The effect of the source pressure on the abundance of ions of noncovalent protein assemblies in an electrospray ionization orthogonal time-of-flight instrument

The effect of elevating the pressure in the interface region of an electrospray ionization orthogonal time-of-flight mass spectrometer on the ion intensity of different noncovalent protein assemblies has been investigated. Elevating the pressure in the interface region generally led to an enhanced detection of high m/z ions. The optimum pressure was found to be dependent on the m/z value of the ions. This pressure effect should be carefully addressed when relating ion abundance in the mass spectra to solution phase abundance of noncovalent protein assemblies.     

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.     

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.     

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.     

9-Alkylideneazafluorenes

A number of tertiary aza-9-fluorenols were obtained from 4- and 2-azafluofenones and were subjected to dehydration in order to synthesize the previously unknown 9-methyleneazafluorenes. The corresponding 9-methyleneazafluorenes and their polymers were obtained simultaneously in relatively stable form from both pyridine-ring-substituted and -unsubstituted 4-aza-9-fluorenols and from 1,3-diphenyl-2-aza-9-fluorenol. On the basis of an analysis of the mass spectrum of the polymer obtained from 9-methylene-4-azafluorene it was concluded that it is evidently isolated in the form of two dimers — dispiro [bis (4-aza-9-fluorene)-1, 3-cyclobutane] and the analogous product of dispiro addition with a 1,2-substituted cyclobutane ring. Condensation of the corresponding azafluorenes with benzaldehyde gave their 9-benzylidene derivatives in the form of geometrical isomers, the structures of which were established on the basis of the PMR spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1234–1240, September, 1978.