The standard genetic code enhances adaptive evolution of proteins

The standard genetic code, by which most organisms translate genetic material into protein metabolism, is non-randomly organized. The Error Minimization hypothesis interprets this non-randomness as an adaptation, proposing that natural selection produced a pattern of codon assignments that buffers genomes against the impact of mutations. Indeed, on the average any given point mutation has a lesser effect on the chemical properties of the utilized amino acid than expected by chance. Might it also, however, be the case that the non-random nature of the code effects the rate of adaptive evolution? To investigate this, here we develop population genetic simulations to test the rate of adaptive gene evolution under different genetic codes. We identify two independent properties of a genetic code that profoundly influence the speed of adaptive evolution. Noting that the standard genetic code exhibits both, we offer a new insight into the effects of the "error minimizing" code: such a code enhances the efficacy of adaptive sequence evolution.     

Proteome analysis of human lung squamous carcinoma

Few lung cancer-specific molecular markers have been established in regard of "early-stage" diagnosis and prognosis. In this study the proteome analysis of human lung squamous carcinoma (hLSC) was carried out using two strategies to explore the carcinogenic mechanisms and identify its molecular markers more directly and comprehensively. Comparative proteome analysis on 20 hLSC tissues and paired normal bronchial epithelial tissues revealed 76 differential proteins, among which 68 proteins were identified by PMF. The identified proteins fell into three categories: oncoproteins, cell cycle regulators and signaling molecules. To validate the identified differential proteins, the expressions levels of three differential proteins mdm2, c-jun and EGFR were determined by immunohistochemical staining and immunoblots. The results verified proteome analysis results. Serological proteome analysis (SERPA) of ten hLSC tissues was performed to identify the tumor-associated antigens. The results revealed 36 +/- 8 differential proteins reactive with patients' autologous sera, of which 14 proteins were identified. Six of the 14 proteins, alpha enolase, pre-B cell-enhancing factor precursor, triosephosphate isomerase, phosphoglycerate mutase 1, fructose-bisphosphate aldolase A, and guanine nucleotide-binding protein beta subunit-like protein, were also up-regulated in hLSCs in the comparative proteomic study, which suggests potential application of these 6 hLSC-associated antigens in diagnosis and therapy of hLSC.     

Regulation of avilamycin biosynthesis in Streptomyces viridochromogenes: effects of glucose, ammonium ion, and inorganic phosphate

Effects of glucose, ammonium ions and phosphate on avilamycin biosynthesis in Streptomyces viridochromogenes AS4.126 were investigated. Twenty grams per liter of glucose, 10 mmol/L ammonium ions, and 10 mmol/L phosphate in the basal medium stimulated avilamycin biosynthesis. When the concentrations of glucose, ammonium ions, and phosphate in the basal medium exceeded 20 g/L, 10 mmol/L, and 10 mmol/L, respectively, avilamycin biosynthesis greatly decreased. When 20 g/L glucose was added at 32 h, avilamycin yield decreased by 70.2%. Avilamycin biosynthesis hardly continued when 2-deoxy-glucose was added into the basal medium at 32 h. There was little influence on avilamycin biosynthesis with the addition of the 3-methyl-glucose (20 g/L) at 32 h. In the presence of excess (NH₄)₂SO₄ (20 mmol/L), the activities of valine dehydrogenase and glucose-6-phosphate dehydrogenase were depressed 47.7 and 58.3%, respectively, of that of the control at 48 h. The activity of succinate dehydrogenase increased 49.5% compared to the control at 48 h. The intracellular adenosine triphosphate level and 6-phosphate glucose content of S. viridochromogenes were 128 and 129%, respectively, of that of the control at 48 h, with the addition of the 40 mmol/L of KH₂PO₄. As a result, high concentrations of glucose, ammonium ions, and inorganic phosphate all led to the absence of the precursors for avilamycin biosynthesis and affected antibiotic synthesis.     

