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1.
Epilepsy Behav ; 149: 109536, 2023 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-38008017

RESUMEN

BACKGROUND: A computer game-based epilepsy educational programme (Epigame) can potentially improve the awareness, knowledge and attitude (AKA) and quality of life (QOL) of children with epilepsy (CWE). Our study among Malaysian CWE aimed to assess the: i) baseline level of epilepsy AKA and potential characteristics associated with poor levels of AKA, ii) effectiveness of Epigame in improving AKA and QOL of CWE. METHOD: Prospective cohort study on CWE age 7-18 years old with no comorbidities. Epilepsy education was delivered using Epigame. CWE completed AKA questionnaire before (time point 1 [TP1]), immediately after (TP2), 3 months (TP3) after provision of Epigame. Child self-report Health-Related Quality of Life Measurement for Children with Epilepsy (CHEQOL-25) questionnaire was completed at TP1 and TP3. RESULTS: Total of 106 CWE participated in this study (mean age of 13.3 years). Baseline (TP1) AKA was rated "very low to moderate" for awareness domain in 95.3 %, "very low to moderate" for knowledge domain in 67 %, "negative to indifferent" for attitude domain in 54.7 %, and "very poor to moderate' for total AKA score domain in 84 %. "Positive to very positive" for child attitude domain was significantly associated with parents with "positive to very positive" for attitude domain (OR 10.6, 95 % CI 3.23-34.66). "Good to excellent" for total child AKA domain was significantly associated with parents with "Good to excellent" for total AKA domain (OR 5.2, 95 % CI 1.16-15.02) and with < 2 antiseizure medication (OR 5.0, 95 % CI 1.34-18.98). The scores in the knowledge, attitude and total AKA score domains improved significantly after the introduction of Epigame at TP3. There were no significant improvements in the CHEQOL-25 scores over time except for the "Quest for Normality" subscale score (mean of score difference between TP1 and TP3 = 1.0, 95 % CI 0.19-1.81). CONCLUSION: Majority of Malaysian CWE had low levels of epilepsy AKA, particularly among parents with "negative to indifferent" for attitude domain, parents with "very poor to moderate" for total AKA domain and on polytherapy. Introduction of Epigame was effective in improving scores of the knowledge, attitude and total AKA domains, and the QOL "Quest for Normality" domain of the CHEQOL-25.


Asunto(s)
Epilepsia , Juegos de Video , Niño , Humanos , Adolescente , Calidad de Vida , Estudios Prospectivos , Epilepsia/terapia , Epilepsia/epidemiología , Comorbilidad
2.
Dev Med Child Neurol ; 64(8): 1025-1033, 2022 08.
Artículo en Inglés | MEDLINE | ID: mdl-35213736

RESUMEN

AIM: To evaluate parental perception of advance care plan (ACP) discussions in families of Malaysian children with bilateral cerebral palsy (CP) classified in Gross Motor Function Classification System levels IV or V for (1) acceptance of the ACP discussion, (2) feedback on the usefulness of ACP discussion, and (3) exploration of possible factors related to parental acceptance of ACP. METHOD: This was a prospective pre- and post-ACP discussion questionnaire study for parents of children with bilateral CP. RESULTS: Sixty-nine patients were recruited to the study; 64 (93%) had at least one additional comorbidity. The median age was 8 years (interquartile range 5 years 1 month-11 years 6 months). Fifty-seven (82.6%) parents found the ACP discussion acceptable, and most reported positive feedback on various components of the discussion (88.4-97.1%). One-third of participants were not comfortable discussing end-of-life care plans. On multivariate analysis, parents who were comfortable discussing end-of-life care plans were more likely to find the ACP discussion acceptable (odds ratio 27.78, 95% confidence interval 2.9-265.1, p = 0.004). INTERPRETATION: Most parents of Malaysian children with bilateral CP reported the ACP discussion as both acceptable and beneficial. Parents need to be comfortable about discussing end-of-life care plans for their child to enable the ACP discussion to be an acceptable experience.


