An update on multiplexed mass spectrometry-based lysosomal storage disease diagnosis.

Lysosomal storage disorders (LSDs) are a type of inherited metabolic disorders in which biomolecules, accumulate as a specific substrate in lysosomes due to specific individual enzyme deficiencies. Despite the fact that LSDs are incurable, various approaches, including enzyme replacement therapy, hematopoietic stem cell transplantation, or gene therapy are now available. Therefore, a timely diagnosis is a critical initial step in patient treatment. The-state-of-the-art in LSD diagnostic uses, in the first stage, enzymatic activity determination by fluorimetry or by mass spectrometry (MS) with the aid of dry blood spots, based on different enzymatic substrate structures. Due to its sensitivity, high precision, and ability to screen for an unprecedented number of diseases in a single assay, multiplexed tandem MS-based enzyme activity assays for the screening of LSDs in newborns have recently received a lot of attention. Here, (i) we review the current approaches used for simultaneous enzymatic activity determination of LSDs in dried blood spots using multiplex-LC-MS/MS; (ii) we explore the need for designing novel enzymatic substrates that generate different enzymatic products with distinct molecular masses in multiplexed-MS studies; and (iii) we give examples of the relevance of affinity-MS technique as a basis for reversing undesirable immune-reactivity in enzyme replacement therapy.

A Diphenylalanine Based Pentapeptide with Fibrillating Self-Assembling Properties.

Peptides and their related compounds can self-assemble into diverse nanostructures of different shapes and sizes in response to various stimuli such as pH, temperature or ionic strength. Here we report the synthesis and characterization of a lysozyme derived pentapeptide and its ability to build well-defined fibrillar structures. Lysozyme FESNF peptide fragment was synthesized by solid phase peptide synthesis using the Fmoc/t-Bu strategy, purified by analytical high-performance liquid chromatography (HPLC) and its molecular weight was confirmed by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Spectroscopic features of this pentapeptide were investigated by UV-visible spectroscopy and fluorimetry showing the pattern of marginal phenylalanine residues within the peptide sequence. Self-assembling properties were determined using atomic force microscopy (AFM), aggregation index and thioflavin T assay (ThT). FESNF generating fibrillar structures observed by AFM and aggregation propensity were primarily influenced by pH conditions. Moreover, the experimental data were confirmed by molecular dynamics simulation studies. The obtained fibrils will be used next to explore their potential to act as support material for medical and cosmetic application.

Applications of MALDI-MS/MS-Based Proteomics in Biomedical Research.

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) is one of the most widely used techniques in proteomics to achieve structural identification and characterization of proteins and peptides, including their variety of proteoforms due to post-translational modifications (PTMs) or protein-protein interactions (PPIs). MALDI-MS and MALDI tandem mass spectrometry (MS/MS) have been developed as analytical techniques to study small and large molecules, offering picomole to femtomole sensitivity and enabling the direct analysis of biological samples, such as biofluids, solid tissues, tissue/cell homogenates, and cell culture lysates, with a minimized procedure of sample preparation. In the last decades, structural identification of peptides and proteins achieved by MALDI-MS/MS helped researchers and clinicians to decipher molecular function, biological process, cellular component, and related pathways of the gene products as well as their involvement in pathogenesis of diseases. In this review, we highlight the applications of MALDI ionization source and tandem approaches for MS for analyzing biomedical relevant peptides and proteins. Furthermore, one of the most relevant applications of MALDI-MS/MS is to provide "molecular pictures", which offer in situ information about molecular weight proteins without labeling of potential targets. Histology-directed MALDI-mass spectrometry imaging (MSI) uses MALDI-ToF/ToF or other MALDI tandem mass spectrometers for accurate sequence analysis of peptide biomarkers and biological active compounds directly in tissues, to assure complementary and essential spatial data compared with those obtained by LC-ESI-MS/MS technique.

The Effectiveness of Different Eradication Schemes for Pediatric Helicobacter pylori Infection-A Single-Center Comparative Study from Romania.

