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1.
Nat Commun ; 14(1): 7258, 2023 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-37990023

RESUMO

The COVID-19 pandemic led to unparalleled pressure on healthcare services. Improved healthcare planning in relation to diseases affecting the respiratory system has consequently become a key concern. We investigated the value of integrating sales of non-prescription medications commonly bought for managing respiratory symptoms, to improve forecasting of weekly registered deaths from respiratory disease at local levels across England, by using over 2 billion transactions logged by a UK high street retailer from March 2016 to March 2020. We report the results from the novel AI (Artificial Intelligence) explainability variable importance tool Model Class Reliance implemented on the PADRUS model (Prediction of Amount of Deaths by Respiratory disease Using Sales). PADRUS is a machine learning model optimised to predict registered deaths from respiratory disease in 314 local authority areas across England through the integration of shopping sales data and focused on purchases of non-prescription medications. We found strong evidence that models incorporating sales data significantly out-perform other models that solely use variables traditionally associated with respiratory disease (e.g. sociodemographics and weather data). Accuracy gains are highest (increases in R2 (coefficient of determination) between 0.09 to 0.11) in periods of maximum risk to the general public. Results demonstrate the potential to utilise sales data to monitor population health with information at a high level of geographic granularity.


Assuntos
COVID-19 , Transtornos Respiratórios , Doenças Respiratórias , Humanos , Pandemias , Inteligência Artificial , COVID-19/epidemiologia , Previsões
2.
JMIR Cancer ; 9: e37141, 2023 Mar 31.
Artigo em Inglês | MEDLINE | ID: mdl-37000495

RESUMO

BACKGROUND: Shopping data can be analyzed using machine learning techniques to study population health. It is unknown if the use of such methods can successfully investigate prediagnosis purchases linked to self-medication of symptoms of ovarian cancer. OBJECTIVE: The aims of this study were to gain new domain knowledge from women's experiences, understand how women's shopping behavior relates to their pathway to the diagnosis of ovarian cancer, and inform research on computational analysis of shopping data for population health. METHODS: A web-based survey on individuals' shopping patterns prior to an ovarian cancer diagnosis was analyzed to identify key knowledge about health care purchases. Logistic regression and random forest models were employed to statistically examine how products linked to potential symptoms related to presentation to health care and timing of diagnosis. RESULTS: Of the 101 women surveyed with ovarian cancer, 58.4% (59/101) bought nonprescription health care products for up to more than a year prior to diagnosis, including pain relief and abdominal products. General practitioner advice was the primary reason for the purchases (23/59, 39%), with 51% (30/59) occurring due to a participant's doctor believing their health problems were due to a condition other than ovarian cancer. Associations were shown between purchases made because a participant's doctor believing their health problems were due to a condition other than ovarian cancer and the following variables: health problems for longer than a year prior to diagnosis (odds ratio [OR] 7.33, 95% CI 1.58-33.97), buying health care products for more than 6 months to a year (OR 3.82, 95% CI 1.04-13.98) or for more than a year (OR 7.64, 95% CI 1.38-42.33), and the number of health care product types purchased (OR 1.54, 95% CI 1.13-2.11). Purchasing patterns are shown to be potentially predictive of a participant's doctor thinking their health problems were due to some condition other than ovarian cancer, with nested cross-validation of random forest classification models achieving an overall in-sample accuracy score of 89.1% and an out-of-sample score of 70.1%. CONCLUSIONS: Women in the survey were 7 times more likely to have had a duration of more than a year of health problems prior to a diagnosis of ovarian cancer if they were self-medicating based on advice from a doctor rather than having made the decision to self-medicate independently. Predictive modelling indicates that women in such situations, who are self-medicating because their doctor believes their health problems may be due to a condition other than ovarian cancer, exhibit distinct shopping behaviors that may be identifiable within purchasing data. Through exploratory research combining women sharing their behaviors prior to diagnosis and computational analysis of these data, this study demonstrates that women's shopping data could potentially be useful for early ovarian cancer detection.

