Glycosphingolipids are a diverse family of biologically important glycolipids. In addition to variations on the lipid component, more than 300 glycosphingolipid glycans have been characterized. These glycans are directly involved in various molecular recognition events. Several naturally occurring sialic acid forms have been found in sialic acid-containing glycosphingolipids, namely gangliosides. However, ganglioside glycans containing less common sialic acid forms are currently not available. Herein, highly effective one-pot multienzyme (OPME) systems are used in sequential for high-yield and cost-effective production of glycosphingolipid glycans, including those containing different sialic acid forms such as N-acetylneuraminic acid (Neu5Ac), N-glycolylneuraminic acid (Neu5Gc), 2-keto-3-deoxy-D-glycero-D-galacto-nononic acid (Kdn), and 8-O-methyl-N-acetylneuraminic acid (Neu5Ac8OMe). A library of 64 structurally distinct glycosphingolipid glycans belonging to ganglio-series, lacto-/neolacto-series, and globo-/isoglobo-series glycosphingolipid glycans is constructed. These glycans are essential standards and invaluable probes for bioassays and biomedical studies.

Nature provides numerous examples of self-assembly that can potentially be implemented for materials applications. Considerable attention has been given to one-dimensional cross-β or amyloid structures that can serve as templates for wire growth or strengthen materials such as glue or cement. Here, we demonstrate controlled amyloid self-assembly based on modifications of β-solenoid proteins. They occur naturally in several contexts (e.g., antifreeze proteins, drug resistance proteins) but do not aggregate in vivo due to capping structures or distortions at their ends. Removal of these capping structures and regularization of the ends of the spruce budworm and rye grass antifreeze proteins yield micron length amyloid fibrils with predictable heights, which can be a platform for biomaterial-based self-assembly. The design process, including all-atom molecular dynamics simulations, purification, and self-assembly procedures are described. Fibril formation with the predicted characteristics is supported by evidence from thioflavin-T fluorescence, circular dichroism, dynamic light scattering, and atomic force microscopy. Additionally, we find evidence for lateral assembly of the modified spruce budworm antifreeze fibrils with sufficient incubation time. The kinetics of polymerization are consistent with those for other amyloid formation reactions and are relatively fast due to the preformed nature of the polymerization nucleus.

Fucosylated human milk oligosaccharides (HMOs) have important biological functions. Enzymatic synthesis of such compounds requires robust fucosyltransferases. A C-terminal 66amino acid truncated version of Helicobacter pylori α1-3-fucosyltransferase (Hp3FT) is a good candidate. Hp3FT was biochemically characterized to identify optimal conditions for enzymatic synthesis of fucosides. The acceptor substrate specificity is N-acetyllactosamine (LacNAc) and lactose, with LacNAc as its preferred acceptor. At a low guanosine 5'-diphospho-β-L-fucose (GDP-Fuc) to acceptor ratio, Hp3FT selectively fucosylated LacNAc. Based on these enzymatic characteristics, diverse fucosylated HMOs, including 3-fucosyllactose (3-FL), lacto-Nfucopentaose (LNFP) III, lacto-N-neofucopentaose (LNnFP) V, lacto-N-neodifucohexaose (LNnDFH) II, difuco-and trifuco-para-lacto-N-neohexaose (DF-paraLNnH and TF-para-LNnH), were synthesized enzymatically by varying the ratio of the donor and acceptor as well as controlling the order of multiple glycosyltransferase-catalyzed reactions.

Uridine 5'-diphosphate-N-acetylglucosamine (UDP-GlcNAc) acyltransferase (LpxA) catalyzes a reversible reaction for adding an O-acyl group to the GlcNAc in UDP-GlcNAc in the first step of lipid A biosynthesis. Lipid A constitutes a major component of lipopolysaccharides, also referred to as endotoxins, which form the outer monolayer of the outer membrane of Gram-negative bacteria. Ligand-free and UDP-GlcNAc-bound crystal structures of LpxA from Bacteroides fragilis NCTC 9343, the most common pathogenic bacteria found in abdominal abscesses, have been determined and are presented here. The enzyme crystallizes in a cubic space group, with the crystallographic threefold axis generating the biological functional homotrimer and with each monomer forming a nine-rung left-handed β-helical (LβH) fold in the N-terminus followed by an α-helical motif in the C-terminus. The structure is highly similar to LpxA from other organisms. Yet, despite sharing a similar LβH structure with LpxAs from Escherichia coli and others, previously unseen calcium ions are observed on the threefold axis in B. fragilis LpxA to help stabilize the trimeric assembly.

Đặt vấn đề: Kháng thuốc kháng sinh đang là mối đe dọa nghiêm trọng nhất đối với sức khỏe con người. Một số chủng vi khuẩn đã kháng gần như tất cả các loại kháng sinh. Mục tiêu: Đánh giá thực trạng kháng kháng sinh của các trực khuẩn gram âm gây bệnh phân lập được tại Bệnh viện Hữu nghị Việt Tiệp Hải Phòng năm 2020. Đối tượng và phương pháp: Tất cả các mẫu bệnh phẩm nuôi cấy mọc trực khuẩn gram âm gây bệnh thường gặp tại Bệnh viện Hữu Nghị Việt Tiệp Hải Phòng từ tháng 01 năm 2020 đến hết tháng 12 năm 2020. Nghiên cứu mô tả cắt ngang. Kết quả: có 2.760 chủng trực khuẩn gram âm gây bệnh được phân lập, thực hiện kháng sinh đồ, trong đó 55,96% số chủng E.coli phân lập được sinh ESBL. Tỷ lệ E.coli kháng kháng sinh là: kháng cefotaxime: 63,37%; cefuroxime: 56,97%; ceftazidime: 34,83%, ciprofloxacin: 68,52%; ertapenem: 3,73%; imipenem: 2,72%; meropenem: 2,85%.Tỷ lệ K. pneumoniae kháng kháng sinh là: kháng amoxicillin/clavulanicacid: 51,01%; cefotaxime: 50,0 %; piperacillin/tazobactam: 45,0%; ceftazidime: 45,09%; cefuroxime: 37,24%; cefepime: 33,33%, ciprofloxacin: 57,29%; ertapenem: 31,29%; imipenem: 27,69%, meropenem: 28,13%. Tỷ lệ kháng kháng sinh của P.aeruginosa: kháng ciprofloxacin: 54,08%, gentamicin: 51,74%; tobramycin: 46,92%; meropenem: 46,30%; amikacin: 36,01%; imipenem: 35,76%; ceftazidime: 33,90%, cefepime: 28,57%; piperacillin/tazobactam: 14,38%. Tỷ lệ kháng kháng sinh của A.baumannii như sau: ampicillin/sulbactam: 63,91%; piperacillin/pazobactam: 88,14%; ceftazidime: 85,26%; cefotaxime: 83,08%; cefepime: 83,57%; imipenem: 83,05%; meropenem: 84,36%.   Kết luận: Kết quả kháng sinh đồ cho thấy các chủng trực khuẩn gram âm phân lập được có tỷ lệ kháng cao với các cephalosporin thế hệ 3 và ciprofloxacin. Tình trạng kháng carbapenemes của các chủng K.pneumonia, A.baumannii ở mức rất nghiêm trọng.