Proton Affinities of Some Amino Acid Side Chains in a Restricted Environment

Abstract

We investigate the dependence of proton affinity values of the side chains of amino acids such as Asp, Glu, His, Ser, and Thr on confinement in a single-walled carbon nanotube. The proton affinity values, estimated using the density functional theories (PW91/dnp and BLYP/dnp), are found to be highly sensitive toward confinement. We find that for both Asp and Glu, the proton affinity, while suspended inside the carbon nanotube, becomes much less in comparison to their respective gas phase values. In the case of His, Ser, and Thr side chains, on the other hand, the proton affinity inside the carbon nanotube becomes negative. Hydrogen bonding with neighboring polar groups is found to result in a marked increase in proton affinity inside the tube in all of the cases reported in this article. The increase is most remarkable in the case of His, Ser, and Thr side chains where the presence of polar neighboring groups within a hydrogen-bonding distance is found to augment the proton affinity value by more than 100 kcal mol(-1).

Structure and dynamics of water inside endohedrally functionalized carbon nanotubes

“…As discussed earlier, 30 initial structures of single-walled carbon nanotubes with or without endohedral functionalization were obtained in the gas phase using the utilities of DMol3 34 and optimized using density functional theory methods. 35 In the first stage of our work, we have studied pristine (6,6) open-ended SWCNT of length 15.6 Å and diameter of 8.2 Å.…”

“…The field exerted by the analogues of polar amino acid sidechains inside the hydrophobic core of SWCNTs has already been shown have substantial effect on the reactivities, energetics, and free energies of simple reactions. 30,31 Therefore, it is not unreasonable to expect interesting variations in the behaviour of water with different functional groups attached to the core of FCNTs.…”

Structure and Electronic Properties of the Double‐Wall Nanotubes Constructed from SiO2 Nanotubes Encapsulatedinside Armchair Carbon Nanotubes

“…When materials are confined in the tube cavity, new form of structure and various novel properties different from those in gas will appear. For example, when acid chain is confined in the nanotube space, its proton affinity will change greatly . So we can increase the materials’ application range by changing their dimension.…”

“…For example, when acid chain is confined in the nanotube space, its proton affinity will change greatly. [8] So we can increase the materials' application range by changing their dimension.…”

“…[11] Then the SiO 2 nanotube with a tetragonal cross section investigated in these letter are successfully produced by Liu and coworkers in 2009. [12] In the single-walled carbon nanotubes (SWCNT), with the diameter of 1.2-1.4 nm, the precursors, H 8 Si 8 O 12 molecules, are transformed into tube-like structure, H 8 Si 4n O 8n-4 , which are confirmed by High Resolution Transmission Electron Microscopy (HRTEM), infrared(IR) and Raman spectroscopy. The new synthesized hybrid material is a novel composite double-walled nanotube constructed by the inner SiO 2 tube encapsulated in outer carbon tube.…”