Interfacial phase transition of an environmentally responsive elastin biopolymer adsorbed on functionalized gold nanoparticles studied by colloidal surface plasmon resonance

The change in optical properties of colloidal gold upon aggregation has been used to develop an experimentally convenient colorimetric method to study the interfacial phase transition of an elastin-like polypeptide (ELP), a thermally responsive biopolymer. Gold nanoparticles, functionalized with a self-assembled monolayer (SAM) of mercaptoundecanoic acid onto which an ELP was adsorbed, exhibit a characteristic red color due to the surface plasmon resonance (SPR) of individual colloids. Raising the solution temperature from 10 degrees C to 40 degrees C thermally triggered the hydrophilic-to-hydrophobic phase transition of the adsorbed ELP resulting in formation of large aggregates due to interparticle hydrophobic interaction. Formation of large aggregates caused a change in color of the colloidal suspension from red to violet due to coupling of surface plasmons in aggregated colloids. The surface phase transition of the ELP was reversible, as seen from the reversible change in color upon cooling the suspension to 10 degrees C. The formation of colloidal aggregates due to the interfacial phase transition of adsorbed ELP was independently verified by dynamic light scattering of ELP-modified gold colloids as a function of temperature. Colloidal SPR provides a simple and convenient colorimetric method to study the influence of the solution environment, interfacial properties, and grafting method on the transition properties of ELPs and other environmentally responsive polymers at the solid-water interface.     

Facile chemoselective synthesis of dehydroalanine-containing peptides

Useful methodology is described for the synthesis of dehydroalanine residues (II) within peptides. The unnatural amino acid (Se)-phenylselenocysteine (I) can be incorporated into growing peptide chains via standard peptide synthesis procedures. Subsequent oxidative elimination affords a dehydroalanine at the desired position. The oxidation conditions are mild and tolerate functionalities commonly found in peptides, including variously protected cysteine residues. To illustrate its utility, cyclic lanthionines have been synthesized by this method.     

A ten-residue fragment of an antibody (mini-antibody) directed against lysozyme as ligand in immunoaffinity chromatography

The interaction between an antibody molecule and a protein antigen is an example of "natural" protein modelling. Amino acids of the antigen-binding site consisting of three hypervariable segments (L1, L2, L3) of the light (L) and three (H1, H2, H3) of the heavy (H) chain of an antibody molecule interact with amino acids present in an epitope of a protein. A ten-residue peptide was synthesized with an amino acid sequence analogous to the hypervariable L3 segment of a monoclonal antibody directed against lysozyme. The peptide was immobilized on CH-Sepharose 4B and the affinity adsorbent was used to purify lysozyme added to a detergent extract of insect cells infected with a recombinant baculovirus. This methodology may also be applicable to other antigen-antibody combinations, in immunoaffinity chromatography for selective purification of a protein or in an immunosensor for detection of a protein.     

Azo coupling and aminomethylation of 2,5-diphenylpyrrole and its derivatives

The azo coupling of 2,5-diphenylpyrrole with arenediazonium chlorides has given previously unknown 3-arylazopyrroles and 4-phenylazo-3-phenylhydrazono-3H-pyrrole. The methylation and reductive acetylation of the anylazo derivatives have led to N-methylarylazo and acetylamino derivatives of 2,5-diphenylpyrrole. 3-Amino-2, 5-diphenylpyrrole has been obtained by the reduction of 3-p-chlorophenylazo-2,5-diphenylpyrrole. The aminomethylation of 2,5-diphenylpyrrole and its derivatives with bis(dialkylamino)methanes had led to aminomethyl derivatives.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5. pp. 612–615, May, 1986.     

Calorimetric,dilatometric and microscopic investigations of the system sodium stearate-stearic acid

Summary AT-x phase diagram of the system sodium stearate (NaSt)-stearic acid (HSt) has been determined by DTA. It shows the existence of five defined association compounds, three of them (2 NaSt · 3 HSt, NaSt · HSt and 3 NaSt · 2 HSt) with an incongruent melting point and the others (5 NaSt · 2 HSt and 5 NaSt · HSt) with a congruent melting point. The latter two compounds pass through various mesomorphic phases before melting. The components do not form solid solutions and are even non-miscible in the mesomorphic state below 200 °C. Mutual miscibility is only observed above this temperature in the subneat and neat region, occurring in the HSt composition range from 0 to 15 and from 0 to 5 mole% respectively. The existence of molecular associations in the liquid state is very probable, particularly in the composition range between 30 and 40 mole% stearic acid. This might result in a liquid structure similar to that present in the melt of anhydrous soaps.

