Asymmetrical Complex Research Articles

Visualizing chaperonin function in situ by cryo-electron tomography

Chaperonins are large barrel-shaped complexes that mediate ATP-dependent protein folding1–3. The bacterial chaperonin GroEL forms juxtaposed rings that bind unfolded protein and the lid-shaped cofactor GroES at their apertures. In vitro analyses of the chaperonin reaction have shown that substrate protein folds, unimpaired by aggregation, while transiently encapsulated in the GroEL central cavity by GroES4–6. To determine the functional stoichiometry of GroEL, GroES and client protein in situ, here we visualized chaperonin complexes in their natural cellular environment using cryo-electron tomography. We find that, under various growth conditions, around 55–70% of GroEL binds GroES asymmetrically on one ring, with the remainder populating symmetrical complexes. Bound substrate protein is detected on the free ring of the asymmetrical complex, defining the substrate acceptor state. In situ analysis of GroEL–GroES chambers, validated by high-resolution structures obtained in vitro, showed the presence of encapsulated substrate protein in a folded state before release into the cytosol. Based on a comprehensive quantification and conformational analysis of chaperonin complexes, we propose a GroEL–GroES reaction cycle that consists of linked asymmetrical and symmetrical subreactions mediating protein folding. Our findings illuminate the native conformational and functional chaperonin cycle directly within cells.

Statistical inference for a novel distribution using ranked set sampling with applications

Working on symmetrical or asymmetrical data is complicated since each requires a different probability density function. Many statistical distributions can be used for these data types, where choosing one should be satisfied with the correct data type. So, we apply the ranked set sampling technique, which is essential in gaining data when dealing with units in a population is expensive. However, their classification is simple according to the variable of interest. The Unit Generalized Rayleigh distribution has recently played a crucial role in analyzing symmetrical or asymmetrical complex data sets specifically in modeling claim and risk data used in actuarial and financial studies, and its density can take different symmetric and asymmetric possible shapes. It is proposed in various areas, such as reliability, survival, economics, actuarial science, and insurance. We applied the ranked set sampling design in this article for gaining the model parameter estimations of the unit generalized Rayleigh model. Different estimation procedures and risk measures are computed. Moreover, the performance of these measures is illustrated via numerical simulation experiments. Under different proposed estimators, we conduct the validation of the suggested ranked set sampling design via numerous Monte Carlo simulation experiments by computing average bias and mean squared errors. At the end, we illustrated two real applications of the financial area for demonstrating the potential and the supremacy of the proposed ranked set sampling estimators.

A longitudinal study on sensitivity to symmetry in writing and associations with early literacy abilities

IntroductionYoung children reportedly find symmetrical prints, such as H, easier to copy and produce from memory than asymmetrical ones. Little is known about how sensitivity to symmetry in print relates to early word reading and writing development. We examined this in Chinese, a visually complex writing system featuring symmetrical patterns, such as X or X.MethodsSixty preschoolers in Beijing completed a character decision task (Experiment 1, Mage = 62.16 months) and a character learning task (Experiment 2, Mage = 63.96 months), using stimuli matched on visual complexity and frequency but differing in symmetry, and were assessed on Chinese word reading and word writing abilities twice with a 2-year interval.ResultsChildren were significantly more likely to endorse symmetrical complex stimuli as possible Chinese than asymmetrical complex ones, and they learned to read symmetrical characters significantly better than asymmetrical ones, reflecting their sensitivity to symmetry in Chinese characters. However, with age and nonverbal IQ statistically controlled, sensitivity to symmetry was not uniquely associated with Chinese word reading or word writing abilities at any time; rather, asymmetrical character learning, which necessitates reduced sensitivity to symmetry, was uniquely associated with Chinese word writing concurrently and longitudinally.DiscussionFindings highlight the close relationship between analytic perception of written words and early writing ability.

