Antigen�Cantibody interactions of influenza virus hemagglutinin revealed by the fragment molecular orbital calculation

Effective interactions between amino acid residues in antigen?Cantibody complex of influenza virus hemagglutinin (HA) protein can be evaluated in terms of the inter-fragment interaction energy (IFIE) analysis with the fragment molecular orbital (FMO) method, in which each fragment contains the side chain of corresponding amino acid residue. We have carried out the FMO-MP2 (second-order Moeller?CPlesset) calculation for the complex of HA antigen and Fab antibody of influenza virus H3N2 A/Aichi/2/68 and obtained the IFIE values between each amino acid residue in HA and the whole antibody as the sums over the residues contained in the latter. Combining this IFIE data with experimental data for hemadsorption activity of HA mutants, we succeeded in theoretically explaining the mutations in HA observed after the emergence of influenza virus H3N2 A/Aichi/2/68 in an earlier study, except for those of THR83. In the present study, we employ an alternative way of fragment division in the FMO calculation at the carbonyl C site of the peptide bond instead of the C_?? site used in the previous work, which provides revised IFIE values consistent with all the historical mutation data in the antigenic region E of HA including the case of THR83 in the present prediction scheme for probable mutations in HA.     

Novel des-fatty acyl-polymyxin B derivatives with Pseudomonas aeruginosa-specific antimicrobial activity

Polymyxin B (PMB) is a cationic cyclic decapeptide antibiotic with a fatty acyl (FA) modification at the α-amino group of Dab1 (Dab: L-α,γ-diaminobutyric acid). In this study, which is part of a series of PMB structure-activity relationship investigations focused on identifying clinically useful peptide antibiotics, we synthesized ten des-FA PMB derivatives whose N-terminal moieties were changed to basic or hydrophilic amino acids. The antimicrobial and lipopolysaccharide (LPS) binding activities of these synthetic analogs were tested. The analogs showed more potent antimicrobial activity against Pseudomonas aeruginosa (P. aeruginosa) compared with the PMB nonapeptide. In particular, [Ser2-Dap3]-PMB(2-10), Guanyl-[Thr2-Dab3]-PMB(2-10), Guanyl-[Dab1-Thr2-Dab3]-PMB(1-10), and N(α,γ)-diguanyl-[Dap3]-PMB(3-10) had antimicrobial activity equivalent to PMB. In LPS binding assays, the displacement curves shifted in a manner proportional to the number of positive charges available to bind to Escherichia coli (E. coli) and P. aeruginosa. Furthermore, peptides with basic side chains were comparable to PMB in binding activity assays against E. coli and P. aeruginosa. The acute toxicities of the peptides were evaluated by intravenously administering the peptides to mice through the tail vein. The toxicities of [Ser2-Dap3]-PMB(2-10), [Dap3]-PMB(3-10), and [Ser3]-PMB(3-10) were lower that of PMB (LD??, 4.8 μmol/kg).     

Effects of Nb and Y substitution on negative thermal expansion of ZrV 2−XPXO7 (0≦X≦0.8)

Zirconium vanadates with a novel chemical composition including niobium and yttrium were synthesized by the sol-gel method. An aqueous solution of NH₄H₂PO₄ and NH₄V O₃ and an ethanol solution of ZrOCl₂,NbCl₅, and Y Cl₃ were prepared. These two solutions were stirred and mixed to prepare precursors of zirconium vanadates at 333 K, following the evaporation of the solvent at 363 K. The precursor gels obtained were heated at 373-973 K in air. A zirconium vanadate phase began to crystallize above 673 K and a single phase of zirconium vanadate was synthesized at 973 K. Although ZrV ₂O₇ generally had a positive thermal expansion in the temperature range above RT, the degree of positive thermal expansion decreased with the two types of substitution of P for V and a set of Nb and Y for Zr of ZrV ₂O₇. X-ray diffraction peaks due to a superlattice structure, causing a positive thermal expansion from RT, were not observed in the synthesized (Nb, Y)-substituted zirconium vanadates.     

Nitroxyl radicals: electrochemical redox behaviour and structure-activity relationships

Comparative study of electrochemical redox behaviour of five different nitroxyl radicals leads to the direct correlation between one-electron redox potentials and group electronegativity of the beta-substituent on the ring. Beta-substituents with an electron-donating effect caused a negative shift in the one-electron oxidation and one-electron reduction potentials of the nitroxyl radicals. In a similar aspect, beta-substituents with an electron-withdrawing effect behaved oppositely.     

Frozen water phase method for logD measurement using a 96-well plate

In this study, a frozen water phase method for log D measurement using a 96-well plate was developed. In the case of log D measurement of compounds, the problem of octanol contamination often occurs; in lipophilic compounds, the concentration of the octanol phase is much higher than that of the water phase. When the water phase is separated from the octanol phase, a small amount of octanol phase contamination could strongly influence the concentration of the water phase. To avoid this problem, the frozen water phase method was developed. The water phase was frozen in liquid nitrogen and then the unfrozen octanol phase was removed. To remove the portion of the octanol remaining on the frozen water phase, the surface of the frozen water phase was washed with octanol and water/ethanol (50/50, v/v). The validity of the method was confirmed by results of commercially available drugs at the log D range from 0 to 4. Further, it was found that this method had the ability to evaluate the pH-log D profile of compounds in the range from pH 2 to pH 12. As a result, we developed the convenient and accurate method that is effective in preventing contamination with a wide dynamic range.     

