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排序方式: 共有988条查询结果,搜索用时 31 毫秒
121.
Colin R. Andrew Jane Han Tanneke den Blaauwen Gertie van Pouderoyen Erik Vijgenboom Gerard W. Canters Thomas M. Loehr J. Sanders-Loehr 《Journal of biological inorganic chemistry》1997,2(1):98-107
In the redox center of azurin, the Cu(II) is strongly coordinated to one thiolate S from Cys 112 and two imidazole Ns from
His 46 and 117. This site yields a complex resonance Raman (RR) spectrum with >20 vibrational modes between 200 and 1500 cm–1. We have investigated the effects of ligand-selective isotope replacements on the RR spectrum of Pseudomonas aeruginosa azurin to determine the relative spectral contribution from each of the copper ligands. Growth on 34S-sulfate labels the cysteine ligand and allows the identification of a cluster of bands with Cu–S(Cys) stretching character
between 370 and 430 cm–1 whose frequencies are consistent with the trigonal or distorted tetrahedral coordination in type 1 sites. In type 2 copper-cysteinate
sites, the lower ν (Cu–S) frequencies between 260 and 320 cm–1 are consistent with square-planar coordination. Addition of exogenous
15N-labeled imidazole or histidine to the His117Gly mutant generates type 1 or type 2 sites, respectively. Because neither the
above nor the His46Gly mutant reconstituted with 15N-imidazole exhibits significant isotope dependence, the histidine ligands can be ruled out as important contributors to the
RR spectrum. Instead, a variety of evidence, including extensive isotope shifts upon global substitution with 15N, suggests that the multiple RR modes of azurin are due principally to vibrations of the cysteine ligand. These are resonance-enhanced
through kinematic coupling with the Cu–S stretch in the ground state or through an excited-state A-term mechanism involving
a Cu-cysteinate chromophore that extends into the peptide backbone.
Received: 29 July 1996 / Accepted: 9 November 1996 相似文献
122.
Teppei Ikeya David Ban Donghan Lee Yutaka Ito Koichi Kato Christian Griesinger 《Biochimica et Biophysica Acta (BBA)/General Subjects》2018,1862(2):287-306
Background
To understand the mechanisms related to the ‘dynamical ordering’ of macromolecules and biological systems, it is crucial to monitor, in detail, molecular interactions and their dynamics across multiple timescales. Solution nuclear magnetic resonance (NMR) spectroscopy is an ideal tool that can investigate biophysical events at the atomic level, in near-physiological buffer solutions, or even inside cells.Scope of review
In the past several decades, progress in solution NMR has significantly contributed to the elucidation of three-dimensional structures, the understanding of conformational motions, and the underlying thermodynamic and kinetic properties of biomacromolecules. This review discusses recent methodological development of NMR, their applications and some of the remaining challenges.Major conclusions
Although a major drawback of NMR is its difficulty in studying the dynamical ordering of larger biomolecular systems, current technologies have achieved considerable success in the structural analysis of substantially large proteins and biomolecular complexes over 1 MDa and have characterised a wide range of timescales across which biomolecular motion exists. While NMR is well suited to obtain local structure information in detail, it contributes valuable and unique information within hybrid approaches that combine complementary methodologies, including solution scattering and microscopic techniques.General significance
For living systems, the dynamic assembly and disassembly of macromolecular complexes is of utmost importance for cellular homeostasis and, if dysregulated, implied in human disease. It is thus instructive for the advancement of the study of the dynamical ordering to discuss the potential possibilities of solution NMR spectroscopy and its applications. This article is part of a Special Issue entitled “Biophysical Exploration of Dynamical Ordering of Biomolecular Systems” edited by Dr. Koichi Kato. 相似文献123.
