201004-33-3Relevant academic research and scientific papers
A safe, simple, and facile staining method using polysiloxanes for high-contrast visualization of gelator aggregates by transmission electron microscopy
Hanabusa, Kenji,Nakashima, Masashi,Funatsu, Eriko,Kishi, Sachiyo,Suzuki, Masahiro
, p. 1176 - 1185 (2018)
The staining of TEM samples using Si atoms was investigated using aggregates of loose gels formed by twelve structurally different gelators in several solvents. Thirteen commercially available siloxanes were used as stains. TEM images of non-stained and OsO4-stained samples of molecular aggregates formed by the dodecamethylenediamide of N-methacryloyloxyethylaminocarbonyl- L-isoleucine in 1-propanol were poorly defined and low-contrast. However, the image of a methacryloyloxypropyl- terminated polydimethylsiloxane (S1)- stained sample was characterized by very clear bundles of fine fibers. The staining effect was explained by the wrapping of fibers, the stabilizing of the individual fibers, and reinforcing by S1. An S1 concentration of more than 5mgmL-1 was found to be necessary for satisfactory contrast. S1 was successfully applied to the observation of aggregates of eleven other gelators. S1 worked universally as an aggregate stain regardless of the gelator or solvent polarity. The staining effect was observed for other siloxanes. This effect was found to depend on the molecular weight of the siloxane (>1, 000) rather than the kind of siloxane employed. Energy-dispersive X-ray spectroscopy indicated that the molecules of S1 gather on the surface of the fibers during drying, wrapping them. The results indicate that the present staining method guarantees reproducibility and universality.
Synthesis, conformation, and chemical properties of new mini parallel double-stranded peptides conjugated with -Phe-Phe- and - Phe-Phe-X- sequences
Kobayashi, Shigeki,Kobayashi, Hiroki,Yamaguchi, Takatoshi,Nishida, Miharu,Yamaguchi, Kentaro,Kurihara, Masaaki,Miyata, Naoki,Tanaka, Akira
, p. 920 - 934 (2007/10/03)
To investigate the chemical conformations and functions of the -Phe-Phe-Val- or -Phe-Phe- sequences contained in the Alzheimer's disease related β-amyloid peptide, a series of mini parallel double-stranded peptides conjugated with two peptide residues to one spacer were designed and prepared. The structure of the compounds was elucidated by circular dichroism (CD) spectrum and NMR two dimensional (2D) nuclear Overhauser enhancement and exchange spectroscopy (NOESY) measurments. The structure of 1,2-ethano-bis(L-Phe-L-Phe-L-Leu), 1,12-dodecano- bis(L-Phe-L-Phe-L-Leu), 1,12-dodecano-bis(L-Phe-L-Phe-L-Val), and 1,12-dodecano (D-Phe-D-Phe-D-Leu) conjugated with L-Leu and L-Val residues show a βturn-like nucleation. The dihedral angles (θ = + 75°, + 180°, ω =+ 90°, φ =- 87°, ψ =+ 180°) obtained from experimental coupling constant (J) data, etc. support that 1,12-dodecano-bis(L-Phe-L-Phe) adopts β-turn mimic nucleation. The 1,12-dodecano-bis(L-Leu-L-Leu-L-Phe), 1,12-dodecano-bis(L- Ile-L-Phe-L-Leu), and 1,12-dodecano-bis(L-Phe-L-Val-L-Leu), etc. adopt most probably a random structure by CD studies. It was found by titration spectrum that an inclusion complex of 1:1 ratio (association constant; K(a)=1.0 x l04 M-1) is formed between 1,12-dodecano-bis(L-Phe-L-Phe-L-Leu) and azobenzene (guest, [L0]=1.758 x 10-5 M-1). Moreover, the stability of the complexes was increased in order of 1,12-dodecano-bis(L-Phe- L-Phe-L-Leu) · azobenzene > 1,12-dodecano-bis(L-Phe-L-Phe-L-Val) · azobenzene > 1,12-dodecano-bis(L-Phe-L-Val-L-Leu) · azobenzene. The data show that X-Phe-L-Phe-L-spacer(S)-L-Phe-L- Phe-X (X=amino acids; S=1,2-ethano- and 1,12-dodecano-) plays an important role as a binding site of the drophobic interaction of the four Phes in the two strands is a very interesting issue in the physiological action of proteins as well as the conformation of the backbone of X-L-Phe-L-Phe-spacer(S)-L-Phe-L-Phe-X.
