Two structural domains of initiation factor eIF-4B are involved in binding to RNA

Translation initiation factor eIF-4B promotes the binding of mRNA to 40 S preinitiation complexes and together with eIF-4A possesses RNA helicase activity. To elucidate structural features involved in its function, a series of internal and C-terminal deletions, as well as point mutations, were constructed in the eIF-4B cDNA. The mutated cDNAs were expressed in transiently transfected COS-1 cells, and mutant forms of the factor were overproduced up to about 25-fold over endogenous eIF-4B levels. Inhibition of dihydrofolate reductase (DHFR) synthesis by high levels of eIF-4B variants was determined in vivo, and the binding of the eIF-4B forms to biotinylated RNA was measured in vitro. The results indicate that the N-terminal region containing the RNA binding motif with its RNP1 and RNP2 consensus elements is sufficient for inhibition of DHFR synthesis. Deletion of the RNP1 sequence abrogates RNA binding, but amino acid substitutions at conserved residues do not always inhibit RNA binding. Deletion of the DRYG domain near the middle of eIF-4B results in inhibition of RNA binding, but not of DHFR synthesis. Up to 164 residues of the C terminus are not required for RNA binding, but removal of 226 or more residues completely inhibits RNA binding, perhaps by the loss of two arginine-rich regions. The results suggest that both the RNA recognition motif and the arginine-rich region are required for stable RNA binding but that both are not necessary for in vivo inhibition of protein synthesis.     

Parallelisation of suboptimal spectrum search

The authors suggest that effective algorithms for spectrum search, such as those used for detecting spread spectrum signals, may be derived by selecting suboptimal algorithms and then recovering some of the lost efficacy through parallelisation methods. This thesis is motivated by considering a simple yet meaningful example of a spectrum search technique that exhibits what at first may seem to be counterintuitive behaviour.<>     

Error rate for optimal follower tone-jamming

The performance of a countermeasure technique in the presence of the optimal follower multitone jammer is evaluated for frequency-hopped spread spectrum (FHSS) communications. It is shown that, with a certain probability, the optimal jammer will have dual tones in a frequency channel     

Comparison of three rewarming methods in a postanesthesia care unit

Postoperative hypothermia is problematic because patients in postanesthesia care units (PACUs) often feel very cold, and unrecognized or prolonged postoperative hypothermia can aggravate patients' underlying cardiovascular disorders. The researchers compared three methods of rewarming PACU patients who had undergone laparotomy procedures. Patients were assigned randomly to three groups. Each patient in group one received the standard PACU rewarming intervention (ie, two warmed thermal blankets and a hospital bedspread). Each patient in group two received the standard PACU rewarming intervention plus a reflective blanket. Each patient in group three received the standard PACU rewarming intervention plus a reflective blanket and a reflective head covering. Nurses measured patients' vital signs on admission to the PACU and every 15 minutes thereafter until patients' sublingual temperatures reached 36 degrees C (96.8 degrees F). No significant temperature differences occurred among patients in the three groups, but an inverse relationship existed between patients' PACU admission temperatures and the time they required to reach normothermia.     

Numerical study of steady turbulent flow through bifurcated nozzles in continuous casting

Bifurcated nozzles are used in continuous casting of molten steel, where they influence the quality of the cast steel slabs. The present study performs two-dimensional (2-D) and three-dimensional (3-D) simulations of steady turbulent(K- ε) flow in bifurcated nozzles, using a finite-element (FIDAP) model, which has been verified previously with water model experiments. The effects of nozzle design and casting process operating variables on the jet characteristics exiting the nozzle are investigated. The nozzle design parameters studied include the shape, angle, height, width, and thickness of the ports and the bottom geometry. The process operating practices include inlet velocity profile and angle as well as port curvature caused by erosion or inclusion buildup. Results show that the jet angle is controlled mainly by the port angle but is steeper with larger port area and thinner walls. The degree of swirl is increased by larger or rounder ports. The effective port area, where there is no recirculation, is increased by smaller or curved ports. Flow asymmetry is more severe with skewed or angled inlet conditions or unequal port sizes. Turbulence levels in the jet are higher with higher casting speed and smaller ports. Formerly Research Assistant, Department of Mechanical and Industrial Engineering. Formerly Research Assistant in the same department.     

