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1.
Metabolites ; 13(11)2023 Nov 19.
Artigo em Inglês | MEDLINE | ID: mdl-37999258

RESUMO

Newborn metabolite perturbations may identify potential biomarkers or mechanisms underlying adverse, smoking-related childhood health outcomes. We assessed associations between third-trimester smoking and newborn metabolite concentrations using the Tennessee Pregnancy Risk Assessment Monitoring System (PRAMS, 2009-2019) as the discovery cohort and INSPIRE (2012-2014) as the replication cohort. Children were linked to newborn screening metabolic data (33 metabolites). Third-trimester smoking was ascertained from birth certificates (PRAMS) and questionnaires (INSPIRE). Among 8600 and 1918 mother-child dyads in PRAMS and INSPIRE cohorts, 14% and 13% of women reported third-trimester smoking, respectively. Third-trimester smoking was associated with higher median concentrations of free carnitine (C0), glycine (GLY), and leucine (LEU) at birth (PRAMS: C0: adjusted fold change 1.11 [95% confidence interval (CI) 1.08, 1.14], GLY: 1.03 [95% CI 1.01, 1.04], LEU: 1.04 [95% CI 1.03, 1.06]; INSPIRE: C0: 1.08 [95% CI 1.02, 1.14], GLY: 1.05 [95% CI 1.01, 1.09], LEU: 1.05 [95% CI 1.01, 1.09]). Smoking cessation (vs. continued smoking) during pregnancy was associated with lower median metabolite concentrations, approaching levels observed in infants of non-smoking women. Findings suggest potential pathways underlying fetal metabolic programming due to in utero smoke exposure and a potential reversible relationship of cessation.

2.
PLoS One ; 18(10): e0287348, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37874824

RESUMO

BACKGROUND: Research on health effects and potential harms of electronic cigarette (EC) use during pregnancy is limited. We sought to determine the risks of pregnancy EC use on pregnancy-related adverse birth outcomes and assess whether quitting ECs reduces the risks. METHODS: Women with singleton live births who participated in the US Pregnancy Risk Assessment Monitoring System (PRAMS) survey study 2016-2020 were classified into four mutually exclusive groups, by their use of ECs and combustible cigarettes (CCs) during pregnancy: non-use, EC only use, CC only use, and dual use. We determined the risk of preterm birth, low birth weight, and small-for-gestational-age (SGA) by comparing cigarette users to non-users with a modified Poisson regression model adjusting for covariates. In a subset of women who all used ECs prior to pregnancy, we determined whether quitting EC use reduces the risk of preterm birth, low birth weight, and SGA by comparing to those who continued its use. All analyses were weighted to account for the PRAMS survey design and non-response rate. RESULTS: Of the 190,707 women (weighted N = 10,202,413) included, 92.1% reported cigarette non-use, 0.5% EC only use, 6.7% CC only use, and 0.7% dual use during pregnancy. Compared with non-use, EC only use was associated with a significantly increased risk of preterm birth (adjusted risk ratio [aRR]: 1.29, 95% confidence interval [CI]: 1.00, 1.65) and low birth weight (aRR: 1.38, 95%CI: 1.09, 1.75), but not SGA (aRR: 1.04, 95%CI: 0.76, 1.44). Among 7,877 (weighted N = 422,533) women EC users, quitting use was associated with a significantly reduced risk of low birth weight (aRR: 0.76, 95%CI: 0.62, 0.94) and SGA (aRR: 0.77, 95%CI: 0.62, 0.94) compared to those who continued to use ECs during pregnancy. CONCLUSIONS: Pregnancy EC use, by itself or dual use with CC, is associated with preterm birth and low birth weight. Quitting use reduces that risk. ECs should not be considered as a safe alternative nor a viable gestational smoking cessation strategy.


