Characterization of Mg2+ binding to the DNA repair protein apurinic/apyrimidic endonuclease 1 via solid-state 25Mg NMR spectroscopy.

Apurinic/apyrimidinic endonuclease 1 (APE1), a member of the divalent cation-dependent phosphoesterase superfamily of proteins that retain the conserved four-layered alpha/beta-sandwich structural core, is an essential protein that functions as part of base excision repair to remove mutagenic and cytotoxic abasic sites from DNA. Using low-temperature solid-state (25)Mg NMR spectroscopy and various mutants of APE1, we demonstrate that Mg(2+) binds to APE1 and a functional APE1-substrate DNA complex with an overall stoichiometry of one Mg(2+) per mole of APE1 as predicted by the X-ray work of Tainer and co-workers (Mol, C. D.; Kuo, C. F.; Thayer, M. M.; Cunningham, R. P.; Tainer, J. A. Nature 1995, 374 , 381-386). However, the NMR spectra show that the single Mg(2+) site is disordered. We discuss the probable reasons for the disorder at the Mg(2+) binding site. The most likely source of this disorder is arrangement of the protein-ligands about the Mg(2+) (cis and trans isomers). The existence of these isomers reinforces the notion of the plasticity of the metal binding site within APE1.

Robotic telesurgery: a real-world comparison of ground- and satellite-based internet performance.

BACKGROUND: Telesurgery was performed with ground vs. satellite networks, and differing satellite bandwidths. METHODS: The networks were compared during internal mammary artery (LIMA) dissection in pigs (n = 8). Length of LIMA dissected and surgical quality (five-point scale) were recorded. Also, satellite bandwidth was decreased (n = 7) to determine a limit for telesurgery. RESULTS: No significant differences existed in LIMA dissection during the ground (4.3 +/- 0.5 cm) and satellite phases (5.4 +/- 1.1 cm; p > 0.05) or in quality of surgery, although latency on satellite was 10 times greater (55 vs. 600 ms). With decreasing satellite bandwidth, surgery was not possible below 3 Mb/s, and quality of surgery was significantly decreased comparing 9 Mb/s (4.38 +/- 0.66/5) to 3 Mb/s (4.10 +/- 0.80/5; p < 0.05). CONCLUSIONS: Satellite communication is a viable telesurgical modality. Satellite bandwidth should be above 5 Mb/s during telesurgery if used primarily or as back-up.

Long-distance robotic telesurgery: a feasibility study for care in remote environments.

BACKGROUND: Basic telesurgical manoeuvres were conducted with signal delays. METHODS: Eight test subjects conducted four manoeuvres. Time delays of 0-1000 ms were investigated. Time to task completion and error rate were recorded in sequential delays of 0-600 ms. Additionally, blinded random delays of 0-1000 ms were studied. RESULTS: In the sequential trials (0-600 ms), there were no significant differences in average task time compared to zero latency. The error rate remained low despite increasing time delay, and was significantly less at 500 ms (p < 0.05). In the random trials, task time was significantly greater at delays of 500, 600, 800 and 1000 ms (p < 0.05). There were no significant differences in error rates (p = 0.252). CONCLUSIONS: Operators are capable of performing surgical exercises at significant delays. Latent video feedback is difficult for telesurgery. Visual or virtual reality cues should be implemented to aid the operator in a high-cadence telesurgery environment.

Chain segment order in ultrathin polymer films: a deuterium NMR study.

The orientational order of monomerically thin films of polydimethylsiloxane melt deposited on the surfaces of cylindrical pores is investigated in this paper by solid-state deuterium nuclear magnetic resonance. Spectra demonstrate substantial orientation of the methyl groups by the surface. The quadrupolar splitting of the oriented film component saturates below one monomer layer, but decreases stepwise for thicker films. Comparisons of experimental and simulated spectra suggest a flat chain conformation in the first polymer monolayer.

Markov models of non-Gaussian exponentially correlated processes and their applications.

We consider three different methods of generating non-Gaussian Markov processes with given probability density functions and exponential correlation functions. All models are based on stochastic differential equations. A number of analytically treatable examples are considered. The results obtained can be used in different areas such as telecommunications and neurobiology.

Generation of compound non-gaussian random processes with a given correlation function

A compound representation of random processes is considered. Each independent component of such a process is considered as the solution of the proper stochastic differential equation (SDE). This guarantees that the process obtained is stationary and ergodic. The analytical expressions are developed for nonlinear coefficients of the generating SDE. Theoretical results are compared with numerical simulation.