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201.
以四氧化三铁为代表的医用磁性纳米材料具有独特的磁学性能、表面易功能化、良好的生物学相容性等特点,在纳米医学相关领域展现出巨大的应用前景,特别是近年来它作为可介导外场的智能材料,在材料设计和生物医学应用方面均取得了突破性的进展.鉴于此,本文围绕磁性氧化铁纳米材料的生物医学应用,着重介绍近年来其在磁共振影像探针、磁热和磁力效应的生物医学应用、诊疗一体化以及纳米酶催化等领域的研究进展,并对磁性纳米材料在生物医学领域未来的发展方向进行了展望. 相似文献
202.
Yamaji N Sugase K Nakajima T Miki T Wakamori M Mori Y Iwashita T 《FEBS letters》2007,581(20):3789-3794
Agelenin, isolated from the Agelenidae spider Agelena opulenta, is a peptide composed of 35 amino acids. We determined the three-dimensional structure of agelenin using two-dimensional NMR spectroscopy. The structure is composed of a short antiparallel beta-sheet and four beta-turns, which are stabilized by three disulfide bonds. Agelenin has characteristic residues, Phe9, Ser28 and Arg33, which are arranged similarly to the pharmacophore of the insect channel inhibitor, omega-atracotoxin-Hv1a. These observations suggest that agelenin and omega-atracotoxin-Hv1a bind to insect calcium channels in a similar manner. We also suggest that another mode of action may operate in the channel inhibition by omega-agatoxin-IVA and omega-atracotoxin-Hv2a. 相似文献
203.
Identification of sequence motifs that favor cis peptide bonds in proteins is important for understanding and designing proteins containing turns mediated by cis peptide conformations. From (1)H NMR solution studies on short peptides, we show that the Pro-Pro peptide bond in Pro-Pro-Phe almost equally populates the cis and trans isomers, with the cis isomer stabilized by a CHc...pi interaction involving the terminal Pro and Phe. We also show that Phe is over-represented at sequence positions immediately following cis Pro-Pro motifs in known protein structures. Our results demonstrate that the Pro-Pro cis conformer in Pro-Pro-Phe sequence motifs is as important as the trans conformer, both in short peptides as well as in natively folded proteins. 相似文献
204.
The albumin-binding domain, or GA module, of the peptostreptococcal albumin-binding protein expressed in pathogenic strains of Finegoldia magna is believed to be responsible for the virulence and increased growth rate of these strains. Here we present the 1.4A crystal structure of this domain, and compare it with the crystal structure of the GA-albumin complex. An analysis of protein-protein interactions in the two crystals, and the presence of multimeric GA species in solution, indicate the GA module is "sticky", and is capable of forming contacts with a range of protein surfaces. This might lead to interactions with different host proteins. 相似文献
205.
DAVID E. RICHARDSON JEFFREY D. VANWYE AMY M. EXUM ROBERT K. COWEN DOUGLAS L. CRAWFORD 《Molecular ecology resources》2007,7(2):199-207
Ichthyoplankton collections provide a valuable means to study fish life histories. However, these collections are greatly underutilized, as larval fishes are frequently not identified to species due to their small size and limited morphological development. Currently, there is an effort underway to make species identification more readily available across a broad range of taxa through the sequencing of a standard gene. This effort requires the development of new methodologies to both rapidly produce and analyse large numbers of sequences. The methodology presented in this paper addresses these issues with a focus on the larvae of large pelagic fish species. All steps of the methodology are targeted towards high‐throughput identification using small amounts of tissue. To accomplish this, DNA isolation was automated on a liquid‐handling robot using magnetic bead technologies. Polymerase chain reaction and a unidirectional sequencing reaction followed standard protocols with all template cleanup and transferring also automated. Manual pipetting was thus reduced to a minimum. A character‐based bioinformatics program was developed to handle the large sequence output. This program incorporates base‐call quality scores in two types of sample to voucher sequence comparisons and provides suggested identifications and sequence information in an easily interpreted spreadsheet format. This technique when applied to tuna and billfish larvae collected in the Straits of Florida had an 89% success rate. A single species (Thunnus atlanticus) was found to dominate the catch of tuna larvae, while billfish larvae were more evenly divided between two species (Makaira nigricans and Istiophorus platypterus). 相似文献
206.
