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There is an association between hypocapnia and adverse neurodevelopmental outcome in infants with neonatal encephalopathy (NE). Our aim was to test the safety and feasibility of 5% CO2 and 95% air inhalation to correct hypocapnia in mechanically ventilated infants with NE undergoing therapeutic hypothermia. Ten infants were assigned to this open-label, single-center trial. The gas mixture of 5% CO2 and 95% air was administered through patient circuits if the temperature-corrected PCO2 ≤40 mm Hg. The CO2 inhalation was continued for 12 h or was stopped earlier if the base deficit (BD) level decreased 40 mm Hg, the lower value of the target range. Regression modeling revealed that BD and lactate had a tendency to decrease during the intervention (by 0.61 and 0.55 mmol/L/h, respectively), whereas pH remained stable. The rate of moderate disabilities and normal outcome was 50%. Our results suggest that inhaled 5% CO2 administration is a feasible and safe intervention for correcting hypocapnia.

Drug desensitization can be achieved successfully by gradual drug dose increases in different protocols. Most protocols are designed to obtain temporal tolerance. The data on long-term maintenance of drug tolerance is scarce. Based on an IgE-mediated colomycin allergy we describe the maintenance of drug tolerance to nebulized drug for the period of 10 years in a 15-year-old cystic fibrosis patient, proceeded by successful rush intravenous desensitization protocol. The mechanism of drug tolerance is largely speculative; however, long-term maintenance of it seems achievable by continuous local drug application.

Background Identification of early signs of hypoxic ischemic encephalopathy (HIE) with magnetic resonance imaging (MRI) has proven of prognostic significance. Yet, the importance of intracranial hemorrhage (ICH), being present concomitantly had not been investigated yet, despite the known influence of hypothermia on hemostasis. We aimed to determine whether presence of ICH on MRI alongside the signs of HIE have an impact on prognosis in neonates with the clinical diagnosis of HIE. Methods A retrospective study of consecutively sampled 108 asphyxiated term infants admitted to a tertiary neonatal intensive care unit (between 2007 and 2016), treated with whole body hypothermia and having brain MRI within 1 week of life was conducted. Presence or absence of HIE signs on MRI (basal ganglia-thalamus, watershed pattern and total brain injury) and on MR spectroscopy (lactate peak with decreased normal metabolites measured by Lac/NAA ratio) and/or of the five major types of ICH were recorded. Neurodevelopmental outcome was measured with Bayley Scales of Infant Development-II (BSID-II) test. Death or abnormal neurodevelopment (BSID-II score Results MRI and MR-spectroscopy (MRS) signs of HIE were present in 72% (n = 78). 36% (n = 39) of neonates had ICH, being mainly small in size. Chi-square test showed a relationship between neurodevelopmental outcome and initial MRI. Unadjusted logistic regression showed that neonates presenting MRI and MRS signs of HIE have 6.23 times higher odds for delayed mental development (OR = 6.2292; CI95% = [1.2642; 30.6934], p = 0.0246), than infants without imaging alterations; with no ICH effect on outcome. Adjustment for clinical and imaging parameters did not change the pattern of results, i.e. HIE remained an independent risk factor for delayed neurodevelopment (OR = 6.2496; CI95% = [1.2018; 32.4983], p = 0.0294), while ICH remained to have no significant effect. Conclusion HIE related MRI abnormalities proved to be important prognostic factors of poor outcome in cooled asphyxiated infants when present, suggesting that early MRI with MRS is beneficial for prognostication. Interestingly, ICHs present in about one third of all cases had no significant effect on neurodevelopmental outcome, despite the known hemostasis altering effects of hypothermia.

The ATP-binding cassette (ABC) transporter MsbA is an ATP-driven lipid-A flippase. It belongs to the ABC protein superfamily whose members are characterized by conserved motifs in their nucleotide binding domains (NBDs), which are responsible for ATP hydrolysis. Recently, it was found that MsbA could catalyze a reverse adenylate kinase (rAK)-like reaction in addition to ATP hydrolysis. Both reactions are connected and mediated by the same conserved NBD domains. Here, the structural foundations underlying the nucleotide binding to MsbA were therefore explored using a concerted approach based on conventional- and DNP-enhanced solid-state NMR, pulsed-EPR, and MD simulations. MsbA reconstituted into lipid bilayers was trapped in various catalytic states corresponding to intermediates of the coupled ATPase-rAK mechanism. The analysis of nucleotide-binding dependent chemical shift changes, and the detection of through-space contacts between bound nucleotides and MsbA within these states provides evidence for an additional nucleotide-binding site in close proximity to the Q-loop and the His-Switch. By replacing Mg

