Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 54
Filtrar
1.
Proc Natl Acad Sci U S A ; 121(37): e2410280121, 2024 Sep 10.
Artículo en Inglés | MEDLINE | ID: mdl-39226343

RESUMEN

We present Einstein coefficient spectra and a detailed-balance derivation of generalized Einstein relations between them that is based on the connection between spontaneous and stimulated emission. If two broadened levels or bands overlap in energy, transitions between them need not be purely absorptive or emissive. Consequently, spontaneous emission can occur in both transition directions, and four Einstein coefficient spectra replace the three Einstein coefficients for a line. At equilibrium, the four different spectra obey five pairwise relationships and one lineshape generates all four. These relationships are independent of molecular quantum statistics and predict the Stokes' shift between forward and reverse transitions required by equilibrium with blackbody radiation. For Boltzmann statistics, the relative strengths of forward and reverse transitions depend on the formal chemical potential difference between the initial and final bands, which becomes the standard chemical potential difference for ideal solutes. The formal chemical potential of a band replaces both the energy and degeneracy of a quantum level. Like the energies of quantum levels, the formal chemical potentials of bands obey the Rydberg-Ritz combination principle. Each stimulated Einstein coefficient spectrum gives a frequency-dependent transition cross-section. Transition cross-sections obey causality and a detailed-balance condition with spontaneous emission, but do not directly obey generalized Einstein relations. Even with an energetic width much less than the photon energy, a predominantly absorptive forward transition with an energetic width much greater than the thermal energy can have such an extreme Stokes' shift that its reverse transition cross-section becomes predominantly absorptive rather than emissive.

2.
Chem Rev ; 123(12): 7890-7952, 2023 Jun 28.
Artículo en Inglés | MEDLINE | ID: mdl-37311205

RESUMEN

Solution-processed semiconductors are in demand for present and next-generation optoelectronic technologies ranging from displays to quantum light sources because of their scalability and ease of integration into devices with diverse form factors. One of the central requirements for semiconductors used in these applications is a narrow photoluminescence (PL) line width. Narrow emission line widths are needed to ensure both color and single-photon purity, raising the question of what design rules are needed to obtain narrow emission from semiconductors made in solution. In this review, we first examine the requirements for colloidal emitters for a variety of applications including light-emitting diodes, photodetectors, lasers, and quantum information science. Next, we will delve into the sources of spectral broadening, including "homogeneous" broadening from dynamical broadening mechanisms in single-particle spectra, heterogeneous broadening from static structural differences in ensemble spectra, and spectral diffusion. Then, we compare the current state of the art in terms of emission line width for a variety of colloidal materials including II-VI quantum dots (QDs) and nanoplatelets, III-V QDs, alloyed QDs, metal-halide perovskites including nanocrystals and 2D structures, doped nanocrystals, and, finally, as a point of comparison, organic molecules. We end with some conclusions and connections, including an outline of promising paths forward.

3.
BMC Public Health ; 23(1): 331, 2023 02 14.
Artículo en Inglés | MEDLINE | ID: mdl-36788515

RESUMEN

BACKGROUND: Health literacy, defined as the knowledge, motivation, and competences to use health information to improve health and well-being, is associated with regular physical activity. However, there is limited evidence on whether health literacy is also related to the motivational readiness for physical activity in a general population. The aim of this study was to investigate whether motivational readiness for leisure-time physical activity is associated with health literacy. METHODS: Analyses were based on data of 21,895 adults from the cross-sectional German Health Update and European Health Interview Survey 2014/2015 (GEDA 2014/2015-EHIS). Motivational readiness for leisure-time physical activity was assessed with stages of change for physical activity with a set of validated items. It was then classified, according to an established algorithm, into five stages: precontemplation, contemplation, preparation, action, and maintenance. Health literacy was measured with the short form of the European Health Literacy Survey Questionnaire (HLS-EU-Q16) and categorised as low, medium, and high. For bivariate and multinomial logistic regression analyses, the stages were categorised in three phases as: (1) no intention (precontemplation), (2) planning (contemplation or preparation), and (3) in activity (action or maintenance). The models were adjusted for sex, age, education, health consciousness, self-efficacy, and self-perceived general health status. RESULTS: High compared to low health literacy was associated with a 1.65-times (95% CI = 1.39-1.96) greater probability of being in activity than planning. High compared to low health literacy was associated with a reduced risk of having no intention to change physical activity behaviour (relative risk ratio, RRR = 0.84, 95% CI = 0.75-0.95). The associations persisted after adjusting for covariates. CONCLUSION: High health literacy was positively associated with more advanced phases of motivational readiness for leisure-time physical activity. Therefore, taking health literacy into account in interventions to promote motivational readiness for leisure-time physical activity could be a useful approach.