DISCUSIÓN SOBRE EL PLAN ANTICIPADO DE CUIDADOS CON PADRES DE NIÑOS CON PARÁLISIS CEREBRAL: OBJETIVO: Evaluar la percepción parental al discutir el Plan Anticipado de Cuidados (PAC) en familias de niños Malasios con parálisis cerebral bilateral (PC) niveles IV o V según el Sistema de Clasificación de la Función Motora Gruesa (GMFCS) para 1) Aceptación de la propuesta sobre el PAC, 2) opinión sobre la utilidad de discusión sobre el PAC y 3) exploración de posibles factores relacionados a la aceptación parental del PAC. MÉTODO: Se utilizó un estudio prospectivo con un cuestionario pre y post discusión sobre el PAC con padres de niños con PC bilateral. RESULTADOS: Se reclutaron sesenta y nueve pacientes para este estudio; 64 (93%) tenían como mínimo una comorbilidad adicional. La edad mediana fue 8 años (rango intercuartilo 5 años y 1 mes - 11 años y 6 meses). Cincuenta y siete (82,6%) padres hallaron aceptable la discusión sobre el PAC y la mayoría reportó una opinión positiva sobre varios componentes de la discusión (88,4 - 97,1%). Un tercio de los participantes no se sintieron bien discutiendo planes sobre cuidados del paciente terminal. Utilizando análisis multivariable, los padres que se sintieron cómodos discutiendo planes sobre cuidados del paciente terminal, con mayor probabilidad hallaron aceptable la discusión sobre el PAC (relación de probabilidades 27,78 (95%) Intervalo de confidencia 2,9-265,1, p=0,004). INTERPRETACIÓN: La mayoría de los padres de niños Malasios con PC bilateral reportaron la discusión sobre el PAC como aceptable y beneficioso. Los padres necesitan sentirse cómodos discutiendo planes sobre cuidados del paciente con múltiples comorbilidades, referidos a su hijo, a fin de permitir que la discusión sobre el PAC sea una experiencia aceptable.


Asunto(s)
Planificación Anticipada de Atención , Parálisis Cerebral , Parálisis Cerebral/terapia , Niño , Familia , Humanos , Lactante , Padres , Estudios Prospectivos
3.
Cochrane Database Syst Rev ; 8: CD011786, 2021 08 16.
Artículo en Inglés | MEDLINE | ID: mdl-34397100

