Effect of the -Alkyl Side Chain on the Amide-Water Interactions.

Amide-water interactions influence the structure and functions of amide-based systems, such as proteins and homopolymers. In particular, the -alkylation of the amide unit appears to play a critical role in defining the interactions of the amide group. Previous studies have linked the thermal behavior of amide-based polymers to the nature of their -alkyl side chain.

Quantum mechanical effects in acid-base chemistry.

Acid-base chemistry has immense importance for explaining and predicting the chemical products formed by an acid and a base when mixed together. However, the traditional chemistry theories used to describe acid-base reactions do not take into account the effect arising from the quantum mechanical nature of the acidic hydrogen shuttling potential and its dependence on the acid base distance. Here, infrared and NMR spectroscopies, in combination with first principles simulations, are performed to demonstrate that quantum mechanical effects, including electronic and nuclear quantum effects, play an essential role in defining the acid-base chemistry when 1-methylimidazole and acetic acid are mixed together.

Bottom-Up Approach to Assess the Molecular Structure of Aqueous Poly(-Isopropylacrylamide) at Room Temperature via Infrared Spectroscopy.

The structure of poly(-isopropylacrylamide) (PNIPAM) in solution is still an unresolved topic. Here, the PNIPAM structure in water was investigated using a bottom-up approach, involving the monomer, dimer, and trimer, and a combination of infrared (IR) spectroscopies as well as molecular dynamics simulations. The experiments show that the monomer and oligomers exhibit a broad and asymmetric amide I band with two underlying transitions, while PNIPAM presents the same major transitions and a minor one.

Proving and Probing the Presence of the Elusive C-H⋅⋅⋅O Hydrogen Bond in Liquid Solutions at Room Temperature.

Hydrogen bonds (H bonds) play a major role in defining the structure and properties of many substances, as well as phenomena and processes. Traditional H bonds are ubiquitous in nature, yet the demonstration of weak H bonds that occur between a highly polarized C-H group and an electron-rich oxygen atom, has proven elusive. Detailed here are linear and nonlinear IR spectroscopy experiments that reveal the presence of H bonds between the chloroform C-H group and an amide carbonyl oxygen atom in solution at room temperature.

Multiple pharmacophores for the selective activation of nicotinic alpha7-type acetylcholine receptors.

The activation of heteromeric and homomeric nicotinic acetylcholine receptors was studied in Xenopus laevis oocytes to identify key structures of putative agonist molecules associated with the selective activation of homomeric alpha7 receptors. We observed that selectivity between alpha7 and alpha4beta2 was more readily obtained than selectivity between alpha7 and alpha3beta4. Based on structural comparisons of previously characterized selective and nonselective agonists, we hypothesize at least three chemical motifs exist that, when present in molecules containing an appropriate cationic center, could be associated with the selective activation of alpha7 receptors.

Quinuclidines as selective agonists for alpha-7 nicotinic acetylcholine receptors.

The alpha7 subtype of the neuronal nicotinic acetylcholine receptors (nAChRs) was targeted for the design of selective agonists deriving from the quinuclidine scaffold. Arylidene groups at the 3-position and N-methyl quinuclidine were found to be selective agonists with EC(50)s of 1.5 and 40 microM, respectively.