Solution and gelling properties of gellan benzyl esters

Gellan benzyl esters of different degrees of esterification were prepared, and their gelation behavior was examined. Native gellan and gellan benzyl ester aqueous solutions and the ensuing aqueous gels obtained by cooling their solutions with added salt were studied by means of rheological and small-angle X-ray scattering experiments. Although esterification causes no fundamental changes in the gellan ordered structure, the introduction of bulky benzyl ester groups reduces the backbone propensity of double-helix formation and subsequent helix-helix association (gelation). In consequence, gellan-based gels become less stable both mechanically and thermally with esterification

Highly ordered and tunable polyHIPEs by using microfluidics

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Applications of biopolymers to processes of environmental control

Two new methods of insolubilizing in cellulose triacetate membranes, natural or synthetic polyelectrolytes, able to bind heavy metal ions, were experimented and discussed. The efficiency of the obtained membranes was tested by monitoring the cupric ion adsorption with a copper ion selective electrode (ISE

Biological activity and DNA sequence specificity of synthetic carbamoyl analogues of distamycin

A new penta(N-methylpyrrole carboxamide) analogue of the antibiotic distamycin has been synthesized in which the N-terminal formylamino group was replaced by a carbamoyl moiety. It was substantially more stable than distamycin in aqueous solution and bound to DNA with about the same affinity constant. It had an exemplary margin of selectivity against herpes simplex virus type 1-infected HEp-2 cells in culture compared to uninfected control cells, and was equipotent with distamycin. For comparison, data for analogues containing fewer N-methylpyrrole carboxamide units and/or lacking the carbamoyl replacement are presented. Extensive DNase I footprinting experiments were conducted and revealed that all the distamycin analogues bound to AT-rich nucleotide sequences in three different restriction fragments, irrespective of how many pyrrole rings or which terminal moiety they contained. However, the relative strength of footprints differed significantly among the various compounds, though the apparent size of the binding site did not. With semi-synthetic DNA containing inosine and 2,6-diaminopurine residues in place of guanosine and adenine, respectively, the compounds recognized new binding sites composed of IC-rich clusters and were excluded from binding to their canonical sites. This showed that the process of specific sequence recognition was critically dominated by the placement of the purine 2-amino group in the minor groove of the double helix. </jats:p