Asunto(s)
Alfabetización en Salud , Motivación , Humanos , Adulto , Estudios Transversales , Ejercicio Físico , Encuestas y Cuestionarios , Alemania
4.
Geroscience ; 44(3): 1269-1293, 2022 06.
Artículo en Inglés | MEDLINE | ID: mdl-35288843

RESUMEN

Dogs may possess a unique translational potential to investigate neural aging and dementia because they are prone to age-related cognitive decline, including an Alzheimer's disease-like pathological condition. Yet very little is known about the molecular mechanisms underlying canine cognitive decline. The goal of the current study was to explore the transcriptomic differences between young and old dogs' frontal cortex, which is a brain region often affected by various forms of age-related dementia in humans. RNA isolates from the frontal cortical brain area of 13 pet dogs, which represented 7 different breeds and crossbreds, were analyzed. The dogs were euthanized for medical reasons, and their bodies had been donated by their owners for scientific purposes. The poly(A) tail RNA subfraction of the total transcriptome was targeted in the sequencing analysis. Cluster analyses, differential gene expression analyses, and gene ontology analyses were carried out to assess which genes and genetic regulatory mechanisms were mostly affected by aging. Age was the most prominent factor in the clustering of the animals, indicating the presence of distinct gene expression patterns related to aging in a genetically variable population. A total of 3436 genes were found to be differentially expressed between the age groups, many of which were linked to neural function, immune system, and protein synthesis. These findings are in accordance with previous human brain aging RNA sequencing studies. Some genes were found to behave more similarly to humans than to rodents, further supporting the applicability of dogs in translational aging research.


Asunto(s)
Enfermedad de Alzheimer , Corteza Prefrontal , Envejecimiento/metabolismo , Enfermedad de Alzheimer/genética , Animales , Perros , Corteza Prefrontal/metabolismo , ARN/genética , ARN/metabolismo , ARN Mensajero/metabolismo , Análisis de Secuencia de ARN
5.
Sci Adv ; 7(22)2021 May.
Artículo en Inglés | MEDLINE | ID: mdl-34049871

RESUMEN

For quantum-confined nanomaterials, size dispersion causes a static broadening of spectra that has been difficult to measure and invalidates all-optical methods for determining the maximum photovoltage that an excited state can generate. Using femtosecond two-dimensional (2D) spectroscopy to separate size dispersion broadening of absorption and emission spectra allows a test of single-molecule generalized Einstein relations between such spectra for colloidal PbS quantum dots. We show that 2D spectra and these relations determine the thermodynamic standard chemical potential difference between the lowest excited and ground electronic states, which gives the maximum photovoltage. Further, we find that the static line broadening from many slightly different quantum dot structures allows single-molecule generalized Einstein relations to determine the average single-molecule linewidth from Stokes' frequency shift between ensemble absorption and emission spectra.

