排序方式: 共有15条查询结果,搜索用时 15 毫秒
1.
Joost den Haan Petra M. Visser Anjani E. Ganase Elfi E. Gooren Lucas J. Stal Fleur C. van Duyl Mark J. A. Vermeij Jef Huisman 《Coral reefs (Online)》2014,33(4):1003-1015
Algal turf communities are ubiquitous on coral reefs in the Caribbean and are often dominated by N2-fixing cyanobacteria. However, it is largely unknown (1) how much N2 is actually fixed by turf communities and (2) which factors affect their N2 fixation rates. Therefore, we compared N2 fixation activity by turf communities at different depths and during day and night-time on a degraded versus a less degraded coral reef site on the island of Curaçao. N2 fixation rates measured with the acetylene reduction assay were slightly higher in shallow (5–10-m depth) than in deep turf communities (30-m depth), and N2 fixation rates during the daytime significantly exceeded those during the night. N2 fixation rates by the turf communities did not differ between the degraded and less degraded reef. Both our study and a literature survey of earlier studies indicated that turf communities tend to have lower N2 fixation rates than cyanobacterial mats. However, at least in our study area, turf communities were more abundant than cyanobacterial mats. Our results therefore suggest that turf communities play an important role in the nitrogen cycle of coral reefs. N2 fixation by turfs may contribute to an undesirable positive feedback that promotes the proliferation of algal turf communities while accelerating coral reef degradation. 相似文献
2.
B. Mueller P. Ahnert J. Burkhardt J. Brauer I. Czepezauer E. Quente J. Boltze H. Kirsten 《Genes, Brain & Behavior》2014,13(3):350-356
Dyslexia is characterized by impaired reading and spelling. The disorder has a prevalence of about 5% in Germany, and a strong hereditary component. Several loci are thought to be involved in the development of dyslexia. Scerri et al. identified eight potential dyslexia‐associated single nucleotide polymorphisms (SNPs) in seven genes on chromosome 18 in an English‐speaking population. Here, we present an association analysis that explores the relevance of these SNPs in a German population comprising 388 dyslexia cases and 364 control cases. In case–control analysis, three nominal SNP associations were replicated. The major alleles of NEDD4L‐rs12606138 and NEDD4L‐rs8094327 were risk associated [odds ratio (OR) = 1.35, 95% confidence interval (CI) = 1.0–1.7, P‐value = 0.017 and OR = 1.39, 95% CI = 1.1–1.7, P‐value = 0.007, respectively], and both SNPs were in strong linkage disequilibrium (r2 = 0.95). For MYO5B‐rs555879, the minor allele was risk associated (OR = 1.31, 95% CI = 1.1–1.6, P‐value = 0.011). The combined analysis of SNP sets using set enrichment analysis revealed a study‐wide significant association for three SNPs with susceptibility for dyslexia. In summary, our results substantiate genetic markers in NEDD4L and MYO5B as risk factors for dyslexia and provide first evidence that the relevance of these markers is not restricted to the English language . 相似文献
3.
The Automated Protein Structure Analysis (APSA) method, which describes the protein backbone as a smooth line in three‐dimensional space and characterizes it by curvature κ and torsion τ as a function of arc length s, was applied on 77 proteins to determine all secondary structural units via specific κ(s) and τ(s) patterns. A total of 533 α‐helices and 644 β‐strands were recognized by APSA, whereas DSSP gives 536 and 651 units, respectively. Kinks and distortions were quantified and the boundaries (entry and exit) of secondary structures were classified. Similarity between proteins can be easily quantified using APSA, as was demonstrated for the roll architecture of proteins ubiquitin and spinach ferridoxin. A twenty‐by‐twenty comparison of all α domains showed that the curvature‐torsion patterns generated by APSA provide an accurate and meaningful similarity measurement for secondary, super secondary, and tertiary protein structure. APSA is shown to accurately reflect the conformation of the backbone effectively reducing three‐dimensional structure information to two‐dimensional representations that are easy to interpret and understand. Proteins 2009. © 2008 Wiley‐Liss, Inc. 相似文献
4.
Li W Hwang DJ Cremer D Joo H Kraka E Kim J Ross CR Nguyen VQ Dalton JT Miller DD 《Chirality》2009,21(6):578-583
We report on the synthesis and investigation of two diastereomers (5a and 5b) of a new bicalutamide analog with an asymmetric carbon atom and a chiral sulfoxide group. These bicalutamide analogs are novel androgen receptor antagonists with biological activities that depend significantly on the configuration of their stereogenic centers. We determined the absolute configuration at the SO center by combining X-ray and NMR measurements with quantum chemical calculations. Since 5a and 5b failed to yield satisfactory crystals for X-ray crystal structure determination, analogs 6a and 6b differing in only one remote functional group relative to the chiral sulfoxide were synthesized, which yielded satisfactory crystals. X-ray structure determination of 6a and 6b provided the absolute configuration at the chiral sulfoxide. Since the structural difference between 5 and 6 is remote from the chiral sulfoxide, the structural assignment was extended from the diastereomers of 6 to those of 5 provisionally. These assignments were verified with the help of measured and DFT-calculated proton and carbon NMR chemical shifts. 相似文献
5.
