Hydrophobic interactions: an overview

We present an overview of the recent progress that has been made in understanding the origin of hydrophobic interactions. We discuss the different character of the solvation behavior of apolar solutes at small and large length scales. We emphasize that the crossover in the solvation behavior arises from a collective effect, which means that implicit solvent models should be used with care. We then discuss a recently developed explicit solvent model, in which the solvent is not described at the atomic level, but rather at the level of a density field. The model is based upon a lattice-gas model, which describes density fluctuations in the solvent at large length scales, and a Gaussian model, which describes density fluctuations at smaller length scales. By integrating out the small length scale field, a Hamiltonian is obtained, which is a function of the binary, large-length scale field only. This makes it possible to simulate much larger systems than hitherto possible as demonstrated by the application of the model to the collapse of an ideal hydrophobic polymer. The results show that the collapse is dominated by the dynamics of the solvent, in particular the formation of a vapor bubble of critical size. Implications of these findings to the understanding of pressure denaturation of proteins are discussed.Comment: 10 pages, 4 figure

Performance evaluation test results - Spacecraft cabin moisture-removal system 630275-1

Regenerative moisture removal system testing for spacecraft cabin gases under 14 day mission simulatio

A Novel Bioluminescent Protease Assay Using Engineered Firefly Luciferase

Proteases play important roles in a variety of disease processes. Understanding their biological functions underpins the efforts of drug discovery. We have developed a bioluminescent protease assay using a circularly permuted form of firefly luciferase, wherein the native enzyme termini were joined by a peptide containing a protease site of interest. Protease cleavage of these mutant luciferases greatly activates the enzyme, typically over 100 fold. The mutant luciferase substrates are easily generated by molecular cloning and cell-free translation reactions and thus the protease substrates do not need to be chemically synthesized or purchased. The assay has broad applicability using a variety of proteases and their cognate sites and can sensitively detect protease activity. In this report we further demonstrate its utility for the evaluation of protease recognition sequence specificity and subsequent establishment of an optimized assay for the identification and characterization of protease inhibitors using high throughput screening

Research of the open-type wind tunnel parameters by using numerical methods

The work covers research of open-type wind tunnel parameters using numerical methods. Computer modeling software Solidworks and its add-on Cosmos FloWorks is used in this study. Research is made about how different configurations of contraction influence air stream quality in the test chamber. Also qualitative assessment is made about analyzed contraction configurations

Kai kurie vakarų baltų kalbos reiškiniai pietinėse lietuvių tarmėse

MANCHE ERSCHEINUNGEN DES WESTBALTISCHEN IN DEN MUNDARTEN DES SÜDLITAUISCHENZusammenfassungDie in südlichen Hochlitauischen Mundarten erhaltengebliebene Erscheinungen des Westbaltischen bemüht man sich als ob von der Seite, von der Mundart Zietela (Belorußland, Bezirk Grodno, Kreis Dziatlava, russ. Diatlovo, pol. Zdięcioł, lit. Zietela) anzusehen. Zietela ist jetzt am meisten ent­fernt von den litauischen Hauptmundarten und stimmt mit keiner gegenwärtigen litauischen Mundart überein. Im Artikel wird die Verbreitung der kennzeichnenden und archaischen Züge Zietelas auf dem Gebiet der Phonetik (des Vokalismus und Konsonantismus), Morphologie und Lexik in benachbarten Südlichen Untermundarten des Süd- und Westhochlitauischen überblickt.Aus den ungleich breit erhaltengebliebenen Elementen des Westbaltischen in west- und südhochlitauischen Untermundarten, auch um Zietela sieht man, daß alle diese Mundarten ehemals zum unun­terbrochenen Areal des Westbaltischen gehörten. Nur im Laufe der Zeit, nach dem Zusammenstoß mit den Litauern, haben die einzelnen Bezirke dieses Areals die verschiedenen Grade der Integration erlitten.Unter größten Einfluß der Litauer (Osthochlitauer) standen die nächsten Nachbarn die Südhochli­tauer, deren Boden jetzt mit größeren oder kleineren Flecken der östlichen Mundarten gedeckt ist. Ein Teil von Östlichkeiten erreichte auch Zietela. Der westliche Teil Litauens, so vie das Kleinlitauen, haben mehr oder weniger den Westsubstrat aufbewahrt. Zietelas Mundart bewahrte bis zur Gegenwart etwa am meisten den Westbalten übliche lautliche und andere Elemente der Sprachstruktur auf, obwohl sie durch die östliche Züge gefärbt ist und sich durch viele Slawismen auszeichnet.</p

Determination of the Volume Changes for Pressure-Induced Transitions of Apomyoglobin between the Native, Molten Globule, and Unfolded States

AbstractThe volume change for the transition from the native state of horse heart apomyoglobin to a pressure-induced intermediate with fluorescence properties similar to those of the well-established molten globule or I form was measured to be −70ml/mol. Complete unfolding of the protein by pressure at pH 4.2 revealed an upper limit for the unfolding of the intermediate of −61ml/mol. At 0.3M guanidine hydrochloride, the entire transition from native to molten globule to unfolded state was observed in the available pressure range below 2.5kbar. The volume change for the N→I transition is relatively large and does not correlate well with the changes in relative hydration for these transitions derived from measurements of the changes in heat capacity, consistent with the previously observed lack of correlation between the m-value for denaturant-induced transitions and the measured volume change of unfolding for cooperativity mutants of staphylococcal nuclease (Frye et al. 1996. Biochemistry. 35:10234–10239). Our results support the hypothesis that the volume change associated with the hydration of protein surface upon unfolding may involve both positive and negative underlying contributions that effectively cancel, and that the measured volume changes for protein structural transitions arise from another source, perhaps the elimination of void volume due to packing defects in the structured chains