Measurement of Local Sodium Ion Levels near Micelle Surfaces with Fluorescent Photoinduced‐Electron‐Transfer Sensors

The Na⁺ concentration near membranes controls our nerve signals aside from several other crucial bioprocesses. Fluorescent photoinduced electron transfer (PET) sensor molecules target Na⁺ ions in nanospaces near micellar membranes with excellent selectivity against H⁺. The Na⁺ concentration near anionic micelles was found to be higher than that in bulk water by factors of up to 160. Sensor molecules that are not held tightly to the micelle surface only detected a Na⁺ amplification factor of 8. These results were strengthened by the employment of control compounds whose PET processes are permanently “on” or “off”.     

Hollow giant lipid vesicles prepared by coaxially electrospraying solutions of phospholipid and degradable polyelectrolyte

Hollow giant lipid vesicles were prepared in a single step by coaxially electrospraying separate solutions of phospholipid and a degradable polyelectrolyte. We synthesized a hydrolytically degradable cationic polyelectrolyte, poly(β-amino esters) (PBAE), and employed it as a degradable microgel template to form giant vesicles. Droplets of the phospholipid solution and the degradable polyelectrolyte solution were electrosprayed from coaxial double needles into a receiving solution. The PBAE formed a microgel by crosslinking with multivalent anions in the receiving solution, and the phospholipids formed bilayers on the microgel. Hollow giant lipid vesicles were successfully obtained and the mean diameters were 7.6 μm (C.V. 58 %). Substrates (calcein, dextran, and polymeric microparticles) were successfully encapsulated in the giant vesicles. Microscopic observations of microparticle mobility inside a giant vesicle indicated the fluidity of its aqueous interior. Investigations using fluorescently labeled PBAE also suggested the degradation of PBAE, and the release of fluorescent PBAE fragments from the encapsulated microgel, to form hollow giant lipid vesicles.     

Stereoselective synthesis of the beta-anomer of 4'-thionucleosides based on electrophilic glycosidation to 4-thiofuranoid glycals

Three types of 4-thiofuranoid glycal with different 3,5-O-silyl protecting groups were prepared and their electrophilic glycosidation was investigated. The 3,5-bis-O-(tert-butyldimethylsilyl)-4-thiofuranoid glycal (5) was obtained through mesylation of 2-deoxy-4-thio-D-erythro-pentofuranose (4) and subsequent base-promoted elimination, while thermal elimination of sulfoxide derivatives was suitable for the preparation of 3,5-O-(tetraisopropyldisiloxane-1,3-diyl) (9) and 3,5-O-(di-tert-butylsilylene) (11) 4-thioglycals. The glycosidation reactions of these 4-thioglycals were carried out, in the presence of either PhSeCl or NIS, by using silylated derivatives of uracil, thymine, cytosine, and N(6)-benzoyladenine. Among the three 4-thioglycals, 11 was found to be an excellent glycosyl donor, forming the desired beta-anomer exclusively irrespective of the nucleobase employed.     

Nuclear protein profiling of Jurkat cells during heat stress-induced apoptosis by 2-DE and MS/MS

Heat stress causes severe constraints on numerous physiological functions of cells, such as the repression of splicing of mRNA precursors. In this study, we performed proteomic profiling of a nuclear fraction of Jurkat cells during heat stress using 2-DE and LC-MS/MS. We found 10 protein spots whose expression had changed after heat stress at 43 degrees C for 30 min. Seven of those protein spots, periodic tryptophan protein 1 homolog (PWP1), importin beta-1 subunit, sumoylated protein, splicing factor 3a subunit 3 (SF3a3), TAR DNA-binding protein 43, U2 small nuclear ribonucleoprotein auxiliary factor 35 kDa subunit (U2AF35) and small ubiquitin-related modifier-1 (SUMO-1) were downregulated, while three other protein spots, Protein SET, 40S ribosomal protein SA and 60S acidic ribosomal protein P0 were upregulated by the heat stress. We focused on the downregulation of two splicing factors, which might participate in the repression of pre-mRNA processing by heat stress, leading to cell apoptosis.     

Amidino-containing Schiff base copper(II) and iron(III) chelates as a thrombin inhibitor

Four series of Schiff base copper(II) and iron(III) chelates were synthesized from 4-formyl-3-hydroxybenzamidine or 3-formyl-4-hydroxybenzamidine and various L- or D-amino acids. Their inhibitory activities for bovine alpha-thrombin (abbreviated as thrombin) were determined. The most potent thrombin inhibitor in this series is copper(II) chelate (1g') derived from 4-formyl-3-hydroxybenzamidine and D-Trp. Its Ki value, 2.7x10(-8) M, is comparable to that of Argatroban (MD-805), which is a clinically used compound. The iron(III) chelates derived from 4-formyl-3-hydroxybenzamidine and hydrophobic L-amino acids (Val, Ile, Leu, Phe, Trp, Met) also exhibited higher inhibitory potency. It appears that coordination geometry composed of metal ion, amidino group, amino acid side chain is well accommodated to the thrombin active site. From the Ki values of Schiff base metal chelates for thrombin, the structure-activity relationships between the chelates and active site of thrombin were discussed.     

