6′/3′-Sialylated N-acetyllactosamine (6′/3′-SLN) is important for discrimination of the source (human or avian) of influenza virus strains. Biotinylated oligosaccharides have been widely used for analysis and quick detection. The development of efficient strategies to synthesize biotin-tagged 6′/3′-SLN have become necessary. Effective mixing is essential for enzymatic solid-phase oligosaccharide synthesis (SPOS). In the current study, newly developed technology ultrahigh-frequency-acoustofluidics (UHFA), which can provide a powerful source for efficient microfluidic mixing, solid-phase oligosaccharide synthesis and one-pot multienzyme (OPME) system, were used to develop a new strategy for oligosaccharide synthesis. Firstly, biotinylated N-acetylglucosamine was designed and chemically synthesized through traditional approaches. Secondly, biotinylated 6′- and 3′-sialyl-N-acetylglucosamines were prepared in solution through two sequential OPME modules in with a yield of ~95%. Thirdly, 6′-SLN was also prepared through UHFA-based enzymatic solid-phase synthesis on magnetic beads with a yield of 64.4%. The current strategy would be potentially used for synthesis of functional oligosaccharides.

Sialyltransferases are key enzymes for the production of sialosides. The versatility of Pasteurella multocida α2,3-sialyltransferase 1 (PmST1) causes difficulties in the efficient synthesis of α2,3-linked sialylatetd compounds, especial its α2,3-sialidase activity. In the current study, the α2,3-sialidase activity of PmST1 was further reduced by rational design-based protein engineering. Three double mutants PMG1 (M144D/R313Y), PMG2 (M144D/R313H) and PMG3 (M144D/R313N) were designed and constructed using M144D as the template and kinetically investigated. In comparison with M144D, the α2,3-sialyltransferase activity of PMG2 was enhanced by 1.4-fold, while its α2,3-sialidase activity was reduced by 4-fold. Two PMG2-based triple mutants PMG2-1 (M144D/R313H/T265S) and PMG2-2 (M144D/R313H/E271F) were then designed, generated and characterized. Compared with PMG2, triple mutants showed slightly improved α2,3-sialyltransferase activity, but their α2,3-sialidase activities were increased by 2.1–2.9 fold. In summary, PMG2 was used for preparative-scale production of 3′-SL (3′-sialyllactose) with a yield of >95%. These new PmST1 mutants could be potentially utilized for efficient synthesis of α2,3-linked sialosides. This work provides a guide to designing and constructing efficient sialyltransferases.

Background Patients with left ventricular thrombus (LVT) resolution can have LVT recurrence and risk for thromboembolism. However, these outcomes after LVT resolution are not well known. We aimed to assess the prevalence, risk factors, and clinical outcomes for LVT recurrence in patients with LVT resolution to inform follow‐up and treatment. Methods and Results Patients with LVT resolution were identified retrospectively from a large echocardiography database between January 2009 and May 2022. Participants had echocardiograms at 3 time points, including baseline at LVT diagnosis, at LVT resolution, and a follow‐up for identification of LVT recurrence. The cumulative LVT recurrence rate was estimated by the Kaplan–Meier method, and predictors of LVT recurrence were evaluated using Cox regression analysis. Among 115 patients with LVT resolution, 28 (24.3%) had LVT recurrence at a median follow‐up of 1.2 (0.5–2.8) years. LV aneurysm (hazard ratio [HR], 2.59 [95% CI, 1.20–5.58], P =0.015) and anticoagulant use (HR, 0.12 [95% CI, 0.04–0.41], P =0.001) were predictors of LVT recurrence on multivariable analysis. Patients with an LV aneurysm who did not receive any anticoagulation demonstrated an LVT recurrence rate of 69.5%, whereas those without an LV aneurysm who received anticoagulation had a recurrence rate of 0%. Patients with LVT recurrence had a higher incidence of an embolic event (10.7% versus 1.1%, P =0.016). Conclusions LVT recurrence after LVT resolution is common, especially in those with an LV aneurysm, and is associated with a higher embolic risk. Continued anticoagulation is protective against LVT recurrence, although bleeding risk needs to be considered. These findings can inform follow‐up and treatment of patients with documented LVT resolution.