Short Molecular Distances Research Articles

Energetic characteristics of 1H-tetrazole/ NaClO4 ionic cocrystal

ABSTRACT The energetic characteristics of a novel ionic cocrystal composed of 1H-tetrazole/sodium perchlorate and differences of properties between the cocrystal and simple mixture are reported herein. Cocrystals containing reductants and oxidizers exhibit enhanced energy release rate compared with their simple mixture owing to their short molecular distances. Differential scanning calorimetry, thermogravimetric analysis, sensitivity tests and humidity tests are performed to clarify the properties of the cocrystals and simple mixture. The calculated detonation velocity of the cocrystal was higher than that of 1H-tetrazole. The cocrystal achieves high deflagration performance, as evaluated via a pressure vessel test.

The Legacy of 20th Century Phage Research.

The Golden Age of Phage Research, where phage was the favored material for attacking many basic questions in molecular biology, lasted from about 1940 to 1970. The era was initiated by Ellis and Delbrück, whose analysis defined the relevant parameters to measure in studying phage growth, and depended on the fact that the contents of a plaque can comprise descendants of a single infecting particle. It ended around 1970 because definitive methods had then become available for answering the same questions in other systems. Some of the accomplishments of phage research were the demonstration by Hershey and Chase that the genetic material of phage T2 is largely composed of DNA, the construction of linkage maps of T2 and T4 by Hershey and Rotman and their extension to very short molecular distances by Benzer, and the isolation of conditionally lethal mutants in T4 by Epstein et al. and in λ by Campbell. The dissection of the phage life cycle into causal chains was explored by Edgar and Wood for T4 assembly and later in the regulation of lysogeny by Kaiser, extended to the molecular level by Ptashne and others. Restriction/modification was discovered in λ by Bertani and Weigle, and the biochemical mechanism was elucidated by Arber and by Smith.

Effect of the Partial Hydrogenation of Hydrophobic Chains on the Mixing of Fluoroalkanols in an Adsorbed Film at the Hexane/Water Interface

The mixed adsorbed film of 1H,1H-perfluorooctanol (DFC8OH) and 1H,1H,2H,2H-perfluorodecanol (TFC10OH) at the hexane/water interface was studied on the basis of interfacial tension measurement and its thermodynamic data analysis. An adsorbed film at any composition of the mixed system as well as those of pure DFC8OH and TFC10OH systems exhibits three states: the gaseous, expanded, and condensed states. Construction of the phase diagram of adsorption clarified that DFC8OH and TFC10OH mix almost ideally in the gaseous and expanded states. On the contrary, the excess Gibbs energy of adsorption gH,E value evaluated in the condensed state was positive. These results are explained by considering the following two factors: (1) The mixing of binary alcohols is accompanied by the loss of dispersion interaction energy due to the difference in extent of fluorination of hydrophobic chains and in their chain length and increases the gH,E value. (2) Since the interchange energy concerning the interaction between dipoles with different dipole moments is negative, the mixing of these alcohols reduces the repulsive force between hydrophilic groups and thus leads to a decrease in the gH,E value. In the gaseous and expanded states, both of above two factors are not effective. On the other hand, the positive gH,E value in the condensed state is attributable to more effective dispersion interaction than the dipole−dipole interaction in short molecular distance, and so factor 1 becomes dominant. Comparison of the gH,E value of the present system with that of the homologous TFC10OH−TFC12OH mixture leads us to a conclusion that the hydrogenation on β-carbons in hydrophobic chains affects appreciably the balance of interactions between hydrophilic and hydrophobic groups which governs the mixing of molecules in adsorbed films.

V-SNARE Actions during Ca 2+-Triggered Exocytosis

Assembly of SNARE proteins between opposing membranes mediates fusion of synthetic liposomes, but it is unknown whether SNAREs act during exocytosis at the moment of Ca(2+) increase, providing the molecular force for fusion of secretory vesicles. Here, we show that execution of pre- and postfusional steps during chromaffin granule exocytosis depends crucially on a short molecular distance between the complex-forming SNARE motif and the transmembrane anchor of the vesicular SNARE protein synaptobrevin II. Extending the juxtamembrane region of synaptobrevin by insertion of flexible "linkers" reduces priming of granules, delays initiation of exocytosis upon stepwise elevation of intracellular calcium, attenuates fluctuations of early fusion pores, and slows rapid expansion of the pore in a linker-length dependent fashion. These observations provide evidence that v-SNARE proteins drive Ca(2+)-triggered membrane fusion at millisecond time scale and support a model wherein continuous molecular pulling by SNAREs guides the vesicle throughout the consecutive stages of exocytosis.

Surface-enhanced nonlinear-optical processes in molecules in a two-oscillator electromagnetic model

~in ~(0) the enhancement of each of the incident optical fields E to E at the molecular site, (2) the renormalization of the effective nonlinear polarizabilities at short molecular distances from the surface, and (3) the change of the outgoing radiation propagator (Green's function) from the free-space Go to Q, due to the presence of the surface. For a metal surface of a given shape, each of these factors may contain possible surface-plasmon — polariton resonances at various frequencies involved.