3.
BMC Med Ethics ; 23(1): 58, 2022 06 07.
Artigo em Inglês | MEDLINE | ID: mdl-35672737

RESUMO

BACKGROUND: A growing number of studies show the potential of loyalty card data for use in health research. However, research into public perceptions of using this data is limited. This study aimed to investigate public attitudes towards donating loyalty card data for academic health research, and the safeguards the public would want to see implemented. The way in which participant attitudes varied according to whether loyalty card data would be used for either cancer or COVID-19 research was also examined. METHODS: Participants (N = 40) were recruited via Prolific Academic to take part in semi-structured telephone interviews, with questions focused on data sharing related to either COVID-19 or ovarian/bowel cancer as the proposed health condition to be researched. Content analysis was used to identify sub-themes corresponding to the two a priori themes, attitudes and safeguards. RESULTS: Participant attitudes were found to fall into two categories, either rational or emotional. Under rational, most participants were in favour of sharing loyalty card data. Support of health research was seen as an important reason to donate such data, with loyalty card logs being considered as already within the public domain. With increased understanding of research purpose, participants expressed higher willingness to donate data. Within the emotional category, participants shared fears about revealing location information and of third parties obtaining their data. With regards to safeguards, participants described the importance of anonymisation and the level of data detail; the control, convenience and choice they desired in sharing data; and the need for transparency and data security. The change in hypothetical purpose of the data sharing, from Covid-19 to cancer research, had no impact on participants' decision to donate, although did affect their understanding of how loyalty card data could be used. CONCLUSIONS: Based on interviews with the public, this study contributes recommendations for those researchers and the wider policy community seeking to obtain loyalty card data for health research. Whilst participants were largely in favour of donating loyalty card data for academic health research, information, choice and appropriate safeguards are all exposed as prerequisites upon which decisions are made.


Assuntos
COVID-19 , Opinião Pública , Atitude , Humanos , Disseminação de Informação , Pesquisa Qualitativa
5.
J Fam Econ Issues ; 42(Suppl 1): 207, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33192038
7.
Front Psychol ; 8: 1443, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28894429

RESUMO

Objectives: Including or excluding certain questions about organ donation may influence peoples' intention to donate. We investigated the effect of omitting certain affective attitudinal items on potential donors' intention and behavior for donation. Design: A cross-sectional survey with a subgroup nested randomized trial. Methods: A total of 578 members of the public in four shopping centers were surveyed on their attitudes to organ donation. Non-donors (n = 349) were randomly assigned to one of three groups: Group 1 completed items on affective and cognitive attitudes, anticipated regret, intention, subjective norm and perceived behavioral control. Group 2 completed all items above but excluded affective attitudes. Group 3 completed all items but omitted negatively worded affective attitudes. The primary outcome was intention to donate, taking a donor card after the interview was a secondary behavioral outcome, and both were predicted using linear and logistic regression with group 1 as the reference. Results: Mean (SD) 1-7 intention scores for groups 1, 2 and 3 were, respectively: 4.43 (SD 1.89), 4.95 (SD 1.64) and 4.88 (SD 1.81), with group 2 significantly higher than group 1 (ß = 0.518, 95% confidence interval [CI] 0.18 to 0.86).At the end of the interview, people in group 2 (66.7%; OR = 1.40, 95% CI 0.94 to 2.07, p = 0.096) but not those in group 3 (61.7%; OR = 1.10, 95% CI 0.69 to 1.75, p = 0.685), were marginally more likely to accept a donor card from the interviewer than people in group 1 (59.7%). Conclusion: Omitting affective attitudinal items results in higher intention to donate organs and marginally higher rates of acceptance of donor cards, which has important implications for future organ donation public health campaigns.