Assuntos
Sistemas Eletrônicos de Liberação de Nicotina , Nascimento Prematuro , Vaping , Gravidez , Recém-Nascido , Humanos , Feminino , Nascimento Prematuro/epidemiologia , Nascimento Prematuro/etiologia , Vaping/efeitos adversos , Estudos Transversais , Medição de Risco , Arritmias Cardíacas/complicações , Retardo do Crescimento Fetal
3.
J Womens Health (Larchmt) ; 32(10): 1052-1061, 2023 10.
Artigo em Inglês | MEDLINE | ID: mdl-37582216

RESUMO

Background: All pregnant women and those who may become pregnant are recommended by the Advisory Committee on Immunization Practices to receive the flu vaccine to prevent severe illness in the woman and infant. Despite the increased risk for complications in this population, flu vaccine uptake in pregnant women was 68.1% in the 2020-2021 flu season, with disparities by race and ethnicity. We sought to describe associations between provider recommendation with flu vaccine uptake by race and ethnicity in Tennessee women with a recent live birth. Materials and Methods: Weighted analysis used data from the 2016 to 2020 Tennessee Pregnancy Risk Assessment Monitoring System complex survey analysis procedures. Uptake was measured as receipt of flu vaccine in the 12 months before the most recent live birth, and positive recall of receiving provider advice to get the shot was the independent variable; for both we estimated 5-year averages stratified by race/ethnicity. Differences were assessed using chi-square tests. We modeled receipt of flu vaccine and estimated marginal predicted prevalence ratios (PRs); stratified models by race/ethnicity were constructed to estimate unadjusted and adjusted PRs. Results: The 5-year average for vaccine uptake before or during pregnancy was 56.7% but varied by race and ethnicity. Stratified bivariate analyses yielded different magnitudes of association by race/ethnicity between provider recommendation and flu vaccine receipt. After adjustment for payment source at delivery, marital status, age group, urbanicity, and maternal education, receiving a provider recommendation was strongly associated with flu vaccine uptake for all stratified models of pregnant women included in the study. The effect size was of a larger magnitude among non-Hispanic Black women, a population with a lower vaccine uptake. Conclusions: Given the association between provider recommendation and vaccine uptake in all groups, attention should be focused on increasing rates of provider recommendation.


Assuntos
Vacinas contra Influenza , Influenza Humana , Lactente , Feminino , Gravidez , Humanos , Gestantes , Vacinas contra Influenza/uso terapêutico , Etnicidade , Vacinação , Gravidez Múltipla , Influenza Humana/prevenção & controle
4.
Matern Child Health J ; 27(8): 1335-1342, 2023 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-36995650

RESUMO

OBJECTIVES: To assess emergency preparedness (EP) actions in women with a recent live birth. METHODS: Weighted survey procedures were used to evaluate EP actions taken by women with a recent live birth responding to an EP question assessing eight preparedness actions as part of the 2016 Tennessee Pregnancy Risk Assessment and Monitoring System (PRAMS) survey. Factor analysis was used to group preparedness actions. RESULTS: Overall, 82.7% [95% Confidence Interval (CI) 79.3%, 86.1%] of respondents reported any preparedness actions, with 51.8% (95% CI 47.2%, 56.4%) completing 1-4 actions. The most common actions were having supplies at home (63.0%; 95% CI 58.5%, 67.4%), an evacuation plan for children (48.5%; 95% CI 43.9%, 53.2%), supplies in another location (40.2%; 95% CI 35.6%, 44.7%), and a communication plan (39.7%; 95% CI 35.1%, 44.2%). Having personal evacuation plans (31.6%; 95% CI 27.3%, 36.0%) and copies of documents in alternate locations (29.3%; 95% CI 25.0%, 33.5%) were least common. Factor analysis yielded three factors: having plans, having copies of documents, and having supplies. Specific preparedness actions varied by education and income level. CONCLUSIONS FOR PRACTICE: Most Tennessee women (about 8 in 10 women) with a recent live birth reported at least one EP action. A three-part EP question may be sufficient for assessing preparedness in this population. These findings highlight opportunities to improve public health education efforts around EP.


Assuntos
Defesa Civil , Gravidez , Criança , Feminino , Humanos , Tennessee , Nascido Vivo , Medição de Risco , Escolaridade
5.
Prev Sci ; 2022 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-36194312

