A hydrophobic to hydrophilic gradient surface was prepared using the tuned photodegradation of an alkylsilane self-assembled monolayer (SAM) using irradiation of vacuum ultraviolet light (wavelength=172 nm). The water contact angle on the photodegraded SAM surface was adjusted using the intensity and time photoirradiation parameters. The formation of a gradient was confirmed by fluorescent labeling. The water drop moved from the hydrophobic to hydrophilic surface with a velocity that depended on the gradient. The higher the gradient, the faster the water moved. For the first time, we have prepared a gradient surface using photodegradation where the movement of a water drop was regulated by the degree of gradation. Considering that the photodegradation technique can be applied to various surfaces and to lithography, this technique will be useful for various material surfaces.

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Radiation-induced free radical formation in the amino acid l-R-alanine has been studied using powder and single-crystal X-, K-, and Q-band electron paramagnetic resonance (EPR) spectroscopy, X-band powder electron-nuclear double resonance (ENDOR), thermal annealing, and EPR spectrum simulations. The spectra obtained after room temperature irradiations are composite, consisting of resonances from mainly three radicals denoted R1, R2, and R3. R1 is the well-known, stable room-temperature species formed by deamination from a protonated alanine anion radical. On the basis of simulations of EPR spectra obtained at X-, K-, and Q-bands, the room-temperature EPR spectrum seems to consist of about 55% of R1. Upon thermal annealing, the R1 resonance disappears faster than those of the other two components. The R2 species is presumably formed in the oxidative chain of radiation-induced events by net H-abstraction from the central alanine carbon atom. Q-band EPR was used to determine the g-tensor of R2. This species contributes about 35% to the resonance recorded at room temperature. Upon thermal annealing this radical decays slower than R1, resulting in the predominance of R2 in spectra obtained after prolonged warming at 480 K. Powder ENDOR was used to verify that the dominating species remaining after thermal annealing at this temperature indeed is R2 and not a successor species of either of the room-temperature radicals. The R3 species was previously assigned to an N-deprotonated version of R2 being additionally protonated at the carboxyl group. Detailed spectral data for this resonance are missing but a set of parameters based on available data and otherwise estimated using literature values for similar products was constructed. Simulations indicated that 5-10% of the roomtemperature resonance could be ascribed to R3. R3 is more heat-resistant than the R1 and R2 radicals, and after prolonged annealing at 480K it was estimated that the resulting resonance consisted of about 51% R2 and 43% R3. The remaining part (about 6%) of the resonance was due to R1. These numbers must, however, be considered as tentative because of the lack of precise spectral data for R3.

The amino acid l-alpha-alanine has attracted considerable interest for use in radiation dosimetry and has been formally accepted as a secondary standard for high-dose and transfer dosimetry. Recent results have shown that the alanine EPR spectrum consists of contributions from three different radicals. A set of benchmark spectra describing the essential spectral features of these three radical components was used for reconstructions of the experimental spectra. In the present work, these basis spectra have been used to investigate the differential effects of variations in radiation doses and microwave power, as well as the dependence upon temperature annealing and UV illumination. The results presented here, based solely on relatively low-energy (60-80 keV) X rays, indicate that the three components behave very similarly with respect to radiation dose at room temperature. However, with respect to the thermal annealing/fading behavior and microwave power saturation properties, the three species behave significantly differently. It is concluded that even if it is now realized that three different radicals contribute to the composite EPR alanine spectrum, this has a minor impact on the established protocols for present-day applications (high-dose) of EPR/alanine dosimetry. However, some care should be exercised when e.g. constructing calibration curves, since fading and power saturation behavior may vary over the dose range in question. New results from UV-illumination experiments suggest a possible procedure for experimental spectral separation of the EPR signals due to the three radicals.

L-Lysine dehydrogenase, which catalyzes the oxidative deamination of L-lysine in the presence of NAD, was found in the thermophilic bacterium Geobacillus stearothermophilus UTB 1103 and then purified about 3,040-fold from a crude extract of the organism by using four successive column chromatography steps. This is the first report showing the presence of a thermophilic NAD-dependent lysine dehydrogenase. The product of the enzyme catalytic activity was determined to be ⌬ 1 -piperideine-6-carboxylate, indicating that the enzyme is L-lysine 6-dehydrogenase (LysDH) (EC 1.4.1.18). The molecular mass of the purified protein was about 260 kDa, and the molecule was determined to be a homohexamer with subunit molecular mass of about 43 kDa. The optimum pH and temperature for the catalytic activity of the enzyme were about 10.1 and 70°C, respectively.

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