Gravitational sedimentation effect of colloidal silica crystals in binary systems of titanium dioxide and silica particles

Colloidal crystals can be formed of silica particles while those of titania particles are not known under the normal gravitational field, because of their high specific gravity. We found by the Kikuchi--Kossel diffraction technique that, when silica particles (diameter: D?=?170?nm; density: ρ?=?2.2?g cm^?3) are mixed with titania particles (D?=?127?nm; ρ?=?3.9?g cm^?3), colloidal crystals are formed. Colloidal crystals started out with body-centred-cubic structure and changed to face-centred-cubic structures after about 60 days. Transitions began from the bottom of the container. Thus, the transitions are considered to be due to gravitational sedimentation. It is significant that the crystal growth process, which has not been observed in one-component dispersions of the silica particles, was found using titania particles with a wide range of the practical applicability.     

A Fluorine-19 Magnetic Resonance Probe,Shiga-Y5, Downregulates Thioredoxin-Interacting Protein Expression in the Brain of a Mouse Model of Alzheimer’s Disease

Thioredoxin-interacting protein (TXNIP) is involved in multiple disease-associated functions related to oxidative stress, especially by inhibiting the anti-oxidant- and thiol-reducing activity of thioredoxin (TXN). Shiga-Y5 (SY5), a fluorine-19 magnetic resonance probe for detecting amyloid-β deposition in the brain, previously showed therapeutic effects in a mouse model of Alzheimer’s disease; however, the mechanism of action of SY5 remains unclear. SY5 passes the blood–brain barrier and then undergoes hydrolysis to produce a derivative, Shiga-Y6 (SY6), which is a TXNIP-negative regulator. Therefore, this study investigates the therapeutic role of SY5 as the prodrug of SY6 in the thioredoxin system in the brain of a mouse model of Alzheimer’s disease. The intraperitoneal injection of SY5 significantly inhibited TXNIP mRNA (p = 0.0072) and protein expression (p = 0.0143) induced in the brain of APP/PS1 mice. In contrast, the levels of TXN mRNA (p = 0.0285) and protein (p = 0.0039) in the brain of APP/PS1 mice were increased after the injection of SY5. The ratio of TXN to TXNIP, which was decreased (p = 0.0131) in the brain of APP/PS1 mice, was significantly increased (p = 0.0072) after the injection of SY5. These results suggest that SY5 acts as a prodrug of SY6 in targeting the thioredoxin system and could be a potential therapeutic compound in oxidative stress-related diseases in the brain.     

Phase transition and extended X-ray absorption fine structure of melt-spun amorphous Fe100−xYx alloys

The phase diagram and local structure of melt-spun amorphous (a-) Fe_100−xY_x (22?x?62) alloys were investigated using AC and DC magnetic and extended X-ray absorption fine structure (EXAFS) measurements. The a-Fe–Y system shows reentrant spin glass (RSG) behavior for 42?x?58 and spin glass (SG) behavior for 60?x. Two SG transition temperatures, T_g and T_f, were obtained in the RSG state. The T_g, T_f and Curie temperature T_C decrease with increasing x, and the T_C and T_g vanish at x=60. A new magnetic phase diagram for the melt-spun a-Fe_100−xY_x alloys was obtained from magnetic measurements for higher Y concentration. The magnetic states of the a-Fe_100−xY_x alloys change remarkably around x=60 and an EXAFS study revealed that the average atomic distance between nearest-neighboring Fe atoms changes at approximately x=60.     

Novel sample preparation technique with needle-type micro-extraction device for volatile organic compounds in indoor air samples

A novel needle-type sample preparation device was developed for the effective preconcentration of volatile organic compounds (VOCs) in indoor air before gas chromatography–mass spectrometry (GC–MS) analysis. To develop a device for extracting a wide range of VOCs typically found in indoor air, several types of particulate sorbents were tested as the extraction medium in the needle-type extraction device. To determine the content of these VOCs, air samples were collected for 30 min with the packed sorbent(s) in the extraction needle, and the extracted VOCs were thermally desorbed in a GC injection port by the direct insertion of the needle. A double-bed sorbent consisting of a needle packed with divinylbenzene and activated carbon particles exhibited excellent extraction and desorption performance and adequate extraction capacity for all the investigated VOCs. The results also clearly demonstrated that the proposed sample preparation method is a more rapid, simpler extraction/desorption technique than traditional sample preparation methods.     

Synthetic studies on β-lactam antibiotics. 19. Synthesis of 3′-nor-type 1-oxacephems

Synthesis of optically active 3′-nor-type 1-oxacephems from 6-APA was described. $\text{p}$-Nitrobenzyl 7β-amino-3-chloro-7α-methoxy-1-oxa-3-cephem-4-carboxylate $\text{39}$ was also prepared.