In this study, the perturbed hard sphere chain equation of state is utilized to calculate the activity of water in binary and ternary solutions of polyethylene glycol (PEG), salt and water. The liquid density of the binary and ternary solutions is also predicted. To estimate the water activity in PEG–water binary systems, a linear correlation is obtained for the binary interaction parameter between water and PEG. Then, using this correlation and without introducing any additional binary parameters, the water activities are predicted in ternary solutions of water, salt and PEG with different molecular weights (MW). Our results show that the mean absolute average relative deviation (AARD %) of water activity for binary PEG–water solutions in 298 K is 0.73 %. In addition, the water activity in ternary solutions of water and two PEGs with different MW is predicted within 0.31 % AARD %. Furthermore, the AARD % for prediction of water activities in binary PEG–water solutions over the temperature range 308–338 K is 0.41 %. Also, the water activities of aqueous two-phase systems are predicted with AARD % = 0.64 %. In this regard, no adjustable parameters were correlated between salt and PEG. Finally, liquid densities were predicted in binary solutions of water–PEG and ternary solutions of water–PEG–salt.     

Synthesis and Characterization of Poly(Aryl Ether-Bissulfone)s

A series of poly(aryl ether-bissulfone)s were synthesized from bis-phenols, 4,4′-bis(4-chlorophenylsulfonyl)biphenyl, and 4,4′-bis(4-fluorophenylsulfonyl)biphenyl. The bishalide monomers were synthesized by reaction of 4,4′-bis(chlorosulfonyl)biphenyl with a suitable aryl halide. Potassium carbonate mediated reaction in di-methylacetamide gave high molecular weight polymers in excellent yield. The polymers are soluble in dipolar aprotic solvents. Unlike the corresponding monosulfone analogues, the poly(aryl ether-bissulfone)s exhibited poor solubility in chlorinated hydrocarbons. The glass transition temperatures of the polymers are among the highest known for poly(aryl ether)s (241-271 °C). In addition, the polymers exhibit excellent thermal stability and they produce clear, colorless tough films by solution casting or compression molding.     

Synthesis of N‐Protected/Free Indole‐7‐Carboxaldehyde

A direct method for the preparation of N‐protected/free indole‐7‐carboxaldehyde is reported from the corresponding N‐protected 7‐bromomethylindoles using three different conditions.     

Dipyrrolylmethane-based macrobicyclic azacryptand: synthesis, X-ray structures, conformational and anion binding properties

A new class of macrobicyclic azacryptand containing dipyrrolylmethane subunits with nitrogen bridgeheads was synthesized by the Mannich reaction of the dipyrrolylmethane in the presence of aqueous ammonia. The azacryptand exhibits a staggered conformation in the solid state, but is in a dynamic equilibrium with the eclipsed conformation in solution studied by the variable-temperature (1)H NMR methods. The azacryptand has a specific size suitable only for fluoride ion; large anions such as NO(3)(-) bind in the clefts of the macrobicycle as shown by the X-ray structures of its fluoride ion inclusion and the nitrate anion complexes. The anion binding studies showed that it has high selectivity and affinity for fluoride ion in acetone over other anions studied, which was supported by (1)H and (19)F NMR methods. The azacryptand has fast fluoride ion-mediated proton-deuterium exchanges with acetone-d(6) studied by the (19)F NMR method.     

Magnetization and Mössbauer studies of 57Fe doped SrCoO3

⁵⁷Fe (1%) doped SrCoO₃ obtained by high-pressure method, has been investigated by magnetization and Mössbauer spectroscopy studies (MS) in the temperature range 4.2 K to 300 K. The ferromagnetic ordering temperature T _C obtained is 272(2) K. Isothermal magnetization curves have been measured at various temperatures, from which the saturation moments (M _sat) have been deduced. The ⁵⁷Fe MS spectra display standard six-line patterns with an isomer shift typical of Fe^3?+? and a very small quadrupole splitting (QS = 0.14(1) mm/s above T _C). The magnetic hyperfine field at 4.2 K is 276(1) kOe. The temperature dependencies of the iron hyperfine field and M _sat (1.83 µ _B at 5 K) are almost identical. This shows that the Fe^3?+? is replacing Co^4?+?, both of the same electronic configuration. They also interact similarly, namely the Fe–Co exchange is almost identical to the Co–Co exchange.     

Studies on the lattice match and strain in the epitaxial growth of III – V alloys on inas and GaSb substrates

The compositional conditions to deposit the epitaxial films of III – V materials lattice matched to InAs and GaSb substrates have been investigated and the results are presented in the form of charts. The validity of our theoretical predictions has been tested by comparing with the available experimental results. Strain in the Ga_xIn_{1 − x}As_ySb_{1 − y} quaternary alloy has been visualised as three-dimensional perspective plots.     

Making an H $H$-free graph k $k$-colorable

We study the following question: How few edges can we delete from any $H$-free graph on $n$ vertices to make the resulting graph $k$-colorable? It turns out that various classical problems in extremal graph theory are special cases of this question. For $H$ any fixed odd cycle, we determine the answer up to a constant factor when $n$ is sufficiently large. We also prove an upper bound when $H$ is a fixed clique that we conjecture is tight up to a constant factor, and prove upper bounds for more general families of graphs. We apply our results to get a new bound on the maximum cut of graphs with a forbidden odd cycle in terms of the number of edges.     

Leveraging Torsional and Steric Strains: A Pre-macrocyclization Strategy Enables Conformation-Specific Fullerene Binding in m-Cyclophanes

Though the chemistry of resorcinarenes is half a century old, the conformationally-locked resorcinarene crowns are generally constructed using hydrogen bonds or covalent tethers. Often, covalent tethering involves extra post-macrocyclization steps involving upper-rim functionalities. We have leveraged the torsional and steric strains through α-substituents of the lower-rim C-alkyl chains and accomplished conformationally-rigid fluorescent m-cyclophane deep-crowns in a predetermined way. The strategy offers a pre-macrocyclization route conserving upper-rim functionalities, an aspect overlooked in resorcinarene chemistry. X-ray structural and computational analyses unveil the cause for conformational rigidity in m-cyclophanes due to α-branching in C-alkyls (linear vs. α-/β-branched). The conformationally-locked fluorescent deep-crown with a preorganized cavity captures hydrophobic spherical guest C₆₀ in both solution and solid states specifically, when compared to conformationally-dynamic boats, enabling conformation-specific binding.