Electron Transfer Precedes ATP Hydrolysis during Nitrogenase Catalysis

The biological reduction of N2 to NH3 catalyzed by Mo-dependent nitrogenase requires at least eight rounds of a complex cycle of events associated with ATP-driven electron transfer (ET) from the Fe protein to the catalytic MoFe protein, with each ET coupled to the hydrolysis of two ATP molecules. Although steps within this cycle have been studied for decades, the nature of the coupling between ATP hydrolysis and ET, in particular the order of ET and ATP hydrolysis, has been elusive. Here, we have measured first-order rate constants for each key step in the reaction sequence, including direct measurement of the ATP hydrolysis rate constant: kATP = 70 s−1, 25 °C. Comparison of the rate constants establishes that the reaction sequence involves four sequential steps: (i) conformationally gated ET (kET = 140 s−1, 25 °C), (ii) ATP hydrolysis (kATP = 70 s−1, 25 °C), (iii) Phosphate release (kPi = 16 s−1, 25 °C), and (iv) Fe protein dissociation from the MoFe protein (kdiss = 6 s−1, 25 °C). These findings allow completion of the thermodynamic cycle undergone by the Fe protein, showing that the energy of ATP binding and protein–protein association drive ET, with subsequent ATP hydrolysis and Pi release causing dissociation of the complex between the Feox(ADP)2 protein and the reduced MoFe protein

Getting Jobs, Keeping Jobs, and Earning a Living Wage: Can Welfare Reform Work?

Most discussions of welfare and work have focused on how demographic characteristics, schooling, training, and work experience limit welfare mothers’ employment and wages, but they have largely ignored factors such as inappropriate workplace behaviors, expectations of discrimination and harassment, depression, alcoholism, and domestic violence, all of which may affect welfare mothers and make employment difficult. In this paper we review the prevalence of these individual-level barriers and argue that they, in combination with an economy which does not pay low-skill workers well, are likely to impede employment and self-sufficiency for a large proportion of welfare mothers. At the end of the review, we summarize the current state of knowledge about barriers to the employment of welfare recipients and suggest several ways in which welfare-to-work programs might address these barriers.

Barriers to the Employment of Welfare Recipients

Dramatic reductions in welfare caseloads since passage of the Personal Responsibility and WorkOpportunity Reconciliation Act of 1996 have not allayed policy concerns about the employability of recipients remaining on the rolls. Analysis of potential barriers to employment can address whether current recipients have problems that either singly or in combination make it difficult for them to comply with the new requirements for getting and keeping jobs. In this paper, we explore the prevalence and work effects of 14 potential barriers in a new survey of a representative sample of 753 urban single-mother recipients. We report the prevalence of the barriers and how their number predicts employment rates, controlling for demographic characteristics. We also analyze which individual barriers are associated with employment and how a model inclusive of a comprehensive array of barriers improves upon a traditional human capital model of the work effects of education and work and welfare history. Single mothers who received welfare in 1997 had higher rates of personal health and mental health problems, domestic violence, and children’s health problems than do women in national samples, but they were no more likely than the general population to be drug or alcohol dependent. Only 15 percent of respondents had none of the barriers and almost two-thirds had two or more barriers. The numbers of multiple barriers were strongly and negatively associated with working, and among the individual barriers, low education, lack of access to transportation, poor health, having drug dependence or a major depressive disorder, and several experiences of workplace discrimination reduced employment. Welfare-to-work programs need to be more finely targeted with respect to exemptions and service provision, and states should consider providing longer-term and enhanced supports for those who face low prospects of leaving welfare for employment.

UPPER BODY SEGMENT LENGTHS AS A PROPORTION OF HEIGHT IN CHILDREN

Most research studies in biomechanics directly measure body segment lengths via anthropometry or digitization of joint markers. There are circumstances in which estimating segment lengths in relation to height is desirable, such as in biomechanical modelling or in the classroom. One commonly used model for this purpose is that by Drillis and Contini (1966; cited in Winter, 2005). One problem with this model is that the initial data was derived from adults, and thus has potentially limited applicability to the study of biomechanics in children. The purpose of the present study was to compare actual selected upper body segment lengths measured via anthropometry to those predicted by Drillis and Contini and also to derive regression equations for those segment lengths based on height and age (separately for males and females)

We Know Better Than We Do: A Policy Framework for Child Welfare Reform

The need for comprehensive reform of child welfare policies and systems has long been evident. This Article reports observations from the WK Kellogg Foundation-sponsored Families for Kids Initiative that seeks to expand services and support to families and reduce the time children spend in temporary care. The authors first provide an overview of the need for reforms such as those proposed by this initiative, suggesting that many child welfare studies, critiques, and proposed reforms have had similar objectives. The authors highlight lessons learned from how these reform goals are being developed, implemented, and practiced in ongoing programs across the nation and argue that change at multiple levels must occur for reform of this system to succeed. They identify nine methods being used to varying degrees by some of these initiatives to institutionalize reform goals and improve the quality and outcomes of child welfare legal and social service practice. By highlighting these evolving models of state law, agency administrative procedure and professional practice, the authors identify areas of reform for other jurisdictions. Child welfare reform rests upon new legislation mandates; more specific reasonable efforts requirements, adoption of flexible funding mechanisms, capitated foster care contracts, timely court processes better trained professional or cross-system data capability to monitor children in care. All of these policy and system reforms must be designed and implemented collectively for child welfare ideals to become operational

