Ultraviolet Photodissociation: Developments towards Applications for Mass‐Spectrometry‐Based Proteomics

Unraveling of all of the information contained in proteomes poses a tremendous chemical challenge, which is balanced by the promise of potentially transformational knowledge. Mass spectrometry offers an unprecedented arsenal of tools for diverse proteomic investigations. Recently, it was demonstrated that ultraviolet light can be utilized to initiate unique and potentially useful fragmentations in peptides and proteins. Either nonspecific dissociation or highly specific dissociation at engineered chromophoric sites is possible following photon absorption. The level of specificity and control over fragmentation in these experiments is greater than with other fragmentation methods. Novel techniques made possible by this technology are poised to make substantial contributions to the field of proteomics.     

Syntheses,X-ray,MS, NMR and CD structure determination of nickel(II) complexes of Schiff bases of (S)-N-(2-benzoylphenyl)-1-benzylpyrrolidine-2-carboxamide and aromatic α-amino acids

A preparative procedure for the synthesis of an important chiral synthon of side-chain protected tyrosine was developed and optimised for the minimisation of nickel salts waste. While preparing a similar side-chain protected tryptophan synthon, an unexpected low stability was found of the Boc-protective group of the tryptophan aromatic nitrogen during purification on silica gel. X-ray crystal structure determination, tandem mass spectrometry (MS/MS) and NMR were applied for the elucidation of the structures of the prepared complexes and by-products. Stereochemistry of products of α-methylation of the complexes was assessed using a model tyrosine-derived compound.     

Reaction of 3-chloroquinoline-2,4-diones with ethanolamine and rearrangement of the reaction products

The reaction of tertiary α-chloroketones with ethanolamine has not been hitherto described in the literature. Herein, we describe the reaction of tertiary 3-chloroquinoline-2,4-diones with ethanolamine to give novel 3-(2-hydroxyethylamino)quinoline-2,4-diones. These compounds provide 3-(2-oxooxazolidin-3-yl)quinoline-2,4(1H,3H)-diones and new compounds with dimeric character after reaction with triphosgene. Molecular rearrangement proceeds during the reaction of 3-(2-hydroxyethylamino)quinoline-2,4-diones with isocyanic acid. Three types of reaction products arise: 2-(2-hydroxyethyl)imidazo[1,5-c]quinazoline-3,5-diones, 3-(2-hydroxyethyl)-3,3a-dihydro-2H-imidazo[4,5-]quinoline-4(5H)diones and primarily 5-hydroxy-1-(hydroxyethyl)-1′H-spiro[imidazolidine-5,3′-indole]-2,2′-diones. The reaction mechanism and product stereochemistry are discussed. The ¹H, ¹³C and ¹⁵N NMR spectra of the prepared compounds were measured, and all resonances were assigned from appropriate two-dimensional experiments.     

Photometric, colorimetric, and acid-base characteristics of nitroso-R-salt

Optical and colorimetric characteristics of 1-nitroso-2-naphthol-3,6-disulfonic acid (nitroso-R-salt) are studied in aqueous solutions at pH 4–10. Equations of calibration plots are obtained as the colorimetric functions of the concentration, and the molar coefficients of the colorimetric functions are calculated. The dissociation constants of nitroso-R-salt are determined by colorimetry at an ionic strength of 0.1–0.5, reduced to zero ionic strength, and compared with the literature data. Advantages of colorimetry over spectrophotometry in the determination of the dissociation constants of colored reagents are demonstrated.     

Radical Formation in the Gas‐Phase Ozonolysis of Deprotonated Cysteine

Although the deleterious effects of ozone on the human respiratory system are well‐known, many of the precise chemical mechanisms that both cause damage and afford protection in the pulmonary epithelial lining fluid are poorly understood. As a key first step to elucidating the intrinsic reactivity of ozone with proteins, its reactions with deprotonated cysteine [Cys?H]^? are examined in the gas phase. Reaction proceeds at near the collision limit to give a rich set of products including 1) sequential oxygen atom abstraction reactions to yield cysteine sulfenate, sulfinate and sulfonate anions, and significantly 2) sulfenate radical anions formed by ejection of a hydroperoxy radical. The free‐radical pathway occurs only when both thiol and carboxylate moieties are available, implicating electron‐transfer as a key step in this reaction. This novel and facile reaction is also observed in small cys‐containing peptides indicating a possible role for this chemistry in protein ozonolysis.     

