A New Colorimetric Assay for Methionyl Aminopeptidases: Examination of the Binding of a New Class of Pseudopeptide Analog Inhibitors

A direct and convenient spectrophotometric assay has been developed for methionine aminopeptidases (MetAPs). The method employs the hydrolysis of a substrate that is a methionyl analogue of p-nitroaniline (l-Met-p-NA), which releases the chromogenic product p-nitroaniline. This chromogenic product can be monitored continuously using a UV–Vis spectrophotometer set at 405 nm. The assay was tested with the type I MetAP from Escherichia coli (EcMetAP-I) and the type II MetAP from Pyrococcus furiosus (PfMetAP-II). Using l-Met-p-NA, the kinetic constants kcat and Km were determined for EcMetAP-I and PfMetAP-II and were compared with those obtained with a “standard” high-performance liquid chromatography (HPLC) discontinuous assay. The assay has also been used to determine the temperature dependence of the kinetic constant kcat for PfMetAP-II as well as to screen two novel pseudopeptide inhibitors of MetAPs. The results demonstrate that l-Met-p-NA provides a fast, convenient, and effective substrate for both type I and type II MetAPs and that this substrate can be used to quickly screen inhibitors of MetAPs

Nuclear charge radii of light isotopes based on frequency comb measurements

Optical frequency comb technology has been used in this work for the first time to investigate the nuclear structure of light radioactive isotopes. Therefore, three laser systems were stabilized with different techniques to accurately known optical frequencies and used in two specialized experiments. Absolute transition frequency measurements of lithium and beryllium isotopes were performed with accuracy on the order of 10^(−10). Such a high accuracy is required for the light elements since the nuclear volume effect has only a 10^(−9) contribution to the total transition frequency. For beryllium, the isotope shift was determined with an accuracy that is sufficient to extract information about the proton distribution inside the nucleus. A Doppler-free two-photon spectroscopy on the stable lithium isotopes (6,7)^Li was performed in order to determine the absolute frequency of the 2S → 3S transition. The achieved relative accuracy of 2×10^(−10) is improved by one order of magnitude compared to previous measurements. The results provide an opportunity to determine the nuclear charge radius of the stable and short-lived isotopes in a pure optical way but this requires an improvement of the theoretical calculations by two orders of magnitude. The second experiment presented here was performed at ISOLDE/CERN, where the absolute transition frequencies of the D1 and D2 lines in beryllium ions for the isotopes (7,9,10,11)^Be were measured with an accuracy of about 1 MHz. Therefore, an advanced collinear laser spectroscopy technique involving two counter-propagating frequency-stabilized laser beams with a known absolute frequency was developed. The extracted isotope shifts were combined with recent accurate mass shift calculations and the root-mean square nuclear charge radii of (7,10)^Be and the one-neutron halo nucleus 11^Be were determined. Obtained charge radii are decreasing from 7^Be to 10^Be and increasing again for 11^Be. While the monotone decrease can be explained by a nucleon clustering inside the nucleus, the pronounced increase between 10^Be and 11^Be can be interpreted as a combination of two contributions: the center-of-mass motion of the 10^Be core and a change of intrinsic structure of the core. To disentangle these two contributions, the results from nuclear reaction measurements were used and indicate that the center-of-mass motion is the dominant effect. Additionally, the splitting isotope shift, i.e. the difference in the isotope shifts between the D1 and D2 fine structure transitions, was determined. This shows a good consistency with the theoretical calculations and provides a valuable check of the beryllium experiment

Continuous dialysis of citric acid: Solubility and diffusivity in Neosepta-AMH membrane

The transport of citric acid through an anion-exchange membrane Neosepta-AMH in a two-compartment continuous dialyzer has been investigated. The basic data obtained were completed by the measurement of the sorption isotherm. Mass transfer rate has been quantified by diffusivity of citric acid in the membrane, which has been determined from the acid concentrations in the streams entering and leaving the dialyzer. For that purpose, a set of ordinary differential equations describing the concentrations profiles in both the compartments of the dialyzer has been numerically solved in the connection with an optimizing procedure. In the mathematical model used, mass transfer resistances in liquid films on both sides of the membrane have been taken into account. All the experiments carried out at steady state (temperature 25 °C) revealed that first diffusivity of citric acid in the Neosepta-AMH membrane gradually increases with an increasing acid concentration until reaching a weak maximum at an acid concentration of c = 0.464 kmol m–3, then it slightly decreases. In the concentration range of citric acid in the membrane from 0 to 0.558 kmol m–3, diffusivity of acid was in the limits from 1.79 ×10–12 to 3.33 ×10–12 m2 s–1