RESUMO

We conducted a mixed methods pilot feasibility study of a Stakeholder and Equity Data-Driven Implementation (SEDDI) process to facilitate using healthcare data to identify patient groups experiencing gaps in the use of evidence-based interventions (EBIs) and rapidly adapt EBIs to achieve greater access and equitable outcomes. We evaluated the feasibility and acceptability of SEDDI in a pilot hybrid type 2 effectiveness-implementation trial of a paired colorectal cancer (CRC) and social needs screening intervention at four federally qualified community health centers (CHCs). An external facilitator partnered with CHC teams to support initial implementation, followed by the SEDDI phase focused on advancing health equity. Facilitation sessions were delivered over 8 months. Preliminary evaluation of SEDDI involved convergent mixed methods with quantitative survey and focus group data. CHCs used data to identify gaps in outreach and completion of CRC screening with respect to race/ethnicity, gender, age, and language. Adaptations to improve access and use of the intervention included cultural, linguistic, and health literacy tailoring. CHC teams reported that facilitation and systematic review of data were helpful in identifying and prioritizing gaps. None of the four CHCs completed rapid cycle testing of adaptations largely due to competing priorities during the COVID-19 response. SEDDI has the potential for advancing chronic disease prevention and management by providing a stakeholder and data-driven approach to identify and prioritize health equity targets and guide adaptations to improve health equity. ClinicalTrials.gov Identifier: NCT04585919.

6.
MMWR Morb Mortal Wkly Rep ; 68(1): 6-10, 2019 Jan 11.
Artigo em Inglês | MEDLINE | ID: mdl-30629576

RESUMO

From 2004 to 2014, the incidence of neonatal abstinence syndrome (NAS) in the United States increased 433%, from 1.5 to 8.0 per 1,000 hospital births. The latest national data from 2014 indicate that one baby was born with signs of NAS every 15 minutes in the United States (1). NAS is a drug withdrawal syndrome that most commonly occurs among infants after in utero exposure to opioids, although other substances have also been associated with NAS. Prenatal opioid exposure has also been associated with poor fetal growth, preterm birth, stillbirth, and possible specific birth defects (2-5). NAS surveillance has often depended on hospital discharge data, which historically underestimate the incidence of NAS and are not available in real time, thus limiting states' ability to quickly direct public health resources (6,7). This evaluation focused on six states with state laws implementing required NAS case reporting for public health surveillance during 2013-2017 and reviews implementation of the laws, state officials' reports of data quality before and after laws were passed, and advantages and challenges of legally mandating NAS reporting for public health surveillance in the absence of a national case definition. Using standardized search terms in an online legal research database, laws in six states mandating reporting of NAS from medical facilities to state health departments (SHDs) or from SHDs to a state legislative body were identified. SHD officials in these six states completed a questionnaire followed by a semistructured telephone interview to clarify open-text responses from the questionnaire. Variability was found in the type and number of surveillance data elements reported and in how states used NAS surveillance data. Following implementation, five states with identified laws reported receiving NAS case reports within 30 days of diagnosis. Mandated NAS case reporting allowed SHDs to quantify the incidence of NAS in their states and to inform programs and services. This information might be useful to states considering implementing mandatory NAS surveillance.


Assuntos
Notificação de Abuso , Síndrome de Abstinência Neonatal/epidemiologia , Vigilância em Saúde Pública , Humanos , Estados Unidos/epidemiologia
7.
Pediatrics ; 142(3)2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-30166364

RESUMO

BACKGROUND: Neonatal abstinence syndrome (NAS) is a postnatal drug withdrawal syndrome that can occur after intrauterine opioid exposure. Adverse neurobehavioral outcomes have been documented in infants with NAS; however, educational outcomes have not been thoroughly examined. We analyzed Tennessee data to understand the need for special educational services among infants who are born with NAS. METHODS: By using Tennessee Medicaid and birth certificate data, infants who were born in Tennessee between 2008 and 2011 with a history of NAS were matched (1:3) to infants who were born during the same period without a history of NAS. Groups were matched on the basis of sex, race and/or ethnicity, age, birth region of residence, and Medicaid enrollment status. Data were linked to Tennessee Department of Education special education data during early childhood (3-8 years of age). Conditional multivariable logistic regression was used to assess associations between NAS and selected special education outcomes. RESULTS: A total of 1815 children with a history of NAS and 5441 children without NAS were assessed. Children with NAS were significantly more likely to be referred for a disability evaluation (351 of 1815 [19.3%] vs 745 of 5441 [13.7%]; P < .0001), to meet criteria for a disability (284 of 1815 [15.6%] vs 634 of 5441 [11.7%]; P < .0001), and to require classroom therapies or services (278 of 1815 [15.3%] vs 620 of 5441 [11.4%]; P < .0001). These findings were sustained in a multivariable analysis, with multiple models controlling for maternal tobacco use, maternal education status, birth weight, gestational age, and/or NICU admission. CONCLUSIONS: Results of this novel analysis linking health and education data revealed that children with a history of NAS were significantly more likely to have a subsequent educational disability.


