Biological properties of low molecular mass peptide dendrimers.

A series of new, low molecular mass, lysine-based peptide dendrimers with varying distribution of cationic and aromatic groups in the structure were synthesized. They expressed antimicrobial activity against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria as well as against fungal pathogens (Candida albicans). Their cytotoxic, haematotoxic, and genotoxic effects were studied. It appears that degree of branching and steric distribution and types of hydrophobic (aromatic) groups and cationic centres are important components of dendrimeric structure and influence both antimicrobial potency and toxicity. Such 3D structure of our dendrimers mimics that of the natural antimicrobial peptides and can be achieved by application of dendrimer chemistry.

Response of DNA, proteins and membrane bilayer in the digestive gland cells of freshwater mussel Unio tumidus to tannins exposure.

Exposure of digestive gland cells (Unio tumidus) in in vitro study to tannins (tannic, ellagic and gallic acid) caused changes in three types of cellular macromolecules, i.e. lipids, proteins and DNA. Two fluorescence probes: TMA-DPH and 12-AS were used to assess the membrane fluidity after incubating cells with different concentrations of tannins (1-60 microM). It was noticed that tannins increased the fluidity in the internal region of the lipid bilayer, but no changes at the surface of the plasma membrane were observed. The number of protein-bound carbonyl groups was quantitated spectrophotometrically using 2,4-dinitrophenylhydrazine (DNPH) assay. Oxidative modification of proteins increased in the cells exposed to tannins in a concentration-dependent manner. Results also showed an increase in carbonyl groups formation after exposing the cells to complex: tannin-Cu(2+) ions. We also investigated the effect of tannins on the level of nuclear DNA damage using the comet assay. We showed that these compounds at 15, 30 and 60 microM induced DNA damage. At these concentrations cell viability measured by trypan blue exclusion assay was not reduced by more than 30%. We also added Cu(2+) ions at 50 microM to assess the influence of the complex tannin-Cu(2+) on DNA lesions. The same method was used to study the possibility to repair this damage in DNA. Experimental data showed that tested polyphenolic acids do not contribute to the induction of strand breaks in nucleic acid at the smallest dose--1 microM and in this range they have a protective effect against the activity of 50 microM Cu(2+) ions.