Heat transport in dilute mixtures of3He in superfluid4He

We report new measurements of the effective thermal conductivity K_eff and relaxation time τ in dilute mixtures of³He in superfluid⁴He, with molar concentrationsX≤10⁻³. The temperature range extended fromT≈1.4 K toT _λ. Both K_cff and τ are found to agree with theoretical predictions, in contrast to previous experiments where significant differences were observed. A new thermal conductivity cell design was used which almost completely eliminates extraneous volumes and surfaces, and the earlier results are explained in relation to these design changes.     

The protease-protected 30 kDa domain of SecA is largely inaccessible to the membrane lipid phase

SecA binds to the inner membrane of Escherichia coli through low affinity lipid interactions or with high affinity at SecYEG, the integral domain of preprotein translocase. Upon addition of preprotein and nucleotide, a 30 kDa domain of SecYEG-bound SecA is protected from proteolysis via membrane insertion. Such protection could result from some combination of insertion into the lipid phase, into a proteinaceous environment or across the membrane. To assess the exposure of SecYEG-bound SecA to membrane lipids, a radiolabeled, photoactivatable and lipid-partitioning crosslinker, 3-trifluoromethyl-3-(m[125I]iodophenyl) diazirine benzoic acid ester, was incorporated into inner membrane vesicles. The 30 kDa domain of SecYEG-bound SecA, inserted into the membrane in response to translocation ligands, is 18-fold less labeled than SecY, which is labeled effectively. In contrast, incorporation of the purified 30 kDa SecA fragment into crosslinker-containing detergent micelles or addition of detergent to crosslinker-containing membranes bearing the protease-protected SecA domain readily allows for labeling of this domain. We propose that the protease-inaccessible 30 kDa SecA domain is shielded from the fatty acyl membrane phase by membrane-spanning SecYEG helices and/or is largely exposed to the periplasm.     

The on-line texture analysis of steel strips

A new on-line texture-analyzing system and its application to nondestructive r value determination is discussed. In addition to providing a brief theoretical background and describing the instrumental set-up, the article presents off-line measurements with this equipment and demonstrates the high accuracy of the determined r-values. A special feature of the unit is the possibility to simultaneously measure the most important r values—r₀, r₄₅, r₉₀, and r_m.     

Solubilization of fish muscle proteins with buffers containing sodium dodecyl sulfate

Summary The extraction of fish muscle protein using SDS containing solubilization buffers was studied varying the time and the temperature of solubilization, as well as pH and SDS concentration of the buffer. At pH < 6 the myofbrillar proteins were incompletely solubilized; temperatures of 80-100 °C resulted in protein degradation observable in the SDS-PAGE.Samples of fish muscle containing high amounts of formaldehyde (50 mmoles FA/kg wet weight) could only be solubilised at 100 °C; on the other hand it was possible to solubilize cooked and/or canned products under mild conditions (2% SDS, 1% 2-ME, pH 8.9, shaking for 2 h at 60 °C).

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Solubilisierung von Fischmuskelproteinen durch Natriumdodecylsulfathaltige Puffer

Zusammenfassung Der Einfluß von Solubilisierungszeit und -temperatur, des pH-Wertes und der SDS-Konzentration des Solubilisierungspuffers auf die Extraktion von Fischmuskelproteinen wurde überprüft. Bei pH-Werten < 6 wurden die myofbrillären Proteine nur unvollständig gelöst; Solubilisierungstemperaturen von 80 bis 100 °C führten zu einem in der SDS-PAGE sichtbaren Proteinabbau. Fischmuskelproben mit hohem Formaldehydgehalt (50 mmole FA/kg Feuchtgewicht) ließen sich nur bei 100 °C vollständig solubilisieren; demgegenüber gelang die weitgehende Solubilisierung gegarter und/oder sterilisierter Produkte unter milden Bedingungen (2% SDS, 1% 2-ME, pH 8,9; 2stündiges Schütteln bei 60 °C).

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Abbreviations FA formaldehyde - IEF isoelectric focusing - 2-ME 2-mercaptoethanol - PA polyacrylamide - PAGE polyacrylamide gel electrophoresis - pI isoelectric point - SDS sodium dodecyl sulfate - TMAO trimethylamine oxide - Tris Tris (hydroxymethyl)methylamine