Immobilization of RNase S-Peptide on a single-stranded DNA-fixed gold surface and effective masking of its surface by an acridinyl poly(ethylene glycol)

Oligonucleotide-peptide conjugate was synthesized by coupling of RNase S-peptide to a 24-mer single-stranded DNA (ssDNA) oligonucleotide to be immobilized on its complementary ssDNA oligonucleotide-fixed gold surface of sensor chip or electrode. Immobilization of on the ssDNA-fixed gold surface through DNA duplex formation was confirmed by quartz crystal microbalance (QCM) and electrochemical measurements. After treating with a synthetic acridinyl poly(ethylene glycol) (APEG), specific interaction of S-protein with the S-peptide immobilized on the gold surface was demonstrated by QCM without nonspecific adsorption of unrelated proteins such as BSA and RNase A at the surfaces. This result suggested that the acridine parts of APEG could bind to the DNA duplex on the gold surface and the poly(ethylene glycol) parts were fastened on the surface to resist the adsorption of proteins. Thus, the combination of oligonucleotide-peptide conjugate, ssDNA-fixed chip and APEG with effective masking property provides a new tool for the analysis of specific peptide-protein interactions without disturbance by other unrelated proteins.     

Synthesis of a one-dimensional metal-dimer assembled system with interdimer interaction, M2(dtp)4 (M = Ni, Pd; dtp = dithiopropionato)

A metal-dimer assembled system, M(2)(dtp)(4) (M = Ni, Pd; dtp = dithiopropionate, C(2)H(5)CS(2-)), was synthesized and analyzed by the X-ray single-crystal diffraction method, UV-vis-near-IR spectra of solutions, solid-state diffuse reflectance spectroscopies, and electrical conductivity measurements. The structures exhibit one-dimensional metal-dimer chains of M(2)(dtp)(4) with moderate interdimer contact. These complexes are semiconducting or insulating, which is consistent with the fully filled d(z)2 band of M(II)(d(8)). Interdimer metal-metal distances were 3.644(2) Angstroms in Ni(2)(dtp)(4) and 3.428(2) Angstroms in Pd(2)(dtp)(4), each of which is marginally longer than twice the van der Waals radius of the metal. Interdimer charge-transfer transitions were nevertheless observed in diffuse reflectance spectra. The origin of this transition is considered to be due to an overlap of two adjacent d(sigma) orbitals, which spread out more than the d(z)2 orbital because of the antibonding d(sigma) character of the M(d(z)2)-M(d(z)2). The Ni(2)(dtp)(4) exhibited an interdimer charge-transfer band at a relatively low energy region, which is derived from the Coulomb repulsion of the 3d(sigma) orbital of Ni.     

Photocatalytic formation of dimethyllepidopterene from 9,10-dimethylanthracene via electron-transfer oxidation

[Structure: see text] Photocatalytic carbon-carbon bond formation of 9,10-dimethylanthracene (DMA) in chloroform occurs efficiently via the electron-transfer oxidation of DMA with the photoinduced electron-transfer state of 9-mesityl-10-methylacridinium ion (Acr+-Mes), followed by deprotonation from the methyl group of DMA radical cation and the radical coupling reaction between anthracenylmethyl radicals to produce dimethyllepidopterene.     

Synthesis and properties ofN-substituted azacalix[n]arenes

Side arm modifications of hexahomotriazacalix[3]arene (1) were achieved by simple synthetic methods. Compound5 has picolyl side arms and liquid-liquid extraction experiments showed that the alkali cation affinity of5 is much stronger than that of1. A chiral group was also introduced into the azacalixarene structure. Calix[4]arene was converted into dihomoazacalix[4]arene (2) in 8% yield. Clathrate formation of2 with various solvents is described. MM3 calculations were carried out onp-substituted analogs of2. The self-filled structure, in which the benzyl side arm is placed in its cavity, is the most stable structure when thep-positions of the aromatic rings carry small substituents. Strong hydrogen bonds between nitrogen and phenolic hydroxyl groups in dihomoazacalix[4]arene (2) were observed at low temperatures. The¹H-NMR signals of phenolic hydroxyl groups appeared as six singlets in the range of 9.817.1 ppm at –70°C.This paper is dedicated to the commemorative issue on the 50th anniversary of calixarenes.     

Immobilization of sunflower trypsin inhibitor (SFTI-1) peptide onto a gold surface and analysis of its interaction with trypsin

Sunflower trypsin inhibitor (SFTI-1) derived peptide having one disulfide bond could be immobilized via a thiol-disulfide exchange reaction onto a gold surface on a quartz crystal microbalance (QCM) chip. This permitted quantitative analysis of the specific interaction with trypsin.     

Synthesis of o-benzoquinones derived from [2.2]- and [3.3]paracyclophanes

Oxidation of [2.2]- and [3.3]paracyclophanols with benzeneseleninic anhydride readily afforded the corresponding cyclophane-o-quinones which showed the intramolecular charge-transfer interactions.