6.
J Sport Health Sci ; 10(4): 439-446, 2021 07.
Artículo en Inglés | MEDLINE | ID: mdl-32738519

RESUMEN

BACKGROUND: Physical activity is favorable for health, and vigorous sports activity is particularly beneficial. This study investigates the association between changes in sports participation patterns over time and cardio-metabolic and self-perceived health outcomes. METHODS: Data from 3752 adults (18-79 years of age) who participated in 2 national health interview and examination surveys in 1997-1999 and 2008-2011 were included, with a mean follow-up time of about 12 years. A change in self-reported sports activity was analyzed with respect to the incidence of type 2 diabetes, coronary heart disease (CHD), hypertension, obesity, dyslipidemia, metabolic syndrome, and poor self-perceived health. Participants with pre-existing disease or risk factor of interest at baseline were excluded from the analysis. Being sufficiently active in sports was specified as doing sports for at least 1-2 h per week, and 4 activity categories were defined: 1) inactive at both time points (inactive-inactive), 2) inactive at baseline and active at follow-up (inactive-active), 3) active at baseline and inactive at follow-up (active-inactive), and 4) active at both time points (active-active). Associations between sports activity engagement and health outcomes were estimated by logistic regression models with different stages of adjustments. RESULTS: Not engaging in any regular sports activity at both time points (inactive-inactive) was associated with higher rates of type 2 diabetes (odds ratio (OR) = 1.82, 95% confidence interval (95%CI): 1.08-3.08), CHD (OR = 1.82, 95%CI: 1.16-2.84), hypertension (OR = 1.36, 95%CI: 1.03-1.81), metabolic syndrome (OR = 1.58, 95%CI: 1.08-2.32), and poor self-perceived health (OR = 2.54, 95%CI: 1.83-3.53) compared to doing regular sports for a minimum of 1-2 h per week over time (active-active). In case of change from inactivity to any regular sports activity (inactive-active), the rate of risk factor occurrence was not statistically different from the active-active reference group except for poor self-perceived health, but it was higher for type 2 diabetes (OR = 2.15, 95%CI: 1.12-4.14) and CHD (OR = 1.77, 95%CI: 1.03-3.03). Being active at baseline but inactive at follow-up (active-inactive) was not associated with higher disease incidence of type 2 diabetes (OR = 0.70, 95%CI: 0.25-1.97) or CHD (OR = 1.20, 95%CI: 0.49-2.99), but was associated with higher rates of hypertension (OR = 1.61, 95%CI: 1.11-2.34), obesity (OR = 2.34, 95%CI: 1.53-3.57), metabolic syndrome (OR = 1.70, 95%CI: 1.11-2.63), and poor self-perceived health (OR = 2.16, 95%CI: 1.53-3.07) at follow-up. CONCLUSION: Even a low weekly quantity (1-2 h) of regular sports activity is partly associated with health benefits. Being formerly but not currently active was not associated with an increased disease incidence, but was associated with a higher risk-factor development compared to the reference group (active-active). Becoming active was preventive for risk-factor development but was not preventive for disease incidence, which probably means that the health benefits from sports activity are not sustainable and disease incidence is only shifted to a later period in life. For this reason, the promotion of and commitment to regular sports activity should be addressed as early as possible over the lifespan to achieve the best health benefits.


Asunto(s)
Ejercicio Físico/fisiología , Enfermedades no Transmisibles/epidemiología , Conducta Sedentaria , Deportes/fisiología , Adolescente , Adulto , Anciano , Femenino , Estudios de Seguimiento , Alemania/epidemiología , Humanos , Incidencia , Masculino , Persona de Mediana Edad , Salud Pública , Factores de Riesgo , Encuestas y Cuestionarios , Adulto Joven
7.
Gesundheitswesen ; 83(2): 114-121, 2021 Feb.
Artículo en Alemán | MEDLINE | ID: mdl-31746446

RESUMEN

AIM OF STUDY: This study aims to provide population-based reference values for heart rate-based indicators of cardiorespiratory fitness for adults with physical activity readiness aged 18 to 64 years living in Germany. METHODS: Based on data on 2,826 individuals who participated in a submaximal cycle ergometer exercise test as part of the German National Health Interview and Examination Survey for Adults (DEGS1) between 2008 and 2011, we calculated the following indicators: physical working capacity at 150 and 130 beats/min and at 75% of estimated maximum heart rate (PWC150, PWC130 and PWC75%) as well as heart rate-based estimated maximum oxygen uptake (VO2max). We used the LMS method by Cole & Green 1992 to calculate reference values. RESULTS: 25th, 50th and 75th percentiles of PWC150 were 1.5, 1.77 and 2.08 watts/kg among men and 1.18, 1.44 and 1.69 among women. 25th, 50th and 75th percentiles of PWC130 were 1.16, 1.41 and 1.68 watts/kg among men and 0.81, 1.05 and 1.29 among women. Age-dependent median PWC75% values among men and women were 1.87 - age in years× 0.01 and 1.31 - (age in years/100)2× 0.98, respectively, and VO2max among men is 41.7 - age× 0.15. CONCLUSIONS: The references values presented can be used for individual rating of cardiorespiratory fitness among adults living in Germany. Furthermore, they can serve as a basis for regular monitoring purposes.


