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1.
《Inorganica chimica acta》1988,153(3):183-188
The O2 affinities on base adducts of four atropisomers of picket fence porphyrin Co(TpivPP), and the corresponding α4 complex containing valeramido pickets instead of pivalamido Co(α4-TvalPP) were measured in several solvents at O or −15 °C. The O2 affinities of the α4 complexes are the lowest in DMF which is the most polar of the solvents used, while those of the other isomers are the highest in DMF. This observation was explained in terms of direct and indirect interactions between the solvent and the bound O2. The trans-α2 complex shows higher O2 affinity in dichloromethane than those in aromatic solvents because of the preferential solvation of the deoxy complex in the solvents. The variation of the O2 affinities of this system to solvents is considerably smaller than those of ‘flat porphyrin’ complexes. This result suggested that the pocket polarity introduced by the amide groups weakens the solvent–solute interaction on the O2 affinities of this system and also that the solvation of the oxy state rather than the deoxy state predominantly affects the O2 affinities. It was concluded that the enhanced O2 uptake by the picket fence may be due to the stabilization of the oxy state by intramolecular interactions rather than to destabilization of the deoxy state by inhibiting solvation for the active site. 相似文献
2.
Makoto Shimizu Fred Basolo Maria N. Vallejo Jack E. Baldwin 《Inorganica chimica acta》1984,91(4):251-255
Oxygen and NO binding constants are reported for Fe(Por)(B) [1] complexes. The results show a good correlation between O2 and NO affinities, and this is attributed to the similar bent structures of the FeOO and FeNO moieties. Evidence is presented to show that iron(II) C3-capped porphyrins have a low affinity for O2 because of ligand coordination on the cavity side of the cap. 相似文献
3.
Most biological substrates have distinctive sizes, shapes, and charge distributions which can be recognized specifically
by proteins. In contrast, myoglobin must discriminate between the diatomic gases O2, CO, and NO which are apolar and virtually the same size. Selectivity occurs at the level of the covalent Fe-ligand complexes,
which exhibit markedly different bond strengths and electrostatic properties. By pulling a water molecule into the distal
pocket, His64(E7)1 inhibits the binding of all three ligands by a factor of ∼10 compared to that observed for protoheme-imidazole complexes
in organic solvents. In the case of O2 binding, this unfavorable effect is overcome by the formation of a strong hydrogen bond between His64(E7) and the highly
polar FeO2 complex. This favorable electrostatic interaction stabilizes the bound O2 by a factor of ∼1000, and the net result is a 100-fold increase in overall affinity compared to model hemes or mutants with
an apolar residue at position 64. Electrostatic interaction between FeCO and His64 is very weak, resulting in only a two-
to three-fold stabilization of the bound state. In this case, the inhibitory effect of distal pocket water dominates, and
a net fivefold reduction in K
CO is observed for the wild-type protein compared to mutants with an apolar residue at position 64. Bound NO is stabilized ∼tenfold
by hydrogen bonding to His64. This favorable interaction with FeNO exactly compensates for the tenfold inhibition due to the
presence of distal pocket water, and the net result is little change in K
NO when the distal histidine is replaced with apolar residues. Thus, it is the polarity of His64 which allows discrimination
between the diatomic gases. Direct steric hindrance by this residue plays a minor role as judged by: (1) the independence
of K
O2, K
CO, and K
NO on the size of apolar residues inserted at position 64, and (2) the observation of small decreases, not increases, in CO
affinity when the mobility of the His64 side chain is increased. Val68(E11) does appear to hinder selectively the binding
of CO. However, the extent is no more than a factor of 2–5, and much smaller than electrostatic stabilization of bound O2 by the distal histidine.
Received, accepted: 23 May 1997 相似文献
4.
Mauricio Isaacs 《Inorganica chimica acta》2006,359(12):3847-3854
A series of new heteroleptic, tris(polypyridyl)chromium(III) complexes, [Cr(phen)2L]3+ (L = substituted phenanthrolines or bipyridines), has been prepared and characterized, and their photophyical properties in a number of solvents have been investigated. X-ray crystallography measurements confirmed that the cationic (3+) units contain only one ligand L plus two phenanthroline ligands. Electrochemical and photophysical data showed that both ground state potentials and lifetime decays are sensitive to ligand structure and the nature of the solvent with the exception of compounds containing L = 5-amino-1,10-phenanthroline (aphen) and 2,2′-bipyrimidine (bpm). Addition of electron-donating groups in the ligand structure shifts redox potentials to more negative values than those observed for the parent compound, [Cr(phen)3]3+. Emission decays show a complex dependence with the solvent. The longest lifetime was observed for [Cr(phen)2(dip)]3+ (dip = 4,7-diphenylphenanthroline) in air-free aqueous solutions, τ = 273 μs. Solvent effects are explained in terms of the affinity of hydrophobic complexes for non-polar solvent molecules and the solvent microstructure surrounding chromium units. 相似文献
5.