Wenli Zou Robert Kalescky Elfi Kraka Dieter Cremer 《Journal of molecular modeling》2013,19(7):2865-2877
Local vibrational modes can be directly derived from normal vibrational modes using the method of Konkoli and Cremer (Int J Quant Chem 67:29, 1998). This implies the calculation of the harmonic force constant matrix F q (expressed in internal coordinates q) from the corresponding Cartesian force constant matrix f x with the help of the transformation matrix U?=?WB ?(BWB ?)?1 (B: Wilson’s B-matrix). It is proven that the local vibrational modes are independent of the choice of the matrix W. However, the choice W?=?M ?1 (M: mass matrix) has numerical advantages with regard to the choice W?=?I (I: identity matrix), where the latter is frequently used in spectroscopy. The local vibrational modes can be related to the normal vibrational modes in the form of an adiabatic connection scheme (ACS) after rewriting the Wilson equation with the help of the compliance matrix. The ACSs of benzene and naphthalene based on experimental vibrational frequencies are discussed as nontrivial examples. It is demonstrated that the local-mode stretching force constants provide a quantitative measure for the C–H and C–C bond strength. 相似文献
6.
7.
The bond energy (BE) of a polyatomic molecule cannot be measured and, therefore, determination of BEs can only be done within a model using a set of assumptions. The bond strength is reflected by the intrinsic BE (IBE), which is related to the intrinsic atomization energy (IAE) and which represents the energy of dissociation under the provision that the degree of hybridization is maintained for all atoms of the molecule. IBE and BE differ in the case of CC and CH bonds by the promotion, the hybridization, and the charge reorganization energy of carbon. Since the latter terms differ from molecule to molecule, IBE and BE are not necessarily parallel and the use of BEs from thermochemical models can be misleading. The stretching force constant is a dynamical quantity and, therefore, it is related to the bond dissociation energy (BDE). Calculation and interpretation of stretching force constants for local internal coordinate modes are discussed and it is demonstrated that the best relationship between BDEs and stretching force constants is obtained within the model of adiabatic internal modes. The valence stretching force constants are less suitable since they are related to an artificial bond dissociation process with geometrical relaxation effects suppressed, which leads to an intrinsic BDE (IBDE). In the case of AXn molecules, symmetric coordinates can be used to get an appropriate stretching force constant that is related to the BE. However, in general stretching force constants determined for symmetry coordinates do not reflect the strength of a particular bond since the related dissociation processes are strongly influenced by the stability of the products formed. 相似文献
8.
Fuchs T Püellmann K Scharfenstein O Eichner R Stobe E Becker A Pechlivanidou I Kzhyshkowska J Gratchev A Ganser A Neumaier M Beham AW Kaminski WE 《Biochemical and biophysical research communications》2012,419(2):309-315
Recent evidence has revealed the existence of T cell receptor (TCR) αβ-based recombinatorial immune receptors in phagocytes. Here, we performed a systematic survey of the variable β-chain repertoires of the neutrophil TCR-like αβ immunoreceptor (referred to as TCRL(n)αβ) in defined cohorts of young and old individuals. Peripheral blood CD15(+) neutrophils from young adults (age 30 ± 7 years, n=12) expressed an average number of 13 ± 6 distinct TCRL(n) Vβ-chains from the total pool of 25 human Vβ-chains. Neutrophils from aged subjects (age 76 ± 6 years, n=12) also consitutively express the TCRL(n), however, only a small number of Vβ-chains is used (4 ± 2). Consistent with this, the average number of expressed CDR3 Vβ length variants was fourfold higher in young individuals than in aged subjects (33 ± 24 vs. 8 ± 3). Young adults showed broad usage of all TCRL(n) Vβ-chains. In contrast, >70years individuals displayed a striking repertoire polarization towards the TCRL(n) Vβ1 and Vβ5b chains and a high degree of Vβ5b clonotype sharing. Our study reveals broad TCRL(n) repertoire diversity in young adults and demonstrates that the neutrophil variable immune receptor is expressed throughout the entire human life span. The marked decline in TCRL(n) repertoire diversity in old age identifies a novel mechanism of immunosenescence in neutrophils. 相似文献
9.
10.
Jana Burkhardt Mechthild Blume Elisabeth Petit-Teixeira Vitor Hugo Teixeira Anke Steiner Elfi Quente Grit Wolfram Markus Scholz Céline Pierlot Paola Migliorini Stefano Bombardieri Alejandro Balsa René Westhovens Pilar Barrera Timothy R. D. J. Radstake Helena Alves Thomas Bardin Bernard Prum Frank Emmrich Fran?ois Cornelis Peter Ahnert Holger Kirsten 《PloS one》2014,9(8)