8.
Bioorg Med Chem ; 19(8): 2742-50, 2011 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-21435888

RESUMO

PKCα and PKA have crucial but opposing roles in the regulation of calcium handling within myocytes. Identification of compounds that inhibit PKCα, but not PKA, are potential therapeutic targets for the treatment of heart disease. The synthesis of indolylureas are described, and a compound displaying nanomolar inhibition towards PKCα with significant selectivity over PKA has been identified.


Assuntos
Proteína Quinase C-alfa/antagonistas & inibidores , Inibidores de Proteínas Quinases/síntese química , Ureia/síntese química , Ureia/farmacologia , Proteínas Quinases Dependentes de AMP Cíclico , Cardiopatias/tratamento farmacológico , Humanos , Ureia/química
9.
BMC Musculoskelet Disord ; 12: 27, 2011 Jan 26.
Artigo em Inglês | MEDLINE | ID: mdl-21269506

RESUMO

BACKGROUND: Control of skeletal muscle mass and force production is a complex physiological process involving numerous regulatory systems. Agents that increase skeletal muscle cAMP levels have been shown to modulate skeletal muscle mass and force production. The dopamine 1 receptor and its closely related homolog, the dopamine 5 receptor, are G-protein coupled receptors that are expressed in skeletal muscle and increase cAMP levels when activated. Thus we hypothesize that activation of the dopamine 1 and/or 5 receptor will increase skeletal muscle cAMP levels thereby modulating skeletal muscle mass and force production. METHODS: We treated isolated mouse tibialis anterior (TA) and medial gastrocnemius (MG) muscles in tissue bath with the selective dopamine 1 receptor and dopamine 5 receptor agonist SKF 81297 to determine if activation of skeletal muscle dopamine 1 and dopamine 5 receptors will increase cAMP. We dosed wild-type mice, dopamine 1 receptor knockout mice and dopamine 5 receptor knockout mice undergoing casting-induced disuse atrophy with SKF 81297 to determine if activation of the dopamine 1 and dopamine 5 receptors results in hypertrophy of non-atrophying skeletal muscle and preservation of atrophying skeletal muscle mass and force production. RESULTS: In tissue bath, isolated mouse TA and MG muscles responded to SKF 81297 treatment with increased cAMP levels. Treating wild-type mice with SKF 81297 reduced casting-induced TA and MG muscle mass loss in addition to increasing the mass of non-atrophying TA and MG muscles. In dopamine 1 receptor knockout mice, extensor digitorum longus (EDL) and soleus muscle mass and force was not preserved during casting with SKF 81297 treatment, in contrast to significant preservation of casted wild-type mouse EDL and soleus mass and EDL force with SKF 81297 treatment. Dosing dopamine 5 receptor knockout mice with SKF 81297 did not significantly preserve EDL and soleus muscle mass and force although wild-type mouse EDL mass and force was significantly preserved SKF 81297 treatment. CONCLUSIONS: These data demonstrate for the first time that treatment with a dopamine 1/5 receptor agonist results in (1) significant preservation of EDL, TA, MG and soleus muscle mass and EDL muscle force production during periods of atrophy and (2) hypertrophy of TA and MG muscle. These effects appear to be mainly mediated by both the dopamine 1 and dopamine 5 receptors.


Assuntos
Força Muscular/fisiologia , Músculo Esquelético/metabolismo , Músculo Esquelético/patologia , Atrofia Muscular/metabolismo , Atrofia Muscular/patologia , Receptores de Dopamina D1/metabolismo , Receptores de Dopamina D5/metabolismo , Animais , Benzazepinas/farmacologia , Agonistas de Dopamina/farmacologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Força Muscular/efeitos dos fármacos , Músculo Esquelético/efeitos dos fármacos , Atrofia Muscular/tratamento farmacológico , Receptores de Dopamina D1/agonistas , Receptores de Dopamina D1/deficiência , Receptores de Dopamina D5/agonistas , Receptores de Dopamina D5/deficiência
10.
BMC Musculoskelet Disord ; 12: 15, 2011 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-21235761

