Ultrathin and Highly Tough Hydrogel Films for Multifunctional Strain Sensors.

With good flexibility and biocompatibility, hydrogel-based sensors have been widely used in human motion detection, artificial intelligence, human-machine interface, and other fields. Previous research on hydrogel-based sensors has focused on improving the mechanical properties and signal transmission sensitivity. With the development of human smart devices, there is an increasing demand for hydrogel sensor comfort and more application functions, such as ultrathin structures and recognition functions for contact surfaces, which are realized with higher requirements for the thickness, flexibility, friction resistance, and biocompatibility of hydrogels. Inspired by the ultrathin and flexible characteristics of human organ biofilms, we constructed conductive hydrogel films by using the flim-casting and glycerol-H2O secondary hydration methods. This ultrathin structure enables the hydrogel films to have a high elongation at break of 523.3%, a stress of 3.5 MPa, and a good friction resistance. Combined with the excellent sensing properties (gauge factor = 2.1 and a response time of 200 ms), the hydrogel film-based sensor can not only record human motion signals but also recognize the surface texture and roughness of objects, such as glass, brushes, wood, and sandpaper with mesh sizes of 80, 50, and 24, accurately. In addition, this hydrogel film has a series of excellent properties such as UV shielding, antiswelling ability, and good biocompatibility. This research provides a novel way for the development of emerging soft-material smart devices, such as hydrogel-based electronic skin and soft robots.

Preparation and characterization of double crosslinked hydrogel films from carboxymethylchitosan and carboxymethylcellulose.

A novel crosslinked hydrogel film was prepared from carboxymethylchitosan (CMCS) and carboxymethylcellulose (CMC) by ionical and covalent crosslinking with CaSO4 and genipin, respectively. The swelling ratio of the crosslinked CMCS/CMC hydrogel films was investigated at different pH solutions (1-9), and the results indicated that the crosslinked hydrogels had the swelling-deswelling properties with two primary peaks of swelling ratio at pH 3 and 7. The surface morphologies of the crosslinked hydrogels at different pH values provided evidences of the swelling-deswelling properties. The mechanical properties of the hydrogel films were also examined. The ionical and covalent crosslinking were found to have the primary impact on the toughness and max load, respectively, of the crosslinked hydrogels. The cells comparatively cultured on the crosslinked hydrogels and the negative and positive controls suggested the biocompatibility of the crosslinked CMCS/CMC films. This kind of hydrogel films have potential application in drug delivery vehicles and skin tissue engineering.

Carbohydrate functionalization using cationic iron carbonyl complexes.

Cationic iron carbonyl cyclohexadiene complexes were employed in the derivatization of the 3-OH position of unprotected and protected methyl beta-D-galactopyranosides using two different approaches, giving access to galactopyranosides with an aromatic or cyclohexadienoic functionality in this position.

Facile synthesis of methyl alpha- and beta-D-[6-(3)H]galactofuranosides from D-galacturonic acid. Substrates for the detection of galactofuranosidases.

Galactofuranose metabolism is a good target for the development of novel chemotherapeutic agents for the treatment of some microbial infections. A simple procedure for the synthesis of methyl (methyl alpha,beta-D-galactopyranosid)uronate followed by NaB(3)H(4) reduction gave a straightforward access to radiolabeled substrates for galactofuranosidases.

Unconventional methyl galactan synthesized via the thexyldimethylsilyl intermediate: preparation, characterization, and properties.

Reaction of a beta-(1 --> 4) linked galactan with TDMS chloride followed by methylation and desilylation yields methyl galactans with unconventional functionalization patterns. The products were characterized via FTIR and NMR of the intact polymer and by CE after controlled depolymerization. A TDMS-derivatized methyl galactan contains differently methylated secondary hydroxyl groups. SEC and analytical ultracentrifugation showed a consistent decrease in the molecular weight after the consecutive reaction steps. Biological studies revealed that the methyl galactans are less active in complement fixation assays as compared with a 3-O-methyl galactan-enriched polysaccharide fraction isolated from Acanthus ebracteatus.

Regioselective synthesis of long-chain ethers and their sulfates derived from methyl beta-D-galactopyranoside and derivatives via dibutylstannylene acetal intermediates.