Asunto(s)
Capacidad Cardiovascular , Adolescente , Adulto , Femenino , Alemania/epidemiología , Humanos , Lactante , Masculino , Persona de Mediana Edad , Oxígeno , Consumo de Oxígeno , Aptitud Física , Valores de Referencia , Adulto Joven
8.
Front Genet ; 11: 315, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-32373156

RESUMEN

Aging is the largest risk factor in many diseases and mortality alike. As the elderly population is expected to increase at an accelerating rate in the future, these phenomena will pose a growing socio-economic burden on societies. To successfully cope with this challenge, a deeper understanding of aging is crucial. In many aspects, the companion dog is an increasingly popular model organism to study aging, with the promise of producing results that are more applicable to humans than the findings that come from the studies of classical model organisms. In this preliminary study we used the whole-genome sequence of two extremely old dogs - age: 22 and 27 years (or 90-135% more, than the average lifespan of dogs) - in order to make the first steps to understand the genetic background of extreme longevity in dogs. We identified more than ∼80 1000 novel SNPs in the two dogs (7500 of which overlapped between them) when compared to three publicly available canine SNP databases, which included SNP information from850 dogs. Most novel mutations (∼52000 SNPs) were identified at non-coding regions, while 4.6% of the remaining SNPs (n∼1600) were at exons, including 670 missense variants - 76 of which overlapped between the two animals - across 472 genes. Based on their gene ontologies, these genes were related - among others - to gene transcription/translation and its regulation, to immune response and the nervous system in general. We also detected 12 loss-of-function mutations, although their actual effect is unclear. Several genetic pathways were also identified, which pathways may be tempting candidates to be investigated in large sample sizes in order to confirm their relevance in extreme longevity in dogs (and possibly, in humans). We hypothesize a possible link between extreme longevity and the regulation of gene transcription/translation, which hypothesis should be further investigated in the future. This phenomenon could define an interesting direction for future research aiming to better understand longevity. The presented preliminary results highlight the utility of the companion dog in the study of the genetic background of longevity and aging.

9.
Artículo en Alemán | MEDLINE | ID: mdl-31529188

RESUMEN

Regular physical activity and good motor performance are the basis for healthy physical development in childhood and are considered a protective factor for various health risks. However, children and adolescents in Germany are not physically active enough because sedentary activities have increased. One consequence is the decline in motor capacity, the totality of structures and functions that are responsible for the performance of motor actions.In the second follow-up survey of the study on the health of children and adolescents in Germany (KiGGS Wave 2, 2014-2017), the motor performance (LF) of 4­ to 10-year-old children was examined with three motor tests: one-leg stand (EIN), stand and reach (RB), and jumping sideways (SHH). The purpose of this paper is to present the results of the tests and to compare them with data from the KiGGS baseline survey (2003-2006). It also analyzes how motor performance differs in terms of different characteristics such as sociodemographic factors, obesity, and physical activity.Compared to the KiGGS baseline survey, the 4­ to 10-year-olds' motor performance in KiGGS Wave 2 has slightly improved in EIN, but RB and SHH are stagnating at low level. The test results indicate that middle and high social status, club sport activity, and "no overweight" are associated with above-average motor performance.Health policy, sports organizations, schools, and kindergartens should work together more closely so that all children have the same chance of good motor performance.


Asunto(s)
Ejercicio Físico , Deportes , Adolescente , Niño , Preescolar , Estudios Transversales , Alemania , Encuestas Epidemiológicas , Humanos , Actividad Motora
12.
Artículo en Alemán | MEDLINE | ID: mdl-30215104

