新石器时代人骨遗骸中古代DNA的提取及X—Y染色体同源基因片段的PCR扩增

从中国新石器时代人骨遗骸中提取出古代ＤＮＡ。通过聚合酶链式反应技术扩增得到Ｘ－Ｙ染色体上的单考贝同源基因片段。由于扩增的基因片段长度具有性别多态性,从而为古代人骨和牙齿提供了分子生物学的性别鉴定。     

Protease-sensitive thylakoidal import machinery for the Sec-, ΔpH- and signal recognition particle-dependent protein targeting pathways, but not for CFoII integration

Nuclear-encoded proteins are targeted into and across the thylakoid membrane by a surprising variety of mechanisms. Distinct Sec- and ΔpH-dependent mechanisms have been shown to operate for lumenal proteins, and an integral membrane protein, LHCP, has been shown to insert via a signal recognition particle-dependent route. Integration of a further membrane protein, CF_oII, requires neither soluble factors nor energy sources, prompting speculation of a spontaneous insertion mechanism. Although the requirements for soluble factors and energy sources have been determined in some detail, much less is known of the events taking place at the membrane surface. This report examines whether thylakoid proteins are involved in each of these pathways, by testing the effects of trypsin on the capacity of isolated thylakoids to import proteins. Because all of the pathways rely to some extent on the thylakoidal ΔpH, and a light-induced ΔpH is easily destroyed by proteolysis, the conditions under which reverse action of the ATP synthase in the dark generates a high ΔpH even after proteolysis of thylakoids have been established. This system is used to show that protease-sensitive thylakoidal import machinery is crucial for the ΔpH-, Sec- and signal recognition particle-dependent pathways, but not for integration of CF_oII.     

Nontransferrin-bound Iron in Serum of Patients Receiving Bone Marrow Transplants

Nontransferrin-bound iron (NTBI) and other parameters of iron status were measured in 40 patients undergoing bone marrow transplantation (BMT) prior to conditioning therapy (between day −10 and −7), at the time of BMT (day 0), and 2 weeks later (day +14). Serum iron and transferrin saturation values were normal before conditioning therapy. At day 0 serum iron values were high and median transferrin saturation was 98% (changes in the values of both serum iron and transferrin saturation, p < .0001). Transferrin saturation values were still elevated 2 weeks posttransplant (day +14 vs. baseline values, p = .0001). Starting at low NTBI levels pretransplant (median 0.4 , range 0–4.2 , controls: ≤ 0.4 ), all patients revealed high levels on day 0 (median 4.0 , range 1.9–6.9 , p < .0001) and 2 weeks posttransplant (median 2.7 , range 0–6.2 , p < .0001). These observations indicate that the plasma iron pool in patients undergoing BMT increases to a level at which the normal ability to sequestrate iron becomes exhausted and considerable amounts of NTBI appear in serum. This “free” form of iron can mediate the production of reactive oxygen species and may cause organ toxicity in the early posttransplantation period. © 1997 Elsevier Science Inc.     

Apoplastic pH and Fe3+ Reduction in Intact Sunflower Leaves

It has been hypothesized that under NO₃⁻ nutrition a high apoplastic pH in leaves depresses Fe³⁺ reductase activity and thus the subsequent Fe²⁺ transport across the plasmalemma, inducing Fe chlorosis. The apoplastic pH in young green leaves of sunflower (Helianthus annuus L.) was measured by fluorescence ratio after xylem sap infiltration. It was shown that NO₃⁻ nutrition significantly increased apoplastic pH at distinct interveinal sites (pH ≥ 6.3) and was confined to about 10% of the whole interveinal leaf apoplast. These apoplastic pH increases presumably derive from NO₃⁻/proton cotransport and are supposed to be related to growing cells of a young leaf; they were not found in the case of sole NH₄⁺ or NH₄NO₃ nutrition. Complementary to pH measurements, the formation of Fe²⁺-ferrozine from Fe³⁺-citrate was monitored in the xylem apoplast of intact leaves in the presence of buffers at different xylem apoplastic pH by means of image analysis. This analysis revealed that Fe³⁺ reduction increased with decreasing apoplastic pH, with the highest rates at around pH 5.0. In analogy to the monitoring of Fe³⁺ reduction in the leaf xylem, we suggest that under alkaline nutritional conditions at interveinal microsites of increased apoplastic pH, Fe³⁺ reduction is depressed, inducing leaf chlorosis. The apoplastic pH in the xylem vessels remained low in the still-green veins of leaves with intercostal chlorosis.     