Sara Lago Matteo Nadai Monica Rossetto Sara N. Richter 《Biochimica et Biophysica Acta (BBA)/General Subjects》2018,1862(6):1276-1282
Background
G-quadruplexes (G4s) are nucleic acids secondary structures formed in guanine-rich sequences. Anti-G4 antibodies represent a tool for the direct investigation of G4s in cells. Surface Plasmon Resonance (SPR) is a highly sensitive technology, suitable for assessing the affinity between biomolecules. We here aimed at improving the orientation of an anti-G4 antibody on the SPR sensor chip to optimize detection of binding antigens.Methods
SPR was employed to characterize the anti-G4 antibody interaction with G4 and non-G4 oligonucleotides. Dextran-functionalized sensor chips were used both in covalent coupling and capturing procedures.Results
The use of two leading molecule for orienting the antibody of interest allowed to improve its activity from completely non-functional to 65% active. The specificity of the anti-G4 antobody for G4 structures could thus be assessed with high sensitivity and reliability.Conclusions
Optimization of the immobilization protocol for SPR biosensing, allowed us to determine the anti-G4 antibody affinity and specificity for G4 antigens with higher sensitivity with respect to other in vitro assays such as ELISA. Anti-G4 antibody specificity is a fundamental assumption for the future utilization of this kind of antibodies for monitoring G4s directly in cells.General significance
The heterogeneous orientation of amine-coupling immobilized ligands is a general problem that often leads to partial or complete inactivation of the molecules. Here we describe a new strategy for improving ligand orientation: driving it from two sides. This principle can be virtually applied to every molecule that loses its activity or is poorly immobilized after standard coupling to the SPR chip surface. 相似文献124.
Behrooz Shojaee Sadi Mansour Bayat Parviz Tajik Seyed Jamal Hashemi 《Saudi Journal of Biological Sciences》2018,25(1):171-177
The specific immune-reaction between the anti-citrinin antibody immobilized on the surface of magnetic/silica core–shell (MSCS) and the citrinin–Rho123–BSA conjugate brings the Rho123 fluorophore as an acceptor and the QDs as a donor in close spatial proximity and causes FRET for occurring upon photo-excitation of the QDs. The novelties of this study include: (1) immobilization of the MSCS; (2) large amount of the immobilized QDs, and (3) immobilization of a large amount of Rho123 on the BSA macromolecule. Cd/Te QDs were synthesized by the simultaneous reduction of cadmium chloride and tellurium in the presence of sodium borohydride. Magnetic nanoparticles were synthesized using FeSO4 and FeCl3. The prepared magnetic nanoparticles shelled by silica using tetraethoxysilane in the presence of ammonia. Transmission electron microscopy (TEM) analysis was used for investigating shape and monodispersity of the nanoparticles. EDC/NHS was used as a cross linking agent for immobilization of the QDs, conjugation of citrinin to amino groups of BSA, labeling of BSA with Rho123 and also for immobilization of the amino-functionalized MSCS on the immobilized QDs. Immobilization of the anti-citrinin antibody on the surface of the amino-functionalized MSCS was performed by Schiff-base mechanism. By using these three effective strategies, sensitivity of the designed nanobiosensor was incredibly enhanced as a very low limit of detection (up to 0.1 pM). The feasibility of this technique was tested by the detection of citrinin in the spiked human serum. Results showed that there was a linear correlation between the decreased fluorescence intensity of the Rho123 and increased fluorescence intensity of the QDs with increasing concentration of citrinin in the spiked samples in the range of 1–6 pM. According to obtained results, we conclude that this highly sensitive detection scheme is a easy, quick and impressive method that can be used in optical-based nanosensors. 相似文献
125.
Matthieu Réfrégiers A. Laigle Béatrice Jollès Gavin V. Wheeler Laurent Chinsky 《European biophysics journal : EBJ》1997,26(3):277-281
An oligodeoxynucleotide has been synthesized, which mimics an ``antigene' oligonucleotide with a polypyrimidic stretch on
its 5′ side and is protected on its 3′ side against nucelases by a naturally forming and very stable hairpin, 5′GCGAAGC3′.