Effects of hydrostatic pressure on microtubule organization and cell cycle in gynogenetically activated eggs of olive flounder (Paralichthys olivaceus)

Indirect immunofluorescence staining was used to detect cytological changes of isolated blastodisks during mitosis of flounder haploid eggs treated with hydrostatic pressure. Changes in microtubule structure and expected cleavage suppression were observed from blastodisk formation to the third cell cycle, with obvious differences between treated and control eggs. In most eggs, microtubules were disassembled and the nucleation capacity of the centrosome was temporarily inhibited after pressure treatment. Within 15-20 min after treatment, the nucleation capacity of the centrosome began to gradually recover, with slow regeneration of microtubules; approximately 25 min after treatment, the nucleation capacity of the centrosome recovered completely, regenerated distinct bipolar spindles, and the first mitosis ensued. During the second cell cycle, approximately 61% of the embryos were at the two-cell stage, with a monopolar spindle in each blastomere; that treatment was effective was based on second cleavage blockage. Approximately 15% of the eggs still remained at the one-cell stage and had a monopolar spindle (treatment was effective, according to the general model of first cleavage blockage). However, treatment was ineffective in approximately 15% of the embryos (bipolar spindle in each blastomeres) and in another 8% (bipolar spindle in one of the two blastomeres and a monopolar spindle in the other; both mechanisms operating in different parts of the embryo). This is the first report elucidating mitotic gynogenetic diploid induction by hydrostatic pressure in marine fishes and provides a cytological basis for developing an efficient method of inducing mitotic gynogenesis in olive flounder.     

Synthesis and evaluation of isosteres of N-methyl indolo[3,2-b]-quinoline (cryptolepine) as new antiinfective agents

Isosteres of cryptolepine (1) were synthesized and evaluated for their antiinfective activities. Overall, the sulfur isostere, 5-methyl benzothieno[3,2-b]quinolinium salt (5b), was equipotent to 1 and has shown no cytotoxicity at 23.8 microg/mL. Compound 5b was also found to have a broad spectrum of activity. Both the carbon and oxygen isosteres were less potent than cryptolepine. A limited library of 2-substituted analogs of 5b has been synthesized and evaluated in antifungal screens but did not show increase in potency compared to the unsubstituted 5b. Similarly, evaluation of tricyclic benzothieno[3,2-b]pyridines while showing promise in individual screens did not produce an overall increase in potency. Overall, the evaluation of the activities of 5b compared with standard antifungal/anti-protozoal agents suggests that the benzothienoquinoline scaffold could serve as a lead for optimization.     

A method of isolation of apical membranous sheets from frog urinary bladder epithelium by stripping with gelatin

We have developed a technique for recovering apical membranous sheets from amphibian urinary bladders by gelatin stripping. The tissue is mounted on a lucite support and the apical surface is first stuck onto a gelatin-coated glass slide at 30 degrees C. This sandwich is then chilled on ice and the bladder is pulled away from the slide. Preliminary results indicate that this simple technique could be used to remove membranous apical sheets of various sizes, almost devoid of cytoplasmic contamination and without significant damage to the underlying cell structures. The method could also be adapted to prepare perforated cells and to study the cohesive forces between the different layers of the tissue.     

单面针的生物碱研究

自芸香科(Rutaceae)花椒属植物单面针(Zanthoxylum nitidum var. fastuosum How ex Huang)的根皮中分得五种已知生物碱:乙氧基白屈菜红碱(ethoxychelerythrine)(Ⅰ);氯化光花椒碱(nitidine chloride)(Ⅱ);去甲基白屈菜红碱(des-N-methychelerythrine)(Ⅲ);α—别隐品碱(α-allocryptopine)(Ⅳ);鹅掌揪宁(liriodenine)(Ⅴ).     

Functional RelBE-Family Toxin-Antitoxin Pairs Affect Biofilm Maturation and Intestine Colonization in Vibrio cholerae

Toxin–antitoxin (TA) systems are small genetic elements that typically encode a stable toxin and its labile antitoxin. These cognate pairs are abundant in prokaryotes and have been shown to regulate various cellular functions. Vibrio cholerae, a human pathogen that is the causative agent of cholera, harbors at least thirteen TA loci. While functional HigBA, ParDE have been shown to stabilize plasmids and Phd/Doc to mediate cell death in V. cholerae, the function of seven RelBE-family TA systems is not understood. In this study we investigated the function of the RelBE TA systems in V. cholerae physiology and found that six of the seven relBE loci encoded functional toxins in E. coli. Deletion analyses of each relBE locus indicate that RelBE systems are involved in biofilm formation and reactive oxygen species (ROS) resistance. Interestingly, all seven relBE loci are induced under the standard virulence induction conditions and two of the relBE mutants displayed a colonization defect, which was not due to an effect on virulence gene expression. Although further studies are needed to characterize the mechanism of action, our study reveals that RelBE systems are important for V. cholerae physiology.