Screening of an α-amylase inhibitor peptide by photolinker-peptide array.

Peptide arrays in which peptides were immobilized on cellulose membranes through photolinkers were synthesized. The peptides were subsequently detached from the arrays by ultraviolet (UV) photolysis for 3 h, and were used to search for functional peptides that inhibit the activity of α-amylase derived from human pancreatic juice. Amino acid replacement with high-molecular-size amino acids, Arg (R), Phe (F), Trp (W), or Tyr (Y), for the first and seventh residues of amylase inhibitor peptide, GHWYYRCW, as previous reported, led to enhancement of the inhibitory effect of the peptide on α-amylase. In particular, one of the resulting peptides, RHWYYRYW, showed a stronger inhibitory effect than acarbose (which is used as a hypoglycemic agent) or inhibitor peptide GHWYYRCW.

Peptide array-based characterization and design of ZnO-high affinity peptides.

Peptides with both an affinity for ZnO and the ability to generate ZnO nanoparticles have attracted attention for the self-assembly and templating of nanoscale building blocks under ambient conditions with compositional uniformity. In this study, we have analyzed the specific binding sites of the ZnO-binding peptide, EAHVMHKVAPRP, which was identified using a phage display peptide library. The peptide binding assay against ZnO nanoparticles was performed using peptides synthesized on a cellulose membrane using the spot method. Using randomized rotation of amino acids in the ZnO-binding peptide, 125 spot-synthesized peptides were assayed. The peptide binding activity against ZnO nanoparticles varied greatly. This indicates that ZnO binding does not depend on total hydrophobicity or other physical parameters of these peptides, but rather that ZnO recognizes the specific amino acid alignment of these peptides. In addition, several peptides were found to show higher binding ability compared with that of the original peptides. Identification of important binding sites in the EAHVMHKVAPRP peptide was investigated by shortened, stepwise sequence from both termini. Interestingly, two ZnO-binding sites were found as 6-mer peptides: HVMHKV and HKVAPR. The peptides identified by amino acid substitution of HKVAPR were found to show high affinity and specificity for ZnO nanoparticles.

Screening of peptides with a high affinity for ZnO using spot-synthesized peptide arrays and computational analysis.

Metal-binding peptides have attracted attention for their usefulness in biomineralization processes. In this work screening of high affinity peptides against ZnO was performed using a combinatorial library approach with a peptide array and computational analysis. The computationally assisted peptide screening and design enabled identification of linear peptides with affinity for ZnO with limited experimentation. Starting with the screening data obtained from a random 6-mer library of 420 sequences, the characteristics of the peptides with high ZnO affinity were analyzed using a fuzzy neural network algorithm by comparison of high and low affinity peptides. Three physical properties of amino acids (hydrophobicity, isoelectric point and size) and positional information of each residue were analyzed and a peptide rule with restricted amino acids at certain positions was extracted. The average affinity for ZnO increased 2.0-fold when 300 sequences were synthesized according to the restricted random library, compared with the non-restricted library. In addition, for a peptide library with the amino acids at the restricted sites exchanged the average binding capacity decreased to 0.7-fold. Interestingly, the peptides with high ZnO affinity obtained exhibited binding specificity for ZnO. Computationally assisted screening is an invaluable means for finding peptides with limited experimentation.

An analysis of changes in the expression of cyclins A and B1 by the cell array system during the cell cycle: comparison between cell synchronization methods.

BACKGROUND: A novel high-throughput analysis, cell array system, was developed for an extensive study of the expression of genes and/or the degradation of gene products at the cellular level. To exemplify the usefulness of this system, we showed the changes in the expression level of cyclin A and B1 during the cell cycle in a single experiment. METHODS: We used the cell array system to chase the changes in cyclin A and B1 expression during the cell cycle in HeLa cells. Cells were synchronized by mitotic selection and thymidine-hydroxyurea methods. Cells were harvested at intervals of 1 h from 0 through 23 h. These 48 cell samples were spotted on a circle of the cell array glass slide. Cyclin A and B1 were immunologically stained with Alexa Fluor 488, and nuclear DNA was stained with propidium iodide. The amount of cyclins and nuclear DNA were simultaneously measured by a laser scanning cytometer. RESULTS: Both cyclins were expressed in a cell cycle-dependent manner as previously reported. The precise time-course of the expression level of cyclins were obtained at a single experiment with this cell array system. CONCLUSIONS: This study indicates that the cell array system is valuable to analyze temporal course of protein expression in relation to the cell cycle position and, that it facilitates antigen expression studies at the cellular level in multiple samples.

Efficient 340-nm light generation by a ridge-type waveguide in a first-order periodically poled MgO:LiNbO3.

Quasi-phase-matched (QPM) UV second-harmonic generation (SHG) in a periodically poled MgO:LiNbO3 waveguide is presented. A ridge-type waveguide with high nonlinearity and strong resistance to photorefractive damage was achieved by use of an ultraprecision machining technique. By use of this waveguide in 1.4-microm periodically poled MgO:LiNbO3, a first-order QPM SHG device for 340-nm UV radiation was demonstrated. In a single-pass configuration, continuous-wave 22.4-mW UV light was generated for a fundamental power of 81 mW, corresponding to a normalized conversion efficiency of 340%/W.

Generation of 360-nm ultraviolet light in first-order periodically poled bulk MgO:LiNbO3.

Ultraviolet second-harmonic generation in first-order periodically poled MgO:LiNbO3 is presented. Using a high-voltage multipulse application method, we fabricated a first-order nonlinear grating with a period of 1.8 microm and depth of approximately 150 microm over 10-mm interaction length in a 1-mm-thick MgO:LiNbO3 substrate. In a single-pass configuration, continuous-wave 30-mW UV light at 362.5 nm was generated for a fundamental power of 522 mW, corresponding to a normalized conversion efficiency of 11%/W.