Glycopolymers are functional polymers with saccharide moieties on their side chains and are attractive candidates for biomaterials. Postpolymerization modification can be employed for the synthesis ...of glycopolymers. Activated esters are useful in various fields, including polymer chemistry and biochemistry, because of their high reactivity and ease of reaction. In particular, the formation of amide bonds caused by the reaction of activated esters with amino groups is of high synthetic chemical value owing to its high selectivity. It has been employed in the synthesis of various functional polymers, including glycopolymers. This paper reviews the recent advances in polymers bearing activated esters for the synthesis of glycopolymers by postpolymerization modification. The development of polymers bearing hydrophobic and hydrophilic activated esters is described. Although water-soluble activated esters are generally unstable and hydrolyzed in water, novel polymer backbones bearing water-soluble activated esters are stable and useful for postpolymerization modification for synthesizing glycopolymers in water. Dual postpolymerization modification can be employed to modify polymer side chains using two different molecules. Thiolactone and glycine propargyl esters on the polymer backbone are described as activated esters for dual postpolymerization modification.
Configuration random access memory (CRAM), which consists of the static random access memory susceptible to single event upset (SEU), configures all of the user logic in field-programmable gate array ...(FPGA). In this article, we evaluate the impact of SEU in CRAM on the image-based lane tracking for autonomous driving via neutron irradiation experiments. In the experiments, the cross section of bit upsets and its corresponding single event function interrupt (SEFI) in the logic function of image processing are measured. By using a virtual driving environment, we observe whether a bit upset finally induces a severe SEFI of the system failure. The system failure is observed by an abnormal behavior on the virtual autonomous car driving by lane tracking. Experimental results show the bit upset has a maximum probability of 23% to induce SEFI and finally 8% of the bit upsets lead to failures in lane tracking. All the SEFIs observed in irradiation experiments are reproduced in fault injections with the same bit address. The cross section of SEFI was estimated in fault injections with reasonable precision. Moreover, we evaluate the improvement of system reliability by the error correction against soft errors. Our evaluation result shows that the error correction within the period of two-frame processing time could reduce the 74% SEFI cross section, but it has little benefit for system failure cross section if an error happens during the period of the image processing.
Reversible temperature-responsive and lectin-recognizing glycosylated block copolymers composed of polyacrylamide (PAAm) and poly(N-isopropylacrylamide) (PNIPAm) were synthesized by consecutive RAFT ...polymerization reactions. PAAm bearing maltose moieties was synthesized by RAFT polymerization with a trithiocarbonate derivative as a chain transfer agent for chain extension and with N-isopropylacrylamide to obtain block copolymers. The resulting glycosylated block copolymers were responsive to temperature at approximately 33 °C (lower critical solution temperature; LCST) and formed aggregates 100 nm in diameter in aqueous media above the LCST. The aggregates specifically interacted with lectin in aqueous media above the LCST, forming conjugates. When the temperature was decreased below the LCST, the conjugate dissociated into the aqueous medium. The conjugates of block copolymer and lectin were reversible in response to changes in temperature.
In this paper, we presented a novel microbial fuel cell (bMFC) structure, with a bipolar membrane separating the anode and cathode chambers. A bipolar membrane divides the bMFC into anode and cathode ...chambers. The bipolar membrane comprises anion and cation exchange layers. The anode chamber side has the cation exchange layer, while the cathode chamber side has the anion exchange layer. The anode chamber of the bMFC was loaded with Shewanella oneidensis MR-1 and lactic acid, while the cathode chamber was loaded with pure water and iron (III) hydroxide. The bMFC generated electrons for 20 days at a maximum current density of 30 mA/m2 and the ohmic resistance value was estimated to be 500 Ω. During the operation of the bMFC, both the anode and cathode chambers kept anaerobic conditions. There was no platinum catalyst in the cathode chamber, which is required for the reaction of protons with oxygen. Therefore, oxygen could not serve as an electron acceptor in the bMFC. We considered a bMFC mechanism in which protons produced by S. oneidensis react with hydroxide ions, the counter anions of Fe3+, inside the bipolar membrane to produce water. In other words, the electron acceptor in bMFC would be Fe3+.
