Investigations of the supramolecular structure of individual diphenylalanine nano- and microtubes by polarized Raman microspectroscopy.
Polarized Raman microspectroscopy and atomic force microscopy were used to obtain quantitative information regarding the molecular structure of individual diphenylalanine (FF) nano- and microtubes. The frequencies of the Raman spectral bands corresponding to the amide I (1690 cm(-1)) and amide III (1249 cm(-1)) indicated that the FF-molecules interact by hydrogen bonding at the N-H and not at the C═O sites. The calculated mean orientation angles of the principal axes of the Raman tensors (PARTs) obtained from the polarized Raman spectral measurements were 41 ± 4° for the amide I and 59 ± 5° for amide III. On the basis of the orientation of the PART for the amide I mode, it was found that the C═O bond is oriented at an angle of 8 ± 4° to the tube axis. These values did not vary significantly with the diameter of the tubes (range 400-1700 nm) and were in agreement with the molecular structure proposed previously for larger crystalline specimens.
School of Physics and Astronomy, University of Nottingham, Nottingham, United Kingdom.
Banyat
B
Lekprasert
Vladimir
V
Korolkov
Alexandra
A
Falamas
Vasile
V
Chis
Clive J
CJ
Roberts
Saul J B
SJ
Tendler
Ioan
I
Notingher
D000577:Amides / Q000737:chemistry; D004151:Dipeptides; D006860:Hydrogen Bonding; D018625:Microscopy, Atomic Force; D008859:Microscopy, Polarization; D008958:Models, Molecular; D043942:Nanotubes / Q000737:chemistry* / Q000648:ultrastructure; D010316:Particle Size; D010649:Phenylalanine / Q000031:analogs & derivatives* / Q000737:chemistry; D013059:Spectrum Analysis, Raman
D000577:Amides; D004151:Dipeptides; C026650:phenylalanylphenylalanine; D010649:Phenylalanine