The room-temperature liquid salt, ethylammonium nitrate~EAN!, has been used to enhance the recovery of denaturedreduced hen egg white lysozyme~HEWL!. Our results show that EAN has the ability to prevent aggregation of the denatured protein. The use of EAN as a refolding additive is advantageous because the renaturation is a one-step process. When HEWL was denatured reduced using routine procedures and renatured using EAN as an additive, HEWL was found to regain 75% of its activity. When HEWL was denatured and reduced in neat EAN, dilution resulted in over 90% recovery of active protein. An important aspect of this process is that renaturation of HEWL occurs at concentrations of 1.6 mg0mL, whereas other renaturation processes occur at significantly lower protein concentrations. Additionally, the refolded-active protein can be separated from the molten salt by simple desalting methods. Although the use of a low-temperature molten salt in protein renaturation is unconventional, the power of this approach lies in its simplicity and utility.

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This paper describes the design, synthesis, and characterization of a hydrogen-bonded molecular duplex (3‚4). Two oligoamide molecular strands, 3 and 4, with the complementary hydrogen-bonding sequences ADAADA and DADDAD, respectively, were found to form an extremely stable (K a ) (1.3 ( 0.7) × 10 9 M -1 ) molecular duplex (3‚4) in chloroform. Evidence from 1D and 2D 1 H NMR spectroscopy, isothermal titration calorimetry, and thin-layer chromatography confirmed the formation and the high stability of the duplex. The exceptional stability is explained by positive cooperativity among the numerous hydrogen-bonding and van der Waals interactions and the preorganization of the individual strands by intramolecular hydrogen bonds. This design has opened a new avenue to supramolecular recognition units with programmable specificities and stabilities.

This paper presents the effect of additives on the mechanism and selectivity of the SmI2-mediated coupling of alkyl halides and ketones. The reaction of 1-iodobutane and 2-octanone was carried out with SmI2 in the absence of cosolvent and in the presence of HMPA, LiBr, and LiCl. The experiments using cosolvent free SmI2 and SmI2−HMPA reductants gave the Barbier product, 5-methyl-5-undecanol predominantly. The same procedure carried out with LiBr as an additive produced the pinacol product, 7,8-dimethyl-7,8-tetradecanediol, exclusively. A careful product analysis of the SmI2-mediated coupling of 1-iodododecane and 2-octanone in the presence of LiBr, LiCl, and HMPA was also performed. The combination of SmI2 and LiBr again produced the pinacol coupling product exclusively and left the 1-iodododecane unreduced. In contrast, the SmI2−HMPA combination gave only the Barbier product. Analysis of the Sm(II) reductants employing cyclic voltammetry and UV−vis spectroscopy coupled with reaction protocol changes and mechanistic studies led to the conclusion that the SmI2-mediated coupling of alkyl halides and carbonyls in the presence of HMPA gives the Barbier product through an outer-sphere electron-transfer process, while the reaction utilizing SmI2 with LiBr or LiCl gives the pinacol product through an inner-sphere reductive coupling of ketones. The results presented herein show that it is possible to alter the reactivity and selectivity of Sm(II) reagents through the choice of additives or cosolvents, primarily by changing the steric bulk around the reductant.

Native coals are strained and glassy. When coals are swollen, this strain is relieved as the coal structure rearranges to a lower free energy and more highly noncovalently associated state. Four coals ranging in carbon content from 77% C to 84% C were warmed in the weak swelling solvent chlorobenzene at 132 °C for 2 weeks and samples were withdrawn at intervals. After evaporation of the chlorobenzene, the pyridine extractability of the treated coals had decreased, sometimes by a factor of 2. The pyridine swelling of Pittsburgh No. 8 coal was sharply reduced. The extractability and swelling decreases with time demonstrate that changes in coal structure occurred with the rearranged coal being more associated. This increased association is not due to hydrogen bond formation because pyridine is known to break most if not all of the hydrogen bonds which occur in coals. The rearranged Pittsburgh No. 8 coal was studied by differential scanning calorimetry. Over the 2 week chlorobenzene reflux period, the heat capacity decreased by a factor of 2, demonstrating that the coal rearranged to a more highly associated, more rigid structure. X-ray diffraction studies show enhanced intensity for a regular structural feature occurring at about 20 Å with no other alterations, including the aromatic face to face stacking. The observation that the rearrangement occurs in a day or two in pyridine at room temperature and the absence of a decrease in the radical population argue against increases in covalent bonding as the source of the observed changes. We believe the driving force for the rearrangement is the release of stored elastic strain. Coal swelling provides the macromolecule with the opportunity to undergo conformational rearrangements and to adopt a lower free energy more highly associated structure. The behavior of the high-rank Upper Freeport coal is opposite in direction to the lower rank coals. It apparently rearranges to a less associated structure.