PubMed Health⌕ Search

Biomedical subjects

A Rakitin

Publications and source records attributed to A Rakitin.

8 recordsLinked to original sources
PubMed2001

Metallic conduction through engineered DNA: DNA nanoelectronic building blocks.

A novel way of engineering DNA molecules involves substituting the imino proton of each base pair with a metal ion to obtain M-DNA with altered electronic properties. We report the first direct evidence of metalliclike conduction through 15 microm long M-DNA. In contrast, measurements on B-DNA give evidence of semiconducting behavior with a few hundred meV band gap at room temperature. The drastic change of M-DNA conductivity points to a new degree of freedom in the development of future molecular electronics utilizing DNA, such as creating all-DNA junction devices for use as nanoelectronic building blocks.

Bacteriophage lambda↗
PubMed2000

Electronic transport in Y-junction carbon nanotubes

Electronic transport measurements were performed on Y-junction carbon nanotubes. These novel junctions contain a large diameter tube branched into smaller ones. Independent measurements using good quality contacts on both individual Y junctions and many in parallel show intrinsic nonlinear transport and reproducible rectifying behavior at room temperature. The results were modeled using classic interface physics for a junction with an abrupt change in band gap due to the change in tube diameter. These Y-junction tubes represent new heterojunctions for nanoelectronics.

Journal Article↗
PubMed1991

Habituation and sensitization to an electrical shock in the crab Chasmagnathus. Effect of background illumination.

The escape response of the crab Chasmagnathus granulatus, elicited by an electrical leg-shock, wanes as a consequence of repeated stimulation, and the decrease persists after a 24-h rest interval. Results concerning stimulus specificity in within- and between-sessions habituation strongly indicate that neither motor fatigue nor sensory adaptation nor damage can account for the response waning, which thus meets the major criteria of habituation. A comparison between the escape response habituation to leg-shock and that to a shadow passing overhead discloses clearcut differences. The shock curve shows an initial hump positively related to stimulus intensity, suggesting that a shock-induced sensitization along with habituation subserves the response curve. The curve asymptote is remarkably high and, unlike the initial waning portion, not greatly affected by treatment changes, hinting that the response may be the combination of an escape response and a basal one (an undirected burst of activity). The waning portion is higher when shocks are given in dark than when given in light, but this effect is not considered as an extra eliciting-stimulus-induced sensitization, since the reactivity enhancement depends necessarily on the darkness-shock concomitance, regardless of prior exposure to darkness. Accordingly, the hypothesis that crab habituates not only to a shock but to a complex stimulus (shock + background illumination) is put forward and discussed.

Animals↗
PubMed1991

Morphine and GABA: effects on perception, escape response and long-term habituation to a danger stimulus in the crab Chasmagnathus.

Prior results (37) showed that morphine pretreatment reduces the escape response of the crab Chasmagnathus to a shadow passing overhead and prevents the acquisition of a long-term habituation. These results were explained by a reduction in the danger signalled by the stimulus, and to test this hypothesis methods other than morphine injection were used herein to abolish response during training. GABA pretreatment induced a dose-dependent reduction in responsiveness to the danger stimulus, and instances of autotomy were shown with doses larger than 12 micrograms/g. A response was rarely displayed with a 9 micrograms GABA/g dose given 5 min before training, but long-term memory was acquired. In one experiment, both morphine and GABA pretreatment produced similar mild response inhibition during training, but morphine, not GABA impaired long-term habituation. Morphine administered immediately after training had no amnesic effect. These results support the hypothesis that morphine effects may be explained by transient disruption between the stimulus and its danger meaning, ruling out alternative explanations such as response inhibition or amnesia due to either storage or retrieval failure.

Animals↗