[Changes in Titin Structure during Its Aggregation].

In this paper, the property of the muscle titin protein to form in vitro specific amyloid-like aggregates is discussed. The main difference from the known amyloid aggregates is the formation of a quaternary structure that resembles cross-ß, with no changes in the secondary structure. Based on the results obtained earlier, as well as the results of this study, we make assumptions about changes in the structure of titin that occur during the formation of amyloid-like aggregates. In particular, our X-ray diffraction data on the titin aggregates suggest that ß-strands in the aggregates of this protein are not located perpendicular to the fibril axis, as described for other amyloid proteins, but in parallel. The distance between the ß-sheets in the aggregates may vary, and the ß-sheets themselves are not strictly oriented along one of the axes, which can lead to the appearance of a diffuse ring reflection of ~8-12 Å. In this regard, the titin aggregates should not be called amyloid, but amyloid-like, with a quaternary structure that resembles cross-ß. It cannot be excluded that the formation of this quaternary structure can also occur due to the partial unfolding of titin domains, followed by the interaction of open ß-strands between neighboring domains and/or domains of neighboring molecules.

[Search for Functionally Significant Motifs and Amino Acid Residues of Actin].

The scientific interest to the structural and functional properties of actin is determined by its abundance in cells. Being an important component of the cytoskeleton, actin is involved in many protein-protein interactions. Using crystal structures and molecular models, we have mapped the amino acid residues that are involved in these interactions and form the ATP-binding site of the actin monomer. Moreover, using mass spectrometry and high-performance liquid chromatography methods, we have discovered the regions of the amino acid sequence of actin that form the core of the actin fibril. According to the bioinformatic analysis, these regions are amyloidogenic and are located in the C-terminal region and in the hinge between the first and third subdomains. The data obtained are applicable to chordate actin, because multiple alignment revealed highly conserved amino acid sequences. In turn, the comparison of the chordate actin with the bacterial homologs showed the presence of numerous amino acid substitutions and insertions.

[Interaction of C60 fullerene-polyvinylpyrrolidone complex and brain Aß(1-42)-peptide in vitro].

Using a spectrophotometric method changes occurring in solution containing brain Aß(1-42)-peptide, fullerene C60, and polyvinylpyrrolidone were analyzed. Using the Bent-French method relative binding constants of fullerene C60 with Aß(1-42)-peptide and polyvinylpyrrolidone with Aß(1-42)- peptide were determined. These data suggest that Aß(1-42)-peptide interacting with the C60 fullerene-polyvinylpyrrolidone complex partially displaces polyvinylpyrrolidone and generates a new three molecular compound.

[Comparative studies of amyloid properties of muscles proteins and brain Abeta-peptides and identification of approaches to destruction of their amyloids in vitro].

In this review our data on the comparative study of amyloid properties of titin family proteins and brain Abeta-peptides are represented. Approaches to the destruction of amyloid fibrils of muscle X-protein and brain Abeta(1-42)-peptides by various chemical compounds are also described.

[Study of cytotoxicity of fullerene C60 derivatives].

We investigated the cytotoxicity of the fullerene C60 derivatives. We showed that complexes of C60 fullerene with polyvinylpyrrolidone (m.w. of polyvinylpyrrolidone 10000 and 25000), C60-NO2-proline and C60-alanine had no toxic effect on HEp-2 cells. Sodium salt of polycarboxylic derivative of fullerene C60 exerted a pronounced toxic effect on this cell culture.

[Antiamyloid properties of fullerene C60 derivatives].

A comparative estimation of the ability of complexes of fullerene C60 with polyvinylpyrrolidone and fullerene C60 derivatives (the sodium salt of the polycarboxylic derivative of fullerene C60, sodium fullerenolate), has been carried out. The fullerenes destroyed amyloid fibrils of the Abeta(1-42) peptide of the brain and the muscle X-protein. A study of the effect of fullerenes on muscle actin showed that complexes of fullerene C60 with polyvinylpyrrolidone and sodium fullerenolate did not prevent the filament formation of actin, nor did they destroy its filaments in vitro. Conversely, sodium salt of the polycarboxylic derivative of fullerene C60 destroyed actin filaments and prevented their formation. It was concluded that sodium fullerenolate and complexes of fullerene C60 with polyvinylpyrrolidone are the most effective antiamyloid compounds among the fullerenes examined.

Fullerenolates: metallated polyhydroxylated fullerenes with potent anti-amyloid activity.

It has been revealed for the first time that sodium fullerenolate Na(4)[C(60)(OH)(∼30)] (NaFL), a water soluble polyhydroxylated [60]fullerene derivative, destroys amyloid fibrils of the Aß(1-42) peptide in the brain and prevents their formation in in vitro experiments. The cytotoxicity of NaFL was found to be negligibly low with respect to nine different culture cell lines. At the same time, NaFL showed a very low acute toxicity in vivo. The maximal tolerable dose (MTD) and LD50 for NaFL correspond to 1000 mg kg(-1) and 1800 mg kg(-1), respectively, as revealed by in vivo tests in mice using intraperitoneal drug injection. The observed pronounced anti-amyloid activity and low toxicity of NaFL make it a very promising lead drug for the development of potent fullerene-based therapeutic approaches for the treatment of amyloidoses, such as Alzheimer's disease and others.