Thiazolo [3,2-b]-s-triazole

2-Formamidothiazole and O-mesitylenesulfonylhydroxylamine readily gave 3-umino-2-form-amidothiazolium mesitylenesulfonate that with polyphosphoric acid gave thiazolo [3,2-b]-s-triazole. triazole. In its nmr spectrum, a long-range coupling of 1.4 Hz between H-2 and H-6 is observed.     

Total synthesis of piericidin A1 and B1 and key analogues

Full details of the total synthesis of piericidin A1 and B1 and its extension to the preparation of a series of key analogues are described including ent-piericidin A1 (ent-1), 4'-deshydroxypiericidin A1 (58), 5'-desmethylpiericidin A1 (73), 4'-deshydroxy-5'-desmethylpiericidin A1 (75), and the corresponding analogues 51, 59, 76, and 77 bearing a simplified farnesyl side chain. The evaluation of these key analogues, along with those derived from their further functionalizations, permitted a scan of the key structural features providing new insights into the role of the substituents found in both the pyridyl core as well as the side chain. A strategic late stage heterobenzylic Stille cross-coupling reaction of the pyridyl core with the fully elaborated side chain permitted ready access to the analogues in which each half of the molecule could be systematically and divergently modified. The pyridyl cores were assembled enlisting inverse electron demand Diels-Alder reactions of N-sulfonyl-1-azabutadienes, while key elements of side chain syntheses include an anti selective asymmetric aldol to install the C9 and C10 relative and absolute stereochemistry (for natural and ent-1) and a modified Julia olefination for formation of the C5-C6 trans double bond with convergent assemblage of the side chains.     

Temperature and electric field dependences of transient photocurrents in a-Si:H

Temperature and electric field dependences of photocurrents measured at fixed times after pulsed-light excitation in hydrogenated amorphous silicon have been investigated. The photocurrents plotted against inverse absolute temperature for undoped samples exhibit activated behaviours. It is found that the activation energies for all different fixed times after photo-excitation and for all applied electric fields are the same. The results indicate the existence of quasi-equilibrium trapping level during the transit of excess electrons in undoped samples. However, in boron-doped samples the excess holes communicate with the effective trapping levels which move away from E_v (valence band mobility edge) during the transit within the time scale of measurement, which is consistent with the data that the width of valence band tail is wider than that of conduction band tail.     

Adsorption behavior of methylene blue and its congeners on a stainless steel surface

Methylene blue and its congeners as model dyes were adsorbed onto stainless steel particles at different ionic strengths, pH values, and ethanol contents, and the adsorption mechanism was investigated. A Fourier transform infrared spectroscopy (FTIR) analysis of the dyes adsorbed on the stainless steel plate was carried out to determine the orientations of the adsorbed dyes on stainless steel surface. The adsorption isotherms for all the dyes tested were approximated by a Langmuir equation (Q=Kq(m)C/(1+KC)) in most cases except under strongly basic conditions. From the ionic strength and ethanol content dependencies of the K value in the Langmuir equations, both the electrostatic and hydrophobic interactions were indicated to contribute to the adsorption of the dyes at neutral pH. By comparing the K and q(m) values for the methylene blue congeners and with the aid of the FTIR analyses, it was found that the kind of substituent groups at most positions of the polyheterocycles of methylene blue strongly affects the adsorption behavior, particularly the area occupied by an adsorbed dye molecule, the affinity for the stainless steel surface, and the orientation of the adsorbed dye molecule on the stainless steel surface.     

Reaction of electron deficient NN bonds with acyloxyketenes and mesoionic 1,3-dioxolium-4-olates: fast equilibrium between acyloxyketenes and mesoionic 1,3-dioxolium-4-olates

Reaction of azodicarboxylates with acyloxyketenes arising from dehydrochlorination of acyloxyphenylacetyl chlorides was carried out to give triacylamidine derivatives in good yields. The same triacylamidine derivatives were also obtained in good yields from the reaction with mesoionic 1,3-dioxolium-4-olates generated by Rh₂(OAc)₄-catalyzed decomposition of phenyldiazoacetic anhydride derivatives. Formation of the same compounds from different starting materials is explained by 1,3-dipolar addition between electron deficient NN bonds and mesoionic 1,3-dioxolium-4-olates, indicating fast equilibrium between acyloxyketenes and mesoionic 1,3-dioxolium-4-olates.