Files and links (1)
Preprint (Author's original)arXiv.org - Non-exclusive license to distribute, Open
Preprint
Extended versus localized vibrations: the case of L-cysteine and L-cystine amino acids
28 Feb 2014
Abstract
A detailed quantitative analysis of the specific heat in the 1.8 – 300 K temperature range for L-cysteine and L-cystine amino acids was presented. We observed not extended but a sharp transition at ~76 K for L-cysteine. This transition was associated to the thiol group ordering and the order-disorder transition was adequately modeled by a 2D Ising model. The energy difference among two thiol configurations was found to be -J=ε_A-ε_B=-66.6 cal/mole. Besides, we conducted a study of phonon and rotor contributions to the specific heat and we proposed a generalization of Debye model. It was possible to evaluate the exponent of the g(ω), leading to the result that it corresponds to the Debye model for L-cysteine, which implies that the boson peak in this system is due to a maximum in the Ccoup(ω) and also that the plane wave of wave-vector( q ⃗ )is a good approximation to describe the phonons. On the other hand the origin of the boson peak for L-cystine correlates to a peak in g(ω) and phonons in L-cystine could be well represented by strongly attenuated plane waves or localized vibrations. Lastly, the analysis at very low temperature (T < 3 K) indicated that L-cysteine presented a nearly temperature independent behaviour which is opposite to which is widely observed in systems with glassy characteristics within the Two-Level System (TLS) framework.
Metrics
5 Record Views
Details
- Title
- Extended versus localized vibrations: the case of L-cysteine and L-cystine amino acids
- Creators
- M. S IshikawaT. A LimaF. F FerreiraH. S Martinho
- Resource Type
- Preprint
- Language
- English
- Academic Unit
- Chemical and Biological Engineering
- Other Identifier
- 991019299006204721