(+)-Epi-biotin differs from (+)-biotin in the configuration of the chiral center at atom C2. This could lead to a difference in the mode of binding of (+)-epi-biotin to streptavidin, a natural protein receptor for (+)-biotin. Diffraction data were collected to a maximum of 0.85 Angstrom resolution for structural analysis of the complex of streptavidin with a sample of (+)-epi-biotin and refinem...

As the originator of the oxygen in our atmosphere, the photosynthetic water-splitting enzyme of chloroplasts is vital for aerobic life on the earth. It has a manganese cluster at its active site, but it is poorly understood at the molecular level. Polarized synchrotron radiation was used to examine the x-ray absorption of manganese in oriented chloroplasts. The manganese site, in the "resting" ...

The optimum imaging of an object structure at the sub-angstrom length scale requires precise adjustment of the lens aberrations of a high-resolution instrument up to the fifth order. A least-squares optimization of defocus aberration C1, third-order spherical aberration C3, and fifth-order spherical aberration C5 yields two sets of aberration coefficients for strong phase contrast up to the inf...

The main goal of this paper is to review the theoretical models which can be used to describe the interactions between silica surfaces and to show that a model proposed earlier by the authors (the polarization model), which accounts concomitantly for double layer and hydration forces, can be adapted to explain recent experiments in this direction. When the water molecules near the interface wer...

Number of mathematical correlations have been used to predict the monthly average global solar radiation on horizontal using the sun hours as an input parameter. The study was carried out on two weather stations in the UAE, which are Abu Dhabi and Al Ain, using a daily weather data recorded for 13 years. The used correlations included the linear Angstrom-Prescott model and its derivations, name...

Structures of a 10-subunit yeast RNA polymerase II have been derived from two crystal forms at 2.8 and 3.1 angstrom resolution. Comparison of the structures reveals a division of the polymerase into four mobile modules, including a clamp, shown previously to swing over the active center. In the 2.8 angstrom structure, the clamp is in an open state, allowing entry of straight promoter DNA for th...

We reported previously that unsaturated linear-chain fatty acids of the cis-configuration with a C18-hydrocarbon chain such as linoleic acid (cis-9, 12-octadecadienoic acid, C18:2) could potently inhibit the activity of mammalian DNA polymerases (Biochim Biophys Acta 1308: 256-262, 1996). In this study, we investigated the inhibitory effects of cis-type C22-fatty acids including cis-7,10,13,16,...

a new polymorph crystalline silica composition having uniform pore dimensions were synthesized by calcining a crystalline hydrated alkyl-ammonium silicate. the pore dimensions approximately were 6 angstrom for silicalite-1 and 11 angstrom for silicalite-2 units. the silicalite-1 was prepared hydrothermally at a ph of about 10 from a reaction mixture consist of water, amorphous silica and a quat...

The introduction of disulfide bonds into proteins creates additional mechanical barriers and limits the unfolded contour length (i.e., the maximal extension) measured by single-molecule force spectroscopy. Here, we engineer single disulfide bonds into four different locations of the human cardiac titin module (I27) to control the contour length while keeping the distance to the transition state...

Aerosol optical depth measurements over Bahrain acquired through the ground-based Aerosol Robotic Network are analyzed. Optical depths obtained from ground-based sun/sky radiometers showed a pronounced temporal trend, with a maximum dust aerosol loading observed during the March to July period. The aerosol optical depth probability distribution is rather narrow with a modal value of about 0.25....