Differences and similarities in DNA-binding preferences of MyoD and E2A protein complexes revealed by binding site selection

A technique was developed for studying protein-DNA recognition that can be applied to any purified protein, partially purified protein, or cloned gene. From oligonucleotides in which particular positions are of random sequence, that subset to which a given protein binds is amplified by the polymerase chain reaction and sequenced as a pool. These selected and amplified binding site (SAAB) "imprints" provide a characteristic set of preferred sequences for protein binding. With this technique, it was shown that homo- and heterooligomers of the helix-loop-helix proteins MyoD and E2A recognize a common consensus sequence, CA--TG, but otherwise bind to flanking and internal positions with different sequence preferences that suggest half-site recognition. These findings suggest that different combinations of dimeric proteins can have different binding sequence preferences.     

Interstellar scintillations of pulsar radiation

Time fluctuations in the intensity of pulsed radiation from CP 0834, CP 1133, AP 1237, and CP 1919 have been investigated. Power spectra, modulation indices, frequency distributions, and decorrelation frequencies are consistent with scintillation theory. If it is assumed that these scintillations are due to irregularities in the interstellar medium that travel at a velocity of 20 kilometers per second, the irregularities have a scale size on the order of 10(4) kilometers and a distance from the earth of approximately 70 parsecs. These interstellar scintillations would not have been observed if the apparent angular diameters of the pulsars were larger than 0.3 X 10(-5) second of arc, and they would cause even a point radio source to have an apparent angular diameter of approximately 10(-3) second of arc at 318 megahertz.     

Microbial control of silicate weathering in organic-rich ground water

An in situ microcosm study of the influence of surface-adhering bacteria on silicate diagenesis in a shallow petroleum-contaminated aquifer showed that minerals were colonized by indigenous bacteria and chemically weathered at a rate faster than theoretically predicted. Feldspar and quartz fragments were placed in anoxic, organic-rich ground water, left for 14 months, recovered, and compared to unreacted controls with scanning electron microscopy. Ground-water geochemistry was characterized before and after the experiment. Localized mineral etching probably occurred in a reaction zone at the bacteria-mineral interface where high concentrations of organic acids, formed by bacteria during metabolism of hydrocarbon, selectively mobilized silica and aluminum from the mineral surface.     

Spot-scan imaging in transmission electron microscopy.

The determination of the structure of proteins and other organic materials by transmission electron microscopy is a rapidly developing field. Obtaining high-resolution images of these radiation-sensitive specimens has, until recently, been problematic. The development of spot-scan imaging, in which the electron beam is focused to a spot with a diameter of about 1000 angstroms and moved over the specimen to record the image, has overcome some of the most severe problems, which result from beam-induced motion of the specimen and its image. Elimination of this motion greatly enhances the contrast of high-resolution features of the image and promises a significant increase in the speed with which future structural work can be accomplished.     

The relation between method of propagation,plant density and growth,mineral uptake and yield of dasheen (Colocasia antiquorum, Schott.)

Two field experiments were carried out to investigate the effect of method of propagation (including two proposed new methods) and plant density on the growth, mineral uptake and yield of dasheen (Colocasia antiquorum, Schott.).Planting different pieces of “seed” resulted in a higher percentage germination, higher percentage efficiency of solar energy conversion and better growth characters of the plant, in the order: cormel, apical, half-apical, corm piece and quarter-apical piece, respectively.Increasing the plant density decreased the growth characters of the plant and increased the percentage efficiency of solar energy conversion.The nitrogen, phosphorus and potassium concentrations were not affected by types of dasheen seeds, whereas the absolute amount per plant followed the same pattern of change as the dry matter content.Distance between plants had no statistically significant effect on the concentrations of nitrogen, phosphorus and potassium in the plant tissues. However, the absolute amounts of these minerals per plant decreased as the plant population was increased.Planting with the cormel resulted in the highest total yield. However, the difference in total yield between planting with the apical and half-apical pieces was not statistically significant. A similar situation was found when planting with quarter-apical and corm pieces. Therefore, it is recommended that the apical piece is cut into two equal halves in order to use a given amount of apicals to reduce the corm pieces when planting.Increasing the plant population, by reducing the distance between plants from 45 to 30 cm, resulted in an increased yield per hectare. However, reducing the distance between plants to 15 cm resulted in a decrease in yield.     

Increase of resistance of <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> plants to phytopathogenic fungi expressing hevein-like peptides from weed plant <Emphasis Type="Italic">Stellaria media</Emphasis>

It is shown that constitutive hyperexpression of new hevein-like peptides from the weed plant chickweed (Stellaria media)in mouse-ear cress (Arabidopsis thaliana) plants leads to a substantial increase of their resistance to phytopathogenic fungi Botrytis cinerea and Bipolaris sorokiniana. Thus, common chickweed peptides can play a definite role in protecting this weed plant and be useful as a new genetic tool for producing plants resistant to fungal diseases.     

Structure of the quaternary complex of interleukin-2 with its alpha, beta, and gammac receptors

Interleukin-2 (IL-2) is an immunoregulatory cytokine that acts through a quaternary receptor signaling complex containing alpha (IL-2Ralpha), beta (IL-2Rbeta), and common gamma chain (gc) receptors. In the structure of the quaternary ectodomain complex as visualized at a resolution of 2.3 angstroms, the binding of IL-2Ralpha to IL-2 stabilizes a secondary binding site for presentation to IL-2Rbeta. gammac is then recruited to the composite surface formed by the IL-2/IL-2Rbeta complex. Consistent with its role as a shared receptor for IL-4, IL-7, IL-9, IL-15, and IL-21, gammac forms degenerate contacts with IL-2. The structure of gammac provides a rationale for loss-of-function mutations found in patients with X-linked severe combined immunodeficiency diseases (X-SCID). This complex structure provides a framework for other gammac-dependent cytokine-receptor interactions and for the engineering of improved IL-2 therapeutics.