Crystallographic study of restricted rotation ino-formanilides

The crystal structures ofcis- andtrans-o-methylformanilide, of itscis-thio analogue, and oftrans-o-phenylformanilide have been studied with a view to clarifying the anomalously high barrier to rotation of the carbonyl group. The pair of resolved geometrical isomers is shown to be stabilized in the solid state primarily by hydrogen bonding. The increased barrier to rotation is inferred not to arise from mesomeric involvement of the carbonyl group, but from nuclear screening by the nitrogen lone pair.     

The numerical integration of a molecular integral using two different techniques

A two-electron integral which commonly occurs in molecular calculations is evaluated numerically using the different methods of Boys and Conroy and the results are discussed.This paper was presented during the session on numerical integration methods for molecules of the 1970 Quantum Theory Conference in Nottingham. It has been revised in the light of the interesting discussion which followed.     

An Adsorption Isotherm from a Micro-state Model

The present study is dedicated to the derivation of an alternative adsorption isotherm for liquid-solid interfaces from a micro-state model, where adsorption is predominantly of a chemical nature. We describe adsorption-desorption on a liquid-solid interface starting from a partition function. In the new model the surface site occupation number is controlled by the Pauli principle (monolayer condition) and additional an attractive or repulsive surface potential, which depends on the overall surface coverage (nonlinearity). The effective potential represents adsorbate adsorbent interaction, as well as an influence of adsorbate adsorbate interactions on the surface potential. A Langmuir equivalent isotherm is recovered in the limit of a weak potential. The proposed model and Langmuirs isotherm are compared using data of humic acid (HA) adsorption on Brazilian Oxisol soil samples. Both models parameterize the experimental data well, but only the new model seems to be self-consistent.     

Caged phosphoproteins

We present the chemical and biological synthesis of caged phosphoproteins using the in vitro nonsense codon suppression methodology. Specifically, phosphoamino acid analogues of serine, threonine, and tyrosine with a single photocleavable o-nitrophenylethyl caging group were synthesized as the amino acyl tRNA adducts for insertion into full-length proteins. For this purpose, a novel phosphitylating agent was developed. The successful incorporation of these bulky and charged amino acids into the alpha-subunit of the nicotinic acetyl choline receptor (nAChR) and the vasodilator-stimulated phosphoprotein (VASP) using an in vitro translation system is reported.