Application of capillary zone electrophoresis and reversed-phase high-performance liquid chromatography in the biopharmaceutical industry for the quantitative analysis of the monosaccharides released from a highly glycosylated therapeutic protein

Two assays for the quantitative determination of the neutral and amino-monosaccharides attached to a therapeutic glycoprotein were developed using capillary zone electrophoresis (CZE) and RP-HPLC. These assays meet the strict batch release requirements of the quality control in biopharmaceutical industry. The monosaccharides were released from the glycoprotein by hydrolysis with 2N trifluoroacetic acid. In the CZE assay the monosaccharides were reacetylated prior to derivatization with 8-aminopyrenesulfonic acid (APTS), reacetylation in the glycoprotein matrix was investigated in detail. The RP-HPLC method used pre-column derivatization with anthranilic acid in methanol-acetate-borate reaction medium; reacetylation was not necessary. However, epimerization of the different monosaccharides was observed and studied in detail. For the quantitative assay, separation of the amino-monosaccharide epimers had to be developed. The HPLC assay was validated.     

Spectral and electrochemical study of coordination molecules Cu4OX6L4: 3-Methylpyridine and 4-Methylpyridine Cu4OBrnCl(6−n)L4 complexes

The tetranuclear Cu₄OBr_nCl_(6-n)L₄ complexes, where L = 3-methylpyridine (3-Mepy), 4-methylpyridine (4-Mepy) and n=0–6 with trigonal bipyramidal coordination of copper(II) were prepared and their infrared and electronic absorption spectra as well as cyclic voltammograms in nitromethane solutions were measured. The polyhedra in Cu₄OBr_nCl_(6−n) (3-Mepy)₄ molecules are less distorted comparing with those of 4-Mepy analogues as indicated by infrared Cu₄O absorptions, far infrared Cu—Br, Cu—Cl, and Cu—N absorptions, d—d bands in electronic spectra and potentials, measured by cyclic voltammetry. The 3-Mepy complexes exhibit strong single infrared Cu₄O absorptions, while for related 4-Mepy complexes doubly split Cu₄O bands were observed. Two strongly overlapped d—d bands in electronic absorption spectra of the 3-and 4-Mepy complexes in nitromethane were resolved by Gaussian fitting. The 4-Mepy ligand produces slightly stronger ligand field than its 3-Mepy analogue. The maxima of high-energy d—d bands are in a linear correlation with the number of bromide ligands. The correlations for corresponding low-energy bands are considerably deviated from linearity. The halfwave potentials of the complexes in nitromethane correlate with both the number of bromides and the data of electronic absorption spectra suggesting that the reducing electron at the electrode process enters the half-filled d _{z 2} orbital of the copper(II) atom. The origin of a difference between the 3-and 4-Mepy complexes in their spectral and electrochemical properties is also discussed.     

Transuranic elements alpha-particle energy analysis using nuclear track in solids methodology

This paper presents a method for the energy analysis of alpha-particles emitted by transuranic elements via a novel technique using Nuclear Tracks. The method is based on the relationship between the energy deposited in the detection material and the diameter of the track, that is formed by chemical etching. The method involves CR-39 polycarbonate as the detector material, one-step chemical etching after irradiation, and a digital image analysis system for automatic reading of the track diameters. The experimental study included alpha-particles in the energy range 5.1 MeV to 5.8 MeV emitted by²³⁹Pu,²⁴¹Am and²⁴⁴Cm. The quantitative results provide a clear signature to identify each one of the emitters based on a characteristic track diameter.     

Darstellung und Struktur von Pyrazolyl-Kationen mit Polymethin- und Methan-Gerüst

The 4-pyrazoline-3-one1 reacts with 4-dimethylaminobenzaldehyde to yield the stable asymmetric cyanine dye2b which reacts with1 to give the colorless (aryl) (dipyrazolyl) methane3b. Using aldehydes with less cationstabilizing groups the polymethines2 are not isolated but only the methanes3. The structures of2b and3 are discussed by¹ H,¹³C and Hetero NMR spectra.     

