Optical methods, such as dynamic light scattering (DLS) and differential dynamic microscopy (DDM) are suitable experimental techniques for detecting submicron particles in different suspensions. In our case, these are aqueous suspensions of guanine-rich oligonucleotides that in the presence of a suitable concentration of cations, such as Na+ or K+, form longer structures called G-wires. The methods are based on light scattering and the calculation of the autocorrelation function of the perceived light intensity on a photomultiplier or a high-speed camera. Despite the fact, that the principle of measurement in the two mentioned methods is different, the results - based on a suitable mathematical model - complement each other and are comparable. With both methods, we determined the diffusion coefficients of the suspension, from which we deduced, which mutation of the initial oligonucleotide d(G2AG4AG2) form G-wires and what is the length of these wires. We detected G-wires of different sizes, whose effective lengths range from L min ⠼ 20 nm to L max ⠼ 140 nm.
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