Aiming at absolute force calibration of optical tweezers, following a critical review proposed theoretical models, we present and test the results Mie-Debye-spherical aberration (MDSA) theory, an extension previous (MD) model, taking account spherical glass-water interface. This first-principles theory is formulated entirely in terms experimentally accessible parameters (none adjustable). Careful experimental tests MDSA undertaken two laboratories, with very different setups, are described....

We have investigated the interaction of DNA molecule with anticancer drug doxorubicin (doxo) by using three different experimental techniques: single stretching, imaging, and dynamic light scattering. Such techniques allowed us to get new insights on mechanical behavior DNA-doxo complexes as well physical chemistry interaction. First, contour length data obtained from stretching were used extract physicochemical parameters under buffer conditions. This analysis has proven that such can be...

We use optical tweezers and atomic force microscopy to investigate the potential of rare earth elements be used as anticancer agents in development new chemotherapeutic drugs by characterizing binding three earths (ytterbium, neodymium, erbium) double-stranded DNA, which is one main targets for these inside cells. The presented a significant interaction with biopolymer buffers physiological relevance, typically very high equilibrium association constants (10 6 10 7 M −1 ) at DNA grooves....

Binding of ligands to DNA can be studied by measuring the change persistence length complex formed, in single-molecule assays. We propose a methodology for data analysis based on quenched disorder statistical model and describing binding isotherm Hill-type equation. obtain an expression effective as function total ligand concentration, which we apply our DNA-cationic $\ensuremath{\beta}$-cyclodextrin DNA-HU protein available literature, determining values local lengths, dissociation...

Chloroquine has been used as a potent antimalarial, anticancer drug, and prophylactic. While chloroquine is known to interact with DNA, the details of DNA–ligand interactions have remained unclear. Here we characterize chloroquine–double-stranded DNA binding four complementary approaches, including optical tweezers, atomic force microscopy, duplex melting measurements, isothermal titration calorimetry. We show that intercalates into double stranded (dsDNA) KD ~ 200 µM, this entropically...

We use optical tweezers to perform stretching experiments on DNA molecules when interacting with the drugs daunomycin and ethidium bromide, which intercalate molecule. Our results show that persistence length of DNA-drug complexes increases strongly as drug concentration up some critical value. Above this value, decreases abruptly remains approximately constant for larger concentrations, at least in range used our experiments. Measured intercalators concentrations transition coincide...

A theoretical treatment of optical tweezers is presented at a level suitable for undergraduates. We explore the Rayleigh and geometrical optics regimes with an emphasis on latter. discuss model regime, including spherical aberration effects, show that can easily be implemented numerically. comparison experimental data yields excellent agreement between theory experiment. also briefly valid microspheres any size.

We have studied the interaction between anticancer drug Actinomycin D (ActD) and DNA molecule by performing single stretching experiments atomic force microscopy (AFM) imaging. From experiments, we determine how mechanical properties of DNA–ActD complexes vary as a function concentration, for fixed concentration. found that persistence lengths formed behave non-monotonically: at low concentrations ActD they are more flexible than bare become stiffer higher concentrations. On other hand,...

By performing single molecule stretching experiments with optical tweezers, we have studied the changes in mechanical properties of DNA-cisplatin complexes as a function some variables interest such drug diffusion time and concentration sample. We propose model to explain behavior persistence length concentration, extracting binding data from pure measurements. Such analysis has allowed us show that cisplatin binds cooperatively DNA molecule. In addition, compaction by action was also...

By performing single molecule stretching experiments with optical tweezers, we have studied the DNA interaction ligand Hoechst 33258. The mechanical properties of complexes formed as a function concentration were directly determined from these measurements by fitting force × extension curve to WormLike Chain model semiflexible polymers. In addition, physicochemical parameters extracted persistence length data using previously developed two-sites quenched disorder statistical model, allowing...

We propose a Bessel beam optical tweezers setup that can stably trap superparamagnetic beads. The stiffness measured is practically independent of the radius and bead height (distance from coverlip sample chamber), indicating beads be trapped with high accuracy within wide range such parameters. On other hand, exhibits expected linear increase laser power, despite non-negligible absorption coefficient A geometrical optics model considers spherical aberration light by was used to predict...

In the present work we have gone a step forward in understanding of DNA-cisplatin interaction, investigating role ionic strength on complexes formation. To achieve this task, use optical tweezers to perform force spectroscopy complexes, determining their mechanical parameters as function drug concentration sample for three different buffers. From such measurements, determine binding and study behavior strength. The equilibrium constant decreases with counterion ([Na]) can be used estimate...

In this work, we use force spectroscopy to investigate the interaction between DAPI fluorescent dye and λ-DNA molecule under high (174 mM) low (34 ionic strengths. Firstly, have measured changes on mechanical properties (persistence contour lengths) of DNA-DAPI complexes as a function concentration in sample. Then, recently developed models order connect behavior both physical chemistry interaction. Such analysis has allowed us identify decouple two main binding modes, determining relevant...

By using optical tweezers with an adjustable trap stiffness, we have performed systematic single molecule stretching experiments two types of DNA–intercalator complexes, in order to investigate the effects maximum applied forces on mechanical response such complexes.

We have investigated the interaction between native neutral β-cyclodextrin (CD) and DNA molecule by performing single-molecule stretching experiments with optical tweezers. In particular, we monitored changes of mechanical properties CD–DNA complexes as a function CD concentration in sample. By using quenched disorder statistical model, were also capable to extract important physicochemical information (equilibrium binding constants, cooperativity degree) such from data. addition, found that...

We report the first experimental study upon optical trapping and manipulation of topological insulator (TI) particles. By virtue unique TI properties, which have a conducting surface an insulating bulk, particles present peculiar behavior in presence single laser beam tweezers: they oscillate plane perpendicular to direction propagation. In other words, behave as optically induced oscillators, allowing dynamical measurements with unprecedented simplicity purely control. Actually, rheology...

Reflection and refraction of light can be used to trap small dielectric particles in the geometrical optics regime. Absorption is usually neglected theoretical calculations, but it known that occurs optical trapping semi-transparent particles. Here, we propose a generalization Ashkin's model for radiative force exerted on spherical bead, including contribution due attenuation/absorption bulk particle. We discuss detail balance between refraction, reflection, absorption different parameters...

Here we propose the use of organic semiconductor polyaniline (PANI) for preparation spherical-shaped microparticles to serve as handles in optical tweezers (OT) experiments. The stable trapping and manipulation PANI beads was demonstrated first time, using a Gaussian (TEM00) beam tweezers. trap stiffness characterized various different parameters such bead radius, laser power, distance between coverslip sample chamber, attesting viability material manipulation. Since effective properties can...

We have measured the overall transmittance of a laser beam through an oil immersion objective as function transverse size beam, using dual-objective method. Our results show that is not uniform and its dependence on radial beam's position can be modeled by Gaussian function. This property affects intensity distribution pattern in sample region should taken into account theoretical descriptions optical tweezers. Moreover, one must consider this to determine local power delivered at method,...