RESUMO

BACKGROUND: Muscle weakness is associated with a variety of chronic disorders such as emphysema (EMP) and congestive heart failure (CHF) as well as aging. Therapies to treat muscle weakness associated with chronic disease or aging are lacking. Corticotrophin releasing factor 2 receptor (CRF2R) agonists have been shown to maintain skeletal muscle mass and force production in a variety of acute conditions that lead to skeletal muscle wasting. HYPOTHESIS: We hypothesize that treating animals with a CRF2R agonist will maintain skeletal muscle mass and force production in animals with chronic disease and in aged animals. METHODS: We utilized animal models of aging, CHF and EMP to evaluate the potential of CRF2R agonist treatment to maintain skeletal muscle mass and force production in aged animals and animals with CHF and EMP. RESULTS: In aged rats, we demonstrate that treatment with a CRF2R agonist for up to 3 months results in greater extensor digitorum longus (EDL) force production, EDL mass, soleus mass and soleus force production compared to age matched untreated animals. In the hamster EMP model, we demonstrate that treatment with a CRF2R agonist for up to 5 months results in greater EDL force production in EMP hamsters when compared to vehicle treated EMP hamsters and greater EDL mass and force in normal hamsters when compared to vehicle treated normal hamsters. In the rat CHF model, we demonstrate that treatment with a CRF2R agonist for up to 3 months results in greater EDL and soleus muscle mass and force production in CHF rats and normal rats when compared to the corresponding vehicle treated animals. CONCLUSIONS: These data demonstrate that the underlying physiological conditions associated with chronic diseases such as CHF and emphysema in addition to aging do not reduce the potential of CRF2R agonists to maintain skeletal muscle mass and force production.


Assuntos
Envelhecimento/efeitos dos fármacos , Contração Muscular/efeitos dos fármacos , Força Muscular/efeitos dos fármacos , Debilidade Muscular/tratamento farmacológico , Músculo Esquelético/efeitos dos fármacos , Peptídeos/uso terapêutico , Receptores de Hormônio Liberador da Corticotropina/agonistas , Envelhecimento/fisiologia , Animais , Doença Crônica , Cricetinae , Dinamarca , Modelos Animais de Doenças , Feminino , Masculino , Mesocricetus , Contração Muscular/fisiologia , Força Muscular/fisiologia , Debilidade Muscular/etiologia , Debilidade Muscular/fisiopatologia , Músculo Esquelético/fisiologia , Músculo Esquelético/fisiopatologia , Ratos , Ratos Endogâmicos F344 , Ratos Endogâmicos Lew , Receptores de Hormônio Liberador da Corticotropina/fisiologia
11.
Water Res ; 43(7): 1801-9, 2009 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-19232671

RESUMO

Ammonia oxidation is critical to global nitrogen cycling and is often thought to be driven only by ammonia-oxidizing bacteria. The recent finding of new ammonia-oxidizing organisms belonging to the archaeal domain challenges this perception. Two major microbial groups are now believed to be involved in ammonia oxidation: chemolithotrophic ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA). Candidatus "Nitrosopumilus maritimus", the first isolated ammonia-oxidizing archaeon from a tropical marine aquarium tank, representative of the ubiquitous marine group 1 Crenarchaeota, contains putative genes for all three subunits (amoA, amoB, and amoC) of ammonia monooxygenase, the key enzyme responsible for ammonia oxidation. In this article, important concepts of the nitrogen cycle, ammonia oxidation processes, ammonia-oxidizing organisms, and their physiology are described. AOA are found to thrive in various habitats including hot/thermal springs, marine and fresh waters, soils, and wastewater treatment systems, where they may outnumber their counterpart, AOB. Various molecular tools have been applied to study AOB and AOA and determine their abundance and community structure changes from natural and engineered systems. The presence of AOA in activated sludge opens new opportunities for elucidating its role of ammonia removal in wastewater treatment plants and wetlands. Several significant questions related to AOA research have been raised to evoke reader involvement for broadening future studies.