Continuous dialysis of citric acid: Solubility and diffusivity in Neosepta-AMH membrane

The transport of citric acid through an anion-exchange membrane Neosepta-AMH in a two-compartment continuous dialyzer has been investigated. The basic data obtained were completed by the measurement of the sorption isotherm. Mass transfer rate has been quantified by diffusivity of citric acid in the membrane, which has been determined from the acid concentrations in the streams entering and leaving the dialyzer. For that purpose, a set of ordinary differential equations describing the concentrations profiles in both the compartments of the dialyzer has been numerically solved in the connection with an optimizing procedure. In the mathematical model used, mass transfer resistances in liquid films on both sides of the membrane have been taken into account. All the experiments carried out at steady state (temperature 25 °C) revealed that first diffusivity of citric acid in the Neosepta-AMH membrane gradually increases with an increasing acid concentration until reaching a weak maximum at an acid concentration of c = 0.464 kmol m–3, then it slightly decreases. In the concentration range of citric acid in the membrane from 0 to 0.558 kmol m–3, diffusivity of acid was in the limits from 1.79 ×10–12 to 3.33 ×10–12 m2 s–1

A first course in feedback, dynamics and control: findings from an online pilot survey for the IFAC community

Undergraduate students in many engineering programs around the world take only one control course. The IFAC Educational Committee has developed and piloted to a limited audience a comprehensive survey for the topics to be included in such course. This issue is relevant to both academia and industry. The paper discusses the initial findings related to the design of the survey as well as the responses of the participants. The findings will be used to refine the survey and distribute it in the near future to the global control community

Cryopreservation of Human Gametes and Embryos: Current State and Future Perspectives

Cryopreservation of human gametes and embryos is an important and widely used method in most embryology laboratories. During last years, the practice of single embryo transfer was a greater demand for reliable cryostorage of surplus embryos. Currently, there are two basic principally different methods usable for cryopreservation: slow freezing and vitrification. Vitrification is a very promising method with massive use in embryology. Nowadays, this method is also suitable for cryopreservation of human mature oocytes (one of the most problematic cell in cryobiology). This progress in the field of cryopreservation opens new perspectives in assisted reproduction. Recent effective oocyte vitrification systems have a significant impact on clinical practice. This chapter gives a view of human gametes (sperms, oocytes) and embryos cryopreservation application and possibilities. Indications and methods of cryopreservation and thawing are mentioned

Technical committee on control education

Presents information of the CS society Presents information of the CS society Technical Committee on Control Education

A survey of international views on a first course in systems and control for engineering undergraduates

This paper summarises the results of an international survey of academics and industrialists on what should be prioritised in the first, and often only, control course taken by engineering undergraduates. The results are made up both of quantitative data whereby respondents selected from a number of options, and also of qualitative data where respondents entered free comments. Reflections on the results and summaries of common trends are given to help readers consider how the curriculum in their own institutions might be updated and modified to meet modern requirements. At the time of writing the survey had around 500 respondents covering a good spread of nationalities, employment status and engineering disciplines

The relationship between structure and in vitro antistaphylococcal effect of plant-derived stilbenes

Staphylococcus aureus is a major human pathogen that is responsible for both hospital- and community-acquired infections. Stilbenes are polyphenol compounds of plant origin known to possess a variety of pharmacological properties, such as antibacterial, antiviral, and antifungal effects. This study reports the in vitro growth-inhibitory potential of eight naturally occurring stilbenes against six standard strains and two clinical isolates of S. aureus, using a broth microdilution method, and expressing the results as minimum inhibitory concentrations (MICs). Pterostilbene (MICs = 32–128 μg/ml), piceatannol (MICs = 64–256 μg/ml), and pinostilbene (MICs = 128 μg/ml) are among the active compounds that possess the strongest activity against all microorganisms tested, followed by 3′-hydroxypterostilbene, isorhapontigenin, oxyresveratrol, and rhapontigenin with MICs 128–256 μg/ml. Resveratrol (MIC = 256 μg/ml) exhibited only weak inhibitory effect. Furthermore, structure–activity relationships were studied. Hydroxyl groups at ortho-position (B-3′ and -4′) played crucial roles for the inhibitory effect of hydroxystilbene piceatannol. Compounds with methoxy groups at ring A (3′-hydroxypterostilbene, pinostilbene, and pterostilbene) produced stronger effect against S. aureus than their analogues (isorhapontigenin and rhapontigenin) with methoxy groups at ring B. These findings provide arguments for further investigation of stilbenes as prospective leading structures for development of novel antistaphylococcal agents for topical treatment of skin infections