Influence of the pyridine methyl substituent position on the chemical changes of the NCS groups in the thermal decomposition of coordination compounds of the type Cu(NCS)2L2

The influence of the position of the CH₃ group in picoline and lutidine ligands on the degree of chemical change of the NCS groups in coordination compounds of the type Cu(NCS)₂L₂ (whereL=2-, 3- and 4-picoline, and 2,3-, 2,4-, 2,5-, 2,6-, 3,4- and 3,5-lutidine) is dealt with. The most marked effect of the CH₃ group is found to be exerted in position 4. This effect of the methyl group on the degree of chemical change points to the mutual influence of the ligands in coordination compounds of Cu(II).

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Zusammenfassung Der Artikel befaßt sich mit dem Einfluß der Lage der CH₃ Gruppe in Pikolinen und Lutidinen als Liganden auf den Grad der chemischen Änderungen der Gruppen NSC in Koordinationsverbindungen des Typs Cu(NCS)₂L₂ (L=2-, 3- und 4-Pikoline, 2,3-, 2,4-, 2,5-, 2,6-, 3,4- und 3,5-Lutidine). Der ausgeprägteste Effekt der CH₃ Gruppe wurde in der Position 4 beobachtet. Dieser Einfluß der Methylgruppe auf das Ausmaß der chemischen Änderungen deutet auch auf die gegenseitige Wirkung der Liganden in Koordinationsverbindungen von Cu(II).

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Résumé L'article a trait à l'influence de la position du groupe CH₂ dans les picolines et lutidines, en tant que ligands, sur le degré des changements chimiques des groupes SCN dans les composés de coordination du type Cu(SCN)₂L₂ (L=2-, 3 et 4-picoline, 2,3-, 2,4-,2,5-, 2,6-, 3,4- et 3,6-lutidine). L'effet le plus prononcé du groupe CH₃ s'observe en position 4. Cette influence du groupe méthyle sur le degré des changements chimiques indique aussi l'influence mutuelle des ligands dans les composés de coordination du Cu(II).

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- , , NCS Cu(NCS)₂,L₂, L=2-, 3- 4- , 2.3-, 2.4-, 2.5-, 2.6-, 3.4- 3.5-. , 4. Cu(II).

     

Geometrical structure of yttrium and metal-bromine complexes in solution: limitations of extended X-ray absorption fine structure analysis (EXAFS)

An extensive study on the appearance of multi-electron features in the X-ray absorption spectra of several yttrium(III)-based compounds has been performed. The existence of a multi-electron transition of non-negligible intensity within the extended X-ray absorption fine structure (EXAFS) region of the Y K-edge spectra has been proven. The impact of such features in the EXAFS analysis is made evident for aqueous solutions of YBr3 x 6H2O in liquid and glassy states in the concentration range 0.005-2.0 M, in which this transition induces an overestimation in the coordination numbers derived from EXAFS. We have performed theoretical computation of cross-sections for the double-electron processes at the K-edge of both Y and Br. These computations have been applied to the experimental EXAFS K-edge spectra of both Y and Br in several solids and in aqueous solutions. While in the case of Y K-edge spectra the presence of such multi-electron transitions was seen to seriously affect the standard EXAFS analysis, its influence in the case of Br K-edge spectra was determined to be negligible.     

Reactions of pyrrolidine enamines of cyclic and acyclic 3,4-dioxobutanoic acid Derivatives with dimethyl acetylenedicarboxylate. A new case of atropoisomerism.

Reaction conditions and structure of the starting enamines (cyclic or open-chain) determine greatly the final products of the title reactions. Whereas in benzene and acetonitrile, DMAD and 1 give a mixture of the diastereoisomeric dienamines 5, in methanol they afford pirrolizine 3. Enaminofuranones 2 and 10 furnish the corresponding “Michael adducts” 7a,b,c and 11a,b,c but fail to yield pirrolizines. It has been demonstrated that above b and c adducts differ exclusively on the arrangement of groups around a chiral axis.     