Assuntos
Amônia/metabolismo , Archaea/metabolismo , Nitrogênio/isolamento & purificação , Oxirredução
12.
BMC Med ; 5: 18, 2007 Jul 12.
Artigo em Inglês | MEDLINE | ID: mdl-17626629

RESUMO

BACKGROUND: Duchenne muscular dystrophy results from mutation of the dystrophin gene, causing skeletal and cardiac muscle loss of function. The mdx mouse model of Duchenne muscular dystrophy is widely utilized to evaluate the potential of therapeutic regimens to modulate the loss of skeletal muscle function associated with dystrophin mutation. Importantly, progressive loss of diaphragm function is the most consistent striated muscle effect observed in the mdx mouse model, which is the same as in patients suffering from Duchenne muscular dystrophy. METHODS: Using the mdx mouse model, we have evaluated the effect that corticotrophin releasing factor 2 receptor (CRF2R) agonist treatment has on diaphragm function, morphology and gene expression. RESULTS: We have observed that treatment with the potent CRF2R-selective agonist PG-873637 prevents the progressive loss of diaphragm specific force observed during aging of mdx mice. In addition, the combination of PG-873637 with glucocorticoids not only prevents the loss of diaphragm specific force over time, but also results in recovery of specific force. Pathological analysis of CRF2R agonist-treated diaphragm muscle demonstrates that treatment reduces fibrosis, immune cell infiltration, and muscle architectural disruption. Gene expression analysis of CRF2R-treated diaphragm muscle showed multiple gene expression changes including globally decreased immune cell-related gene expression, decreased extracellular matrix gene expression, increased metabolism-related gene expression, and, surprisingly, modulation of circadian rhythm gene expression. CONCLUSION: Together, these data demonstrate that CRF2R activation can prevent the progressive degeneration of diaphragm muscle associated with dystrophin gene mutation.


Assuntos
Distrofina/genética , Regulação da Expressão Gênica , Distrofia Muscular de Duchenne/genética , Distrofia Muscular de Duchenne/patologia , Receptores de Hormônio Liberador da Corticotropina/agonistas , Animais , Modelos Animais de Doenças , Progressão da Doença , Perfilação da Expressão Gênica , Masculino , Camundongos , Camundongos Endogâmicos mdx , Modelos Biológicos , Músculos/metabolismo , Mutação , Fatores de Tempo
13.
J Am Soc Mass Spectrom ; 17(6): 815-822, 2006 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-16616859

RESUMO

Mass Spectrometry (MS) has been widely reported for measuring the conversion of substrates to products for enzyme assays. These measurements are typically performed by time-consuming LC-MS to eliminate buffer salts that interfere with electrospray ionization MS. However, matrix-assisted laser desorption ionization, time-of-flight MS (MALDI-TOF MS) offers a label-free and direct readout of substrate and product, a fast sampling rate, and is tolerant of many buffer salts, reagents, and compounds that are typically found in enzyme reaction mixtures. In this report, a demonstration of how MALDI-TOF MS can be used to directly measure ratios of substrates and products to produce IC(50) curves for rapid enzyme assays and compound screening is provided. Typical reproducibility parameters were <7% RSD-a value comparable to ESI MS quantitative assays and well within the acceptable limits for screening assays. The speed of the MALDI readout is currently about 10 s per sample, thus allowing for over 7500 samples/day. From a simplicity standpoint, the enzymatic reaction mixtures are prepared by liquid handling robots, the reactions are stopped by addition of a 10 times volume of acidic matrix solution, and the samples are simultaneously transferred to MALDI target plate for analysis. Importantly, the ratios of substrate to product are of sufficient reproducibility to eliminate the need for internal standards and, thus, minimize the cost and increasing the speed of assay development.


