Molecular dynamics (MD) simulations have been carried out to understand the binding mechanism of various chiral single-walled carbon nanotubes (SWCNTs) and single-stranded DNA (ssDNA) of four different nucleobase sequences (i.e., ssdA(14), ssdT(14), ssdG(14), and ssdC(14), where, A, T, G, and C are adenine, thymine, guanine, and cytosine, respectively) in aqueous media at room temperature (300 K) and atmospheric pressure (1 atm). The simulations studies reveal that ssDNA undergoes rapid structural changes and wrap around the SWCNTs via π-stacking interactions between SWCNT's wall and the nucleobases of ssDNA. Our computations demonstrate that the length of the ssDNA plays an important role during the wrapping process. Moreover, it suggests that the length of the sequence should be proportional to the diameter of the SWCNT, in order to overcome the intralocked π-stacking interactions between the nucleobases of ssDNA sequence. Also, in our classical MD simulation, we do not observe the correlation between the diameter of SWCNTs and the sequences of ssDNA, which indicates the importance of electronic factors of these systems. In order to understand the electronic contributions of these systems, the quantum calculations have been performed at Hartree-Fock level for the 17 ns MD simulated structures. The quantum chemical calculations provide evidence that the highly stable ssDNA@SWCNT hybrid possesses a larger HOMO-LUMO gap.
Three fundamental challenges for the development of technologically relevant sodium-ion batteries (SIB) and sodium-ion capacitors (SIC) are the lower cell voltage, decreased ionic-diffusivity and larger volume of sodium-ions relative to their lithium-ion analogues.
Density functional theory at the B3LYP/6-31G* level with counterpoise correction has been employed to study six sets of nitrogenous bases for the capacity of each to form H-bonded dimers restricted to a chosen pairing configuration. These results are augmented by MP2/6-311++G(d,p) single point calculations on the B3LYP/6-31G* optimized geometries. Each set has two bases, including substituted azoles, imidazoles, pyrimidines, and fused ring systems. This study aims to determine the suitability of each set to furnish H-bonded base pairs which may serve as repeat units for self-associative H-bonded macromolecular duplexes with the capacity to store and replicate information at the molecular level. Out of the various possibilities tested here, a set of two substituted pyrimidines best satisfies the prescribed criteria and may be put forward as a good candidate to yield isomorphic repeat units for designing such synthetic information-bearing macromolecular duplexes. The optimized configurations of these chosen base pairs as calculated at the B3LYP/6-31G* level compare well with those calculated at the B3LYP/6-31++G(d,p) and MP2/6-31G(d,p) levels, and indicate that isomorphism of the two base pairs is independent of method used. Assuming a one-to-one correspondence for encoding information in the macromolecule, such a set of two bases can allow the macromolecule to encode up to 8 types of encrypted species.
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