RESUMEN

BACKGROUND: Despite decreasing smoking prevalence, tobacco use remains a key public health problem in Germany. For planning, managing, and evaluating tobacco control measures, regular data collection on smoking behavior in the population is essential. The aim of this article is to present trends in adult tobacco use since the early 1990s based on data from the health monitoring of the Robert Koch-Institute (RKI). METHODS: Analyses are based on data from 106,158 individuals aged 18 to 79 years, who participated in seven RKI health surveys from 1991-2015. Trends in tobacco consumption were analyzed using different indicators of smoking behavior, stratified by age, cohort, and gender. RESULTS: An overall falling smoking prevalence can be attributed primarily to a significant decline in the younger age groups since the early 2000s. Trend analysis by cohort reveals a declining prevalence for almost all cohorts over time from 1991-2015. Historically there has been is a sharp increase in the prevalence of women who have ever smoked between the 1930-1934 and 1950-1959 cohorts. The proportion of men who have ever smoked slightly decreased between the 1930-1934 and 1980-1984 cohorts. DISCUSSION: The shown overall decline happened concurrently with various tobacco prevention measures implemented during this period in Germany. If present trends related to continuous high smoking rates are sustained, it can be assumed that the tobacco consumption of the population will remain the source of adverse health outcomes. Accordingly, tobacco prevention measures and the promotion of smoking cessation in all age groups should be a public health priority.


Asunto(s)
Cese del Hábito de Fumar , Fumar , Adolescente , Adulto , Anciano , Femenino , Alemania/epidemiología , Encuestas Epidemiológicas , Humanos , Masculino , Persona de Mediana Edad , Prevalencia , Fumar/epidemiología , Uso de Tabaco , Adulto Joven
13.
J Cell Biol ; 217(10): 3398-3415, 2018 10 01.
Artículo en Inglés | MEDLINE | ID: mdl-30037925

RESUMEN

Spp1 is the H3K4me3 reader subunit of the Set1 complex (COMPASS/Set1C) that contributes to the mechanism by which meiotic DNA break sites are mechanistically selected. We previously proposed a model in which Spp1 interacts with H3K4me3 and the chromosome axis protein Mer2 that leads to DSB formation. Here we show that spatial interactions of Spp1 and Mer2 occur independently of Set1C. Spp1 exhibits dynamic chromatin binding features during meiosis, with many de novo appearing and disappearing binding sites. Spp1 chromatin binding dynamics depends on its PHD finger and Mer2-interacting domain and on modifiable histone residues (H3R2/K4). Remarkably, association of Spp1 with Mer2 axial sites reduces the effective turnover rate and diffusion coefficient of Spp1 upon chromatin binding, compared with other Set1C subunits. Our results indicate that "chromosomal turnover rate" is a major molecular determinant of Spp1 function in the framework of meiotic chromatin structure that prepares recombination initiation sites for break formation.


Asunto(s)
Cromosomas Fúngicos/metabolismo , Roturas del ADN , ADN de Hongos/metabolismo , Proteínas de Unión al ADN/metabolismo , Recombinación Homóloga/fisiología , Meiosis/fisiología , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/metabolismo , Cromatina/genética , Cromatina/metabolismo , Cromosomas Fúngicos/genética , ADN de Hongos/genética , Proteínas de Unión al ADN/genética , N-Metiltransferasa de Histona-Lisina/genética , N-Metiltransferasa de Histona-Lisina/metabolismo , Histonas/genética , Histonas/metabolismo , Dominios Proteicos , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genética
14.
Annu Rev Phys Chem ; 69: 327-352, 2018 04 20.
Artículo en Inglés | MEDLINE | ID: mdl-29677467

RESUMEN

Femtosecond two-dimensional (2D) Fourier transform spectroscopy generates and probes several types of coherence that characterize the couplings between vibrational and electronic motions. These couplings have been studied in molecules with Jahn-Teller conical intersections, pseudo-Jahn-Teller funnels, dimers, molecular aggregates, photosynthetic light harvesting complexes, and photosynthetic reaction centers. All have closely related Hamiltonians and at least two types of vibrations, including one that is decoupled from the electronic dynamics and one that is nonadiabatically coupled. Polarized pulse sequences can often be used to distinguish these types of vibrations. Electronic coherences are rapidly obscured by inhomogeneous dephasing. The longest-lived coherences in these systems arise from delocalized vibrations on the ground electronic state that are enhanced by a nonadiabatic Raman excitation process. These characterize the initial excited-state dynamics. 2D oscillation maps are beginning to isolate the medium lifetime vibronic coherences that report on subsequent stages of the excited-state dynamics.