Assuntos
Inibidores Enzimáticos/análise , Espectrometria de Massas por Ionização por Electrospray/métodos , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz/métodos , Inibidores Enzimáticos/metabolismo , Concentração Inibidora 50 , Oxigenases de Função Mista/antagonistas & inibidores , Oxigenases de Função Mista/metabolismo , Fosfotransferases/antagonistas & inibidores , Fosfotransferases/metabolismo , Reprodutibilidade dos Testes , Espectrometria de Massas em Tandem
14.
Peptides ; 27(7): 1806-13, 2006 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-16476507

RESUMO

Recently, we demonstrated that the corticotropin releasing factor 2 receptor agonist, urocortin 2, demonstrated anti-atrophy effects in rodent skeletal muscle atrophy models. Compared to other CRF2R agonists however, the in vivo pharmacological potency of urocortin 2 is poor when it is administered by continuous subcutaneous infusion. Therefore, we attempted to modify the structure of urocortin 2 to improve in vivo efficacy when administered by subcutaneous infusion. By substituting amino acid residues in the linker region of urocortin 2 (residues 22-32), we have demonstrated improved in vivo potency without altering selectivity, probably through reduced CRFBP binding. In addition, attempts to shorten urocortin 2 generally resulted in inactive peptides, demonstrating that the 38 amino acid urocortin 2 peptide is the minimal pharmacophore.


Assuntos
Hormônio Liberador da Corticotropina/química , Peptídeos/química , Sequência de Aminoácidos , Animais , Atrofia , Linhagem Celular , Linhagem Celular Tumoral , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Dados de Sequência Molecular , Ligação Proteica , Estrutura Terciária de Proteína , Ratos , Urocortinas
15.
Muscle Nerve ; 32(6): 775-81, 2005 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-16116651

RESUMO

Several GTP-binding protein (G-protein)-coupled receptors that signal through Galphas (GTP-binding protein alpha stimulatory) and the cyclic adenosine monophosphate (cAMP) pathway increase skeletal muscle mass. In order to further evaluate the role of the cAMP pathway in the regulation of skeletal muscle mass, we utilized inhibitors of phosphodiesterase 4 (PDE 4), the major cAMP-modifying PDE found in skeletal muscle, to modulate skeletal muscle cAMP levels. We found that PDE 4 inhibitors reduced the loss of muscle mass and force resulting from denervation and casting in rats and mice. These studies indicate that PDE 4 inhibitors may have a role in the treatment of skeletal muscle-wasting diseases.


Assuntos
3',5'-AMP Cíclico Fosfodiesterases/antagonistas & inibidores , Músculo Esquelético/efeitos dos fármacos , Atrofia Muscular/tratamento farmacológico , Inibidores de Fosfodiesterase/uso terapêutico , Agonistas Adrenérgicos beta/uso terapêutico , Análise de Variância , Animais , Clembuterol/uso terapêutico , Nucleotídeo Cíclico Fosfodiesterase do Tipo 4 , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Relação Dose-Resposta à Radiação , Estimulação Elétrica/métodos , Camundongos , Contração Muscular/efeitos dos fármacos , Denervação Muscular/métodos , Atrofia Muscular/etiologia , Ratos , Neuropatia Ciática/complicações , Neuropatia Ciática/tratamento farmacológico
16.
Mol Biosyst ; 1(3): 229-41, 2005 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-16880987

RESUMO

Skeletal muscle atrophy is a process in which protein degradation exceeds protein synthesis, resulting in a decrease of the muscle's physiological cross-sectional area and mass, and is often a serious consequence of numerous health problems. We used the isotope-coded affinity tag (ICAT) labelling approach and MS-MS to protein profile cytosolic subcellular fractions from mouse tibialis anterior skeletal muscle undergoing 0, 4, 8, or 16 days of immobilisation-induced atrophy. For the validation of peptide and protein identifications statistical algorithms were applied to the sequence database search results in order to obtain consistent sensitivity/error rates for protein and peptide identifications at each immobilisation time point. In this study, we identified and quantified a large number of mouse skeletal muscle proteins. At a protein probability (P) of P> or = 0.9 (corresponding to a false positive error rate of less than 1%) 807 proteins were identified (231, 226, 217 for 4, 8, 16 days of immobilisation and 133 for the control sample, respectively), from which 51 displayed altered protein abundance with atrophy. Due to randomness of data acquisition, a full time course could be generated only for 62 proteins, most of which displayed unchanged protein abundance. In spite of this, useful information about dataset characteristics and underlying biological processes could be obtained through gene over-representation analysis. 20 gene categories-mainly but not exclusively encoded by the subset of overlapping proteins--were consistently found to be significantly (p < 0.05) over-represented in all 4 sub-datasets.


