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1 May 2006

Volume 99, Issue 9, Articles (09xxxx)

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Enhancement of cancer chemotherapy in vitro by intense ultrawideband electric field pulses

David W. Jordan, Michael D. Uhler, Ronald M. Gilgenbach, and Y. Y. Lau

J. Appl. Phys. 99, 094701 (2006); http://dx.doi.org/10.1063/1.2194115 (4 pages) | Cited 4 times

Online Publication Date: 12 May 2006

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Experiments have been performed to enhance the Jurkat cell-killing effects of the cancer chemotherapy agent bleomycin using electric field pulses of 50–200 kV/cm peak electric field strength, ∼ 150 ns duration, and nanosecond rise time. Dramatic increases in cell killing (factors of ∼ 1000) were observed with a low dose of bleomycin after treatment with trains of ten or more pulses at all electric field strengths tested, compared to pulse-only or drug-only treatments. Cell death occurred within 24 h for treated cells, with some evidence of membrane phosphatidylserine externalization at 6 h postexposure but no significant increase in caspase activity, indicating that the primary mode of cell death was not caspase-mediated apoptosis.
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87.80.-y Biophysical techniques (research methods)
87.19.X- Diseases
87.16.D- Membranes, bilayers, and vesicles
87.14.E- Proteins
87.50.C- Static and low-frequency electric and magnetic fields effects

In situ observation of DNA hybridization and denaturation by surface infrared spectroscopy

Ko-Ichiro Miyamoto, Ken-Ichi Ishibashi, Ryo-Taro Yamaguchi, Yasuo Kimura, Hisao Ishii, and Michio Niwano

J. Appl. Phys. 99, 094702 (2006); http://dx.doi.org/10.1063/1.2188128 (7 pages) | Cited 11 times

Online Publication Date: 15 May 2006

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We have investigated in situ the hybridization and denaturation of DNA in aqueous solution using infrared absorption spectroscopy (IRAS) in the multiple internal reflection (MIR) geometry. We demonstrate that conformational changes of DNA strands due to hybridization (binding of two complementary single-stranded DNAs) and denaturation (separation of double helix at elevated temperatures) are reflected in the infrared absorption spectra in the frequency region where vibrational modes of the bases of DNA appear. Comparison with results of ab initio cluster calculation shows that hybridization produces the specific CO carbonyl stretching vibration modes in the hydrogen-bonded base pairs. The ratio of absorbance of the CO stretching peak at 1690 cm−1 to the absorbance at 1660 cm−1 provides a definitive metric for determining DNA hybridization. We also reveal that the CO stretching vibration modes of the bases of a single strand is strongly influenced by the surrounding water molecules that may interact with the CO groups of the bases. The present results suggest that MIR-IRAS is applicable to label-free, high-sensitive biosensors that provide insight about the gene expression and a variety of biological interactions such as DNA-protein interactions.
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87.64.K- Spectroscopy
87.14.G- Nucleic acids
87.15.M- Spectra of biomolecules
87.15.H- Dynamics of biomolecules
87.15.K- Molecular interactions; membrane-protein interactions
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
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