Synthesis and triplex forming properties of an acyclic N7-glycosylated guanine nucleoside

A chiral acyclic nucleoside, one in which the ribose carbohydrate has been replaced with a glycerol-based linker, is prepared by glycosylating guanine at the N7-nitrogen. The stereochemically pure derivative is converted to a DMT-protected phosphoramidite for incorporation into DNA sequences. Sequence containing the acyclic N7-dG nucleoside are capable of forming DNA triplexes in which it is likely that the N1-H and N2-amino groups of the N7-dG are involved in recognition of the guanine base in G-C base pairs.     

Evaluation of chromic oxide,glycerol triether,and β-sitosterol as fecal flow markers in two species of nonhuman primates

Recovery of β-sitosterol, glycerol triether (1-hexadecyl-2,3,-didodecyl glycerol triether), and chromic oxide was studied in African green monkeys and stumptail macaques consuming diets containing 0.75 mg/Cal cholesterol and 38% of calories as safflower oil or butter. Following oral administration of these compounds, feces were collected daily for 9 days. For all animals, excretion of β-sitosterol and glycerol triether paralleled one another almost exactly. Except for two animlas, this was also true for chromic acid. Essentially 100% of the administered β-sitosterol and 90–95% of the glycerol triether were recovered; excretion of these markers virtually was complete by day 3. Ninety-two percent of the β-sitosterol was isolated in the nonsaponifiable lipid extract of the feces with less than 6% in the remaining aqueous phase. A maximum of 3.1% of the β-sitosterol and 1.8% of the glycerol triether were found in the blood. For stumptail macaques, the major excretory form of β-sitosterol was the 5β-derivative. African green monkeys were more variable; one animal excreted the bulk of the β-sitosterol unchanged while others excreted greater than 80% as the ring-saturated 5β-derivative. Animals consuming the safflower oil containing diet consistently excreted a greater percentage of the β-sitosterol unchanged, compared with those animals eating the butter containing diet. There was no evidence for steroid ring degradation in any of the animals used in this study.     

The effect of molecular structure on the gas transmission rates of aromatic polyimides

A series of high-molecular weight condensation polyimides was evaluated to determine the effect of polymer molecular structure on the transmission rate of oxygen, carbon dioxide, and water vapor. The polyimide films were prepared from either 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA) or pyromellitic dianhydride (PMDA) with various diamines. The study shows that molecular structure had a strong influence on gas transmission rates with results for some films varying three orders of magnitude from that of other polyimide films. In general, the BTDA series of polyimides had overall lower gas transmission rates than the PMDA-derived series. Polymers prepared with meta-oriented diamines characteristically displayed lower gas transmission than those prepared with para-oriented diamines.     

Color‐Coded Super‐Resolution Small‐Molecule Imaging

Although the development of super‐resolution microscopy dates back to 1994, its applications have been primarily focused on visualizing cellular structures and targets, including proteins, DNA and sugars. We now report on a system that allows both monitoring of the localization of exogenous small molecules in live cells at low resolution and subsequent super‐resolution imaging by using stochastic optical reconstruction microscopy (STORM) on fixed cells. This represents a powerful new tool to understand the dynamics of subcellular trafficking associated with the mode and mechanism of action of exogenous small molecules.     

Flexibilized Copolyimide Adhesives

Two copolyimides, LARC-STPI and STPI-LARC-2, with flexible backbones were prepared and characterized as adhesives. The processability and adhesive properties were compared to those of a commercially available form of LARC-TPI.

Lap shear specimens were fabricated using adhesive tape prepared from each of the three polymers. Lap shear tests were performed at room temperature, 177°C, and 204°C before and after exposure to water-boil and to thermal aging at 204°C for up to 1000 hours.

The three adhesive systems possess exceptional lap shear strengths at room temperature and elevated temperatures both before and after thermal exposure. LARC-STPI, because of its high glass transition temperature provided high lap shear strengths up to 260°C. After water-boil, LARC-TPI exhibited the highest lap shear strengths at room temperature and 177°C, whereas the LARC-STPI retained a higher percentage of its original strength when tested at 204°C [68% versus 50% (STPI-LARC-2) and 40% (LARC-TPI)].

These flexible thermoplastic copolyimides show considerable potential as adhesives based on this study and because of the ease of preparation with low cost, commercially available materials.