Low-temperature infrared spectra and hydrogen bonding in polycrystalline dl-serine and deuterated derivatives

Abstract

The FT-IR spectra of polycrystalline DL-serine [a-amino-b-hydroxypropionic acid; HO-CH 2 -CH(NH 3 ) + -COO À ] and isotopically substituted [ND/OD Alcohol (<10% and >90% D); CD 2 (>98% D)] DL-serine were recorded in the range 4000-500 cm À1 in the temperature range 300-10 K, and fully assigned. The isotopic-doping/low-temperature methodology, which allows for decoupling of individual proton vibrational modes from the crystal bulk vibrations, was used to estimate the energies of the different H-bonds present in DL-serine crystal. To this end, the frequency shifts observed in both the NH/OH stretching and out-of-plane bending spectral regions (relatively to reference values for these vibrations in nonhydrogen-bonded DL-serine molecules) were used, together with previously developed empirical correlations. The results are compared with available structural data on this amino acid. #

Foldamers of β-peptides: conformational preference of peptides formed by rigid building blocks. The first MI-IR spectra of a triamide nanosystem

“…The first MI-IR spectroscopic investigations on amino acid residues were performed by Grenie et al (1970), who studied glycine (Gly) in an Ar matrix. Since then Gly (Grenie and Garrigou-Lagrange1972;Reva et al 1995;Stepanian et al 1998a;Ivanov et al 1997Ivanov et al , 1999Bazsó et al 2012a, b) and many other amino acids were thoroughly studied by MI-IR spectroscopy, including alanine (Rosado et al 1997;Stepanian et al 1998b;Lambie et al 2003;Bazsó et al 2013), valine (Stepanian et al 1999), leucine (Sheina et al 1988), isoleucine (Boeckx and Maes 2012a), proline (Reva et al 1994;Stepanian et al 2001), serine (Lambie et al 2004;Jarmelo et al 2005;Jarmelo et al 2006), phenylalanine (Kaczor et al 2006), tyrosine (Ramaekers et al 2005), tryptophan (Kaczor et al 2007), cysteine (Dobrowolski et al 2007), asparagine (Boeckx and Maes 2012b), lysine (Boeckx and Maes 2012c), and β-alanine (Rosado et al 1997;Dobrowolski et al 2008). In a step towards understanding the structure and folding of peptides, protected amino acids, the smallest peptide models, were also investigated by this technique, including N-formylglycine (For-Gly, Wierzejewska and OlbertMajkut 2009), N-acetylglycine (Ac-Gly, Boeckx and Maes2012d), N-acetylalanine (Ac-Ala, Boeckx and Maes 2012e), N-acetyproline (Ac-Pro, Boeckx et al 2011), N-acetylcysteine (Ac-Cys, Boeckx et al 2010), Nacetyl-N′-methyl-glycine-amide (Ac-Gly-NHMe, Grenie et al1975;Pohl et al 2007), N-acetyl-N′-methyl-Lalanine-amide (Ac-L-Ala-NHMe, Grenie et al 1975;…”

The Raman spectra of serine and 3,3-dideutero-serine in aqueous solution

“…2). In keeping with the data obtained for the studied compounds in the crystalline state [6,7], in this spectral range one can expect observation of bands due to the two stretching modes of the carboxylate group (nCOO À asym and nCOO À sym) and to the bending modes of the ammonium (dNH 3 + asym 0 , dNH 3 + asym 00 and dNH 3 + sym), methylene (scissoring, dCH 2 ; wagging, vCH 2 ; twisting, twCH 2 ), methyne (dC-H and gC-H) and hydroxyl (dCOH) groups.…”

“…As it will be shown in the next sections, the data obtained for the first time for the deuterated compound provide strong support to revise the assignments previously made for the undeuterated amino acid. Previous data obtained for serine in the crystalline state (both for L-and DL-serine crystals [6,7]) were also taken into consideration to help interpretation of the spectra obtained in aqueous solution. The Raman spectra of serine and 3,3-dideutero-serine in aqueous solution are presented in Figs.…”

“…In this spectral region, crystalline serine (DL-crystal) gives rise to bands at 2976 and 2943 cm À1 , ascribed to nCH 2 asym and to both nC-H and the nCH 2 sym modes, respectively, whereas the crystal of 3,3-dideutero-serine gives rise to only a band at 2943 cm À1 (nC-H) [6]. Though being small, the observed shifts in the frequencies of these modes, in going from the aqueous solution to the crystalline state, clearly reveal the importance of the chemical environment on the vibrations of serine, including those associated with the methylene and methyne groups, which could be expected to be less sensitive to these effects.…”

“…The infrared spectra of crystalline samples of both DL-and Lserine were also recently investigated in our laboratories using an isotopic-doping/low-temperature methodology [6,7]. In the crystalline state, serine exists in the zwitterionic form and in a single conformation.…”