Combining X-Rays and Neutrons to Shed Light in the Conformational Changes in Aminoacids
Journal Title: Biomedical Journal of Scientific & Technical Research (BJSTR) - Year 2018, Vol 8, Issue 3
Abstract
Amino acids are small organic molecules having both amino and carboxylic acid groups bound to the a-carbon, with a general formula NH2- CH(R)-COOH. Their side chains, R, can vary - saml our bulky, hidrophobic our hydrophilic, polar, charged or neutral. If the a-carbon is bound to four different chemical groups, the amino acid is chiral and two isomers exist labeled with L our D. Furthermore, the parameters characterizing the motions of amino acids in crystal can be comparable with those describing this dynamics in biopolymers. Therefore, possessing information on the strusture and dynamics of single amino acids is important in biochemistry, biophysics, medicine and pharmacy. The structure and dynamics of crystalline amino acids can be followed in a wide temperature and pressure range by diffraction and various spectroscopic techniques and the results can be interpreted, giving the characteristic times of selected motions and the values of related energy barriers.L-methionine (Figure 1) is an essential amino acid important in the methylation process playing a key role in the immune system affected by HIV [1] and other diseases (like Alzheimer and Parkinson [2]) . However very few studies crystalline L- methionine have been reported in the literature [3] thus very little is known about its physical properties. The aim of this study is to investigate the stucture-property relations in L- methionine as a function temperature, because of according to recent experiments, including Raman spectroscopy, thermal analysis, neutron diffraction and inelastic neutron scattering, changes in the conformational states of L-methionine induce a variety of structural arrangements between 220 and 340 K. Here we present the first results from X-ray Synchrotron(LNLS-XPD) and neutron diffraction (IPEN) which combined to the previous results confirm that subtle structural changes in L- Methionine lead to a rich phase diagram in this important amino acid.The L-methionine powder samples measured, using neutron and X-ray diffraction, were acquire from Sigma-Aldrich and no further treatment (like purification) were performed. Neutron Powder Diffractometer (NPD) Aurora-IPEN: The neutron powder diffractometer used in the study is Aurora, a high-resolution powder diffractometer, placed on the research reactor IEA-R1, located at the Instituto de Pesquisas Energéticas e Nucleares (IPEN-CNEN, Sao Paulo) [4]. Aurora diffractometer set up is designed with a position sensitive detector (PSD) and a silicon double-focusing single crystal monochromator. In order to perform the measurement in the L-methionine powder samples, an adjusted value for the wavelength of 1.399 Á was used, improving the resolution in the q-range measured. The experiment was performed at room temperature, and a vanadium container was used to hold the sample.
Authors and Affiliations
Margareth KKD Franco, Fabiano Yokaichiya
Keywords
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- EP ID EP591030
- DOI 10.26717/BJSTR.2018.08.001643
- Views 157
- Downloads 0
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