RESUMEN

BACKGROUND: This is an updated version of a Cochrane Review published in 2017. Paediatric neurodiagnostic investigations, including brain neuroimaging and electroencephalography (EEG), play an important role in the assessment of neurodevelopmental disorders. The use of an appropriate sedative agent is important to ensure the successful completion of the neurodiagnostic procedures, particularly in children, who are usually unable to remain still throughout the procedure. OBJECTIVES: To assess the effectiveness and adverse effects of chloral hydrate as a sedative agent for non-invasive neurodiagnostic procedures in children. SEARCH METHODS: We searched the following databases on 14 May 2020, with no language restrictions: the Cochrane Register of Studies (CRS Web) and MEDLINE (Ovid, 1946 to 12 May 2020). CRS Web includes randomised or quasi-randomised controlled trials from PubMed, Embase, ClinicalTrials.gov, the World Health Organization International Clinical Trials Registry Platform, the Cochrane Central Register of Controlled Trials (CENTRAL), and the specialised registers of Cochrane Review Groups including Cochrane Epilepsy. SELECTION CRITERIA: Randomised controlled trials that assessed chloral hydrate agent against other sedative agent(s), non-drug agent(s), or placebo. DATA COLLECTION AND ANALYSIS: Two review authors independently evaluated studies identified by the search for their eligibility, extracted data, and assessed risk of bias. Results were expressed in terms of risk ratio (RR) for dichotomous data and mean difference (MD) for continuous data, with 95% confidence intervals (CIs). MAIN RESULTS: We included 16 studies with a total of 2922 children. The methodological quality of the included studies was mixed. Blinding of the participants and personnel was not achieved in most of the included studies, and three of the 16 studies were at high risk of bias for selective reporting. Evaluation of the efficacy of the sedative agents was also underpowered, with all the comparisons performed in small studies. Fewer children who received oral chloral hydrate had sedation failure compared with oral promethazine (RR 0.11, 95% CI 0.01 to 0.82; 1 study; moderate-certainty evidence). More children who received oral chloral hydrate had sedation failure after one dose compared to intravenous pentobarbital (RR 4.33, 95% CI 1.35 to 13.89; 1 study; low-certainty evidence), but there was no clear difference after two doses (RR 3.00, 95% CI 0.33 to 27.46; 1 study; very low-certainty evidence). Children with oral chloral hydrate had more sedation failure compared with rectal sodium thiopental (RR 1.33, 95% CI 0.60 to 2.96; 1 study; moderate-certainty evidence) and music therapy (RR 17.00, 95% CI 2.37 to 122.14; 1 study; very low-certainty evidence). Sedation failure rates were similar between groups for comparisons with oral dexmedetomidine, oral hydroxyzine hydrochloride, oral midazolam and oral clonidine. Children who received oral chloral hydrate had a shorter time to adequate sedation compared with those who received oral dexmedetomidine (MD -3.86, 95% CI -5.12 to -2.6; 1 study), oral hydroxyzine hydrochloride (MD -7.5, 95% CI -7.85 to -7.15; 1 study), oral promethazine (MD -12.11, 95% CI -18.48 to -5.74; 1 study) (moderate-certainty evidence for three aforementioned outcomes), rectal midazolam (MD -95.70, 95% CI -114.51 to -76.89; 1 study), and oral clonidine (MD -37.48, 95% CI -55.97 to -18.99; 1 study) (low-certainty evidence for two aforementioned outcomes). However, children with oral chloral hydrate took longer to achieve adequate sedation when compared with intravenous pentobarbital (MD 19, 95% CI 16.61 to 21.39; 1 study; low-certainty evidence), intranasal midazolam (MD 12.83, 95% CI 7.22 to 18.44; 1 study; moderate-certainty evidence), and intranasal dexmedetomidine (MD 2.80, 95% CI 0.77 to 4.83; 1 study, moderate-certainty evidence). Children who received oral chloral hydrate appeared significantly less likely to complete neurodiagnostic procedure with child awakening when compared with rectal sodium thiopental (RR 0.95, 95% CI 0.83 to 1.09; 1 study; moderate-certainty evidence). Chloral hydrate was associated with a higher risk of the following adverse events: desaturation versus rectal sodium thiopental (RR 5.00, 95% 0.24 to 102.30; 1 study), unsteadiness versus intranasal dexmedetomidine (MD 10.21, 95% CI 0.58 to 178.52; 1 study), vomiting versus intranasal dexmedetomidine (MD 10.59, 95% CI 0.61 to 185.45; 1 study) (low-certainty evidence for aforementioned three outcomes), and crying during administration of sedation versus intranasal dexmedetomidine (MD 1.39, 95% CI 1.08 to 1.80; 1 study, moderate-certainty evidence). Chloral hydrate was associated with a lower risk of the following: diarrhoea compared with rectal sodium thiopental (RR 0.04, 95% CI 0.00 to 0.72; 1 study), lower mean diastolic blood pressure compared with sodium thiopental (MD 7.40, 95% CI 5.11 to 9.69; 1 study), drowsiness compared with oral clonidine (RR 0.44, 95% CI 0.30 to 0.64; 1 study), vertigo compared with oral clonidine (RR 0.15, 95% CI 0.01 to 2.79; 1 study) (moderate-certainty evidence for aforementioned four outcomes), and bradycardia compared with intranasal dexmedetomidine (MD 0.17, 95% CI 0.05 to 0.59; 1 study; high-certainty evidence). No other adverse events were significantly associated with chloral hydrate, although there was an increased risk of combined adverse events overall (RR 7.66, 95% CI 1.78 to 32.91; 1 study; low-certainty evidence). AUTHORS' CONCLUSIONS: The certainty of evidence for the comparisons of oral chloral hydrate against several other methods of sedation was variable. Oral chloral hydrate appears to have a lower sedation failure rate when compared with oral promethazine. Sedation failure was similar between groups for other comparisons such as oral dexmedetomidine, oral hydroxyzine hydrochloride, and oral midazolam. Oral chloral hydrate had a higher sedation failure rate when compared with intravenous pentobarbital, rectal sodium thiopental, and music therapy. Chloral hydrate appeared to be associated with higher rates of adverse events than intranasal dexmedetomidine. However, the evidence for the outcomes for oral chloral hydrate versus intravenous pentobarbital, rectal sodium thiopental, intranasal dexmedetomidine, and music therapy was mostly of low certainty, therefore the findings should be interpreted with caution. Further research should determine the effects of oral chloral hydrate on major clinical outcomes such as successful completion of procedures, requirements for an additional sedative agent, and degree of sedation measured using validated scales, which were rarely assessed in the studies included in this review. The safety profile of chloral hydrate should be studied further, especially for major adverse effects such as oxygen desaturation.


