Reversed-phase high-performance liquid chromatographic investigation of mucosal nucleosides and bases and urinary modified nucleosides of gastrointestinal cancer patients

Reversed-phase high-performance liquid chromatography (HPLC) was used to determine the levels of nucleosides, bases and their metabolites in perchloric acid extracts of gastrointestinal mucosa. By comparing the levels of these compounds in the normal portion with the neoplastic portion of mucosa resected from malignant cancer patients, it was found that there was significant elevation of the uracil level in the neoplastic mucosa of all eight patients with colorectal cancer (2.7-fold in normal mucosa), but only in the neoplastic mucosa of one out of four patients with gastric cancer. The levels of hypoxanthine and uridine in the colorectal cancer mucosa samples and the inosine in gastric cancer samples were also significantly higher than those in normal mucosa. The urinary modified nucleosides were prefractionated with a boronate affinity gel column, and their levels were determined by the same HPLC method. There was no significant difference in the concentrations of pseudouridine, 1-methylguanosine N2-methylguanosine and N2,N2-dimethylguanosine between urine samples taken before and after surgery from eight patients with malignant colorectal cancer. Contrary to other reports, no significant differences in modified nucleoside levels were observed between urine samples from patients with colorectal cancer and those from normal subjects.     

Characterization of saccharide moiety in the electroplax sodium channel.

Carbohydrate chains on the large peptide of the voltage-sensitive sodium channel from Electrophorus electricus electroplax have been partially characterized by the lectin-blotting technique combined with digestion using three glucosidases: neuraminidase, endo-beta-N-acetylglucosaminidase H, and peptide: N-glycosidase F. The results show that both N-linked oligosaccharides and O-linked (mucin-type) oligosaccharides are present. In N-linked oligosaccharides, the results suggest the presence of complex- and hybrid-type oligosaccharides which contain bisecting N-acetylglucosamine(s), as well as the complex-type oligosaccharides with the alpha-Fuc-GlcNAc-(Asn) residue(s). In O-linked oligosaccharides, they must carry Gal beta1----3GalNAc- moieties which contain NeuNAc residues in the terminal.     

Computational examination of the electrophilic reaction on oxidative polymerization of phenyltrimethylsilane with sulfur chloride

Phenyltrimethylsilane possesses a higher HOMO energy (–9.34 eV) than nonsubstituted benzene (>0.41 eV). The π electron of the phenyltrimethylsilane localizes on the benzene ring at the ipso position rather than at the para position. Two center energies calculated by the MNDO-PM3 method indicate that the C? Si bond is facilitated to cleave in comparison with the C? H (para position) one of the benzene ring. Phenyltrimethylsilane and phenyl bis(trimethylsilane) were polymerized with sulfur chloride through the cationic oxidative polymerization. The product is isolated as oligo(p-phenylene sulfide), with a melting point of 150–190°C. An electrophile attacks the carbon atom linked to the Si atom in phenyltrimethylsilane. The new synthetic route of PPS can be established on the basis of the computational calculation.     

Preparation and reactions of s,s-dimethyl-n-(2,4-dinitrophenyl)sulfilimine

S,S-Dimethyl-N-(2,4-dinitrophenyl)sulfilimine(4a) has been prepared in good yield by use of DMSO, 2,4-dinitroaniline and phosphorus pentoxide in DMF and the role of DMF in this System is discussed. The method has been applied successfully to the syntheses of several sulfilimines. The reactions of 4a with protonic compounds show an interesting ylide-exchange reaction.     

Quantitative analysis of methylguanidine and guanidine in physiologic fluids by high-performance liquid chromatography-fluorescence detection method.

A rapid and sensitive high-performance liquid chromatographic method has been developed for the quantitative analysis of methylguanidine and guanidine in physiological fluids. These quanidino compounds are separated on a 6 x 0.23 cm cation-exchange column with 0.5 M sodium hydroxide solution. The guanidino compounds are detected with a fluorometer, which monitors the fluorescent guanidine derivatives produced by the reaction of the eluted constituents with 9,10-phenanthrenequinone. Sensitivity to sub-nanomole levels of methylguanidine and guanidine is demonstrated. The method was successfully applied to physiological fluids such as serum and cerebrospinal fluid from uremic patients.