Conformational stability of muscle acylphosphatase: the role of temperature, denaturant concentration, and pH

The conformational stability (delta G) of muscle acylphosphatase, a small alpha/beta globular protein, has been determined as a function of temperature, urea concentration, and pH. A combination of thermally induced and urea-induced unfolding, monitored by far-UV circular dichroism, was used to define the conformational stability over a wide range of temperature. Through analysis of all these data, the heat capacity change upon unfolding (delta Cp) could be estimated, allowing the determination of the temperature dependence of the main thermodynamic functions (delta G, delta H, delta S). Thermal unfolding in the presence of urea made it possible to extend such thermodynamic analysis to examine these parameters as a function of urea concentration. The results indicate that acylphosphatase is a relatively unstable protein with a delta G(H2O) of 22 +/- 1 kJ mol-1 at pH 7 and 25 degrees C. The midpoints of both thermal and chemical denaturation are also relatively low. Urea denaturation curves over the pH range 2-12 have allowed the pH dependence of delta G to be determined and indicate that the maximum stability of the protein occurs near pH 5.5. While the dependence of delta G on urea (the m value) does not vary with temperature, a significant increase has been found at low pH values, suggesting that the overall dimensions of the unfolded state are significantly affected by the number of charges within the polypeptide chain. The comparison of these data with those from other small proteins indicates that the pattern of conformational stability is defined by individual sequences and not by the overall structural fold.     

The development of epistemological beliefs among secondary students: A longitudinal study.

This article is the continuation of M. Schommer's (1993) study, in which the development of secondary students' beliefs about the nature of knowledge and learning, or epistemological beliefs, was examined. High school students (N?=?69) completed an epistemological questionnaire as freshmen in 1992 and as seniors in 1995. Repeated-measures analyses revealed that their beliefs in fixed ability to learn, simple knowledge, quick learning, and certain knowledge changed as they neared the end of their 4th year in high school. In addition, the less students believed in quick learning, the better grade point average they earned. These results are consistent with a cross-sectional study (M. Schommer, 1993) establishing substantial differences in students' epistemological beliefs across the high school years and thus strengthen the case that there is development of epistemological beliefs related to learning during high school. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Eye movements induced by lateral acceleration steps. Effect of visual context and acceleration levels

Different extracellular matrix (ECM) molecules, when presented to hippocampal neurons in culture in a substrate-bound form, exert strikingly similar effects on the establishment of neuronal polarity, i.e., the growth of axon-like major neurites is favored, whereas extension of dendrite-like minor neurites is inhibited. To gain insight into the underlying signal transduction processes, we have investigated the effects of modulators of protein kinase activity on the morphology of neurons cultured on tenascin-R, tenascin-C, and laminin-entactin substrates. We found differential effects of broad-spectrum protein kinase inhibitors: H-7 promoted the growth of minor neurites, whereas H-8 reduced the growth of major neurites on ECM but not control substrates. In contrast, chelerythrine, a specific inhibitor of protein kinase C, selectively affected growth of both minor and major neurites on control, but not on ECM substrates. Finally, reagents which elevate intracellular cAMP levels facilitated growth of minor neurites and inhibited growth of major neurites and thus interfered with the establishment of a polarized phenotype on both ECM and control substrates. Our results suggest that protein kinases mediate the effects of ECM molecules on neuronal polarity and that different kinases control extension of axons and dendrites.     

Short communication: reference values for blood parameters in Holstein dairy cows: effects of parity, stage of lactation, and season of production

Confidence intervals for blood parameters used for nutritional and metabolic profile testing in cattle were calculated for clinically normal lactating Holstein cows, taking into account the effects of parity, stage of lactation, and season. Blood samples were collected from 740 cows in 33 Italian dairy herds according to a predefined protocol. Herds were visited during summer and the following winter, sampling 12 lactating cows at each visit (4 primiparous and 8 multiparous). Six cows were selected from the early-lactation group (days in milk: 10 to 89) and the other 6 were selected from the mid-lactation group (days in milk: 90 to 215). Cow selection criteria excluded animals clinically exposed to periparturient diseases as well as animals not considered in good health by a veterinary clinical examination. For each blood variable, outliers were identified and discarded. Data were then analyzed for their Gaussian distribution and variables with not normal distribution were log-transformed to adjust for lack of normality. Herd mean values were calculated for each blood parameter according to 3 main classification factors: parity (primiparous vs. multiparous), stage of lactation (early vs. mid) and season of production (summer vs. winter). The resulting data set was statistically analyzed using a mixed model with the fixed effects of these factors, their interactions, and the random effect of herd. General 95% confidence intervals were calculated for blood variables that showed a relevant herd variance component such as albumin, triglycerides, aspartate, urea, glucose, alanine aminotransferase, lactate dehydrogenase, direct and total bilirubin, calcium, magnesium, and potassium. For the remaining parameters, specific confidence intervals were calculated for each level of the significant main factors. Parity affected blood concentration of total protein, globulin, creatinine, alkaline phosphatase, gamma glutamyl transferase, creatinine kinase, and phosphorus. Blood nonesterified fatty acids, aspartate aminotransferase, gamma glutamyl transferase, creatinine kinase and cholesterol were influenced by stage of lactation. The season of production had a significant effect on total protein, globulin, creatinine, alkaline phosphatase, phosphorus, sodium, and chlorine. The outcomes of this work will improve the accuracy of the biochemical profile as a tool for dairy practitioners to assess the metabolic status of lactating Holstein cows.     