Assuntos
Educação Inclusiva/estatística & dados numéricos , Deficiências da Aprendizagem/epidemiologia , Síndrome de Abstinência Neonatal/complicações , Criança , Pré-Escolar , Feminino , Humanos , Recém-Nascido , Deficiências da Aprendizagem/etiologia , Masculino , Medicaid , Tennessee/epidemiologia , Estados Unidos
8.
MMWR Morb Mortal Wkly Rep ; 64(5): 125-8, 2015 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-25674995

RESUMO

Over the last decade, rates of opioid pain reliever prescribing grew substantially in the United States, affecting many segments of the population, including pregnant women. Nationally, Tennessee ranks second in the rate of prescriptions written for opioid pain relievers, with 1.4 per person in 2012. The rising prevalence of opioid pain reliever use and misuse in Tennessee led to an increase in adverse outcomes in the state, including neonatal abstinence syndrome (NAS). NAS is a withdrawal syndrome experienced by infants shortly after birth. The syndrome most commonly occurs after antenatal exposure to opioids, although other medications have also been implicated. From 2000 to 2009, the incidence rate of NAS in Tennessee increased from 0.7 to 5.1 per 1,000 births, exceeding the national average, which increased from 1.2 to 3.4 per 1,000 births. NAS is associated with numerous morbidities for the infant, including low birth weight, poor feeding, and respiratory problems. Previous population-based analyses of NAS relied on hospital discharge data, which typically become available for analysis only after substantial delay. In Tennessee, the rising incidence of NAS and its associated public health burden created an urgent need for timelier incidence figures to drive policy and prevention efforts. Beginning January 1, 2013, the Tennessee Department of Health (TDH) made NAS reporting mandatory. A total of 921 cases were reported in 2013 (among 79,954 births), with the most cases clustered in eastern Tennessee; 63% of cases occurred to mothers who were reported to be using at least one substance prescribed by a health care provider (e.g., opioid pain relievers or maintenance medications for opioid dependency), and 33% of cases occurred among women using illicit or diverted substances (e.g., heroin or medications prescribed for someone else). The first year's surveillance results highlight the need for primary prevention activities focused on reducing dependence/addiction among women of childbearing age and preventing unintended pregnancy among female opioid users.


Assuntos
Síndrome de Abstinência Neonatal/epidemiologia , Vigilância da População , Feminino , Humanos , Recém-Nascido , Masculino , Transtornos Relacionados ao Uso de Opioides/epidemiologia , Gravidez , Tennessee/epidemiologia
9.
Matern Child Health J ; 19(2): 335-42, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25008405

RESUMO

Workforce development is a priority across many state Maternal and Child Health (MCH) Title V programs. Three case studies were conducted to explore varied state implementations of MCH workforce development initiatives. Three states utilized the online MCH Navigator resource to support orientation and ongoing professional development for staff and other partners. Key informant interviews and surveys were utilized to gather staff feedback on practical aspects of the project and to ascertain lessons learned by state MCH leadership during project implementation. Staff impressions of the MCH Navigator were generally positive. Staff reported that Navigator modules were useful to their current work and that completion of the modules resulted in expanded knowledge in key MCH competency areas and contributed to their professional development. Many indicated that they would recommend use of the Navigator to colleagues. State leaders found that utilization of introductory training sessions or the Navigator's online orientation modules were helpful in acclimating staff to the Navigator, although some staff still experienced minor technical challenges. State leaders across all three sites reported the value of pre-existing tools on the Navigator site, including core competency self-assessments and orientation bundles; the leaders also noted that the Navigator represents a useful and thorough resource that can be integrated into state efforts to enhance professional development for MCH staff. The significant variation between the three states' implementations demonstrates the flexibility of the Navigator, highlighting its utility to meet state-specific needs.


Assuntos
Pessoal de Saúde/educação , Mão de Obra em Saúde/organização & administração , Internet/estatística & dados numéricos , Centros de Saúde Materno-Infantil , Competência Profissional , Feminino , Humanos , Masculino , Maryland , Oklahoma , Avaliação de Programas e Projetos de Saúde , Autoavaliação (Psicologia) , Desenvolvimento de Pessoal/métodos , Tennessee
10.
Pediatr Blood Cancer ; 60(4): 663-8, 2013 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-23255294

