PubMed Health⌕ Search

Biomedical subjects

D V Klinov

Publications and source records attributed to D V Klinov.

6 recordsLinked to original sources
PubMed2001

Proximity-induced superconductivity in DNA.

Conductivity measurements on double-stranded DNA molecules deposited by a combing process across a submicron slit between rhenium/carbon metallic contacts reveal conduction to be ohmic between room temperature and 1 kelvin. The resistance per molecule is less than 100 kilohm and varies weakly with temperature. Below the superconducting transition temperature (1 kelvin) of the contacts, proximity-induced superconductivity is observed. These results imply that DNA molecules can be conducting down to millikelvin temperature and that phase coherence is maintained over several hundred nanometers.

DNA↗
PubMed2001

RNA-binding properties of the 63 kDa protein encoded by the triple gene block of poa semilatent hordeivirus.

The 63 kDa '63K' movement protein encoded by the triple gene block of poa semilatent virus (PSLV) comprises the C-terminal NTPase/helicase domain and the N-terminal extension domain, which contains two positively charged sequence motifs, A and B. In this study, the in vitro RNA-binding properties of PSLV 63K and its mutants were analysed. Membrane-immobilized 63K and N-63K (isolated N-terminal extension domain) bound RNA at high NaCl concentrations. In contrast, C-63K (isolated NTPase/helicase domain) was able to bind RNA only at NaCl concentrations of up to 50 mM. In gel-shift assays, C-63K bound RNA to form complexes that were unable to enter an agarose gel, whereas complexes formed by N-63K could enter the gel. Full-length 63K formed both types of complexes. Visualization of the RNA-protein complexes formed by 63K, N-63K and C-63K by atomic force microscopy demonstrated that each complex had a different shape. Collectively, these data indicate that 63K has two distinct RNA-binding activities associated with the NTPase/helicase domain and the N-terminal extension domain. Mutations in either of the positively charged sequence motifs A and B had little effect on the RNA binding of the N-terminal extension domain, whereas mutations in both motifs together inhibited RNA binding. Hybrid viruses with mutations in motifs A and B were able to infect inoculated leaves of Nicotiana benthamiana plants, but were unable to move systemically to uninoculated leaves, suggesting that the RNA-binding activity of the N-terminal extension domain of PSLV 63K is associated with virus long-distance movement.

Amino Acid Sequence↗
PubMed2000

Atomic force and electron microscopy of high molecular weight circular DNA complexes with synthetic oligopeptide trivaline.

Intramolecular compact structures formed by high molecular weight circular superhelical DNA molecules due to interaction with synthetic oligopeptide trivaline (1) were studied by atomic force and electron microscopy. Three DNA preparations were used: plasmids pTbol, pRX10 and cosmid 27,877, with sizes 6,120 bp, 10,500 bp and 44,890 bp respectively. Plasmid pTbo1 and pRX10 preparations along with monomers contained significant amount of dimers and trimers. Main structures in all preparations observed were compact particles, which coincide in their appearance and compaction coefficient (3,5-3,7) with triple rings described earlier. The size and structure characteristics of triple rings and other compact particles on atomic force images in general coincide with those obtained by EM (2). AFM (3) images allow to get additional information about the ultrastructural organization and arrangement of DNA fibers within the compact structures. Along with triple rings in pTbol and pRX10-TVP complexes significant amount of compact structures were observed having the shape of two or three compact rings attached to each other by a region of compact fibre. Basing on the data of contour length measurements and the shape of the particles it was concluded that these structures were formed due to compaction of dimeric and trimeric circular DNA molecules. Structures consisting of several attached to each other triple rings were not found for pTbol, pRX10 monomers or cosmid preparations--TVP complexes where only single triple rings were observed. The conclusion is made that initiation of compact fibre formation within the circular molecules depends on the primary structure and for dimeric or trimeric circular molecules two or three compaction initiation points are present, located in each monomer unit within one circular DNA molecule. The nucleotide sequence dependent compaction mechanism providing independent compaction of portions of one circular molecule can be of interest for understanding of DNA compaction processes in vivo.

Cosmids↗
PubMed1998

High resolution mapping DNAs by R-loop atomic force microscopy.

R-loops formed by short RNA transcripts have been imaged by atomic force microscopy (AFM) at a constant force in the height mode. The technique was applied to mapping the human endogenous retrovirus K10 family (HERV-K10) long terminal repeats (LTR) within individual plasmids and cosmids. RNA probes specific for the U3 (384 nt) and U5 (375 nt) LTR regions separated by a span of 200 bp were used for R-loop formation with LTRs located within plasmid (3.8 kb) or cosmid ( approximately 40 kb) DNAs. R-loops stabilized by glyoxal treatment and adsorbed onto the mica surface in the presence of magnesium ions looked like looped out segments of RNA:DNA hybrids. The total yield of R-loops was usually approximately 95%. The RNA:DNA hybrids were found to be 12-15% shorter than the corresponding DNA:DNA duplex. The two regions of the LTR could be easily discerned in the AFM images as clearly separated loops. R-loop positions determined on cosmids by AFM were accurate to approximately 0.5% of the cosmid length. This technique might be easily adapted for mapping various sequences such as gene exons or regulatory regions and for detecting insertions, deletions and rearrangements that cause human genetic diseases.

Cosmids↗
PubMed1995

[Nonchemical methods of modifying substrates for studying biopolymers with atomic force microscopy].

Two simple procedures of DNA molecule fixation on mica for following imaging by the atomic force microscopy were developed. The distinctive features of the procedures are their simplicity, absence of chemical modification stages, and the possibility to obtain the images in air under relative high humidity. Comparison of the features of the images obtained indicated that the procedures developed were competitive with the procedures earlier suggested.

Aluminum Silicates↗