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Zusammenfassung EinT-x Zustandsdiagramm des Natriumstearat (NaSt)- Stearins?ure (HSt)-Systems wurde mittels DTA bestimmt. Es weist fünf definierte assoziierte Verbindungen auf, drei (2 NaSt · 3 HSt, NaSt · HSt und 3 NaSt · 2 HSt) mit einem inkongruenten Schmelzpunkt und zwei (5 NaSt · 2 HSt und 5 NaSt · HSt) mit einem kongruenten Schmelzpunkt. Die zwei letzteren Verbindungen durchlaufen verschiedene mesomorphe Phasen, bevor sie schmelzen. Die Komponenten bilden keine festen L?sungen und sind im mesomorphen Zustand unter 200 °C nicht einmal miteinander mischbar. Nur bei h?heren Temperaturen sind sie v?llig mischbar, und zwar in der “subneat” und “neat” Region, die im HSt-Bereich von 0 bis 15 bzw. von 0 bis 5 Mol% reicht. Die Existenz molekularer Assoziate im flüssigen Zustand ist sehr wahrscheinlich, vor allem im Bereich zwischen 30 und 40 Mol% Stearins?ure. Dies k?nnte zur Bildung von Strukturen in der Flüssigkeit führen ?hnlich, wie dies bei der Schmelze wasserfreier Seifen der Fall ist.

     

Preparation of alkyl-containing derivatives of chitosan and its oligomers in polymer-analogous reactions

It has been shown that the interaction of chitosan and oligochitosan with unsaturated acrylic esters via the nucleophilic addition mechanism and their condensation with heptadecyl isocyanate yield hydrophobic alkyl-containing derivatives of the above polymers. The method of modification of oligochitosan in reactions via end functional groups is developed.     

Effect of plasmatron excitation conditions on the determination of traces

Optimal analysis conditions can be selected and errors caused by variations in the excitation conditions can be decreased or corrected based on the results of studying the temperature distribution along the plasma torch height and correlations between the analytical signal Y and the correcting signal Z that follows the temperature variation in the plasma torch. The obtained correlations can be used to create automated feedback between the spectrum recording system and the mode control system of the plasmatron.     

Luminescence of the pyrene/N,N-diethylaniline triplet exciplex in methanol at room temperature

Fluorescence, whose spectral and magnetic properties permit its assignment to the luminescence of a triplex exciplex, has been discovered at times 3 sec after photoexcitation in the luminescence spectrum of the pyrene+N,N-diethylaniline system in methanol at 600 nm by the method of nanosecond stroboscopic fluorometry.Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 25, No. 5, pp. 623–626, September–October, 1989.     

Isolation of preparations with a high content of eicosapentaenoic acid from the red marine alga Palmaria stenogona

The composition is given of the fatty acids of the red marine algaPalmaria stenogona. The amount of eicosapentaenoic acid (EPA) in the alga was 69.9–77.0% of the total fatty acids. The procedure for isolating EPA of 80–90% purity from the alga is described which includes the saponification of the algal lipids, the selective extraction of the unsaponifiable lipids, the isolation of the free fatty acids, and their separation by the method of crystallizing inclusion complexes of the fatty acids with urea. Institute of Marine Biology, Far Eastern Branch, USSR Academy of Sciences, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 330–333, May–June, 1990.     

Simultaneous multielement atomic-absorption analysis of biological materials

A prototype multielement atomic-absorption spectrometer (SIMAAC) consisting of a continuum source and an echelle polychromator modified for wavelength modulation, has been used to determine several elements in a variety of biological materials. Analyses have been done with flame atomization as well as graphite furnace atomization. Compromise atomization conditions do not significantly limit the accuracy or precision. Analytical results for a variety of samples are reported.