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1.
Lupus ; 26(6): 623-632, 2017 May.
Artigo em Inglês | MEDLINE | ID: mdl-27703053

RESUMO

Objective The objective of this study was to estimate the proportion of pregnant women with systemic lupus erythematosus meeting Institute of Medicine guidelines for gestational weight gain and determine correlates of adherence to guidelines. Methods Singleton, live births in the Hopkins Lupus Pregnancy Cohort 1987-2015 were included. Pre-pregnancy weight was the weight recorded 12 months prior to pregnancy/first trimester. Final weight was the last weight recorded in the third trimester. Adherence to Institute of Medicine guidelines (inadequate, adequate, or excessive) was based on pre-pregnancy body mass index. Fisher's exact test and analysis of variance determined factors associated with not meeting guidelines. Stepwise selection estimated predictors of gestational weight gain. Results Of the 211 pregnancies, 34%, 24% and 42% had inadequate, adequate and excessive gestational weight gain, respectively. In exploratory analyses, differences in Institute of Medicine adherence were observed by pre-pregnancy body mass index, race, elevated creatinine during pregnancy and pre-pregnancy blood pressure. Odds of inadequate and excessive gestational weight gain increased 12% with each 1 kg/m2 increase in pre-pregnancy body mass index. Lower maternal education was associated with increased odds of inadequate and excessive gestational weight gain. Conclusions As in the general population, most women with systemic lupus erythematosus did not meet Institute of Medicine guidelines. Our results identified predictors of gestational weight gain to aid in targeted interventions to improve guideline adherence in this population.


Assuntos
Lúpus Eritematoso Sistêmico/complicações , Obesidade/epidemiologia , Complicações na Gravidez/epidemiologia , Adulto , Índice de Massa Corporal , Feminino , Humanos , Guias de Prática Clínica como Assunto , Gravidez , Terceiro Trimestre da Gravidez , Aumento de Peso
2.
Cerebrovasc Dis ; 31(6): 552-8, 2011.
Artigo em Inglês | MEDLINE | ID: mdl-21487219

RESUMO

BACKGROUND: Atherosclerosis is characterized by infiltration of inflammatory cells from circulating blood. Blood cell activation could play an important role in plaque formation. METHODS: We analyzed the relationship between blood cellular markers and quantitative measures of carotid wall components in 1,546 participants from the ARIC (Atherosclerosis Risk in Communities) Carotid MRI Study. Carotid imaging was performed using a gadolinium contrast-enhanced MRI and cellular phenotyping by flow cytometry. RESULTS: Monocyte Toll-like receptor (TLR)-2 is associated with larger plaques, while CD14, myeloperoxidase, and TLR-4 associate with smaller. Platelet CD40L is associated with smaller plaques and thinner caps, while P-selectin is associated with smaller core size. CONCLUSIONS: Blood cell activation is significantly associated with atherosclerotic changes of the carotid wall.


Assuntos
Biomarcadores/metabolismo , Plaquetas/metabolismo , Doenças das Artérias Carótidas/epidemiologia , Doenças das Artérias Carótidas/metabolismo , Monócitos/metabolismo , Idoso , Artérias Carótidas/metabolismo , Artérias Carótidas/patologia , Doenças das Artérias Carótidas/patologia , Estudos Transversais , Feminino , Citometria de Fluxo , Humanos , Imunofenotipagem , Imageamento por Ressonância Magnética/métodos , Masculino , Pessoa de Meia-Idade , Prevalência , Estudos Prospectivos , Características de Residência , Fatores de Risco
3.
Pediatr Obes ; 14(5): e12498, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30629806

RESUMO

BACKGROUND: While attention-deficit/hyperactivity disorder (ADHD) has been associated with higher body mass index (BMI), little research has focused on how this association differs by sex or race/ethnicity. OBJECTIVE: To investigate the association between ADHD and BMI by sex and race/ethnicity (ie, European [EA], African [AA], and Hispanic American [HA]). METHODS: Data came from the National Longitudinal Survey of Adolescent to Adult Health Waves II to IV (n = 13 332, age: 12-34 years). On the basis of self-reported childhood ADHD symptoms between the ages of 5 and 12 years, participants were categorized into: ADHD predominantly hyperactive/impulsive (ADHD-HI); ADHD predominantly inattentive (ADHD-I); ADHD combined (ADHD-C; a combination of ADHD-HI and ADHD-I symptoms); and non-ADHD. RESULTS: The patterns of ADHD-BMI associations in the transition period between adolescence and young adulthood differed by sex and race/ethnicity. Compared with non-ADHD, ADHD-HI was associated with higher BMI among EA males and females, while ADHD-I was associated with higher BMI among EA females. ADHD-C was associated with higher BMI for HA females. We found no evidence of an association among AA males and females and HA males. CONCLUSION: These study results suggest that the association between ADHD subtypes and BMI might differ across population subgroups in the United States.