Toric ideals of phylogenetic invariants.

Statistical models of evolution are algebraic varieties in the space of joint probability distributions on the leaf colorations of a phylogenetic tree. The phylogenetic invariants of a model are the polynomials which vanish on the variety. Several widely used models for biological sequences have transition matrices that can be diagonalized by means of the Fourier transform of an Abelian group. Their phylogenetic invariants form a toric ideal in the Fourier coordinates. We determine generators and Gr?bner bases for these toric ideals. For the Jukes-Cantor and Kimura models on a binary tree, our Gr?bner bases consist of certain explicitly constructed polynomials of degree at most four.     

Interactions between the stem-mining weevils Ceutorhynchus napi Gyll. and Ceutorhynchus pallidactylus (Marsh.) (Coleoptera: Curculionidae) in oilseed rape

Abstract 1 The rape stem weevil Ceutorhynchus napi Gyll. and the cabbage stem weevil Ceutorhynchus pallidactylus (Marsh.) share the same habitat and food resource within the stems of oilseed rape, Brassica napus L. var. oleifera. Interactions occurring between these two sympatric species on this host were studied under both field and laboratory conditions. 2 The oviposition preference of C. pallidactylus and the within‐plant distribution of eggs and larvae were examined in field plots of oilseed rape. Female C. pallidactylus tended to lay their eggs in plants already infested by eggs and larvae of C. napi rather than in uninfested plants. The within‐plant distribution of the egg batches of C. pallidactylus did not differ significantly between uninfested plants and those preinfested by C. napi. Ovipositing females of C. napi and C. pallidactylus generally showed a significant preference for plants with larger stem diameter. 3 Laboratory choice tests provided further evidence for the oviposition preference of C. pallidactylus. Females laid significantly more eggs in leaves of plants that had been previously infested by C. napi than in leaves of previously uninfested plants. 4 Larvae of C. pallidactylus showed a significant shift of their feeding niche towards the stem base when feeding in individual plants attacked by both species. This possibly indicates ressource partitioning between C. pallidactylus and C. napi. The within‐plant distribution of C. napi larvae was not affected by the simultaneous attack of C. pallidactylus. 5 The size of the head capsule of full‐grown larvae of C. napi and C. pallidactylus was not significantly correlated with the diameter of the stem of their host plant or with the number of conspecific larvae within individual plants.     

Characterizing seamless ligation cloning extract for synthetic biological applications

Synthetic biology aims at designing and engineering organisms. The engineering process typically requires the establishment of suitable DNA constructs generated through fusion of multiple protein coding and regulatory sequences. Conventional cloning techniques, including those involving restriction enzymes and ligases, are often of limited scope, in particular when many DNA fragments must be joined or scar-free fusions are mandatory. Overlap-based-cloning methods have the potential to overcome such limitations. One such method uses seamless ligation cloning extract (SLiCE) prepared from Escherichia coli cells for straightforward and efficient in vitro fusion of DNA fragments. Here, we systematically characterized extracts prepared from the unmodified E. coli strain DH10B for SLiCE-mediated cloning and determined DNA sequence-associated parameters that affect cloning efficiency. Our data revealed the virtual absence of length restrictions for vector backbone (up to 13.5 kbp) and insert (90 bp to 1.6 kbp). Furthermore, differences in GC content in homology regions are easily tolerated and the deletion of unwanted vector sequences concomitant with targeted fragment insertion is straightforward. Thus, SLiCE represents a highly versatile DNA fusion method suitable for cloning projects in virtually all molecular and synthetic biology projects.