INTRODUCTION: In Romania, studies on the pediatric population regarding H. pylori infection or bacterial resistance to antibiotics are limited. Eradication treatment of this infection still raises important problems in medical practice. This study aims to compare the effectiveness of three eradication therapies used against H. pylori infection in the pediatric population. METHODS: The prospective study enrolled children aged 6-17 years who were first diagnosed with H. pylori infection. Patients received a randomized treatment either the therapy with clarithromycin (CLR), the therapy with metronidazole (MTZ) or sequential therapy. The effectiveness of the eradication treatment was evaluated after 4-8 weeks from the end of the therapy by testing fecal antigen. RESULTS: 149 patients were enrolled over 18 months. The eradication rates were 49.5% for the treatment scheme with proton pump inhibitor (PPI) + amoxicillin (AMO) + MTZ, 26.7% for PPI + AMO + CLR and 23.8% for sequential therapy. MTZ therapy was superior to CLR therapy, but sequential therapy was not. Side effects were recorded for PPI + AMO + CLR with 39.6%, followed by sequential therapy 37.7%, and only 22.6% for PPI + AMO + MTZ. CONCLUSIONS: Therapy with MTZ can achieve a higher eradication rate as a first-line treatment in the case of H. pylori infection. Taking into account that Romania is in an area with increased resistance to CLR, MTZ therapy could be a promising alternative.

Self-Medication Patterns during a Pandemic: A Qualitative Study on Romanian Mothers' Beliefs toward Self-Treatment of Their Children.

Self-medication represents a significant healthcare and health policy issue worldwide, both in developed and underdeveloped countries. Currently, the COVID-19 pandemic is considered a relevant context that could subtly trigger self-medication behavior because of limited access to health care services and the threat of infection with the SARS-CoV-2 virus. While the previous research conducted with quantitative methodologies reported a dramatically increased rate of self-medication around the world, qualitative inquiries on the subjective experience with self-medicine remain scarce in medical and related fields of study. For this purpose, a qualitative study with semi-structured interviews was undertaken to better understand how Romanian mothers (n = 18) applied self-treatment with their children by avoiding medical advice during the COVID-19 pandemic. The results showed that the COVID-19 pandemic did not affect the prevalence of self-medicine among the pediatric population as parents achieved a degree of awareness of self-treatment of their children due to the general context of the outbreak of the COVID-19 pandemic.

Cu and Zn Interactions with Peptides Revealed by High-Resolution Mass Spectrometry.

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by abnormal extracellular amyloid-beta (Aß) peptide depositions in the brain. Among amorphous aggregates, altered metal homeostasis is considered a common risk factor for neurodegeneration known to accelerate plaque formation. Recently, peptide-based drugs capable of inhibiting amyloid aggregation have achieved unprecedented scientific and pharmaceutical interest. In response to metal ions binding to Aß peptide, metal chelation was also proposed as a therapy in AD. The present study analyzes the interactions formed between NAP octapeptide, derived from activity-dependent neuroprotective protein (ADNP), amyloid Aß(9-16) fragment and divalent metal ions such as Cu and Zn. The binding affinity studies for Cu and Zn ions of synthetic NAP peptide and Aß(9-16) fragment were investigated by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), electrospray ion trap mass spectrometry (ESI-MS) and atomic force microscopy (AFM). Both mass spectrometric methods confirmed the formation of metal-peptide complexes while the AFM technique provided morphological and topographic information regarding the influence of metal ions upon peptide crystallization. Our findings showed that due to a rich histidine center, the Aß(9-16) fragment is capable of binding metal ions, thus becoming stiff and promoting aggregation of the entire amyloid peptide. Apart from this, the protective effect of the NAP peptide was found to rely on the ability of this octapeptide to generate both chelating properties with metals and interactions with Aß peptide, thus stopping its folding process.

A computational study of metal ions interaction with amyloid-ß 1-42 peptide structure in hyperpyrexia: Implications for Alzheimer disease.

Given the current context of the SARS-CoV-19 pandemic, among the interfering risky factors with the Aß peptide aggregation in the brains of Alzheimer's disease (AD) patients can be hyperpyrexia and increased intracranial pressure (ICP). According to our hypothesis on the relationship between hyperpyrexia and cognitive decline in AD, two models of Aß peptides were used in this study: the structure of AD amyloid beta-peptide and near-atomic resolution fibril structures of the Aß peptide. Therefore, the binding templates were constructed for Aß peptide regions able to bind 9 different metal ions. The fragment transformation method was used for the structural comparison between Aß chains. Molecular dynamics simulation (MDS) was applied using the Nose-Poincare-Anderson equation to generate a theoretically correct NPT (isothermal-isobaric ensemble). The smallest dissimilarities were observed in the case of Cu+ binding potential followed by Co2+, both with similar variation. Structural changes have also occurred as a result of the dynamic simulation. All these changes suggest an aggravating factor in both hyperpyretic and AD conditions. Our findings suggest that elevated temperature and increased intracranial pressure rise the effect of peptide aggregation, by converting α-helix motif to ß-sheet and random coil conformation, which are related to the formation of senile plaques in AD brains.

