The Effects of Cryoprotection on the Structure and Activity of p21ras:Implications for Electron Spin-Echo Envelope Modulation Spectroscopy

Halkides, Christopher J.; Farrar, Christian T.; Singel, David J.

doi:10.1006/jmre.1998.1520

Cited by 12 publications

(10 citation statements)

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“…Given the larger amount of glycerol in our preparations (20%), we reason that glycerol increases the population of these broad S 3 EPR signals. In fact, glycerol has been shown to effect the populations of CW EPR signals of the S 2 state. − In Mn II species, glycerol can alter the coordination environment of Mn II centers and produce observable changes to the ZFS interaction. , On the basis of our EDNMR results, which suggest that the coordination environment of Mn4A (and/or Mn3B) is perturbed, it is easy to envision that glycerol may occupy an area near O4, similar to that of the proposed methanol site. ,, However, given the structural differences between glycerol and methanol, the exact placement of glycerol may differ from methanol in the vicinity of O4 and thus lead to different effects to the OEC in the S 3 state. Inspection of recent XFEL structures of the S 3 state reveals that multiple glycerol molecules occupy areas approximately 11 Å from Mn1D, while other glycerol molecules occupy areas approximately 25 Å from Mn4A and Mn3B (Figure S7).…”

Section: Discussionmentioning

confidence: 84%

“…48−50 In Mn II species, glycerol can alter the coordination environment of Mn II centers and produce observable changes to the ZFS interaction. 51,52 On the basis of our EDNMR results, which suggest that the coordination environment of Mn4A (and/or Mn3B) is perturbed, it is easy to envision that glycerol may occupy an area near O4, similar to that of the proposed methanol site. 28,53,54 However, given the structural differences between glycerol and methanol, the exact placement of glycerol may differ from methanol in the vicinity of O4 and thus lead to different effects to the OEC in the S 3 state.…”

Section: ■ Discussionmentioning

confidence: 90%

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Pulse EPR Spectroscopic Characterization of the S₃ State of the Oxygen-Evolving Complex of Photosystem II Isolated from Synechocystis

2020

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The S 3 state is the last semi-stable state in the water splitting reaction that is catalyzed by the Mn 4 O 5 Ca cluster that makes up the oxygen-evolving complex (OEC) of photosystem II (PSII). Recent high-field/frequency (95 GHz) electron paramagnetic resonance (EPR) studies of PSII isolated from the thermophilic cyanobacterium Thermosynechococcus elongatus have found broadened signals induced by chemical modification of the S 3 state. These signals are ascribed to an S 3 form that contains a fivecoordinate Mn IV center bridged to a cuboidal Mn IV 3 O 4 Ca unit. High-resolution X-ray free-electron laser studies of the S 3 state have observed the OEC with all-octahedrally coordinated Mn IV in what is described as an open cuboid-like cluster. No five-coordinate Mn IV centers have been reported in these S 3 state structures. Here, we report high-field/frequency (130 GHz) pulse EPR of the S 3 state in Synechocystis sp. PCC 6803 PSII as isolated in the presence of glycerol. The S 3 state of PSII from Synechocystis exhibits multiple broadened forms (≈69% of the total signal) similar to those seen in the chemically modified S 3 centers from T. elongatus. Field-dependent ELDOR-detected nuclear magnetic resonance resolves two classes of 55 Mn nuclear spin transitions: one class with small hyperfine couplings (|A| ≈ 1−7 MHz) and another with larger hyperfine couplings (|A| ≈ 100 MHz). These results are consistent with an all-Mn IV 4 open cubane structure of the S 3 state and suggest that the broadened S 3 signals arise from a perturbation of Mn4A and/or Mn3B, possibly induced by the presence of glycerol in the as-isolated Synechocystis PSII.

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Section: Discussionmentioning

confidence: 84%

Section: ■ Discussionmentioning

confidence: 90%

Pulse EPR Spectroscopic Characterization of the S₃ State of the Oxygen-Evolving Complex of Photosystem II Isolated from Synechocystis

2020

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“…The minor disparity between the magnitudes of D for [Mn(II)(H 2 O) 6 ] 2+ likely results from a difference in glassing agent [39,40]. Indeed, Halkides et al [107] showed that glycerol, used in previous studies, can displace water ligands from Mn(II) centers, indicating that our choice of a much lower concentration of ethylene glycol (20% vs. 50% [v/v], respectively) may result in a more representative spectrum of [Mn(II)(H 2 O) 6 ] 2+ . More significant, however, is the difference between the two sets of parameters for Mn(II)ATP.…”

Section: Pulsed Epr Studiesmentioning

confidence: 99%

Multifrequency pulsed EPR studies of biologically relevant manganese(II) complexes

