Anna Malovíková

Interaction of alginates and pectins with cationic polypeptides

The interactions of alginates of various compositions and of pectins with basic polypeptides, namely, poly(l-lysine) and poly(Lys-Ala-Ala), have been studied by means of circular dichroism. The complexation efficiency of both types of anionic polysaccharides were compared and quantified on the basis of the extent of the induced α-helical conformation of the polypeptide. The alginate with a high content of guluronic acid (∼ 75%) did not interact with poly(l-lysine). Pectins and alginates interacted with poly(Lys-Ala-Ala) rather intensively. The difference in efficiency of interaction of l-guluronan and d-galacturonan with poly(l-lysine) results from the difference in the conformational flexibility of their polyanionic chains in solution. l-Guluronan maintains the rigid two-fold symmetry in solution, and d-galacturonan is conformationally adaptable in the course of interaction.

Impact of cadmium stress on two maize hybrids.

Some physiological parameters and composition of the root cell walls of two maize hybrids (monocots), the sensitive Novania and the tolerant Almansa were studied after treatment with cadmium cations. After 10 days of Cd2+ treatment (1xa0×xa010-5xa0M and 5xa0×xa010-5xa0M), plant growth inhibition, in the sensitive hybrid in particular, as well as a certain alteration in root structure and pigment content were observed. The Cd2+ accumulation was ten times higher in the roots than in the shoots. Chemical analyses and atomic absorption spectroscopy proved that Cd2+ modified the composition of the root cell walls by a significant increase in the content of alkali-soluble polysaccharide fractions, particularly in the tolerant hybrid. An increase in the content of phenolic compounds, mainly in the tolerant hybrid, and a decrease in protein content were observed in the presence of Cd2+ in the alkali fractions. The results indicate that the changes in the cell wall polysaccharide fractions and their proportion to lignin and cellulose are obviously involved in the tolerance and/or defence against Cd2+ of the maize hybrids studied.

Surface-Active and Viscous Behavior of HM-CMC in Aqueous Solutions

Water-soluble, partially hydrophobized derivatives of carboxymethylcellulose (CMC) were prepared by the transesterification reaction using the methyl ester of rapeseed oil (MERO). The chemical modification was performed in reaction media H2O/DMF with and without K2CO3 as catalyst, at various reaction conditions and using microwave radiation with controlled power as heating source. The obtained hydrophobically modified carboxymethylcellulose (HM-CMC) derivatives were characterized by FT-IR spectroscopy. The surface-active and viscometric properties of aqueous solutions of unmodified CMC and its HM-CMC derivatives were investigated. The surface-active properties were studied by surface tension, critical micelle concentration and emulsifying efficiency. The complexation of CMC or some HM-CMC derivatives with cationic surfactants – tetraalkylammonium bromides (CnTAB) in aqueous medium was studied by measuring the surface tension. The studied derivatives showed, in spite of moderate surface tension-lowering effects, excellent emulsifying activity for ‘oil in water’ type emulsions comparable to that of the commercial emulsifier Tween 20. The viscometric properties were investigated in the dilute domain. For all HM-CMC solutions the intrinsic viscosities were distinctly lower than for CMC, probably due to molecular degradation. The increased Huggins constant of some of the derivatives are indicative of intramolecular hydrophobic interactions. The results suggested that the HM-CMC derivatives and their complexes with CnTAB surfactants can be exploited as potential biosurfactants in various industrial applications.

Maize shoot cell walls under cadmium stress

The composition of shoot cell walls of two maize hybrids (Zea mays L.), the sensitive Novania and the tolerant Almansa, both after cadmium treatment was studied. Previous results showed a smaller effect of cadmium on shoot physiological parameters (e.g., elongation, dry mass, photosynthetic pigments content) in both hybrids compared to their roots. Changes in the composition of shoot cell walls were observed. It was ascertained that the amount of hemicelluloses in shoot cell walls decreased and the amount of lignocellulose complex increased in the sensitive hybrid; the opposite was observed in the tolerant Almansa. Dissimilarities in the cell wall structure of shoots, compared to the roots, in both hybrids were observed mainly in higher quantities of total lignin, in hemicelluloses fractions. The lignocellulose complex remained unchanged in the shoots in comparison to the roots. Nevertheless, in both hybrids, the highest Cd2+ amount was found in hemicelluloses. Such modification of the cell walls might affect the amount of binding sites resulting in lower cell wall permeability and subsequently in a lower pollutant influx into the protoplast.

Oligogalacturonate hydrolase with unique substrate preference from the pulp of parsley roots

The main form of pectate hydrolases in the cell wall of parsley roots showed a unique substrate preference of a plant exopolygalacturonase because it clearly preferred the substrates with degree of polymerization about 10. This form was separated from the others, purified and characterized. Enzyme exhibited sharp pH optimum corresponding to pH 4.7, molecular mass 53.5 kDa, and isoelectric point 5.3. It was stable at 50°C in 2-h assay and had optimum of temperature at 60°C (activation energy being 37.0 kJ/mol). The interaction with concanavalin A indicated the glycosylation of enzyme. Substrates were cleaved from the non-reducing end.

THERMOOXIDATION STABILITY OF SOME DEGRADED XYLOGLUCANS

The effect on chemiluminescence intensity ant thus on thermal oxidation of the initial molar mass of xyloglucans has been examined. The molar mass was pre‐set by degradation using ultrasonic and/or gamma‐rays. It has been demonstrated that the initial molar mass has a significant effect on the course of xyloglucan oxidation.