6.
The conformational properties of the cyclohexadepsipeptide antibiotic Beauvericin have been investigated by 1H-NMR spectroscopy in polar (C2H3O2H) and non-polar (CCl4, C62H6, C2HCl3) solvents and in two solvent mixtures; one a mixture of a polar and non-polar solvent (C2H3O2H/CCl4) and the other an aromatic solvent in a non-polar environment (C62H6/CCl4). The ion-complexation properties of Beauvericin with alkali metal halides (Li+, Na+, K+, Cs+) have also been studied. It is demonstrated that changes in chemical shifts of Beauvericin with concentration, with polarity of solvent or with added alkali metal ion reflect changes not only in the solvent properties but also changes in backbone conformation and changes due to ion-complexation, where appropriate, and therefore cannot be used, by themselves, to determine the conformation of the molecule, its self-aggregation properties, or the stoichiometry of the metal ion-complex. The backbone conformations of Beauvericin in different environments are determined by methods that are independent of chemical shift analysis; i.e., by measurements of 5J(HH) magnitudes observed between the alpha-CH protons of the L-phenylalanine and D-hydroxyisovaleric acid (DHyIv) residues and by nuclear Overhauser effect measurements observed between alpha-CH(HyIv) and (N)-CH3(Phe) proton signals. In the knowledge of these results the chemical shifts of Beauvericin in different environments can then be rationalised. It is found that the conformation of Beauvericin in a polar solvent is different from that found in a non-polar solvent and from that found for the in the ion-complexed form is similar to that found in non-polar solvents. By taking into account the conformational properties of the L-phenylalanine and DHyIv side-chains, it is possible to assign unambiguously the magnetically non-equivalent beta-CH2(Phe) and gamma Me(HyIv) proton signals and so elucidate the complete conformational behaviour of the uncomplexed forms of Beauvericin in a polar and a non-polar environment, and of the ion-complexed form of Beauvericin in a polar solvent. 相似文献
7.
Protein–protein interactions are intrinsic to virtually every cellular process. Predicting the binding affinity of protein–protein complexes is one of the challenging problems in computational and molecular biology. In this work, we related sequence features of protein–protein complexes with their binding affinities using machine learning approaches. We set up a database of 185 protein–protein complexes for which the interacting pairs are heterodimers and their experimental binding affinities are available. On the other hand, we have developed a set of 610 features from the sequences of protein complexes and utilized Ranker search method, which is the combination of Attribute evaluator and Ranker method for selecting specific features. We have analyzed several machine learning algorithms to discriminate protein‐protein complexes into high and low affinity groups based on their Kd values. Our results showed a 10‐fold cross‐validation accuracy of 76.1% with the combination of nine features using support vector machines. Further, we observed accuracy of 83.3% on an independent test set of 30 complexes. We suggest that our method would serve as an effective tool for identifying the interacting partners in protein–protein interaction networks and human–pathogen interactions based on the strength of interactions. Proteins 2014; 82:2088–2096. © 2014 Wiley Periodicals, Inc. 相似文献
8.
《Inorganica chimica acta》1986,113(1):31-36
A series of dimeric picket fence porphyrinatocobalt(II) complexeses in which the length of the bridging chain controls the dioxygen affinity was newly derived from the coupling of two meso-mono- (β-o-aminophenyl)-tris-(α,α,α-o-pivaloylamidophenyl)- porphyrins with (CH2)n(COCl)2 (n = 1, 3, 5 or 7). Some of the dimeric complexes form a unique ‘sandwich structure’ upon binding with certain bidentate ligands, and their dioxygen affinities are greatly increased compared with those for corresponding monomeric complexes. The relationship observed between the length of the bridging chain and the dioxygen affinity of the dimer complex having a sandwich structure is interpreted in terms of the displacement mechanism of the metal atom from a porphyrin plane. 相似文献
9.
David R. Williams 《Inorganica chimica acta》1985,106(2):115-118
The solvent, pressure and temperature dependencies of the lowest energy metal to ligand charge transfer absorption bands were studied for a series of complexes of the type Mo(CO)4(N), where N = 2,2′-bipyridine, 1,10-phenanthroline and biacetylbis(phenylimine). Throughout the series of complexes the absorption bands shift to shorter wavelength in more polar solvents or on increasing the pressure in a particular solvent, but to longer wavelengths on increasing temperature. These main tendencies can be accounted for in terms of solvent polarity and its dependence on pressure and temperature. 相似文献
10.