Assuntos
Enzimas/genética , Proteínas Musculares/genética , Músculo Esquelético/patologia , Proteínas Adaptadoras de Transdução de Sinal , Animais , Atrofia , Proteínas de Ciclo Celular , Regulação da Expressão Gênica , Indicadores e Reagentes , Cinética , Masculino , Espectrometria de Massas , Camundongos , Camundongos Endogâmicos C57BL , Peptídeos/genética , Proteínas Repressoras , Fatores de Transcrição
17.
Biophys J ; 86(4): 2030-6, 2004 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-15041645

RESUMO

The protein matrix of an electron transfer protein creates an electrostatic environment for its redox site, which influences its electron transfer properties. Our studies of Fe-S proteins indicate that the protein is highly polarized around the redox site. Here, measures of deviations of the environmental electrostatic potential from a simple linear dielectric polarization response to the magnitude of the charge are proposed. In addition, a decomposition of the potential is proposed here to describe the apparent deviations from linearity, in which it is divided into a "permanent" component that is independent of the redox site charge and a dielectric component that linearly responds or polarizes to the charge. The nonlinearity measures and the decomposition were calculated for Clostridium pasteurianum rubredoxin from molecular dynamics simulations. The potential in rubredoxin is greater than expected from linear response theory, which implies it is a better electron acceptor than a redox site analog in a solvent with a dielectric constant equivalent to that of the protein. In addition, the potential in rubredoxin is described well by a permanent potential plus a linear response component. This permanent potential allows the protein matrix to create a favorable driving force with a low activation barrier for accepting electrons. The results here also suggest that the reduction potential of rubredoxin is determined mainly by the backbone and not the side chains, and that the redox site charge of rubredoxin may help to direct its folding.


Assuntos
Simulação por Computador , Proteínas Ferro-Enxofre/química , Rubredoxinas/química , Software , Proteínas de Bactérias , Clostridium/química , Transporte de Elétrons , Oxirredução , Conformação Proteica , Eletricidade Estática
18.
Biophys J ; 82(5): 2317-25, 2002 May.
Artigo em Inglês | MEDLINE | ID: mdl-11964222

RESUMO

We demonstrate the ease and utility of simulating heterogeneous interfacial systems with P2(1) and Pc periodic boundary conditions which allow, for example, lipids in a membrane to switch leaflets. In preliminary tests, P2(1) was shown to yield equivalent results to P1 in simulations of bulk water, a water/vacuum interface, and pure DPPC bilayers with an equal number of lipids per leaflet; equivalence of Pc and P1 was also demonstrated for the former two systems. P2(1) was further tested in simulations involving the spreading of an octane film on water, and equilibration of a DPPC bilayer from an initial condition containing different numbers of lipids in the two leaflets. Lastly, a simulation in P2(1) of a DOPC/melittin membrane showed significant passage of lipids to the melittin-containing leaflet from the initial distribution, and lends insight into the condensation of lipids by melittin.


Assuntos
Bicamadas Lipídicas/química , 1,2-Dipalmitoilfosfatidilcolina/química , Sítios de Ligação , Simulação por Computador , Membranas Artificiais , Modelos Moleculares , Conformação Molecular , Octanos/química , Fosfatidilcolinas/química , Software , Relação Estrutura-Atividade , Água/química
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