Assuntos
Transtorno do Deficit de Atenção com Hiperatividade/epidemiologia , Índice de Massa Corporal , Adolescente , Adulto , Transtorno do Deficit de Atenção com Hiperatividade/etnologia , Transtorno do Deficit de Atenção com Hiperatividade/etiologia , Criança , Pré-Escolar , Etnicidade , Feminino , Humanos , Estudos Longitudinais , Masculino , Fatores de Risco , Autorrelato , Fatores Sexuais , Estados Unidos/epidemiologia , Adulto Jovem
4.
Pediatr Obes ; 12(5): 422-430, 2017 10.
Artigo em Inglês | MEDLINE | ID: mdl-27273455

RESUMO

BACKGROUND: China has the world's highest diabetes prevalence, which along with hypertension and inflammation continues to grow particularly among children. Little is known about the strength of the association of these cardiometabolic risk factors between parents and their children; thus, the potential of household-based strategies to reduce risk is unknown. OBJECTIVES: The objective of the study is to examine the parent-child association for haemoglobin A1c (HbA1c), blood pressure (BP) and C-reactive protein (CRP) in a large, geographically diverse Chinese sample. METHODS: In 940 parent-child pairs (children aged 7-17 years) who participated in the 2009 China Health and Nutrition Survey, we measured each individual's HbA1c and CRP using fasting blood and BP. We used sex-specific random-effects linear regression to examine the parent-child association for these risk factors, accounting for within-family clustering. RESULTS: Child's HbA1c was positively associated with parental HbA1c. Beta coefficients ranged from 0.06 (95% CI 0.03-0.12) for father-daughter to 0.43 (95% CI 0.28-0.58) for mother-son pairs. We also detected a positive mother-daughter association for BP and positive father-child associations for CRP. CONCLUSION: The statistically significant parent-child association for HbA1c, BP and CRP in Chinese families suggests that household-based interventions could be useful for confronting the high rates of diabetes, hypertension and inflammation in China.


Assuntos
Pressão Sanguínea/fisiologia , Proteína C-Reativa/metabolismo , Hemoglobinas Glicadas/metabolismo , Adolescente , Povo Asiático , Criança , China , Características da Família , Jejum/sangue , Feminino , Humanos , Masculino , Inquéritos Nutricionais , Relações Pais-Filho , Pais , Prevalência , Fatores de Risco
5.
J Hum Hypertens ; 31(3): 225-230, 2017 03.
Artigo em Inglês | MEDLINE | ID: mdl-27629244

RESUMO

Cadmium (Cd) is an environmental pollutant that has been associated with cardiovascular disease in populations, but the relationship of Cd with hypertension has been inconsistent. We studied the association between urinary Cd concentrations, a measure of total body burden, and blood pressure in American Indians, a US population with above national average Cd burden. Urinary Cd was measured using inductively coupled plasma mass spectrometry, and adjusted for urinary creatinine concentration. Among 3714 middle-aged American Indian participants of the Strong Heart Study (mean age 56 years, 41% male, 67% ever-smokers, 23% taking antihypertensive medications), urinary Cd ranged from 0.01 to 78.48 µg g-1 creatinine (geometric mean=0.94 µg g-1) and it was correlated with smoking pack-year among ever-smokers (r2=0.16, P<0.0001). Participants who were smokers were on average light-smokers (mean 10.8 pack-years), and urinary Cd was similarly elevated in light- and never-smokers (geometric means of 0.88 µg g-1 creatinine for both categories). Log-transformed urinary Cd was significantly associated with higher systolic blood pressure in models adjusted for age, sex, geographic area, body mass index, smoking (ever vs never, and cumulative pack-years) and kidney function (mean blood pressure difference by lnCd concentration (ß)=1.64, P=0.002). These associations were present among light- and never-smokers (ß=2.03, P=0.002, n=2627), although not significant among never-smokers (ß=1.22, P=0.18, n=1260). Cd was also associated with diastolic blood pressure among light- and never-smokers (ß=0.94, P=0.004). These findings suggest that there is a relationship between Cd body burden and increased blood pressure in American Indians, a population with increased cardiovascular disease risk.


