Thermally Stable and Chemically Recyclable Poly(ketal-ester)s Regulated by Floor Temperature.

Chemical recycling to monomers (CRM) offers a promising closed-loop approach to transition from current linear plastic economy toward a more sustainable circular paradigm. Typically, this approach has focused on modulating the ceiling temperature (Tc) of monomers. Despite considerable advancements, polymers with low Tc often face challenges such as inadequate thermal stability, exemplified by poly(γ-butyrolactone) (PGBL) with a decomposition temperature of ∼200 °C. In contrast, floor temperature (Tf)-regulated polymers, particularly those synthesized via the ring-opening polymerization (ROP) of macrolactones, inherently exhibit enhanced thermodynamic stability as the temperature increases. However, the development of those Tf regulated chemically recyclable polymers remains relatively underexplored. In this context, by judicious design and efficient synthesis of a biobased macrocyclic diester monomer (HOD), we developed a type of Tf -regulated closed-loop chemically recyclable poly(ketal-ester) (PHOD). First, the entropy-driven ROP of HOD generated high-molar mass PHOD with exceptional thermal stability with a Td,5% reaching up to 353 °C. Notably, it maintains a high Td,5% of 345 °C even without removing the polymerization catalyst. This contrasts markedly with PGBL, which spontaneously depolymerizes back to the monomer above its Tc in the presence of catalyst. Second, PHOD displays outstanding closed-loop chemical recyclability at room temperature within just 1 min with tBuOK. Finally, copolymerization of pentadecanolide (PDL) with HOD generated high-performance copolymers (PHOD-co-PPDL) with tunable mechanical properties and chemical recyclability of both components.

Efficient Semi-Synthesis of Atypical Ubiquitin Chains and Ubiquitin-Based Probes Forged by Thioether Isopeptide Bonds.

The development of powerful and general methods to acquire ubiquitin (Ub) chains has prompted the deciphering of Ub-mediated processes. Herein, the cysteine-aminoethylation assisted chemical ubiquitination (CAACU) strategy is extended and improved to enable the efficient semi-synthesis of atypical Ub chain analogues and Ub-based probes. Combining the Cys aminoethylation and the auxiliary-mediated protein ligation, several linkage- and length-defined atypical Ub chains including di-Ubs, K27C-linked tri-Ub, K11/K48C-branched tri-Ub, and even the SUMOlated Ub are successfully prepared from recombinantly expressed starting materials at about a 9-20 mg L-1 expression level. In addition, the utility of this strategy is demonstrated with the synthesis of a novel non-hydrolyzable di-Ub PA probe, which may provide a new useful tool for the mechanistic studies of deubiquitinase (DUB) recognition.

Fully Bio-based Poly(ketal-ester)s by Ring-opening Polymerization of a Bicylcic Lactone from Glycerol and Levulinic Acid.

A fully renewable bio-based bicyclic lactone containing a five-membered cyclic ketal moiety, 7-methyl-3,8,10-trioxabicyclo[5.2.1]decan-4-one (TOD), was synthesized through a two-step acid-catalyzed process from glycerol and levulinic acid. The ring-opening polymerization (ROP) of TOD at 30°C with benzyl alcohol (BnOH) as the initiator and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as the catalyst can afford high molar mass PTOD with a cis-2.4-disubstitued 2-methyl 1,3-dioxolane moiety in its repeating unit. PTOD is an amorphous polymer with a glass transition temperature (Tg ) of 13°C. It can be hydrolyzed into structurally defined small molecules under acidic or basic conditions by the selective cleavage of either the cyclic ketal or the ester linkage respectively. The TBD-catalyzed copolymerization of L-lactide (L-LA) and TOD at -20°C was investigated. It was confirmed that L-LA polymerized quickly with racemization to form PLA, followed by a slow incorporation of TOD into the formed PLA chains via transesterification. By varying the feed ratios of L-LA to TOD, a series of random copolymers (PLA-co-PTOD) with different TOD incorporation ratios and tunable Tg s were obtained. Under acidic conditions, PLA-co-PTOD degrades much faster than PLA via the selective cleavage of the cyclic ketal linkages. This work provides insights for the development of more sustainable and acid-accelerated degradable alternatives to aliphatic polyesters.