The in vitro degradation of the resulting oligonucleotide d(5′TTCTCGCGAAGC3′) has already been studied by fluorescence resonance
energy transfer (FRET) (Réfrégiers et al. 1996, J Biomol Struct Dyn 14: 365 – 371). The technique required the grafting of
fluorophores at both ends of the oligonucleotide. In the present work we have compared the hairpin formed in the presence
and in the absence of such fluorophores. This was achieved by the study of the Raman spectra (excitation at 257 nm) of the
oligodeoxynucleotides H, which forms the hairpin (5′TTCTCGCGAAGC3′), and a con-trol C (5′TTCTCCGGAAGC3′) which is unable to
form the hairpin. Resonance Raman spectroscopy with 257 nm excitation greatly favors the resonance of purines and therefore
the study of the 3′ part of the oligonucleotides. The difference spectrum obtained from resonance Raman spectra of C and H
showed marker peaks specific for hairpin formation. The search for these marker peaks in difference spectra involving the
Raman spectrum of H labeled by fluorophores and either C or H proved that the fluorophores do not modify the structure of
the hairpin but only the vibrations of the two terminal bases on which the fluorophores are grafted. The use of such labeling
is then justified in order to allow oligonucleotides protected by a hairpin on their 3′ side to be studied by fluorescence
spectroscopy.
Received: 13 December 1996 / Accepted: 7 April 1997 相似文献
126.
Miwa Sugiura Tania Tibiletti Itsuki Takachi Yuya Hara Shin Kanawaku Julien Sellés Alain Boussac 《BBA》2018,1859(12):1259-1273
In Photosystem II (PSII), the Mn4CaO5-cluster of the active site advances through five sequential oxidation states (S0 to S4) before water is oxidized and O2 is generated. The V185 of the D1 protein has been shown to be an important amino acid in PSII function (Dilbeck et al. Biochemistry 52 (2013) 6824–6833). Here, we have studied its role by making a V185T site-directed mutant in the thermophilic cyanobacterium Thermosynechococcus elongatus. The properties of the V185T-PSII have been compared to those of the WT*3-PSII by using EPR spectroscopy, polarography, thermoluminescence and time-resolved UV–visible absorption spectroscopy. It is shown that the V185 and the chloride binding site very likely interact via the H-bond network linking TyrZ and the halide. The V185 contributes to the stabilization of S2 into the low spin (LS), S?=?1/2, configuration. Indeed, in the V185T mutant a high proportion of S2 exhibits a high spin (HS), S?=?5/2, configuration. By using bromocresol purple as a dye, a proton release was detected in the S1TyrZ?→?S2HSTyrZ transition in the V185T mutant in contrast to the WT*3-PSII in which there is no proton release in this transition. Instead, in WT*3-PSII, a proton release kinetically much faster than the S2LSTyrZ?→?S3TyrZ transition was observed and we propose that it occurs in the S2LSTyrZ?→?S2HSTyrZ intermediate step before the S2HSTyrZ?→?S3TyrZ transition occurs. The dramatic slowdown of the S3TyrZ?→?S0TyrZ transition in the V185T mutant does not originate from a structural modification of the Mn4CaO5 cluster since the spin S?=?3?S3 EPR signal is not modified in the mutant. More probably, it is indicative of the strong implication of V185 in the tuning of an efficient relaxation processes of the H-bond network and/or of the protein. 相似文献
127.
《Bioorganic & medicinal chemistry》2016,24(13):2947-2953
The inhibition of metallo-β-lactamases (MBL) can prevent the hydrolysis of β-lactam antibiotics and hence is a promising strategy for the treatment of antibiotic resistant infections. In this study, we present a novel reversible covalent inhibitor of the clinically relevant MBL New Delhi metallo-β-lactamase 1 (NDM-1). Electrospray ionization-mass spectrometry (ESI-MS) and single site directed mutagenesis were used to show that the inhibitor forms a covalent bond with Lys224 in the active site of NDM-1. The inhibitor was further characterized using an enzyme inhibition assay, a surface plasmon resonance (SPR) based biosensor assay and covalent docking. The determined inhibition constant (KI1) was 580 nM and the inhibition constant for the initial complex (KI) was 76 μM. To our knowledge, this inhibitor is the first example for a reversible covalent non-β-lactam inhibitor targeting NDM-1 and a promising starting point for the design of potent covalent inhibitors. 相似文献
128.