Asunto(s)
Hidrato de Cloral/administración & dosificación , Técnicas de Diagnóstico Neurológico , Hipnóticos y Sedantes/administración & dosificación , Niño , Hidrato de Cloral/efectos adversos , Humanos , Hidroxizina/administración & dosificación , Hipnóticos y Sedantes/efectos adversos , Midazolam/administración & dosificación , Midazolam/efectos adversos , Pentobarbital/administración & dosificación
4.
Brain Dev ; 43(4): 538-547, 2021 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-33358123

RESUMEN

OBJECTIVE: Describe the outcome of a Malaysian cohort of children with acute necrotising encephalopathy (ANE). METHOD: Retrospective study of children with ANE seen at University of Malaya Medical Centre from 2014 to 2019. All clinical details including ANE-severity score (ANE-SS), immunomodulation treatment and neurodevelopmental long-term outcome were collected. RESULTS: Thirteen patients had ANE and brainstem death occurred in 5. In 10 patients (77%) viruses were isolated contributing to ANE: 8 influenza virus, 1 acute dengue infection, and 1 acute varicella zoster infection. The ANE-SS ranged 2-7: 9 were high risk and 4 were medium risk. Among the 8 survivors; 1 was lost to follow-up. Follow-up duration was 1-6 years (median 2.2). At follow-up among the 4 high-risk ANE-SS: 2 who were in a vegetative state, 1 remained unchanged and 1 improved to severe disability; the other 2 with severe disability improved to moderate and mild disability respectively. At follow-up all 3 medium-risk ANE-SS improved: 2 with severe disability improved to moderate and mild disability respectively, while 1 in a vegetative state improved to severe disability. Early treatment with immunomodulation did not affect outcome. CONCLUSION: Our ANE series reiterates that ANE is a serious cause of encephalopathy with mortality of 38.5%. All survivors were in a vegetative state or had severe disability at discharge. Most of the survivors made a degree of recovery but good recovery was seen in 2. Follow-up of at least 12 months is recommended for accurate prognostication. Dengue virus infection needs to be considered in dengue endemic areas.


Asunto(s)
Antibacterianos/uso terapéutico , Encéfalo/diagnóstico por imagen , Leucoencefalitis Hemorrágica Aguda/tratamiento farmacológico , Metilprednisolona/uso terapéutico , Niño , Preescolar , Femenino , Glucocorticoides/uso terapéutico , Humanos , Leucoencefalitis Hemorrágica Aguda/diagnóstico por imagen , Leucoencefalitis Hemorrágica Aguda/mortalidad , Malasia/epidemiología , Masculino , Atención al Paciente , Estudios Retrospectivos , Tasa de Supervivencia , Resultado del Tratamiento
5.
J Clin Neurosci ; 64: 11-14, 2019 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-30948308

RESUMEN

We report a rare case of distinctive extensive punctate intracranial haemorrhage associated with acute lymphoblastic leukaemia with hyperleukocytosis. A 7-year-old girl presented with hyperleukocytosis (white cell count 788.7 × 109/L; 94% peripheral blasts) and laboratory tumour lysis syndrome. The diagnosis of T-cell acute lymphoblastic leukaemia was established and confirmed by immunophenotyping of peripheral blood and chemotherapy was commenced promptly. On day 3 of treatment, she developed progressive encephalopathy, left sided hemiparesis with left 6th and upper motor neuron 7th cranial nerve palsy. Brain MRI scan showed extensive punctate haemorrhages with perilesional oedema over the frontal, parietal, occipital, temporal, brainstem and cerebellar regions. The lesions were predominantly over the juxtacortical grey matter. She made a full neurological recovery after 3 months. Our report widens the neuroradiological features of intracranial haemorrhage associated with hyperleukocytosis and highlights the importance of prompt chemotherapy in these patients.


Asunto(s)
Hemorragias Intracraneales/etiología , Leucemia-Linfoma Linfoblástico de Células Precursoras/complicaciones , Niño , Femenino , Humanos , Leucocitosis/etiología , Imagen por Resonancia Magnética , Leucemia-Linfoma Linfoblástico de Células Precursoras/tratamiento farmacológico
6.
Epilepsy Behav ; 94: 52-58, 2019 05.
Artículo en Inglés | MEDLINE | ID: mdl-30884408

