The 2'-5' RNA Ligase of Escherichia coli: Purification, Cloning, and Genomic Disruption

An RNA ligase previously detected in extracts of Escherichia coli is capable of joining Saccharomyces cerevisiae tRNA splicing intermediates in the absence of ATP to form a 2-5 phosphodiester linkage (Greer, C., Javor, B., and Abelson, J. (1983) Cell 33, 899-906). This enzyme specifically ligates tRNA half-molecules containing nucleoside base modifications and shows a preference among different tRNA species. In order to investigate the function of this enzyme in RNA metabolism, the ligase was purified to homogeneity from E. coli lysate utilizing chromatographic techniques and separation of proteins by SDS-polyacrylamide gel electrophoresis. A single polypeptide of approximately 20 kilodaltons exhibited RNA ligase activity. The amino terminus of this protein was sequenced, and the open reading frame (ORF) encoding it was identified by a data base search. This ORF, which encodes a novel protein with a predicted molecular mass of 19.9 kDa, was amplified from E. coli genomic DNA and cloned. ORFs coding for highly similar proteins were detected in Methanococcus jannaschii and Bacillus stearothermophilus. The chromosomal gene encoding RNA ligase in E. coli was disrupted, abolishing ligase activity in cell lysates. Cells lacking ligase activity grew normally under laboratory conditions. However, moderate overexpression of the ligase protein led to slower growth rates and a temperature-sensitive phenotype in both wild-type and RNA ligase knockout strains. The RNA ligase reaction was studied in vitro using purified enzyme and was found to be reversible, indicating that this enzyme may perform cleavage or ligation in vivo

Why bayesian “evidence for H1” in one condition and bayesian “evidence for H0” in another condition does not mean good-enough bayesian evidence for a difference between the conditions

Psychologists are often interested in whether an independent variable has a different effect in condition A than in condition B. To test such a question, one needs to directly compare the effect of that variable in the two conditions (i.e., test the interaction). Yet many researchers tend to stop when they find a significant test in one condition and a nonsignificant test in the other condition, deeming this as sufficient evidence for a difference between the two conditions. In this Tutorial, we aim to raise awareness of this inferential mistake when Bayes factors are used with conventional cutoffs to draw conclusions. For instance, some researchers might falsely conclude that there must be good-enough evidence for the interaction if they find good-enough Bayesian evidence for the alternative hypothesis, H1, in condition A and good-enough Bayesian evidence for the null hypothesis, H0, in condition B. The case study we introduce highlights that ignoring the test of the interaction can lead to unjustified conclusions and demonstrates that the principle that any assertion about the existence of an interaction necessitates the direct comparison of the conditions is as true for Bayesian as it is for frequentist statistics. We provide an R script of the analyses of the case study and a Shiny app that can be used with a 2 × 2 design to develop intuitions on this issue, and we introduce a rule of thumb with which one can estimate the sample size one might need to have a well-powered design

Low-frequency electronic noise in superlattice and random-packed thin films of colloidal quantum dots

We report measurements of low-frequency electronic noise in ordered superlattice, weakly-ordered and random-packed thin films of 6.5 nm PbSe quantum dots prepared using several different ligand chemistries. For all samples, the normalized noise spectral density of the dark current revealed a Lorentzian component, reminiscent of the generation-recombination noise, superimposed on the 1/f background (f is the frequency). An activation energy of 0.3 eV was extracted from the temperature dependence of the noise spectra. The noise level in the ordered films was lower than that in the weakly-ordered and random-packed films. A large variation in the magnitude of the noise spectral density was also observed in samples with different ligand treatments. The obtained results are important for application of colloidal quantum dot films in photodetectors.Comment: 24 pages, 6 figures and supplemental inf

An engineered Tetrahymena tRNA(Gln) for in vivo incorporation of unnatural amino acids into proteins by nonsense suppression

A new tRNA, THG73, has been designed and evaluated as a vehicle for incorporating unnatural amino acids site-specifically into proteins expressed in vivo using the stop codon suppression technique. The construct is a modification of tRNAGln(CUA) from Tetrahymena thermophila, which naturally recognizes the stop codon UAG. Using electrophysiological studies of mutations at several sites of the nicotinic acetylcholine receptor, it is established that THG73 represents a major improvement over previous nonsense suppressors both in terms of efficiency and fidelity of unnatural amino acid incorporation. Compared with a previous tRNA used for in vivo suppression, THG73 is as much as 100-fold less likely to be acylated by endogenous synthetases of the Xenopus oocyte. This effectively eliminates a major concern of the in vivo suppression methodology, the undesirable incorporation of natural amino acids at the suppression site. In addition, THG73 is 4-10-fold more efficient at incorporating unnatural amino acids in the oocyte system. Taken together, these two advances should greatly expand the range of applicability of the in vivo nonsense suppression methodology

Factors Influencing Real Estate Brokerage Sales Staff Performance

This research examined factors that affect residential real estate sales staff performance from sixteen firms of various sizes in different residential markets. The human capital model was related to sales staff commission earnings. A psychological factors model and management systems model were introduced that explained variance beyond that accounted for by the human capital model. Multiple regression analysis demonstrated that five of the twenty-seven variables examined accounted for most of the statistically significant variance. These variables included gender, hours worked per week, amount of formal education, work satisfaction, and reputation of the firm. Suggestions on how to utilize the findings regarding those variables related to earnings, as well as those not related, are briefly discussed.

