Low‐temperature Raman spectra of racemate <scp>DL</scp>‐Alanine crystals

Lima, J.A.; Freire, Paulo; Melo, F. E. A.; Fílho, J. Mendes; Sousa, G.P. De; Lima, Ricardo Chaves; Filho, P.F. Façanha; Bordallo, Heloisa N.

doi:10.1002/jrs.2507

Cited by 18 publications

(6 citation statements)

References 35 publications

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“…Although no conclusive assignments of these two modes could be made, tentative assignments can be proposed based on previously reported Raman literature values. For example, given that the 17-residue isomer pair of CAPs each contains mainly Ala and Leu residues in the hydrophobic core segment, the mode at 1297 cm -1 may be assigned to a CH deformation of the Leu side chain [30][31][32], while the mode at 1483 cm -1 may be assigned to a CH 3 deformation of the Ala side chain [32,33].…”

Section: Discussionmentioning

confidence: 99%

Differential Binding of L- vs. D-isomers of Cationic Antimicrobial Peptides to the Biofilm Exopolysaccharide Alginate

Yin¹,

Lee²,

Mak³

et al. 2013

PPL

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Alginate is a biofilm exopolysaccharide secreted by the opportunistic pathogen Pseudomonas aeruginosa that acts to prevent the diffusion of antibiotics toward the bacterial cell membrane. Cationic antimicrobial peptides (CAPs) have been increasingly recognized as a viable alternative for prospective antimicrobial agents. The D-isomer chiral counterparts of active L-isomer CAPs tend to show slightly greater antimicrobial activities because bacteria lack proteases to hydrolyze the unnatural D-isomers. Using an enantiomeric pair of synthetic CAPs designed in our laboratory (L-4Leu in the sequence KKKKKKALFALWLAFLA-NH2 and its D-analog D-4Leu), we studied the binding and interactions of Lvs. D-isomers of CAPs with alginate using circular dichroism and Raman spectroscopic techniques. We found that the peptide D-4Leu underwent a more rapid structural transition over time from an initial alginate-induced α-helical conformation to a less soluble β-sheet conformation than L-4Leu, indicating that the D-isomer of this peptide has a relatively greater affinity for alginate. Through Raman spectroscopy it was observed that Raman modes at 1297 cm-1 and 1453 cm-1 wavenumbers were found to differ between the spectra obtained from the insoluble complexes formed between L-4Leu vs. D-4Leu and alginate. These modes were tentatively assigned to CH, and CH3 deformation modes, respectively. Our findings reveal previously undetected subtleties in the binding of this diastereomeric pair of peptides in the microenvironment of a biofilm exopolysaccharide, and provide guidelines for future development of antimicrobial peptides.

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Section: Discussionmentioning

confidence: 99%

Differential Binding of L- vs. D-isomers of Cationic Antimicrobial Peptides to the Biofilm Exopolysaccharide Alginate

Yin¹,

Lee²,

Mak³

et al. 2013

PPL

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“…Raman spectra of dl ‐alanine crystals were investigated by Lima et al . between 50 and 3200 cm −1 for temperatures ranging from 15 to 295 K . The crystal structure of dl ‐alanine represents a rare example of an amino acid racemate that crystallizes in a noncentrosymmetric space group.…”

Section: Solid‐state Studiesmentioning

confidence: 99%

Recent advances in linear and nonlinear Raman spectroscopy. Part V

Nafie

2011

J Raman Spectroscopy

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“…Thermal expansion coefficients of DL-Ala in various crystallographic directions were reported as 7.5 × 10 −5 , (3.8−5) × 10 −5 and −2.25 × 10 −6 along a, b, and c crystal axes, respectively. 17,18 Whereas the c direction is contracting, the a-and b-directions are expanding. Crystal contraction along the c direction can lead to hardening of the polarization change in this direction, which has negative influence on the pyroelectric effect.…”

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confidence: 99%

Pyroelectricity in Nonpolar Directions in Crystals: Enantiomeric Disorder and Surface Wetting in Racemic α-Amino-Acids

Mishuk

Weissbuch

Lahav

et al. 2014

Crystal Growth & Design

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Display of pyroelectricity along nonpolar directions of crystals or from surfaces implies structural disorder or presence of polar surface layers. Nonpolar {210} faces of polar DLalanine crystals display far larger pyroelectric effect than that at the polar {001} faces. Similarly, pyroelectricity is reported from {110} faces of centrosymmetric crystals of DL-aspartic acid. The origin of the disorder is due to an interchange of enantiomers at specific chiral crystal sites as supported by atom−atom potential energy computations and by pyroelectric effect observed on the nonpolar crystals of L-alanine intentionally doped with opposite enantiomers. These results should explain the riddle of the needle-like morphology of DL-alanine. The {100} faces of DLserine and the {021} faces of DL-glutamic acid monohydrate crystals exhibit pyroelectricity due to surface wetting, whereas pyroelectricity originating from the {210} faces of enantiomerically doped L-alanine crystals could be deciphered as arising both from surface wetting and enantiomeric bulk disorder.

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Low‐temperature Raman spectra of racemate DL‐Alanine crystals

Cited by 18 publications

References 35 publications

Differential Binding of L- vs. D-isomers of Cationic Antimicrobial Peptides to the Biofilm Exopolysaccharide Alginate

Differential Binding of L- vs. D-isomers of Cationic Antimicrobial Peptides to the Biofilm Exopolysaccharide Alginate

Recent advances in linear and nonlinear Raman spectroscopy. Part V

Pyroelectricity in Nonpolar Directions in Crystals: Enantiomeric Disorder and Surface Wetting in Racemic α-Amino-Acids

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