《BBA》2023,1864(2):148953
The multi-subunit membrane protein complex photosystem II (PSII) catalyzes the light-driven oxidation of water and with this the initial step of photosynthetic electron transport in plants, algae, and cyanobacteria. Its biogenesis is coordinated by a network of auxiliary proteins that facilitate the stepwise assembly of individual subunits and cofactors, forming various intermediate complexes until fully functional mature PSII is present at the end of the process. In the current study, we purified PSII complexes from a mutant line of the thermophilic cyanobacterium Thermosynechococcus vestitus BP-1 in which the extrinsic subunit PsbO, characteristic for active PSII, was fused with an N-terminal Twin-Strep-tag. Three distinct PSII complexes were separated by ion-exchange chromatography after the initial affinity purification. Two complexes differ in their oligomeric state (monomeric and dimeric) but share the typical subunit composition of mature PSII. They are characterized by the very high oxygen evolving activity of approx. 6000 μmol O2·(mg Chl·h)?1. Analysis of the third (heterodimeric) PSII complex revealed lower oxygen evolving activity of approx. 3000 μmol O2·(mg Chl·h)?1 and a manganese content of 2.7 (±0.2) per reaction center compared to 3.7 (±0.2) of fully active PSII. Mass spectrometry and time-resolved fluorescence spectroscopy further indicated that PsbO is partially replaced by Psb27 in this PSII fraction, thus implying a role of this complex in PSII repair. 相似文献
11.
《Journal of enzyme inhibition and medicinal chemistry》2013,28(5):809-815
AbstractThe aim of this study is to propose an improved computational methodology, which is called Compressed Images for Affinity Prediction-2 (CIFAP-2) to predict binding affinities of structurally related protein–ligand complexes. CIFAP-2 method is established based on a protein–ligand model from which computational affinity information is obtained by utilizing 2D electrostatic potential images determined for the binding site of protein–ligand complexes. The quality of the prediction of the CIFAP-2 algorithm was tested using partial least squares regression (PLSR) as well as support vector regression (SVR) and adaptive neuro-fuzzy ?nference system (ANFIS), which are highly promising prediction methods in drug design. CIFAP-2 was applied on a protein–ligand complex system involving Caspase 3 (CASP3) and its 35 inhibitors possessing a common isatin sulfonamide pharmacophore. As a result, PLSR affinity prediction for the CASP3–ligand complexes gave rise to the most consistent information with reported empirical binding affinities (pIC50) of the CASP3 inhibitors. 相似文献
12.
The synthesis of new platinum bipy (bipy = 2,2′-bipyridyl) complexes containing phenoxide ligands is reported, together with kinetic studies of their oxidative addition reactions with MeI to produce phenoxo platinum(IV) complexes. Complexes of the form [(bipy)Pt(OC6H4-4-X)2] (X = OCH3, CH3, H, Br, Cl) are prepared by the reaction of the chloro complex [(bipy)PtCl2] with substituted phenols and KOH in a two phase system of water and chloroform in the presence of benzyl triphenylphosphonium chloride. Platinum(IV) complexes are formed by oxidative addition of MeI to the platinum(II) complexes obtained. The complexes are characterized by elemental analysis, UV-Vis, IR, mass spectrometry and 1H and 13C NMR spectroscopy.The reaction of methyl iodide with [(bipy)Pt(OC6H4-4-OMe)2] to give [(bipy)PtMe(I)(OC6H4-4-OMe)2] follows the rate law rate = k2[(bipy)Pt(OC6H4-4-OMe)2][MeI]. The values of k2 increase with increasing polarity of the solvent, suggesting a polar transition state for the reaction. 相似文献
13.
Takao Osako Shigenori Nagatomo Teizo Kitagawa Christopher J. Cramer Shinobu Itoh 《Journal of biological inorganic chemistry》2005,10(5):581-590
Copper(II) complexes supported by bulky tridentate ligands L1H (N,N-bis(2-quinolylmethyl)-2-phenylethylamine) and L1Ph (N,N-bis(2-quinolylmethyl)-2,2-diphenylethylamine) have been prepared and their crystal structures as well as some physicochemical properties have been explored. Each complex exhibits a square pyramidal structure containing a coordinated solvent molecule at an equatorial position and a weakly coordinated counter anion (or water) at an axial position. The copper(II) complexes reacted readily with H2O2 at a low temperature to give mononuclear hydroperoxo copper(II) complexes. Kinetics and DFT studies have suggested that, in the initial stage of the reaction, deprotonated hydrogen peroxide attacks the cupric ion, presumably at the axial position, to give a hydroperoxo copper(II) complex retaining the coordinated solvent molecule (H
R
·S). H
R
·S then loses the solvent to give a tetragonal copper(II)-hydroperoxo complex (H
R
), in which the –OOH group may occupy an equatorial position. The copper(II)–hydroperoxo complex H
R
exhibits a relatively high O–O bond stretching vibration at 900 cm−1 compared to other previously reported examples.Electronic Supplementary Material Supplementary material is available for this article at 相似文献
14.