Effect of Step Size on the Formability of Al/Cu Bimetallic Sheets in Single Point Incremental Sheet Forming

Single Point Incremental Forming (SPIF) is an unconventional forming process that is suitable for prototype production and small lot production due to the economical tooling cost, short lead time, and the ability to create symmetrical and asymmetrical complex geometries without the use of expensive dies. This article presents the effect of the step size Δz of a forming tool made of 145Cr6 tool steel on the formability and maximum forming angle, mechanical properties, hardness, surface roughness, microstructure and texture of bimetallic Al/Cu sheets. Experiments were conducted at a constant rotational speed and feed rate, with the use of rapeseed oil as a lubricant. The tests were carried out with the use of a forming tool on both sides of the bimetallic sheet. The shape and dimensions of the formed elements are determined by non-contact optical 3D scanning. It has been proved that an increase in the step size Δz affects the deterioration of the surface quality of the specimens (an increase in the Ra parameter from 0.2 μm to approximately 3 μm for the step size of 1.2 mm), while a small step size down Δz favours the geometric stability of the samples. With increasing step size (at Δx = Δy = const.), the drawpiece wall continually thinned until the material fractured. Based on the results, it was shown that increasing the step size Δz over 1.1 mm causes cracking of the drawpieces. Furthermore, greater thinning of the Al/Cu sheet was observed in the range of step size Δz between 0.7 and 1.0 mm for aluminum side and step size Δz ≤ 0.6 mm and Δz ≥ 1.1 mm for copper side. It was also found that the mechanical properties of the bimetal sheet decreased as a result of incremental forming. The greatest decrease in strength and ductility was recorded for a pitch of 1.2 mm. Strength decreased from 230 MPa (for sheet in initial state) to approximately 80 MPa, elongation from 12% to approximately 8.5%, and hardness from 120 HV10 for Cu and 60 HV10 for Al to approximately 30 HV10 for both layers.

C–H⋯S Hydrogen Bond Assisted Supramolecular Encapsulation of Fullerenes with Nanobelts

C–H⋯S Hydrogen Bond Assisted Supramolecular Encapsulation of Fullerenes with Nanobelts

Solution Structure of the dATP-Inactivated Class I Ribonucleotide Reductase From Leeuwenhoekiella blandensis by SAXS and Cryo-Electron Microscopy.

The essential enzyme ribonucleotide reductase (RNR) is highly regulated both at the level of overall activity and substrate specificity. Studies of class I, aerobic RNRs have shown that overall activity is downregulated by the binding of dATP to a small domain known as the ATP-cone often found at the N-terminus of RNR subunits, causing oligomerization that prevents formation of a necessary α2β2 complex between the catalytic (α2) and radical generating (β2) subunits. In some relatively rare organisms with RNRs of the subclass NrdAi, the ATP-cone is found at the N-terminus of the β subunit rather than more commonly the α subunit. Binding of dATP to the ATP-cone in β results in formation of an unusual β4 tetramer. However, the structural basis for how the formation of the active complex is hindered by such oligomerization has not been studied. Here we analyse the low-resolution three-dimensional structures of the separate subunits of an RNR from subclass NrdAi, as well as the α4β4 octamer that forms in the presence of dATP. The results reveal a type of oligomer not previously seen for any class of RNR and suggest a mechanism for how binding of dATP to the ATP-cone switches off catalysis by sterically preventing formation of the asymmetrical α2β2 complex.

Advances in sleep-related hypermotor epilepsy

Sleep-related hypermotor epilepsy (SHE), formerly known as nocturnal frontal epilepsy, is characterized by asymmetrical tonic or complex hypermotor seizures during sleep, with transient, frequent and clustering attack. The accurate incidence is not known but somehow low, which is estimated about 1.8/100 000. The differential diagnosis between SHE and parasomnias may be challenging due to possible similarities between the two sleep-related manifestations. In a majority of patients, the etiology is unknown. Identified etiologies are heterogeneous and structural abnormalities,which are involved in the severity and prognosis of SHE. In terms of treatment, it mainly includes pharmacological therapy and surgery. Carbamazepine seems to be the drug of choice in SHE patients, and epilepsy surgery provides excellent results in selected drug-resistant SHE cases. This review will focus on diagnosis, pathogenesis, treatment and prognosis of SHE, aiming to promote its early diagnosis and appropriate treatment.

Synthesis, X‐Ray Structures, and Fluxional Properties of Symmetrical, Asymmetrical Binuclear and Cubane Type Copper(I) Complexes Bearing the Pyrrole‐Based P, N‐Hetero Donor Ligand