A number of different conditions were investigated for the alkylation of the dibutylstannylene acetals of methyl beta-d-galactopyranoside with long-chain primary alkyl bromides, decyl, dodecyl, and tetradecyl bromide. The best yields of the major products, the 3-O-alkyl ethers, were obtained by reaction of the alkyl bromide with the monodibutylstannylene acetal in DMF in the presence of cesium fluoride for extended periods of time at moderate temperatures (65 degrees C). These products were always accompanied by minor amounts of the 3,6-di-O-alkyl derivative. Performing the reaction with excess alkyl halide on the bis(dibutylstannylene) acetal resulted in more of the 3,6-di-O-alkyl derivative, particularly for the shorter alkyl bromides, but this product was never predominant. Sulfation of the dibutylstannylene acetal of methyl 3-O-tetradecyl-beta-D-galactopyranoside resulted in the 6-sulfate in 96% yield.

Synthesis of oligosaccharide derivatives related to those from sanqi, a Chinese herbal medicine from Panax notoginseng.

Oligosaccharide derivatives from sanqi, a Chinese herbal medicine derived from Panax notoginseng, methyl beta-D-galactopyranosyl-(1-->3)-[alpha-L-arabinofuranosyl-(1-->6)]-alpha-D-galactopyranoside, diosgenyl beta-D-galactopyranosyl-(1-->3)-[alpha-L-arabinofuranosyl-(1-->6)]-alpha-D-galactopyranoside, and methyl beta-D-galactopyranosyl-(1-->3)-[alpha-L-arabinofuranosyl-(1-->6)]-alpha-D-galactopyranosyl-(1-->4)-beta-D-galactopyranosyl-(1-->3)-[alpha-L-arabinofuranosyl-(1-->6)]-alpha-D-galactopyranoside, were synthesized under standard glycosylation conditions. An unexpected alpha-(1-->4) linkage was formed predominantly in the presence of neighboring participation group during regioselective synthesis of hexasaccharide via 3+3 strategy.

Inhibition of the phosphoenolpyruvate:lactose phosphotransferase system and activation of a cytoplasmic sugar-phosphate phosphatase in Lactococcus lactis by ATP-dependent metabolite-activated phosphorylation of serine 46 in the phosphocarrier protein HPr.

Lactococcus lactis takes up lactose and the nonmetabolizable lactose analogue, thiomethyl-beta-galactoside (TMG), via the phosphoenolpyruvate:sugar phosphotransferase system (PTS) which couples sugar transport to sugar phosphorylation. Earlier studies had shown that TMG-phosphate, previously accumulated in L. lactis cells, is rapidly dephosphorylated in the cytoplasm and effluxes from the cells upon addition of glucose and that glucose inhibits further uptake of TMG. We have developed a vesicular system to analyze this regulatory mechanism and have used electroporation to shock proteins and membrane-impermeable metabolites into the vesicles. Uptake of TMG was dependent on an energy source, effectively provided by intravesicular phosphoenolpyruvate at low concentrations or extravesicular phosphoenolpyruvate at high concentrations. TMG uptake into osmotically shocked vesicles was only weakly inhibited, and expulsion of preaccumulated TMG was only slightly stimulated upon addition of glucose. Intravesicular (but not extravesicular) wild-type HPr of Bacillus subtilis completely restored the regulatory behavior observed in vivo when glucose was present in the external medium. Glucose could be replaced by intravesicular (but not extravesicular) fructose 1,6-diphosphate, gluconate 6-phosphate, or 2-phosphoglycerate, but not by other phosphorylated metabolites, in agreement with the allosteric activating effects of these compounds on HPr(Ser) kinase measured in vitro. Intravesicular mutant HPr(S46A) protein could not promote regulation of lactose permease activity when electroporated into the vesicles regardless of the presence or absence of glucose or the various phosphorylated metabolites, but the HPr(S46D) mutant protein promoted regulation, even in the absence of glucose or a metabolite, and HPr(H15A) was more effective than the wild-type protein in promoting regulation. Intravesicular wild-type and H15A HPrs, but not the S46A or S46D mutant proteins, were found to be phosphorylated by ATP under the conditions which promoted TMG efflux. In toluenized vesicles, the conditions which promoted TMG efflux also promoted TMG-P hydrolysis. These results establish for the first time that HPr serine phosphorylation by the ATP-dependent metabolite-activated HPr kinase regulates the expulsion of intracellular sugar-phosphate as well as the uptake of sugar via the PTS in L. lactis.

