Synchronization of 9L rat brain tumor cells by centrifugal elutriation

Asynchronous 9L cells were separated into relatively homogeneously-sized populations using centrifugal elutriation with both a conventional collection method and a long collection method. A substantial increase in the homogeneity of the volume distributions and in the degree of synchrony of the separated fractions was obtained using the long collection method. Autoradiographic data indicated that fractions containing ≥97% G₁ cells, ≥80% S cells, and 70–75% G₂ cells could be routinely recovered with this procedure. Recovery in these fractions varied from 5 to 8% of the total number of cells elutriated. The colony forming efficiency (CFE) of cells from fractions representing each phase of the cell cycle was a constant 60–70%, which was comparable to the 60–80% usually found for asynchronous 9L cells. The percentage of cells in the G₁, S, and G₂ phases in the elutriated fractions was more accurately determined from the volume distribution than from computer fits of the DNA histogram obtained from flow cytometry. In general, the degree of synchrony was related to the coefficient of variation (CV) of the volume distributions of the elutriated fractions. The CV was about 14% for all elutriated fractions. When the ≥97% G₁ population was allowed to progress to S and G₂, the CVs were about 17 and 20.2%, respectively. Thus, the best nonperturbing method for obtaining synchronous 9L cells in the S or G₂ phases was direct elutriation with the long collection method.     

The structure of monellin and its relation to the sweetness of the protein.

The sweet protein monellin [1-3] has been shown to consist of two non-identical subunits of 50 and 42 amino acid residues, which were separated electrophoretically and chromatographically. Automatic sequential Edman degradation gave the complete sequence of the longer subunit, and a partial sequency of the shorter one. It was found that the sweetness of monellin requires the undissociated molecule. The individual subunits were not sweet, neither did they block the sweet sensation of sucrose or monellin. Blocking of the single SH of monellin abolished its sweetness as did reaction of the single methionyl residue with CNBr. Since the cysteinyl and methionyl residues appear to be adjacent, it is suggested that this part of the molecule is essential for its sweetness.     

Phosphoprotein phosphatase-catalyzed dephosphorylation of the 22,000 dalton phosphoprotein of cardiac sarcoplasmic reticulum.

The present study demonstrated the presence within the myocardium of phosphoprotein phosphatase activity which can account for dephosphorylation of a 22,000 dalton phosphoprotein of cardiac sarcoplasmic reticulum that has been associated with the stimulatory effects of adenosine 3':5'-monophosphate (cyclic AMP)-dependent protein kinase on calcium transport (Tada, M., Kirchberger, M. A., and Katz, A. M. (1975) J. Biol. Chem. 250:2640-2647). Dog cardiac microsomes, consisting mainly of fragmented sarcomplasmic reticulum, were phosphorylated by incubation with cyclic AMP-dependent protein kinase and [gamma-32P]ATP, and subsequently washed with trichloroacetic acid or buffered KCl. Phosphorylated microsomes contained approximately 1 nmole of 32P bound per mg of microsomal protein, 32P labeling occurring almost exclusively at the 22,000 dalton component. Soluble phosphoprotein phosphatases, isolated from the cytosol, catalyzed dephosphorylation of 32P-labeled microsomes. The existence of a phosphoprotein phosphatase that is associated with the microsomes was demonstrated by the ability of the microsomes to dephosphorylate 32P-histone. This membrane-associated phosphatase activity can also account for a rapid decrease in the amount of 32P-labeling of the 22,000 dalton protein. The dephosphorylation of the phosphorylated 22,000 dalton protein by phosphoprotein phosphatase satisfies an important requirement for the phosphorylation of the 22,000 dalton protein to serve a physiological role, namely, its reversibility.     

Electrospun Scaffold of Collagen and Polycaprolactone Containing ZnO Quantum Dots for Skin Wound Regeneration

Nanofibers(NFs)have been widely used in tissue engineering such as wound healing.In this work,the antibacterial ZnO quantum dots(ZnO QDs)have been incorporated into the biocompatible poly(ε-caprolactone)/collagen(PCL/Col)fibrous scaffolds for wound healing.The as-fabricated PCL-Col/ZnO fibrous scaffolds exhibited good swelling,antibacterial activity,and biodegradation behaviors,which were beneficial for the applications as a wound dressing.Moreover,the PCL-Col/ZnO fibrous scaffolds showed excellent cytocompatibility for promoting cell proliferation.The resultant PCL-Col/ZnO fibrous scaffolds containing vascular endothelial growth factor(VEGF)also exhibited promoted wound-healing effect through promoting expression of transforming growth factor-β(TGF-β)and the vascular factor(CD31)in tissues in the early stages of wound healing.This new electrospun fibrous scaffolds with wound-healing promotion and antibacterial property should be convenient for treating wound healing.     

Chromosome-level genome assembly and characterization of Sophora Japonica

Sophora japonica is a medium-size deciduous tree belonging to Leguminosae family and famous for its high ecological, economic and medicinal value. Here, we reveal a draft genome of S. japonica, which was ∼511.49 Mb long (contig N50 size of 17.34 Mb) based on Illumina, Nanopore and Hi-C data. We reliably assembled 110 contigs into 14 chromosomes, representing 91.62% of the total genome, with an improved N50 size of 31.32 Mb based on Hi-C data. Further investigation identified 271.76 Mb (53.13%) of repetitive sequences and 31,000 protein-coding genes, of which 30,721 (99.1%) were functionally annotated. Phylogenetic analysis indicates that S. japonica separated from Arabidopsis thaliana and Glycine max ∼107.53 and 61.24 million years ago, respectively. We detected evidence of species-specific and common-legume whole-genome duplication events in S. japonica. We further found that multiple TF families (e.g. BBX and PAL) have expanded in S. japonica, which might have led to its enhanced tolerance to abiotic stress. In addition, S. japonica harbours more genes involved in the lignin and cellulose biosynthesis pathways than the other two species. Finally, population genomic analyses revealed no obvious differentiation among geographical groups and the effective population size continuously declined since 2 Ma. Our genomic data provide a powerful comparative framework to study the adaptation, evolution and active ingredients biosynthesis in S. japonica. More importantly, our high-quality S. japonica genome is important for elucidating the biosynthesis of its main bioactive components, and improving its production and/or processing.