U. Casellato D. Fregona S. Sitran S. Tamburini P. A. Vigato 《Inorganica chimica acta》1985,110(3):181-190
A new heptadentate compartmental ligand has been synthesized by condensation of 3-formylsalicylic acid and 1,5-diamino-3-thiapentane in methanol (H4La). This Schiff base contains an inner N2SO2 and an outer O2O2 site and gives, by reaction with copper(II), nickel(II) and uranyl(VI) diacetate, mononuclear, homo- and heterobinuclear complexes. In the mononuclear copper and nickel complexes, the metal ion is in the inner N2SO2 site, while it is in the outer O2O2 for uranyl; a solvent molecule fills the fifth equatorial coordination position in this last complex. The physico-chemical properties of the compounds are discusscd on the basis of infrared, electronic and magnetic data and by comparison with the analogous complexes with the ligand obtained by reaction of 3- formylsalicylic acid and diethylenetriamine (H4Lb). The mononuclear copper and the heterodinuclear copper-uranyl complexes show anomalously low magnetic moments. 相似文献
15.
《Journal of Free Radicals in Biology & Medicine》1986,2(1):3-11
Cooper complexes of 1,10-phenanthroline and some substituted 1,10-phenanthroline cleave DNA in the presence of a reducing agent and molecular oxygen. Generally, the damage is attributed to hydroxyl radicals which are formed through the Haber-Weiss reaction. It is assumed that this reaction occurs with the ternary metal complexes with the biological target and the mechanism is defined as the “site specific mechanism.” In these systems, O2− drives the cycle through the reduction of copper(II). On the other hand, these same copper complexes catalyze the dismutation of O2− and thus should protect the systems from O2− toxicity. In this article, the toxicity of these complexes is explained on kinetic grounds. A general discussion on the various factors which could cause the metal ions or their complexes to act either as protectors from O2− toxicity or as sensitizers of toxic effects of O2− is given. 相似文献
16.
Suhaila Rahman Ichiro Yamato Shinya Saijo Kenji Mizutani Yoshiko Ishizuka-Katsura Noboru Ohsawa Takaho Terada Mikako Shirouzu Shigeyuki Yokoyama So Iwata Takeshi Murata 《PloS one》2013,8(2)
Peripheral stalk subunits of eukaryotic or mammalian vacuolar ATPases (V-ATPases) play key roles in regulating its assembly and disassembly. In a previous study, we purified several subunits and their isoforms of the peripheral stalk region of Homo sapiens (human) V-ATPase; such as C1, E1G1, H, and the N-terminal cytoplasmic region of Vo, a1. Here, we investigated the in vitro binding interactions of the subunits at the stalk region and measured their specific affinities. Surface plasmon resonance experiments revealed that the subunit C1 binds the E1G1 heterodimer with both high and low affinities (2.8 nM and 1.9 µM, respectively). In addition, an E1G1-H complex can be formed with high affinity (48 nM), whereas affinities of other subunit pairs appeared to be low (∼0.21−3.0 µM). The putative ternary complex of C1-H-E1G1 was not much strong on co-incubation of these subunits, indicating that the two strong complexes of C1-E1G1 and H-E1G1 in cooperation with many other weak interactions may be sufficiently strong enough to withstand the torque of rotation during catalysis. We observed a partially stable quaternary complex (consisting of E1G1, C1, a1NT, and H subunits) resulting from discrete peripheral subunit interactions stabilizing the complex through their intrinsic affinities. No binding was observed in the absence of E1G1 (using only H, C1, and a1NT); therefore, it is likely that, in vivo, the E1G1 heterodimer has a significant role in the initiation of subunit assembly. Multiple interactions of variable affinity in the stalk region may be important to the mechanism of reversible dissociation of the intact V-ATPase. 相似文献
17.