Alexander Pazur Christine Schimek Paul Galland 《Central European Journal of Biology》2007,2(4):597-659
The ability to respond to magnetic fields is ubiquitous among the five kingdoms of organisms. Apart from the mechanisms that
are at work in bacterial magnetotaxis, none of the innumerable magnetobiological effects are as yet completely understood
in terms of their underlying physical principles. Physical theories on magnetoreception, which draw on classical electrodynamics
as well as on quantum electrodynamics, have greatly advanced during the past twenty years, and provide a basis for biological
experimentation. This review places major emphasis on theories, and magnetobiological effects that occur in response to weak
and moderate magnetic fields, and that are not related to magnetotaxis and magnetosomes. While knowledge relating to bacterial
magnetotaxis has advanced considerably during the past 27 years, the biology of other magnetic effects has remained largely
on a phenomenological level, a fact that is partly due to a lack of model organisms and model responses; and in great part
also to the circumstance that the biological community at large takes little notice of the field, and in particular of the
available physical theories. We review the known magnetobiological effects for bacteria, protists and fungi, and try to show
how the variegated empirical material could be approached in the framework of the available physical models. 相似文献
207.
Proposed minimum reporting standards for chemical analysis 总被引:4,自引:0,他引:4
Lloyd W. Sumner Alexander Amberg Dave Barrett Michael H. Beale Richard Beger Clare A. Daykin Teresa W.-M. Fan Oliver Fiehn Royston Goodacre Julian L. Griffin Thomas Hankemeier Nigel Hardy James Harnly Richard Higashi Joachim Kopka Andrew N. Lane John C. Lindon Philip Marriott Andrew W. Nicholls Michael D. Reily John J. Thaden Mark R. Viant 《Metabolomics : Official journal of the Metabolomic Society》2007,3(3):211-221
There is a general consensus that supports the need for standardized reporting of metadata or information describing large-scale
metabolomics and other functional genomics data sets. Reporting of standard metadata provides a biological and empirical context
for the data, facilitates experimental replication, and enables the re-interrogation and comparison of data by others. Accordingly,
the Metabolomics Standards Initiative is building a general consensus concerning the minimum reporting standards for metabolomics
experiments of which the Chemical Analysis Working Group (CAWG) is a member of this community effort. This article proposes
the minimum reporting standards related to the chemical analysis aspects of metabolomics experiments including: sample preparation,
experimental analysis, quality control, metabolite identification, and data pre-processing. These minimum standards currently
focus mostly upon mass spectrometry and nuclear magnetic resonance spectroscopy due to the popularity of these techniques
in metabolomics. However, additional input concerning other techniques is welcomed and can be provided via the CAWG on-line
discussion forum at or . Further, community input related to this document can also be provided via this electronic forum.
The contents of this paper do not necessarily reflect any position of the Government or the opinion of the Food and Drug Administration
Sponsor: Metabolomics Society http://www.metabolomicssociety.org/
Reference: http://msi-workgroups.sourceforge.net/bio-metadata/reporting/pbc/
http://msi-workgroups.sourceforge.net/chemical-analysis/
Version: Revision: 5.1
Date: 09 January, 2007 相似文献
208.
Dyguda-Kazimierowicz E Sokalski WA Leszczyński J 《Journal of molecular modeling》2007,13(6-7):839-849
The subject of this study was an analysis of the role of active site residues in the phosphoryl transfer reaction catalyzed
by 4-methyl-5-β-hydroxyethylthiazole kinase (ThiK). The ThiK-catalyzed reaction is of special interest due to the lack of
a highly conserved aspartate residue serving as a catalytic base. ONIOM(B3LYP:PM3) models of stationary points along the reaction
pathway consisted of reactants, two magnesium ions and several highly conserved ThiK active site residues. The results indicate
that an SN2-like mechanism of ThiK, with γ-phosphate acting as an alcohol-activating base is reasonable. Geometries of substrates, transition
state and products were utilized in the non-empirical analysis of the physical nature of catalytic interactions taking place
in the ThiK active site. The role of particular residues was investigated in terms of their ability to preferentially stabilize
the transition state relative to substrates (differential transition state stabilization, DTSS) or products (differential
product stabilization, DPS). It seems that Mg2, Glu126 and Cys198 play a major catalytic role, whereas Mg1 and the same Cys198
are responsible for product release. It is remarkable that no dominant role of an electrostatic term in the interactions involved
in catalytic activity is observed for product release. Determination of catalytic fields expressing differential electrostatic
potential of the transition state with respect to substrates revealed the optimal electrostatic features of an ideal catalyst
for the studied reaction. The predicted catalytic environment is in agreement with experimental data showing increased catalytic
activity of ThiK upon mutation of Cys198 to aspartate.