Kathleen M. Vogel Songzhou Hu T. G. Spiro Elizabeth A. Dierks Anita E. Yu J. N. Burstyn 《Journal of biological inorganic chemistry》1999,4(6):804-813
1 , the resting Fe(II) state is mainly 6-coordinate and low-spin, and the CO adduct has vibrational frequencies characteristic
of a histidine-heme-CO complex in a hydrophobic environment. In contrast, the protein sGC2 is 5-coordinate, high-spin in the resting state, and the CO adduct has perturbed vibrational frequencies indicative of a
negatively polarizing residue in the binding pocket. The differences may result from the need to reconstitute sGC1 or different isolation procedures for sGC1 versus sGC2. However, both sGC1 and sGC2 are activated by the same mechanism, namely displacement of the proximal histidine ligand upon NO binding, and neither one
is activated by CO. If CO is an activator in vivo, some additional molecular component is required.
Received: 11 February 1999 / Accepted: 17 September 1999 相似文献
129.
目的:探讨磁共振水成像技术对脊柱疾病诊断的应用价值。方法:采用快速高级自旋回波(FASE)、重T2WI及脂肪抑制序列对300例病人检查行磁共振椎管水成像(MRmyelography,MRM)。结果:MRM显示正常25例,MRM异常275例,清楚显示原发病变与邻近脊髓腔、脊髓、神经根的相关关系。结论:MRM具有无创伤、无辐射、速度快,不需对比剂,患者易接受的特点。MRM与常规MRI图像结合可获得全面、客观的病变信息,MRM图像可取代X线脊髓造影和CT脊髓造影。 相似文献
130.
Marzena B. Fitzpatrick Roman S. Czernuszewicz 《Journal of biological inorganic chemistry》2009,14(4):611-620
Metal-substituted blue copper proteins (cupredoxins) have been successfully used to study the effect of metal-ion identity
on their active-site properties, specifically the coordination geometry and metal–ligand bond strengths. In this work, low-temperature
(77 K) resonance Raman (RR) spectra of the blue copper protein Alcaligenes xylosoxidans azurin I and its Ni(II) derivative are reported. A detailed analysis of all observed bands is presented and responsiveness
to metal substitution is discussed in terms of structural and bonding changes. The native cupric site exhibits a RR spectrum
characteristic of a primarily trigonal planar (type 1) coordination geometry, identified by the ν(Cu–S)Cys markers at 373, 399, 409, and 430 cm−1. Replacement of Cu(II) with Ni(II) results in optical and RR spectra that reveal (1) a large hypsochromic shift in the main
(Cys)S → M(II) charge-transfer absorption from 622 to 440 nm, (2) greatly reduced metal–thiolate bonding interaction, indicated
by substantially lower ν(Ni–S)Cys stretching frequencies, (3) elevation of the cysteine ν(C
β
–S) stretching, amide III, and ρ
s(C
β
H2) scissors vibrational modes, and (4) primarily four-coordinated, trigonally distorted tetrahedral geometry of the Ni(II)
site that is marked by characteristic ν(Ni–S)Cys stretching RR bands at 347, 364, and 391 cm−1. Comparisons of the electronic and vibrational properties between A. xylosoxidans azurin I and its closely structurally related azurin from Pseudomonas aeruginosa are made and discussed. For cupric azurins, the intensity-weighted average M(II)–S(Cys) stretching frequencies are calculated
to be ν(Cu–S)iwa = 406.3 and 407.6 cm−1, respectively. These values decreased to ν(Ni–S)iwa = 359.3 and 365.5 cm−1, respectively, after Ni(II) → Cu(II) exchange, suggesting that the metal–thiolate interactions are similar in the two native
proteins but are much less alike in their Ni(II)-substituted forms. 相似文献