Synthesis of a series of methyl beta-glycosides of (1----6)-beta-D-galacto-oligosaccharides having one residue deoxygenated at position 3.

Methyl beta-glycosides of beta-(1----6)-linked D-galactobioses (13 and 16) and -galactotrioses (21, 24, and 26) containing a 3-deoxy-beta-D-xylo-hexopyranosyl moiety either as one of the end units or the internal unit have been synthesized. The extension of the oligosaccharide chain was achieved, inter alia, by the use of two newly synthesized glycosyl donors derived from 3-deoxy-D-xylo-hexopyranose, namely, 2,4,6-tri-O-benzoyl-3-deoxy-a-D-xylo-hexopyranosyl chloride (8) and 2,4-di-O-benzoyl-6-O-bromoacetyl-3-deoxy-a-D-xylo-hexopyranosyl chloride (10). Glycosylation reactions were mediated by silver triflate under base-deficient conditions.

Preparation and calculated conformations of the 2'-, 3'-, 4'-, and 6'-deoxy, 3'-O-methyl, 4'-epi, and 4'- and 6'-deoxy-fluoro derivatives of methyl 4-O-alpha-D-galactopyranosyl-beta-D-galactopyranoside (methyl beta-D-galabioside).

The glycosyl chlorides of the 3-O-methyl (6) and 4-deoxy-4-fluoro (8) O-benzylated derivatives of D-galactopyranose and 2,3,4,6-tetra-O-benzyl-D-glucopyranose were condensed with methyl 2,3,6-tri-O-benzoyl-beta-D-galactopyranoside to give, after deprotection, the 3'-O-methyl (23), 4'-deoxy-4'-fluoro (25), and 4'-epi (27) derivatives, respectively, of methyl beta-D-galabioside (1). The glycosyl fluorides of 2,3,4-tri-O-benzyl-D-fucopyranose and the 3-deoxy (12) and 4-deoxy (16) O-benzylated derivatives of D-galactopyranose were condensed with methyl 2,3,6-tri-O-benzyl-beta-D-galactopyranoside (21), to give, after deprotection, the 6'-deoxy (31), 3'-deoxy (34), and 4'-deoxy (37) derivatives of 1, respectively. The 2'-deoxy (41) derivative of 1 was prepared by N-iodosuccinimide-induced condensation of 3,4,6-tri-O-acetyl-D-galactal and 21 followed by deprotection. Treatment of methyl 2,3,6-tri-O-benzoyl-4-O-(2,3-di-O-benzoyl-alpha-D-galactopyranosyl)-beta -D- galactopyranoside with Et2NSF3 (DAST), followed by deprotection, provided the 6'-deoxy-6'-fluoro (46) derivative of 1. Molecular mechanics calculations yielded conformations for 23, 25, 27, 31, 34, 37, 41, and 46 with small deviations from the calculated conformation for 1 (phi H/psi H: -40 degrees/-6 degrees).

[Synthetic studies in the series of polyene macrolide antibiotics. 5. Synthesis of methyl-2,4,6-trideoxy-2,4-di-C-methyl-alpha-L- gluco-hexopyranoside and methyl-2,4,6-trideoxy-2,4-di-C-methyl- alpha-L-manno-hexopyranoside, the stereoisomers of the C33-C38 fragment of amphotericin B]. / Sinteticheskie issledovaniia v riadu polienovykh makrolidnykh antibiotikov. 5. Sintez metil-2,4,6-tridezoksi-2,4-di-C-metil- alpha-L-gliuko-geksopiranozida i metil-2,4,6-tridezoksi-2,4-di-C- metil-alpha-L-manno-geksopiranozina--stereoizomerov fragmenta C33-C38 amfoteritsina B.

The synthesis of the gluco- and manno-stereoisomers of amphotericin B is described.

Synthetic receptor analogues: preparation and calculated conformations of the 2-deoxy, 6-O-methyl, 6-deoxy, and 6-deoxy-6-fluoro derivatives of methyl 4-O-alpha-D-galactopyranosyl-beta-D-galactopyranoside (methyl beta-D-galabioside).