Figure Catalytic fields for ThiK-catalyzed reaction juxtaposed with the positions of active site residues of a model system. Magnesium
ions are considered part of the transition state/reactants. The surface of constant electronic density is colored according
to differential electrostatic potential of transition state with respect to reactants. The sign of the differential potential
reflects the electrostatic properties of a complementary molecular environment. Red (green) color denotes regions where a negative (positive) charge would be optimal for catalytic activity 相似文献
209.
核磁共振(NMR)技术由于具有高效快速、不破坏土壤结构且对人体无害等优点,逐渐被应用到土壤学相关领域研究中。然而,土壤中顺磁物质的存在对核磁共振信号特征的影响仍不明确。本研究旨在揭示顺磁物质对不同类型土壤低场核磁共振(LF-NMR)信号特征和土壤含水量测定的影响。结果表明:土壤水的LF-NMR信号量最高可达150左右,土壤矿物、有机质和微生物等固相物质的LF-NMR信号量基本不超过0.3,相对可以忽略。质地和顺磁物质对土壤水的LF-NMR信号量测量有更大影响。LF-NMR仪器存在弛豫时间监测盲区,信号量损失主要是由于顺磁物质加速了水中氢质子的弛豫过程,导致小孔隙中水分反馈的极快的LF-NMR信号不能被监测设备捕获。对于顺磁物质含量较少的壤性潮土(1.2%)和黏壤性黑土(1.3%),LF-NMR信号量损失不大,其与土壤含水量呈线性关系;但对于黏粒含量(45.3%)和顺磁物质含量(4.0%)较高的黏性红壤,测定中会损失一部分LF-NMR信号量,监测到的LF-NMR信号量与土壤含水量不再呈线性关系。此外,外源添加顺磁物质(3.0 g·L-1的MnCl2溶液)也会降低黑土和红壤中可被监测的LF-NMR信号量,黑土和红壤的信号量最大损失率分别为41.0%和46.7%,极大地改变其与土壤含水量之间的定量关系。因此,在利用LF-NMR测量富含顺磁物质(>1.3%)或有外源顺磁物质进入的黏性土壤的含水量时,应先通过校正降低顺磁物质等对LF-NMR信号量的影响。研究结果对利用低场核磁共振技术准确分析土壤水分分布及土壤孔隙结构具有重要意义。 相似文献
210.
Delfine Cheng Marco Morsch Gerald J. Shami Roger S. Chung Filip Braet 《Experimental cell research》2019,374(1):162-171
Although liver transport routes have been extensively studied in rodents, live imaging under in situ and in vivo conditions of large volumes is still proven to be difficult. In this study, we took advantage of the optical transparency of zebrafish and their small size to explore their usefulness for correlative imaging studies and liver transport experimentations. First, we assessed the micro-architecture of the zebrafish liver and compared its fine structure to the rodent and humans’ literature. Next, we investigated the transport routes and cellular distribution of albumin using combined and correlative microscopy approaches. These methods permitted us to track the injected proteins at different time points through the process of liver uptake and clearance of albumin.We demonstrate strong structural and functional resemblance between the zebrafish liver and its rodents and humans’ counterparts. In as short as 5?min post-injection, albumin rapidly accumulated within the LSECs. Furthermore, albumin entered the space of Disse where it initially accumulated then subsequently was taken up by the hepatocytes. We propose the zebrafish as a viable alternative experimental model for hepatic transport studies, allowing swift multimodal imaging and direct quantification on the hepatic distribution of supramolecular complexes of interest. 相似文献