To develop an evidence-based, standardized structured reporting (SR) method for brain MRI examinations in neonatal hypoxic-ischemic encephalopathy (HIE) suitable both for clinical and research use.SR template development was based on comprehensive review of the pertinent literature with the basic sections and subdivisions of the template defined according to MRI sequences (both conventional and diffusion-weighted, MR-spectroscopy (MRS), and T2*-weighted imaging), and the items targeted on age-related imaging patterns of HIE. In order to evaluate the usability of the proposed SR template we compared data obtained from the brain MR image analysis of 87 term and 19 preterm neonates with the literature. The enrolled 106 infants were born between 2013 and 2015, went through therapeutic hypothermia according to the TOBY criteria due to moderate to severe asphyxia and had at least one brain MRI examination within the first two weeks of life. Ethical approval was obtained for this retrospective study. Descriptive statistical analysis was also performed on data exported from the structured reporting system as feasibility test.The mean gestational age of the study population was 38.3±2.2 weeks; brain MRI was performed on 5.8±2.9 day of life, hence in 78% of our patients after the conclusion of therapeutic hypothermia. Our main imaging findings were concordant to the pertinent literature. Moreover, we identified a characteristic temporal evolution of diffusion changes. Interestingly 18% (n=19/106) of the clinically asphyxiated infants had isolated axial-extraaxial haemorrhage without any imaging sign of HIE.In this article our approach of reporting HIE cases with our novel SR template is described. The SR template was found suitable for reporting HIE cases, moreover it uncovered time and location dependent evolution of diffusion abnormalities (and pseudonormalization, as well), suggesting its usefulness in clinical research applications. The high number of isolated intracranial haemorrhages, and the changing diffusion pattern emphasizes the importance of early imaging in HIE.Célunk klinikai és kutatási célokra egyaránt használható, bizonyítékon alapuló, standardizált, strukturált koponya-MR-leletezési rendszer kidolgozása volt neonatalis hypoxiás-ischaemiás encephalopathia (HIE) leletezésére.A strukturált MR-leletező rendszer tervezése az irodalmi adatok széles körű áttekintésén alapult. A leletező rendszer fastruktúrája részben az „asphyxia MR-protokoll” alapján épül fel, mely T1- és T2-súlyozott, hemosziderin-érzékeny (T2* vagy SWI), illetve diffúziósúlyozott szekvenciákból, valamint MR-spektroszkópiás (MRS) mérésekből áll. A rendszer további alcsoportjai a HIE ra-diológiai megjelenésén alapulnak, így akár részletekbe menően karakterizálható a HIE-re jellegzetes perifériás és a basalis ganglion-thalamus mintázat, illetve a traumás szülés kapcsán kialakuló, a HIE-hez gyakran társuló intracranialis vérzés. A rendszer tervezése és tesztelése kapcsán, etikai engedélyünk birtokában, a TOBY-kritériumok alapján 2013-2015 között közepes vagy súlyos apshyxiával diagnosztizált, hypothermiával kezelt és az első két élethétben legalább egy MR-vizsgálaton átesett 106 kora- és érett újszülött koponya-MR-leleteit rögzítettük retrospektív adatbázisunkban, majd az adatokat leíró statisztikai mód-szerekkel elemeztük.A vizsgálatban szereplő betegek átlagosan a 38,3±2,2 gestatiós héten születtek; a koponya-MR-vizsgálat az esetek 78%-ában a terápiás hypothermiát követően, átlagosan az 5,8±2,9 életnapon történt. Az MR-vizsgálatok leletezése során lényegében az irodalmi adatokkal megegyező eltéréseket azonosítottunk, ráadásul megfigyeltük a diffúziós eltérések érdekes időbeli változását is. Az MR-vizsgálatok és klinikai adatok összevetésénél azt tapasztaltuk, hogy a hűtött, klinikailag asphyxiásnak tartott újszülöttek 18%-ánál (n=19/106) a HIE MR-jelei hiányoztak, viszont izolált állomány- vagy extraaxialis vérzés volt kimutatható.Közleményünk a strukturált MR-leletezés újfajta megközelítését mutatja be, mely a tesztelés során alkalmasnak bizonyult az újszülöttkori koponya-MR-leletek pontos és szükség szerint részletekbe menő rögzítésére. A tesztelés során végzett adatelemzés érdekes eredményeket mutatott, mint például a diffúziós eltérések evolúciója (pszeudonormalizációval egyetemben). Az izolált intracranialis vérzések magas száma, illetve a diffúziós mintázat időbeli változása kiemeli a korai képalkotás jelentőségét HIE-ben.

The UV light absorbing species of proteorhodopsin with deprotonated Schiff base retinal was investigated using steady-state fluorescence and femtosecond pump-probe spectroscopy. Compared to the all-trans retinal with protonated Schiff base, the deprotonated chromophore absorbs at 365 nm and exhibits a blue-shifted fluorescence spectrum. The unusually long-lived excited state decays bi-exponentially with time constants of 8 ps and 130 ps to form a deprotonated 13-cis retinal as the primary photo-product.

