The energetics of naphthalene derivatives. II. The isomeric 1— and 2—naphthyl acetates

The isomeric 1- and 2-naphthyl acetates (acetoxynaphthalenes) are at the confluence of diverse concepts, techniques and classes of organic compounds. Summing the results of literature measurements of the enthalpy of formation of their solids and of our new sublimation enthalpies reported herein, we derive gas phase enthalpies of formation of ?209.9 ± 1.4 and ?213.3 ± 1.3 kJ mol^?1 respectively. This corresponds to 2-naphthyl acetate being more stable than its 1-isomer by 3.4 ± 1.9 kJ mol^?1. We also performed MP2(full)/6-31G(d) calculations on these species, resulting in enthalpies of formation of ?212.9 ± 3.9 and ?212.2 ± 3.9 kJ mol^?1 for 1- and 2-naphthyl acetate and a difference of ?0.7 kJ mol^?1 respectively in satisfactory agreement with the above experimental results.     

The phase behaviour of a fluid in a slitlike pore with permeable walls

The confinement of a lattice fluid in a set of slitlike pores separated by semipermeable walls with a finite width has been studied. The walls are modelled by a square-well repulsive potential with a finite height. The thermodynamic properties and the phase behaviour of the system are evaluated by means of Monte Carlo simulations. For some states theoretical calculations have been made using a mean-field-type theory. These investigations confirm previous findings for confined Lennard-Jones fluids, obtained from a density functional approach. For intermediate and low potential barriers that separate the pores, the isotherms exhibit two hysteresis loops and the liquid-vapour coexistence curve divides into two branches describing condensation inside the pore and inside the permeable wall. These two branches are separated by a triple point. At temperatures lower than the triple point temperature, the condensation takes place instantaneously in both the pore and inside the permeable wall. It was found that when the temperature is scaled by the bulk critical temperature, the phase diagram emerging from this simple mean-field treatment is close to the phase diagram obtained from simulation.     

Second-order Percus–Yevick theory for the radial distribution functions of a mixture of hard spheres in the limit of zero concentration of the large spheres

The radial distribution functions of a mixture of hard spheres are quite interesting when the ratio of diameters is large and the concentration of the large spheres is very small. In this regime, the radial distrbution functions change rapidly with concentration. The usual PercusYevick theory, which is adequate over most of the concentration range, fails at low concentrations of the large spheres. Values are reported of the radial distribution functions for zero concentration of the large spheres using the most accurate theory presently available, secondorder Percus-Yevick theory. Agreement with recent formulae for the contact values of these functions is very good except for the contact value for a pair of large spheres, where the agreement is fairly good. It is possible that the radial distribution function for a pair of large spheres may be a little larger than the already large values given by this recent formula.     

Phase behaviour of a Lennard-Jones fluid in a pore with permeable walls of a finite thickness: a density functional approach

A confinement of a Lennard-Jones fluid in a system of slitlike pores separated by semipermeable walls of a finite width is studied. The walls are modelled by square-well repulsive potential wells. The structure of the confined fluid is investigated by means of a density functional method. For high potential barriers separating the pores, the phase behaviour of the system is similar to that for a single slitlike pore with impenetrable walls. For intermediate and low potential barriers the system shows different phase behaviour. Within some temperature range the isotherms exhibit two hysteresis loops, which characterize the condensation of the fluid in different parts of the system, namely in the pore and inside the semipermeable walls. The systems characterized by low and intermediate potential barriers exhibit the triple point, such that at temperatures below that triple point the condensation instantaneously takes place in both the pore and inside the permeable wall.     

Monte Carlo study of the selectivity of calcium channels: improved geometrical model

An extended model of a calcium channel is described involving a channel with a finite length. With this new geometry the channel is still selective but less so than in an infinite cylinder geometry (Boda, D., Busath, D. D., Henderson, D., and Sokolowski, S., 2000, J. phys. Chem. B, 104, 8903). The selectivity of the channel depends on the width and length of the channel filter but is not significantly affected by changes in the size of the entry vestibules. Interestingly, changes in the size of the entry vestibules do affect the details of the concentration profiles of some of the ions.     

Heuristic Programming

In this paper we take a general look at the nature of currentheuristic programming, its philosophy, and the justificationof its use in specific problem instances.     