AbstractThe 1 : 1 reaction between 2‐(3,5‐dimethylpyrazolylmethyl)‐5‐(diphenylphosphinomethyl)pyrrole L and CuX (X=Cl, and Br) in THF afforded the symmetrical binuclear copper(I) complexes [Cu(μ‐X){μ‐C4H2NH‐2‐(CH2PPh2)‐5‐(CH2Me2pz)‐κ2P,N}]2, having one type of copper environment. When X=I, the asymmetrical complex having two copper environments was isolated, in addition to the symmetrical complex as crystals. Interestingly, the 1 : 2 ratio reaction between L and CuCl gave a distorted cubane type complex [Cu4Cl4{μ‐C4H2NH‐2‐(CH2PPh2)‐5‐(CH2Me2pz)‐κ2P,N}2], while the CuBr and CuI reactions did not give similar cubane complexes. Conversely, the 2 : 1 (L : Cu) ratio reactions using CuX (X=Cl, Br and I) in THF suggest the formation of four coordinate bis‐chelated copper(I) complex of the type [CuL2]+ in solution, in addition to the binuclear complexes. The X‐ray solid state structures of [CuL2X2] (X=Br and I) are retained in solution, in contrast to its chloride derivative giving two signals in 31P{1H} NMR spectrum. The formation of the binuclear complexes from [CuL2]+ and their equilibria were shown by variable temperature NMR, 31P{1H} 2D NOESY and HRMS studies. In addition, the reaction of L with [Cu(CH3CN)4]BF4 gave yet another binuclear complex [Cu2L2][BF4]2 which was characterized by spectroscopic methods. This study lends support for the hemilability of L.

High performance solution-processed green phosphorescent organic light-emitting diodes with high current efficiency and long-term stability

Highly efficient (D–π–A)-type host and green Ir(iii) complexes are introduced for solution-processed PHOLEDs that achieve high CE with considerably high EQE. The devices with symmetrical complex show more stable than those with asymmetrical complex.

Ligand-Induced Reassembly of GroEL/ES Chaperone In Vitro: Visualization by Electron Microscopy

The products of the reassembly reaction of tetradecameric two-ring quaternary structure of GroEL chaperonin under the pressure of its heptameric co-chaperonin GroES have been visualized by electron microscopy. It has been shown that one-ring heptameric oligomers of GroEL have been formed at the beginning (after ~5 min) of the reaction, while at the final stage of the reaction (after ~70 min), both one-ring heptamers in complex with one GroES and two-rings tetradecamers in complexes with one (asymmetrical complex) or two (symmetrical complex) GroES heptamers are present. The relationship between the data of light scattering, native electrophoresis, and electron microscopy obtained earlier has been discussed.

Construction of Asymmetrical Hexameric Biomimetic Motors with Continuous Single-Directional Motion by Sequential Coordination.

The significance of bionanomotors in nanotechnology is analogous to mechanical motors in daily life. Here the principle and approach for designing and constructing biomimetic nanomotors with continuous single-directional motion are reported. This bionanomotor is composed of a dodecameric protein channel, a six-pRNA ring, and an ATPase hexamer. Based on recent elucidations of the one-way revolving mechanisms of the phi29 double-stranded DNA (dsDNA) motor, various RNA and protein elements are designed and tested by single-molecule imaging and biochemical assays, with which the motor with active components has been constructed. The motor motion direction is controlled by three operation elements: (1) Asymmetrical ATPase with ATP-interacting domains for alternative DNA binding/pushing regulated by an arginine finger in a sequential action manner. The arginine finger bridges two adjacent ATPase subunits into a non-covalent dimer, resulting in an asymmetrical hexameric complex containing one dimer and four monomers. (2) The dsDNA translocation channel as a one-way valve. (3) The hexameric pRNA ring geared with left-/right-handed loops. Assessments of these constructs reveal that one inactive subunit of pRNA/ATPase is sufficient to completely block motor function (defined as K = 1), implying that these components work sequentially based on the principle of binomial distribution and Yang Hui's triangle.

Asymmetrical Macromolecular Complex Formation of Lysophosphatidic Acid Receptor 2 (LPA2) Mediates Gradient Sensing in Fibroblasts

Chemotactic migration of fibroblasts toward growth factors relies on their capacity to sense minute extracellular gradients and respond to spatially confined receptor-mediated signals. Currently, mechanisms underlying the gradient sensing of fibroblasts remain poorly understood. Using single-particle tracking methodology, we determined that a lysophosphatidic acid (LPA) gradient induces a spatiotemporally restricted decrease in the mobility of LPA receptor 2 (LPA2) on chemotactic fibroblasts. The onset of decreased LPA2 mobility correlates to the spatial recruitment and coupling to LPA2-interacting proteins that anchor the complex to the cytoskeleton. These localized PDZ motif-mediated macromolecular complexes of LPA2 trigger a Ca(2+) puff gradient that governs gradient sensing and directional migration in response to LPA. Disruption of the PDZ motif-mediated assembly of the macromolecular complex of LPA2 disorganizes the gradient of Ca(2+) puffs, disrupts gradient sensing, and reduces the directional migration of fibroblasts toward LPA. Our findings illustrate that the asymmetric macromolecular complex formation of chemoattractant receptors mediates gradient sensing and provides a new mechanistic basis for models to describe gradient sensing of fibroblasts.

