Conformational and mechanical changes of DNA upon transcription factor binding detected by a QCM and transmission line model.

A novel quartz crystal microbalance (QCM) analytical method is developed based on the transmission line model (TLM) algorithm to analyze the binding of transcription factors (TFs) to immobilized DNA oligoduplexes. The method is used to characterize the mechanical properties of biological films through the estimation of the film dynamic shear moduli, G and G, and the film thickness. Using the Saccharomyces cerevisiae transcription factor Haa1 (Haa1DBD) as a biological model two sensors were prepared by immobilizing DNA oligoduplexes, one containing the Haa1 recognition element (HRE(wt)) and another with a random sequence (HRE(neg)) used as a negative control. The immobilization of DNA oligoduplexes was followed in real time and we show that DNA strands initially adsorb with low or non-tilting, laying flat close to the surface, which then lift-off the surface leading to final film tilting angles of 62.9° and 46.7° for HRE(wt) and HRE(neg), respectively. Furthermore we show that the binding of Haa1DBD to HRE(wt) leads to a more ordered and compact film, and forces a 31.7° bending of the immobilized HRE(wt) oligoduplex. This work demonstrates the suitability of the QCM to monitor the specific binding of TFs to immobilized DNA sequences and provides an analytical methodology to study protein-DNA biophysics and kinetics.

Comparação dos níveis de ansiedade e depressão entre idosos ativos e sedentários / Comparison of levels of anxiety and depression among active and sedentary elderly

CONTEXTO: A ansiedade e a depressão constituem um problema de saúde pública nos idosos. Atualmente, tem-se demonstrado uma associação positiva entre a prática de atividade física e a boa saúde mental.OBJETIVO: Comparar a relação entre os níveis de ansiedade e depressão entre idosos ativos e sedentários.MÉTODOS: A amostra foi constituída por 72 idosos, divididos num grupo de 38 idosos sedentários (GS) e outro grupo (GA) de 34 fisicamente ativos. Estes responderam a um questionário com características sociodemográficas e a Escala de Ansiedade e Depressão para Hospital Geral.RESULTADOS: As variáveis que influenciaram a presença de ansiedade ou depressão foram o nível de atividade física (p < 0,001) e de escolaridade (p < 0,01). O GS apresentou 38 vezes mais de probabilidade de vir a desenvolver sintomas de ansiedade e depressão e os indivíduos sem habilitações apresentam 11 vezes mais de probabilidade de vir a desenvolver esses sintomas. No GS, 35 (92,1%) idosos apresentaram níveis de ansiedade ou depressão e 3 (7,9%) não apresentaram. No GA apenas 8 (23,5%) apresentaram níveis de ansiedade ou depressão e 26 (76,5%) não revelaram esses sintomas (p < 0,05).CONCLUSÃO: A prática da atividade física pode representar um fator importante para reduzir os níveis de ansiedade e depressão em idosos.

BACKGROUND: The anxiety and depression are a public health problem in the elderly. Currently some studies have been shown a positive association between physical activity and good mental health.OBJECTIVE: To compare the possible relationship between levels of anxiety and depression among active and sedentary elderly.METHODS: The sample comprised a total of 72 patients divided into one group of 38 elderly subjects (GS) and another group of 34 physically assets (GA). These answered a questionnaire with socio-demographic characteristics and the Hospital Anxiety and Depression Scale.RESULTS: The variables that influenced the presence of anxiety and depression were the level of physical activity (p < 0,001) and the level of instruction (p < 0,01). The GS showed 38 more probability to develop symptoms of anxiety and depression and subjects without qualifications had 11 more probability to develop these symptoms. For the GS 35 (92,1%) patients had levels of anxiety or depression and 3 (7,9%) did not. In GA, the presence of anxiety or depression were observed only in 8 (23,5%) and the remaining 26 (76,5%) revalidates not any kind of these symptoms (p < 0,05).DISCUSSION: Practicing physical activity may represent a very important factor to reduce levels of anxiety and depression in elderly.

Acoustic detection of cell adhesion on a quartz crystal microbalance.

An acoustic quartz crystal microbalance (QCM) was used to signal and follow the cell­adhesion process of epithelial cells [human embryonic kidney(HEK) 293T and cervical cancer (HeLa) and fibroblasts [African Green Monkey kidney cells (COS-7)] onto gold surfaces. Cells were applied on the sensor and grown under serum-free and serum-supplemented culture media. The sensor resonance frequency (Δf) and motional resistance (ΔR) variations were measured during cell growth to monitor cell adhesion processes. Fingerprints of the adhesion processes, generated using the QCM signal, were found to be specific for each cell type while enabling the identification of the phases of the adhesion process. Under serum-free conditions, the deposition of HEK 293T and HeLa cells was characterized by a decrease of Δf with constant ΔR, whereas for COS­7 cells, this initial deposition was signaled by variations of ΔR at constant Δf. Toward the end of the adhesion process, fingerprints were characterized by a continuous increase of ΔR consistent with the increase in viscoelasticity. The morphology of adherent cells was visualized by fluorescent microscopy, enabling the association of the cell morphology with QCM signals.

Acoustic wave biosensors: physical models and biological applications of quartz crystal microbalance.

Piezoelectric sensors are acoustic sensors that enable the selective and label-free detection of biological events in real time. These sensors generate acoustic waves and utilize measurements of the variation of the wave propagation properties as a signal for probing events at the sensor surface. Quartz crystal microbalance (QCM) devices, the most widespread acoustic resonators, allow the study of viscoelastic properties of matter, the adsorption of molecules, or the motility of living cells. In a tutorial-like approach, this review addresses the physical principles associated with the QCM, as well as the origin and effects of major interfering phenomena. Special attention is paid to the possibilities offered by QCM that go beyond microweighing, and important recent examples are presented.