Structural Characterization of a New Collagen Biomimetic Octapeptide with Nanoscale Self-Assembly Potential: Experimental and Theoretical Approaches.

Bioinspired peptides are attractive biomolecules which can improve our understanding of self-assembly processes for rational design of new peptide-based materials. Herein, a new amidated peptide FRSAPFIE (FRS), based on a sequence present in human collagen, was synthesized, characterized by mass spectrometry and subjected to self-assembling investigations. The optimal conditions for self-assembly were disclosed by dynamic light scattering at 32 °C and a peptide concentration of 0.51 %. In addition, AFM studies revealed ellipsoidal FRS shapes with an area between 0.8 and 3.1 µm2 . The ability of self-assembly was also proved using FAD dye as extrinsic fluorescence reporter. According to the theoretical analysis, the FRS peptide tends to form a bundle-type association, with a type of fibrillary tangles particle. Altogether, our findings address new challenges regarding the FRS peptide which can be used in further self-assembly studies to design biocompatible drug-delivery platforms.

A Proteomic Approach to Identify Zein Proteins upon Eco-Friendly Ultrasound-Based Extraction.

Zein is a type of prolamin storage protein that has a variety of biomedical and industrial applications. Due to the considerable genetic variability and polyploidity of the starting material, as well as the extraction methods used, the characterization of the protein composition of zein requires a combination of different analytical processes. Therefore, we combined modern analytical methods such as mass spectrometry (MS), Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), atomic force microscopy (AFM), or Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) for a better characterization of the extracted zein. In this study, we present an enhanced eco-friendly extraction method, including grinding and sieving corn seeds, for prolamins proteins using an ultrasonic extraction methodology. The use of an ultrasonic homogenizer, 65% ethanol extraction buffer, and 710 µm maize granulation yielded the highest protein extraction from all experimental conditions we employed. An SDS PAGE analysis of the extracted zein protein mainly revealed two intense bands of approximatively 20 and 23 kDa, suggesting that the extracted zein was mostly α-zein monomer. Additionally, MS analysis revealed as a main component the α-zein PMS2 (Uniprot accession no. P24450) type protein in the maize flour extract. Moreover, AFM studies show that extracting zein with a 65% ethanol and a 710 µm granulation yields a homogeneous content that could allow these proteins to be employed in future medical applications. This research leads to a better understanding of zeins content critical for developing new applications of zein in food and pharmaceutical industries, such as biocompatible medical vehicles based on polyplexes complex nanoparticles of zein with antimicrobial or drug delivery properties.

Probiotics and prebiotics in atopic dermatitis: Pros and cons (Review).

Atopic dermatitis (AD) represents a chronic inflammatory skin condition in which the skin barrier is impaired; thus, the permeability is increased. Hence, there is a greater risk of allergic sensitization, as well as a higher pH and lower protection against resident microbes. Since this condition is currently increasing among children, it requires further study, as little is known regarding the pathogenesis that makes the skin prone to chronic relapsing inflammation. Trying to standardize the data regarding the use of prebiotics and probiotics in AD, we encountered tremendous variability in the literature data. Literature abounds in conflicting data: studies regarding prophylactic and therapeutic applications, different types of strains and dosages, applications in young children up to 5 years of age and above, usage of probiotics alone, prebiotics alone or synbiotics combined. There are also conflicting data regarding the outcome of these studies; some confirming a positive effect of prebiotics, probiotics or synbiotics and some showing no efficacy at all. The articles were divided into those assessing probiotics or prebiotics alone and a combination of the two, with studies showing a positive effect and studies proving no efficacy at all. We tried to critically analyze those articles showing weak and strong points. In summary, the most studied probiotics were the strains of Lactobacilli and Bifidobacteria. The Severity Scoring of Atopic Dermatitis (SCORAD) index was used to measure the efficacy of the treatment. Most studies compared their results with a placebo group and the efficacy when seen in moderate to severe forms of AD in patients with other allergic diseases present. However, the results are difficult to interpret, as in many studies the authors suggest that the disease may have a tendency to improve in time in some groups of patients.