RESUMEN

BACKGROUND: An information technology (IT)-based epilepsy educational program, the Interactive Animated Epilepsy Education Programme (IAEEP), can potentially help improve awareness, knowledge, and attitude (AKA) of parents of children with epilepsy (CWE) enabling CWE to lead a normal life. Our study aimed to assess the following: i) baseline level of epilepsy AKA of Malaysian parents of CWE and explore potential characteristics associated with low levels of AKA; ii) effectiveness of the IAEEP in improving parental AKA, and whether these effects remained stable over time; and iii) effects of the IAEEP on parental mental state and perception of their child's quality of life. METHODS: This prospective study includes parents of CWE aged 8-18 years old with no comorbidities. Epilepsy education was delivered using the IAEEP. Parents completed an AKA questionnaire before (time point 1 [TP1]), immediately after (TP2), and 4-6 months (TP3) after the provision of IAEEP. Parent proxy report of Health-Related Quality of Life Measurement for Children with Epilepsy (CHEQOL)-25 questionnaire and Depression, Anxiety, and Stress Scale (DASS)-21 questionnaire was completed at TP1 and TP3. RESULTS: A total of 78 parents participated in the study. At baseline (TP1), parental responses were rated as "moderate" for awareness domain, "high" for knowledge domain, "very positive" for attitude domain, and "good" for total AKA score domain. No epilepsy or parental characteristics were associated with the low baseline parental AKA levels. After IAEEP intervention, there was a significant increase in all AKA subdomain scores. Post-IAEEP, the AKA of parents were rated as "very high" for awareness domain, "very high" for knowledge domain, "very positive" for attitude domain, and "excellent" for total AKA domain at both TP2 and TP3. Parent proxy CHEQOL-25 report showed significant increments in interpersonal/social and secrecy scale scores between TP1 and TP3. There were no significant differences in the DASS-21 scores between TP1 and TP3. CONCLUSION: The IAEEP is an effective epilepsy educational tool to increase the levels of AKA among parents of CWE. Following the use of the IAEEP, parents of CWE also reported an improvement of their child's quality of life in the interpersonal/social and epilepsy secrecy CHEQOL-25 domains. There was no impact on parental mental health following exposure to the IAEEP.


Asunto(s)
Epilepsia/psicología , Conocimientos, Actitudes y Práctica en Salud , Padres/educación , Educación del Paciente como Asunto/métodos , Adolescente , Adulto , Niño , Comorbilidad , Depresión , Femenino , Humanos , Masculino , Persona de Mediana Edad , Estudios Prospectivos , Calidad de Vida/psicología , Encuestas y Cuestionarios , Adulto Joven
7.
Epilepsy Behav ; 75: 6-12, 2017 10.
Artículo en Inglés | MEDLINE | ID: mdl-28806633

RESUMEN

Sudden unexpected death in epilepsy (SUDEP) is an important cause of mortality in epilepsy. To date, there is only one published UK study evaluating information provision of SUDEP among parents of children with epilepsy (CWE), and there are no studies published from Asia. Although SUDEP information provision is recommended among parents of CWE, it is uncertain if these recommendations are applicable to Asian countries due to the different cultural attitude towards epilepsy. Our prospective cohort study consisted of multiethnic parents of children with epilepsy (CWE) seen in a tertiary hospital in Malaysia. Information on SUDEP was delivered to parents using an epilepsy educational software program. Participants completed a set of standardized questionnaire and Depression Anxiety Stress Scales-Short Form (DASS-21) immediately after and retested 3-6months after the SUDEP information provision. A total of 127 parents (84 mothers) participated in the study. The CWE consisted of 3 ethnic groups (38% Malay, 30% Chinese, 32% Indian) with a mean age of 9.6years. Majority (70.9%) felt positive after SUDEP information provision, 90.6% wanted SUDEP discussion for themselves with 70.1% wanted SUDEP discussion with their child, and a lower proportion (58.3%) would discuss SUDEP with their child. None of the participants reported increased symptoms of depression, stress or anxiety attributed to SUDEP information provision. Most parents took steps to reduce SUDEP risk, and most parents did not report an impact on their own functioning. However, there was an increase in parental report over time of impact on their child's functioning following SUDEP information (P<0.05). In conclusion, most Malaysian parents of CWE wanted SUDEP information. Following SUDEP information disclosure, majority did not report negative emotions; however, an increase in parents over time reported an impact on their child. Our findings reiterate that provision of SUDEP information should form part of care of CWE and parents should receive ongoing support as they undergo a period of parenting adjustment when dealing with the information provided.