15.
J Chem Phys ; 148(8): 084308, 2018 Feb 28.
Artículo en Inglés | MEDLINE | ID: mdl-29495789

RESUMEN

Vibrational-electronic resonance in photosynthetic pigment-protein complexes invalidates Förster's adiabatic framework for interpreting spectra and energy transfer, thus complicating determination of how the surrounding protein affects pigment properties. This paper considers the combined effects of vibrational-electronic resonance and inhomogeneous variations in the electronic excitation energies of pigments at different sites on absorption, emission, circular dichroism, and hole-burning spectra for a non-degenerate homodimer. The non-degenerate homodimer has identical pigments in different sites that generate differences in electronic energies, with parameters loosely based on bacteriochlorophyll a pigments in the Fenna-Matthews-Olson antenna protein. To explain the intensity borrowing, the excited state vibrational-electronic eigenvectors are discussed in terms of the vibrational basis localized on the individual pigments, as well as the correlated/anti-correlated vibrational basis delocalized over both pigments. Compared to those in the isolated pigment, vibrational satellites for the correlated vibration have the same frequency and precisely a factor of 2 intensity reduction through vibrational delocalization in both absorption and emission. Vibrational satellites for anti-correlated vibrations have their relaxed emission intensity reduced by over a factor 2 through vibrational and excitonic delocalization. In absorption, anti-correlated vibrational satellites borrow excitonic intensity but can be broadened away by the combination of vibronic resonance and site inhomogeneity; in parallel, their vibronically resonant excitonic partners are also broadened away. These considerations are consistent with photosynthetic antenna hole-burning spectra, where sharp vibrational and excitonic satellites are absent. Vibrational-excitonic resonance barely alters the inhomogeneously broadened linear absorption, emission, and circular dichroism spectra from those for a purely electronic excitonic coupling model. Energy transfer can leave excess energy behind as vibration on the electronic ground state of the donor, allowing vibrational relaxation on the donor's ground electronic state to make energy transfer permanent by removing excess energy from the excited electronic state of the dimer.


Asunto(s)
Electrones , Dimerización , Transferencia de Energía , Teoría Cuántica , Análisis Espectral , Vibración
18.
Mol Cell Endocrinol ; 471: 63-74, 2018 08 15.
Artículo en Inglés | MEDLINE | ID: mdl-28774779

RESUMEN

Macrophages are able to differentiate into classically polarized (M1) or alternatively polarized (M2) states upon encountering pro-inflammatory cytokines such as interferon (IFN) γ or anti-inflammatory cytokines such as interleukin (IL) -4/IL-13, respectively. Moreover, macrophages are known to regulate lipid metabolism via multiple members of the nuclear hormone receptor family, including the retinoid X receptors (RXR). It has been also documented that cytokines are able to modulate macrophage responses to lipid signals but the nature of these interactions and the underlying mechanisms of these processes especially at the level of the chromatinized genome are not well understood. Previous work from our laboratory suggested that STAT6 is a facilitator of nuclear receptor mediated transcriptional activity acting at the genome level. This prompted us to investigate genome-wide DNA binding events and the development of cistromes in human CD14+ monocyte-derived macrophages upon exposure to IL-4. We determined the impact of IL-4 on the PU.1, RXR and STAT6 cistromes within the active enhancer regions marked by H3K27-acetylation using chromatin immunoprecipitation followed by deep sequencing and integrated bioinformatics analyses. We found that about 2/3rd of the IL-4 induced STAT6 peaks co-localized with RXR peaks. These STAT6/RXR co-peaks differed at least in part from the non-overlapping RXR peaks regarding the most enriched de novo transcription factor binding motifs. Interestingly, RXR-binding was not regulated at the STAT6/RXR co-bound enhancers following IL-4 stimulation, but differential enhancer interactions were observed between the IL-4/STAT6 and RXR signaling pathways acting in a gene selective manner. Our results suggest that there is a novel, so far uncharacterized cistromic crosstalk between RXR and STAT6 that is likely to contribute to the formation of the active enhancer repertoire, transcriptome and differential signal-specific gene regulation of polarized macrophages.