Escherichia coli EmrE, a homodimeric multidrug antiporter, has been suggested to offer a convenient paradigm for secondary transporters due to its small size. It contains four transmembrane helices and forms a functional dimer. We have probed the specific binding of substrates TPP(+) and MTP(+) to EmrE reconstituted into 1,2-dimyristoyl-sn-glycero-3-phosphocholine liposomes by (31)P MAS NMR. Our NMR data show that both substrates occupy the same binding pocket but also indicate some degree of heterogeneity of the bound ligand population, reflecting the promiscuous nature of ligand binding by multidrug efflux pumps. Direct interaction between (13)C-labeled TPP(+) and key residues within the EmrE dimer has been probed by through-space (13)C-(13)C correlation spectroscopy. This was made possible by the use of solid-state NMR enhanced by dynamic nuclear polarization (DNP) through which a 19-fold signal enhancement was achieved. Our data provide clear evidence for the long assumed direct interaction between substrates such as TPP(+) and the essential residue E14 in transmembrane helix 1. Our work also demonstrates the power of DNP-enhanced solid-state NMR at low temperatures for the study for secondary transporters, which are highly challenging for conventional NMR detection.

The paper deals with the application of thermodynamic description of metal–ligand interactions in biological systems, when the determination of the actual chemical form of a metal ion or a metal compound with potential biological activity in biological fluids or tissues can help in the identification of the relevant active form of the metallic drug or in the exploration of its pharmacokinetics. Two groups of metal compounds are discussed in the paper: the fate of vanadium and zinc containing antidiabetics during their transport in the blood stream, and the application of metal ion chelators to control synaptic Cu(II) and Zn(II) level in order to hinder oligomerisation of β-amyloids in Alzheimer's disease.

Efforts to delineate the interactions of Al(III), a known metallotoxin, with low molecular mass physiological substrates involved in cellular processes led to the investigation of the structural speciation of the binary Al(III)–quinic acid system. Reaction of Al(NO3)3 · 9H2O with d -(−)-quinic acid at a specific pH (4.0) afforded a colorless crystalline material K[Al(C7H11O6)3] · (OH) · 4H2O (1). Complex 1 was characterized by elemental analysis, FT-IR, DSC–TGA, 13C-MAS NMR, solution 1H and 13C NMR, and X-ray crystallography. The structure of 1 reveals a mononuclear octahedral complex of Al(III) with three singly ionized quinate ligands bound to it. The three ligand alcoholic side chains do not participate in metal binding and dangle away from the complex. The concurrent study of the aqueous speciation of the binary Al(III)–quinic acid system projects a number of species complementing the synthetic studies on the binary system Al(III)–quinic acid. The structural and spectroscopic data of 1 in the solid state and in solution emphasize its physicochemical properties emanating from the projections of the aqueous structural speciation scheme of the Al(III)–quinic acid system. The employed pH-specific synthetic work (a) exemplifies essential structural and chemical attributes of soluble aqueous species, arising from biologically relevant interactions of Al(III) with natural α-hydroxycarboxylate substrates, and (b) provides a potential linkage to the chemical reactivity of Al(III) toward O-containing molecular targets influencing physiological processes and/or toxicity events.

The interactions of Al(III) with the dipeptide AspAsp and the tripeptide AspAspAsp in aqueous solutions were studied by pH-potentiometry and multinuclear 1H- and 13C- nuclear magnetic resonance (NMR) spectroscopy. Their numerous negatively charged COO(-) functions allow these ligands to bind Al(III) even in weakly acidic solutions. Various mononuclear 1:1 complexes are formed in different protonation states. 13C-NMR spectroscopy unambiguously proved participation of the COO(-) functions in a monodentate or chelating mode in Al(III) binding, however, the terminal-NH(2) group seems to be excluded from the coordination. Depending on the metal ion to ligand ratio precipitation occurs at pH approximately 5 to 6. This indicates that the COO(-) groups at the low level of preorganization in such small peptides are not sufficient to keep the Al(III) ion in solution and to prevent the precipitation of Al(OH)(3) at physiological pH. To achieve this, a more specific arrangement of the side-chain donors seems necessary.

ATP binding cassette (ABC) transporters form a superfamily of integral membrane proteins involved in translocation of substrates across the membrane driven by ATP hydrolysis. Despite available crystal structures and extensive biochemical data, many open questions regarding their transport mechanisms remain. Therefore, there is a need to explore spectroscopic techniques such as solid state NMR in order to bridge the gap between structural and mechanistic data. In this study, we investigate the feasibility of using Escherichia coli MsbA as a model ABC transporter for solid state NMR studies. We show that optimised solubilisation and reconstitution procedures enable preparing stable and homogenous protein samples. Depending on the duration of solubilisation, MsbA can be obtained in either an apo- or in a native lipid A bound form. Building onto these optimisations, the first promising MAS-NMR spectra with narrow lines have been recorded. However, further sensitivity improvements are required so that complex NMR experiments can be recorded within a reasonable amount of time. We therefore demonstrate the usability of paramagnetic doping for rapid data acquisition and explore dynamic nuclear polarisation as a method for general signal enhancement. Our results demonstrate that solid state NMR provides an opportunity to address important biological questions related to complex mechanisms of ABC transporters.