[Long-term Follow-up of Patients with Hepatitis-Associated Aplastic Anemia].

OBJECTIVE: To explore the clinical characteristic, therapeutic efficacy and prognosis of patients with hepatitis-associated aplasitc anemia (HAAA). METHODS: the clinical data and labrotatory examination results of 30 cases of HAAA were analyzed retrospectively, the 6-month response ratio and overall survival (OS) were assessed. RESULTS: HAAA most commonly occured in males, with the occurence rate of males and females was 4:1, the median onset age was 16 (4-43) years old, HAAA oriented focus on sever aplastic anemia (SAA)(4 cases,13%) and very sever aplastic anemia (VSAA)(22 cases,73%). Aplastic anemia (AA) could be seen on occurence of hepatitis (accompanied aplastic anemia) (7 cases,23%), or after the onset of hepatits (delayed aplastic anemia) (23 cases,77%), but more often occured in the latter. Statistical analysis showed that when compared with the patients of delayed aplastic anemia, patients accompanied aplastic anemia possesses lower levels of glutamic-pyruvic transaminase(ALT), aspertate aminotransferase (AST) and total bilirubin (TBIL)(P=0.042,0.012,0.001), and possessed a more obvious lymphoid cell disorder when AA occured, with more lower peripheral blood CD19+ B cells proportion (P=0.046) and more obvious imbalance of CD4+/CD8+ ratio, but the difference was no statistical significant (P=0538). Factors affecting the 6-month respose were the severity of AA (P=0.044), the peak level of bilirubin of hepatitis (P=0.006) and the propotion of mature monocyte in bone marrow (P=0.034). The long-term follow-up showed that the 2-year OS of HAAA was 64.3±9.2%, the 6-month curative efficacy significantly affect the prognosis (P<0.001). CONCLUSION: HAAA more often occur in young male, HAAA is mainly SAA and VSAA and mostly non-A-C hepatitis associated aplastic anemia, patients usually have a high incidence of early infection. Patients acompanied with aplastic anemia possess more obvious immunological derangement; the treatment efficacy for HAAA is poor, patients who haven't obtained 6-month response indicate a sinister prognosis, allogeneic hematopoietic stem cell transplantion is a better choice for these patients.

[Application of separating brachial plexus block combined with preoperative analgesia by patient controlled intravenous analgesia in tendon repair].

OBJECTIVE: To investigate whether the separating brachial plexus block combined with preoperative analgesia by patient controlled analgesia (PCA) can be applied in tendon repair and postoperative active or passive functional exercise. METHODS: Two hundred and ten cases with tendon injury were randomly divided into 3 groups and all of the patients were administered Bupivacaine (0.25%), Papaverine (0.0625 mg/ml), and Dexamethasone (0.25 mg/ml) in separating brachial plexus block through axillary approach. Group A was control group, and preoperative analgesia was not applied. Preoperative analgesia was applied in group B and C. Tramadol and Ondansetron were administered in group B, Midazolam was administered besides Tramadol and Ondansetron in group C. The injection volume in the PCIA pump was increased to 100 ml by mixing physiologic saline. The pump was started after separating brachial plexus block in velocity of 2 ml/h, and its maintenance time was 48 h. The effect of separating brachial plexus block at 1, 2, 3, 6 and 12 h after finishing brachial plexus block was compared. The VAS, Ramesay assessment scoring were recorded at 0, 12, 24 and 48 h after starting pump. RESULTS: In each group, the effect of motor block became greater in the ascending order from 1, 2 to 3 h after finishing brachial plexus block, and less in the descending order from 3, 6 to 12 h after finishing brachial plexus block. Only at 6 and 12 h after finishing brachial plexus block, the effect of motor block of group B and group C was significantly less than that of group A (P < 0.05, < 0.01), the effect of motor block of group C was less than that of group B (P > 0.05). The effect of sensory block in the patients of all 3 groups was satisfactory. The VAS, Ramesay assessment scoring, effect of analgesia and sedation at 24 and 48 h after starting pump became greater in the ascending order from group A to group C, in which group B and group C were significantly greater than group A (P < 0.01). CONCLUSIONS: The separating brachial plexus block combined with preoperative analgesia by 2 kinds of PCIA dispensation can be both applied in tendon repair, but the separating effect of brachial plexus block of group B was superior to the group C.