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PubMed1990

Preparation, properties and antileukemic activity of arabinosylcytosine polysaccharide conjugates.

1. Conjugates of 1-beta-D-arabinofuranosylcytosine (araC) with polysaccharides containing carboxyl groups, such as polygalacturonic acid (PGA) and carboxymethylated yeast beta-D-glucan (CMG) were prepared. 2. Activation of the polysaccharidic carboxyl group by isobutylchloroformiate and formation of a peptide bond via 4-NH2 group of araC was used for a coupling reaction. 3. Elementary analysis, u.v. and i.r. spectra confirmed the structures of the conjugates. 4. The conjugates were most stable against the hydrolysis under the mild acid conditions. 5. It was also shown that under the physiological conditions trypsin catalyze the conjugate hydrolysis and the catalytic effect is higher than that of chymotrypsine. 6. It is suggested that trypsin or trypsin-like proteases could participate in the hydrolysis of the conjugates in vivo. PGA-araC and CMG-araC showed 1.5- or 2.5-times higher antileukemic activity than both free araC or polysaccharides.

Animals↗
PubMed1993

Influence of the chromatographic capacity factor (log k') as an index of lipophilicity in the antibacterial activity of a series of 6-fluoroquinolones. Relationship between physico-chemical and structural properties and their hydrophobicity.

The aim of this study was to establish the influence of lipophilicity on the antibacterial activity (log 1/MIC50) of 22 fluoroquinolones and to assess the influence of their electronic, steric and topological properties on their hydrophobicity. The lipophilicity of the compounds, expressed as the chromatographic capacity factor (log k'), was determined by ion-pair reversed-phase HPLC. On the basis of the mathematical models developed, an attempt was made to confirm the mechanism of interaction of the quinolones with DNA-gyrase proposed previously.

Anti-Infective Agents↗
PubMed1991

Site-directed mutagenesis in haemoglobin. Functional role of tyrosine-42(C7) alpha at the alpha 1-beta 2 interface.

To clarify the functional role of Tyr-42(C7) alpha, which forms a hydrogen bond with Asp-99(G1) beta at the alpha 1-beta 2 interface of human deoxyhaemoglobin, we engineered two artificial mutant haemoglobins (Hb), in which Tyr-42 alpha was replaced by Phe (Hb Phe-42 alpha) or His (Hb His-42 alpha), and investigated their oxygen binding properties together with structural consequences of the mutations by using various spectroscopic probes. Like most of the natural Asp-99 beta mutants, Hb Phe-42 alpha showed a markedly increased oxygen affinity, a reduced Bohr effect and diminished co-operativity. Structural probes such as ultraviolet-region derivative and oxy-minus-deoxy difference spectra, resonance Raman scattering and proton nuclear magnetic resonance spectra indicate that, in Hb Phe-42 alpha, the deoxy T quaternary structure is highly destabilized and the strain imposed on the Fe-N epsilon (proximal His) bond is released, stabilizing the oxy tertiary structure. In contrast with Hb Phe-42 alpha, Hb His-42 alpha showed an intermediately impaired function and only moderate destabilization of the T-state, which can be explained by the formation of a new, weak hydrogen bond between His-42 alpha and Asp-99 beta. Spectroscopic data were consistent with this assumption. The present study proves that the hydrogen bond between Tyr-42 alpha and Asp-99 beta plays a key role in stabilizing the deoxy T structure and consequently in co-operative oxygen binding.

Hemoglobins↗