Sno-capped: 5' ends of preribosomal RNAs are decorated with a U3 SnoRNP

Efficient ribosome biosynthesis is crucial for cell viability. Work recently published in Nature demonstrates that a large ribonucleoprotein processes 18S rRNA in S. cerevisiae, indicating that macromolecular particles regulate ribosome maturation and revealing the complex nature of this process.     

Microfluidic devices fabricated in poly(methyl methacrylate) using hot-embossing with integrated sampling capillary and fiber optics for fluorescence detection

High-aspect-ratio microstructures have been prepared using hot-embossing techniques in poly(methyl methacrylate) (PMMA) from Ni-based molding dies prepared using LIGA (Lithographie, Galvanoformung, Abformung). Due to the small amount of mask undercutting associated with X-ray lithography and the high energy X-ray beam used during photoresist patterning, deep structures with sharp and smooth sidewalls have been prepared. The Ni-electroforms produced devices with minimal replication errors using hot-embossing at a turn around time of approximately 5 min per device. In addition, several different polymers (with different glass transition temperatures) could be effectively molded with these Ni-electroforms and many devices (>300) molded with the same master without any noticeable degradation. The PMMA devices consisted of deep and narrow channels for insertion of a capillary for the automated electrokinetic loading of sample into the microfluidic device and also, a pair of optical fibers for shuttling laser light to the detection zone and collecting the resulting emission for fluorescence analysis. Electrophoretic separations of double-stranded DNA ladders Phi X174 digested with Hae III) were performed with fluorescence detection accomplished using near-IR excitation. It was found that the narrow width of the channels did not contribute significantly to electrophoretic zone broadening and the plate numbers generated in the extended length separation channel allowed sorting of the 271/281 base pair fragments associated with this sizing ladder when electrophoresed in methylcellulose entangled polymer solutions. The dual fiber detector produced sub-attomole detection limits with the entire detector, including laser source, electronics and photon transducer, situated in a single box measuring 3' x 10" x 14".     

Correlation of the rates of reaction of arenesulfonate ions with the trimethyloxonium ion in acetonitrile1

The kinetics of the reactions between trimethyloxonium hexafluorophosphate and a series of tetra-n-butylammonium arenesulfonates have been studied in acetonitrile at ?23.4°. With the oxonium salt concentration at about 0.01 M, two series of runs were carried out; Hammett plots of the second-order rate coefficients led to ? values of ?1.18±0.04 for 0.04 M arenesulfonate salt and ?1.07±0.02 for 0.16 M arenesulfonate salt. Solvolysis kinetics for the trimethyloxonium ion in acetonitrile are also reported.     

Differentiation of isomeric 1-, 3- and 7-deazaadenosines by electron ionization mass spectrometry

The low and high resolution electron ionization mass spectra of 1-deazaadenosine, 3-deazaadenosine and 7-deazaadenosine are reported. Fragmentation pathways and ion structures are proposed with the aid of linked-scan, daughter-ion spectra. Results indicate that the N-3 position of the purine ring serves as an important acceptor site in fragmentation processes involving hydrogen transfer from the sugar to the base. A mixture analysis of the trimethylsilyl derivatives of adenosine, 1-, 3- and 7-deazaadenosine by combined gas chromatography/mass spectrometry is also described.     

Local boundedness of minimizers of integrals of the calculus of variations

In this paper we prove the local boundedness of minimizers of integral functionals with non-standard growth conditions.     

Labelling classes by sets

Let Q be an equivalence relation whose equivalence classes, denoted Q[x], may be proper classes. A function L defined on Field(Q) is a labelling for Q if and only if for all x,L(x) is a set andL is a labelling by subsets for Q if and only ifBG denotes Bernays-Gödel class-set theory with neither the axiom of foundation, AF, nor the class axiom of choice, E. The following are relatively consistent with BG. (1) E is true but there is an equivalence relation with no labelling.(2) E is true and every equivalence relation has a labelling, but there is an equivalence relation with no labelling by subsets.This research was partially supported by Fondecyt 1980855 and by Fondecyt 1040846     

Rapid stereological quantitation of temporal neocortex in TLE

To determine the extent of neocortical atrophy in the temporal lobe using rapid stereological analysis of magnetic resonance slices in patients with temporal lobe epilepsy and to compare the findings to those obtained by visual analysis of high-resolution magnetic resonance images. 25 patients with temporal lobe epilepsy, along with 25 age-matched controls were scanned using a 1.5 Tesla magnetic resonance imaging machine (GE signa systems Paris). Visual analysis was performed on standard high-resolution images. Volumetric analysis of hippocampus and temporal neocortex was performed using computer-aided stereology (MEASURE program, Patrick Barta, Johns Hopkins, Baltimore, USA). Stereological volumetric analysis demonstrated isolated hippocampal atrophy in only nine (36%) cases including three (12%) with bilateral disease. However, eight (32%) cases had combined hippocampal and neocortical atrophy and three (12%) had isolated neocortical atrophy. All volumetric measurements took less than 10 min. On the other hand, visual analysis suggested that 17 (68%) had hippocampal atrophy alone with only two (8%) having combined neocortical atrophy and a further two (8%) having isolated neocortical atrophy. Nearly half of the patients had temporal neocortical atrophy with or without hippocampal atrophy. This rapid, accurate and non-biased quantitative technique has wide clinical utility and is significantly more valuable in detecting neocortical atrophy than visual analysis alone. The results support the notion that abnormalities may be overlooked by current standards of routine magnetic resonance imaging.     

The interstitial volume of ion-exchange columns

The relative interstitial volumes of ion-exchange columns were measured by equilibrating the columns with a standard solution, rinsing out the interstitial solution and determining the amount of solute in the rinsings. Solutions of three polyelectrolytes and of hydrochloric acid were used for this purpose. When hydrochloric acid was used, corrections were generally necessary because of the penetration of the acid into the resin. Satisfactory agreement was obtained among the various methods. Within the experimental error, the relative interstitial volume is independent of the exchangeable ion of the resin and of the mesh size. The interstitial volume decreases with decreasing crosslinkage.     

Fragment chemistry of the hydrogen thioperoxide molecule; energy, chemical potential and hardness

In this paper we present a complete theoretical study of the hydrogen thioperoxide molecule (HSOH). We characterize the internal rotation by studying the evolution of the energy, chemical potential and hardness along the torsional angle. We have found that hydrogen thioperoxide in its electronic singlet state is a gauche molecule. Barrier heights, activation chemical potential and activation hardness have been obtained, and it has been found that the trans barrier is lower than the cis one. Good agreement of rotation barriers is obtained on the basis of comparisons with the available literature experimental data for the HOOH and HSSH parent molecules. Another important result is that the maximum hardness principle is verified for the torsional motion. On the other hand, we characterize the thermochemistry of chemical reactions leading to formation of HSOH from the electronic properties associated with the free constituent fragments. The procedure, which involves the use of Sanderson's rule to estimate chemical potentials and hardnesses, is shown to be promising and opens the possibility of rationalizing the behavior of other series of reactions.