Mark P. Wentland Rongliang Lou Qun Lu Yigong Bu Melissa A. VanAlstine Dana J. Cohen Jean M. Bidlack 《Bioorganic & medicinal chemistry letters》2009,19(1):203-208
A series of 15 novel opioid derivatives were made where the prototypic phenolic-OH group of traditional opioids was replaced by a carboxamido (CONH2) group. For 2,6-methano-3-benzazocines and morphinans similar or, in a few instances, enhanced affinity for μ, δ and κ opioid receptors was observed when the OH → CONH2 switch was applied. For 4,5α-epoxymorphinans, binding affinities for the corresponding carboxamide derivatives were much lower than the OH partner consistent with our pharmacophore hypothesis concerning carboxamide bioactive conformation. The active metabolite of tramadol and its carboxamide counterpart had comparable affinities for the three receptors. 相似文献
18.
U. Casellato D. Fregona S. Sitran S. Tamburini P.A. Vigato 《Inorganica chimica acta》1985,110(3):161-167
A new heptadentate compartmental ligand has been synthesized by condensation of 3-formylsalicylic acid and 1,5-diamino-3-thiapentane in methanol (H4La). This Schiff base contains an inner N2SO2 and an outer O2O2 site and gives, by reaction with copper(II), nickel(II) and uranyl(VI) diacetate, mononuclear, homo- and heterobinuclear complexes. In the mononuclear copper and nickel complexes, the metal ion is in the inner N2SO2 site, while it is in the outer O2O2 for uranyl; a solvent molecule fills the fifth equatorial coordination position in this last complex. The physico-chemical properties of the compounds are discusscd on the basis of infrared, electronic and magnetic data and by comparison with the analogous complexes with the ligand obtained by reaction of 3- formylsalicylic acid and diethylenetriamine (H4Lb). The mononuclear copper and the heterodinuclear copper-uranyl complexes show anomalously low magnetic moments. 相似文献
19.
Casey L. Quinlan Renata L. S. Goncalves Martin Hey-Mogensen Nagendra Yadava Victoria I. Bunik Martin D. Brand 《The Journal of biological chemistry》2014,289(12):8312-8325
Several flavin-dependent enzymes of the mitochondrial matrix utilize NAD+ or NADH at about the same operating redox potential as the NADH/NAD+ pool and comprise the NADH/NAD+ isopotential enzyme group. Complex I (specifically the flavin, site IF) is often regarded as the major source of matrix superoxide/H2O2 production at this redox potential. However, the 2-oxoglutarate dehydrogenase (OGDH), branched-chain 2-oxoacid dehydrogenase (BCKDH), and pyruvate dehydrogenase (PDH) complexes are also capable of considerable superoxide/H2O2 production. To differentiate the superoxide/H2O2-producing capacities of these different mitochondrial sites in situ, we compared the observed rates of H2O2 production over a range of different NAD(P)H reduction levels in isolated skeletal muscle mitochondria under conditions that favored superoxide/H2O2 production from complex I, the OGDH complex, the BCKDH complex, or the PDH complex. The rates from all four complexes increased at higher NAD(P)H/NAD(P)+ ratios, although the 2-oxoacid dehydrogenase complexes produced superoxide/H2O2 at high rates only when oxidizing their specific 2-oxoacid substrates and not in the reverse reaction from NADH. At optimal conditions for each system, superoxide/H2O2 was produced by the OGDH complex at about twice the rate from the PDH complex, four times the rate from the BCKDH complex, and eight times the rate from site IF of complex I. Depending on the substrates present, the dominant sites of superoxide/H2O2 production at the level of NADH may be the OGDH and PDH complexes, but these activities may often be misattributed to complex I. 相似文献
20.
《Bioorganic & medicinal chemistry letters》2014,24(13):2954-2956
The enantiomers of two analogs of Sazetidine-A as well as several other novel biosteric analogues were synthesized. Their binding affinities at three major nAChRs subtypes and selectivity profiles were determined. Though many (S)-enantiomers of Sazetidine-A analogs have high binding affinities and good subtype selectivities, it is not a general rule that (S)-enantiomers are better than their (R) counterparts. Compound 11, of which the ethynyl group was replaced by its’ bioisostere—the triazole via click chemistry, showed a high binding affinity to α4β2 subtype (Ki = 1.3 nM) and better selectivity to the α4β2 subtype over α3β4 subtype with that of Sazetidine-A. The azide compound 15, a potential photoaffinity label, showed improved high selectivity and similar binding property profile with that of Sazetidine-A. The biaryl analog 17 exhibited a much lower affinity as compared to Sazetidine-A indicating the importance of a ‘long tail’ side chain for α4β2 nAChR binding. 相似文献