HLA-A*02 is the most prevalent and polymorphic major histocompatibility complex (MHC) allele family in humans. Functional differences have been revealed among subtypes, demanding further subtyping of HLA-A*02 in basic and clinical settings. However, the fast growing polymorphisms render traditional primer- or probe-based typing methods impractical and result in increasing ambiguities in direct sequence-based typing. In this study, we combined group-specific amplification and mono-allelic sequencing to design and validate a simple scheme for the complete screening and accurate subtyping of all 540 reported HLA-A*02 alleles. This scheme could be performed in routine labs to facilitate studies with an interest in HLA-A*02.
Poly (lactic acid) (PLA)-Poly (propylene carbonate) (PPC) block copolymer compatibilizers are produced in incompatible 70wt%PLA/PPC blend by initiating transesterification with addition of 1% of tetra butyl titanate (TBT) or by chain extension with addition of 2% of 2,4-toluene diisocyanate (TDI). The above blends can have much better mechanical properties than the blend without TBT and TDI. The elongation at break is dramatically larger (114% with 2% of TDI and 60% with 1% of TBT) than the blend without TDI and TBT, with a slightly lower mechanical strength. A small fraction of the copolymer is likely formed in the PLA/PPC blend with addition of TBT, and a significant amount of the copolymer can be made with addition of TDI. The copolymer produced with TDI has PPC as a major content (~70 wt%) and forms a miscible interphase with its own Tg. The crystallinity of the blend with TDI is significantly lower than the blend without TDI, as the PLA blocks of the copolymer in the interphase is hardly to crystallize. The average molecular weight increases significantly with addition of TDI, likely compensating the lower mechanical strength due to lower crystallinity. Material degradation can occur with addition of TBT, but it is very limited with 1% of TBT. However, compared with the blends without TBT, the PLA crystallinity of the blend with 1%TBT increases sharply during the cooling process, which likely compensates the loss of mechanical strength due to the slightly material degradation. The added TDI does not have any significant impact on PLA lamellar packing, but the addition of TBT can make PLA lamellar packing much less ordered, presumably resulted from much smaller PPC domains formed in the blend due to better compatibility.
Sortase A (SrtA)-mediated ligation, a popular method for protein labeling and semi-synthesis, is limited by its reversibility and dependence on the LPxTG motif, where "x" is any amino acid. Here, we report that SrtA can mediate the efficient and irreversible ligation of a protein/peptide containing a Cterminal thioester with another protein/peptide bearing an N-terminal Gly, with broad tolerance for a wide variety of LPxT-derived sequences. This strategy, the thioester-assisted SrtA-mediated ligation, enabled the expedient preparation of proteins bearing various N-or C-terminal labels, including post-translationally modified proteins such as the Ser139-phosphorylated histone H2AX and Lys9-methylated histone H3, with less dependence on the LPxTG motif. Our study validates the chemical modification of substrates as an effective means of augmenting the synthetic capability of existing enzymatic methods.
Gut microbiota is thought to play a crucial role in nutrient digestion for pigs, especially in processing indigestible polysaccharides in the diets to produce short-chain fatty acids (SCFAs). However, the link between microbiota community structure and phenotypic performances are poorly understood. In the present study, the fecal samples of 105 Jinhua pigs at 105 days of age were clustered into three enterotypes (ETs, ET1, ET2, and ET3) that are subpopulations of distinct bacterial community composition by using 16S rRNA high throughput sequencing. The α-diversity indices (the OTU number and Shannon index) were significantly different among the ETs (p < 0.001). At the genus level, the ET1 group was over-represented by Lactobacillus (17.49%) and Clostridium sensu stricto 1 (11.78%), the ET2 group was over-represented by Clostridium sensu stricto 1 (17.49%) and Bifidobacterium (11.78%), and the ET3 group was over-represented by Bacteroides (18.17%). Significant differences in the fecal contents of butyrate were observed among ETs, with the highest level detected in ET3 and the lowest in ET2 (p < 0.05). Consistently, more copies of the terminal genes for butyrate synthesis, butyrate kinase (Buk) and butyryl coenzyme A (CoA): acetate CoA transferase (But) were detected by qPCR in the fecal samples of the ET3 group as compared to other two groups (p < 0.05). In addition, of the two genes, But was demonstrated to be more relevant to the butyrate content (R = 0.7464) than Buk (R = 0.4905) by correlation analysis. In addition, based on the taxonomic analysis, we found that Faecalibacterium was the most relevant butyrate-producing genera with fecal butyrate contents in Jinhua pigs, followed by Butyricicoccus, Eubacterium, Butyricimonas, Blautia, and Anaerostipes, all of which showed significantly higher richness in ET3 than as compared to ET1 and ET2 (p < 0.05). Collectively, this work presents a first overview of the enterotypes clustering in Jinhua pigs and will help to unravel the functional implications of ETs for the pig’s phenotypic performance and nutrient metabolism.
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