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Efficient enzymatic synthesis of 13 C,15N-labeled DNA for NMR studies (1997)

Smith, Deborah E. ; Su, Jin-Yuan ; Jucker, Fiona M.

Springer

Journal of biomolecular NMR 10 (1997), S. 245-253

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ISSN: 1573-5001

Keywords: DNA ; DNA–protein complex ; Deoxythymidylate kinase ; Enzymatic synthesis ; Heteronuclear NMR ; Isotope labeling

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology

Notes: Abstract The power of heteronuclear NMR spectroscopy to study macromoleculesand their complexes has been amply demonstrated over the last decade. Theobstacle to routinely applying these techniques to the study of DNA has beenthe synthesis of 13C,15N-labeled DNA. Here wepresent a simple and efficient method to generate isotope-labeled DNA forNMR studies that is as easy as that for isotope labeling of RNA. The methodwas used to synthesize a uniformly13 C,15N-labeled 32-nucleotide DNA that binds tohuman basic fibroblast growth factor with high affinity and specificity.Isotope-edited experiments were applied to the13 C,15N-labeled DNA bound to unlabeled protein,and the 13 C,15N-labeled DNA was also examined incomplex with 15N-labeled protein. The NMR experiments showthat the DNA adopts a well-defined stable structure when bound to theprotein, and illustrate the potential of13 C,15N-labeled DNA for structural studies ofDNA–protein complexes.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1018358602001

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A frequency-dependent finite-difference time-domain formulation for induced current calculations in human beings (1992)

Gandhi, Om P. ; Gao, Ben-Qing ; Chen, Jin-Yuan

New York, NY [u.a.] : Wiley-Blackwell

Bioelectromagnetics 13 (1992), S. 543-555

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ISSN: 0197-8462

Keywords: broadband irradiation ; short pulses ; tissue dispersion ; induced currents ; SARs ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Physics

Notes: The finite-difference time-domain (FDTD) method has been used to calculate SARs and induced currents involving whole-body or partial-body exposures of models to spatially uniform or nonuniform (far-field or near-field), to sinusoidally varying EM fields, or to transient fields such as those associated with electromagnetic pulses. However, a weakness of the FDTD algorithm is that the dispersion of the tissue's dielectric properties is ignored and frequency-independent properties are assumed. Although this is permissible for continuous-wave or narrow-band irradiation, the results may be highly erroneous for short pulses, in which ultra-wide bandwidths are involved. In some recent publications, procedures are described for one- and two-dimensional problems for media in which the complex permittivity ∊ * (ω) may be described by a single-order Debye relaxation equation or a modified version thereof. These procedures based on a convolution integral describing D(t) in terms of E(t) cannot be extended to human tissues for which multiterm Debye relaxation equations must generally be used.We describe here a new differential-equation approach that can be used for general dispersive media. We illustrate the use of this approach by one- and three-dimensional examples of media for which ∊ * (ω) is given by a multiterm Debye equation, and for an approximate two-thirds muscle-equivalent model of the human body. Based on a single run involving a Gaussian pulse, the frequency-dependent FDTD [(FD)2TD] method allows calculations of SARs and induced currents at various frequencies by taking the Fourier components of the induced E fields. The (FD)2TD method can also be used to calculate coupling of the short (ultra-wideband) pulses to the human body. 1992 Wiley-Liss, Inc.

Additional Material: 8 Ill.