[Atomic force microscopy monitoring of temperature dependence of cytochrome BM3 oligomeric state].

The change in temperature is one of the factors affecting the activity of enzymes. In this work thermal denaturation and aggregation of cytochrome P450 BM3 were studied by atomic force microscopy. To determine specific temperature transitions the fluorescence analysis was used. In the low melting temperature range, 10-33 degrees C, a decrease in the fluorescence intensity of aromatic residues was observed with an increase in the fluorescence intensity of flavin groups. Protein melting in this range indicated three narrow S-shaped cooperative transitions at temperatures 16, 22 and 29 degrees C. Atomic force microscopy analysis in this temperature range showed that the shape of BM3 molecules remained globular in the form of compact objects (heights h < 7 nm, lateral dimensions d < 50 nm), but protein oligomeric state changed. The first two transitions were accompanied by a decrease in the degree of oligomerization and the third one was accompanied by its increase.

[Irreversible chemical AFM-fishing for the detection of low-copied proteins].

The atomic-force microscopy-based method of irreversible chemical AFM-fishing (AFM-IF(Ch)) has been developed for the detection of proteins at ultra-low concentrations in solution. Using this method, a very low concentration of horseradish peroxidase (HRP) protein (10(-17) M) was detected in solution. A theoretical model that allows the description of obtained experimental data, is proposed. This model takes into consideration both the transport of the protein from the bulk solution onto the AFM-chip surface and its irreversible binding to the activated area.

[Oligomeric state investigation of flavocytochrome CYP102A1 using AFM with standard and supersharp probes].

Atomic force microscopy with two types of probes - standard (radius of curvature R approximately 10 nm) and supersharp (R approximately 2 nm)- was used to determine CYP102A1oligomeric state. CYP102A1 images were obtained in a liquid, air and vacuum environment using the standard probes, also a ratio of monomers to oligomers (alpha) of CYP102A1 were determined as alpha=0.48:0.52. At the same time use of standard probes did not allow to resolve the structure of these oligomers. Supersharp probes allowed to obtain the data about the monomers to oligomers ratio, and also about the dimers/trimers/tetramers ratio in air and vacuum. So, a ratio alpha of CYP102A1 in liquid can be determined by the standard probes, and an oligomeric state of protein can be specified by the supersharp probes.

[Atomic force microscopy visualization and measurement of the activity and physicochemical properties of single monomeric and oligomeric enzymes].

An approach to measure the activity of single oligomers of the heme-containing enzyme the cytochrome P450 CYP102A1 (CYP102A1) by atomic force microscopy (AFM) has been developed. It was found that the amplitude of fluctuations of the height of single CYP102A1 molecules performing the catalytic cycle is twice as great as the amplitude of fluctuations of the height of the same enzymes in the inactive state. It was shown that the amplitude of height fluctuations of a CYP102A1 protein globule depends on temperature, the maximum of this dependence being observed at 22 degrees C. The activity of a single CYP102A1 molecule in the unit amplitude of height fluctuations of a protein globule reduced to the unit time was 5+/-2 Ac. The elasticity of a single protein molecule was measured from the deformation of this molecule by the action of an AFM probe. The use of AFM probes of different geometry made i t possible t o determine t he integral andlocal Young's modulus for the monomers of the protein putidaredoxin reductase from the cytochrome P450 CYP101 (P450cam)-containing monooxigenase system, which were 37+/-117 and 1+/-3 MPa, respectively.

[Visualization and identification of hepatitis C viral particles by atomic force microscopy combined with MS/MS analysis].

Possibility of detection and identification of hepatitis C viral particles with mass spectrometry (MS) in combination with atomic force microscopy (AFM) had been investigated. AFM/MS approach is based on two technologies: (1) AFM-biospecific fishing that allows to detect, concentrate from solution and to count protein complexes on a surface of AFM-nanochip; (2) mass spectrometric identification of these complexes. AFM-biospecific fishing of HCVcoreAg from solution was carried onto surface of AFM-nanochips with immobilized anti-HCVcoreAg. It was shown that HCVcoreAg/anti-HCVcore(im) complexes were formed onto AFM-nanochips in quantity sufficient for mass spectrometric identification. Thus, AFM/MS approach allows to identify fragments of hepatitis C virus fished onto a surface of AFM-nanochip from serum.

[Atomic force microscopy detection of serological markers of viral hepatites B and C].

The aim of the study was to demonstrate the possibility of detection of serological markers, containing the hepatitis B surface antigen (HBsAg) and hepatitis C virus core-antigen (HCVcoreAg) in human serum, by use of a new atomic force microscopy (AFM)-based nanotechnological approach. In this study, the immobilization on AFM-chip of antibodies against the hepatitis B virus surface antigen (anti-HBsAg) as well as the antibodies against the hepatitis C virus core antigen (anti-HCVcoreAg) was performed. It was shown that such approach enables to detect: HBsAg, HCVcoreAg and the viral fragments containing these antigens in the serum. Comparative analysis of detection of HBsAg- and HCVcoreAg-containing particles by use of the AFM method vs. traditional methods (ELISA, PCR) has demonstrated the 75% coincidence of results between the AFM and the latter two methods.