Negative Cooperativity in the Nitrogenase Fe Protein Electron Delivery Cycle

Nitrogenase catalyzes the ATP-dependent reduction of dinitrogen (N2) to two ammonia (NH3) molecules through the participation of its two protein components, the MoFe and Fe proteins. Electron transfer (ET) from the Fe protein to the catalytic MoFe protein involves a series of synchronized events requiring the transient association of one Fe protein with each αβ half of the α2β2 MoFe protein. This process is referred to as the Fe protein cycle and includes binding of two ATP to an Fe protein, association of an Fe protein with the MoFe protein, ET from the Fe protein to the MoFe protein, hydrolysis of the two ATP to two ADP and two Pi for each ET, Pi release, and dissociation of oxidized Fe protein-(ADP)2 from the MoFe protein. Because the MoFe protein tetramer has two separate αβ active units, it participates in two distinct Fe protein cycles. Quantitative kinetic measurements of ET, ATP hydrolysis, and Pi release during the presteady-state phase of electron delivery demonstrate that the two halves of the ternary complex between the MoFe protein and two reduced Fe protein-(ATP)2 do not undergo the Fe protein cycle independently. Instead, the data are globally fit with a two-branch negative-cooperativity kinetic model in which ET in one-half of the complex partially suppresses this process in the other. A possible mechanism for communication between the two halves of the nitrogenase complex is suggested by normal-mode calculations showing correlated and anticorrelated motions between the two halves

Less-healthy eating behaviors have a greater association with a high level of sugar-sweetened beverage consumption among rural adults than among urban adults

Background: Sugar-sweetened beverage (SSB) consumption is associated with the increasing prevalence of overweight and obesity in the United States; however, little is known about how less-healthy eating behaviors influence high levels of SSB consumption among rural adults. Objective: We assessed the frequency of SSB consumption among rural and urban adults, examined the correlates of frequent SSB consumption, and determined difference in correlates between rural and urban adults in a large region of Texas. Design: A cross-sectional study using data on 1,878 adult participants (urban = 734 and rural = 1,144), who were recruited by random digit dialing to participate in the seven-county 2006 Brazos Valley Community Health Assessment. Data included demographic characteristics, eating behaviors (SSB consumption, frequency of fast-food meals, frequency of breakfast meals, and daily fruit and vegetable intake), and household food insecurity. Results: The prevalence of any consumption of SSB and the prevalence of high consumption of SSB were significantly higher among rural adults compared with urban counterparts. The multivariable logistic regression models indicated that a high level of SSB consumption (≥3 cans or glasses SSB/day) was associated with demographic characteristics (poverty-level income and children in the home), frequent consumption of fast-food meals, infrequent breakfast meals, low fruit and vegetable intake, and household food insecurity especially among rural adults. Conclusions: This study provides impetus for understanding associations among multiple eating behaviors, especially among economically and geographically disadvantaged adults. New strategies are needed for educating consumers, not only about how to moderate their SSB intake, but also how to simultaneously disrupt the co-occurrence of undesirable eating and promote healthful eating

Argonne National Laboratory Reports

The reliability of stainless steel type 304L canisters for the containment of solidified high-level radioactive wastes in the glass and calcine forms was studied. A reference system, drawn largely from information furnished by Battelle Northwest Laboratories and Atlantic Richfield Hanford Company is described. Operations include filling the canister with the appropriate waste form, interim storage at a reprocessing plant, shipment in water to a Retrievable Surface Storage Facility (RSSF), interim storage at the RSSF, and shipment to a final disposal facility

An Examination of Sport Participation Tracking and Adult Physical Activity for Participants of the Michigan State University Motor Performance Study

Research tracking sport participation from youth to adulthood is relatively rare, as is research that tracks youth sport participation with regard to adult physical activity (PA) levels, especially in the United States. Aims of this study were: 1) To investigate the degree to which sport participation tracked across youth, adolescence, and early adulthood in a sample of participants from the Michigan State University Motor Performance Study (MPS), and 2) Determine if differences existed in their levels of adult PA relative to prior sport participation. In total, 256 (60.8%) former participants from the MPS completed follow-up surveys regarding routine sport participation and PA across the previous year. Sport participation tracked consistently from youth to college. Further, regardless of the level of youth sport participation, adult leisure time PA was relatively consistent among groups. Although the study did not directly test the influence of the MPS on subsequent adult outcomes, our findings suggest that participants’ past sport participation was not a good predictor of adult PA for those who were involved in a program that emphasized fundamental motor skills in youth. Further investigation of such programs can help to better inform their influence on adult PA