et al. 2007

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Electron paramagnetic resonance studies at multiple frequencies (MF EPR) can provide detailed electronic structure descriptions of unpaired electrons in organic radicals, inorganic complexes, and metalloenzymes. Analysis of these properties aids in the assignment of the chemical environment surrounding the paramagnet and provides mechanistic insight into the chemical reactions in which these systems take part. Herein, we present results from pulsed EPR studies performed at three different frequencies (9, 31, and 130 GHz) on [Mn(II)(H 2 O) 6 ] 2+ , Mn(II) adducts with the nucleotides ATP and GMP, and the Mn(II)-bound form of the hammerhead ribozyme (MnHH). Through line shape analysis and interpretation of the zero-field splitting values derived from successful simulations of the corresponding continuous-wave and field-swept echodetected spectra, these data are used to exemplify the ability of the MF EPR approach in distinguishing the nature of the first ligand sphere. A survey of recent results from pulsed EPR, as well as pulsed electron-nuclear double resonance and electron spin echo envelope modulation spectroscopic studies applied to Mn(II)-dependent systems, is also presented. Mn-Containing Biological SystemsManganese operates as a cofactor in numerous proteins, serving both catalytic and structural roles [1][2][3][4]. Many Mn-dependent enzymes take advantage o f the rich redox chemistry available to the metal, accessing the +2, +3, +4, and perhaps even the +5 oxidation states during their turnover. For example, Mn-superoxide dismutase (MnSOD), which detoxifies the cell of the superoxide radical , cycles between the Mn(II) and Mn(III) oxidation states via the ping-pong type mechanism shown below [5][6][7][8][9].(1a) (1b) Other examples of such mononuclear redox-active enzymes include the manganese peroxidase responsible for lignin degradation by white-rot fungus [10][11][12]; a unique Mndependent form of lipoxygenase [13][14][15][16]; oxalate decarboxylase [17,18]; as well as an extradiol catechol dioxygenase [19][20][21]. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptIn order to help minimize kinetic and thermodynamic penalties associated with electron transfer events and the execution of chemical reactions, two or more metal centers can be coupled together to provide active sites capable of conducting multiple electrons while still operating within a physiologically accessible range of reduction potentials [22]. Only three such examples of redox-active polynuclear Mn enzymes are known: Mn-catalase that disproportionates hydrogen peroxide [23][24][25][26]; a Mn form of ribonucleotide reductase (Mn-RNR) [27,28]; and, arguably the most recognized Mn-dependent enzyme, the photosynthetic core of green plants, algae, and certain cyanobacteria termed photosystem II (PSII) [29,30]. Through a series of photoinitiated electron transfer events, oxidizing equivalents are stored on the tetranuclear Mn core of PSII -the oxygen-evolving complex (OEC) -which then extracts four electr...

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“…Different concentrations of methyl α-D-glucopyranoside were used to vary echo decay times in a study that assessed the effects of cryoprotection on the structure and activity of p21ras (Halkides et al, 1998). Methyl α-D-glucopyranoside has also been used in a study to investigate saccharide-mediated protection of chaotropic-induced deactivation of concanavalin A (Figlas et al, 1997).…”

Section: Introductionmentioning

confidence: 99%

Acylation of D-Glucose Derivatives over C5H5N: Spectral Characterization and in vitro Antibacterial Activities

Kawsar¹,

Uddin²,

Manchur³

et al. 2015

International J. of Biological Chemistry

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Methyl α-D-glucopyranoside was easily prepared by the treatment of D-glucose with anhydrous methyl alcohol in presence of hydrogen chloride at freezing temperature in good yield. Then N-acetylsulfanilylation of methyl α-D-glucopyranoside has been carried out by the direct method and afforded the 6-O-N-acetylsulfanilyl derivative in an excellent yield. In order to obtain newer products, the 6-O-N-acetylsulfanilyl derivative was further transformed to a series of 2,3,4-tri-O-acyl derivatives containing a wide variety of functionalities in a single molecular framework. The chemical structures of the newly synthesized compounds were elucidated by Fourier Transform Infrared spectroscopy (FTIR), 1 H-NMR (Proton nuclear magnetic resonance) spectroscopy elemental and physicochemical properties analysis. All the newly synthesized D-glucose derivatives were tested for their in vitro antibacterial activity against some human pathogenic bacterial strains. The study revealed that a good number of acylated products exhibited promising antibacterial activities. It is expected that the acylated derivatives of D-glucose may be considered as a potential source for developing new and better antibacterial agents against a number of pathogenic organism.

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The Effects of Cryoprotection on the Structure and Activity of p21ras:Implications for Electron Spin-Echo Envelope Modulation Spectroscopy

Cited by 12 publications

References 59 publications

Pulse EPR Spectroscopic Characterization of the S₃ State of the Oxygen-Evolving Complex of Photosystem II Isolated from Synechocystis

Pulse EPR Spectroscopic Characterization of the S₃ State of the Oxygen-Evolving Complex of Photosystem II Isolated from Synechocystis

Multifrequency pulsed EPR studies of biologically relevant manganese(II) complexes

Acylation of D-Glucose Derivatives over C5H5N: Spectral Characterization and in vitro Antibacterial Activities

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The Effects of Cryoprotection on the Structure and Activity of p21ras:Implications for Electron Spin-Echo Envelope Modulation Spectroscopy

Cited by 12 publications

References 59 publications

Pulse EPR Spectroscopic Characterization of the S3 State of the Oxygen-Evolving Complex of Photosystem II Isolated from Synechocystis

Pulse EPR Spectroscopic Characterization of the S3 State of the Oxygen-Evolving Complex of Photosystem II Isolated from Synechocystis

Multifrequency pulsed EPR studies of biologically relevant manganese(II) complexes

Acylation of D-Glucose Derivatives over C5H5N: Spectral Characterization and in vitro Antibacterial Activities

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Product

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Pulse EPR Spectroscopic Characterization of the S₃ State of the Oxygen-Evolving Complex of Photosystem II Isolated from Synechocystis

Pulse EPR Spectroscopic Characterization of the S₃ State of the Oxygen-Evolving Complex of Photosystem II Isolated from Synechocystis