Enzymatic diagnosis of neuronal lipofuscinoses in dried blood spots using substrates for concomitant tandem mass spectrometry and fluorimetry.

Neuronal ceroid lipofuscinoses (NCLs) are a group of neurodegenerative diseases predominantly in childhood that are characterized by psychomotor deterioration, epilepsy, and early death of patients. The NCLs analyzed in the present study are caused by defects of the specific enzymes, CLN1 (palmitoyl protein thioesterase 1; PPT1), CLN2 (tripeptidyl peptidase 1; TPP1), and CLN10 (cathepsin D). Specific and sensitive diagnostic assays of NCLs were the main goal of this study. They are of increasing importance, particularly since enzyme replacement therapy (ERT) for NCL2 has recently become available for clinical treatment, and ERTs for further NCLs are under development. Here, we report specific and sensitive determinations for CLN1, CLN2, and CLN10 on dried blood spots by tandem mass spectrometry using multiple reaction monitoring mass spectrometry (MRM-MS). Identical substrates suitable for (i) fluorimetric determination of single enzymes and (ii) for MRM-MS determination of multiple enzymes were synthesized by chemical coupling of alkyl-umbelliferone building blocks with the corresponding peptidyl-substrate groups recognized by the target enzyme. Enzymatic determinations were performed both by fluorimetry and MRM-MS in patients with NCL1, NCL2, and NCL10 and showed good agreement in single assays. Moreover, duplex and triplex determinations were successfully performed for NCL1, NCL2, and NCL10. Specific peptidyl-(4-alkyl-umbelliferone) substrates were also synthesized for mass spectrometric determinations of different cathepsins (cathepsins-D, -F, and -B), to provide a differentiation of proteolytic specificities.

A Case Report of Generalized Pustular Psoriasis Associated With IgA Nephropathy.

Psoriasis vulgaris is a complex immune-mediated disorder that manifests as a chronic skin disorder, characterized by well-circumscribed inflammatory, erythematous plaques. In this case report, we present a patient with generalized pustular psoriasis (GPP) who presented to the nephrology department with rapidly progressive decline in renal function. The diagnosis of GPP was made a month ago, secondary to a coagulase-negative staphylococcal superinfection. Intrinsically, this introduced a diagnostic challenge as the presumed diagnosis of immunoglobulin A (IgA) nephropathy had to be distinguished from IgA-dominant infection-related glomerulonephritis. We further discuss the current evidence and immunohistological profiles of IgA nephropathy in psoriasis and detail the evolution of renal function of our patient over 25 months after he presented to our department.

Immuno-Affinity Mass Spectrometry: A Novel Approaches with Biomedical Relevance.

Identifying antigen-antibody interactions have been shown as a critical step in understanding the proteins biological functions and their involvement in various pathological conditions. While many techniques have been developed to characterize antigen-antibody interactions, one strategy that has gained considerable momentum over the last decade for the identification and quantification of antigen-antibody interactions, is immune affinity-chromatography followed by mass spectrometry. Moreover, the combination of enzymatic digestion of antigens and mass spectrometric identification of specific binding peptide(s) to the corresponding anti-antigen antibody has become a versatile and clinical relevant method for mapping epitopes by mass spectrometry. In this chapter, the development and applications of novel immunoaffinity mass spectrometric methodologies for elucidating biomedical aspects will be presented. First, a simplified mass spectrometric approach that maps an epitope from a digested antigen solution without immobilizing the anti-antigen antibody on a solid support will be reported. iMALDI (from immunoaffinity and MALDI, matrix-assisted laser desorption/ionization), a technique that involves immunoaffinity capture of specific peptides and direct MALDI measurements was used for absolute quantification of serine/threonine-specific protein kinase (AKT) peptides from breast cancer and colon cancer cell lines and flash-frozen tumor lysates. The intact transition epitope mapping (ITEM) was shown as a rapid and accurate epitope mapping method by using Ion mobility mass spectrometry (IMS-MS) for analysing the antigen peptide-containing immune complex previously generated by in solution epitope extraction/excision procedures.

Stoichiometry of Heavy Metal Binding to Peptides Involved in Alzheimer's Disease: Mass Spectrometric Evidence.

