A perspective on cold enzymes: current knowledge and frequently asked questions.

Studies on psychrophilic enzymes to determine the structural features important for cold-activity have attracted increased attention in the last few years. This enhanced interest is due to the attractive properties of such proteins, i.e. a high specific activity and a low thermal stability, and thus, these enzymes constitute a tremendous potential for fundamental research and biotechnological applications. This review examines the impact of low temperatures on life, the diversity of adaptation to counteract these effects and gives an overview of the features proposed to account for low thermal stability and cold-activity, following the chronological order of the catalytic cycle phases. Moreover, we present an overview of recent techniques used in the analysis of the flexibility of a protein structure which is an important concept in cold-adaptation; an overview of biotechnological potential of psychrophilic enzymes and finally, a few frequently asked questions about cold-adaptation and their possible answers.

Optically stimulated luminescent glass optical fibre dosemeter.

An optical fibre radiation dosemeter has been developed that utilises optically stimulated luminescence and scintillation to provide independent, remote, real-time dose measurements. The radiation sensitive element consists of a 1 mm long, 0.4 mm diameter piece of copper-ion-doped fused quartz that is attached to a 1 m length of commercial optical fibre. The dosemeter probe is 0.6 mm in diameter and is flexible enough to be used in standard medical catheters for internal radiation dose measurements. A four-channel dosemeter system has been built and characterised under conditions typical of a radiotherapy environment. The device exhibits a linear response over the range of doses from 0.01 Gy to 10 Gy. The dosemeter responds identically to both electrons and photons in the range from 4 to 20 MV and the calibration was retained to within +/-2% over a period of 4 weeks. The fibre dosemeter has been used successfully to verity doses received by three patients receiving radiotherapy treatments.

Remarkably low temperature optima for extracellular enzyme activity from Arctic bacteria and sea ice.

Extracellular degradative enzymes released by psychrophilic marine bacteria (growing optimally at or below 15 degrees C and maximally at 20 degrees C) typically express activity optima at temperatures well above the upper growth limit of the producing strain. In the present study, we investigated whether or not near-zero Arctic environments contain extracellular enzymes with activity optimized to temperatures lower than previously reported. By applying fluorescently tagged substrate analogues to measure leucine-aminopeptidase and chitobiase activity, the occurrence of extracellular enzymatic activity (EEA) with remarkably low temperature optima (15 degrees C) was documented in sea-ice samples. An extremely psychrophilic bacterial isolate, strain 34H, yielded an extract of cell-free protease with activity optimized at 20 degrees C, the lowest optimum yet reported for cell-free EEA from a pure culture. The use of zymogram gels revealed the presence of three proteolytic bands (between 37 and 45 kDa) in the extract and the release of the greatest quantities of the proteases when the strain was grown at -1 degrees C, suggesting a bacterial strategy for counteracting the effects of very cold temperatures on the catalytic efficiency of released enzymes. The detection of unusually cold-adapted EEA in environmental samples has ramifications not only to polar ecosystems and carbon cycling but also to protein evolution, biotechnology and bioremediation.

Anti-homosexual attitudes in college students: predictors and classroom interventions.

Undergraduate college students (N = 173) enrolled in business or psychology classes were studied to investigate (1) predictors of anti-gay and lesbian attitudes and (2) two educational approaches for counteracting negative attitudes toward homosexuality. Students' gender and other demographic characteristics, gender role orientation, gender role attitudes, and personal history variables were employed as independent variables in a multiple regression analysis to predict anti-homosexual attitudes. Results indicated that attitudes were significantly predicted by gender role attitudes, personal acquaintance with a gay man, lesbian, or bisexual person, and religious conviction. Gender, gender role orientation, age, prior participation in a workshop on homosexuality, sexual experience, and class type (psychology or business) were not significant predictors. One-way independent groups analysis of variance indicated no significant differences in level of anti-homosexual attitudes between heterosexual students who had interacted with gay and lesbian students in a one hour classroom panel discussion, viewed a video presentation on homosexuality, or had no classroom intervention.

Thermal-defocusing/scattering optical limiter.

Operation of an f/5 thermal-defocusing/scattering optical limiter is described. Thermal-defocusing limiting of 6-ns-duration, 532-nm laser pulses occurs by use of the broadband-absorbing dye Nigrosin dissolved in carbon disulfide. Additional limiting due to thermally induced scattering occurs at high incident fluences (above a threshold fluence) when either surface-roughened BASF-1 glass windows are in contact with the dye solution or microscopic glass fibers are added to the liquid cell. Limiter figures of merit are improved by factors of 2 and 4, respectively, over that of a purely thermal-defocusing limiter.

Frequency-offset, solid-state laser coherent Doppler velocity measurements of high-speed targets.

Diode-pumped, single-frequency Nd:YAG lasers were used to measure velocities of laser-accelerated targets over a range of 0.1 to greater than 2 km/sec. A 1-GHz optical heterodyne receiver was used with a tunable, frequencyoffset local oscillator to compensate for Doppler shifts of as much as 4 GHz.

Nonlinear Mie scattering: electrostrictive coupling of light to droplet acoustic modes.

Nonlinear Mie scattering at 532 nm was observed from 23-microm-diameter ethanol droplets excited by picosecond light pulses. Low-order optical modes (l = 2-4), normally hidden at low intensity, became visible as new peaks in elastic scattering spectra at 2 GW/cm(2). When higher-Q resonances were selectively excited, the scattered light showed an amplitude-modulated time dependence. The data are explained by electrostrictive generation of acoustic modes of the droplet by the incident radiation and subsequent coupling of the acoustic disturbance back onto the light field.

Some characteristics of a droplet whispering-gallery-mode laser.

We report lasing characteristics of 40-60-microm-diameter Rhodamine 590/water solution droplets pumped by a 20-nsec-duration Q-switched laser. The Rhodamine/water solution provides a useful model system for studying the properties of oscillators based on whispering-gallery-wave spherical cavities. The low threshold for lasing, 10(4) W/cm(2) for 10(-4) M solutions, is consistent with particle size and a cavity Q factor of 10(4). Portions of the droplet lase purely in transverse electric (TE) modes, while other portions contain both TE and lower-Q transverse magnetic modes. In the far field, the lasing droplet approximates a coherent point source emitting in all directions.

Preorgasmic group treatment: assertiveness, marital adjustment and sexual function in women.

Five measures were used in this study to assess preorgasmic group treatment: Gambill-Richey Assertiveness Scale, Dyadic Adjustment Scale, Sexual Arousal Inventory, Survey of Sexual Activity, and General Information Questionnaire. The total sample (N = 70) was made up of two groups: a control group of 32 women and a treatment group of 38 women who had completed preorgasmic group treatment. Analysis of the data showed that the treatment group women were having orgasms more frequently, had developed significantly more positive feelings about themselves, and established better communication with their partners. In assertiveness, the treatment group was somewhat higher, while no significant differences were found on the Dyadic Adjustment Scale. Of most significance for future research was the finding of increased sexual arousal for treatment group women.