Tyrosine, Cysteine, and S-Adenosyl Methionine Stimulate In Vitro [FeFe] Hydrogenase Activation

Background: [FeFe] hydrogenases are metalloenzymes involved in the anaerobic metabolism of H2. These proteins are distinguished by an active site cofactor known as the H-cluster. This unique [6Fe–6S] complex contains multiple non-protein moieties and requires several maturation enzymes for its assembly. The pathways and biochemical precursors for H-cluster biosynthesis have yet to be elucidated. Principal Findings: We report an in vitro maturation system in which, for the first time, chemical additives enhance [FeFe] hydrogenase activation, thus signifying in situ H-cluster biosynthesis. The maturation system is comprised of purified hydrogenase apoprotein; a dialyzed Escherichia coli cell lysate containing heterologous HydE, HydF, and HydG maturases; and exogenous small molecules. Following anaerobic incubation of the Chlamydomonas reinhardtii HydA1 apohydrogenase with S-adenosyl methionine (SAM), cysteine, tyrosine, iron, sulfide, and the non-purified maturases, hydrogenase activity increased 5-fold relative to incubations without the exogenous substrates. No conditions were identified in which addition of guanosine triphosphate (GTP) improved hydrogenase maturation. Significance: The in vitro system allows for direct investigation of [FeFe] hydrogenase activation. This work also provides a foundation for studying the biosynthetic mechanisms of H-cluster biosynthesis using solely purified enzymes and chemical additives

The Methodology of the Multi-site Study of the Termination of Supplemental Security Income Benefits for Drug Addicts and Alcoholics

This paper describes the quantitative and qualitative methodologies used in a nine-site, two-year study of the effects of terminating Supplemental Security Income (SSI) for drug addiction and alcoholism (DA&A). The quantitative component of the study involved a longitudinal survey that collected data on 1,744 former DA&A recipients, representing about one-fourth of the national population, and achieved an aggregate follow-up rate of 82%. Despite limitations in questionnaire design and implementation, the survey provided reasonably valid data in the following areas: demographics, employment/income, medical/psychiatric status, drug and alcohol use, legal involvement, family/social functioning, food and hunger, housing, and victimization. The qualitative component examined the lives of a subsample to help clarify important issues that could not be addressed within the more structured protocol and format of the longitudinal survey. The paper also presents details on the survey instrument design, the results of validation studies of selected survey items, and data collection protocols across study sites

The Methodology of the Multi-site Study of the Termination of Supplemental Security Income Benefits for Drug Addicts and Alcoholics

This paper describes the quantitative and qualitative methodologies used in a nine-site, two-year study of the effects of terminating Supplemental Security Income (SSI) for drug addiction and alcoholism (DA&A). The quantitative component of the study involved a longitudinal survey that collected data on 1,744 former DA&A recipients, representing about one-fourth of the national population, and achieved an aggregate follow-up rate of 82%. Despite limitations in questionnaire design and implementation, the survey provided reasonably valid data in the following areas: demographics, employment/income, medical/psychiatric status, drug and alcohol use, legal involvement, family/social functioning, food and hunger, housing, and victimization. The qualitative component examined the lives of a subsample to help clarify important issues that could not be addressed within the more structured protocol and format of the longitudinal survey. The paper also presents details on the survey instrument design, the results of validation studies of selected survey items, and data collection protocols across study sites

Termination of Supplemental Security Income Benefits for Drug Addiction and Alcoholism: Results of a Longitudinal Study of the Effects on Former Beneficiaries

This article reviews the results of a multisite cohort study on effects of terminating Supplemental Security Income benefits for drug addiction and alcoholism. Within 2 years of the program\u27s termination, 35 - 43 percent of participants requalified for disability benefits for another impairment. Regardless of requalification status, substance abuse treatment participation declined sharply and illegal drug use was prevalent. Although many of those who did not requalify lost income, medical benefits, and housing, these losses lessened over time and were not associated with increased psychological or medical problems or with declines in other aspects of participants\u27 lives

Termination of Supplemental Security Income Benefits for Drug Addiction and Alcoholism: Results of a Longitudinal Study of the Effects on Former Beneficiaries

This article reviews the results of a multisite cohort study on effects of terminating Supplemental Security Income benefits for drug addiction and alcoholism. Within 2 years of the program\u27s termination, 35 - 43 percent of participants requalified for disability benefits for another impairment. Regardless of requalification status, substance abuse treatment participation declined sharply and illegal drug use was prevalent. Although many of those who did not requalify lost income, medical benefits, and housing, these losses lessened over time and were not associated with increased psychological or medical problems or with declines in other aspects of participants\u27 lives

Drug Treatment Participation and Retention Rates among Former Recipients of Supplemental Security Income for Drug Addiction and Alcoholism

This study examined drug treatment participation and retention rates for a multisite sample of 1,586 former recipients of Supplemental Security Income (SSI) for drug addiction and alcoholism (DA&A). Fewer than half of the sample were complying with the DA&A program treatment mandate at the time the program was terminated by federal legislation in January 1997. For all forms of treatment, both participation and retention rates declined steadily thereafter until fewer than 10% of the total sample reported being in a formal treatment two years after termination of the mandate. Survival analyses comparing treatment retention rates for DA&A beneficiaries with non-DA&A SSI beneficiaries revealed that most of the decline in treatment retention could be attributed to ending the mandate. The findings suggest that although the mandate was often not well enforced, it did bring into drug treatment many individuals who would not otherwise have participated

Substance Abuse and Welfare Policy at the New Century

Drawing on findings from the SSI Study and other research, this paper takes up various policy questions fundamental to any welfare program for substance abusers. The paper considers the place of disability benefits in the U.S. system of categorical aid and the problems raised by substance abuse for the disability category. It discusses the desirable objectives of a welfare program for substance abusers and the various mechanisms by which they might be achieved. And finally, it considers how any new program might be positioned in the context of categorical aid and American federalism

Drug Treatment Participation and Retention Rates among Former Recipients of Supplemental Security Income for Drug Addiction and Alcoholism

This study examined drug treatment participation and retention rates for a multisite sample of 1,586 former recipients of Supplemental Security Income (SSI) for drug addiction and alcoholism (DA&A). Fewer than half of the sample were complying with the DA&A program treatment mandate at the time the program was terminated by federal legislation in January 1997. For all forms of treatment, both participation and retention rates declined steadily thereafter until fewer than 10% of the total sample reported being in a formal treatment two years after termination of the mandate. Survival analyses comparing treatment retention rates for DA&A beneficiaries with non-DA&A SSI beneficiaries revealed that most of the decline in treatment retention could be attributed to ending the mandate. The findings suggest that although the mandate was often not well enforced, it did bring into drug treatment many individuals who would not otherwise have participated

Substance Abuse and Welfare Policy at the New Century

Drawing on findings from the SSI Study and other research, this paper takes up various policy questions fundamental to any welfare program for substance abusers. The paper considers the place of disability benefits in the U.S. system of categorical aid and the problems raised by substance abuse for the disability category. It discusses the desirable objectives of a welfare program for substance abusers and the various mechanisms by which they might be achieved. And finally, it considers how any new program might be positioned in the context of categorical aid and American federalism