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101.
102.
Kamenarska Z Yalçin FN Ersöz T Caliş I Stefanov K Popov S 《Zeitschrift für Naturforschung. C, Journal of biosciences》2002,57(7-8):584-590
The chemical composition of the brown alga Cystoseira crinita Bory from the Eastern Mediterranean was investigated. Fourteen sterols have been identified, five of them for the first time in algae. The structure of one new sterol was established. The origin of seven sterols with short side chains was discussed. In the volatile fraction 19 compounds and in the polar fraction 15 compounds were identified. The main lipid classes were isolated and their fatty acid composition was established. 相似文献
103.
Sharmila?Anishetty Gautam?Pennathur Ramesh?AnishettyEmail author 《BMC structural biology》2002,2(1):9
Background
An efficient building block for protein structure prediction can be tripeptides. 8000 different tripeptides from a dataset of 1220 high resolution (≤ 2.0°A) structures from the Protein Data Bank (PDB) have been looked at, to determine which are structurally rigid and non-rigid. This data has been statistically analyzed, discussed and summarized. The entire data can be utilized for the building of protein structures. 相似文献104.
Wood WB;NRC Committee on Programs for Advanced Study of Mathematics Science in American High Schools 《Cell biology education》2002,1(4):123-127
A recently released National Research Council (NRC) report, Learning and Understanding: Improving Advanced Study of Mathematics and Science in U.S. High Schools, evaluated and recommended changes in the Advanced Placement (AP), International Baccalaureate (IB), and other advanced secondary school science programs. As part of this study, discipline-specific panels were formed to evaluate advanced programs in biology, chemistry, physics, and mathematics. Among the conclusions of the Content Panel for Biology were that AP courses in particular suffer from inadequate quality control as well as excessive pressure to fulfill their advanced placement function, which encourages teachers to attempt coverage of all areas of biology and emphasize memorization of facts rather than in-depth understanding. In this essay, the Panel's principal findings are discussed, with an emphasis on its recommendation that colleges and universities should be strongly discouraged from using performance on either the AP examination or the IB examination as the sole basis for automatic placement out of required introductory courses for biology majors and distribution requirements for nonmajors. 相似文献
105.
Dhingra G Kumari R Bala S Majumdar S Malhotra S Sharma P Lal S Cullum J Lal R 《Journal of industrial microbiology & biotechnology》2003,30(4):195-204
The genus Amycolatopsis is of industrial importance, as its species are known to produce commercial antibiotics. It belongs to the family Pseudonocardiaceae and has an eventful taxonomic history. Initially strains were identified as Streptomyces, then later as Nocardia. However, based on biochemical, morphological and molecular features, the genus Amycolatopsis, containing seventeen species, was created. The development of molecular genetic techniques for this group has been slow.
The scarcity of molecular genetic tools including stable plasmids, antibiotic resistance markers, transposons, reporter genes,
cloning vectors, and high efficiency transformation protocols has made progress slow, but efforts in the past decade have
led to the development of cloning vectors and transformation methods for these organisms. Some of the cloning vectors have
broad host range (pRL series) whereas others have limited host range (pMEA300 and pMEA100). The cloning vector pMEA300 has
been completely sequenced, while only the minimal replicon (pA-rep) has been sequenced from pRL plasmids. Direct transformation of mycelia and electroporation are the most widely applicable
methods for transforming species of Amycolatopsis. Conjugational transfer from Escherichia coli has been reported only in the species A. japonicum, and gene disruption and replacements using homologous recombination are now possible in some strains.
Electronic Publication 相似文献
106.
107.
The influence of Putrescine (Put) on the growth and elicitation of anthocyanin in callus cultures of Daucus carota var. Nantes scarlet was investigated through the use of α-DL-difluoromethylarginine (DFMA), the polyamine (PA) biosynthetic
inhibitor. It was observed that the addition of Put (0.05 mM) resulted in enhancement of growth and anthocyanin content. The
anthocyanin content was found to be enhanced by 1.68 fold on the 21st day as compared to the untreated controls. The PA inhibitor was found to result in lowering of the growth and the anthocyanin
accumulation, which could be partially restored by the addition of Put in combination with this inhibitor. The levels of Ca2+ ATPase were also found to be elevated in treatment with Put suggesting the involvement of calcium in the elicitation of anthocyanin.