Synthesis, structure, DNA interaction, and hydrolytic function toward bis(p-nitrophenyl) phosphate of a heterobinuclear macrocyclic complex

An asymmetrical bis-pyridine pendant-armed macrocyclic heterobinuclear complex, [ZnNiL](ClO4)2·CH3CN (H2L was derived from the condensation between 3,3′-((ethane-1,2-diylbis((pyridin-2-ylmethyl)azanediyl))bis(methylene))bis(2-hydroxy-5-methylbenzaldehyde) and 1.3-diaminopropane), has been synthesized and characterized by physico-chemical and spectroscopic methods. The asymmetric unit contains two complete macrocyclic complexes that are nevertheless quite similar to one another. The Zn–Ni separations, bridged by the two phenoxides, are 3.107 and 3.141 Ǻ, respectively. The phosphate hydrolysis catalyzed by the complex was investigated using bis(4-nitrophenyl)phosphate (BNPP) as the substrate. The catalytic rate constant (kcat) is 1.64 × 10−3 s−1 at pH 7.4 and 25 °C, which is 108-fold higher than that of the corresponding uncatalyzed reaction. The interaction between the complex and calf thymus (CT) DNA was investigated by UV–vis absorption, viscosity experiments, and cyclic voltammetry. The complex shows good binding propensity to calf thymus DNA via intercalation with a binding constant of 5 × 104 M−1. The agarose gel electrophoresis studies show that the complex has a concentration-dependent DNA cleavage activity.

Asymmetrical Diruthenium Complex Bridged by a Redox-Active Ligand

The asymmetrical dinuclear complex [(acac)(2)Ru1(μ-abpy)Ru2(Cym)Cl]PF(6) ([2]PF(6)), with acac(-) = acetylacetonato = 2,4-pentanedionato, abpy = 2,2'-azobis(pyridine), and Cym = p-cymene = 1-isopropyl-4-methylbenzene, has been obtained from the mononuclear precursors [Ru(acac)(2)(abpy)] and [Ru(Cym)Cl(2)](2). X-ray crystal structure analysis suggests the oxidation state formulation [(acac)(2)Ru1(III)(μ-abpy(•-))Ru2(II)(Cym)Cl](+) for 2(+), with antiferromagnetic coupling between one Ru(III) center and the radical-anion bridging ligand (abpy(•-)), based on the N-N distance of 1.352(3) Å. As appropriate references, the newly synthesized mononuclear [(abpy)Ru(II)(Cym)Cl]PF(6) ([1]PF(6)) with an unreduced N═N double bond at d(NN) = 1.269(4) Å and the symmetrical dinuclear [(acac)(2)Ru(2.5)(μ-abpy(•-))Ru(2.5)(acac)(2)] with d(NN) = 1.372(4) Å (rac isomer) support the above assignment for 2(+) as an asymmetrical mixed-valent configuration bridged by a radical ligand. Reversible one-electron oxidation leads to a dication, 2(2+), with largely metal-centered spin (EPR: g(1) = 2.207, g(2) = 2.155, and g(3) = 1.929), and a weak intervalence charge-transfer absorption at 1700 nm, as observed by spectroelectrochemistry. These results support a description of 2(2+) as [(acac)(2)Ru1(III)(μ-abpy(0))Ru2(II)(Cym)Cl](2+). Density functional theory (DFT) calculations suggest that the first reduction of [2]PF(6) also involves the bridging ligand, leading to [(acac)(2)Ru1(III)(μ-abpy(2-))Ru2(II)(Cym)Cl] (2). Experimentally, the first reduction of 2(+) is not fully reversible, with evidence for the loss of chloride to form [(acac)(2)Ru1(μ-abpy)Ru2(Cym)](+) (2a(+); g(1) = 2.454, g(2) = 2.032, and g(3) = 1.947). Further reduction produces [(acac)(2)Ru1(II)(μ-abpy(2-))Ru2(II)(Cym)] (2a), which forms [(acac)(2)Ru1(II)(μ-abpy(2-))Ru2(I)(Cym)](-)/[(acac)(2)Ru(II)(μ-abpy(•-))Ru(0)(Cym)](-) (2a(-)) in yet another one-electron step (g(1) = 2.052, g(2) = 2.008, and g(3) = 1.936). The major electronic transitions for each redox state have been assigned by time-dependent DFT calculations.