Complexes formed with low molecular mass biomolecules are the ‘dynamic or mobile units’ of Al(III), which may be involved in the absorption and transport processes of this toxic element in organisms. This paper reviews the interactions of Al(III), from speciation and structural aspects, with biologically relevant endogenous and exogenous small biomolecules such as inorganic ligands (hydroxide, fluoride, (oligo)phosphates and silicic acid), amino acids, phosphorylated amino acids, oligopeptides, biophosphates including nucleotides, phosphonates, hydroxamates, and aromatic and aliphatic hydroxycarboxylates. The importance of time in biospeciation is demonstrated on the examples of binary and ternary systems involving Al(III) and citric acid. Examples are also given for the implications of the speciation of Al(III) with such small biomolecules in biology.

The solution state of the neurotoxic Al(III) in biological systems is discussed briefly, and the importance of the Al(III)–peptide and Al(III)–protein interactions in the various neurodegeneration processes is emphasised and evaluated. The possible involvement of Al(III) in the formation of Alzheimer's disease marker senile plaques and neurofilament tangles is discussed in light of the solution speciation of the Al(III)–AcLysSerProValValGluGly system and the structural features of the complexes formed.

Potentiometric, 1H, 31P NMR spectroscopic and X-ray studies were carried out to investigate the complex formation of Al(III) with iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), their mixed carboxylic–phosphonic and purely phosphonic derivatives. The stability constants of the complexes formed were determined at 25 °C and at 0.2 mol dm−3 ionic strength (KCl). It was found that substitution of CO2− by PO32− increases the overall stability of the complexes, due to the higher basicity of the phosphonic groups. However, the higher spatial requirement of the phosphonic moiety and the greater electrostatic repulsion between the dinegatively charged PO32− moieties overcompensate this effect, resulting in a somewhat weaker metal binding capacity for the phosphonic derivatives. According to the 1H NMR spectra of Al(III) complexes of IDA, complex formation renders the two protons of each CH2 group inequivalent, while the CH2 groups of NTA and its derivatives remain chemically and magnetically equivalent in their Al(III) complexes. As no symmetrical arrangements of the donor atoms in their Al(III) complexes can be expected with most of the ligands, the rate of intramolecular rearrangement motions of the binding functional groups seems to be different for the IDA and the NTA derivatives.

Proteorhodopsins (PRs) found in marine microbes are the most abundant retinal-based photoreceptors on this planet. PR variants show high levels of environmental adaptation, as their colors are tuned to the optimal wavelength of available light. The two major green and blue subfamilies can be interconverted through a L/Q point mutation at position 105. Here we reveal the structural basis behind this intriguing color-tuning effect. High-field solid-state NMR spectroscopy was used to visualize structural changes within green PR directly within the lipid bilayer upon introduction of the green-blue L105Q mutation. The observed effects are localized within the binding pocket and close to retinal carbons C14 and C15. Subsequently, magic-angle spinning (MAS) NMR spectroscopy with sensitivity enhancement by dynamic nuclear polarization (DNP) was applied to determine precisely the retinal structure around C14-C15. Upon mutation, a significantly stretched C14-C15 bond, deshielding of C15, and a slight alteration of the retinal chain's out-of-plane twist was observed. The L105Q blue switch therefore acts locally on the retinal itself and induces a conjugation defect between the isomerization region and the imine linkage. Consequently, the S0-S1 energy gap increases, resulting in the observed blue shift. The distortion of the chromophore structure also offers an explanation for the elongated primary reaction detected by pump-probe spectroscopy, while chemical shift perturbations within the protein can be linked to the elongation of late-photocycle intermediates studied by flash photolysis. Besides resolving a long-standing problem, this study also demonstrates that the combination of data obtained from high-field and DNP-enhanced MAS NMR spectroscopy together with time-resolved optical spectroscopy enables powerful synergies for in-depth functional studies of membrane proteins.