Mass spectrometry is a powerful analytical technique becoming increasingly important in different biomedical research area. Mass spectrometric based methods were developed and applied to detect and identify multiple metal ion complexes of peptides and proteins with high sensitivity and high mass accuracy. Aggregation of amyloid-ß (Aß) peptides is one of the main pathological features of Alzheimer's disease (AD), and some metal ions seem to play a key role in AD pathogenesis. Consequently, mass spectrometry was used to investigate heavy metal binding to AD-related peptides. Therefore, the purpose of this chapter is to review the methodology and application of identifying coordination chemistry and binding properties of several metal ion-binding sites to synthetic ß-amyloid (Aß) and anti-amyloid model peptides. The selective metal-amyloid-ß peptide interaction studies using (a) Matrix-assisted laser desorption/ionization mass spectrometry (MALDI); (b) Electrospray ionization mass spectrometry (ESI-MS), and (c) Tandem mass spectrometry (MS/MSn) will be reported.

Mass spectrometric characterization of the zein protein composition in maize flour extracts upon protein separation by SDS-PAGE and 2D gel electrophoresis.

Highly homogenous α zein protein was isolated from maize kernels in an environment-friendly process using 95% ethanol as solvent. Due to the polyploidy and genetic polymorphism of the plant source, the application of high resolution separation methods in conjunction with precise analytical methods, such as MALDI-TOF-MS, is required to accurately estimate homogeneity of products that contain natural zein protein. The α zein protein product revealed two main bands in SDS-PAGE analysis, one at 25 kDa and other at 20 kDa apparent molecular mass. Yet, high resolution 2DE revealed approximately five protein spot groups in each row, the first at ca. 25 kDa and the second at ca. 20 kDa. Peptide mass fingerprinting data of the proteins in the two dominant SDS-PAGE bands matched to 30 amino acid sequence entries out of 102 non-redundant data base entries. MALDI-TOF-MS peptide mapping of the proteins from all spots indicated the presence of only α zein proteins. The most prominent ion signals in the MALDI mass spectra of the protein mixture of the 25 kDa SDS gel band after in-gel digestion were found at m/z 1272.6 and m/z 2009.1, and the most prominent ion signals of the protein mixture of the 20 kDa band after in-gel digestion were recorded at m/z 1083.5 and m/z 1691.8. These ion signals have been found typical for α zein proteins and may serve as marker ion signals which upon chymotryptic digestion reliably indicate the presence of α zein protein in two hybrid corn products.

Ultrasound-based protein determination in maize seeds.

The need for a simple and accurate method for protein estimation in alcoholic extracts led to the reexamination of the optimum conditions of a colorimetric assay based on the biuret reaction. Sonication time and the other experimental parameters were optimized after kinetics study on the extraction of either zein or total proteins. Zein extraction and purity were investigated by (1)H and (13)C NMR spectroscopy, SDS-PAGE electrophoresis, and UV-visible spectrophotometry (UV-vis). A zein assay was proposed, which involves the reaction of copper ions in copper phosphate powder with zein extracted in ethanolic solutions under strong alkaline environment. Furthermore, we extended this procedure to determine total proteins in maize samples simultaneously with their ultrasonic-assisted (US) extraction with an alkaline-alcoholic solution. Proteins in both types of extracts were well characterized by UV-vis spectroscopy. However, the 545 nm absorbance of the violet-colored supernatants which is proportional to the protein content was found to be the key parameter of the improved biuret-based protein assay. Comparison of values obtained by this procedure and by Micro-Kjeldahl method was in excellent agreement. A scaled-down procedure agreed well with the standard procedure. Enhanced accuracy and repeatability was found in protein determination in maize using the modified biuret method. The optimization of reagent concentrations and incubation times were studied as well.

Letter: Mass spectrometric approach of high pH- and copper-induced glutathione oxidation.

The interaction between copper ions and gamma-L-glutamyl-L-cysteinyl-glycine [glutathione (GSH)] molecules may lead to the formation of the physiologically occurring Cu[I)-[GSH]2 and Cu(II)-GSSG complexes. Since glutathione depletion in neurons and aberrant copper metabolism have been implicated in several neurodegenerative disorders, we studied here the interaction of GSH with copper ions (Cu2+) by electrospray ionization ion trap mass spectrometry (ESI-IT-MS). Besides, we extended this approach to pH in excess of 10 by adding ethanolamine to the solution being investigated. As a result, the ESI-IT-MS spectra revealed novel aspects regarding the speciation of copper-glutathione complex.