PEGylated N-methyl-S-methyl dithiocarbazate as a new reagent for the high-yield preparation of nitrido Tc-99m and Re-188 radiopharmaceuticals

A novel nitrido nitrogen atom donor for the preparation of (99m)Tc and (188)Re radiopharmaceuticals containing a metal-nitrogen multiple bond is presented. HO(2)C-PEG(600)-DTCZ was obtained by conjugation of N-methyl-S-methyl dithiocarbazate [H(2)N-N(CH(3))-C(S)SCH(3), HDTCZ] with polyethylene glycol 600 (PEG(600)). Asymmetrical heterocomplexes of the type [M(N)(PNP)(B)](0/+) (M=(99m)Tc, (188)Re; PNP=diphosphine ligands, B=DBODC, DEDC, NSH, H(2)OS, CysNAc, HDTCZ) and symmetrical nitride compounds of the type [M(N)(L)(2)] (L=DEDC, DPDC) have been prepared in high yield by using the newly designed nitride nitrogen atom donor HO(2)C-PEG(600)-DTCZ. A two-step procedure was applied for preparing the above symmetrical and asymmetrical complexes. The first step involved the preliminary formation of a mixture of nitride Tc-99m or Re-188 precursors, which contained the [M≡N](2+) core, through reduction of generator-eluted (99m)Tc-pertechnetate or (188)Re-perrhenate with thin (II) chloride in the presence of HO(2)C-PEG(600)-DTCZ. In the second step, the intermediate mixture was converted either in the final mixed asymmetrical complex by the simultaneous addition of diphosphine ligand and the suitable bidentate ligand B, or in the final symmetrical complex by the only addition of the bidentate ligand L. It was also demonstrated that the novel water-soluble nitride nitrogen atom donor HO(2)C-PEG(600)-DTCZ did not show coordinating properties toward the M≡N ((99m)Tc, (188)Re) core. Biodistribution studies in rats of the hitherto unreported [(99m)Tc(N)(PNP(3))DTCZ](+) and [(99m)Tc(N)(PNP(5))DTCZ](+) complexes showed that they selectively localize in the myocardium of rats with a favourable heart-to-lung and heart-to-liver uptake ratios. In particular, the heart-to-lung and heart-to-liver uptake ratios dramatically increased in the interval between 60 and 120 min postinjection. Hence, the combination of the favourable chemical and biological properties of HO(2)C-PEG(600)-DTCZ might confer to this novel compound an important role for the development of new (99m)Tc and (188)Re-nitrido radiopharmaceuticals.

Structure of Diethyl Phosphate Bound to the Binuclear Metal Center of Phosphotriesterase

The bacterial phosphotriesterase (PTE) from Pseudomonas diminuta catalyzes the hydrolysis of organophosphate esters at rates close to the diffusion limit. X-ray diffraction studies have shown that a binuclear metal center is positioned in the active site of PTE and that this complex is responsible for the activation of the nucleophilic water from solvent. In this paper, the three-dimensional structure of PTE was determined in the presence of the hydrolysis product, diethyl phosphate (DEP), and a product analogue, cacodylate. In the structure of the PTE-diethyl phosphate complex, the DEP product is found symmetrically bridging the two divalent cations. The DEP displaces the hydroxide from solvent that normally bridges the two divalent cations in structures determined in the presence or absence of substrate analogues. One of the phosphoryl oxygen atoms in the PTE-DEP complex is 2.0 A from the alpha-metal ion, while the other oxygen is 2.2 A from the beta-metal ion. The two metal ions are separated by a distance of 4.0 A. A similar structure is observed in the presence of cacodylate. Analogous complexes have previously been observed for the product complexes of isoaspartyl dipeptidase, d-aminoacylase, and dihydroorotase from the amidohydrolase superfamily of enzymes. The experimentally determined structure of the PTE-diethyl phosphate product complex is inconsistent with a recent proposal based upon quantum mechanical/molecular mechanical simulations which postulated the formation of an asymmetrical product complex bound exclusively to the beta-metal ion with a metal-metal separation of 5.3 A. This structure is also inconsistent with a chemical mechanism for substrate hydrolysis that utilizes the bridging hydroxide as a base to abstract a proton from a water molecule loosely associated with the alpha-metal ion. Density functional theory (DFT) calculations support a reaction mechanism that utilizes the bridging hydroxide as the direct nucleophile in the hydrolysis of organophosphate esters by PTE.

