Combinatorial Generation of Nucleobase Libraries by MCR

Abstract

Multi component reactions (MCR) together with a suitable set of nucleobase building blocks provide a valuable tool for the fast generation of combinatorial libraries. These arrays of compounds are of high interest as anticancer and antiviral drugs. The preparation of small libraries and their analytics is described.     

Reactions of Purine Nucleosides with Aqueous Alkalies: The Effect of the C6 Substituent on the Kinetics of the Multistage Pathway

Abstract

Kinetics of the reactions of 6-substituted 9-(β-Q-ribofuranosyl)purines with aqueous alkalies have been studied liquid chromatographicaIly.     

Mechanism of pH-independent Cleavage and Isomerization of 3′-Ribonucleotide Phosphodiesters

Abstract

The detailed mechanisms of pH-independent cleavage and isomerization reactions of the phosphodiester bond are evaluated by examining kinetics of hydrolytic reactions of selected mono- and dialkyl esters of 3′-uridylic acid. The mechanistic choices are made by comparing LFER's between reaction rates and acidity of the alkyl group of phosphodi- and triesters.     

Structure of a Covalent Complex Between Benzo(a)Pyrene Diol Epoxide and DNA

Abstract

Flow linear dichroism and fluorescence spectroscopy show that the covalent (+)-anti-BPDE-DNA complex adopts two rapidly interchanging conformations. The binding introduces local flexibility in DNA facilitating further covalent attacks.     

Arenesulfonylethoxycarbonyl- a Set of Amino Protecting Groups for DNA and RNA Synthesis

Abstract

Phenyl-, 4-chlorophenyl- and 4-nitrophenylsufonylethoxycarbonyl groups have been reported for the first time as the exocyclic amino protecting groups in nucleoside chemistry. They are all stable under the standard conditions of manipulations in phosphotriester and phosphiteamidite chemistry, they are removable both under the alkaline hydrolytic conditions and also under the influence of non-nucleophilic tertiary bases. N³-Phenyl- and 4-toluenesulfonylethoxycarbonyl derivatives of uridine have been also prepared and characterized by ¹⁵N-NMR spectroscopy, their stabilities under different conditions have been tested.     

Cleavage of the Phosphodiester Bond of Uridylyl-(3′,5′)-8-Carboxymethylaminoadenosine by Hydronium,Hydroxide and Zinc(Ii) Ions: A Model Study Aimed at Elucidating the Potential of a Carboxylate Function as an Intramolecular Catalyst

Abstract

Uridylyl-(3′,5′)-8-carboxymethylaminoadenosine has been synthesised, and its transesterification to uridine 2′,3′-cyclic phosphate in the presence and absence of Zn²⁺ ion has been studied. The results show that a carboxylate function in the vicinity of the phosphodiester bond accelerates the metal ion promoted cleavage but not the metal ion independent reaction. Under acidic conditions, the predominant reaction is the cleavage of the side chain, giving the 8-amino derivative.     

Rational Methods of DNA Synthesis,Exemplified for the Preparation of Parts of the Human Proopiomelanocortin Gene

Abstract

Complete genes can now be prepared in single-batch procedures a) as one long oligonucleotide strand, b) as a number of simultaneously synthesized fragments. For further increase of overall efficiency DNA fragments terminated by a 3′-ribonucleoside can be joined by solid-phase single strand ligation using RNA ligase. This paper describes the application of these techniques to the preparation of parts of the human proopiomelanocortin gene.     

Test System for Measurement of Translational Activity in Vivo

Abstract

A new plasmid which makes it possible to measure formation of a mature protein, as well as prematurely terminated gene products, has been constructed. It can be used for the analysis of translational efficiency of specified codon sequences in vivo.     

Cloning and Expression of Collagen-Derived Protein in E. Coli And Baculovirus System

Abstract

Using appropriately designed primers we amplified a 783 bp frag ment of the triple helical portion of human α1-collagen (I) by PCR methods. The expression of this biosynthetic collagen gene and a modified one containing cell adhesion sequences was carried out in a prokaryotic (E. coli) and a eukaryotic (baculovirus) system. The expression products were purified by affinity chromatography.     

Stability of Benzocaine Formulated in Commercial Oral Disintegrating Tablet Platforms

Pharmaceutical excipients contain reactive groups and impurities due to manufacturing processes that can cause decomposition of active drug compounds. The aim of this investigation was to determine if commercially available oral disintegrating tablet (ODT) platforms induce active pharmaceutical ingredient (API) degradation. Benzocaine was selected as the model API due to known degradation through ester and primary amino groups. Benzocaine was either compressed at a constant pressure, 20 kN, or at pressure necessary to produce a set hardness, i.e., where a series of tablets were produced at different compression forces until an average hardness of approximately 100 N was achieved. Tablets were then stored for 6 months under International Conference on Harmonization recommended conditions, 25°C and 60% relative humidity (RH), or under accelerated conditions, 40°C and 75% RH. Benzocaine degradation was monitored by liquid chromatography–mass spectrometry. Regardless of the ODT platform, no degradation of benzocaine was observed in tablets that were kept for 6 months at 25°C and 60% RH. After storage for 30 days under accelerated conditions, benzocaine degradation was observed in a single platform. Qualitative differences in ODT platform behavior were observed in physical appearance of the tablets after storage under different temperature and humidity conditions.