Assuntos
Pressão Sanguínea , Cádmio/urina , Hipertensão/urina , Indígenas Norte-Americanos/estatística & dados numéricos , Carga Corporal (Radioterapia) , Estudos Transversais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade
6.
Nutr Diabetes ; 5: e166, 2015 Jun 22.
Artigo em Inglês | MEDLINE | ID: mdl-26098445

RESUMO

BACKGROUND/OBJECTIVES: Nonglycemic factors like iron deficiency (ID) or anemia may interfere with classification of diabetes and prediabetes using hemoglobin A1c (HbA1c). However, few population-based studies of diabetes in areas with endemic ID/anemia have been conducted. We aimed to determine how mutually exclusive categories of ID alone, anemia alone and iron-deficiency anemia (IDA) were each associated with prediabetes and diabetes prevalence using fasting blood glucose (FBG) versus HbA1c in a population-based study of adults with endemic ID/anemia. SUBJECTS/METHODS: We used data from the China Health and Nutrition Survey, a longitudinal, population-based study across 228 communities within nine provinces of China. This analysis included 7308 adults seen in the 2009 survey aged 18-75 years. We used descriptive and covariate-adjusted models to examine relative risk of prediabetes and diabetes using FBG alone, HbA1c alone, HbA1c and FBG, or neither (normoglycemia) by anemia alone, ID alone, IDA or normal iron/hemoglobin. RESULTS: Approximately 65% of individuals with diabetes in our sample were concordantly classified with diabetes using both FBG and HbA1c, while 35% had a discordant diabetes classification: they were classified using either FBG or HbA1c, but not both. Fewer participants with ID alone versus normal iron/hemoglobin were classified with diabetes using HbA1c only. From covariate-adjusted, multinomial regression analyses, the adjusted prevalence of prediabetes using HbA1c only was 22% for men with anemia alone, but 13% for men with normal iron/hemoglobin. In contrast, the predicted prevalence of prediabetes using HbA1c only was 8% for women with ID alone, compared with 13% for women with normal iron/hemoglobin. CONCLUSIONS: These findings suggest potential misclassification of diabetes using HbA1c in areas of endemic ID/anemia. Estimating diabetes prevalence using HbA1c may result in under-diagnosis in women with ID and over-diagnosis in men with anemia.

7.
Cell Death Dis ; 6: e1813, 2015 Jul 09.
Artigo em Inglês | MEDLINE | ID: mdl-26158519

RESUMO

The human inflammatory caspases, including caspase-1, -4, -5 and -12, are considered as key regulators of innate immunity protecting from sepsis and numerous inflammatory diseases. Caspase-1 is activated by proximity-induced dimerization following recruitment to inflammasomes but the roles of the remaining inflammatory caspases in inflammasome assembly are unclear. Here, we use caspase bimolecular fluorescence complementation to visualize the assembly of inflammasomes and dimerization of inflammatory caspases in single cells. We observed caspase-1 dimerization induced by the coexpression of a range of inflammasome proteins and by lipospolysaccharide (LPS) treatment in primary macrophages. Caspase-4 and -5 were only dimerized by select inflammasome proteins, whereas caspase-12 dimerization was not detected by any investigated treatment. Strikingly, we determined that certain inflammasome proteins could induce heterodimerization of caspase-1 with caspase-4 or -5. Caspase-5 homodimerization and caspase-1/-5 heterodimerization was also detected in LPS-primed primary macrophages in response to cholera toxin subunit B. The subcellular localization and organization of the inflammasome complexes varied markedly depending on the upstream trigger and on which caspase or combination of caspases were recruited. Three-dimensional imaging of the ASC (apoptosis-associated speck-like protein containing a caspase recruitment domain)/caspase-1 complexes revealed a large spherical complex of ASC with caspase-1 dimerized on the outer surface. In contrast, NALP1 (NACHT leucine-rich repeat protein 1)/caspase-1 complexes formed large filamentous structures. These results argue that caspase-1, -4 or -5 can be recruited to inflammasomes under specific circumstances, often leading to distinctly organized and localized complexes that may impact the functions of these proteases.


