Aquaporin-11: A channel protein lacking apparent transport function expressed in brain

Background  

The aquaporins are a family of integral membrane proteins composed of two subfamilies: the orthodox aquaporins, which transport only water, and the aquaglyceroporins, which transport glycerol, urea, or other small solutes. Two recently described aquaporins, numbers 11 and 12, appear to be more distantly related to the other mammalian aquaporins and aquaglyceroporins.     

Partial cross sections and density-of-states effects in the valence-band photoemission from solid nitrogen

Photoelectron energy distribution curves from solid nitrogen were measured for excitation energies to 40 cV using synchrotron radiation. Partial cross sections for emission from 3σ_g, 1π_u and 2σ_u derived valence bands show pronounced mauna 3, 4, 2.9 and 3.0 eV above the vacuum levels, interpreted as due to high density of conduction-band final states. These states are related to π*_g negative-ion shape resonances.     

Mechanistic model for the dielectric spectrum of a simple dielectric material

ABSTRACT

In this paper, we perform molecular dynamics simulations of a dielectric fluidic material composed of permanent molecular dipoles. The dielectric spectrum features two peaks at lower frequencies than the system phonon frequency. The primary peak is observed at all temperatures studied and shifts toward lower frequencies as the temperature decreases. During this shift, the secondary peak emerges with a higher peak frequency than the primary peak. The secondary peak amplitude increases as the temperature decreases. Both peaks are dependent on the wavevector; in the small wavevector regime, the primary peak is shifted to higher frequencies as the wavevector squared and the secondary peak amplitude increases as the wavevector increases, but shows no shift in frequency. From the polarisation balance equation, we propose a model for the dielectric spectrum. This captures the spectrum features, and we conjecture that the primary peak is due to dipole moment correlations (Debye-type) and the secondary peak is due to the correlation between the dipole moment and a microscopic local field.     

Electronic band structure of solid CO2 as determined from the hv-dependence of photoelectron emission

Photoelectron energy distribution curves from solid CO₂ have been determined for excitation energies from hv = 14 up to 40 eV using synchrotron radiation. A 1:1 correspondence to the gas-phase photoelectron spectrum is observed for the occupied molecular orbitals. The vertical binding energies E_B^v (E_VAC = 0) and widths (fwhm) of the valence bands of solid CO₂ are determined to be 13.0 and 0.95 eV (1π_g); 16.7 and 1.1 eV (1π_u); 17.6 and 0.85 eV (3σ_u) and 18.8 and 0.8 eV (4σ_g) for the individual bands respectively. The partial photoemission cross sections differ importantly from those of the gas phase in exhibiting pronounced maxima at 5.2 eV (1π_g), 4.4–5.3 eV (1π_u + 3σ_u) and 4.2 eV (4σ_g) above the vacuum level, which is attributed to effects of high density of final (conduction-band) states. Further weaker maxima are observed at higher photon energies. Contrary to the case for the gas phase, the resonances are unperturbed in the solid by degenerate autoionizing molecular Rydberg states. The molecular origin of the resonances in the continuum is discussed and related to X-ray absorption spectra, electron-scattering data and to theoretical cross-section calculations. It is shown that the same set of resonances is observed in the different experiments. The resonances occur however at different energies due to different Coulomb interactions. The photoemission results presented provide also a key to the hitherto unexplained optical spectrum of solid CO₂ in the VUV range, making possible an assignment of the structures observed to Frenkel-type excitons (hv ≤ 15 eV) and interband transitions (hv ? 15 eV).     

Size of the light-emitting region in a sonoluminescing bubble

The size of the light-emitting region is a key parameter toward understanding the light-emitting processes in a sonoluminescing bubble. Here we present measurements of interference effects from particles with a diameter of approximately 2 microm situated 6-10 microm from a sonoluminescing bubble. From the angular size of the pattern and from an estimated distance to the particles we conclude that the light-emitting region of a sonoluminescing bubble is smaller than commonly believed [see, e.g., Nature (London) 398, 402 (1999)]. We argue that an upper limit of the size of the light-emitting region is approximately 200 nm.     

Minimal model for Beta relaxation in viscous liquids

Contrasts between beta relaxation in equilibrium viscous liquids and glasses are rationalized in terms of a double-well potential model with structure-dependent asymmetry, assuming structure is described by a single order parameter. The model is tested for tripropylene glycol where it accounts for the hysteresis of the dielectric beta loss peak frequency and magnitude during cooling and reheating through the glass transition.