RESUMO

BACKGROUND: Childhood cancer survivors may have premature symptomatic cardiovascular and non-cardiovascular diseases that contribute to reduced capacity for physical activity. Studies of exercise capacity and identification of risk factors for reduced capacity in survivors are limited. PROCEDURE: We assessed maximal myocardial oxygen consumption (V(O(2)max), a measure of exercise capacity) in survivors at least 4 years after cancer diagnosis and sibling controls. We evaluated associations between V(O(2)max) and age, sex, treatments, cardiac structure and function, biomarkers, endocrine function, and physical activity. RESULTS: Of 72 survivors (mean age, 22 years; range, 8.0-40 years) and 32 siblings (mean age, 20.2 years; range, 8-46 years), about half were male. Mean time since diagnosis was 13.4 years (range, 4.5-31.6 years). In age- and sibling-pair adjusted analyses, V(O(2)max) was lower in survivors than siblings (males, 28.53 vs. 30.90 ml/kg/minute, P = 0.08; females, 19.81 vs. 23.40 ml/kg/minute, P = 0.03). In males, older age (P = 0.01), higher percent body fat (P < 0.001) and high or low left ventricular (LV) mass Z-scores (P = 0.03) predicted lower V(O(2)max). In females, older age (P < 0.001), methotrexate exposure (P = 0.01), and higher, but normal, LV load-dependent contractility (P = 0.02) predicted lower V(O(2)max). CONCLUSIONS: Fitness for most survivors and controls was poor and generally lower in survivors, particularly females. Older age, higher body fat, methotrexate exposure, and extremes of LV mass/function were associated with lower V(O(2)max) in survivors. Because physical activity can improve nutritional and cardiac conditions, survivors should be encouraged to exercise regularly with close monitoring.


Assuntos
Doenças Cardiovasculares/etiologia , Neoplasias/complicações , Consumo de Oxigênio/fisiologia , Aptidão Física , Função Ventricular Esquerda/fisiologia , Adolescente , Adulto , Criança , Estudos Transversais , Teste de Esforço , Feminino , Humanos , Masculino , Miocárdio/metabolismo , Fatores de Risco , Sobreviventes , Fatores de Tempo , Adulto Jovem
11.
Arch Womens Ment Health ; 15(4): 307-11, 2012 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-22588510

RESUMO

Thirteen percent of women experience postpartum depression. Prenatal screening for anticipated postpartum social support, a postpartum depression risk factor, may allow for early intervention. We sought to validate use of a modified version of the Postpartum Social Support Questionnaire (PSSQ) in pregnant women at increased risk for postpartum depression. Factor analysis using orthogonal varimax rotation was used. The modified PSSQ, administered during pregnancy, yields similar loading patterns as observed in postpartum administration of the original PSSQ.


Assuntos
Depressão Pós-Parto/prevenção & controle , Período Pós-Parto/psicologia , Apoio Social , Inquéritos e Questionários , Adulto , Análise Fatorial , Feminino , Georgia , Humanos , Cuidado Pré-Natal , Estudos Prospectivos , Fatores de Risco
12.
Environ Sci Technol ; 44(14): 5377-82, 2010 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-20536226

RESUMO

Ambient concentrations of eight predominantly anthropogenic halocarbons were measured via in situ gas chromatography in California's South Coast air basin for both summer and fall during the 2005 Study of Organic Aerosols at Riverside (SOAR). Ongoing emissions of the banned halocarbons methylchloroform and CFC-11 were observed in the South Coast air basin, whereas CFC-113 emissions have effectively ceased. We estimate anthropogenic emissions in the South Coast air basin for methylchloroform, CFC-11, HCFC-141b, chloroform, tetrachloroethene (PCE), trichloroethylene (TCE), and dichloromethane based on regressions of halocarbon to carbon monoxide mixing ratios and carbon monoxide emission inventories. We estimate per capita methylchloroform and chloroform emissions in the South Coast air basin for the year 2005 to be 6.6 +/- 0.4 g/(person.year) and 19 +/- 1 g/(person.year), respectively. We compare our results to national emission estimates calculated from previous work; for several compounds, emissions in the South Coast air basin are significantly lower than national per capita emissions. We observed strong seasonal differences in anthropogenic emissions of methylchloroform and chloroform; emissions were 4.5 and 2.5 times greater in summer than in fall, respectively. Possible seasonal sources include landfills and water chlorination. We conclude that seasonal variability in methylchloroform emissions has not been included in previous inventories and may cause errors in methylchloroform emission estimates after the year 2000 and seasonally resolved inversion calculations of hydroxyl radical abundance.


