Tracing Lysozyme-Lipid Interactions with Long-Wavelength Squaraine Dyes

The applicability of the two newly commercial available squaraine labels Square-670-NHS and Seta-635-NHS to exploring protein-lipid interactions has been evaluated. The labels were conjugated to lysozyme (Lz) (squaraine-lysozyme conjugates below referred to as Square-670-Lz and Seta-635-Lz), a structurally well-characterized small globular protein displaying the ability to interact both, electrostatically and hydrophobically with lipids. The lipid component of the model systems was represented by lipid vesicles composed of zwitterionic lipids egg yolk phosphatidylcholine (PC) and 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine (SOPC), and their mixtures with anionic lipids either beef heart cardiolipin (CL) or 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol (POPG), respectively. Fluorescence intensity of Square-670-Lz was found to decrease upon association with lipid bilayer, while the fluorescence intensity of Seta-635-Lz displayed more complex behavior depending on lipid-to-protein molar ratio. Covalent coupling of squaraine labels to lysozyme exerts different influence on the properties of dye-protein conjugate. It was suggested that Square-670-NHS covalent attachment to Lz molecule enhances protein propensity for self-association, while squaraine label Seta-635-NHS is sensitive to different modes of lysozyme-lipid interactions—within the L:P range 6–11, when hydrophobic protein-lipid interactions are predominant, an aggregation of membrane-bound protein molecules takes place, thereby decreasing the fluorescence intensity of Seta-635-Lz. At higher L:P values (from 22 to 148) when electrostatic interactions are enhanced fluorescence intensity of Seta-635-Lz increases with increasing lipid concentrations.     

Chromatographic Characteristics of Adamantyl Silicone Stationary Phase

Chromatographic characteristics of adamantyl silicone stationary phase were studied.     

Investigation of selectively substituted monosaccharides by the method of vibrational spectroscopy and X-ray analysis

The influence of steric factors on the formation of vibrational spectra of carbohydrates was illustrated by the example of selectively substituted monosaccharides. We consider compounds in which the difference and similarity of vibrational spectra are largely determined by the difference and similarity of the geometry of their molecular base (the molecule's skeleton). At the same time, in the case of selectively substituted nitrates of methyl-β- -glucopyranoside, the skeletal bases of which are identical, with differences in the localization site of volumetric substituents and their total number, or in rotational isomers (conformations) of the lateral nitrate groups, their Fourier Raman spectra are different over a wide spectral range. It is concluded that steric factors and the position of volumetric substituents of hydroxyls produce an exceptionally important effect on the formation of vibrational spectra of carbohydrates.     

Sigmatropic rearrangements of alkenyl benzofuryl and benzothienyl sulfides

The thio Claisen rearrangement of 2-butenyl 2-benzofuryl sulfide, cyclopenten-2-yl 2-benzofuryl sulfide, 2-butenyl 2-benzothienyl sulfide, and cyclopenten-2-yl 2-benzothienyl sulfide was investigated. The rates, energies and entropies of activation of the process were calculated, and the effect of the structure of the sulfide, the polarity of the solvent, and the temperature was demonstrated by comparison of these values. The 1,3-thioallyl rearrangement of 1-methylallyl 3-methyl-2-benzothienyl sulfide was studied, and it was shown that this reaction competes with the thio Claisen rearrangement.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1338–1341, October, 1982.     

Thermal analysis of acetylcellulose modified with bis(2-chloroethyl)1-bromovinyl phosphonate

TG, DTA, pyrolytic GC and mass spectrometry methods were used to study the effect of (bis(2-chloroethyl)l-bromovinyl phosphonate on the thermal- and thermooxidative destruction of acetylcellulose. On heating the BVP-containing AC in air the initiation and intensive decomposition of the polymer was found to occur at a reduced temperature. In an inert atmosphere one can also observe a decrease in the characteristic AC decomposition with increasing BVP. The modification results in an accelerated process of dehydration and deacetylation. The effective energy of deacetylation activation (between 220 and 270 °C) decreases from 135 to 80 kJ/mol on the addition of 5.0 wt.% BVP. A comparative study of the mass spectra of the modified AC subjected to stepwise heating up to 300 °C at a rate of 10 deg/min was carried out.

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Zusammenfassung Mittels TG-, DTA-, Pyrolyse-GC- und MS-Methoden wurde der Einfluß von bis(2-chlorethyl)-1-bromvinylphosphat auf den thermischen und thermooxidativen Abbau von Azetylzellulose untersucht. Bei Erhitzen der BVP-haltigen AZ an Luft findet die Initiierung und die intensive Zersetzung des Polymers bei niedrigeren Temperaturen statt. In inerter Atmosphäre kann man mit zunehmendem BVP-Gehalt außerdem ein Absinken des charakteristischen AZ-Zerfalles beobachten. Die Veränderung verursacht die Beschleunigung von Dehydratation und Deazetylierung. Die effektive Energie für die Aktivierung der Deazetylierung (zwischen 220 und 270 °C) sinkt bei Zusatz von 5.0 Gew.-% BVP von 135 auf 80 kJ/mol. Außerdem wurde bei stufenweisem Aufheizen auf 300 °C und bei einer Aufheizgeschwindigkeit von 10 grd/min eine vergleichende Untersuchung der Massenspektren der modifizierten AZ durchgeführt.

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