Assuntos
Caspase 1/metabolismo , Caspases/metabolismo , Inflamação/enzimologia , Análise de Célula Única/métodos , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Apoptose/imunologia , Proteínas Reguladoras de Apoptose/metabolismo , Proteínas Adaptadoras de Sinalização CARD , Caspase 1/química , Caspase 1/isolamento & purificação , Caspase 12/química , Caspase 12/isolamento & purificação , Caspase 12/metabolismo , Caspases/química , Caspases/isolamento & purificação , Caspases Iniciadoras , Toxina da Cólera/farmacologia , Proteínas do Citoesqueleto/metabolismo , Humanos , Imunidade Inata/genética , Inflamassomos/química , Inflamassomos/metabolismo , Inflamação/patologia , Macrófagos/enzimologia , Imagem Molecular/métodos , Proteínas NLR , Multimerização Proteica
8.
Chem Biol Interact ; 17(3): 257-63, 1977 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-880696

RESUMO

Cadmium, zinc and copper, accumulated from polluted habitats by the oysters Ostrea edulis and Crassostrea gagas, were studied. Three distinct low molecular weight (less than 3000 daltons) zinc complexes were separated from highly contaminated C. gigas, one of which may be a complex with the amino acid taurine. Only one of these zinc complexes was present in less contaminated specimens of O. edulis. On gel permeation chromatography of oyster extracts, copper was eluted together with amino acids (principally taurine) and the betaine homarine. No evidence of metallothionein type proteins was found.


Assuntos
Cádmio/metabolismo , Cobre/metabolismo , Ostreidae/metabolismo , Poluição Química da Água , Zinco/metabolismo , Aminoácidos/metabolismo , Animais , Sítios de Ligação , Peso Molecular , Especificidade da Espécie , Espectrofotometria Ultravioleta
9.
Chem Biol Interact ; 16(1): 107-14, 1977 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-837462

RESUMO

The accumulation of cadmium, zinc and copper by the marine gastropod molluscs Patella vulgata and Patella intermedia has been studied by gel permeation chromatography of water-soluble extracts of environmentally contaminated shellfish. A major proportion of the water-soluble cadmium and copper in these molluscs is associated with a protein of molecular weight 10 800 daltons. Evidence is presented supporting the similarity of this protein with mammalian metallothionein. This protein contained only a small proportion of the zinc found in the samples.


Assuntos
Metais/metabolismo , Moluscos/metabolismo , Poluição da Água , Aminoácidos/metabolismo , Animais , Cádmio/metabolismo , Cobre/metabolismo , Compostos de Sulfidrila/metabolismo , Zinco/metabolismo
10.
Chem Biol Interact ; 23(2): 227-31, 1978 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-709687

RESUMO

The accumulation of cadmium, zinc and copper by environmentally contaminated periwinkles, cockles and scallops has been studied by gel permeation chromatography of water-soluble extracts of the shellfish. Three distinct low mol. wt. (less than 3000) zinc complexes were separated from periwinkle extracts. Copper and cadmium were present as a single low mol. wt. species which is apparently responsible for the elevated copper levels in Littorina littorea.


Assuntos
Metais/metabolismo , Moluscos/metabolismo , Animais , Cádmio/metabolismo , Cromatografia em Gel , Cobre/metabolismo , Zinco/metabolismo
11.
Talanta ; 26(9): 895-7, 1979 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-18962535

RESUMO

The preconcentration of "inorganic" and methyl mercury cations from aqueous solution is described. The procedure involves collection of mercury on dithizone-coated macroreticular resin beads prior to analysis by cold-vapour atomic absorption spectroscopy. The beads are readily prepared before use and give rise to quantitative selective recovery of "inorganic" and methyl mercury from fresh and saline water samples.

12.
Talanta ; 32(8 Pt 2): 709-22, 1985 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-18963995

RESUMO

The modified simplex method is a well-known method of optimization. In this study several changes have been made to it. These include an adaptive weighted centroid and a Lagrange interpolation procedure. The latter is used to get a better value of the reflected point when a contraction succeeds or an expansion fails. The new method, called the composite modified simplex method (CMS) has been rigorously evaluated by means of mathematical functions, maps and chemical experimentation. The effect of the starting point and the size of the simplex have been investigated in detail. For flow-injection analysis it has proved possible to optimize 2-12 variables. The method has proved most suitable for rapid and effective optimization of polarography, flow-injection analysis and chemical synthesis. This paper describes the evaluation procedures and reviews the results obtained.

