The Observed and Calculated Vibrational Spectra of DL‐methionine in the Study of the Solid State Phase Transition

Abstract

The ir and Raman spectra of α and β‐DL‐methionine and three isotopomers have been recorded and assigned with the help of normal coordinate analyses. The vibrational intensities of three conformers (χ1 = gauche II; χ2 = trans; χ3 = gauche I, trans, and gauche II) have been calculated for the free molecule with a MNDO program including a finite field perturbation. Except for the vibrations including the S atom, the CO−2 and NH+3 group the calculations agree with experimental data and confirm the change of χ3 from trans to gauche I at the 326 K transition. The lattice vibrations confirm the conservation of the overall structure of the double layers through the transition.

Solid−Solid Phase Transitions in dl-Norvaline Studied by Differential Scanning Calorimetry and Raman Spectroscopy

“…The first ratio is assumed to be sensitive to lateral chain−chain interactions and the second ratio is sensitive to intermolecular interactions, but also it should reflect the mobility of the methyl terminal group of hydrocarbon chains. Thus, the lower the intensity ratio is, the higher the conformational order of the alkyl chain and the lower mobility of the methyl end group is obtained. ,, Figure represents the changes in Raman peak height intensity ratios in relation to temperature of dl -norvaline. It is shown clearly that there are two temperature regions at about −120 and −76 °C, in which an increase of the intensity ratios is observed that almost corresponds to the phase transitions observed by DSC.…”

“…This table summarizes conformationally sensitive bands which are showed differences during phase transition and will be discussed in the text. Bands were assigned by comparison with similar compounds. ,,,,,,− ,, …”

“…The structural variations in the solid state constitute a simple model for conformational dependence in biochemical processes. In particular, the thermal analysis on solid−solid phase transitions between crystalline amino acids brings suggestive information on transition phenomena of biological systems, especially of biomembranes. − …”

Study of spontaneous cleavage and change in surface structure of dl-methionine crystals

“…Figs. 3(a) and (b) show CH 3 -S stretching region and -COO-vibration region, respectively [2]. The spectra observed at 333 K are different from others, indicating that the structural change of the crystal occurred between 323 and 333 K.…”

Methionine Changes in Bacteriorhodopsin Detected by FTIR and Cell-Free Selenomethionine Substitution

“…Earlier infrared studies of methionine and selenomethionine, which utilized solid-state amino acids (Shepherd and Huber, 1969;Tamba et al, 1973), revealed that the S!Se substitution had a small effect on the 1800-1400 cm ÿ1 region but altered many peaks below 1400 cm ÿ1 . The latter bands represent various vibrational modes of the methionine side chain and typically have medium intensity (Grunenberg and Bougeard, 1986). Because our difference spectra exhibited only two bands at 1284 and 903/899 cm ÿ1 , which are sensitive to the S!Se replacement, it appears that only minor alterations of the chemical bonds involving sulfur occur during the BR!M transition.…”