Asunto(s)
Muerte Súbita/etnología , Revelación , Epilepsia/etnología , Conocimientos, Actitudes y Práctica en Salud/etnología , Conducta en la Búsqueda de Información , Padres/psicología , Adulto , Niño , Femenino , Humanos , Malasia/etnología , Masculino , Estudios Prospectivos , Factores de Riesgo
8.
J Clin Neurosci ; 36: 73-75, 2017 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-27887978

RESUMEN

A 14-year-old girl presented with encephalopathy, delirium and ophthalmoplegia following a 3day history of high-grade fever. Brain MRI on day 6 of illness showed diffusion restricted ovoid lesion in the splenium of corpus callosum. Dengue virus encephalitis was diagnosed with positive PCR for dengue virus type-2 in both serum and cerebrospinal fluid. She made a complete recovery from day 10 of illness. Repeat brain MRI on day 12 of illness showed resolution of the splenial lesion. Serial diffusion tensor imaging (DTI) showed normal fractional anisotropy values on resolution of splenial lesion indicating that MERS was likely due to transient interstitial oedema with preservation of white matter tracts. This is the first reported case of MERS following dengue virus infection. It highlights the usefulness of performing serial DTI in understanding the underlying pathogenesis of MERS. Our case report widens the neurological manifestations associated with dengue infection and reiterates that patients with MERS should be managed supportively as the splenial white matter tracts are reversibly involved in MERS.


Asunto(s)
Dengue/complicaciones , Encefalitis Viral/diagnóstico por imagen , Adolescente , Cuerpo Calloso/diagnóstico por imagen , Imagen de Difusión Tensora , Encefalitis Viral/etiología , Encefalitis Viral/patología , Femenino , Humanos , Imagen por Resonancia Magnética , Bazo/patología
9.
J Chem Phys ; 144(2): 024904, 2016 Jan 14.
Artículo en Inglés | MEDLINE | ID: mdl-26772587

RESUMEN

Depletion forces and macromolecular crowding govern the structure and function of biopolymers in biological cells and the properties of polymer nanocomposite materials. To isolate and analyze the influence of polymer shape fluctuations and penetrability on depletion-induced interactions and crowding by nanoparticles, we model polymers as effective penetrable ellipsoids, whose shapes fluctuate according to the probability distributions of the eigenvalues of the gyration tensor of an ideal random walk. Within this model, we apply Monte Carlo simulation methods to compute the depletion-induced potential of mean force between hard nanospheres and crowding-induced shape distributions of polymers in the protein limit, in which polymer coils can be easily penetrated by smaller nanospheres. By comparing depletion potentials from simulations of ellipsoidal and spherical polymer models with predictions of polymer field theory and free-volume theory, we show that polymer depletion-induced interactions and crowding depend sensitively on polymer shapes and penetrability, with important implications for bulk thermodynamic phase behavior.


Asunto(s)
Nanosferas/química , Polímeros/química , Modelos Químicos , Método de Montecarlo , Tamaño de la Partícula
10.
Soft Matter ; 12(8): 2247-52, 2016 Feb 28.
Artículo en Inglés | MEDLINE | ID: mdl-26689367

RESUMEN

Depletion-induced interactions between colloids in colloid-polymer mixtures depend in range and strength on size, shape, and concentration of depletants. Crowding by colloids in turn affects shapes of polymer coils, such as biopolymers in biological cells. By simulating hard-sphere colloids and random-walk polymers, modeled as fluctuating ellipsoids, we compute depletion-induced potentials and polymer shape distributions. Comparing results with exact density-functional theory calculations, molecular simulations, and experiments, we show that polymer shape fluctuations play an important role in depletion and crowding phenomena.

11.
J Chem Phys ; 141(11): 114909, 2014 Sep 21.
Artículo en Inglés | MEDLINE | ID: mdl-25240374

RESUMEN

Macromolecular crowding can influence polymer shapes, which is important for understanding the thermodynamic stability of polymer solutions and the structure and function of biopolymers (proteins, RNA, DNA) under confinement. We explore the influence of nanoparticle crowding on polymer shapes via Monte Carlo simulations and free-volume theory of a coarse-grained model of polymer-nanoparticle mixtures. Exploiting the geometry of random walks, we model polymer coils as effective penetrable ellipsoids, whose shapes fluctuate according to the probability distributions of the eigenvalues of the gyration tensor. Accounting for the entropic cost of a nanoparticle penetrating a larger polymer coil, we compute the crowding-induced shift in the shape distributions, radius of gyration, and asphericity of ideal polymers in a theta solvent. With increased nanoparticle crowding, we find that polymers become more compact (smaller, more spherical), in agreement with predictions of free-volume theory. Our approach can be easily extended to nonideal polymers in good solvents and used to model conformations of biopolymers in crowded environments.


Asunto(s)
Nanopartículas/química , Polímeros/química , Modelos Teóricos
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