The 2-deoxy (7), 6-O-methyl (15), 6-deoxy (22), and 6-deoxy-6-fluoro (31) derivatives of methyl beta-D-galabioside (1) have been synthesised. Thus, 7 was prepared by xanthate reduction using tributyltin hydride, whereas 22 was obtained by catalytic hydrogenation of a 6-deoxy-6-iodogalabioside. Regioselective monofluorination of methyl 2,3-di-O-benzoyl-beta-D-galactopyranoside with Et2NSF3 and subsequent alpha-D-galactosylation provided 31. Molecular mechanics calculations yielded similar conformations for 1, 7, 15, 22, and 31 with differences in phi H and psi H of less than 5 degrees. No indications of intramolecular hydrogen bonds, as displayed by 1 in the crystal, were found for 7, 15, 22, or 31.

2-Substituted methyl alpha-D-galactopyranosides: synthesis and binding affinity for the A and B subunits of the Griffonia simplicifolia I isolectins.

The binding affinities of the N-acetyl, N-trifluoroacetyl, N-propionyl, N-formyl, N-benzoyl, N-p-nitrobenzoyl, N-p-aminobenzoyl, and N-methyl derivatives of methyl 2-amino-2-deoxy-alpha-D-galactopyranoside and the 2-O-acetyl, -benzoyl, -benzyl, and -methyl derivatives of methyl alpha-D-galactopyranoside for the A and B subunits of the Griffonia simplicifolia I isolectins have been determined by hapten inhibition analysis of a galactomannan-isolectin precipitation system. Models for these carbohydrate-protein interactions are presented together with an interpretation of the results on the basis of electronic and steric effects.

Synthesis and characterization of methyl 6-O-alpha- and -beta-D-galactopyranosyl-beta-D-galactopyranoside.

Sequential tritylation, acetylation and detritylation of methyl beta-D-galactopyranoside gave crystalline methyl 2,3,4-tri-O-acetyl-beta-D-galactopyranoside (4) and methyl 2,3,6-tri-O-acetyl-beta-D-galactopyranoside, the latter being the minor product resulting from acetyl migration. Reaction of 4 with 2,3,4,6-tetra-O-acetyl-alpha-D-galactosyl bromide in benzene, in the presence of mercuric cyanide and mercuric bromide, gave the alpha- and beta-D-(1----6)-linked disaccharides (7 and 9, respectively) in high yield, and their structure was confirmed by 1H- and 13C-n.m.r. 1d. and 2d. spectroscopy. O-Deacetylation of 7 gave the hitherto unknown, crystalline methyl 6-O-alpha-D-galactopyranosyl-beta-D-galactopyranoside. O-Deacetylation of 9 gave the corresponding, beta-D-linked disaccharide methyl glycoside, the physical constants of which are discussed with respect to controversial data in the literature.

Synthesis and conformational properties of methyl 6,6-di-C-methyl-beta-D-galactopyranoside. Probes for the combining sites of D-galactosyl-binding proteins.

The binding of D-galactopyranosyl groups by lectins and antibodies can involve the 5-hydroxymethyl group. In order to examine the nature of these binding reactions, it was of interest to synthesize 6,6-di-C-methyl-D-galactose which was found to exist, like D-galactose, extensively in the pyranose forms. 2,3,4,6-Tetra-O-acetyl-7-deoxy-6-C-methyl-alpha-D-galacto-heptopyranosyl bromide was prepared under standard conditions and converted into methyl 6,6-di-C methyl-beta-D-galactopyranoside (6). Evidence based on 13C-n.m.r. studies indicates that the favored conformer of 6 has O-4 and O-6 in syn-axial-like relationship. General comments are presented on the nature of the binding of oligosaccharides by proteins.

Preparation of two methyl deoxyfluoro-beta-D-galactopyranosides, and their interaction with galactan-specific immunoglobulin A J539 (Fab').

Methyl 2-deoxy-2-fluoro-beta-D-glactopyranoside (2) and methyl 4-deoxy-4-fluoro-beta-D-glactopyranoside (7) have been prepared, and the possibility of their binding to (1 leads to 6)-beta-D-galactopyranan-specific immunoglobulin A J539 (Fab') has been investigated. Compound 2 does not show binding, whereas 7 does. It appears that the 2-hydroxyl group of methyl beta-D-galactopyranoside may take part in hydrogen bonding to the protein.