Reaction of 3‐Hydroxyquinoline‐2,4‐diones with Inorganic Thiocyanates in the Presence of Ammonium or Alkylammonium Ions: the Unexpected Replacement of a Hydroxy Group by an Amino Group

3‐Hydroxyquinoline‐2,4‐diones react with KSCN in the presence of the NH$\rm{{_{4}^{+}}}$ ions to generate 2,3‐dihydro‐3‐thioxoimidazo[1,5‐c]quinazolin‐5(6H)‐ones, 2,3‐dihydro‐2‐thioxo‐1H‐imidazo[4,5‐c]quinolin‐4(5H)‐ones, and products of molecular rearrangement of the 3‐aminoquinolinedione intermediates. Starting compounds with a benzyl (Bn) group at C(3) afford 3‐aminoquinolinediones, even when only AcONH₄ is used. The results of the reaction between 3‐hydroxyquinoline‐2,4‐diones and KSCN in the presence of BuNH₂ show that replacing a OH group with a secondary NH₂ group is also possible.     

Effets d'entrée en écoulements pulsés non-newtoniens

Sommaire Le présent travail concerne l'étude des champs de vitesse dans la région d'entrée dans un écoulement pulsé, newtonien et pseudoplastique en conduites cylindriques circulaires. Trois méthodes d'étude ont été utilisées: une méthode analytique, une méthode aux différences finies et une méthode expérimentale basée sur la vélocimétrie à laser. Les résultats obtenus à l'aide de ces méthodes sont confrontés entre eux. Les influences des paramètres rhéologiques et hydrodynamiques sur ces écoulements sont également analysées.

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Summary The purpose of this work is the study of the entrance effects for pulsating flow of inelastic non-newtonian fluids in cylindrical tubes. Founding upon classic methods relating to steady flows, we consider this problem as development of hydrodynamic boundary layer. The evolutions of velocity profiles have been obtained on the one hand by laser velocimetry on aqueous solutions of high polymers and, on the other hand, by numerical resolution of non-linear equations relating to such flows. The relative influences of rheological and hydrodynamical parameters have been analysed and compared.

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Zusammenfassung Die vorliegende Veröffentlichung befaßt sich mit der Einlaufströmung in zylindrische Rohre für den Fall pulsierender Strömungen newtonscher und unelastischer nicht-newtonscher Flüssigkeiten. Dabei werden drei Untersuchungsmethoden verwendet: eine analytische Methode, eine numerische Methode auf der Basis der Finiten Differenzen und eine experimentelle Methode unter Einsatz eines Laser-Doppler-Anemometers. Die mit Hilfe dieser Methoden gewonnenen Ergebnisse werden miteinander verglichen und der Einfluß der verschiedenen rheologischen und hydrodynamischen Parameter auf die Strömungsform wird analysiert.

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Avec 9 figures et 3 tableaux     

Freeze-fracture TEM imaging of robust order in swollen phases of amphiphilic diblock copolymers

We report on the structures exhibited by two different diblock poly(styrene)-b-poly(acrylic acid) (PS-b-PAA) copolymers in water, a selective solvent. Using a combination of X-ray scattering and freeze fracture-transmission electron microscopy (FF-TEM), we show that these structures can be widely swollen while retaining their initial morphology and a high degree of long-range order. The analysis of the FF-TEM pictures also evidences the presence of water crystallites of regular size and shape within the confined water domains. We relate the growth of these crystallites to the high local ionic strength of the water swelling the PAA brushes. Moreover, the confinement of the crystallites growth shows that the swollen phases have a very robust structure, potentially useful for confining colloidal particles.