13.
Talanta ; 32(8 Pt 2): 723-34, 1985 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-18963996

RESUMO

This paper discusses the details of the composite modified simplex, critically compares it with other simplex methods, and reviews the value of this type of optimization procedure.

14.
Curr Eye Res ; 4(2): 97-102, 1985 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-3987351

RESUMO

The present study demonstrated that less than three days of exposure to low levels of normally cycled ambient illumination are sufficient to cause death to photoreceptor cells in adult pigmented and albino rat. Cyclic light levels as low as 133 and 320 lux were found to destroy photoreceptor cells. A single mydriatic treatment with atropine immediately preceding the three-day exposure was sufficient to permit the effect in pigmented rats. No mydriasis was required for albino rats. When pigmented rats were reared in either 3 lux or 100 lux, it was found that these different light histories did not significantly affect the rats' subsequent susceptibility, during mydriasis, to retinal damage by cyclic illumination.


Assuntos
Albinismo/fisiopatologia , Atropina/farmacologia , Luz , Midriáticos/farmacologia , Pigmentação , Retina/efeitos da radiação , Albinismo/patologia , Animais , Relação Dose-Resposta à Radiação , Células Fotorreceptoras/patologia , Células Fotorreceptoras/efeitos da radiação , Coelhos , Ratos , Ratos Endogâmicos , Retina/lesões , Retina/patologia , Fatores de Tempo
15.
Obes Rev ; 15 Suppl 1: 27-36, 2014 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-24341756

RESUMO

Previous studies have linked work, home production, travel activities and inactivity with weight and health outcomes. However, these focused on average physical activity (PA) over time rather than changes in PA and associated sociodemographic and economic factors and urbanicity. Using the 1991-2011 China Health and Nutrition Survey data, we estimated the metabolic equivalent of task hours per week for individuals in occupational, domestic, travel and active leisure domains and sedentary hours per week. We present the distributions among adult men and women (aged 18-60), and use quantile regression models to explore factors associated with these trends. Trend analyses on the distribution of PA show declines along the whole distribution of occupational PA for men and women and domestic PA for women in China. These patterns remain consistent after adjusting for individual- and household-level factors. Controlling for urbanicity mitigated the decrease in occupational PA, particularly for men, but not the decrease in domestic PA. Given China's rapid urbanization and its association with occupational PA declines and the strong time trend in domestic PA, there is a need to invest in interventions and policies that promote PA during leisure and travel times.


Assuntos
Povo Asiático , Exercício Físico , Transição Epidemiológica , Atividades de Lazer , Atividade Motora , Comportamento Sedentário , Trabalho/tendências , Adulto , China/epidemiologia , Feminino , Conhecimentos, Atitudes e Prática em Saúde , História do Século XX , História do Século XXI , Humanos , Masculino , Pessoa de Meia-Idade , Inquéritos Nutricionais , Vigilância da População , Fatores Socioeconômicos , Urbanização , Trabalho/estatística & dados numéricos
16.
Talanta ; 65(2): 574-7, 2005 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-18969837

RESUMO

This paper presents an HPLC based procedure that has been developed for the determination of the 9-fluorenylmethoxycarbonyl (FMOC) content of protected amine-functionalised polymer beads. FMOC reagents are frequently employed both in the protection of amines and in their determination. The procedure utilises the stoichiometric base cleavage of dibenzofulvene from the protected amine using 1,8-diazabicyclo undec-7-ene. This stearically hindered base prevents the adduct formation that occurs with alternative base systems and measurement performance is enhanced by the incorporation of anthracene into the system as a non-reactive internal standard. HPLC separation of the reaction products permits the measurement of FMOC in the presence of additional chromophores that might otherwise impede direct measurement by UV-vis spectrophotometry. The procedure has been evaluated for the measurement of the FMOC content of protected amine-modified polymer beads employed in combinatorial solid phase synthesis.