Upgrading Marine Ecosystem Restoration Using Ecological-Social Concepts

Conservation and environmental management are principal countermeasures to the degradation of marine ecosystems and their services. However, in many cases, current practices are insufficient to reverse ecosystem declines. We suggest that restoration ecology, the science underlying the concepts and tools needed to restore ecosystems, must be recognized as an integral element for marine conservation and environmental management. Marine restoration ecology is a young scientific discipline, often with gaps between its application and the supporting science. Bridging these gaps is essential to using restoration as an effective management tool and reversing the decline of marine ecosystems and their services. Ecological restoration should address objectives that include improved ecosystem services, and it therefore should encompass social ecological elements rather than focusing solely on ecological parameters. We recommend using existing management frameworks to identify clear restoration targets, to apply quantitative tools for assessment, and to make the re-establishment of ecosystem services a criterion for success

Marginalized Populations’ Access to Transit: Journeys from Home and Work to Transit

Previous scholarship has shown that low-income individuals who also might identify as racial, ethnic, and gender minorities (such as transgender and gender nonconforming) are more likely to be dependent on public transportation. What remains understudied is how these marginalized groups, given their intersectional identities of oppression, might experience transit. The primary research question guiding this project is how do people with intersecting marginal identities experience social exclusion as they travel via mass transit? To answer the above research question, we employed a photovoice methodology and video-call interviewing, in Portland, OR, and Salt Lake City, UT. Across these two sites we interviewed 35 BIPOC (Black, Indigenous and other People of Color) with an income level less than $35,000 per person per year or$70,000 per family per year who use transit regularly, who were ethnically diverse, and included immigrants and people with other marginalized identities. In the interviews we found that people from these historically marginalized communities experience economic barriers, discrimination, harassment, and violence on transit and in public areas such as sidewalks, bus stops, and transit platforms when accessing transit related to their intersecting identities (e.g., being a woman of color). We examined how to make transit more accessible; for example, transit passes for low-income individuals, higher frequency of buses, lighting in dark areas, Spanish messaging in stations and on buses, to mention a few. We found that transit workers were key to feelings of safety by marginalized riders, where they could create a sense of welcome and community and fairly and consistently support policies that facilitated access for all. In addition, technology could be a mechanism for safety and ease of travel, but also widen socioeconomic gaps. Our findings are a starting point about what not only Salt Lake City and Portland planners, policymakers, social service providers, and case managers can do, but also what other municipalities could expect in terms of improving transportation and services for these vulnerable populations

Setting Priorities for Space Research: Opportunities and Imperatives

This report represents the first phase of a study by a task group convened by the Space Studies Board to ascertain whether it should attempt to develop a methodology for recommending priorities among the various initiatives in space research (that is, scientific activities concerned with phenomena in space or utilizing observations from space). The report argues that such priority statements by the space research community are both necessary and desirable and would contribute to the formulation and implementation of public policy. The report advocates the establishment of priorities to enhance effective management of the nation's scientific research program in space. It argues that scientific objectives and purposes should determine how and under what circumstances scientific research should be done. The report does not take a position on the controversy between advocates of manned space exploration and those who favor the exclusive use of unmanned space vehicles. Nor does the report address questions about the value or appropriateness of Space Station Freedom or proposals to establish a permanent manned Moon base or to undertake a manned mission to Mars. These issues lie beyond the charge to the task group

The ideal healthcare: priorities of people with chronic conditions and their carers

Background It is well established that health consumer opinions should be considered in the design, delivery, and evaluation of health services. However, the opinions of people with chronic conditions and their carers and what they actually consider as ideal healthcare is limited. The aim of this study is to investigate the healthcare priorities of consumers with chronic conditions and their carers, if there are differences between these two groups, and if priorities differ depending on geographical location. Methods The nominal group technique was used as a method to identify what is currently important to, or valued by, participants. This method was also particularly suited to learning about healthcare problems and generating important solutions, thereby helping to bridge the gap between research and policy. Recruitment was carried out via purposive sampling, with the assistance of community pharmacies, general practices, various health agencies, government and non-government organisations. A total of 11 nominal groups were conducted; five groups consisted predominantly of consumers (n = 33 participants), two groups consisted predominantly of carers (n = 12 participants) and four were mixed groups, i.e. consumers, carers, and both (n = 26 participants). Results The findings suggested that to create a model of ideal healthcare for people with chronic conditions and their carers, appropriate and timely healthcare access was of paramount importance. Continuity and coordinated care, patient-centred care and affordability were equally the second most important healthcare priorities for all groups. When compared with other groups, access was discussed more frequently among participants residing in the rural area of Mount Isa. Compared to consumers, carers also discussed priorities that were more reminiscent with their caring roles, such as increased access and continuity and coordinated care. Conclusions Access to healthcare is the most important priority for people with chronic conditions and their carers. In the event of inappropriate access for certain groups, all other efforts to increase the quality of healthcare delivery, e.g. patient-centred care, may be pointless. However, health professionals alone may be limited in their ability to address the concerns related to healthcare access; structural changes by health policy makers may be needed