High-resolution computer simulations of stacking of weak bases using a transient pH boundary in capillary electrophoresis. 1. Concept and impact of sample ionic strength

The dynamics of focusing weak bases using a transient pH boundary was examined via high-resolution computer simulation software. Emphasis was placed on the mechanism and impact that the presence of salt, namely, NaCl, has on the ability to focus weak bases. A series of weak bases with mobilities ranging from 5 x 10(-9) to 30 x 10(-9) m2/V x s and pKa values between 3.0 and 7.5 were examined using a combination of 65.6 mM formic acid, pH 2.85, for the separation electrolyte, and 65.6 mM formic acid, pH 8.60, for the sample matrix. Simulation data show that it is possible to focus weak bases with a pKa value similar to that of the separation electrolyte, but it is restricted to weak bases having an electrophoretic mobility of 20 x 10(-9) m2/V x s or quicker. This mobility range can be extended by the addition of NaCl, with 50 mM NaCl allowing stacking of weak bases down to a mobility of 15 x 10(-9) m2/V x s and 100 mM extending the range to 10 x 10(-9) m2/V x s. The addition of NaCl does not adversely influence focusing of more mobile bases, but does prolong the existence of the transient pH boundary. This allows analytes to migrate extensively through the capillary as a single focused band around the transient pH boundary until the boundary is dissipated. This reduces the length of capillary that is available for separation and, in extreme cases, causes multiple analytes to be detected as a single highly efficient peak.

[Cosmetic results after breast conserving carcinoma treatment in patients with intramammarian seromas]

INTRODUCTION: There were 373 patients irradiated after breast conserving carcinoma treatment. A planning computed tomography revealed in 97 of these patients seromas and tissue defects exceeding 2cm in diameter. The cosmetic results in those patients and the impact of seromas herein had to be evaluated. PATIENTS AND METHODS: Mean age was 59 years. A quadrant resection was performed in 17.5 percent of the patients, a segmental resection in 27.8 percent and a tumour excision in 54.6 percent. Radiation therapy was applied with the Linear accelerator and 6 MeV photons up to a total dose in the residual breast of 50 Gy followed by a boost dose to the former tumour bed of 10 Gy. A distinct evaluation and documentation of therapy related side effects and the resulting cosmesis was done in 51 patients. RESULTS: In all the examined seroma patients there were moderate acute skin reactions grade 1 to 3. As late effects in 82.3 percent scar indurations were noticed. At the skin 51 percent showed enhanced pigmentation, 68.6 percent atrophia and only 11 percent teleangiectasia. Subcutaneous fibrosis occurred in 56,9 percent of the patients, 78.4 percent of the women had breast asymmetries. In 41.2 percent there were a lymphedema subcutaneously, in 72.5 percent impaired sensibility. The overall cosmetic result documented with a 5 point score was "very good" (score 1) in 19.6 percent and "good" (score 2) in 33.3 percent, 37.3 percent were "satisfactory" (score 3) and 9.8 percent "bad" (score 4) respectively. No "very bad" results (score 5) were seen. CONCLUSIONS: The cosmetic results in the examined group of seroma and hematoma patients were inferior to those reported in the literature. We conclude that postoperative seroma and hematoma have an adverse effect on the resulting cosmesis and that their frequency and extent have to be reduced in future by the responsible surgeons.

Exploring "fringe" consciousness: the subjective experience of perceptual fluency and its objective bases

Perceptual fluency is the subjective experience of ease with which an incoming stimulus is processed. Although perceptual fluency is assessed by speed of processing, it remains unclear how objective speed is related to subjective experiences of fluency. We present evidence that speed at different stages of the perceptual process contributes to perceptual fluency. In an experiment, figure-ground contrast influenced detection of briefly presented words, but not their identification at longer exposure durations. Conversely, font in which the word was written influenced identification, but not detection. Both contrast and font influenced subjective fluency. These findings suggest that speed of processing at different stages condensed into a unified subjective experience of perceptual fluency.

Structural bases for the interaction and stabilization of the human amino acid transporter LAT2 with its ancillary protein 4F2hc.

Heteromeric amino acid transporters (HATs) are the unique example, known in all kingdoms of life, of solute transporters composed of two subunits linked by a conserved disulfide bridge. In metazoans, the heavy subunit is responsible for the trafficking of the heterodimer to the plasma membrane, and the light subunit is the transporter. HATs are involved in human pathologies such as amino acidurias, tumor growth and invasion, viral infection and cocaine addiction. However structural information about interactions between the heavy and light subunits of HATs is scarce. In this work, transmission electron microscopy and single-particle analysis of purified human 4F2hc/L-type amino acid transporter 2 (LAT2) heterodimers overexpressed in the yeast Pichia pastoris, together with docking analysis and crosslinking experiments, reveal that the extracellular domain of 4F2hc interacts with LAT2, almost completely covering the extracellular face of the transporter. 4F2hc increases the stability of the light subunit LAT2 in detergent-solubilized Pichia membranes, allowing functional reconstitution of the heterodimer into proteoliposomes. Moreover, the extracellular domain of 4F2hc suffices to stabilize solubilized LAT2. The interaction of 4F2hc with LAT2 gives insights into the structural bases for light subunit recognition and the stabilizing role of the ancillary protein in HATs.

Synthesis of Carbocyclic C-Nucleosides Containing Nonnatural Pyrimidine Bases

A series of new carbocyclic C-nucleosides with a cis-4′-(hydroxymethyl)cyclopent-2′-enyl sugar moiety and unnatural pyrimidine bases (2–6) were synthesized in racemic form in two steps starting from the easily accessible cyclic carbonate 1.

Nucleic-Acid Analogs with Restricted Conformational Flexibility in the Sugar-Phosphate Backbone (‘Bicyclo-DNA’). Part 5. Synthesis, Characterization, and Pairing Properties of Oligo-αlpha-D-(bicyclodeoxynucleotides) of the Bases Adenine and Thymine (αlpha-Bicyclo-DNA)

10.1002/hlca.19950780816.abs A conformational analysis of the (3′S,5′R)-2′-deoxy-3′,5′-ethano-α-D-ribonucleosides (a-D-bicyclodeoxynucleosides) based on the X-ray analysis of N4-benzoyl-α-D-(bicyclodeoxycytidine) 6 and on 1H-NMR analysis of the α-D-bicyclodeoxynucleoside derivatives 1-7 reveals a rigid sugar structure with the furanose units in the l′-exo/2′-endo conformation and the secondary OH groups on the carbocyclic ring in the pseudoequatorial orientation. Oligonucleotides consisting of α-D-bicyclothymidine and α-D-bicyclodeoxyadenosine were successfully synthesized from the corresponding nucleosides by phosphoramidite methodology on a DNA synthesizer. An evaluation of their pairing properties with complementary natural RNA and DNA by means of UV/melting curves and CD spectroscopy show the following characteristics: i) α-bcd(A10) and α-bcd(T10) (α = short form of α-D)efficiently form complexes with complementary natural DNA and RNA. The stability of these hybrids is comparable or slightly lower as those with natural β-d(A10) or β-d(T10)( β = short form ofβ-D). ii) The strand orientation in α-bicyclo-DNA/β-DNA duplexes is parallel as was deduced from UV/melting curves of decamers with nonsymmetric base sequences. iii) CD Spectroscopy shows significant structural differences between α-bicyclo-DNA/β-DNA duplexes compared to α-DNA/β-DNA duplexes. Furthermore, α-bicyclo-DNA is ca. 100-fold more resistant to the enzyme snake-venom phosphodiesterase with respect to β-DNA and about equally resistant as α-DNA.