Molecular Pairing Research Articles

Ordered pairing in liquid metallic hydrogen

We study two possible types of pairing involving the protons of a proposed low-temperature liquid phase of metallic hydrogen. Electron-proton pairing, which can result in an insulating phase, is investigated by using an approximate solution of an Eliashberg-type equation for the anomalous self-energy. A very low estimate of the transition temperature is obtained by including proton correlations in the effective interaction. For proton-proton pairing, we derive a new proton pair potential based on the Abrikosov wave function. This potential includes the electron-proton interaction to all orders and has a much larger well depth than is obtained with linear screening methods. This suggests the possibility of either a superfluid paired phase analogous to that in ${\mathrm{He}}^{3}$, or alternatively a phase with true molecular pairing.

2D NMR observation of pairing in materials forming the reentrant nematic phase

The orientational order parameter ( S xx - S yy ) of the Meier-Saupe order matrix is measured for perdeuterated p-xylene- d 10 dissolved in mixtures of 4-cyano-4'- n-octyloxybiphenyl (8OCB) and 4-cyano-4'- n-hexyloxybiphenyl (6OCB). A strong dependence of ( S xx - S yy ) on the concentration of 6OCB in 8OCB is observed and interpreted in terms of molecular pairing.

Theory of dense hydrogen

Equations of state for molecular and metallic hydrogen are calculated in an accurate and comparable manner by using the density-functional method applied to static lattices. By isolating the electronic energies in this way, attention can be drawn to the relative importance of the protonic degrees of freedom. From the equation-of-state results it can be concluded that a remnant molecular pairing is preferred in a band-overlap metallic state, complete dissociation occurring only at very high densities. An accurate determination of the pressure needed to achieve complete dissociation is shown to require a self-consistent treatment of electron and proton degrees of freedom.

Effect of molecular pairing in the phase transition of solid ortho-hydrogen

The effect of molecular pairing due to electric quadrupole-quadrupole (EQQ) interaction is taken into account in the molecular field theory of phase transition in solid ortho-hydrogen. This effect lowers the transition temperature, as can be expected from the fact that the lowest energy of an isolated pair is fairly lower than that of the pair in the ordered state of the whole crystal. In result, the transition temperature is evaluated as 2.36 K.

Fine structure of the synaptonemal complex: Regular and stereo electron microscopy of deoxyribonuclease-treated whole mount preparations

Summary Whole mount preparations of quail meiotic chromosomes were treated with deoxyribonuclease. This removed the chromatin fibers and left the proteinaceous synaptonemal complex intact. Regular and stereo-electron microscopy of these preparations allowed the following conclusions. o 1. The lateral element is composed of two individual filaments, presumably one for each chromatid. 2. Protein fibers (L-C fibers) emerge as a series of loops from both filaments of the lateral elements and fuse to form the central element. 3. The deoxyribonucleoprotein fibers attach to the lateral elements and loop out laterally in a lampbrush-like configuration. The attachment sites for the chromatin may be clustered to form the chromomeres seen by light microscopy. The apparent absence of DNA in the central element suggests that the synaptonemal complex serves only to pull homologous chromsomes into tight apposition (chromosomal pairing) and that molecular pairing and recombination take place in the region around the synaptonemal complex.

Mechanism of chromosome pairing during meiosis.

Electron microscopy with whole mount preparations has revealed that the synaptonemal complex merely pulls two homologous chromosomes together. Intimate molecular pairing is another matter—probably brought about by connexions between short stretches of single stranded DNA.