Time-dependent speciation studies have been carried out on the ternary AlIII−citrate (A)−phosphate (B) system in order to clarify the solution state of AlIII in blood serum. The potentiometric results indicate that ternary complexes predominate both in freshly prepared mixtures and at equilibrium. The ternary species AlAB and AlABH−1 and the binary species AlAH−1 and AlBH−1 are present at physiological pH. As the solution ages the amount of the trinuclear species [Al3(AH−1)3(OH)]4− increases at the expense of the mononuclear binary and ternary complexes. 31P NMR spectra measured at neutral pH provide corroborating evidence of the formation of the ternary complexes AlAB and AlABH−1 and binary species AlBH−1 and Al2BH−3 found potentiometrically. Time-dependent 1H NMR measurements show that monodentate phosphate can slowly displace citrate from the otherwise very stable structure of the trinuclear species [Al3(AH−1)3(OH)]4−. At blood serum concentrations [c(AlIII) = 3 μM], AlIII is mostly bound to citrate either in binary species or in the ternary species formed with phosphate. However, with increasing AlIII concentrations binding to phosphate becomes more important.

Time-dependent potentiometric and NMR spectroscopic measurements were carried out in the AlIII−citric acid system in an equimolar solution and at an excess of ligand in order to monitor the changes in speciation as a function of time. In fresh solutions, the mononuclear 1:1 species [AlLH]+, [AlL], [AlLH−1]− and [AlLH−2]2− and the 1:2 complexes [AlL2]3−, [AlL2H−1]4− and [AlL2H−2]5− are formed. In agreement with earlier findings (Inorg. Chem. 1988, 27, 2565), these complexes are converted to a large extent into a thermodynamically more stable trinuclear species as the solutions age. Depending on the composition of the initially formed mononuclear species, the formation of the trinuclear species is accompanied either by the consumption or by the liberation of hydroxide ions. NMR spectroscopy was used to confirm the considerable time dependence of the species distribution. The 1H, 27Al and 13C NMR spectra indicated that at equilibrium the trinuclear species [Al3(LH−1)3(OH)]4− predominates in the pH range 4−7. Oligomerization of the mononuclear species takes place through at least one intermediate complex. At equilibrium, the ligand-exchange reactions between the trinuclear species, the mononuclear species and free citrate are slow on the NMR time scale.

The speciation of the toxic Al(III) and the beneficial VO(IV) in various biofluids and tissues is discussed in order to describe the solution state of these metal ions in the organism. The importance of ternary complex formation with relevant biomolecules is emphasized. The interactions of Al(III) and VO(IV) with oligopeptides are also dealt with. The importance of the biospeciation of Al(III) ion in its transport and involvement in neurological disorders, and of insulin mimetic VO(IV) complexes is discussed.

In order to assess the Al(III)-binding abilities of phosphorylated proteins and peptides, the interactions of Al(III) with the building blocks O-phosphoserine (PSer) and O-phosphotyrosine (PTyr) were studied. pH-metric and 31 P NMR measurements were carried out to determine the stoichiometries and stability constants of the complexes formed, and to establish the most probable binding sites of the metal ion. PSer was found to bind Al(III) in a monodentate manner at the phosphate moiety, and in a tridentate manner with the simultaneous coordination of all donor groups. PTyr binds Al(III) only at the separate phosphate function. Citric acid (Cit) proved to be a stronger Al(III) binder at the physiological pH, though, it was able to displace PSer only in a rather slow process through formation of the trinuclear species Al 3 (Cit) 3 (OH). The results were used to evaluate the potential role of Al(III) in inducing the formation of neurofilamentous aggregates in neurological disorders.

Solid-state NMR is an established method for biophysical studies of membrane proteins within the lipid bilayers and an emerging technique for structural biology in general. In particular magic angle sample spinning has been found to be very useful for the investigation of large membrane proteins and their interaction with small molecules within the lipid bilayer. Using a number of examples, we illustrate and discuss in this chapter, which information can be gained and which experimental parameters need to be considered when planning such experiments. We focus especially on the interaction of diffusive ligands with membrane proteins.

Two histidine-rich branched peptides with one lysine as a branching unit have been designed and synthesized by solid-phase peptide synthesis. Their complex formation with Cu(II) and Zn(II) as well as their ability to attenuate the metal-ion induced amyloid aggregation has been characterized. Both peptides can keep Cu(II) and Zn(II) in complexed forms at pH 7.4 and can bind two equivalents of metal ions in solutions with excess metal. The stoichiometry, stability and structure of the complexes formed have been determined by pH potentiometry, UV-Vis spectrophotometry, circular dichroism, EPR and NMR spectroscopy and ESI-MS. Both mono- and bimetallic species have been detected over the whole pH range studied. The basic binding mode is either a tridentate {N(amino), N(amide), N(im)} or a histamine-type of coordination which is complemented by the binding of far imidazole or amino groups leading to macrochelate formation. The peptides were able to prevent Cu(II)-induced Aβ(1-40) aggregation but could not effectively compete for Zn(II) in vitro. Our results suggest that branched peptides containing potential metal-binding sites may be suitable metal chelators for reducing the risk of amyloid plaque formation in Alzheimer's disease.