Two different hydrogen bond donor ligands together: a selectivity improvement in organometallic {Re(CO)3} anion hosts.

Rhenium(I) compounds [Re(CO)(3)(Hdmpz)(2)(ampy)]BAr'(4) and [Re(CO)(3)(N-MeIm)(2)(ampy)]BAr'(4) (Hdmpz = 3,5-dimethylpyrazole, N-MeIm = N-methylimidazole, ampy = 2-aminopyridine or 3-aminopyridine) have been prepared stepwise as the sole reaction products in good yields. The cationic complexes feature two different types of hydrogen bond donor ligands, and their anion binding behavior has been studied both in solution and in the solid state. Compounds with 2-ampy ligands are labile in the presence of nearly all of the anions tested. The X-ray structure of the complex [Re(CO)(3)(Hdmpz)(2)(ampy)](+) (2) shows that the 2-ampy ligand is metal-coordinated through the amino group, a fact that can be responsible for its labile character. The 3-ampy derivatives (coordinated through the pyridinic nitrogen atom) are stable toward the addition of several anions and are more selective anion hosts than their tris(pyrazole) or tris(imidazole) counterparts. This selectivity is higher for compound [Re(CO)(3)(N-MeIm)(2)(MeNA)]BAr'(4) (5·BAr'(4), MeNA = N-methylnicotinamide) that features an amido moiety, which is a better hydrogen bond donor than the amino group. Some of the receptor-anion adducts have been characterized in the solid state by X-ray diffraction, showing that both types of hydrogen bond donor ligands of the cationic receptor participate in the interaction with the anion hosts. DFT calculations suggest that coordination of the ampy ligands is more favorable through the amino group only for the cationic complex 2, as a consequence of the existence of a strong intramolecular hydrogen bond. In all other cases, the pyridinic coordination is clearly favored.

Second-sphere interaction of anions with a weakly binding metal complex host: probing the effect of counteranions.

The reaction of [Re(OTf)(CO)5] with N-methylimidazole (MeIm) afforded [Re(CO)3(MeIm)3]OTf (1). The reactions of 1 with KPF6, NaBPh4 and NaBAr'4 (Ar' = 3,5-bis(trifluoromethyl)phenyl) afforded [Re(CO)3(MeIm)3]PF6 (2) [Re(CO)3(MeIm)3]BPh4 (3) and [Re(CO)3(MeIm)3]BAr'4 (4) respectively. An analogous reaction using N-phenylimidazole (PhIm) yielded [Re(CO)3(PhIm)3]BAr'4 (7). These new compounds were characterized by IR and NMR, and the structures of 1 and 2 were determined by X-ray diffraction. Compounds [Re(CO)3(MeIm)3]2[PtCl6] (5), [Re(CO)3(MeIm)3][HSO4] (6), [Re(CO)3(PhIm)3][Br] (8) and [Re(CO)3(PhIm)3][NO3] (9) were crystallized from equimolar mixtures of either 4 or 7 and the tetrabutylammonium salt of the corresponding anion, and their structures were determined by X-ray diffraction. The solution behavior of 1-4, 7 toward several anions was studied spectroscopically, including the quantitative determination of binding constants by 1H NMR. The cationic tris(imidazole)complexes are stable against imidazole-by-anion substitution, and the main hydrogen bonding interactions involve the imidazole NC(H)N groups. The binding constants for compounds 1-4 with several external anions follow the order 1<2<3<4, indicating that the strength of the cationic complex-counteranion interaction follows the order OTf(-) > PF6(-) > BPh4(-) > BAr'4(-).

Biimidazole and bis(amide)bipyridine molybdenum carbonyl complexes as anions receptors.

Compounds [Mo(CO)4(N-N)] (N-N = 4,4'-bis((4-methylphenyl)carbamoyl)-2,2'-bipyridine, bipy', 1; or 2,2'-biimidazole, H2biim, 2), [MoCl(eta3-methallyl)(CO)2(N-N)] (N-N = bipy', 3; H2biim, 4), and [Mo(eta3-methallyl)(CNtBu)(CO2)(N-N)]BAr'4 (Ar' = 3,5-bis(trifluoromethyl)phenyl; N-N= bipy', 5; H2biim, 6) were synthesized and characterized, and their behavior toward anions was investigated in solution (IR and 1H NMR) and in solid state (X-ray diffraction).