Well-ordered tubular crystals of acetylcholine receptor were obtained from suspensions of Torpedo marmorata receptor-rich vesicles. They are composed of pairs of oppositely oriented molecules arranged on the surface lattice with the symmetry of the plane group p2 (average unit cell dimensions: a = 90 A, b = 162 A, gamma = 117 degrees). The receptor in this lattice has an asymmetric distribution...

In order for haploid gametes to fuse during fertilization, microtubules (MTs) must generate forces that are sufficient to move the nuclei together. Nuclear movements during fertilization rely on microtubule-associated proteins (MAPs), many of which have been characterized extensively during mitosis. A useful model system to study MT-dependent forces before nuclear fusion, or karyogamy, is the m...

SoPIP2;1 is one of the major integral proteins in spinach leaf plasma membranes. In the Xenopus oocyte expression system its water channel activity is regulated by phosphorylation at the C terminus and in the first cytosolic loop. To assess its structure, SoPIP2;1 was heterologously expressed in Pichia pastoris as a His-tagged protein and in the non-tagged form. Both forms were reconstituted in...

We predict the nature (attractive or repulsive) and range (exponentially screened or long-range power law) of the electrostatic interactions of oppositely charged, planar plates as a function of the salt concentration and surface charge densities (whose absolute magnitudes are not necessarily equal). An analytical expression for the crossover between attractive and repulsive pressure is obtaine...

We propose an ultrathin metallic structure to produce frequency-selective spoof surface plasmon polaritons (SPPs) in the microwave and terahertz frequencies. Designed on a thin dielectric substrate, the ultrathin metallic structure is composed of two oppositely oriented single-side corrugated strips, which are coupled to two double-side corrugated strips. The structure is fed by a traditional c...

We have identified a protein, BAF1, which has two oppositely oriented, partially overlapping binding sites within a symmetrical sequence located midway between and upstream of the divergently transcribed YPT1 and TUB2 genes of the yeast Saccharomyces cerevisiae. The 120 kd BAF1 protein was purified to near homogeneity and used to delineate the two binding sites and to identify apparent protein ...

Disjunction of maternal and paternal centromeres during meiosis I requires crossing over between homologous chromatids, which creates chiasmata that hold homologs together. It also depends on a mechanism ensuring that maternal and paternal sister kinetochore pairs attach to oppositely oriented microtubules. Proteolytic cleavage of cohesin's Rec8 subunit by separase destroys cohesion between sis...

The interfacial structure of water in contact with TiO2 is the key to understand the mechanism of photocatalytic water dissociation as well as photoinduced superhydrophilicity. We investigate the interfacial molecular structure of water at the surface of anatase TiO2, using phase-sensitive sum frequency generation spectroscopy together with spectra simulation using ab initio molecular dynamic t...

The MvaI restriction endonuclease cuts 5'-CC↓AGG-3'/5'-CC↑TGG-3' sites as indicated by the arrows. N4-methylation of the inner cytosines (C(m4)CAGG/C(m4)CTGG) protects the site against MvaI cleavage. Here, we show that MvaI nicks the G-strand of the related sequence (CCGGG/CCCGG, BcnI site) if the inner cytosines are C5-methylated: C(m5)C↓GGG/CC(m5)CGG. At M.SssI-methylated SmaI sites, where tw...