Nimustine hydrochloride [systematic name: 4-amino-5-({[N-(2-chloroethyl)-N-nitrosocarbamoyl]amino}methyl)-2-methylpyrimidin-1-ium chloride], C9H14ClN6O2+·Cl−, is a prodrug of CENU (chloroethylnitrosourea) and is used as a cytostatic agent in cancer therapy. Its crystal structure was determined from laboratory X-ray powder diffraction data. The protonation at an N atom of the pyrimidine ring was established by solid-state NMR spectroscopy.

Two pyridine derivatives, DMAP and ENDIP, have been investigated as possible metal chelators in the therapy of Alzheimer's disease. Their complex formation with Cu(ii) and Zn(ii) were characterised in detail. In the case of ENDIP a high stability tetradentate ML complex is formed at physiological pH both with Cu(ii) and Zn(ii). DMAP was found to be a weaker metal binder. At physiological pH, it forms a bidentate ML complex with Zn(ii) and MLH(-1) and ML(2) complexes with Cu(ii), depending on the metal ion to ligand ratio. Fluorescence spectroscopy and dynamic light scattering measurements proved that ENDIP effectively competes with aggregated amyloid-beta peptides (Abeta) for both Cu(ii) and Zn(ii) and thus is able to prevent the metal ion-induced amyloid aggregation and to resolubilise amyloid precipitates.

The aqueous solutions of arsenous acid with the meso and racemic forms of 1,4-dithiol-butane-2,3-diol, namely, dithioerythritol (dte) and dithiothreitol (dtt), respectively, were titrated pH-metrically in different molar ratios. The p K a values determined for As(OH) 3, and dtt were in good accordance with the literature data, and we determined for the first time the p K a value of dte. The deprotonation steps of both M (As(OH) 3 considered as a central metal ion) and H 2L components dte and dtt (considered as ligands) appeared at a higher pH in the titration curves of the ternary systems (M, H 2L, H (+)) than in the individual component. This unusual observation is explained by the condensation reactions between the reagents taking place in the pH8 range. In the solutions of c As(III)5.10 (-3) M, the precipitate formed upon mixing the arsenous acid and H 2L solutions in neutral medium, and the formation of the precipitate shifted toward acidic pH on the increase of the total concentrations. This indicated that pH-metry can follow the reactions only in an indirect way. Useful, but not satisfactory, information can be obtained by means of this method alone. Combined with NMR and UV spectroscopic measurements it is revealed that depending on the As(III)/H 2L molar ratio, different complexes form in the solutions. In the species with 1:2 composition, one of the ligands is strongly bound to the arsenic(III) probably via its two thiolate, while the second one is attached only weakly. The crystal structure of an As(III)-dte crystal of 1:1 composition, grown from ethanolic solution, shows that As(III) binds the ligand through its three p-orbitals in a manner similar to that expected in aqueous solution. While the uptake of the second ligand cannot be detected by pH-metry, the decomposition of thioether bonds above pH approximately 10 is confirmed by the change in UV spectra at approximately 265 nm to be a base-consuming process. In such alkaline solutions, most probably, rearrangement of the bonding scheme occurs, resulting in ligands being bound to the arsenic(III) through the oxygen donor atoms.

The complexation of Al(III) with d -gluconic acid was studied in solution by means of pH-potentiometry, ESI mass spectrometry and one- and two-dimensional NMR spectroscopy. Six complexes were found to form in solution from pH 2 to 10: [AlL]2+, [AlLH−1]+, [AlLH−2], [AlLH−3]−, [AlL2H−1] and [AlL2H−2]−. NMR spectroscopy indicated very complicated chemical exchange processes between the free ligand and gluconic acid molecules bound in the metal complexes, with different coordination modes resulting in changes both of the chemical shift and of the line shape of the signals. A solid complex [AlL2H−1] · 2H2O was isolated as a microcrystalline powder and characterized. The structures of the complexes are discussed on the basis of the spectroscopic results and MM force field calculations.

Ternary complex formation of some potent insulin-mimetic zinc(II) complexes of bidentate ligands: maltol and 3-hydroxy-1,2-dimethyl-pyridinone with (O,O), 2-picolinic acid and 6-methylpicolinic acid with (N,O) and the tridentate 2,6-dipicolinic acid with (O,N,O) coordination modes was studied in aqueous solutions by pH-potentiometry and spectroscopic (UV, CD, ESI-MS) methods in the presence of critical cell constituents such as L-glutathione reduced (GSH) and adenosine 5'-triphosphate (ATP). Results showed that formation of the ternary complexes was hindered in the case of 2,6-dipicolinic acid, especially with ATP, while it was favoured with the bidentate ligands in the physiological pH range. Driving force of the formation of mixed-ligand species was found to be a more enhanced coordination of GSH and ATP as second ligands in the ternary complexes than in their binary ones due to steric and electrostatic reasons. The mitochondrial dehydrogenase activity of the zinc(II) complexes, as an indirect indicator for the glucose intake, was measured on Mono Mac and 3T3-L1 adipocyte cell lines. The activity of the complexes up to approximately 10-100 microM concentration was in the range of the effect of 0.75-1.5 microM insulin, while at higher concentration it was broken down due to the sensitivity of the cells to toxicity of the complexes.

