Terpolymerization of sulfur dioxide or maleic anhydride with unsaturated compounds under ultraviolet irradiation

The effect of ultraviolet irradiation on the terpolymerization was investigated. In the terpolymerizations of sulfur dioxide–butene-1–acrylonitrile, sulfur dioxide–butene-1–n-butyl acrylate, and maleic anhydride–allyl chloride–acrylonitrile systems, the composition of the terpolymers prepared under ultraviolet irradiation was different from those prepared in the dark. The unit content of sulfur dioxide and butene-1 or of maleic anhydride and allyl chloride in the terpolymer increased under ultraviolet irradiation. The nature of the growing end under ultraviolet irradiation is supposed to be the same as that of the dark polymerization on the basis of the same solvent effect on the terpolymer composition, the rate of polymerization and the molecular weight of polymer. The experimental results suggest that the complex between sulfur dioxide and butene-1 or maleic anhydride and allyl chloride might be excited by ultraviolet light and the excited complex may participate in the terpolymerization.     

Multi-turn time-of-flight mass spectrometers with electrostatic sectors

The mass resolution of a time-of-flight (TOF) mass spectrometer is directly proportional to its total flight pathlength. Multi-turn or multi-passage ion optical geometries are necessary to obtain fight distances of sufficient length within reasonable size limitations. We have investigated ion optics for a multi-turn TOF mass spectrometer with electrostatic sectors. The concept of 'perfect' focusing conditions is introduced. Furthermore, a new type of multi-turn TOF mass spectrometer, the MULTUM Linear plus, was developed. It consists of four cylindrical electric sectors and 28 electric quadrupole lenses. It has a vacuum chamber 60 x 70 x 20 cm in size. Mass resolution is demonstrated to increase according to the number of ion cycles. A mass resolution of 350 000 (m/z = 28, FWHM) was achieved after 501.5 cycles. The MULTUM Linear plus analyzer is not simple, however; 28 electric quadrupole lenses are used. In order to reduce the number of ion optical parts, an improved multi-turn TOF mass spectrometer, the MULTUM II, consisting of only four toroidal electric sectors, was also developed. The possibility of tandem mass spectrometric applications using multi-turn TOF mass spectrometers is also discussed.     

Aromatic polyesters obtained directly from hydroxybenzoic acids by hexachlorocyclotriphosphatriazene (PNC) in pyridine

Polyaryl esters of moderate molecular weights were prepared by the direct polycondensation reaction of hydroxybenzoic acids and its derivatives with hexachlorocyclotriphosphatriazene (also known as phosphonitrilic chloride trimer, PNC) as a condensing agent in pyridine. Copolymerization of p-hydroxybenzoic acid with several hydroxybenzic acid derivatives was carried out to improve the processability of the polymer of p-hydroxybenzoic acid, which yields fusible and soluble copolymers of high inherent viscosities. Polymer solubility and thermal behavior were examined.     

Studies of nucleosides and nucleotides—LXXIV: Purine cyclonucleosides—34 a new method for the synthesis of 2'-substituted 2'-deoxyadenosines

8,2'-O-Cycloadenosine was protected at 3' and 5'-OHs with acetyl groups and cleaved using liq. H₂S. Subsequent dethiolation and mesylation gave 2'-O-mesyl-3',5'-di-O-acetyl-arabinosyladenine (6). When 6 or its deacetylated parent compound (7) was heated with sodium azide in DMF, 3'-azido-3'-deoxyxylofuranosyladenine (9) was the only product. The cyclonucleoside was then protected with tetrahydropyranyl groups and subjected to a similar series of reactions as above to give 2'-O-mesyl-3',5'-di-O-tetrahydropyranylarabinosyladenine (14). The compound 14 was heated with sodium azide after which acidic deprotection afforded 2'-azido-2'-deoxyadenosine (16). Hydrogenation of 16 gave 2'-amino-2'-deoxyadenosine (18). 2'-Chloro-2'-deoxyadenosine (19) was also obtained by treatment of 14 with lithium chloride and subsequent deprotection. UV, IR and NMR spectral data of these compounds are described.     

