Equilibrium Geometries and Structural Stability of the AlmNan (m = 2-4; n = 1-8) Clusters.

The stable geometries and formation processes of the AlmNan (m = 2-4; n = 1-8) clusters were investigated using the density functional theory (DFT). The Alm (m = 2-4) structures are maintained in the clusters. The Na atoms are attached to the Al-Al bond or Al plane for less than n = 4 in the AlmNan (m = 2-4) clusters. The odd electron of the attached Na atom is transferred to the Alm part for n ≤ 4 or 5 in the AlmNan (m = 2-4) clusters since the Alm part becomes stable. The Na-Na bonding is formed by the attached Na atom after saturation of the Al-Al bonds or Al atoms. The Al2Na5, Al3Na5, Al3Na6, Al3Na7, and Al3Na8 clusters have a characteristic structure. The Na wing is formed in the Al3Nan (n = 5-8) clusters. The 2S shell containing the 3s orbital of the Na atom and the 3p orbital of the Al atom becomes stable before the occupation of the 1D shell because the electrons are delocalized on the Na plane for n ≥ 5 in the AlmNan (m = 2-4) clusters. The stability of the AlmNan (m = 2-4; n = 1-8) clusters was evaluated by comparison of the vertical ionization potential (IP), HOMO-LUMO gap, adsorption energy of the Na atom, and binding energy per atom.

Mannosylerythritol lipids, yeast glycolipid biosurfactants, are potential affinity ligand materials for human immunoglobulin G.

Three mannosylerythritol lipids (MEL-A, -B, and -C), yeast glycolipid biosurfactants, were independently attached to poly (2-hydroxyethyl methacrylate) beads (PHEMA), and the three obtained MEL-PHEMA composites were examined for their binding affinity to human immunoglobulin G (HIgG). Of the three composites, the composite bearing MEL-A exhibited the highest binding capacity for HIgG. The binding amount of HIgG increased with increased applied concentration, reaching 106 mg HIgG (per g of composite), with a binding yield of 81%. Interestingly, the protein binding to the composite appeared to follow two different modes (Langmuir type and Freundlich type) depending on the applied concentration. The binding amount of human serum albumin to the composite was much smaller than that of HIgG. The bound human serum albumin, however, had minimal effect on the subsequent binding of HIgG, indicating that the two proteins have different binding sites onto the composite. More significantly, the bound HIgG was efficiently recovered under significantly mild elution conditions: Approximately 90% of the protein was eluted from the composite with phosphate buffer at pH 7. These results indicate that the glycolipid biosurfactant may have great potential as an affinity ligand material for HIgG.