ABSTRACT
We describe a transputer-based system suitable for accurate measurements of single-fiber electromyographic jitter. It consists of a conventional electromyograph, a home-made interface and a commercially available transputer-based board installed within a PC/AT compatible. Taking advantage of the concurrent operation of two transputer modules, the system features simultaneous data acquisition and statistical signal processing: while data are acquired and analyzed, a real-time visualization of the signal latency and its variability is provided. In the present configuration, the system can acquire and analyze up to 40,000 consecutive action potentials, which can be grouped into up to eight sets at different stimulation rates programmable up to 16 Hz. Since the determination of the electromyographic signal latency relies on least-squares smoothing and interpolation of the acquired data rather than on amplitude-threshold triggering, a low value (0.7 microsecond) of so called technical jitter is achieved. Computing power and memory can be easily extended by addition of transputer-based modules. Typical results of data acquisition and on-line analysis are reported.
Subject(s)
Diagnosis, Computer-Assisted/methods , Electromyography/methods , Microcomputers/statistics & numerical data , Signal Processing, Computer-Assisted/instrumentation , Diagnosis, Computer-Assisted/instrumentation , Electromyography/instrumentation , Evaluation Studies as Topic , Humans , SoftwareABSTRACT
The interaction energy and the structure of water molecules either inside the Gramicidin A transmembrane channel or at its two extremities is examined with the use of iso-energy maps and Monte Carlo simulations. The shape of the channel as experienced by water is analyzed in detail. Variations in the hydration structure due to the presence of a sodium ion placed at several positions along the channel are simulated, analyzed and discussed. Preliminary data on Li+ and K+ interacting with Gramicidin A and the system of water molecules are reported. The Gramicidin A atomic coordinates have been taken from Urry's recent papers (Urry, D.W. (1971) Proc. Natl. Acad. Sci. U.S.A. 68, 672-676 and Urry, D.W., Trapane, T.L. and Prasad, K.U. (1982) Int. J. Quant. Chem. Quant. Biol. Symp. 9, 31-40).
Subject(s)
Gramicidin , Ion Channels/physiology , Models, Biological , Models, Molecular , Protein Conformation , Thermodynamics , WaterABSTRACT
The interaction energy and the structure of water molecules either inside the Gramicidin A transmembrane channel or at its two extremities is examined with the use of iso-energy maps and Monte Carlo simulations. The shape of the channel as experienced by water is analyzed in detail. Variations in the hydration structure due to the presence of a Na+ ion placed at several positions along the channel are simulated, analyzed and discussed. Preliminary data on Li+ and K+ interacting with Gramicidin A and the system of water molecules are reported. The Gramicidin A atomic coordinates have been taken from Urry's recent papers.
Subject(s)
Gramicidin , Ion Channels , Computer Simulation , Molecular Structure , Monte Carlo Method , Thermodynamics , WaterABSTRACT
Thermodynamic interpretation of experiments with isotopically perturbed solvent supports the view that solvent stereodynamics is directly relevant to thermodynamic stability of biomolecules. According with the current understanding of the structure of the aqueous solvent, in any stereodynamic configuration of the latter, connectivity pathways are identifiable for their topologic and order properties. Perturbing the solvent by isotopic substitution or, e.g., by addition of co-solvents, can therefore be viewed as reinforcing or otherwise perturbing these topologic structures. This microscopic model readily visualizes thermodynamic interpretation. In conclusion, the topologic stereodynamic structures of connectivity pathways in the solvent, as modified by interaction with solutes, acquire a specific thermodynamic and biological significance, and the problem of thermodynamic and functional stability of biomolecules is seen in its full pertinent phase space.
Subject(s)
Molecular Conformation , Deuterium , Models, Chemical , Solvents , Stereoisomerism , ThermodynamicsSubject(s)
Oxygen/blood , Oxyhemoglobins/metabolism , Humans , Kinetics , Protein Conformation , SolventsSubject(s)
Alcohols/pharmacology , Galactosidases/metabolism , Liver/enzymology , beta-Galactosidase/metabolism , Animals , Cattle , KineticsABSTRACT
In the present work we studied the initial part of thermal denaturation curves of B. subtilis DNA in normal and heavy water, observing, by electron microscopy, the "opening" of DNA as a function of temperature. The results support the hypothesis that D(2)O plays a stabilizing role on strands separation during thermal denaturation of DNA.
Subject(s)
Bacillus subtilis/analysis , DNA, Bacterial , Binding Sites , DNA, Bacterial/isolation & purification , Deuterium , Hot Temperature , Microscopy, Electron , Nucleic Acid Denaturation , WaterABSTRACT
The repair of U.V. damages to DNA in B. subtilis cultures competent for genetic transformation has been studied. The comparison of survival curves for competent and non competent fractions shows that: i) excision repair is more effective in competent than in non competent bacteria; ii) recombination repair is more effective in non competent than in competent bacteria. These facts support the hypothesis that metabolic conditions and, very likely, DNA replication play a role in the regulation of the efficiency of the two different mechanisms of repair.