Nachweis isomerer Phenole und Nitroaniline,von Naphthylamin und Anilin

Zusammenfassung Die mit diazotiertem p-Nitranilin hergestellten Tetrazoverbindungen von Phenolderivaten geben mit Magnesium in alkalischem Mediumfarbige Komplexe. Die Farbe des Komplexes ist verschieden bei substituierten und nicht substituierten bzw. verschieden substituierten Phenolen. Damit kann man Phenol-, Kresol- und Chlorphenol-Isomere bzw. 2,4- und 2,6-Dichlorphenol unterscheiden.Beim Diazotieren von Nitranilin und Kuppeln mit Anilin entstehen. Indikatorsäuren; p-Nitranilin bildet die stärkste Indikatorsäure, m-Nitranilin die schwächste. Auf dieser Grundlage können alle drei Isomeren nebeneinander nachgewiesen werden. Außerdem bilden die aus p- und o-Nitranilin entstandenen Indikatoren mit Magnesium verschieden gefärbte Nitronsäurekomplexe, während m-Nitranilin, das zur Nitronsäuretautomerie nicht befähigt ist, keinen Komplex bildet.Naphthylamine geben mit diazotiertem p-Nitranilin in wäßrigem. Medium eine Indikatorbase, Anilin eine Indikatorsäure. In alkoholischem Medium führt-Naphthylamin bei Kupplung von diazotiertem p-Nitranilin zu einem amphoteren Säure-Base-Indikator, aber-Naphthylamin und Anilin zu Indikatorsäuren. Damit kann man Naphthylamin und Anilin nebeneinander nachweisen. Kuppelt man Phenyldiazoniumchlorid mit Naphthylamin, so erhält man mit-Naphthylamin eine starke Indikatorbase, mit- Naphthylamin eine schwache Indikatorbase. Auf der Basis dieser Indikatorwirkung kann man-Naphthylamin neben- Naphthylamin nachweisen.

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Summary The tetrazo compounds of phenol derivatives prepared with diazotizedp-nitraniline yield colored complexes with magnesium in alkaline surroundings. The color of the complexes differs with substituted and non-substituted or variously substituted phenols. It is possible in this way to differentiate phenol, cresol and chlorophenol isomers, and also 2,4- and 2,6-dichlorophenol.Indicator acids result from diazotized nitraniline coupled with aniline;p-nitraniline yields the strongest indicator acid,m-nitraniline the weakest. With this information as a basis, all three isomers can be detected in the presence of each other. In addition, the indicators produced fromp- ando-nitraniline give nitronic acid complexes with magnesium that differ in color, whilem-nitraniline, which is not capable of nitronic acid tautomerism, forms no complex.Naphthylamines gives an indicator base in aqueous medium with diazotizedp-nitraniline, whereas aniline yields an indicator acid. In alcoholic medium, 1-naphthylamine on coupling with diazotizedp-nitraniline produces an amphoteric acid-base indicator, but 2-naphthylamine and aniline yield indicator acids. Naphthylamine and aniline can be detected in this way in the presence of each other. If phenyldiazonium chloride is coupled with naphthylamine, a strong indicator base is obtained with 1-naphthylamine, a weak indicator base with 2-naphthylamine. This indicator action is the basis of the detection of 1-naphthylamine in the presence of 2-naphthylamine.

