Centro de Ciências Exatas e Tecnológicas
URI permanente desta comunidadehttps://locus.ufv.br/handle/123456789/9791
Navegar
2 resultados
Resultados da Pesquisa
Item Videomicroscopy calibration of optical tweezers by position autocorrelation function analysis(Applied Physics B, 2012-03-21) Alves, P. S.; Rocha, M. S.We present a simple method to calibrate optical tweezers by using only videomicroscopy to measure the position autocorrelation function of the trapped bead in the potential well of the tweezers. To accomplish this task, we use a high-speed camera with ∼500 fps (frames per second), which provides a precise measurement of the relaxation time of the bead Brownian fluctuations. We also study the variation of the trap stiffness as a function of some parameters of interest such as the laser power and the distance from the bead center to the microscope coverslip, showing that the presented method returns precise results.Item Controlling cooperativity in β-cyclodextrin–DNA binding reactions(The Journal of Physical Chemistry Letters, 2015-08-26) Rocha, M. S.; Alves, P. S.; Mesquita, O. N.We have investigated the interaction between the native neutral β- cyclodextrin (CD) and the DNA molecule by performing single-molecule stretching experiments with optical tweezers. In particular, we have monitored the changes of the mechanical properties of the CD−DNA complexes as a function of the CD concentration in the sample. By using a quenched disorder statistical model, we were also capable to extract important physicochemical information (equilibrium binding constants, cooperativity degree) of such interaction from the mechanical data. In addition, we have found that the interaction occurs by two different mechanisms, first with the formation of relatively large CD clusters along the double helix, which thereafter can locally denature the DNA molecule by forming hydrogen bonds with the base pairs that eventually flip out. A prediction of our quenched disorder model was that cooperativity could be controlled by adjusting the surface charge of β-CD molecules. This prediction is confirmed in the present work.