THE ENZYMOLOGY AND MOLECULAR BIOLOGY OF THE Ca2+-ACTIVATED PHOTOPROTEIN, AEQUORIN

Aequorin is a bioluminescent protein, isolated from the hydromedusan Aequorea victoria. A recombinant cDNA plasmid (pAEQ1) was shown to encode apoaequorin by detecting photoprotein activity in an extract of an E. coli strain containing pAEQ1 (Prasher et al., 1986, Biochem. Biophys. Res. Comm. 126, 1259-1268). The nucleotide sequence of the pAEQ1 insert has been determined and is shown to differ significantly from the aequorin cDNA (AQ440) isolated by Inouye et al. (1985, Proc. Natl. Acad. Sci. USA 82, 3154-3158). Comparisons of the coding regions of the two cDNAs show there are 52 nucleotide differences, 19 of which are responsible for 18 amino acid replacements. These differences explain the microheterogeneity observed at 17 positions during the sequencing of native apoaequorin. Five aequorin isotypes extracted from Aequorea tissue are observed on 2-dimensional gels and the E. coli-expressed apoaequorin is shown to co-migrate with one of these isotypes. The multiple isotypes could be caused by the presence of a multi-gene family since Southern blot analysis of Aequorea DNA suggests the presence of a minimum of four aequorin genes. Immunoblot analysis suggests that purified native aequorin is proteolytically cleaved during its purification from Aequorea. Comparison of the deduced cDNA translations and the protein sequence suggests the loss of seven residues from the amino terminal. Overexpression of the apoaequorin cDNA in E. coli now provides the means of obtaining gram quantities of a single isotype of the protein which can be converted to aequorin in the presence of coelenterate luciferin, oxygen and an appropriate thiol. Proper extraction procedures and a single chromatographic step provides apoaequorin which is greater than 95% homogeneous.     

A COMPARATIVE STUDY OF THE PHOTOCHEMISTRY OF THE NON-STEROIDAL ANTI-INFLAMMATORY DRUGS, NAPROXEN, BENOXAPROFEN AND INDOMETHACIN

Abstract— The photochemical reactivity of the non-steroidal anti-inflammatory drugs, naproxen and indomethacin, has been studied and compared with benoxaprofen, a similar compound of known cutaneous phototoxicity. Although indomethacin shows some phosphorescence at 77 K, flash photolysis at room temperature revealed only a weak photoionization process, and no photochemical reactivity was detected in steady state photolysis. Naproxen has strong fluorescence and phosphorescence, and in laser flash photolysis showed photoionization and a triplet state species in approximately equal yield. Naproxen and benoxaprofen produced singlet oxygen with similar quantum yield, as deduced from the sensitized rates of photooxidation of 2,5-dimethylfuran. Naproxen underwent photodecarboxylation as detected by ESR-spin trap experiments with 2-methyl-2-nitrosopropane. The decarboxy-naproxen radical combined readily with oxygen in aerated solution, and l-(6-methoxy-2-napthyl)ethanol and 2-acetyl-6-methoxynaphthalene were formed as the oxidation products. In deaer-ated solution, the major product was 2-ethyI-6-methoxynaphthalene, with the alcohol also formed. In comparison, benoxaprofen also underwent decarboxylation, with much higher quantum yield, but the decarboxy-benoxaprofen radical did not add oxygen. This difference in photoreactivity between naproxen and benoxaprofen, together with the much lower molar absorptivity of naproxen are the significant factors in relating to the differences in reported levels of clinical photosensitivity responses.     

Monte Carlo data of dilute solutions of large spheres in binary hard sphere mixtures

Monte Carlo (MC) simulation data for additive binary hard sphere mixtures are reported for dilute concentrations of the large sphere. Using a single occupancy linked cell method, binary hard sphere solutions with a size ratio of 5 are simulated at high reduced density and low concentration of the large sphere. Data for the solute-solvent pair distribution function show that at the lowest concentrations of the large sphere simulated, the Boublik-Mansoori-Carnahan-Starling-Leland (BMCSL) equation underestimates the contact value; whereas the recently proposed Henderson-Chan (HC) equation gives a good prediction. For the solute-solute contact value at the colloidal limit, the MC data lie between the two predictions. The BMCSL equation underestimates, while the HC equation overestimates, the correct solute-solute contact value.     

Vapour-liquid equilibrium of the charged Yukawa fluid from Gibbs ensemble Monte Carlo simulations and the mean spherical approximation

A Gibbs ensemble Monte Carlo (GEMC) study supplemented by theoretical calculations using the mean spherical approximation (MSA) is reported for the charged Yukawa system. In this system the particles interact via an attractive Yukawa potential and a Coulomb potential. When the Coulomb potential is weak compared to the Yukawa attraction the results obtained for the vapour-liquid equilibrium from the GEMC and the MSA are very similar. On increasing the charge, the system becomes similar to the primitive model of electrolytes, and at high charges similar phenomena, such as ion association, are observed. At these charges, the MSA yields poorer results. Using both methods, an increase of the charge results in an increase of the critical temperature but a decrease of the critical density.