Matrix metalloproteinase (MMP)-2 and MMP-9 are well-known gelatinases that disrupt the extracellular matrix, including gelatin. However, the advantages of modulating MMP expression in gelatin-based ...materials for applications in bone regenerative medicine have not been fully clarified. In this study, we examined the effects of epigallocatechin gallate (EGCG), a major polyphenol catechin isolated from green tea, on MMP expression in gelatin sponges and its association with bone formation. Four gelatin sponges with or without EGCG were prepared and implanted into bone defects for up to 4 weeks. Histological and immunohistological staining were performed. Micro-computed tomography was used to estimate the bone-forming capacity of each sponge. Our results showed that EGCG integration attenuated MMP-2 (70.6%) and -9 expression (69.1%) in the 1 week group, increased residual gelatin (118.7%), and augmented bone formation (101.8%) in the 4 weeks group in critical-sized bone defects of rat calvaria compared with vacuum-heated gelatin sponges without EGCG. Moreover, vacuum-heated gelatin sponges with EGCG showed superior bone formation compared with other sponges. The results indicated that integration of EGCG in gelatin-based materials modulated the production and activity of MMP-2 and -9 in vivo, thereby enhancing bone-forming capacity.
Cost-effective and functionalized scaffolds are in high demand for stem-cell-based regenerative medicine to treat refractory bone defects in craniofacial abnormalities and injuries. One potential ...strategy is to utilize pharmacological and cost-effective plant polyphenols and biocompatible proteins, such as gelatin. Nevertheless, the use of chemically modified proteins with plant polyphenols in this strategy has not been standardized. Here, we demonstrated that gelatin chemically modified with epigallocatechin gallate (EGCG), the major catechin isolated from green tea, can be a useful material to induce bone regeneration in a rat congenial cleft-jaw model in vivo when used with/without adipose-derived stem cells or dedifferentiated fat cells. Vacuum-heated gelatin sponges modified with EGCG (vhEGCG-GS) induced superior osteogenesis from these two cell types compared with vacuum-heated gelatin sponges (vhGS). The EGCG-modification converted the water wettability of vhGS to a hydrophilic property (contact angle: 110° to 3.8°) and the zeta potential to a negative surface charge; the modification enhanced the cell adhesion property and promoted calcium phosphate precipitation. These results suggest that the EGCG-modification with chemical synthesis can be a useful platform to modify the physicochemical property of gelatin. This alteration is likely to provide a preferable microenvironment for multipotent progenitor cells, inducing superior bone formation in vivo.
Diols are versatile chemicals used for multiple manufacturing products. In some previous studies,
Escherichia coli
has been engineered to produce 1,2-propanediol (1,2-PDO) and 1,3-propanediol ...(1,3-PDO) from glucose. However, there are no reports on the direct production of these diols from starch instead of glucose as a substrate. In this study, we directly produced 1,2-PDO and 1,3-PDO from starch using
E. coli
engineered for expressing a heterologous α-amylase, along with the expression of 1,2-PDO and 1,3-PDO synthetic genes. For this, the recombinant plasmids, pVUB3-SBA harboring
amyA
gene for α-amylase production, pSR5 harboring
pct
,
pduP
, and
yahK
genes for 1,2-PDO production, and pSR8 harboring
gpd1-gpp2
,
dhaB123
,
gdrAB
, and
dhaT
genes for 1,3-PDO production, were constructed. Subsequently,
E. coli
BW25113 (
ΔpflA
) and BW25113 strains were transformed with pVUB3-SBA, pSR5, and/or pSR8. Using these transformants, direct production of 1,2-PDO and 1,3-PDO from starch was demonstrated under microaerobic condition. As a result, the maximum production titers of 1,2-PDO and 1,3-PDO from 1% glucose as a sole carbon source were 13 mg/L and 150 mg/L, respectively. The maximum production titers from 1% starch were similar levels (30 mg/L 1,2-PDO and 120 mg/L 1,3-PDO). These data indicate that starch can be an alternative carbon source for the production of 1,2-PDO and 1,3-PDO in engineered
E. coli
. This technology could simplify the upstream process of diol bioproduction.
Abstract
A novel method for the chemo-enzymatic synthesis of chitin oligosaccharide catalyzed by mutants of BcChi-A, an inverting family GH19 chitinase from Bryum coronatum, has been developed using ...4,6-dimethoxy-1,3,5-triazin-2-yl α-chitobioside DMT-α-(GlcNAc)2) as a donor substrate. Based on the glycosynthase derived from BcChi-A, Glu70, which acts as a catalytic base, and Ser102, which fixes a nucleophilic water molecule, were changed to generate several single and double mutants of BcChi-A, which were employed in synthetic reactions. Among the double mutants tested, E70G/S102G, E70G/S102C and E70G/S102A were found to successfully synthesize chitotetraose (GlcNAc)4 from DMT-α-(GlcNAc)2 and (GlcNAc)2; however, the single mutants, E70G, S102G, S102C and S102A, did not. Among the mutants, E70G/S102A showed the highest synthetic activity. This is the first report of a glycosynthase that employs a dimethoxytriazine-type glycoside as a donor substrate.
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