Promotion of cell adhesion by low-molecular-weight hydrogel by Lys based amphiphile.

Hydrogels formed by low-molecular hydrogelators have been used as anti-microbial agents and cell-attachment materials. However the biomedical application of low-molecular gelators is slowly progressing compared to the hydrogels formed by polymer hydrogelator that is applied to biomedical application such as tissue engineering and biomedical regions. To obtain a simple molecular model for potent and prospective usage of low-molecular hydrogelators, we designed a Lys-based hydrogelator which was mimic to the poly cationic poly-l-lysine that promotes cells to attach to a plastic plate nonspecifically. The gel-coating led to cause 10-fold cell attachment compared to no-coating well. Also five-time cells were attached to the well compared to the poly-l-lysine coating. From the competitive assay, these hydrogels could interact with cells through electrostatic interaction between positive charge from -NH3(+) in the hydrogelator and negative charge from substances on the cell surface such as glycosaminoglycans. This strong adhesive ability can be useful for the tissue engineering and molecular glue regions using low-molecular hydrogels in the future.

Raman optical activity of a cyclic dipeptide analyzed by quantum chemical calculations combined with molecular dynamics simulations.

Raman optical activity (ROA) measures the different intensity of right- and left-circularly polarized Raman scattered light and provides information on chirality associated with vibrational modes. Because of a high sensitivity to subtle structural and environmental changes, interpretations of ROA spectra usually rely on quantum chemical simulations. Recent advances in computational chemistry allow us to consider explicit solvent models that are derived from molecular dynamics (MD) simulations to compute the Raman and ROA spectra. An important concern for the explicit solvent models is the number of MD snapshots that lead to a good agreement between the observed and calculated spectra. In the present study, we measured the Raman and ROA spectra of cyclo(L-Ala-Gly) and then simulated the spectra using density functional theory combined with MD simulations. Although cyclo(L-Ala-Gly) is a relatively rigid cyclic molecule, boat-up and boat-down conformations were found from the MD calculations. Because the Raman spectra of the two conformations are similar except for a lower frequency region, ∼10 MD snapshots are capable of reproducing the main features of the observed Raman spectra. In contrast, a larger number of MD snapshots was required to reproduce the ROA spectra. In the middle freqency region of 800-1580 cm(-1), an average of ∼40 spectra led to good agreement between the observed and calculated spectra. On the other hand, the low (0-800 cm(-1)) and high (1580-1800 cm(-1)) frequency regions require more than 60 and 120 MD snapshots, respectively. The Raman and ROA spectra in the low frequency region are relatively broad, and such spectral features require a larger number of averaged spectra. The high frequency region of the spectra consists of an amide I band, which is primarily a C═O stretching vibration. Since both the ROA intensity and frequency of the amide I band are highly sensitive to structural and environmental differences, a large number of the spectra need to be averaged to reproduce the small negative features in the observed ROA spectra.

Formation of ion-selective channel using cyclic tetrapeptides.

It is important for ion channel peptides to have energetic stability and ion-selectivity for development of some medicines. In the present study, our objective was to achieve formation of energetically stable and ion-selective channels in the membrane using cyclic tetrapeptides. We succeeded in formation of energetically stable and ion-selective channels using two cyclic tetrapeptides cyclo(D-Ala-Dap)(2) (Dap; l-2,3-diaminopropionic acid) and cyclo(D-Ala-Glu)(2). The results of ion channel recording suggested that the cationic cyclo(D-Ala-Dap)(2) was resulted in Cl(-) anion-selective and the anionic cyclo(D-Ala-Glu)(2) led to K(+) cation-selective ion channel formation, respectively. This ion selectivity may be attributed to the charge state of peptides. And a low-hydrophobic cyclic tetrapeptide; cyclo(D-Ala-Dap)(2) had a tendency to form stable ion channel compared to more high-hydrophobic ones; cyclo(D-Phe-Lys)(2), cyclo(D-Phe-Dap)(2) and cyclo(D-Ala-Lys)(2). Our findings will shed light on the field of ion channel peptide study, especially cyclic one.