The underlying cause of Alzheimer's disease (AD) is thought to be the beta-amyloid aggregates formed mainly by Abeta1-42 peptide. Protective pentapeptides [e.g., Leu-Pro-Phe-Phe-Asp (LPFFD)] have been shown to prevent neuronal toxicity of Abeta1-42 by arresting and reversing fibril formation. Here we report that an endogenous tetrapeptide, endomorphin-2 (End-2, amino acid sequence: YPFF), defends against Abeta1-42 induced neuromodulatory effects at the cellular level. Although End-2 does not interfere with the kinetics of Abeta fibrillogenesis according to transmission electron microscopic studies and quasielastic light scattering measurements, it binds to Abeta1-42 during aggregation, as revealed by tritium-labeled End-2 binding assay and circular dichroism measurements. The tetrapeptide attenuates the inhibitory effect on cellular redox activity of Abeta1-42 in a dose-dependent manner, as measured by 3-(4,5-dimethylthiazolyl-2)-2,-5-diphenyltetrazolium bromide (MTT) assay. In vitro and in vivo electrophysiological experiments show that End-2 also protects against the field excitatory postsynaptic potential attenuating and the NMDA-evoked response-enhancing effect of Abeta1-42. Studies using [D-Ala (2), N-Me-Phe (4), Gly (5)-ol]-enkephalin (DAMGO), a mu-opioid receptor agonist, show that the protective effects of the tetrapeptide are not mu-receptor modulated. The endogenous tetrapeptide End-2 may serve as a lead compound for the drug development in the treatment of AD.

The Al(III)-binding abilities of two aldaric acids, D-saccharic acid and mucic acid (the neutral form is denoted as H(2)L), were studied in solution by means of pH potentiometric, (1)H and (13)C NMR, and ESI-MS techniques. The most probable conformations and isomeric binding modes of the complexes formed in solution were determined by density functional theory (DFT) calculations. A solid D-saccharic acid complex K(2)[[Al(LH(-2))(H(2)O)](2)].H(2)O was isolated and crystallographically characterised. The two alcoholic hydroxy groups alpha to the terminal COO(-) groups were found to take part in the coordination, but in different ways. One of them coordinates in a bridging mode. Detailed ESI-MS and NMR studies proved that the complex retains its structure in solution. However, depending on the ligand and the pH, such complexes may exist in two isomeric forms. DFT calculations on the ion [[Al(LH(-2))(H(2)O)](2)](2-) revealed that several orbitals participate in stabilizing the dimeric arrangement.

The chemistry of aluminum was explored in the presence of the physiological ligand citric acid and in low-pH aqueous media. As a result, the first dinuclear aluminum-citrate complex (NH4)4[Al2-(C6H4O7)(C6H5O7)2].4H2O was isolated at low pH (approximately 3.5), and was characterized by FT-IR spectroscopy and X-ray crystallography. The structural analysis reveals the presence of a dinuclear assembly of two aluminum ions octahedrally coordinated to three citrate ligands of differing protonation state. The NMR solution behavior of this complex emphasizes its time-dependent transformation into a number of variable nature species, ultimately leading to the thermodynamically stable trinuclear species. It also establishes the participation of the dinuclear complex as a viable component of the aqueous Al(III)-citrate speciation. The chemical and structural features of this novel low molecular mass species provide considerable insight into citrate's ability, as a natural ligand, to influence the chemistry of aluminum in a pH-dependent fashion, and potentially affect aluminum's (bio)distribution, absorption, accumulation, and biotoxicity at sensitive biological sites.

A 57-year-old man with a history of chronic alcoholism was evaluated for seizures. MRI showed severe diffuse atrophy of the corpus callosum (CC). Clinical examination revealed bimanual coordination difficulties, left ideomotor apraxia, and tactile anomia. The genu and the splenium had central cystic degeneration, with sparing of the peripheral layers. Tractography showed the lack of central white matter tracts, an “acquired callosotomy” (figure). The imaging findings were compatible with the chronic phase of Marchiafava-Bignami disease, a rare demyelinating disorder, primarily affecting the central CC layers, thought to be due to chronic alcohol consumption.1,2