Assuntos
Poluentes Atmosféricos/química , Hidrocarbonetos Halogenados/química , Estações do Ano , Ritmo Circadiano , Atividades Humanas , Fatores de Tempo
13.
Environ Sci Technol ; 43(12): 4247-52, 2009 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-19603630

RESUMO

On- and off-road mobile sources are the dominant contributors to urban anthropogenic volatile organic compound (AVOC) emissions. Analyses of gasoline samples from California for both summer and winter indicate significant differences in liquid fuel and vapor chemical composition due to intentional seasonal adjustments. Ambient concentrations of 55 VOCs were measured via in situ gas chromatography in the 2005 Study of Organic Aerosols at Riverside (SOAR) during both summer and fall. A chemical mass balance analysis was used to differentiate vapor pressure-driven VOC emissions from other motor vehicle-related emissions such as tailpipe exhaust. Overall, fuel vapor emissions accounted for 31 +/- 2% of gasoline-related VOC in Riverside; California's emission factor model similarly estimates 31% of gasoline-related VOC emissions are fuel vapor. The diurnal pattern of vapor pressure-driven VOC source contributions is relatively stable around 10 microg/m3, while whole gasoline (i.e., tailpipe) contributions peak at approximately 60 microg/m3 during the morning commute. There is no peak in whole gasoline source contributions during the afternoon, due to rapid dilution associated with high mixing heights and wind speeds in the Riverside area. The relationship between estimated gasoline-related VOC and observed carbon monoxide concentrations in this study is similar to California's 2005 emission inventory; we calculated a VOC to CO mass ratio of 0.086 +/- 0.006 (95% CI) compared to 0.097 in the emission inventory for all gasoline-related sources.


Assuntos
Gasolina , Emissões de Veículos/análise , Compostos Orgânicos Voláteis/química , Poluentes Atmosféricos/química , Poluição do Ar , California , Ritmo Circadiano , Monitoramento Ambiental , Estações do Ano
14.
J Phys Chem A ; 109(9): 1879-89, 2005 Mar 10.
Artigo em Inglês | MEDLINE | ID: mdl-16833520

RESUMO

Kinetics studies of the OH-initiated oxidation of 2-butyne, propyne, and acetylene were conducted at 100 Torr and 298 K using turbulent flow chemical ionization mass spectrometry. The major oxidation products were identified, and with the aid of supporting electronic structure thermodynamics calculations, a general OH-initiated oxidation mechanism for the alkynes is proposed. The major product branching ratio and the product-forming rate constants for the 2-butyne-OH adduct + O(2) reaction were experimentally determined as well. The atmospheric implications of the chemical oxidation mechanism and kinetics results are discussed.

15.
Photochem Photobiol ; 77(2): 158-64, 2003 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-12785054

RESUMO

Lifetimes of the lowest excited singlet (S1) electronic states of various derivatives of the pyrimidine nucleobase cytosine (Cyt) were measured by the femtosecond transient absorption technique. The bases were excited in room-temperature aqueous solution at 265 nm using approximately 200 fs pump pulses from a titanium-sapphire laser system. The decay of excited-state absorption (ESA) at visible probe wavelengths was used to determine the S1 lifetimes of a variety of modified Cyt compounds at different pH values by global fitting. Identical lifetimes were observed for Cyt and cytidine (Cyd) within experimental uncertainty, but ESA by the ribonucleoside was considerably stronger, suggesting that the ribose group increases the oscillator strength of the S1 --> SN transition. The S1 lifetime of the important minor base 5-methylcytosine (m5Cyt) is 7.2 +/- 0.4 ps at pH 6.8. The same lifetime was measured for the ribonucleoside 5-methylcytidine, but sugar substitution again increased the strength of the ESA signal. Protonation of Cyd and m5Cyt at low pH led to a modest decrease in their S1 lifetimes. On the other hand, deprotonation of Cyt and m5Cyt significantly increased the lifetime of their respective S1 states. These trends support the intermediacy of the n,pi* state localized on the carbonyl oxygen in the nonradiative decay mechanism of Cyt. Longer S1 lifetimes were observed for 5-fluorocytosine and N4-acetylcytosine. Collectively, these results illustrate the great potential of femtosecond laser spectroscopy for investigating excited-state dynamics in DNA and DNA components.


Assuntos
Citosina/química , Espectrofotometria Ultravioleta/métodos , Metilação
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