17.
Analyst ; 129(9): 860-3, 2004 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-15343404

RESUMO

A sensitive spectofluorimetric method has been developed for the quantitative measurement of surface-bound thiol groups. The procedure is based on the quantitative esterification of the thiol group with Rhodamine B and its subsequent release from the solid by base hydrolysis for spectrofluorimetric determination. Application of the method to the analysis of thiol-modified nanoparticulate silicas yielded results that compared favourably against alternative approaches based on measurements of mercury capacity and iodometric titration of the thiol groups. Non-specific Rhodamine uptake, assessed using unmodified silica and C18-modified silica, did not significantly influence the analytical results. When applied to a typical 50 mg sample, the detection limit of the procedure was 1 nmole SH g(-1) silica.


Assuntos
Compostos de Sulfidrila/análise , Nanotecnologia , Rodaminas/química , Dióxido de Silício/química , Espectrometria de Fluorescência/métodos , Compostos de Sulfidrila/química
18.
Int J Environ Anal Chem ; 14(1): 43-53, 1983.
Artigo em Inglês | MEDLINE | ID: mdl-6192102

RESUMO

Following collection of diesel particulate samples on high efficiency glass fibre papers, and Soxhlet extraction with cyclohexane, a two-stage clean-up involving DMF/H2O partition and silica gel thin-layer chromatography is required in order to simplify the extract. Individual compound identification can then be achieved by high resolution gas chromatography using WCOT quartz capillary columns with flame ionisation or computer-assisted electron impact mass spectrometry detection systems. The technique provides a relatively quick and simple enrichment step, whilst the high separating power of the capillary column is able to resolve the many chromatographically similar isomers and substituted PAH members that are present. Investigations indicate that presence of a vast range of PAH species, comprising both substituted and unsubstituted two- to seven-membered ring systems, many of which are known carcinogens and mutagens.


Assuntos
Óleos Combustíveis/análise , Petróleo/análise , Compostos Policíclicos/análise , Emissões de Veículos/análise , Cromatografia Gasosa , Cromatografia em Camada Fina , Espectrometria de Massas
19.
Anal Chem ; 69(15): 2882-7, 1997 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-21639309

RESUMO

Novel HPLC instrumentation has been developed which employs an in-line sodium tetrahydroborate (borohydride) reaction step to generate volatile sulfur species from a variety of sulfonium compounds. Transfer of the resulting volatile sulfur-containing products into the gas phase permits them to be monitored using sulfur-specific flame photometric detection. The system has been evaluated for the determination of a collection of dimethylsulfonium compounds, comprising (dimethylsulfonio)propionate, S-methylmethionine (SMM), (dimethylsulfonio)-2-methylpropionate, dimethylsulfocholine, (dimethylsulfonio)acetate, (dimethylsulfonio)butanoate, and (dimethylsulfonio)pentanoate. Following their separation by either cation- or anion-exchange HPLC, these compounds react in-line with the tetrahydroborate, generating dimethyl sulfide, which is then swept into a flame photometric detector. The development of chromatographic conditions for the resolution of the seven sulfonium compounds is described. In an example application of the instrumentation, the levels of SMM in parsley and cabbage were found to be 16 and 74 mmol kg(-)(1), respectively, on a fresh weight basis.

20.
Analyst ; 126(4): 538-41, 2001 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-11340995

RESUMO

Polymer beads are the starting point of many synthetic protocols, and in a number of combinatorial syntheses such studies are based on single beads. It has therefore become important that individual beads carry the same functional group activity and quality control of populations of beads requires a knowledge of the distribution of activity between the individual beads. A procedure was developed for the measurement of the thiol loading of single copolymer beads which is based on the bleaching of Michler's hydrol [4,4'-bis(dimethylamino)-diphenylcarbinol (BDC-OH)]. Flow injection colorimetry permits the small volumes of solution generated from single beads to be measured with rapid turnover and with a reproducibility of ca. 2%. The solution detection limit of 0.17 mM corresponds to a bead thiol concentration of 0.33 mmol g-1. The procedure and the variability of a bead population were demonstrated using modified styrene-divinylbenzene copolymer beads. The apparatus allowed fast, simple and accurate determinations to be carried out on the individual polymer beads. Within a single batch of thiol-modified styrene-divinylbenzene beads thiol loadings ranged from < 0.35 to 2.07 mmol g-1 or 0.12 to 1.3 mumol per bead. Polydispersity may therefore significantly influence screening decisions based on single bead syntheses.

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