Solubilization of lanthanide ions by cyclodextrins in basic aqueous solutions

Cyclodextrins form complexes with lanthanide ions in basic aqueous solutions. This complex formation in basic solution dramatically enhances the solubility of lanthanide ions, which are otherwise insoluble due to the formation of hydroxide gels. Solutions of the -cyclodextrin-Ce³⁺ complex effectively hydrolyze 2-deoxyadenosine-5-monophosphate to 2-deoxyadenosine.     

Metal-ion-assisted hydrolysis of dipeptides involving a serine residue in a neutral aqueous solution

Dipeptides having a serine residue at the C-terminus, X-Ser, where X is an appropriate amino acid residue, were efficiently hydrolyzed in the presence of ZnCl2 at pH 7.0. The rapid hydrolysis of X-Ser is due to an autocatalysis of the hydroxy group in the serine residue, and is found to be accelerated by a metal ion, in particular by ZnCl2. Roles of the metal ion in the hydrolysis of peptides involving a serine residue, in relation to the recently reported protein cleavages, are discussed.     

Chemical synthesis of the 5-́half molecule of E.coli tRNA2GLY

A tritriacontanucleotide which has the sequence of the 5$\text{-}\text{?}$half molecule of E.coli glycine tRNA₂, was synthesized by the phosphotriester method involving p-anisidate protection for the 3$\text{-}\text{?}$phosphate ends. Di- and trinucleotide units were prepared from 5$\text{-}\text{?}$dimethoxytrityl-2$\text{-}\text{?}$O-tetrahydrofuranyl-3?-O-(o-chlorophenyl)phosphoryl derivatives of uridine, N-benzoylcytidine, N-benzolyadenosine and N-iso-butyrylguanosine by condensation with 3$\text{,}\text{?}$5$\text{-}\text{?}$unprotected nucleosides followed by phosphorylation to give 3$\text{-}\text{?}$phosphodiester blocks. The 3$\text{-}\text{?}$terminal dimers and trimers were synthesized by using 3$\text{-}\text{?}$(o- chlorophenyl)phosphoro-p-anisidates instead of 3?,5?-unprotected nucleosides. The 3?-phosphodiesters of oligonucleotides with a chain length of larger than 5 were obtained by removal of the 3?-phosphoro-p-anisidate with isoamyl nitrite. The 5$\text{-}\text{?}$dimethoxytrityl group was removed by treatment with zinc bromide under anhydrous conditions. Fragments were designed to use common dimer blocks and to reduce the step for 5$\text{-}\text{?}$deblocking of larger fragments. Finally a 3$\text{-}\text{?}$phosphodiester block with a chain length of 20 was condensed with a 5$\text{-}\text{?}$OH component (tridecanucleotide). The fully protected 33 mer was deblocked and purified by chromatography. The structural integrity of the product was confirmed by mobility shift analysis and complete digestion with RNase T2.     

Versatile lipid profiling by liquid chromatography–high resolution mass spectrometry using all ion fragmentation and polarity switching. Preliminary application for serum samples phenotyping related to canine mammary cancer

Lipids represent an extended class of substances characterized by such high variety and complexity that makes their unified analyses by liquid chromatography coupled to either high resolution or tandem mass spectrometry (LC–HRMS or LC–MS/MS) a real challenge. In the present study, a new versatile methodology associating ultra high performance liquid chromatography coupled to high resolution tandem mass spectrometry (UHPLC–HRMS/MS) have been developed for a comprehensive analysis of lipids. The use of polarity switching and “all ion fragmentation” (AIF) have been two action levels particularly exploited to finally permit the detection and identification of a multi-class and multi-analyte extended range of lipids in a single run. For identification purposes, both higher energy collision dissociation (HCD) and in-source CID (collision induced dissociation) fragmentation were evaluated in order to obtain information about the precursor and product ions in the same spectra. This approach provides both class-specific and lipid-specific fragments, enhancing lipid identification. Finally, the developed method was applied for differential phenotyping of serum samples collected from pet dogs developing spontaneous malignant mammary tumors and health controls. A biological signature associated with the presence of cancer was then successfully revealed from this lipidome analysis, which required to be further investigated and confirmed at larger scale.