Imperfect DNA mirror repeats in the gag gene of HIV-1 (HXB2) identify key functional domains and coincide with protein structural elements in each of the mature proteins

<p>Abstract</p> <p>Background</p> <p>A DNA mirror repeat is a sequence segment delimited on the basis of its containing a center of symmetry on a single strand, e.g. 5'-GCATGGTACG-3'. It is most frequently described in association with a functionally significant site in a genomic sequence, and its occurrence is regarded as noteworthy, if not unusual. However, imperfect mirror repeats (IMRs) having ≥ 50% symmetry are common in the protein coding DNA of monomeric proteins and their distribution has been found to coincide with protein structural elements – helices, β sheets and turns. In this study, the distribution of IMRs is evaluated in a polyprotein – to determine whether IMRs may be related to the position or order of protein cleavage or other hierarchal aspects of protein function. The gag gene of HIV-1 [GenBank:<ext-link ext-link-type="gen" ext-link-id="K03455">K03455</ext-link>] was selected for the study because its protein motifs and structural components are well documented.</p> <p>Results</p> <p>There is a highly specific relationship between IMRs and structural and functional aspects of the Gag polyprotein. The five longest IMRs in the polyprotein translate a key functional segment in each of the five cleavage products. Throughout the protein, IMRs coincide with functionally significant segments of the protein. A detailed annotation of the protein, which combines structural, functional and IMR data illustrates these associations. There is a significant statistical correlation between the ends of IMRs and the ends of PSEs in each of the mature proteins. Weakly symmetric IMRs (≥ 33%) are related to cleavage positions and processes.</p> <p>Conclusion</p> <p>The frequency and distribution of IMRs in HIV-1 Gag indicates that DNA symmetry is a fundamental property of protein coding DNA and that different levels of symmetry are associated with different functional aspects of the gene and its protein. The interaction between IMRs and protein structure and function is precise and interwoven over the entire length of the polyprotein. The distribution of IMRs and their relationship to structural and functional motifs in the protein that they translate, suggest that DNA-driven processes, including the selection of mirror repeats, may be a constraining factor in molecular evolution.</p

A study of failure in senior high school

Not available.Dorothy R. LangNot ListedNot ListedMaster of ScienceDepartment Not ListedCunningham Memorial Library, Terre Haute, Indiana State University.isua-thesis-1952-lang.pdfMastersTitle from document title page. Document formatted into pages: contains 61p. : ill. Includes bibliography

ORIGIN OF THE MOUNT MERINO CHERT AND SHALE, MIDDLE ORDOVICIAN, EASTERN NEW YORK STATE

Mount Merino Chert and Shale, Middle Ordovician, is one of the most siliceous units of the Taconic sequence (eastern New York and western Vermont); it is composed of interbedded shale, siliceous hale, argillite and chert. Non-clastic quartz — aggregates of quartz having a.mosaic or felted texture — predominates in all beds, except `shale. All siliceous beds are finely laminated; most laminae are distinguished from adjacent laminae by the texture of the quartz groundmass, and the amount of clastics, carbonates, chlorite and sulphides. Statistical comparison of the textures of the quartz aggregates which occur with the other mineral components suggests that the components of each lamina represent a stable mineralogic assemblage; the assemblages probably formed during silica precipitation and early diagenesis. These assemblages are compositionally-consistent with experimental data regarding the formation of authigenic minerals in the presence of colloidal silica. Mount Merino rocks comprise a minor.part of the Giddings Brook slice of the Taconic allochthon; the Mount Merino fauna is the youngest of the Giddings Brook slice rock sequence. Mount Merino rocks also occur as boulders and blocks in Forbes Hill Conglomerate, an autochthonous wildflysch-like terrain underlying the Giddings Brook slice. Petrographic aspects of Mount Merino rocks indicate a starved depositional environment distant from an extensive land area. The predominant source of silica for the rocks was probably vulcanism (the Ammonoosuc volcanics) which became relatively intense during Mount Merino time, just preceding emplacement of the Taconic allochthon

Scalable Multiprocessor for High-Speed Computing in Space

A report discusses the continuing development of a scalable multiprocessor computing system for hard real-time applications aboard a spacecraft. "Hard realtime applications" signifies applications, like real-time radar signal processing, in which the data to be processed are generated at "hundreds" of pulses per second, each pulse "requiring" millions of arithmetic operations. In these applications, the digital processors must be tightly integrated with analog instrumentation (e.g., radar equipment), and data input/output must be synchronized with analog instrumentation, controlled to within fractions of a microsecond. The scalable multiprocessor is a cluster of identical commercial-off-the-shelf generic DSP (digital-signal-processing) computers plus generic interface circuits, including analog-to-digital converters, all controlled by software. The processors are computers interconnected by high-speed serial links. Performance can be increased by adding hardware modules and correspondingly modifying the software. Work is distributed among the processors in a parallel or pipeline fashion by means of a flexible master/slave control and timing scheme. Each processor operates under its own local clock; synchronization is achieved by broadcasting master time signals to all the processors, which compute offsets between the master clock and their local clocks

Facilitate Insight by Non-Invasive Brain Stimulation

Our experiences can blind us. Once we have learned to solve problems by one method, we often have difficulties in generating solutions involving a different kind of insight. Yet there is evidence that people with brain lesions are sometimes more resistant to this so-called mental set effect. This inspired us to investigate whether the mental set effect can be reduced by non-invasive brain stimulation. 60 healthy right-handed participants were asked to take an insight problem solving task while receiving transcranial direct current stimulation (tDCS) to the anterior temporal lobes (ATL). Only 20% of participants solved an insight problem with sham stimulation (control), whereas 3 times as many participants did so (p = 0.011) with cathodal stimulation (decreased excitability) of the left ATL together with anodal stimulation (increased excitability) of the right ATL. We found hemispheric differences in that a stimulation montage involving the opposite polarities did not facilitate performance. Our findings are consistent with the theory that inhibition to the left ATL can lead to a cognitive style that is less influenced by mental templates and that the right ATL may be associated with insight or novel meaning. Further studies including neurophysiological imaging are needed to elucidate the specific mechanisms leading to the enhancement