Asunto(s)
Diferenciación Celular , Elementos de Facilitación Genéticos/genética , Receptores de Lipopolisacáridos/metabolismo , Macrófagos/citología , Monocitos/metabolismo , Receptores X Retinoide/metabolismo , Factor de Transcripción STAT6/metabolismo , Células Cultivadas , Perfilación de la Expresión Génica , Genoma Humano , Humanos , Interleucina-4/metabolismo , Macrófagos/metabolismo , Unión Proteica , Proteínas Proto-Oncogénicas/metabolismo , Transducción de Señal , Transactivadores/metabolismo
19.
J Chem Phys ; 147(19): 194306, 2017 Nov 21.
Artículo en Inglés | MEDLINE | ID: mdl-29166106

RESUMEN

The nonadiabatic states and dynamics are investigated for a linear vibronic coupling Hamiltonian with a static electronic splitting and weak off-diagonal Jahn-Teller coupling through a single vibration with a vibrational-electronic resonance. With a transformation of the electronic basis, this Hamiltonian is also applicable to the anti-correlated vibration in a symmetric homodimer with marginally strong constant off-diagonal coupling, where the non-adiabatic states and dynamics model electronic excitation energy transfer or self-exchange electron transfer. For parameters modeling a free-base naphthalocyanine, the nonadiabatic couplings are deeply quantum mechanical and depend on wavepacket width; scalar couplings are as important as the derivative couplings that are usually interpreted to depend on vibrational velocity in semiclassical curve crossing or surface hopping theories. A colored visualization scheme that fully characterizes the non-adiabatic states using the exact factorization is developed. The nonadiabatic states in this nested funnel have nodeless vibrational factors with strongly avoided zeroes in their vibrational probability densities. Vibronic dynamics are visualized through the vibrational coordinate dependent density of the time-dependent dipole moment in free induction decay. Vibrational motion is amplified by the nonadiabatic couplings, with asymmetric and anisotropic motions that depend upon the excitation polarization in the molecular frame and can be reversed by a change in polarization. This generates a vibrational quantum beat anisotropy in excess of 2/5. The amplitude of vibrational motion can be larger than that on the uncoupled potentials, and the electronic population transfer is maximized within one vibrational period. Most of these dynamics are missed by the adiabatic approximation, and some electronic and vibrational motions are completely suppressed by the Condon approximation of a coordinate-independent transition dipole between adiabatic states. For all initial conditions investigated, the initial nonadiabatic electronic motion is driven towards the lower adiabatic state, and criteria for this directed motion are discussed.

20.
J Chem Phys ; 147(15): 154308, 2017 Oct 21.
Artículo en Inglés | MEDLINE | ID: mdl-29055315

RESUMEN

Non-adiabatic vibrational-electronic resonance in the excited electronic states of natural photosynthetic antennas drastically alters the adiabatic framework, in which electronic energy transfer has been conventionally studied, and suggests the possibility of exploiting non-adiabatic dynamics for directed energy transfer. Here, a generalized dimer model incorporates asymmetries between pigments, coupling to the environment, and the doubly excited state relevant for nonlinear spectroscopy. For this generalized dimer model, the vibrational tuning vector that drives energy transfer is derived and connected to decoherence between singly excited states. A correlation vector is connected to decoherence between the ground state and the doubly excited state. Optical decoherence between the ground and singly excited states involves linear combinations of the correlation and tuning vectors. Excitonic coupling modifies the tuning vector. The correlation and tuning vectors are not always orthogonal, and both can be asymmetric under pigment exchange, which affects energy transfer. For equal pigment vibrational frequencies, the nonadiabatic tuning vector becomes an anti-correlated delocalized linear combination of intramolecular vibrations of the two pigments, and the nonadiabatic energy transfer dynamics become separable. With exchange symmetry, the correlation and tuning vectors become delocalized intramolecular vibrations that are symmetric and antisymmetric under pigment exchange. Diabatic criteria for vibrational-excitonic resonance demonstrate that anti-correlated vibrations increase the range and speed of vibronically resonant energy transfer (the Golden Rule rate is a factor of 2 faster). A partial trace analysis shows that vibronic decoherence for a vibrational-excitonic resonance between two excitons is slower than their purely excitonic decoherence.

SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA