Simple separation of isomeric sialylated N-glycopeptides by a zwitterionic type of hydrophilic interaction chromatography

Asparagine-linked oligosaccharides (N-glycans) usually show structural heterogeneity, especially in proteins with sialylated N-glycans and, therefore, their structural analysis is still very difficult. A zwitterionic type of hydrophilic interaction chromatography column with sulfobetaine functional groups (called a ZIC-HILIC column) was applied to the separation of tryptic peptides of alpha-1-acid glycoprotein. It was demonstrated that the ZIC-HILIC separation column has a selectivity for sialylated N-glycopeptides and a high capability for separation based on the structural recognition of sialylated N-glycan isomers as well as for the previously reported neutral N-glycans and N-glycopeptides. The retention characteristics of neutral and sialylated N-glycans derivatized with 2-aminopyridine (PA N-glycans) demonstrate that the retentions of the N-glycans are based primarily on hydrophilic interaction with the water-rich liquid layer generated on the surface of the ZIC-HILIC column. In addition, the electrostatic repulsion interaction shielded with counter ions effectively tunes the separation and recognition of sialylated N-glycan isomers.     

On the dynamics of ferro- and antiferro-electric liquid crystals

Abstract

In this work, a set of Landau–Ginzburg equations to investigate the dynamic properties of ferro- and antiferro-electric smectic phases is formulated on the basis of the elastic continuum theory of compressible smectics. In the present framework, the polarization electric field is consistently taken into account through the Poisson equation as seen in our previous work. As a practical application, a few numerical results are presented for the surface-stabilized geometry with inclined and chevron layer structures. An asymmetric bistable switching is found to be achieved in the chevron layer structure under an alternating external field. In an inclined layer structure, however, a symmetric switching is found to be possible. In addition, it is first presented from a theoretical standpoint that the compressible smectic layer structure may be drastically deformed in the chevron and inclined layer structures with a sufficiently large external field.     

Design of Ratiometric Fluorescent Probes Based on Arene–Metal‐Ion Interactions and Their Application to CdII and Hydrogen Sulfide Imaging in Living Cells

Non‐coordinative interactions between a metal ion and the aromatic ring of a fluorophore can act as a versatile sensing mechanism for the detection of metal ions with a large emission change of fluorophores. We report the design of fluorescent probes based on arene–metal‐ion interactions and their biological applications. This study found that various probes having different fluorophores and metal binding units displayed significant emission redshift upon complexation with metal ions, such as Ag^I, Cd^II, Hg^II, and Pb^II. X‐ray crystallography of the complexes confirmed that the metal ions were held in close proximity to the fluorophore to form an arene–metal‐ion interaction. Electronic structure calculations based on TDDFT offered a theoretical basis for the sensing mechanism, thus showing that metal ions electrostatically modulate the energy levels of the molecular orbitals of the fluorophore. A fluorescent probe was successfully applied to the ratiometric detection of the uptake of Cd^II ions and hydrogen sulfide (H₂S) in living cells. These results highlight the utility of interactions between arene groups and metal ions in biological analyses.     

Complementary structural information of positive- and negative-ion MSn spectra of glycopeptides with neutral and sialylated N-glycans

Positive- and negative-ion MSn spectra of chicken egg yolk glycopeptides binding a neutral and a sialylated N-glycan were acquired by using electrospray ionization linear ion trap time-of-flight mass spectrometry (ESI-LIT-TOFMS) and collision-induced dissociation (CID) with helium as collision gas. Several characteristic differences were observed between the positive- and negative-ion CID MSn (n = 2, 3) spectra. In the positive-ion MS2 spectra, the peptide moiety was presumably stable, but the neutral N-glycan moiety caused several B-type fragmentations and the sialylated N-glycan almost lost sialic acid(s). In contrast, in the negative-ion MS2 spectra, the peptide moiety caused several side-chain and N-glycan residue (e.g., N-acetylglucosamine (GlcNAc) residue) fragmentations in addition to backbone cleavages, but the N-glycan moieties were relatively stable. The positive-ion MS3 spectra derived from the protonated peptide ion containing a GlcNAc residue (203.1 Da) provided enough information to determine the peptide amino-acid sequence including the glycosylation site, while the negative-ion MS3 spectra derived from the deprotonated peptide containing a 0,2X1-type cross-ring cleavage (83.1 Da) complicated the peptide sequence analysis due to side-chain and 0,2X1 residue related fragmentations. However, for the structural information of the N-glycan moiety of the glycopeptides, the negative-ion CID MS3 spectra derived from the deprotonated 2,4A6-type cross-ring cleavage ion (neutral N-glycan) or the doubly deprotonated B6-type fragment ion (sialylated N-glycan) are more informative than are those of the corresponding positive-ion CID MS3 spectra. Thus, the positive-ion mode of CID is useful for the analyses of peptide amino-acid sequences including the glycosylation site. The negative-ion mode of CID is especially useful for sialylated N-glycan structural analysis. Therefore, in the structural analysis of N-glycopeptides, their roles are complementary.     

A new aliphatic ester of hydroxysalicylic acid from fermented Carica papaya L. preparation with a potential hair growth stimulating activity

Abstract

An aliphatic ester of hydroxysalicylic acid (6), reported for the first time from a natural source in addition to five known compounds were isolated from the fermented Carica papaya L. preparation, a commercialized functional food. The known compounds were identified as 5-hydroxymethylfurfuraldehyde (1), trans-caffeic acid (2), butyl 4-hydroxybenzoate (butylparaben) (3), lycopene (4), benzyl isothiocyanate (5). Compounds 1 and 3 were reported for the first time from Papaya fruits through this study. The new compound showed a moderate antioxidant activity and a potent hair growth stimulating activity in vitro.     

Synthesis and catalysis of di- and tetranuclear metal sandwich-type silicotungstates [(gamma-SiW10O36)2M2(mu-OH)2]10- and [(gamma-SiW10O36)2M4(mu4-O)(mu-OH)6]8- (M = Zr or Hf)

The di- and tetranuclear metal sandwich-type silicotungstates of Cs10[(gamma-SiW10O36)2{Zr(H2O)}2(mu-OH)2] x 18 H2O (Zr2, monoclinic, C2/c (No. 15), a = 25.3315(8) A, b = 22.6699(7) A, c = 18.5533(6) A, beta = 123.9000(12) degrees, V = 8843.3(5) A(3), Z = 4), Cs10[(gamma-SiW10O36)2{Hf(H2O)}2(mu-OH)2] x 17 H2O (Hf2, monoclinic, space group C2/c (No. 15), a = 25.3847(16) A, b = 22.6121(14) A, c = 18.8703(11) A, beta = 124.046(3) degrees, V = 8974.9(9) A(3), Z = 4), Cs8[(gamma-SiW10O36)2{Zr(H2O)}4(mu4-O)(mu-OH)6] x 26 H2O (Zr4, tetragonal, P4(1)2(1)2 (No. 92), a = 12.67370(10) A, c = 61.6213(8) A, V = 9897.78(17) A(3), Z = 4), and Cs8[(gamma-SiW10O36)2{Hf(H2O)}4(mu4-O)(mu-OH)6] x 23 H2O (Hf4, tetragonal, P4(1)2(1)2 (No. 92), a = 12.68130(10) A, c = 61.5483(9) A, V = 9897.91(18) A(3), Z = 4) were obtained as single crystals suitable for X-ray crystallographic analyses by the reaction of a dilacunary gamma-Keggin silicotungstate K8[gamma-SiW10O36] with ZrOCl2 x 8 H2O or HfOCl2 x 8 H2O. These dimeric polyoxometalates consisted of two [gamma-SiW10O36](8-) units sandwiching metal-oxygen clusters such as [M2(mu-OH)2](6+) and [M4(mu4-O)(mu-OH)6](8+) (M = Zr or Hf). The dinuclear zirconium and hafnium complexes Zr2 and Hf2 were isostructural. The equatorially placed two metal atoms in Zr2 and Hf2 were linked by two mu-OH ligands and each metal was bound to four oxygen atoms of two [gamma-SiW10O36](8-) units. The tertanuclear zirconium and hafnium complexes Zr4 and Hf4 were isostructural and consisted of the adamantanoid cages with a tetracoordinated oxygen atom in the middle, [M4(mu4-O)(mu-OH)6](8+) (M = Zr or Hf). Each metal atom in Zr4 and Hf4 was linked by three mu-OH ligands and bound to two oxygen atoms of the [gamma-SiW10O36](8-) unit. The tetra-nuclear zirconium and hafnium complexes showed catalytic activity for the intramolecular cyclization of (+)-citronellal to isopulegols without formation of byproducts resulting from etherification and dehydration. A lacunary silicotungstate [gamma-SiW10O34(H2O)2](4-) was inactive, and the isomer ratio of isopulegols in the presence of MOCl2 x 8 H2O (M = Zr or Hf) were much different from that in the presence of tetranuclear complexes, suggesting that the [M4(mu4-O)(mu-OH)6](8+) core incorporated into the POM frameworks acts as an active site for the present cyclization. On the other hand, the reaction hardly proceeded in the presence of dinuclear zirconium and hafnium complexes under the same conditions. The much less activity is possibly explained by the steric repulsion from the POM frameworks in the dinuclear complexes.     

Measurement of attachment force of microbial cells

A parallel-plate flow chamber consisting of two transparent electro-conductive glass plates was constructed. The two glass plates were set parallel to each other and connected to a potentiostat apparatus to regulate the strength of the electric field between the plates. A microbial cell suspension was flowed through the chamber. This system enabled the application of an electrostatic force to suspend charged particles, e.g. microbial cells, existing between the two plates. The time course of the cell attachment of Pseudomonas syringae pv. atropurpurea NIAES 1309 suspended in 10 mM phosphate buffer solution (pH 7.0) to the glass plate was investigated at various electric field strengths ranging from −4.2 to +4.1 V cm⁻¹. The attachment rate and the maximum number of attached cells increased linearly with the increase in the strength of the positive electric field. In contrast, the rate and the number of cells decreased linearly with the decrease in the strength of the negative electric field. These linear relations gave a specific value for the strength of the electric field (−5.9 ± 0.7 V cm⁻¹) where the electrostatic repulsion and the microbial attachment force were thought to be equal, resulting in no cell attachment. From this value, the electrostatic repulsion, i.e. the microbial attachment force, was calculated to be 5.0 × 10⁻¹¹ N cell⁻¹ for cells of average size.     

Novel gas chromatography-mass spectrometry database for automatic identification and quantification of micropollutants

A novel gas chromatography-mass spectroscopy (GC-MS) database for identification and quantification of micropollutants in environmental and food samples is reported. GC retention times, calibration curves, and mass spectra of nearly 700 chemicals were registered in the database, and the GC retention times of registered chemicals in actual samples were predicted from the retention times of n-alkanes measured before sample analysis. Differences between predicted and actual retention times were less than 3 s, an accuracy that is nearly identical to that obtained by analysis of standard substances. After the retention times were predicted, a calibration file for the GC-MS instrument was created from the predicted retention times, calibration curves, and mass spectra of the registered chemicals. With the resulting calibration file, automated identification of all the chemicals in actual samples was possible without the use of standards, and the identification method was as reliable as conventional methods. When the GC inlet, column, and tuning conditions were adjusted using GC-MS performance check standards, relative standard deviations of 20% or less for determination values could be obtained. More than 90% of the chemicals in the database could be detected at a sensitivity sufficient for all practical purposes (100 pg or less). Because each chemical in the database, to which new substances can easily be added, can be determined in 1 h, micropollutants in samples can be analyzed efficiently and inexpensively.