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The role of complementary hydrogen bonding as a determinant of biological specificity has been examined by protein engineering of the tyrosyl-tRNA synthetase. Deletion of a side chain between enzyme and substrate to leave an unpaired, uncharged hydrogen-bond donor or acceptor weakens binding energy by only 0.5-1.5 kcal mol-1. But the presence of an unpaired(More)
Adeno-associated virus (AAV), a non-pathogenic human parvovirus, is gaining attention for its potential use as a human gene therapy vector. One of the most attractive features of recombinant AAV vectors is the ability to be stably maintained in host cells as integrated proviruses. This property is particularly desireable for therapies requiring long-term(More)
In a previous study, a mutant of tyrosyl-tRNA synthetase in which a threonine residue (Thr51) was converted to proline dramatically improved the affinity of the enzyme for its ATP substrate. How does Pro51 improve the enzyme's affinity for ATP? A priori, Pro51 might interact directly with the ATP, or it might distort the polypeptide backbone and thereby(More)
The Double Star Project is a collaboration between Chinese and European space agencies, in which two Chinese magnetospheric research spacecraft, carrying Chi-nese and European instruments, have been launched into equatorial (on 29 December 2003) and polar (on 25 July 2004) orbits designed to enable complementary studies with the Cluster spacecraft. The two(More)
An improved method is described for the construction of mutations in M13 vectors using synthetic oligonucleotides. The DNA is first cloned into a novel M13 vector (based upon M13mp18 or M13mp19), which carries a genetic marker that can be selected against, such as an EcoK or EcoB site, or an amber mutation in an essential phage gene. In this "coupled(More)
The tyrosyl-tRNA synthetase (EC from Bacillus stearothermophilus is a dimer of two identical subunits. The dimer shows "half-of-the-sites" reactivity in that only one molecule of tyrosyladenylate is formed and one molecule of tRNATyr binds per dimer. To identify whether the tRNATyr binds to a single subunit in the dimer, or to both subunits,(More)
People often remember relatively novel environments from the first perspective encountered or the first direction of travel. This initial perspective can determine a preferred orientation that facilitates the efficiency of spatial judgements at multiple recalled locations. The present study examined this "first-perspective alignment effect" (FPA effect). In(More)
During the first quarter of 2001 the apogees of the Cluster spacecraft quartet precessed through midday local times. This provides the first opportunity for 4 spacecraft studies of the bow shock, magnetosheath and the day-side magnetopause current layer and boundary layers. In this paper, we present observations of electrons in the energy range ∼ 10 eV–26(More)