The endogenous titres of PAs and the ethylene production under these treatments were also studied. The treatment with DFMA
resulted in lower levels of endogenous PAs and higher levels of ethylene. Lowering of ethylene by putrescine treatment shows
that PA treatment also inhibited ethylene formation, which would also imply that endogenous ethylene does not influence anthocyanin
production in carrot callus cultures. 相似文献
108.
Barnali?Baisakhi Jita?Patra Rabindra?K.?Panigrahy Brahma?B.?PandaEmail author 《Acta Physiologiae Plantarum》2003,25(4):357-363
Tolerant and non-tolerant clones of Chloris barbata Sw. obtained, respectively, from an erstwhile mercury contaminated solid waste dump site near a chloralkali plant and a non-contaminated
(control) site were subjected to cadmium-stress by growing the rooted cuttings in water containing CdSO4, 13 and 130 μM. Differences between the two clones in their response to cadmium-stress were noted in root growth, and also
with respect to certain biochemical parameters. Whereas catalase activity decreased and non protein-thiol levels increased
in the non-tolerant clone, the level of protein-thiol alone increased significantly in the tolerant clone in response to cadmium-stress.
No remarkable differences between the clones, however, were noted with respect to total soluble protein, peroxidase activity
and lipid peroxidation. Remarkably the two clones responded differently to buthionine sulfoximine, an inhibitor of glutathione
and/or phytochelatin synthesis, which inhibited root growth significantly in non-tolerant clone but not in the tolerant clone.
Buthionine sulfoximine, nonetheless, could potentate cadmium toxicity in either of the clones, but more effectively in the
tolerant clone. The high sensitivity of tolerant-clone to the combined treatment of BSO and Cd in the present study could,
therefore, be attributed to the cumulative oxidative stress generated synergistically by BSO and Cd. 相似文献
109.
Corticosteroid binding globulin (CBG) and thyroxin binding globulin (TBG) both belong to the same SERPIN superfamily of serine-proteinase inhibitors but in the course of evolution CBG has adapted to its new role as a transport agent of insoluble hormones. CBG binds corticosteroids in plasma, delivering them to sites of inflammation to modify the inflammatory response. CBG is an effective drug carrier for genetic manipulation, and hence there is immense biological interest in the location of the hormone binding site. The crystal structure of human CBG (hCBG) has not been determined, but sequence alignment with other SERPINs suggests that it conforms as a whole to the tertiary structure shared by the superfamily. Human CBG shares 52.15% and 55.50% sequence similarity with alpha1-antitrypsin and alpha1-antichymotrypsin, respectively. Multiple sequence alignment among the three sequences shows 73 conserved regions. The molecular structures of alpha1-antitrypsin and alpha1-antichymotrypsin, the archetype of the SERPIN superfamily, obtained by X-ray diffraction methods are used to develop a homology model of hCBG. Energy minimization was applied to the model to refine the structure further. The homology model of hCBG contains 371 residues (His13 to Val383 ). The secondary structure comprises 11 helices, 15 turns and 11 sheets. The putative corticosteroid binding region is found to exist in a pocket between beta-sheets S4, S10, S11 and alpha helix H10. Both cortisol and aldosterone are docked to the elongated hydrophobic ligand binding pocket with the polar residues at the two extremities. A difference accessible surface area (DASA) study revealed that cortisol binds with the native hCBG more tightly than aldosterone. Cleavage at the Val379-Met380 peptide bond causes a deformation of hCBG (also revealed through a DASA study). This deformation could probably trigger the release of the bound hormone. Figure Stereoscopic view of the ribbon diagram of hCBG complexed with cortisol. The bound cortisol is shown in space filling model in blue. Helices and sheets are shown in red and magenta respectively. Turns are shown in yellow. 相似文献
110.
Leela?SahijramEmail author Jaya?R.?Soneji K.?T.?Bollamma 《In vitro cellular & developmental biology. Plant》2003,39(6):551-556
Summary In a micropropagation program, where it is of paramount importance to produce true-to-type planting material, somaclonal variation
of any kind is undesirable. Variation among plants regenerated from tissue culture is termed ‘somaclonal variation’. In banana,
somaclonal variants of different type have been reported with regard to plant morphology. This article discusses various factors
due to which somaclonal variations may arise. Somaclonal variation may be detected by visual screening or by using molecular
markers such as randomly amplified polymorphic DNA (RAPD), amplified fragment length polymorphism (AFLP), and by cytological
studies. Although somaclonal variation is undesirable in the context of micropropagation, it can be used to advantage for
genetic improvement of banana, as has been described. 相似文献