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Résumé Les composés tétrazoïques des dérivés phénoliques qui se forment avec lap-nitraniline diazotée, donnent avec le magnésium, en milieu alcalin, des complexes colorés. La couleur du complexe diffère suivant que les phénols sont substitués, non substitués ou différemment substitués. On peut ainsi distinguer le phénol, les crésols et les chlorophénols isomères, ainsi que les dichloro-2,4 et -2,6 phénols.En diazotant la nitraniline et en copulant avec l'aniline, des acides indicateurs prennent naissance, lap-nitraniline donnant l'acide indicateur le plus fort, lam-nitraniline le plus faible. En s'appuyant sur ce fait, on peut rechercher les trois isomères en présence les uns des autres. En outre, les indicateurs qui prennent naissance à partir de lap- et de l'o-nitraniline forment avec le magnésium différents complexes colorés acinitrés, alors que lam-nitraniline, qui n'est pas susceptible d'une tautomérie de l'acide nitronique, ne donne pas de complexe.Les naphtylamines donnent avec lap-nitraniline diazotée, en milieu aqueux, une base indicateur et l'aniline, un acide indicateur. En milieu alcoolique, l'-naphtylamine conduit par copulation de lap-nitraniline diazotée à un indicateur acide-base amphotère mais la-naphtylamine et l'aniline à des acides indicateurs. On peut ainsi rechercher la naphtylamine et l'aniline en présence l'une de l'autre. Si l'on copule le chlorure de phenyldiazonium avec la naphtylamine, on obtient avec la forme une base indicateur forte et avec la forme une base indicateur faible. En se fondant sur cette action d'indicateur, on peut rechercher l'-naphtylamine en présence de-naphtylamine.

     

Reaction-based machine learning representations for predicting the enantioselectivity of organocatalysts

Hundreds of catalytic methods are developed each year to meet the demand for high-purity chiral compounds. The computational design of enantioselective organocatalysts remains a significant challenge, as catalysts are typically discovered through experimental screening. Recent advances in combining quantum chemical computations and machine learning (ML) hold great potential to propel the next leap forward in asymmetric catalysis. Within the context of quantum chemical machine learning (QML, or atomistic ML), the ML representations used to encode the three-dimensional structure of molecules and evaluate their similarity cannot easily capture the subtle energy differences that govern enantioselectivity. Here, we present a general strategy for improving molecular representations within an atomistic machine learning model to predict the DFT-computed enantiomeric excess of asymmetric propargylation organocatalysts solely from the structure of catalytic cycle intermediates. Mean absolute errors as low as 0.25 kcal mol⁻¹ were achieved in predictions of the activation energy with respect to DFT computations. By virtue of its design, this strategy is generalisable to other ML models, to experimental data and to any catalytic asymmetric reaction, enabling the rapid screening of structurally diverse organocatalysts from available structural information.

A machine learning model for enantioselectivity prediction using reaction-based molecular representations.     

Selective determination of copper with pyridoin phenylhydrazone as chromogenic extraction reagent

Summary The synthesis, characteristics and analytical applications of pyridoin phenylhydrazone are described. It reacts with copper(I) to produce an orange 11 complex ( _max=450 nm,=2.1×10⁴l· mole^–1·cm^–1) in aqueous ethanolic solution; it behaves as a cuproin type reagent. The orange complex can be extracted into amyl alcohol ( _max=440 nm,=2.0×10⁴l·mole^–1·cm^–1), and used for the spectrophotometric determination of trace amounts of copper. Interferences have been investigated.

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Zusammenfassung Synthese, Eigenschaften und analytische Anwendung von Pyridoin-phenylhydrazon wurden beschrieben. Es reagiert mit Cu(I) unter Bildung eines orange gefärbten 11-Komplexes in wäßrig-alkoholischer Lösung ( _max=450 nm,=2,1×10⁴l·mol^–1·cm^–1); das Reagens verhält sich ähnlich wie Cuproin. Der erwähnte Komplex läßt sich mit Amylalkohol extra-hieren ( _max=440 nm,=2,0×10⁴l·mol^–1·cm^–1) und zur spektrophoto-metrischen Bestimmung von Kupferspuren benützen. Auftretende Störungen wurden angegeben.