Evolving Concepts and Technologies in Mitral Valve Repair

Over the past few decades, it has become apparent that mitral valve repair is preferable to mitral valve replacement for the majority of patients undergoing surgery for mitral regurgitation (MR). The advantages of mitral valve repair include low rates of thromboembolism, resistance to endocarditis, excellent late durability reported for as long as 25 years, and no need for anticoagulation in the majority of patients.1–5 Because of these advantages of repair over replacement, the threshold for performing mitral valve repair has been lowered to include patients with MR who have early symptoms or even those who are asymptomatic, assuming that the chance of successful repair is ≥90% according to the latest American College of Cardiology/American Heart Association guidelines.6,7 Recently, surgeons have evaluated new techniques to further improve mitral valve repair, and cardiologists and surgeons are increasingly interested in the potential for percutaneous approaches to mitral valve repair.8 Myxomatous MR affects 1% to 2% of the population and therefore is a common pathology for mitral valve surgery, but the complexity of the operation may be difficult, which leads to generally low rates of repair. In a recent review, only 44.3% of patients in the United States who required mitral valve surgery for MR received a mitral valve repair,9 and in the Euro Heart Survey, repair rates were similarly low (46.5%).10 The goals of mitral repair are to maintain leaflet mobility, remodel the annulus, and allow normal coaptation of the anterior and posterior leaflets. Recent advances in techniques and new concepts for mitral repair are important to cardiologists and other clinicians interested in the management of patients with mitral valve disease. Accordingly, an improved understanding of these concepts will aid in the development of innovative techniques to create safe, durable, reliable, and reproducible mitral valve repair techniques, both …

Stability of Dissipative Solitons as Solutions of Asymmetrical Complex Cubic-quintic Ginzburg-Landau Equation

The existence and nonlinear dynamics of optical dissipative spatial solitons asym- metrical with respect to transverse coordinates are studied. Steady state solutions of asym- metrical complex cubic-quintic Ginzburg-Landau equation are computed using the variational approach extended in order to treat asymmetrical input. Using established stability criterion a domain of dissipative parameters for stable solitonic solutions is flxed. Analytical predictions are conflrmed by numerically simulated evolution of an asymmetrical input pulse towards a stable and robust dissipative soliton. DOI: 10.2529/PIERS060905192230

Study on Hydrodynamic Behavior of Large Droplet Levitated by Ultrasonic Wave

The containerless processing conducted by droplet levitation techniques makes it possible to manufacture new materials and conducts non-contact measurement of material properties under the microgravity condition. It is pointed out that surface deformation and internal flow of the large levitated droplet influence the containerless processing. There are few studies about surface deformation and internal flow of the large droplet levitated by the acoustic wave. In the present study, the characteristics of the surface deformation and the internal flow of the droplet levitated by the ultrasonic wave are investigated under the normal gravity condition and microgravity condition by using the aircraft. Under the microgravity condition, it is possible to levitate a larger and more spherical droplet in comparison with under the normal gravity condition. When the droplet surface oscillates in the second mode, the internal flow corresponding to the surface oscillation and the asymmetrical complex flow are observed.

Europium(III) Macrocyclic Complexes with Alcohol Pendant Groups as Chemical Exchange Saturation Transfer Agents

Paramagnetic lanthanide(III) complexes that contain hyperfine-shifted exchangeable protons offer considerable advantages over diamagnetic molecules as chemical exchange saturation transfer (CEST) agents for MRI. As part of a program to investigate avenues to improve the sensitivity of such agents, the CEST characteristics of europium(III) macrocyclic complexes having appended hydroxyethyl groups were investigated. The CEST spectrum of the asymmetrical complex, EuCNPHC3+, shows five distinct peaks for each magnetically nonequivalent exchangeable proton in the molecule. The CEST spectra of this complex were fitted to NMR Bloch theory to yield exchange rates between each of six exchanging proton pools (five on the agent plus bulk water). Exchange between the Eu3+-bound hydroxyl protons and bulk water protons was slow in dry acetonitrile but accelerated incrementally upon stepwise addition of water. In pure water, exchange was too fast to observe a CEST effect. The utility of this class of europium(III) complex for CEST imaging applications is ultimately limited by the small chemical shifts induced by the hydroxyl-appended ligands of this type and the resulting small Deltaomega values for the exchangeable hydroxyl protons.