Reactions of Al(III) and Ga(III) with citric acid in aqueous solutions, yielded the complexes (NH(4))(5)[M(C(6)H(4)O(7))(2)].2H(2)O (M(III) = Al (1), Ga (2)) at alkaline pH, and the complexes (Cat)(4)[M(C(6)H(5)O(7))(C(6)H(4)O(7))].nH(2)O (M(III) = Al (3), Ga (4), Cat. = NH(4)(+), n = 3; M(III) = Al (5), Ga (6), Cat. = K(+), n = 4) at acidic pH. All compounds were characterized by spectroscopic (FT-IR, (1)H, (13)C, and (27)Al NMR, (13)C-MAS NMR) and X-ray techniques. Complex 1 crystallizes in space group P1, with a = 9.638(5) A, b = 9.715(5) A, c = 7.237(4) A, alpha = 90.96(1) degrees, beta = 105.72(1) degrees, gamma = 119.74(1) degrees, V = 557.1(3) A(3), and Z = 1. Complex 2 crystallizes in space group P1, with a = 9.659(6) A, b = 9.762(7) A, c = 7.258(5) A, alpha = 90.95(2) degrees, beta = 105.86(2) degrees, gamma = 119.28(1) degrees, V = 564.9(7) A(3), and Z = 1. Complex 3 crystallizes in space group I2/a, with a = 19.347(3) A, b = 9.857(1) A, c = 23.412(4) A, beta = 100.549(5) degrees, V = 4389(1) A(3), and Z = 8. Complex 4 crystallizes in space group I2/a, with a = 19.275(1) A, b = 9.9697(6) A, c = 23.476(1) A, beta = 100.694(2) degrees, V = 4432.8(5) A(3), and Z = 8. Complex 5 crystallizes in space group P1, with a = 7.316(1) A, b = 9.454(2) A, c = 9.569(2) A, alpha = 64.218(4) degrees, beta = 69.872(3) degrees, gamma = 69.985(4) degrees, V = 544.9(2) A(3), and Z = 1. Complex 6 crystallizes in space group P1, with a = 7.3242(2) A, b = 9.4363(5) A, c = 9.6435(5) A, alpha = 63.751(2) degrees, beta = 70.091(2) degrees, gamma = 69.941(2) degrees, V = 547.22(4) A(3), and Z = 1. The crystal structures of 1-6 reveal mononuclear octahedral complexes of Al(III) (or Ga(III)) bound to two citrates. Solution NMR, on both 4- and 5- species, reveals rapid intramolecular exchange of the bound and unbound terminal carboxylates. Upon dissolution in water, the complexes, through a complicated reaction cascade, transform to oligonuclear 1:1 species that, in agreement with previous studies, represent the thermodynamically stable state in solution. The data provide, for the first time, structural details of low MW, mononuclear complexes of Al(III) (or Ga(III)) with citrate that are dictated, among other factors, by pH. The properties of 1-6 may provide clues relevant to their biological association with humans.

For a long time aluminium was considered to be an innocuous element for humans, in large part because of the very low intestinal uptake of Al from the diet. It is now clear that Al is an important toxicant in plants, experimental animals and humans [1]. The increase in the Al exposure of the population becomes of greater concern in light of a series of studies which shows an increased risk of various neurological disorders, including Alzheimer’s disease (AD) and other skeletal and hematological disorders, associated with elevated Al levels in body fluids and tissues [1–5].

Complex formation between Al III and various bidentate and potentially tridentate amino acids (Gly, Ser, Thr, Gln, Asn, Glu and Asp) and some model compounds (N-acetylaspartic acid, succinic acid, and 2-sulfanylsuccinic acid) was studied in aqueous solution by pH-potentiometric and multinuclear ( 1 H, 13 C and 27 Al) NMR techniques. A weak interaction through the carboxylate function was unambiguously detected for all of these ligands. For Asp, however, which contains two carboxylates and a central amino donor, tridentate co-ordination is strongly suggested. Although its steric environment is similar to that of the amino function in Asp, binding of the thiolate sulfur of 2-sulfanylsuccinic acid could not be verified.

In recent years, an international project Hydrological cycle in Mediterranean Experiment (HyMeX) was launched to achieve a better general understanding of natural water cycle and improve hydrometeorological forecasts. Reasons for launching the Hymex project lie in the fact that the Mediterranean is one of hot spots for regional climate change. The Mediterranean area also concentrates the major natural risks related to the water cycle, including heavy precipitation and flash-flooding during the fall season, severe cyclogenesis associated with strong winds and large sea waves during winter, and heat waves and droughts accompanied by forest fires during summer. The Hymex project has focused on conducting both special observation periods (SOPs) and long-term observation periods (LOPs). An important goal of the project is also to advance state-of-the-art numerical models within a coupled atmosphere – sea – land modelling system across all weather and climate scales. Therefore, the project aims to improve the capability of predicting high-impact weather events, which remains moderate due to contribution of very fine-scale processes and their non-linear interactions with the larger-scale processes. On climate scales, in addition to temperature increase, a large decrease in the mean precipitation and an increase in precipitation variability are expected during dry (warm) season in future. Due to comparable amplitudes of climate change and internal climate variability, assessing regional climate evolution in the Mediterranean still remains a principal challenge.