Optical properties of metallic nanoparticles: manipulating light, heat and forces at the nanoscale

We present to a general readership an overview of the rich variety of phenomena and applications that arise from the interaction of metallic nanoparticles with light. First, we present the fundamental physics of localized surface plasmon resonances, the most relevant theories and numerical methods, as well as optical detection schemes. Finally, we explain how the localized surface plasmon resonances are currently exploited for the nanoscale manipulation of light, heat and forces in various applications and experimental investigations.     

From application service provision to service-oriented computing: A study of the IT outsourcing evolution

IT outsourcing is not a new concept. Originating from the early 60’s in the form of time sharing, IT outsourcing has evolved to the application service provision (ASP) model, in the late 90’s to pure services in the beginning of the century. Services, and their major representative web services, are actually the next phase of the movement toward Internet-based componentized software, known in the not so distant past as ASP. As the continuous expansion of the Internet and its relating technologies creates new marketing opportunities, traditional monolithic architectures are giving way to service-oriented computing (SOC), the architecture that enables service provision. SOC permits the utilization of large systems which are comprised of self-containing building blocks: services. Services may be made public, searched, reused and combined to form complex business processes while in the same time retaining a significant level of flexibility. Services and SOC have emerged as a response to a fundamental shift in enterprise business culture that started at the late 90’s. Although they are promising as an IT outsourcing enabler, many issues need to be dealt with before they can be considered suitable for wide adoption. These issues are of technological, business, economic and cultural nature and they were also faced by ASPs in the past. It is worth revisiting the successes and failures of the ASP model in order to get a better understanding of the evolving IT outsourcing industry. In this work, we describe the evolution of service provision from its initial form as software application, through the application service provision era and towards the new trend of web services.     

Remote Didactic Laboratory “G. Savastano,” The Italian Experience for E-Learning at the Technical Universities in the Field of Electrical and Electronic Measurements: Overview on Didactic Experiments

The Remote Didactic Laboratory Laboratorio Didattico Remoto - LA.DI.RE. ldquoG. Savastanordquo is the e-learning measurement laboratory supported by the Italian Ministry of Education and University. It involves about 20 Italian universities and provides students of electric and electronic measurement courses with access to remote measurement laboratories delivering different didactic activities related to measurement experiments. In order to demonstrate the versatility for didactic use, the overview of some experiments is given. The didactic experiments summarized in this paper concern measurement characterization of instruments and communication systems, measurement devices for remote laboratories, basic electrical measurements, magnetic measurements, electromagnetic-interference measurements, and signal processing for measurement applications.     

90dB‐DR 3.3V CMOS single‐ended‐to‐fully differential and fully differential‐to‐single‐ended amplifiers for audio applications

This paper presents the design and the realization of single‐ended‐to‐fully differential and fully differential‐to‐single‐ended amplifiers to be used in an audio signal processing system. The proposed blocks allow to reduce significantly the pin number of the developed system, while guaranteeing the high quality (16bit) performance required in an audio channel. The proposed circuits have been realized in a standard 3.3V 0.35 µm CMOS technology and achieve a Dynamic Range in excess of 90dB with a Total Harmonic Distortion lower than ‐80dB for a full scale signal amplitude. Their power consumption (≈6mW and each) and the area (0.1mm² each) are finally negligible with respect to the other blocks in the overall systems. Copyright © 2003 John Wiley & Sons, Ltd.     

A Contactless Inductive Velocity Reconstruction Method for Metallic and Semiconducting Melts

The knowledge of the flow in metallic and semiconducting melts is important for a number of industrial problems. Optical methods cannot be applied due to the opaqueness of those fluids. Ultrasonic methods have problems with wetting and thermal stability when applied in hot metallic melts. Evidently, contactless methods for velocity determination would be highly desirable. In some applications, even a coarse knowledge of the flow topology and the direction of the main eddies would be of high value. The study examines the possibility of velocity reconstruction in electrically conducting fluids from external measurements of different induced magnetic fields. It is shown that, for a reliable velocity reconstruction, the effect of the electric potential at the fluid boundary on the induced magnetic field should be taken into account.